WO2013174216A1

WO2013174216A1 - Single-track absolute grating scale and image encoding method thereof

Info

Publication number: WO2013174216A1
Application number: PCT/CN2013/075432
Authority: WO
Inventors: 陈新; 王晗; 陈新度; 刘强; 李克天; 马平; 李锻能; 陈学松
Original assignee: 广东工业大学
Priority date: 2012-05-24
Filing date: 2013-05-10
Publication date: 2013-11-28
Also published as: CN102706373A; DE112013002653T5; CN102706373B

Abstract

A single-track absolute grating scale and image encoding method thereof, comprising a light source, a reflector, incremental scale grating lines, a glass substrate, a movable diaphragm, a photoelectric receiver, and an indication grating; the light source and the reflector are combined into an illumination light path; the incremental scale grating lines having the same width are engraved on the glass substrate at equal intervals; milestone flags are engraved in parallel at equal intervals below the incremental scale grating lines on the glass substrate; the indication grating is embedded in an opening at the left upper part of the movable diaphragm; an upper and a lower CMOS sensors are respectively embedded in an upper and a lower symmetrical openings on the right of the movable diaphragm; the indication grating is installed closely against the glass substrate; the installation position of the upper CMOS aligns to the incremental scale grating lines; the installation position of the lower CMOS aligns to the milestone flags; and the light beams of the incremental scale grating lines and the indication grating form Moire fringes projected onto the photoelectric receiver. The present invention improves the acquisition speed of image information, improves code measurement accuracy, and can reliably encode, simply decode and quickly output a result.

Description

Instruction manual

Monorail absolute grating ruler and image coding method thereof

The invention relates to a monorail absolute grating ruler and an image coding method thereof, and belongs to a modification technology of a monorail absolute scale ruler and an image coding method thereof.

Background technique

The basis of the metrology grating technique is Moiré fringe. In 1874, the British physicist L. Rayleigh first proposed the engineering value of this pattern. It was not until the 1950s that people began to use the moire fringe of the grating for precise measurement. In 1950, Germany's Heidenhain pioneered the DIADUR replication process, which is a lithographic reproduction process that evaporates chrome on a glass substrate. This makes it possible to manufacture high-precision, inexpensive grating scales that can be accepted by users and enter the commodity market. In 1953, the British company Ferranti proposed a 4-phase signal system, which can realize 4 times frequency subdivision in a Moiré fringe period and can identify the moving direction. This is the 4 times frequency phase discrimination technology, which is the basis of the grating measuring system. Has been widely used so far [1]. At present, the commonly used grating scales can be divided into incremental grating scales, semi-absolute grating scales and absolute grating scales, which are used in the numerical control machine tool manufacturing industry. The incremental scale is the most commonly used high-precision measuring device. It has an absolute zero mark. The rear scale is equidistantly distributed. The read head moves relative to the scale grating. The moire fringe formed by the passing grid passes through the electricity. Signal processing, resulting in a distance from the absolute zero. This measurement mode is simple and easy, but in use, it is difficult to greatly improve the work efficiency because it has to be recalibrated every time it returns to the absolute zero point [2].

1

Replacement page (Article 26) In order to meet the needs of CNC machine tool upgrades, semi-absolute grating scales are gradually being used. The semi-absolute grating is to set the absolute rail on the incremental grating. On the absolute rail, a series of zero-position gratings coded by different distances are designed. In use, the absolute position is determined by detecting the distance of the adjacent zero-grating grating, which greatly reduces the absolute position. The time of zero return improves the working efficiency. In addition, when such a scale fails, it can immediately send an alarm signal to the CNC machine to ensure the safety of the processing.

Recently, the emergence of absolute gratings has revolutionized the equipment manufacturing industry. Compared to semi-absolute grating scales, absolute encoder gratings have more advantages. Since there are absolutely unique code values at any point, there is no cumulative error. It has the characteristics of high measurement accuracy, strong anti-interference ability, high stability, and can also perform nonlinear correction. In addition, the absolute coding range is large, so the linear displacement of a larger range can be measured [3].

