Absolute grating ruler and its measuring method based on cmos image sensor

Abstract

The invention discloses an absolute grating scale and a measuring method based on a CMOS image sensor, the absolute grating scale comprises a grating scale main body, an optical amplification system, a CMOS image sensor, a signal processing module and a master control module, a measurement code track and a subdivision code track are arranged on the grating scale main body, the optical amplification system is used for collecting light rays reflected or transmitted through the measurement code track and the subdivision code track, the light rays converge and are incident on the CMOS image sensor, the CMOS image sensor is used for collecting the reached light signal to obtain an analog image of the present measuring position and transmitting the analog image to the signal processing module, the signal processing module is used for converting the analog image into a digital image and transmitting the digital image to the master control module, and the master control module is used for processing the digital image to separately obtain a rough measurement position value and a subdivision position value and combining the position values to obtain an absolute position measured value. According to the invention, the measurement accuracy is high, the measurement resolution is greatly improved, and the grating scale and the method can be widely applied in grating measurement industry.

Description

technical field [0001] The invention relates to the field of grating ruler measurement, in particular to an absolute grating ruler based on a CMOS image sensor and a measuring method thereof. Background technique [0002] The absolute grating ruler is used to detect the absolute position of the linear displacement. In the current technology, the physical scale of vertical encoding is generally used, and then the integrated photocell with the same length as the grating pitch is used to detect the absolute position. At the same time, in order to improve the position resolution, This type of grating scale is often attached with a sine-cosine incremental detection channel, and the position resolution can reach up to 0.005 microns through the subdivision of the incremental output signal. However, in the current absolute grating ruler, the grating code track is depicted on glass or steel belt and other materials, and the motor will inevitably produce a certain radial runout during...

AI Technical Summary

Problems solved by technology

However, in the current absolute grating ruler, the grating code track is written on glass or steel belt and other materials, and the motor will inevitably produce a certain radial runout during operation, which may cause a small displacement of the code track. When the radial displacement caused by vibration reaches a certain amplitude, there may even be false readings

Moreover, the traditional absolute grating scales all use grating codes, which have high requirements for grating writing technology, such as binary code discs, n-bit binary code discs have 2 n different codes, if you want to improve the resolution of the absolute grating ruler, you must increase the value of n

With the increase of the value of n, more and more grating dimensions are added, resulting in larger grating size and greatly increased production costs. Moreover, this method has a limitation on the encoding range, which limits the expansion of the measurement range.

In addition, the slight production error of the binary raster code track will advance or delay the individual code track, which will cause the error of the output signal

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