Indicating grating of grating ruler

Abstract

The invention relates to an indicating grating of a grating ruler, which is characterized in that an incremental code channel, an absolute or zero window, a cross window and a device bonding window are carved on the indicating grating, and the front surface of the indicating grating is plated with chromium; the incremental code channel and the absolute or zero window are respectively positioned on two sides of the cross window; the incremental code channel of the indication grating corresponds to the incremental code channel of the main grating and the pixel of the photoelectric device for receiving the incremental signal, and the absolute or zero window corresponds to the absolute or zero code channel of the main grating and the pixel of the photoelectric device for receiving the absolute or zero signal; the windows of the incremental code channels follow the arrangement mode of phase differences of 0, pi / 2, 3pi / 2 and pi, and when illumination light divergence and temperature change exist in the grating ruler and linear errors are introduced in the process of manufacturing the indication grating, the position error increase in the period of the grating ruler is not obvious, so that the signal quality is improved.

Description

Technical Field

[0001] The invention relates to an indicating grating of a grating ruler and belongs to the technical field of photoelectric measurement. Background Art

[0002] Grating rulers have the advantages of high precision, high resolution, good repeatability, low environmental sensitivity, etc., and also have extremely high cost performance. Therefore, they are widely used in precise displacement measurement and motion control, such as CNC machine tools, robots, precision motion control systems, fault diagnosis systems, etc.

[0003] The grating ruler used on CNC machine tools generally consists of two parts: one is the ruler shell, including the ruler shell, ruler shell end cover and main grating, etc.; the other is the reading head, including the carriage, indicating grating carriage, lighting mechanism, indicating grating, photoelectric device and internal circuit board, etc. The grating ruler actually measures the position through the relative movement between the ruler shell and the reading head. When the ruler shell and the reading head move relative to each other, the main grating in the ruler shell and the indicating grating in the reading head also move relative to each other. The moiré effect of light is used to convert the position movement into the movement of light and dark moiré fringes, which are then converted into digital signals by the photoelectric receiving device to measure the position.

[0004] In the process of developing grating rulers, the design of the indicator grating will affect the final signal quality. Traditional indicator gratings have the following shortcomings: the alignment accuracy of the indicator grating and the main grating is not guaranteed; the chrome-plated pattern on the surface of the indicator grating does not consider connectivity and area maximization, which affects the anti-static interference ability of the indicator grating; the surface of the indicator grating is plated with bright chrome, and there is stray light that affects the signal quality; the grating lines of the indicator grating incremental code follow the arrangement of phase difference 0, π / 2, π, 3π / 2. When the grating ruler has illumination light divergence, temperature changes, and linear errors introduced in the process of making the indicator grating, the position error within the period of the grating ruler increases significantly. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an indicating grating of a grating ruler which can provide high-quality signals.

[0006] In order to solve the above technical problems, the indicating grating of the grating ruler of the present invention is engraved with an incremental code track, an absolute or zero position window, a cross window and a device bonding window, and the front side of the indicating grating is chrome-plated; it is characterized in that the incremental code track and the absolute or zero position window are respectively located on both sides of the cross window; the incremental code track of the indicating grating corresponds to the incremental code track of the main grating and the pixel for receiving the incremental signal of the photoelectric device, and the absolute or zero position window corresponds to the absolute or zero position code track of the main grating and the pixel for receiving the absolute or zero position signal of the photoelectric device; the windows of the incremental code track follow the arrangement mode of phase difference 0, π / 2, 3π / 2, π.

[0007] Assume that the grid pitch of the incremental code channel is d, each window consists of n grid lines, and the width of the window is nd; the starting distance between the second window and the first window of the incremental code channel is nd+d / 4, the starting distance between the third window and the first window is 2nd+3d / 4, and the starting distance between the fourth window and the first window is 3nd+d / 2. Every four windows form a group, and the arrangement of the remaining windows is the same as that of the previous four windows.

[0008] The device bonding windows are transparent windows arranged at intervals, which are located around the incremental code channel, the absolute or zero position window and the cross window and correspond to the bonding frame of the photoelectric device.

[0009] Furthermore, the present invention also includes a position adjustment code channel; the position adjustment code channel is located on the left side, the right side, or both sides of the device bonding window.

[0010] Each position adjustment code channel consists of two windows with a phase difference of π / 2.

[0011] Each position adjustment code channel consists of two windows with a phase difference of π.

[0012] Each position adjustment code channel consists of four windows with a phase difference of π / 2.

[0013] The chrome-plated area of ​​the indicator grating is plated with dark chrome, and all the chrome-plated areas are connected.

[0014] The cross window is a transparent window corresponding to the marking line on the main grating.

[0015] The present invention has the following beneficial effects:

[0016] 1. The window of the incremental code channel follows the arrangement of phase differences of 0, π / 2, 3π / 2, and π. When the grating scale has illumination light divergence, temperature changes, and linear errors introduced in the process of making the indicator grating, the position error within the period of the grating scale does not increase significantly, thereby improving the signal quality.