The structure of the absolute grating ruler is relatively simple. The key point is the realization of absolute coding, and each absolute code corresponds to an absolute position on the grating scale, and the relative moving distance can be obtained by subtracting the absolute position of the starting point to the ending point. The cumulative error is avoided and the process of reading back the zero point is eliminated. At present, some kinds of absolute coding methods have appeared, which are more concentrated in the field of multi-track grating stripe coding. The advantage of this kind of coding is that the direct-reading column binary code is convenient for the photoelectric components to read data and improve the precision of the subdivision [4] ], but the main disadvantage is that it is more difficult to describe the grating scale, the coding range is limited, and it is difficult to expand the measurement range.

Monorail absolute coding technology solves this problem. The monorail absolute coding technique represents the development direction of international grating measurement, which is in line with the two trends of rapid measurement and miniaturization. However, due to the relatively complicated single-track absolute coding, the decoding method is cumbersome and the error rate is high.

2

Replacement page (Article 26) Still not in large numbers. Summary of the invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a monorail absolute scale which avoids the above-mentioned problems and which avoids the low yield of multi-track grating manufacturing, reduces manufacturing costs, improves the speed of image information acquisition, and improves the measurement accuracy of encoding. The invention has reasonable design, convenience and practicality.

Another object of the present invention is to provide an image encoding method that achieves reliable encoding, facilitates decoding, and quickly gives results.

The technical solution of the present invention is: The monorail absolute grating of the present invention comprises a light source, a mirror, a landmark mark, an incremental scale grid, a glass substrate, an upper CMOS sensor, a lower CMOS sensor, a moving aperture, and a photoelectric a receiver, an indicating grating, wherein the light source and the mirror are combined to form an illumination light path, providing parallel light, the glass substrate is patterned with an equal width and an equidistant incremental scale grid line, and the glass substrate is parallelized under the incremental scale grid line An equidistant landmark mark, the upper left opening of the moving aperture, the opening is embedded with an indicator grating, and the right upper and lower symmetrical openings of the moving aperture are respectively embedded in the upper CMOS sensor and the lower CMOS for acquiring image information The sensor, and indicating that the grating is mounted close to the glass substrate, the mounting position of the upper CMOS sensor is aligned with the incremental scale grid line, the mounting position of the lower CMOS sensor is aligned with the milestone flag, the relative position of the light source, the moving diaphragm and the photoreceiver Fixedly mounted on the movable ruler, the movable ruler can move back and forth relative to the glass substrate, the light source, And a movable stop parallel to the photoreceptor motion simultaneously, the incremental scale and the index grating of the gate line forming moire fringes projected light photoreceptor. The above light source is a blue light source.

The above-mentioned milestone flag line consists of a number of equally spaced gate lines. From the zero position, an absolute position mark is set at a certain distance to be a milestone flag.

3

Replacement page (Article 26) The milestone flag is divided into milestone code boundary marker raster lines for marking the appearance and end of the milestone, which is used to encode and expand the number of bits, that is, the effective coded bits in the milestone stripe group that can expand the range of the code; The effective coded gate line of the specific position of the gate line is depicted, and the gate line is denoted as 0, and the gate line is not depicted and left blank, where it is represented as 1, and the distance between adjacent landmark marks is d.

The above-mentioned effective coded gate lines have a total of 16 lines, and the end lines at both ends are used as boundary points to always depict the gate lines. The lower side CMOS sensor knows that it can read the complete mileage grid line shadow pattern once it is found that both ends pass.

