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Taiwan’s UMA Technology develops optical testing equipment for industry to provide accurate, rapid and reliable lens error detection schemes. Renishaw has supplied the optical encoder components for UMA Technology’s E1 series, designed for small lens mass production line testing.

Taiwan’s UMA Technology develops optical lens testing equipment to ensure smartphone camera quality

The general test process starts with the precise placement of a lens tray on the DSC-E1 series’ mobile platform; the candidate lens is then lined up with the standard chart and the imaging sensor beneath. Each lens test examines nine to 25 image regions such that the total time taken for each lens is less than three seconds. 

The platform moves with high speed back and forth, in both X and Y directions, and accuracy depends on high-quality closed-loop feedback information provided by an optical encoder on each axis. Sentry Lee, UMA senior project manager, said: ‘The mobile platform is one of the core components of the testing equipment; it has a decisive influence on test results and uses two stepper motors with a screw-drive system. Renishaw’s RGH22 optical encoder system with self-adhesive RGS20 scale and 0.1µm resolution is installed on both X and Y axes of the platform. The linear stage can position a lens, in line with the light source and image sensor, with an overall accuracy of 1–2µm.’ 

Key benefits of product application

  • UMA wanted the highest yield possible and minimal scrap as a result of testing errors, leading to the general requirement for a detection error rate of ±3 per cent. Lee said: ‘Prior to redesign, the linear stage on the equipment was driven by only stepper motors, offering an unsatisfactory level of repeatability. Installation of Renishaw’s RGH22 encoder system has enhanced resolution to 0.1µm, which improves our product competitiveness.’
  • The scale of a typical encoder, attached in some way to the machine structure, is the basis for measurement performance of the system. In general, the thermal expansion of the scale will not match that of the supporting substrate, which is often made of a different material. Choosing granite confers its various benefits including lower thermal expansion. Conventional scales then lead to measurement uncertainty over temperature — a problem completely eliminated by using the Renishaw RGS20 self-adhesive tape scale, which is essentially a gold-faced steel strip of 6 x 0.1mm cross section. This is mastered to the substrate and expands precisely with it, ensuring the elimination of hysteresis for completely predictable metrology as well as easy installation without the need for fixing holes.
  • Speed is another important factor in the industry’s assessment of equipment performance. Lee said: ‘There is a gap between the edge of the lens and the insert on the tray. The original system had to re-adjust position until the lens, light source and image sensor were aligned, which often took several attempts. Consequently, enhancing process efficiency was a big challenge for us. Renishaw’s high-performance encoder allows our latest system to locate the correct position at once, reducing processing time significantly.’
  • According to Lee, Renishaw’s encoders are well known in the market and, when compared with other brands, have the best cost-performance ratio. Renishaw also offers excellent after-sales service, quick response and fast delivery.


A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

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