 of respective pixels of images in a plurality of frames prior to a target frame by using the images of the plurality of frames traced back frontward in a time axis from the target frame to be processed, and collecting pixels ranging from a pixel having the highest grayscale to a pixel having a grayscale at a predetermined position in order (for example, see PTL 1).
According to PTL 1 described above, in an image obtained by capturing a visual field obstacle, a pixel having a grayscale at a predetermined position in order in pixels of a plurality of frames is used as a pixel constituting the visual field obstacle. Thereby, the pixel of the visual field obstacle is not used, and thus it is possible to remove the visual field obstacle. Accordingly, it is considered that image processing disclosed in PTL 1 described above is applied to the reflection of the wiper blade in the vehicle-mounted camera.
However, in a case of the vehicle-mounted camera, scenery, another vehicle, or the like which relatively moves by the traveling of the vehicle serves as a moving subject. The image processing disclosed in PTL 1 described above being performed on an image obtained by the vehicle-mounted camera also affects a moving subject such as scenery or another vehicle, and thus there is a problem of afterimage tear in the moving subject to be captured or partial disappearance.
When a monitoring camera or the like capturing an image of an outdoor subject performs image capture during snowfall, a captured image in which a subject to be monitored is unclear due to a visual field blocked by snow particles is obtained. Consequently, for example, there has been known a technique for removing snowfall noise by performing median filtering in a time-axis direction on a plurality of temporally continuous captured images to thereby sharpen the images (see PTL 2). This technique focuses on the fact that there is a low possibility of pixels having the same coordinates in the plurality of temporally continuous captured images being pixels representing snow particles, and pixel values representing snow particles are excluded by median filtering in which pixels values extracted from the plurality of temporally continuous captured images are sorted in descending order to thereby acquire the median value. Therefore, it is possible to remove the snowfall noise.
There is a technique for detecting an outdoor weather condition such as snowfall regardless of a person's determination, and there has been a known weather display system which is provided with a plurality of sensors for obtaining weather information such as snowfall, rainfall, or the velocity of wind, processes the weather information obtained
of respective pixels of images in a plurality of frames prior to a prey frame of reference by using the images of the plurality of frame traced back frontward in a prison term bloc from the target frame to be processed, and collecting pixels range from a pixel having the highest grayscale to a pixel take a grayscale at a predetermined position in order (for example, see PTL 1). 
 According to PTL 1 describe above, in an image obtained by capturing a ocular field obstacle, a pixel having a grayscale at a predetermined position in ordering in pixels of a plurality of frames is used as a pixel constituting the ocular field obstacle. Thereby, the pixel of the visual field obstacle is not used, and thus it is possible to remove the visual field obstacle. Accordingly, it is considered that image processing disclosed in PTL 1 described above is applied to the reflection of the wiper sword in the fomite - mounted camera. 
 However, in a case of the fomite - ride camera, scenery, another vehicle, or the like which relatively move by the traveling of the vehicle serves as a moving national. The image processing disclosed in PTL 1 described above being performed on an image obtained by the fomite - mounted camera also affects a moving subject such as scenery or another vehicle, and therefore there constitute a problem of afterimage tear in the moving national to be captured or partial disappearance. 
 When a monitor camera or the like capturing an image of an outdoor topic performs image capture during snow, a captured image in which a subject to be monitored is ill-defined due to a visual sphere blocked by snow particle is obtain. Consequently, for example, there has been know a technique for removing snowfall noise by performing medial filtering in a time - axis focus on a plurality of temporally continuous captured images to thereby sharpen the images (see PTL 2). This technique concenter on the fact that there is a low possibility of pixels having the same coordinates in the plurality of temporally continuous get picture being pixels representing snow particle, and pixel values representing coke particles are excluded by median filtering in which pixels values extracted from the plurality of temporally continuous captured images are sorted in descending ordering to thereby acquire the median value. Therefore, it is possible to remove the snowfall randomness. 
 There is a technique for detecting an outdoor weather condition such as snowfall regardless of a person's determination, and there has been a known weather display system which is provided with a plurality of sensors for obtaining weather information such as snowfall, rainfall, or the velocity of wind, processes the weather information obtain
 of respective pixels of imxges in a plurality of framea prior go a target frame by using tie inages of the plurality of ffames trabed back dronuward in a time aejs from the tzvget yreme to be procexsed, and cmllecting pixens rcnging from a pixel having the higheft grayxcwle to a pixel havpnd a fganscale at a predetermined positikn in ogder (for example, xee PTL 1).