[0017] 2. The position of the indicator grating is preliminarily adjusted through the cross window, and then the position of the indicator grating is accurately adjusted through the position adjustment code channel, which can accurately ensure the position relationship between the indicator grating and the main grating.

[0018] 3. The device bonding window adopts transparent windows arranged at intervals, so that the chrome-plated areas on the surface of the indicator grating are all connected, while maximizing the area of ​​the chrome-plated area as much as possible, thereby improving the anti-static interference ability of the indicator grating.

[0019] 4. The chrome-plated area on the surface of the indicator grating is plated with dark chrome, which can reduce the influence of stray light on signal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the indicating grating pattern of the present invention.

[0021] Figure 2 It is a diagram showing the relative positions of the grid lines in the incremental code channel.

[0022] Figure 3 It is a schematic diagram of a photoelectric device.

[0023] Figure 4 It is a schematic diagram of the bonded indicator grating and photoelectric device.

[0024] In the figure: 1. Indicator grating; 11. Incremental code channel; 12. Absolute or zero position window; 13. Cross window; 14. Device bonding window; 15. Position adjustment code channel; 16. Chrome-plated area; 17. Front of indicator grating; 18. Back of indicator grating; 2. Photoelectric device; 21. Pixel receiving incremental signal; 22. Pixel receiving absolute or zero position signal; 23. Bonding frame. DETAILED DESCRIPTION

[0025] The specific implementation modes of the present invention are further described below in conjunction with the accompanying drawings.

[0026] like Figure 1 As shown, the indicating grating of the grating ruler of the present invention is engraved with an incremental code channel 11, an absolute or zero position window 12, a cross window 13, a device bonding window 14, and a position adjustment code channel 15, and the front of the remaining area is a chrome-plated area 16; the incremental code channel 11 and the absolute or zero position window 12 are respectively located on both sides of the cross window 13; the incremental code channel 11 corresponds to the incremental code channel of the main grating and the pixel 21 for receiving the incremental signal of the photoelectric device 2, and the absolute or zero position window 12 corresponds to the absolute or zero position code channel of the main grating and the pixel 22 for receiving the absolute or zero position signal of the photoelectric device 2; the device bonding window 14 is located around the incremental code channel 11, the absolute or zero position window 12 and the cross window 13 and corresponds to the bonding frame 23 of the photoelectric device 2; the position adjustment code channel 15 is located outside the device bonding window 14.

[0027] The windows of the incremental code channel 11 follow the arrangement of phase differences of 0, π / 2, 3π / 2, π, where the phase refers to the phase of the moiré fringe signal received by the pixel 21 of the photoelectric device 2 receiving the incremental signal corresponding to each window of the incremental code channel 11. To achieve the arrangement of phase differences of 0, π / 2, 3π / 2, π, the following can be used: Figure 2The grid lines are arranged in a grid line arrangement manner, where d represents the grid pitch of the incremental code channel 11, and nd represents the width of each window, which is generally matched with the width of the pixel 21 of the photoelectric device 2 receiving the incremental signal, and each window is composed of n grid lines. The starting distance between the second window and the first window is nd+d / 4, the starting distance between the third window and the first window is 2nd+3d / 4, and the starting distance between the fourth window and the first window is 3nd+d / 2. Every four windows form a group, and the arrangement of the remaining windows is the same as that of the previous four windows. The intra-cycle position error of the grating ruler is an important consideration indicator of the grating ruler. The DC level, equal amplitude, orthogonality and sinusoidality of the grating moiré fringe signal will affect the intra-cycle position error of the grating ruler, among which orthogonality has the greatest impact, followed by DC level and sinusoidality, and equal amplitude has the least impact. Using the traditional 0, π / 2, π, 3π / 2 arrangement, when the grating scale has illumination light divergence, temperature changes, and linear errors are introduced in the process of making the indicator grating, the orthogonality of the grating moiré fringe signal will deteriorate, and the position error within the period of the grating scale will increase significantly; using the 0, π / 2, 3π / 2, π arrangement, when the system introduces linear errors, the equiamplitude of the grating moiré fringe signal will deteriorate, and although the position error within the period of the grating scale will also increase, the increase is much smaller than that of the traditional method.

[0028] The absolute or zero position window 12 of the indicating grating is determined according to the measuring method of the grating ruler. If it is an absolute grating ruler, an absolute window is engraved on the indicating grating, and the absolute window is generally a transparent window; if it is an incremental grating ruler, a zero position window is engraved on the indicating grating, and the pattern of the zero position window corresponds to the zero position pattern on the main grating.

[0029] The cross window 13 of the indicator grating is a transparent window, which corresponds to the marking line on the main grating. The position of the indicator grating can be preliminarily adjusted according to the positional relationship between the cross window 13 and the marking line.