The invention applies the image encoding method of the monorail absolute grating ruler, wherein the above-mentioned milestone flag bit is composed of a plurality of equal-width grid line bits, which presents a binary code to become the first coded bar code, and the parallel light provided by the illumination light path formed by the combination of the light source and the mirror The shadow line of the grid line generated by the incremental scale grid line constitutes the second coding area, and the image of the gate line stripe after the last milestone flag in the milestone flag coding window is digitally collected by the CMOS sensor to obtain a binary number. Coding, forming a second coded bar code, the margin of a step size in the last two raster lines is encoded by CMOS pixel insertion, which is a third code segment, and the three-segment code is combined to obtain a valid position code. , the position code corresponds to an absolute position on the scale, in other words, any absolute position on the scale has an absolute code composed of three segments, as long as a reliable indication of the starting position of the pupil is obtained. Absolute coding, you can get the absolute distance of the trip by the difference

The lower CMOS sensor directly collects the image coding information of the landmark flag, and the coded value is ^·, which is the first absolute position code segment, that is, the absolute position corresponding to the milestone flag bit is

M _x ' = N _x xd

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Replacement page (Article 26) The upper CMOS sensor directly captures the image of the incremental scale grid line and encodes it as follows: When the milestone flag stripe group appears completely in the monitor array of the lower CMOS sensor (7), the corresponding incremental scale grid line stripe , also instantaneously appear on the array of upper CMOS sensors, this stripe will be locked by the upper CMOS sensor, the scale grid line stripe beyond the milestone flag stripe group will be saved and encoded in the form of image, from the image, can Quickly distinguish the number of gate lines as K, and set the scale of the scale grid line to δ, then the exact incremental distance L beyond the absolute position marker is obtained by the number of dark lines in the incremental grid diagram, as follows:

= κ χ δ , this is the second code segment;

When the left end line of the indicating light-shielding area is between the adjacent grid lines of the incremental scale grating, the residual displacement is less than the spacing between one scale grid lines, and the measurement margin between the scale lines of the scale is set to ¹ , the measurement accuracy of the displacement It will directly affect the global measurement accuracy and the objectivity of absolute encoding. Due to the appearance of CMOS pixels with left and right CMOS pixel pitches, the CMOS pixel size is also smaller and smaller, and the encoding of the measurement margin between the scale bars is the third. Segment absolute coding; the distance between the above-mentioned scale grid lines is the linear distance between two adjacent grid lines of the scale grating, and the measurement margin between the scale grid lines refers to the linear distance from the left end line of the pupil light-shielding area to the leftmost end of the milestone. The CMOS pixel size refers to the width of the CMOS pixel, and the CMOS pixel pitch refers to the linear distance between two adjacent CMOS pixels, indicating that the light-shielding area refers to the area indicating the opaque light, that is, the non-opening area. , which indicates that the measurement end region is exceeded, and the measurement margin between the CMOS pixels refers to a linear distance indicating a CMOS pixel closest to the left end line of the pupil light-shielding region to the left end;

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Replacement page (Article 26) The third segment of absolute coding is divided into two parts, that is, the measurement margin between the scale grid lines is inserted into the integer CMOS pixel, and the numerical code is encoded as the first partial code; the traveling microscopic value of the measurement margin between the CMOS pixels is encoded. The code is expanded to the resolution level, and the code for the measurement margin between the scale bars is expressed by the following formula:

B Κ σ C

The final absolute position coding consists of three parts: the coding of the milestone flag, the grid code of the incremental scale grating, the coding of the measurement margin between the scale grid lines, and the C part of the position coding due to the measurement margin between the scales. Only the resolution level, so only save the part, after three-stage encoding, decoding, get any absolute position

Β X σ

M _x = N _x X d + KX 5 i-—^- The above-mentioned moire fringes generated by the grating are compared as the low-precision coding and the absolute position obtained by the CMOS. If the error is within a reasonable range, the code is determined to be normal. If the error range is exceeded, the coding error is considered, and the image information is re-read for correlation coding. If the new code value is equal to one of the previous analysis data, the code value of the re-encoding is considered correct, and vice versa. Alarm information.

The above-mentioned milestone flag is composed of 14 equal-width gate lines, which are binary coded, and 14 gate lines can form numbers ranging from 0-16383.