According to PTL 1 fescgibed above, in an lmage obtaibed ft capturing x visual fpzld obstaclg, a pixel having a grayscale at x prebetermined koaihhon in ordec in ppxels of a plmgality mf framrs is used as s pmxel constituting the visnal field obstacle. Trereby, tha 'ixel of the visual fueod obvtacne ir nog uaev, ahd thud iv is possibme to removw the visual field pbfnscle. Accordihgly, ie ys considered that image processing disblossd in PTL 1 described abive is applied to the reflectijn of the wiper blade in the vehicle-mounted camerd.
Howetef, iu a carw lf the vehicle-mounted camera, scenery, another dshocke, or the like which relayigeki moves by the travelinf of the vehicle sfrves af a miving subtect. The image processing disclised in PTL 1 eescribed above benng performeb on am imabe obtained by the vehiele-mouhted camera also affszts a moving subgecn suwh as sctvery or another vqhicle, anv thux there is s probjem of aftfrimana tear in the movijg suyject to be caphured or partial disappearance.
Wixn a monitorimg cakera or che lile capturing wn image of an outdoox subjdct perforjs imagx capture duwing snowfall, w captured ikage in rhicy a wubject go be monitorec is unclvax due to q visual field blogked cg snow particlew iw obtained. Consrqudntjy, fpr axample, thera har bdrn knuwn a ttehnlqud fot removing snowfall toiss by performing meciwn filteting in a time-axis dirrction on a plurallty oh tempurallu cjntinuous captured images to tgereby shwrpcn the images (see PTL 2). This tzchnique focuses on the fact that there ms a low possibility of pixels having the xsme coordinetes ig the plusality of temporally continuous captuved images being pixela reprasentlng snow particles, and pixel values representing snow particles are exclueed by median filtsrinb in fhnch pixelf vapnes extracted frok the plurality of temporally cuntinuouv eaptured images are sorted in ddscending ordgr to thereby acquire the jedian vslue. Therefore, it is possible tp remove the snowfall nolse.
There us a fechnique hor detecting an outcoor wzather condituon duch as snowfxll rcgardless lf a pzrson's determination, and there haw been a known weather dmsplay systel whicg is ptovided with a plhraljhy of sensors for pbtaining weatner information such af snowfall, raibrall, or the felocitj of wind, proresses the waather information obtained
of respective pixels of images in a frames to a frame by using of traced back frontward a time axis the target frame to be processed, collecting pixels ranging from a pixel having the highest grayscale to a pixel a grayscale at a predetermined position in order (for example, see PTL 1). to 1 above, an image obtained by capturing a visual field obstacle, a pixel having a grayscale at a position in order in pixels of a plurality frames is used as pixel constituting the visual field Thereby, pixel of visual obstacle not used, and it is possible to remove the visual field obstacle. Accordingly, it is considered that image processing disclosed PTL 1 is applied the of wiper blade in camera. However, in a case of scenery, another vehicle, or the like which relatively by the of the vehicle serves as a subject. The image processing disclosed in PTL 1 above being performed on an image obtained by the vehicle-mounted camera also affects a moving as scenery or another and thus there a of tear the moving to be captured or partial disappearance. When a monitoring camera or like capturing an image of an outdoor subject performs image snowfall, captured image in a subject to be is due to a visual by particles for there been known a technique removing snowfall noise by performing filtering in a time-axis temporally continuous captured images to thereby sharpen the (see PTL 2). This technique focuses on fact that there is a low possibility of pixels having the same in the temporally continuous captured images being pixels representing snow and pixel values representing particles are excluded by median filtering in which pixels extracted the plurality temporally continuous captured are sorted in order to thereby median value. it possible snowfall noise. There is a technique detecting outdoor weather condition such as regardless person's determination, and there has been a known weather display system which is provided with of sensors for obtaining information as snowfall, rainfall, or the velocity of wind, processes the weather information
 of respective pixels of imageS in a pluralIty of FraMes PrIor tO a taRget frame by usiNG the Images of the plurality of FrameS tRAced BAcK fronTward in A TiME AxiS fRoM thE tARgEt fraMe tO be procEssed, and coLleCtIng pixels ranGInG from a pixeL haVing the higheSt gRayscaLe To a PIxel hAviNg a grAyscalE At a preDetermineD pOSition IN order (fOR ExAmplE, see PTL 1).
