Title of Invention: LENS DRIVE DEVICE, IMAGE PICKUP DEVICE AND LENS DRIVE METHOD Abstract: A lens drive device in at least one lens barrel holding a lens moveably includes a motor to drive the lens; an acceleration detection section to detect an acceleration; and an output control section to control an output of the motor corresponding to the acceleration detected by the acceleration detection section. The output control section determines whether the acceleration detected by the acceleration detection section falls within a predetermined acceleration range or not. When the acceleration is determined to be within the range, a further determination of whether the lens drive device is in a stationary state is performed. When it is determined not being in the stationary state, the motor is driven by a maximum drive voltage. When it is determined being in the stationary state, a further determination of whether the posture is horizontal or not is performed. Detailed Description: CROSS-REFERENCE TO THE RELATED APPLICATIONS The present application is based on and claims priority benefit from each of Japanese Patent Application Nos. 2007-296059, filed on Nov. 14, 2007, 2008-056035, filed on Mar. 6, 2008, and 2008-245652 filed on Sep. 25, 2008, the disclosures of which are incorporated herein by reference in their entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens drive device, an image pickup device and a lens drive method, configured to control a lens barrel drive force, by detecting a posture and an operation of the image pickup device by use of an acceleration sensor and based on the detected information. 2. Description of the Related Art In recent years, image pickup accuracy, rapidness, as well as low power consumption and drive stability have been further highly required of an image pickup device, such as a digital camera. In order to satisfy these requirements, a built-in accelerometer is fitted into the image pickup device to detect a posture or a motion direction thereof with respect to a direction of gravity of the image pickup device and to perform various controls of the image pickup device based on information obtained by the accelerometer. In order to photograph with high accuracy, one of the problems that remain to be solved is that an out of focus image is sometimes undesirably photographed depending on the posture of the image pickup device. Such a problem is caused by a still-position deviation of a lens existing in a lens drive unit, resulting from a looseness, such as a play or a backlash, thereby lacking sharpness in a photograph. To deal with such a problem, it is proposed that an acceleration sensor be provided to detect the posture of the image pickup device via an output of the acceleration sensor. Corresponding to the detected posture of the image pickup device, the lens stationary position deviation is corrected, thereby allowing photography with high accuracy (For reference, see Japanese Application Publication Number Hei6-300962 and Japanese Application Publication Number 2005-265448). Furthermore, in order to photograph rapidly, one of the problems that remain to be solved is that it is rather time-consuming to perform a focus adjustment; for example, when an automatic focusing is performed at the time of photographing, while moving the lens along the optical axis in order to determine a focus where an edge component of a photographed image reaches a peak. Since a range to perform focusing needs to be set wide, the focus adjustment becomes time-consuming. To deal with such a problem, it is proposed that a subject position be predicted based on a posture of the image pickup device to narrow the range to perform focus adjustment, whereby rapid photographing can be expected to be realized (For reference, see Japanese Application Publication Number 2006-323121). Meanwhile, concerning the image pickup device, a force (torque) necessary to drive a lens barrel varies with the posture of the image pickup device and a direction of the drive. For example, concerning the image pickup device having a collapsible lens barrel, when the lens barrel is placed in the gravity direction, namely downwards, the gravity promotes an extension of the lens barrel. In contrast, when the lens barrel is placed in the direction opposite to the gravity direction, namely upwards, the gravity facilitates a collapse or housing of the lens barrel. Considering the above, on the one hand, to extend the lens barrel, when a photographing lens is placed upwards, a maximum torque is required because the gravity impedes the extension of the lens barrel. When the photographing lens is placed horizontally, a second largest torque is required. When the photographing lens is placed downwards, a minimum torque is required because the gravity facilitates the extension of the lens barrel with the gravity direction being consistent with the extension direction. On the other hand, to house the lens barrel, when the photographing lens is placed downwards, a maximum torque is required because the gravity impedes the housing of the lens barrel. When the photographing lens is placed horizontally, a second largest torque is required. When the photographing lens is placed upwards, a minimum torque is required because the gravity facilitates the housing of the lens barrel with the gravity direction being consistent with the housing direction. As illustrated heretofore, although the torque necessary to extend and house the lens barrel varies with the posture of the image pickup device, a conventional image pickup device always extends and houses the lens barrel with a constant drive torque. More specifically, despite the fact that the maximum torque (a maximum extension torque will be used hereinafter) is required to extend the lens barrel when the photographing lens is placed upwards, the conventional image pickup device always extends the lens barrel unalterably with the maximum torque even when the photographing lens is placed in other postures. Likewise, despite the fact that the maximum torque (a maximum