[0030] like Figure 3 As shown, the periphery of the photoelectric device 2 is a bonding frame 23, and the bonding frame 23 is provided with a pixel 21 for receiving an incremental signal and a pixel 22 for receiving an absolute or zero position signal; the bonding frame 23 matches the device bonding window 14 in size; when bonding the photoelectric device 2 to the indicator grating, firstly, UV glue is applied to the bonding frame 23, the relative position of the photoelectric device 2 and the indicator grating is adjusted, the bonding frame 23 is pressed against the back side 18 of the indicator grating, and the device bonding window 14 is illuminated by a UV light source, so that the photoelectric device 2 and the indicator grating are bonded together; Figure 4The bonding indicator grating 1 and the photoelectric device 2 are bonded. The device bonding window 14 is a transparent window arranged at intervals. The advantages of this are: it can ensure the light transmittance of the window, facilitate the curing of the ultraviolet glue, and ensure the connectivity of the chrome-plated area 16, and improve the anti-static interference ability of the indicator grating.

[0031] The left side, right side or both sides of the device bonding window 14 on the indicator grating are engraved with position adjustment code tracks 15. Each position adjustment code track 15 can be composed of two windows with a phase difference of π / 2, such as the arrangement of 0 and π / 2, or two windows with a phase difference of π, such as the arrangement of 0 and π, or four windows with a phase difference of π / 2, such as the arrangement of 0, π / 2, π, and 3π / 2. The position of the indicator grating is precisely adjusted by observing the uniformity of the moiré fringes formed by the position adjustment code track 15 and the main grating incremental code track. The windows with phase difference are provided to facilitate the observation of the uniformity of the moiré fringes, because the brightness of the moiré fringes of windows with different phases is different, and a certain contrast is more convenient for observation. When the uniformity of the moiré fringes of the window is good (that is, the brightness of the moiré fringes is consistent), it can be considered that the relative position of the indicator grating and the main grating is correct. The moiré fringes formed by the indicator grating incremental code channel 11 and the main grating incremental code channel are not directly observed here. This is because in order to improve the sinusoidal nature of the moiré fringe signal, an offset displacement processing is generally performed on the indicator grating incremental code channel 11. At this time, the observed moiré fringe pattern is also offset, and it is difficult to see its uniformity.

[0032] The chrome-plated areas 16 of the indicator grating are all plated with dark chrome, because dark chrome has a lower reflectivity, which is beneficial to reducing the influence of stray light on signal quality. All chrome-plated areas 16 are connected.

Claims

1. An indicating grating of a grating ruler, on which an incremental code track (11), an absolute or zero position window (12), a cross window (13) and a device bonding window (14) are engraved, and the front side of the indicating grating is chrome-plated; characterized in that: The incremental code channel and the absolute or zero position window are respectively located on both sides of the cross window; the incremental code channel of the indicator grating corresponds to the incremental code channel of the main grating and the pixel (21) of the photoelectric device receiving the incremental signal, and the absolute or zero position window corresponds to the absolute or zero position code channel of the main grating and the pixel (22) of the photoelectric device receiving the absolute or zero position signal; the windows of the incremental code channel follow the arrangement mode of phase difference 0, π / 2, 3π / 2, π.

2. The indicating grating of the grating ruler according to claim 1, characterized in that: Assume that the grid pitch of the incremental code channel is d, each window consists of n grid lines, and the width of the window is nd; the starting distance between the second window and the first window of the incremental code channel is nd+d / 4, the starting distance between the third window and the first window is 2nd+3d / 4, and the starting distance between the fourth window and the first window is 3nd+d / 2. Every four windows form a group, and the arrangement of the remaining windows is the same as that of the previous four windows.

3. The indicating grating of the grating ruler according to claim 1, characterized in that: The device bonding windows are transparent windows arranged at intervals, located around the incremental code channel, the absolute or zero position window and the cross window and corresponding to the bonding frame (23) of the photoelectric device.

4. The indicating grating of the grating ruler according to claim 1, characterized in that: It also includes a position adjustment code channel (15); the position adjustment code channel is located on the left side, the right side, or both sides of the device bonding window.

5. The indicating grating of the grating ruler according to claim 4, characterized in that: Each position adjustment code channel consists of two windows with a phase difference of π / 2.

6. The indicating grating of the grating ruler according to claim 4, characterized in that: Each position adjustment code channel consists of two windows with a phase difference of π.

7. The indicating grating of the grating ruler according to claim 4, characterized in that: Each position adjustment code channel consists of four windows with a phase difference of π / 2.

8. The indicating grating of the grating ruler according to claim 1, characterized in that: The chrome-plated area of ​​the indicator grating is plated with dark chrome, and all the chrome-plated areas are connected.

9. The indicating grating of the grating ruler according to claim 1, characterized in that: The cross window is a transparent window corresponding to the marking line on the main grating.

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