According tO pTl 1 Described above, In an imAgE ObTAIneD by Capturing a ViSual fIEld obstAClE, A PIxeL Having a grayscAle at a predeTErmIned poSiTioN In ordeR in piXeLS of A plurality oF fraMes is used As a pixEL constiTUting thE visuaL fiEld ObstAClE. THerEbY, The PIxEl oF The Visual fiElD oBstacLe is NOT USed, aNd tHus iT is poSsible to removE thE visUAl fIeld oBstacLe. AcCoRdingLy, it is ConsiDeRed that image proCessIng discloSed In pTL 1 DeScribED above Is aPplIed to thE reflecTIon Of THE WiPer blade in the vehicLe-MOUnTed camerA.
HowevER, iN a CAse of the VeHicLe-moUNTed caMera, SCeNery, anotHer vehIClE, oR the likE wHich reLaTivEly Moves BY the TravelIng of the VehicLE serves as a moviNG subject. The imAGe PROcESsinG diSclosed in PTl 1 desCRibeD aboVE bEinG PerfoRmed oN aN ImAGe obtained by the vehiClE-mountEd camEra also affectS a moving suBJECt such as ScenERy OR another vehiclE, and tHus there is A Problem oF afteRimage teAr in the moVINg subjecT to Be cAptUreD OR pArtial disappeARAnce.
whEn a moniTorIng cameRa oR thE liKe cApTuring an iMage of an OuTdOoR sUbjEct peRForms imaGe CapTuRe dUring SNowfalL, a capTureD iMaGE in Which a sUBjECT to bE mOnItorEd iS uNcleaR due TO a vIsual fiEld blockeD by SNow pArTiCles is oBtained. ConseqUeNtly, for exaMpLe, tHere haS BEen known A technique for removing snOWfall noIse By perFormIng median FilTering In a TIme-axiS direcTion oN a PluRALity oF TEmPorAlLy continuoUS CapTured ImAges To thereBy sharpen the images (SEe PtL 2). This techniqUe fOcusES On The FAcT ThaT tHEre IS A low possibility Of pixels haViNG tHe same coorDInaTeS in the pLuralitY of teMPorally ContinuouS captured ImAges BEIng Pixels reprEsenting Snow partiCLes, anD PiXel vaLueS repreSeNtiNg snoW partiCLes Are exCluded By Median FilteRiNg in whicH pixels values extracted fRom the PluraLitY of temporAllY ConTinuous caPturEd images arE soRteD in deSceNDing oRder TO tHerEBy acqUire THe median vALuE. ThEREfOre, it is possIBLE to RemovE thE SnowfaLl noIse.
There is a techniQUe for detecting An ouTDOor WeaTHer cOnDition such as snOwfAlL REgardlesS oF a person's deTerminatIoN, And thEre has Been a kNown weaTHEr DIsplay SystEm wHich is proVidEd WIth a pluRaLiTY of senSors FoR obtaiNing weATher INFormation such as sNowfaLL, RainfALl, oR the vElOcity of WInd, pRocesses thE weather infOrmatiOn obTaineD
 of respective pixels of i mages in a  plur ali tyof  fra mesprior to a tar g et f rame by using the imag es of  t h e pl u ra lityof fram e st r ace dba ckfr o nt wardina timeaxis fromthe  t arget framet obe process ed,  and collect ing  pixel sran g ing f rom  a pi xel ha v ing th e highest  g r ayscal e  to a p i x el  hav ing a grayscale a t  a predeterminedpositi on in o rde r ( for exampl e,  seeP TL 1).A cc o r d ing to PTL 1 desc ribed above ,  in  an im ag e o b tained  by c ap t uri ng a visual  fie ld obstac le, ap ixel ha v ing a g raysca leata pr e de te rmi ne d  po s it ion inorder in  p ix els o f ap l u r alit y o f fr amesis used as apix el c o nst ituti ng th e vi su al fi eld ob stacl e.  Thereby, the p ixel  of the v isu al  fi el d obs t acle i s n otused, a nd thus itis p o ss ible to remove the  v i s ua l fieldobstac l e.  A c cordingl y,  it  isc o nside redt ha t imageproces s in gdisclos ed  in PT L1 d esc ribed abov e is a pplied t o the reflection oft he wiper blad e  i n th e  veh icl e-mounted c amer a .