housing torque will be used hereinafter) is required to house the lens barrel when the photographing lens is placed downwards, the conventional image pickup device always houses the lens barrel unalterably with the maximum torque even when the photographing lens is placed in other postures. The maximum extension torque and the maximum housing torque will be referred to as a maximum drive torque hereinafter. As illustrated heretofore, since the conventional image pickup device always drives the lens barrel unalterably with the maximum drive torque even when a smaller drive torque will do, a superfluous amount of electricity is consumed. Consequently, it is difficult for the image pickup device to meet the demand of energy-saving. Moreover, concerning the conventional image pickup device, although a torque corresponding to the maximum drive torque required to extend and to house the lens barrel is set, the lens barrel has not been driven by a torque larger than the maximum drive torque. However, for example, in the cases wherein the image pickup device is operated in the middle of an intense movement or is forcibly taken out of a bag or a pocket, because an acceleration produced at the time operates, the lens barrel may not be able to be driven unless by the torque which is larger than the aforementioned maximum drive torque. In these cases, since neither the drive of the lens barrel is able to start nor the drive is able to be maintained, there is a problem with the conventional image pickup device in that a stable drive of the lens barrel cannot be realized. In addition, there is also a collapsible lens barrel in which when in a non-photographing state, at least one group of lenses retreats sideways from a lens optical axis at the time of photographing and other lens groups are housed in an image pickup device body. Concerning such a collapsible lens barrel, when a power switch is turned on to photograph, if an acceleration larger than the prescribed value is applied to the image pickup device in the middle of moving the respective lens groups to photographing positions, occasionally the respective lens groups are not able to be moved to the photographing positions. The reason is that when the acceleration is applied to the lens groups, especially to the aforementioned lens group, which retreats sideways from the lens optical axis at the time of photographing, the torque becomes insufficient to move this lens group. SUMMARY OF THE INVENTION An object of the present invention is to provide a lens drive device, an image pickup device and a method of lens drive, which is capable of suppressing the power consumption and securing a stable drive of a lens barrel. More specifically, the power consumption can be suppressed via detecting a posture of the image pickup device by a built-in acceleration sensor fitted into the image pickup device and then based on the detected information, adjusting a torque necessary to drive the lens barrel holding lenses. The stable drive of the lens barrel can be secured via terminating the drive of the lens barrel upon the detected acceleration exceeding a prescribed range. In the middle of the lens being moved along the optical axis by the lens drive device, for example, to perform an operation such as zooming, the lens movement direction may be reversed. When the lens is driven while the posture of the lens drive device remains unchanged, the force required to drive the lens varies before and after the switch of the lens movement direction. Therefore, based on the detected information obtained from the acceleration sensor, the output of the lens drive device is appropriately controlled, whereby the superfluous power consumption can be suppressed, and the stable drive can be secured. It is also an object of the invention to provide such a lens drive device. In order to achieve the above object, according to one embodiment of the present invention, a lens drive device is provided in a lens barrel holding a lens moveably, including: a motor to drive the lens; an acceleration detection section to detect an acceleration; and an output control section to control an output of the motor corresponding to the acceleration detected by the acceleration detection section; wherein the output control section determines whether the acceleration detected by the acceleration detection section falls within a predetermined acceleration range or not, when the acceleration is determined to be within the range, a further determination of whether being in a stationary state is performed, and when it is determined as not being in the stationary state, the motor is driven by a maximum drive voltage, while when it is determined as being in the stationary state, a further determination of whether the posture is horizontal or not is performed, when being horizontal is determined, the motor is driven by a drive voltage appropriate for being horizontal, while when it is determined as not being horizontal, a further determination is performed of whether to drive the motor in the gravity direction or in the direction opposite to the gravity direction, when it is determined to drive the motor in the gravity direction, the motor is driven by a lower voltage than the drive voltage appropriate for being horizontal, while when otherwise, the motor is driven by a voltage higher than the drive voltage appropriate for being horizontal and lower than the maximum drive voltage. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front perspective view of a digital camera according to a first embodiment of the present invention. FIG. 2 is a rear perspective view of the digital camera according to the first embodiment of the present invention. FIG. 3 is a rear view of the digital camera with a rear cover unit and an upper cover unit detached according to the first embodiment of the present invention. FIG. 4 is a rear perspective view of a lens barrel unit according to the first embodiment of the present invention. FIG. 5 is a front perspective view of an imaging element circuit board according to the first embodiment of the present invention. FIG. 6 is a rear perspective view of the imaging element circuit board according to the first embodiment of the present invention. FIG. 7 is a rear view of the digital camera of a transfiguration with the rear cover unit and the upper cover unit detached according to the first embodiment of the present invention. FIG. 8 is a rear perspective view of an inclination detection wiring substrate of a transfiguration according to the first embodiment of the present invention. FIG. 9 is a block diagram showing a schematic construction of a built-in control system of the digital camera according to the first embodiment of the present invention. FIG. 10 is a diagrammatic sketch showing a screen display when a posture of the digital camera is determined, according to the first embodiment of the present invention. FIG. 11 is a sectional view showing a direction of the gravity working on the lens when the digital camera is in an upwards posture according to the first embodiment of the present invention. FIG. 12 is a sectional view showing a direction of the gravity working on the lens when the digital camera is in a downwards posture according to the first embodiment of the present invention. FIG. 13 is a graph illustrating a variation of the voltage with the lapse of time when the lens barrel is extended with the current and a pulse rate being constant corresponding to various postures of the digital camera according to the first embodiment of the present invention. FIG. 14 is a graph illustrating a variation of the current with the lapse of time when the lens barrel is extended with the voltage and the pulse rate being constant corresponding to the various postures of the digital camera according to the first embodiment of the present invention. FIG. 15 is a graph illustrating a variation of the voltage with the lapse of time when the lens barrel is housed with the current and the pulse rate being constant corresponding to the various postures of the digital camera according to the first embodiment of the present invention. FIG. 16 is a graph illustrating a variation of the current with the lapse of time when the lens barrel is housed with the voltage and the pulse rate being constant corresponding to the various postures of the camera according to the first embodiment of the present invention. FIG. 17 is a flow chart illustrating a torque control performed to extend the lens barrel based on the voltage when the power is on according to the first embodiment of the present invention. FIG. 18 is a flow chart illustrating a torque control performed to house the lens barrel based on the voltage when the power is off according to a second embodiment of the present invention. FIG. 19 is a flow chart illustrating a torque control performed for an automatic focusing, based on the voltage when the power is on according to a third embodiment of the present invention. FIG. 20 corresponds to a fourth embodiment of the present invention, in which FIG. 20A is a table indicating a posture determination condition and a relationship between a drive voltage of the lens drive device and a voltage table applied corresponding to a respective determined postures. FIG. 20B is a timing diagram illustrating a fluctuation in the drive voltage of the lens drive device when the lens is moved from the wide-angle end to the telephoto end. FIG. 20C is a timing diagram illustrating a fluctuation in the drive voltage of the lens drive device when the lens is moved from the telephoto end to the wide-angle end. FIG. 21 is a flow chart illustrating an operation of the fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIGS. 1 to 17 illustrate a first embodiment in which a lens drive device according to the present invention is applied to a digital camera. As shown in FIG. 1 and FIG. 2, on an upper surface of a camera main body 1, there are provided a shutter button 2 (a release button) which is pressed to photograph; a power switch button 3; a mode dial 4, used to switch an operation mode; a shift dial 5; a flash section 6 accommodated in the camera which pops up when necessary; and an accessory shoe 7 whereto an external flash and an external optical finder provided. In the front of the camera main body 1, there is provided a photographing lens 8 (photographing lens 8 collectively refers to plural lenses included in a lens barrel unit 62, which will be illustrated hereinafter). In the rear of the camera main body 1, there are provided a zoom button 9; menu cursor instruction buttons and selection instruction buttons 10; a replay button 11; a deletion/self-timer button 12; a monitor screen 15, which is an electronic view panel such as a LCD panel, to display a subject or mode information; a switch button 14 to switch the display of the monitor screen 15; and a light emitting diode 16 (an LED display section), which is lighted indicating either being within a charge period of the flash or being in an in-focus state. At the flank of the camera main body 1, there is provided a terminal lid 17, which covers an AV terminal entrance and an USB terminal entrance (external connection terminal entrance). At the bottom of the camera main body 1, there is provided a battery lid 18, which covers a battery insertion entrance and an insertion entrance of a memory card to record an image. Then, the constitution inside of the digital camera 1 will be illustrated hereinafter. FIG. 3 is a rear view showing the digital camera after a rear cover unit and an upper cover unit are removed according to an embodiment of the present invention. FIG. 4 is a rear perspective view of a barrel unit according to an embodiment of the present invention. FIG. 5 and FIG. 6 are a front perspective view and a rear perspective view respectively of an image pickup element circuit substrate according to an embodiment of the present invention. The imaging element circuit board 64 is provided near a rear surface of the camera main body. On a front surface 70 of the imaging element circuit board 64, there is installed a CCD26 (See FIG. 