Renishaw's Zsombor Zelena collaborates with 3DHISTECH Ltd, a pathology equipment and services specialist, to provide them with the latest in encoder technology. Watch the video summary below and read the full article for further information and links.
Located in Budapest, Hungary, 3DHISTECH designs and manufactures one of the world's fastest and highest-capacity autonomous panoramic digital slide scanners – the P1000.
The P1000 is a highly accurate scanning microscope that enables large pathology labs to capture ultra-high resolution images of medical samples, while operating unmanned for up to 2 days. Building upon 3DHISTECH's successful product range, this new generation of digital slide scanner is the first to have integrated optical and magnetic position feedback encoders for enhanced throughput.
The VIONiC™ digital incremental optical encoder system with RTLC-S stainless steel tape scale has been installed on the three axes of the microscope, and the absolute LA11 magnetic encoder system was selected for the pick-and-place robot of the slide loader. These encoders enable the P1000 to operate at higher speeds than competing products in an accurate and repeatable way.
During a scanning procedure, a stage with the sample is moved in the horizontal plane, along the X and Y axes, while the lens is adjusted vertically to maintain image focus. The higher the magnification, the greater the accuracy required to ensure accurate stitching of multiple photomicrographs to create a high resolution image.
3DHISTECH specified a high resolution encoder, ultra-precise mechanics, and a fine-tuned process control system with a short control response time. These requirements are challenging in terms of mechanical and electrical engineering. Engineers had to minimise the stick-slip effect, and create a control loop with precise feedback for driving a piezomotor with a 100 nm step-size. The readhead's resolution and noise level (non-repeatable errors) were the most important performance parameters that influenced selection of the encoder system.
For the pick-and-place robot of the slide-loader, a high accuracy encoder was unnecessary as wide setup tolerances and easy installation were more important, as was reliability. When designing the microscope, the engineers chose the same encoder specification for each axis to simplify installation and servicing. They also selected cut-to-length scales, which allows the stocking of compact tape scale reels.
The encoder systems are surprisingly easy to install and set up in light of their performance.
Since the step-size of the chosen piezo-motor is 100 nm, the required resolution of the encoder is 50 nm to allow sufficient servo-bandwidth. The depth of field of the lens with the highest magnification factor is 0.2 μm, which gives every design parameter a sizable safety margin. The sample holder slides on a granite block to minimise frictional forces and vibration transfer from the outside.
The VIONiC series is Renishaw's ultra-high accuracy, all-in-one digital incremental encoder for both linear and rotary applications. VIONiC combines all necessary interpolation and digital signal processing inside the readhead, with cyclic error as low as <±10 nm and resolutions down to 2.5 nm. It has many customizable parameters, from resolution and edge separation to connector-type and cable lengths. Unrivalled ease of set-up and calibration is supported by an Advanced Diagnostic Tool (ADT), which includes user software that allows remote control and monitoring of VIONiC's set-up and calibration routines.
The pick-and-place robot comprises three belt-driven axes with encoder feedback. In this case, the LA11 magnetic encoder by Renishaw's associate company RLS is the ideal solution as it is a true-absolute encoder system with a large rideheight tolerance. The controller uses SPI protocol (Serial Peripheral Interface - an absolute signal protocol), so the LA11 encoder with RS422 (a digital 5 V-potential incremental signal protocol with twisted pairs) parallel output is the optimal solution for the robot to achieve the specified accuracy of ±0.1 mm. Furthermore, the true-absolute measuring principle protects the samples in the event of unexpected shutdowns: after a power outage the encoder reports its position immediately upon power restoration without the need for time-consuming homing cycles.
With Renishaw's technical support, 3DHISTECH's engineering team were able to specify an encoder for each machine axis and find the appropriate encoder products for their applications. Advanced encoders, such as Renishaw's VIONiC series and RLS' LA11 magnetic encoder, enable the P1000 to achieve truly market-leading performance.
3DHISTECH was founded in 1996 and manufactures high-speed slide scanners and digital microscopes. Its aim is to fully digitalise the traditional pathology workflow to meet the ever growing demands of 21st century healthcare. 3DHISTECH's facility is located in Budapest, but it has machines all over the world from Europe and US to East Asia, including Korea and Japan.
RLS d.o.o is a Renishaw associate company. RLS produce a range of robust magnetic rotary and linear motion sensors for applications such as industrial automation, metalworking, textiles, packaging, electronic chip / board production, robotics and more.