Photoelectric displacement sensors are high-precision measurement devices based on the photoelectric effect principle. It detects minute displacement changes in objects using optical or laser technology, and is characterized by high sensitivity, rapid response and miniaturized structure.

A domestic high-tech enterprise, possessing fully independent intellectual property rights, specializes in the R&D and manufacturing of displacement sensors (rotary and linear), particularly miniature photoelectric displacement sensors and servo control systems, achieving world-leading standards.

In recent years, leveraging the high precision and miniaturization of its precision motion drive technology, the company has provided customers with more comprehensive technical solutions. It has successfully transformed its core technologies into multiple aerospace, military, and civilian products, such as aviation electro-optical pods and servos, aerospace gyroscope status sensors, Multi-Leaf Collimators (MLCs) for medical accelerators, insulin pumps, and joint drive units for assistive robots. 

Stringent Yield Requirements from Key Clients Drive Quantitative Roughness Control  

Recently, while fulfilling an order for an aerospace client, the company faced new demands for product accuracy and signal transmission stability. After analyzing the production process, they discovered that the roughness of encoder disks and the etching depth and width of code tracks in their absolute displacement sensor modules critically impacted performance. Implementing quantitative control over the roughness and etching dimensions of these components became imperative.  

Upon identifying the need for quantifiable data, the company evaluated white light interferometers from four domestic and international brands. After extensive data verification and testing, they shortlisted two brands whose accuracy met the requirements for final comparison, ultimately selecting and procuring the Atometrics White Light Interferometer.  

Precision Roughness Quantification  

Component Fatigue Life Increased by 50%  

Through equipment testing and validation, the R&D team found that encoder disk roughness affects the following product performance aspects:  

1. Measurement Accuracy: The surface roughness of encoder disks influences signal acquisition between photoelectric sensors/mechanical probes and the disks. For instance, in high-precision angular measurement systems, encoder disk surface roughness must typically reach the nanoscale. Rough surfaces may increase measurement errors, failing to meet system accuracy requirements.  

Encoder Grinding Surface Test Sample  

In preliminary tests, the company used encoder disks with surface roughness levels of 100nm, 30nm, and 10nm to validate signal stability. At a roughness of ~10nm, the yield rate fully satisfied the client’s requirements.  

2. Service Life: Rough surfaces increase friction with other components (Such as read heads). Long-term use accelerates part wear, degrading encoder disk performance and shortening lifespan. Additionally, wear debris may enter the encoder, disrupting other components.  

Laser-Etched Microstructure of Encoder Code Track

Extensive testing revealed that encoder disks with a surface roughness (Sa) of 10nm exhibited 30% higher vibration amplitude and ~50% longer fatigue life compared to those with Sa=100nm.

By implementing quantitative roughness control and data management for etching width and depth, the company successfully resolved production process challenges, significantly enhanced key metrics for related product models, and delivered the core client’s order.

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