5 for reference), serving as the image pickup element which converts the light incident via the aforementioned photographing lens 8 into an electrical signal. At the periphery of the COD 26, an electric component 66 including a front end IC, a digital still camera processor and the like, used to process signals, is installed. In addition, on a rear surface 71 of the imaging element circuit board 64, there is also installed an inclination detection sensor 67 (an acceleration sensor will also be used hereinafter), which detects an inclination based on variances in the acceleration. The acceleration sensor 67 according to an embodiment of the present invention is a heat detection acceleration sensor installed on a PCB (a printed circuit board). The acceleration sensor 67 detects the acceleration of the three-dimensional space while dividing the acceleration into X-axis, Y-axis and Z-axis components. Here the X-axis, Y-axis and Z-axis are perpendicular to one another. In addition, being a heat detection acceleration sensor, if this acceleration sensor 67 is disposed in the vicinity of a heat-generating device such as the image pickup element 26 or a CPU block 104-3, detection accuracy may undesirably deteriorate. Therefore, as illustrated hereinafter, the acceleration sensor 67 is disposed away from the heat-generating electrical components, whereby the deterioration in the detection accuracy due to the heat generated from the electrical components is prevented. One end 68 of the imaging element circuit board 64 is connected with a main circuit board 63 via a connector 69, whereby the electrical signal is transmitted to the main circuit board 63. After a tilt adjustment, the imaging element circuit board 64 is assembled via being adhered to and fixed to a rear surface 76 of the lens barrel unit 62. The inclination detection sensor 67 is provided at the rear surface 76, whereby some effects can be obtained as follows. The tilt, namely an assembly error of the inclination detection sensor 67, caused by a manufacture process of the digital camera, with respect to the image pickup element 26, can be absorbed via performing a calibration (adjustment) electrically. However, when a user drops or bangs the camera main body 1, because of the produced shock applied to the camera, the components of the assembly may move. Consequently, the posture or the inclination of the inclination sensor 67 with respect to the image pickup element 26 may vary, which may cause an incorrect display on the monitor screen 15 (see FIG. 10 for reference) which is used to display the inclination of the camera. However, as illustrated above, since the inclination detection sensor 67, which detects the inclination of the image pickup device, is directly mounted on the imaging circuit board 64 whereon the image pickup element 26 is provided, one advantage is that the variance in the relative inclination is not generated by such a configuration. Furthermore, since the inclination detection sensor 67 is installed on the opposite side of the surface 70 whereon the image pickup element 26 is mounted, a space 66 for some electrical components to process signals, which are installed at the periphery of the surface 70 on the image pickup element 26 of the imaging element circuit board 64, can be secured. In addition, a space for electromechanical components of the lens barrel unit 62 can also be secured. In addition, considering that the image pickup element 26 is a heat-generating member, the inclination detection sensor 67, which is a heat detection acceleration sensor, is provided at a position away from the image pickup element 26 and being on the different plane from that of the image pickup element 26. Thus, deterioration in the detection accuracy of the acceleration can be suppressed. Although in one embodiment of the present invention, the inclination detection sensor 67 is installed on the rear surface 71 of the imaging element circuit board 64, the invention is not limited thereto. Hereinafter a transfiguration example will be illustrated. FIG. 7 is a rear view of the digital camera with a back cover unit and an upper cover unit detached according to a transfiguration of the present invention. FIG. 8 is a rear perspective view of an inclination detection wiring board according to a transfiguration of the present invention. Behind the rear surface 76 of the lens barrel unit 62, an inclination detection wiring substrate 65, equipped with the inclination detection sensor 67 that detects the inclination of the image pickup device, is positioned by two bosses 78 and 79 of the lens barrel unit 62, and fixed by a screw 80. The inclination detection sensor 67 is mounted on the rear surface 71 of the inclination detection wiring substrate 65. An end 72 of the inclination detection wiring substrate 65 is connected with the main circuit board 63 via a connector 73, whereby the electrical signal obtained from the inclination detection sensor 67 is transmitted to the main circuit board 63. The inclination detection sensor 67 is mounted at such a position that some effects can be obtained as follows. More specifically, since after the tilt adjustment, the imaging element circuit board 64, equipped with the image pickup element 26, is assembled via being adhered to and fixed to the rear surface of the lens barrel unit 62, one of the advantages is that the inclination of the image pickup element 26 with respect to the lens barrel unit 62 does not vary. Moreover, since the inclination detection sensor 67, which detects the inclination of the image pickup device, and the aforementioned inclination detection wiring substrate 65 are fixed by the positioning screw 80, one of the advantages is that the inclination of the inclination detection sensor 67 with respect to the image pickup element 26 does not vary. In addition, since the inclination detection sensor 67, which is a heat detection acceleration sensor, is provided at a position away from the heat-generating member, the deterioration in the detection accuracy of the acceleration can