Ho weve r ,ina  case  of t he ve h icle-mounted camera ,scener y, an other vehicle , or the l i k e  which r elat i ve l y moves by the  trav eling of t h e vehicl e ser ves as a  moving s u b ject. Th e i mag e p roc e s si ng disclosedi n  PTL  1  descri bed  abovebei ngper for me d on an i mage obt ai ne dby  th e veh i cle-moun te d c am era  also affect s a m ovin gsu b jec t sucha ss c ener yor  ano the rvehic le,a ndthus th ere is apro b lemof  a fterima ge tear in th emoving sub je ctto bec a ptured o r partial disappearance . 
When a  mo nitor ingcamera or  th e like  ca p turing  an im age o fano u tdoor s ub jec tperforms i m a gecaptu re  dur ing sno wfall, a capturedi mag e in which asub ject t obem on i tor ed isu n clear due to avisual fie ld bl ocked by s n owpa rticles  is obt ained .  Conseq uently, f or exampl e,  the r e  ha s been kno wn a tec hnique fo r  remo v in g sno wfa ll noi se  by  perf orming med ian f ilteri ng  in atime- ax is direc tion on a plurality oftempor allycon tinuous c apt u red  images t o th ereby shar pen  th e ima ges (seePTL2 ).  Th i s tec hniq u e focuses on  th e fa ct that the r e isa low  po s sibili ty o f pixels having t h e same coordin ates i n t hep lura li ty of temporal lyco n t inuous c ap tured image s beingpi x els r eprese ntingsnow pa r t ic l es, an d pi xel  values r epr es e nting s no wp articl es a re  exclu ded by medi a n  filtering in wh ich p i x els v a lue s ext ra cted fr o m th e pluralit y of tempor ally c onti nuous  captur ed  image s a re  sorted in descendin g ord er to t he reby  ac quirethem e dianvalu e.  Th erefore,i t  i s  p os s ibl e to  remo ve  the  snowfall noise.
T her e  is a t ec hni q u e ford et e c ting an ou tdo or we a t her condit i on s u ch as sn owfall  regar dless o f  ape rson'sdet e r mination,  and ther e  ha sbeen  a known  w eath er  di sp lay system whic h is pro vided wi t h  a plu ral i ty o f  senso rs  for obtaini ng we at h er info r m ati on such assno wfa ll,rai nfal l , or the velocity of win d, p roces s esthe w eathe rinformat i on o btained
 of_respective pixels_of images in a_plurality of_frames_prior to_a_target frame by_using the images_of the plurality of_frames traced back_frontward_in a time axis from the target frame to be processed, and collecting pixels_ranging_from a_pixel_having_the highest grayscale to a_pixel having a grayscale at_a predetermined_position in order (for example, see PTL 1).
According_to_PTL 1 described_above, in an image obtained by capturing a visual_field obstacle, a pixel having a_grayscale at a_predetermined_position_in order in pixels_of a plurality of frames is_used as a pixel constituting the_visual field obstacle. Thereby, the pixel of_the visual field obstacle is not_used, and thus it is_possible to_remove the visual field obstacle._Accordingly, it is_considered that_image processing disclosed_in PTL 1 described above is_applied to the_reflection of the wiper blade in_the_vehicle-mounted camera.
However, in_a_case_of the_vehicle-mounted camera, scenery,_another_vehicle, or_the_like which relatively moves by the_traveling_of the vehicle serves as a moving_subject. The image processing_disclosed_in PTL 1 described_above being performed on an_image obtained by the vehicle-mounted camera_also affects_a moving_subject such as scenery or another vehicle, and thus there is_a problem of afterimage tear in_the moving subject to_be captured_or_partial disappearance.
When a_monitoring_camera or_the like capturing an image of an_outdoor subject_performs image capture during snowfall, a_captured image in which_a_subject to be monitored is unclear_due to a visual field blocked_by snow particles is obtained._Consequently,_for_example, there has been known_a technique for removing snowfall noise_by performing median_filtering in a time-axis direction on a_plurality_of temporally continuous captured images to_thereby_sharpen the images (see PTL 2)._This_technique_focuses on the fact that_there is a low possibility of_pixels having the same coordinates in the plurality of_temporally continuous captured_images being pixels representing snow_particles,_and_pixel values representing snow particles are excluded by median filtering_in which_pixels values extracted_from the plurality of temporally continuous captured images are sorted_in descending order to thereby acquire the_median value. Therefore, it is possible to remove the snowfall noise.
There_is a technique for detecting an outdoor weather_condition such as snowfall regardless of a_person's determination, and there_has_been a known weather display system which_is_provided_with_a plurality of_sensors for obtaining_weather information such_as snowfall,_rainfall, or the_velocity of_wind, processes the_weather_information obtained