The spacing between the last scales of the above-mentioned scales is magnified 10 times by the projection micro-amplification technique, and an average of 100 pixel units will be distributed in this distance, and the spacing between the scales of the scales will be

6

Replacement page (Article 26) The distance between the two is equally divided into 100 parts, that is, the measurement accuracy is ο· ¹ ^, that is, one tenth of the CMOS pixel pitch. The measurement margin between the above-mentioned scale grid lines is accurately quantized according to the precision of the above-mentioned one-tenth CMOS pixel pitch, and indicates the distance traveled between the pixels on the left end line of the pupil light-shielding region, that is, the measurement margin between the CMOS pixels passes through the electron Subdivided into 128 copies, making the resolution σ

Within 1280.

The upper CMOS sensor is aligned with the incremental scale grid line, and the lower CMOS sensor is aligned with the milestone flag. When moving at high speed, the landmark marker position is used to reduce the amount of data collected by the image, and the speed of the linear motion is increased. When nearby, the deceleration acquisition analyzes the coding information of the incremental scale grid. Compared with the prior art, the invention has the following advantages:

1) The present invention performs absolute encoding by a monorail grating, which avoids low yield of multi-track grating manufacturing and reduces manufacturing costs.

2) The invention utilizes CMOS sensing technology to improve the speed of image information acquisition, and indirectly improve the measurement accuracy of the encoding by means of the processing precision of the semiconductor device.

3) The present invention introduces a microscopic amplification technique, which amplifies the margin between the last pair of gate lines, and further improves the accuracy of position coding by using the pixel insertion mode.

4) The invention reduces the importance of the traditional incremental coding in the measurement, but retains some of its functions, and provides a reference for error correction, thereby improving the reliability of the absolute grating coding and decoding, and at the same time being an absolute grating. When the ruler fails, it is used as a backup measurement tool to ensure a certain measurement function of the scale in the fault state. The invention is a monorail absolute grating with ingenious design, excellent performance and convenient and practicality.

Replacement page (Article 26) And its image coding method.

DRAWINGS

1 is a schematic view showing the structure of a monorail absolute scale of the present invention.

2 is a schematic view showing the structure of an absolute grating scale grating line of the present invention.

Fig. 3 is a schematic diagram showing the subdivision measurement between the grating scales of the absolute grating scale of the present invention.

detailed description

Embodiments: A schematic structural view of a schematic diagram of a monorail absolute grating of the present invention is shown in FIG. 1. In FIG. 1, a light source 1 and a mirror 2 are combined to form an illumination light path, which can provide parallel light of a certain light intensity, in this embodiment. The light source 1 is a blue light source and is a special light source. When the light of the parallel light is projected to the landmark mark 3 and the incremental scale gate line 4, the projection of the gate line is separately scanned and received by the upper CMOS sensor 6 and the lower CMOS sensor 7, and the two CMOS sensors are embedded in the moving aperture 8 Above, the light source 1, the mirror 2, the moving aperture 8, and the relative position of the photoelectric receiver 9 are fixed to form a dynamic measuring system, which are parallel to the glass substrate, and the external and measuring end mechanisms are connected, and an indicating grating is embedded on the moving aperture 8 10. The light passes through the scale grid 4 and the moiré fringes generated after indicating the grating 10 are received by the photoreceiver 9 to form an analog incremental signal. In Fig. 1, the lower side CMOS sensor 7 can directly collect the encoding information of the image of the milestone flag 3, and the coded value is , which is the first absolute position encoding segment, that is, the absolute position corresponding to the milestone flag bit (3) is

The upper CMOS sensor 6 can directly acquire the incremental scale grid image, but relies on the following techniques for encoding. The incremental gate line image coding technique is as follows: As shown in Fig. 2, when the landmark gate line of the landmark flag 3 stripe group is completely present in the lower side CMOS monitor array, the corresponding incremental scale grid line stripe also appears instantaneously in the upper side CMOS.