be suppressed. The inclination detection sensor 67 can also be installed in other positions apart from the position mentioned above. For example, the inclination detection sensor 67 can also be installed in a position away from a heat-generating electrical component, such as a CPU block 104-3, on the main circuit board 63 whereon some electrical components are equipped, such as a digital still camera processor 104 having the CPU block 104-3. Thus, the deterioration in the detection accuracy of the acceleration can be suppressed. Although according to an embodiment of the present invention, the inclination detection sensor 67 is of the type of the heat detection acceleration sensor, other types can also be used which can be equipped on the PCB, such as a piezoresistor-type acceleration sensor or a capacitance-type acceleration sensor. In addition, although according to an embodiment of the present invention, the inclination detection sensor 67 is of the type which can be mounted on the PCB, other types can also be used which are capable of measuring accelerations in three-dimensional directions. Next, an inner control system of the digital camera will be illustrated hereinafter. FIG. 9 is a block diagram schematically showing a configuration of the inner control system of the digital camera according to an embodiment of the present invention. As shown in the FIG. 9, the digital camera comprises the lens barrel unit 62 including various lenses and motors, a CCD101 which is built in the camera main body 1, a front end IC 102 to apply various adjustments to the image data, a digital still camera processor 104 (hereinafter also referred to as processor) which plays a central role for the overall control and data processing of the camera main body 1, an SDRAM 103 which temporarily stores an image data whereto various processing is performed, an embedded memory 107 and a ROM 108. The lens barrel unit 62 includes a photographic lens optical system, a lens barrel and a motor which is composed of a plurality of pulse motors to drive each part of the lens barrel unit. The focusing at the time of photographing and an adjustment of a diaphragm at the time of exposure are performed via the lens barrel unit 62. More specifically, the lens barrel unit 62 is composed of a zoom optical system 62-1 including a zoom lens 62-1a to pick up an image of the subject and a zoom drive motor 62-1b; a focus optical system 62-2 including a focus lens 62-2a and a focus drive motor 62-2b; a diaphragm unit 62-3 including a diaphragm 62-3a and a diaphragm motor 62-3b; a mechanical shutter unit 62-4 including a mechanical shutter 62-4a and a mechanical shutter motor 62-4b; and a motor driver 62-5 to drive the respective motors. A subject image obtained from the lens barrel unit 62 at the time of photographing is formed on the imaging surface of the CCD101 built-in the camera body 1. The CCD101 converts the subject image data into an electrical signal (analog data) and outputs the electrical signal to a front end IC (F/E-IC is used in FIG. 9). The front end IC 102 comprises a CDS 102-1 which performs correlated double sampling to eliminate image noise, an AGC 102-2 for gain adjustment, an A/D converter 102-3 which performs analog-digital conversion, and a TG 102-4 (a drive timing signal generating section) which receives vertically synchronized signals (hereinafter referred to as “VD”) and horizontally synchronized signals (hereinafter referred to as “HD”) from CCD1 signal processing block 104-1 in the digital still camera processor 104. Here, the TG 102-4 is controlled by a CPU block 104-3. The front end IC 102 is used to apply various adjustments to the data received from the CCD 101. The electrical signal whereto various adjustments are applied by the front end IC 102 is then conveyed to the digital still camera processor 104. As mentioned above, the digital still camera processor 104 plays a central role for the overall control of the camera main body 1 and data processing for an image file conveyed as an electrical signal. The digital still camera processor 104 performs a white balance setting and a Gamma setting for output data obtained from the CCD 101 and conveyed to the front end IC 102. The digital still camera processor 104 comprises the CCD1 signal processing block 104-1 which supplies VD signals and HD signals, the CCD2 signal processing block 104-2 to perform conversion to brightness data and color difference data via filtering, the CPU block 104-3 to control the operations of the various constituent sections such as the motors built in the camera main body 1, and the local SRAM which temporarily stores data, etc. necessary for control of the operations of respective sections. In addition, the digital still camera processor 104 further comprises an USB block 104-5 which enables the communication with an external device such as a personal computer via a USB terminal, a serial block 104-6 which enables serial communication with an external device such as a personal computer, a JPEG CODEC block 104-7 which performs a compression and expansion of a JPEG file, a resize block 104-8 which enlarges and shrinks a size of image data by interpolation, a TV signal display block 104-9 which converts the image data into a video signal so as to display the image data on a monitor screen 15, such as an LCD panel via an LCD driver 109, a memory card controller block 104-10 which performs control of a memory card (not shown) recording photographed image data, and an I2C block which performs serial communication between the acceleration sensor 67 and the CPU block 104-3. The memory card is inserted in a memory card slot (not shown). The data is always transmitted and received among these circuit elements and constituent sections mentioned above. Outside of the processor 104, there are provided the SDRAM 103, the embedded memory 107, and the ROM 108 which stores various control programs, all of which are connected to the processor 104 via a bus line. The SDRAM 103 temporarily stores the data when various processings are applied to the image data by the processor 104. The stored image data, for example, are RAW-RGD image data obtained from the CCD 101 via the front end IC 102 and subjected to the white balance setting and the Gamma setting performed by the CCD1 signal processing block 104-1, YUV image data subjected to brightness data and color difference data conversion by the CCD2 signal processing block 104-2, JPEG image data subjected to JPEG compression by the JPEG CODEC block 104-7, and the like. The embedded memory 107 is a memory to store photographed image data even if no memory card is loaded in a memory card throttle. The ROM 108 stores the control programs which are described in codes that may be read by a CPU block 104-3 within the digital still camera processor 104, as well as parameters for control. When the power switch of the camera is turned on, the control programs are loaded into a main memory (not shown). The CPU block controls operations of respective sections according to the control programs and also temporarily stores data, etc. necessary for control in the local SRAM 104-4 within the digital still camera processor 104. A rewritable flash ROM is used as the ROM 108, whereby the control program and parameters for control can be altered to facilitate version upgrade of the function. The ultimate data obtained after various processings are performed is stored either in the embedded memory 107 or in the memory card serving as an external record medium, which is detachably inserted in the memory card slot. The acceleration sensor 67 to detect the acceleration is connected to the digital still camera processor 104. The detailed illustration of the acceleration sensor 67 is made as above. The acceleration data detected by the acceleration sensor 67 is transmitted to the I2C block 104-11, and converted into a serial signal that the CPU block 104-3 can recognize. The serial signal including the acceleration data generated in the I2C block 104-11 is transmitted to the CPU block 104-3, whereby serial communication is performed between the acceleration sensor 67 and the CPU block 104-11. The CPU block 104-3 performs arithmetic processing by using a threshold value and the calculation formula stored in the ROM108 illustrated later based on the aforementioned acceleration data, whereby there is generated an instruction signal to control an operation of a motor driver 62-5 illustrated later. This instruction signal is transmitted to the motor driver 62-5, whereby the operation control of the motor driver 62-5 is performed. The motor driver 62-5 is used to control the various motors in the lens unit 62. The various motors are pulse motors controlled by a momentum or a current pulse. The output of the pulse motor (the torque) is increased accompanied by an increase in a current and a voltage applied to the motor and decreases accompanied by an increase of a pulse rate. Therefore, the torque of these motors can be controlled by adjusting the current, the voltage, and the pulse rate. Next, it will be illustrated hereinafter how the digital camera detects the posture according to the first embodiment of the present invention. FIG. 10 is a schematic diagram showing that the digital camera according to the first embodiment of the present invention detects the posture thereof. The digital camera 1 according to the first embodiment of the present invention has a function which enables the user to confirm whether the camera is placed horizontally with respect to a photographing direction. This function will be illustrated as follows. As shown in FIG. 10, the inclination of the digital camera 1 with respect to the horizontal direction is displayed by a plurality of circular marks on the monitor screen 15, based on the information obtained from the inclination detection sensor 67. There are provided a plurality of circles overlapping the subject image, which are displayed on the monitor screen 15. Specifically, the inclination of the digital camera 1 with respect to the horizontal direction is indicated either by the color change of the plurality of circles or by the color change accompanied by a sound generated. As shown in FIG. 10, the plurality of circles are aligned horizontally at the lower part of the monitor screen 15. When the composition image inclines, the inclination direction thereof and the amount of the inclination are indicated by the color change of twelve small circles provided at both sides of one central bigger circle 51. For instance, when the composition image is inclined greatly to the right due to the inclination of the camera, the color of a circle at the right end 53 changes from white into green. When the amount of the inclination decreases, the color of a circle 54, adjacent to the circle 53 at the left side, changes from white into green while the color of the circle 53 reverts to white. When the user operates to reduce the amount of the inclination of the camera while observing the indicated state of the camera, the circle whose color turns into green approaches the center likewise. When the digital camera 1 is positioned horizontally by the user, the user can be informed of the state of the camera either by the color of the central big circle 53 turning into green or by such a color change of the circle 53 accompanied by a sound generated. It is optional for the user to decide whether to indicate such an inclination direction and an inclination amount on the monitor screen 15 or not. Next, the control of the drive torque of the lens barrel and the various motors will be elaborated hereinafter. FIG. 11 is a sectional view showing a direction of the gravity working on the lens when the digital camera 1 is positioned upwards. FIG. 12 is a sectional view showing a direction of the gravity working on the lens when the digital camera 1 is positioned downwards. As illustrated in FIG. 11 by the indication of an arrow, when the camera body 1 is placed upwards, the gravity working on the photographing lens 8, included in the lens barrel unit 62, facilitates the housing of the lens barrel unit 