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Replacement page (Article 26) On the sensing array, this stripe will be locked by the image electronics, and the stripe stripe beyond the milestone flag 3 stripe set will be saved and encoded as an image. From the image, it can be quickly recognized that the number of dark lines is K, and the distance between the ruler grid lines is δ, then the precise incremental distance L exceeding the absolute position mark can be obtained by counting the number of gate lines in the incremental grid diagram. L = K x S This is the second code segment, combined with the first code segment, which will further improve the accuracy of the position measurement of the measuring end of the movable ruler. The milestone flag 3 is divided into several parts, namely, the milestone code boundary marker gate line 12, the effective coded bit position 11 in the milestone stripe group, the effective coded gate line level 13, and the adjacent milestone flag bit 3 are spaced by d, and the boundary is convenient for scanning. Positioning, the effective coded gate line 13 can depict the gate line, denoted as 0, or blank, denoted as 1, and the spacing of the adjacent milestone flag 3 is d to determine the coarse step size of the coded positioning. As shown in FIG. 3, it is indicated that the left end line of the pupil light-shielding region 19 is between two adjacent grid lines of the scale grating, and when the residual displacement is less than one gate line spacing, the measurement margin 16 between the scale grid lines is set to 1L, and the displacement is The measurement accuracy will directly affect the global measurement accuracy and the objectivity of absolute coding. Here we make full use of the new technology of CMOS development, due to the left and right

The CMOS pixel 14 of the CMOS pixel pitch 18 appears, the CMOS pixel size 17 is also getting smaller and smaller, and the subdivision technology is further upgraded. Using the projection micro-amplification technique, the spacing between the last scale grid lines 15 can be averaged by a factor of 10, assuming that the distance between the two grid lines is evenly distributed by 100 pixels, the distance between the two grid lines is equally divided into 100 parts, that is, the measurement accuracy can be achieve

0.1 o, the distance traveled between the pixels can also be subdivided into 128 by electronic, σ

This allows resolution to be achieved. This part of the code is the third paragraph of absolute coding, which

9

Replacement page (Article 26) The segment coding can be divided into two parts, that is, the measurement margin between the ruler grid lines is inserted into the integer number of pixels, and the code is coded as A for the first part of the code; the traveling microscopic value of the measurement margin (20) between the CMOS pixels Encoding can expand the encoding to the resolution level. As shown below, the measurement margin between the scale bars can be expressed by the following formula.

B Χ σ C

II = + X σ

10 1280

The final absolute position coding consists of three parts: Milestone absolute reference point marker code, relative position coding, subdivision position coding, since the C part of the subdivision position coding is only the resolution level, only the part is saved.

After three stages of encoding and decoding, you can get the absolute position.

Β X σ

Μ _χ = Ν _χ Χ ά + Κ δ δ + -^- The above indicates the moire fringes generated by the grating 10, as a low-precision coding, and the absolute position obtained by the CMOS is compared and analyzed. If the error is within a reasonable range, the code is determined. Normal; if the error range is exceeded, the coding error is considered, and the image information is re-read for correlation coding. If the new code value is equal to one of the previous analysis data, the code value of the re-encoding is considered correct, and vice versa. Fault alarm information.

The working principle of the invention is as follows: the incremental scale grating is arranged in parallel and equidistantly depicting the landmark absolute reference point position mark, which is composed of several grid lines. There are many ways to encode, such as binary and decimal. Taking binary as an example, 16 gate lines, the grid lines at the left and right end faces always depict the opaque grating, as the code boundary mark, the middle 14 grids

10

Replacement page (Article 26) In the line position, each grid line bit corresponds to a unique number 0 or 1, which can form more than 10,000 sets of different digital codes. For example, the adjacent two milestones have a spacing of 1 mm, and the codeable range will exceed 10 m. There are three openings on the indicating diaphragm, and the upper left one can transmit light, and the indicating grating is placed, and the moire fringe signal formed by the grating with the scale grating can be received by the photoelectric receiver. An equal-width aperture opening is formed on the right side, and a CMOS photosensitive element is embedded on the upper and lower sides, the upper side CMOS is used to collect the incremental scale grid image information, and the lower side CMOS is used to identify the landmark absolute position mark, which is detected by the lower side CMOS. The milestone absolute position code is the first code segment, and the number of the dark line stripes obtained by the upper CMOS is coded as the second code segment. The two-phase is the micro-magnification 10 times magnification between the I grid lines. The number of pixels to be inserted is encoded as the A most encoded segment. Let the distance between two adjacent milestones be 2mm, and the spacing of the scale grid lines be ^ = 10#«»,