62. Therefore, compared with the case wherein the camera body 1 is placed horizontally, the torque required by the drive motors of the lens barrel unit 62 so as to extend the lens barrel unit 62 is larger. Conversely, compared with the case wherein the camera body 1 is placed horizontally, the torque required by the motors so as to house the lens barrel unit 62 is smaller. As illustrated in FIG. 12 by the indication of an arrow, when the camera body 1 is placed downwards, the gravity working on the photographing lens 8, included in the lens barrel unit 62, facilitates the extension of the lens barrel unit 62. Therefore, compared with the case wherein the camera body 1 is placed horizontally, the torque required by the drive motors of the lens barrel unit 62 so as to extend the lens barrel unit 62 is smaller. Conversely, compared with the case wherein the camera body 1 is placed horizontally, the torque required by the motors so as to house the lens barrel unit 62 is larger. To summarize the above, in terms of the extension of the lens barrel unit 62 when only the gravitational acceleration is at work, a maximum torque is required when the camera is placed upwards; a second largest torque is required when the camera is placed horizontally; and a minimum torque is required when the camera is placed downwards. In contrast, in terms of the housing of the lens barrel unit 62 when only the gravitational acceleration is at work, a maximum torque is required when the camera is placed downwards; a second largest torque is required when the camera is placed horizontally; and a minimum torque is required when the camera is placed upwards. Meanwhile, sometimes, the user may start the operation of the camera while taking the camera body 1 out of a bag forcibly. Furthermore, the user also may photograph when he is doing an intense exercise or riding in a vehicle which shakes violently. In these cases, the acceleration applied to the camera body 1 becomes larger than the gravitational acceleration. Consequently, the acceleration produced at the time may impede the operation of the lens barrel unit 62 more than the gravitational acceleration does. Therefore, a torque which is even larger than the aforementioned maximum torque is required. As for the lens drive device having a photographing device such as the camera, besides the lens which moves in parallel with the optical axis, there also exists at least one lens group which moves in a direction which is not parallel with the optical axis, for example, which moves perpendicularly to the optical axis. In the lens drive device, the at least one lens group is referred to as a retractable lens. When in a non-photographing state, namely the lens barrel is housed or collapsed, the retractable lens is retracted sideways from the lens optical axis. When the lens barrel is extended, the retractable lens is placed onto the optical axis. A swing level, etc is fitted to the retractable lens. The retractable lens is susceptible to the acceleration because the retractable lens is advanced and retreated by rotating the swing level. Therefore, for the camera including the retractable lens, if an acceleration larger than the gravitational acceleration is applied to the camera in the middle of the movement of the retractable lens, the retractable lens contacts undesirably with other components inside the camera body 1. Consequently, the retractable lens may not be able to be moved normally. In such a case, the digital camera can not shift to the normal photographing state or a standstill state. As illustrated heretofore, although the torque necessary to extend and house the lens barrel varies with the posture of the camera, a conventional camera always drives the lens barrel with a constant drive torque. More specifically, despite the fact that the maximum torque is only required to extend the lens barrel when the photographing lens is placed upwards and the acceleration which is at work is 1 G (no acceleration other than the gravitational acceleration is further applied), the conventional camera always extends the lens barrel unalterably with the maximum torque even when the photographing lens is placed in other postures. Likewise, despite the fact that the maximum torque is required to house the lens barrel when the photographing lens is placed downwards, the conventional camera always houses the lens barrel unalterably with the maximum torque even when the photographing lens is placed in other postures. As illustrated heretofore, since the conventional camera always drives the lens barrel unalterably with the maximum drive torque even when a smaller drive torque will do, a superfluous amount of electricity is consumed. In addition, when the applied acceleration is larger than 1 G, the drive of the lens barrel may not be performed stably. In order to solve the problems of the conventional camera, the camera according to an embodiment of the present invention is provided to adjust the torque necessary to drive the lens barrel according to the determined posture of the camera based on the acceleration applied to the camera. Here, according to an embodiment of the present invention, the drive torque of a pulse motor, which is the motor to drive the lens barrel unit 62, is adjusted via adjusting a current, a voltage and a pulse rate applied to the motor. In other words, the current, the voltage and the pulse rate are parameters to adjust the torque of the pulse motor. The drive torque of the motor increases as the current or the voltage increases. Conversely, the drive torque of the motor decreases as the pulse rate increases. FIGS. 13 to 16 can be referred to for more details. FIG. 13 is a graph illustrating the variation of the voltage with the lapse of time when the lens barrel is extended with the current and the pulse rate being constant corresponding to various postures of the camera according to an embodiment of the present invention. FIG. 14 is a graph illustrating the variation of the current with the lapse of time when the lens barrel is extended with the voltage and the pulse rate being constant corresponding to various postures of the camera according to an embodiment of the present invention. FIG. 15 is a graph illustrating the variation of the voltage with the lapse of time when the lens barrel is collapsed with the current and the pulse rate being constant corresponding to various postures of the camera according to an embodiment of the present invention. FIG. 16 is a graph illustrating the variation of the current with the lapse of time when the lens barrel is collapsed with the voltage and the pulse rate being constant corresponding to various postures of the camera according to an embodiment of the present invention. All of FIGS. 13 to 16 illustrate the variation of the voltage or the current when the pulse is applied to the pulse motor. As illustrated in FIG. 13, when the current and the pulse rate applied to the motor are constant, the torque for the extension of the lens barrel unit 62 is adjusted via adjusting the voltage applied to the motor. In the case of extending the lens barrel unit 62, when only the gravitational acceleration (1 G) is at work, among the three postures of the camera (namely when the camera is placed upwards, horizontally and downwards, as illustrated in FIG. 13), the maximum torque is required when the camera is placed upwards. In this case, namely, the maximum voltage is required when the camera is placed upwards. Therefore, when the camera is upwards, in order to extend the lens barrel unit 62, compared with the voltage applied for the case wherein the camera is horizontal (hereinafter referred to as extension voltage for the horizontal posture), a higher voltage (hereinafter referred to as extension voltage for the upwards posture) is applied to the motor. Similarly, when only the gravitational acceleration (1 G) is at work and the camera is downwards, the lens barrel unit 62 can be extended by the minimum torque, or the minimum voltage (hereinafter referred to as the extension voltage for the downwards posture). Therefore, compared with the voltage for the horizontal posture, a lower voltage is applied to the motor. Meanwhile, in order to extend the lens barrel unit 62 when an acceleration is applied except the gravitational acceleration, for example, when the acceleration in the collapse direction of the lens barrel unit 62 exceeds 1 G (hereinafter the acceleration exceeding 1 G will be referred to as 1 G over), a higher voltage than that in the case where the camera is upwards is required. In other words, in the case of 1 G over, compared with the case of the upwards posture, an even higher voltage (hereinafter referred to as 1 G over extension voltage) is applied. In addition, when the current and the pulse rate are constant as the case with the three postures mentioned above, for various postures, the voltages are set to be higher than the lowest voltage (in FIG. 13, referred to as a lowest drive voltage) to extend the lens barrel unit 62 with the case of the upwards posture respectively. As illustrated in FIG. 14, when the voltage and the pulse rate applied to the motor are constant, the torque for the extension of the lens barrel unit 62 is adjusted via adjusting the current applied to the motor. Specifically, for the case of 1 G, when the camera is upwards, the maximum torque is required for the extension. Therefore, in order to extend the lens barrel unit 62, compared with the current applied for the case wherein the camera is horizontal (hereinafter referred to as extension current for the horizontal posture), a larger current (hereinafter referred to as extension current for the upwards posture) is applied to the motor. Conversely, when the camera is downwards, since the minimum torque is sufficient for the extension, among the cases with the three postures, the smallest current (hereinafter referred to as the extension current for the downwards posture) is applied. Similarly, in order to extend the lens barrel unit 62 with the downwards posture when an acceleration is applied except the gravitational acceleration, for example, when the acceleration in the collapse direction of the lens barrel unit 62 is 1 G over, an even larger torque than the one with the aforementioned case wherein the camera is upwards is required. In other words, in the case of 1 G over, compared with the case of the upwards posture, an even larger current (hereinafter referred to as 1 G over extension current) is applied. In addition, when the voltage and the pulse rate are constant as the case with the three postures mentioned above, for various postures, the currents are set to be larger than the smallest voltage (in FIG. 14, referred to as the smallest drive current) to extend the lens barrel unit 62 with the case of the upwards posture respectively. Meanwhile, in the case of 1 G, in order to house the lens barrel unit 62, when the camera is downwards, the maximum housing torque, or the highest voltage is required. Therefore, as illustrated in FIG. 15, in order to collapse the lens barrel unit 62 with the downwards posture, compared with the voltage applied in the case of the horizontal posture (hereinafter referred to as a collapse voltage for the horizontal posture), a higher voltage (hereinafter referred to as a housing voltage for the downwards posture) is applied to the motor. Conversely, in order to house the lens barrel unit 62 when the camera is upwards, the lens barrel unit 62 can be driven by the minimum torque or the minimum voltage. Therefore, a lower voltage is applied to the motor, compared with the voltage applied in the case of the horizontal posture. In order to collapse the lens barrel unit 62 when an acceleration in the collapse direction of the lens barrel unit 62 exceeds 1 G (1 G over), a higher torque is required than the one with the case wherein the camera is downwards. Therefore, in the case of 1 G over, compared with the case of the downwards posture, an even higher voltage (hereinafter referred to as a 1 G over collapse voltage) is applied.
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