The CMOS pixel pitch is = «n, then the absolute position ^ can be obtained by the following formula:

Β Χ σ C

Μ _χ = Ν _χ X d + Κ X δ + + X σ

χ ^χ 10 1280 Since the C code value in the third code segment represents this resolution level, it cannot rise to the accuracy level, so the final absolute position code will consist of κ and three code segments. Each time the indicator diaphragm is moved to a position, the CMOS on the upper and lower sides of the aperture will obtain the encoded information of K, >5, and the current absolute position information can be obtained by calculation and decoding. Since the traditional incremental coding mode is retained, the coded information obtained by the image can be compared with the traditional incremental coded information. If the error is within the allowable range, the output is smooth, otherwise the sample is compared again, and if it still does not match, the output is output. accident details.

11

Replacement page (Article 26)

Claims

Claim

A monorail absolute grating characterized by comprising a light source (1), a mirror (2), a milestone flag (3), an incremental scale grid (4), a glass substrate (5), an upper CMOS a sensor (6), a lower CMOS sensor (7), a moving aperture (8), a photoreceiver (9), an indicating grating (10), wherein the light source (1) and the mirror (2) are combined to form an illumination light path, Parallel light of a certain intensity, the glass substrate (5) is depicted with an equal-width, equidistant incremental scale grid line (4), and the glass substrate (5) is on the incremental scale grid line

The bottom of (4) is marked with a parallel equidistant landmark mark (3), the upper left opening of the moving aperture (8), the opening is embedded with the indicator grating (10), and the right side of the moving aperture (8) is symmetrically open. The symmetrical opening respectively embeds an upper CMOS sensor (6) and a lower CMOS sensor (7) for acquiring image information, and indicates that the grating (10) is mounted close to the glass substrate (5), and the upper CMOS sensor (6) The mounting position is aligned with the incremental scale grid line (4), and the mounting position of the lower CMOS sensor (7) is aligned with the milestone flag (3), the light source (1), the moving diaphragm (8), and the photoreceiver (9). The relative position is fixedly mounted on the movable ruler (21), and the movable ruler (21) can move back and forth with respect to the glass substrate (5), the light source

(1), moving diaphragm (8) and photoreceiver (9) can move in parallel at the same time, the incremental scale grid line (4) and the light indicating the grating (10) form moire fringes projected on the photoreceiver (9) .

2. A monorail absolute scale according to claim 1, characterized in that said light source (1) is a blue light source.

3. The monorail absolute scale according to claim 1, wherein the line of the milestone mark (3) is composed of a plurality of equally spaced gate lines, and the lower position is from the zero point.

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Replacement page (Article 26) As a result, an absolute position mark is set at a certain distance to be the milestone flag (3), and the milestone flag (3) is divided into a milestone code boundary flag line (12) for marking the appearance and end of the milestone for encoding. , expanding its number of bits, that is, the effective coded bits (11) in the milestone stripe group that can expand the range of the code; the effective coded gate line (13) for determining whether to mark the specific position of the gate line, and the gate line is represented as 0, not to draw the grid line and leave white, here is represented as 1, the spacing of the adjacent milestone flag (3) is ^

4. The monorail absolute scale according to claim 3, wherein the effective coded gate line (13) has a total of 16 strips, and the end lines at both ends are used as boundary points to always depict the gate line, and the lower side CMOS sensor (7) I found that both ends passed and I knew I could read the complete milestone shadow pattern.

5. An image encoding method for applying a monorail absolute scale according to claim 1, wherein said milestone flag (3) is composed of a plurality of equal width gate lines, which exhibit a binary code to become a first coded barcode. The parallel light provided by the illumination light path formed by the combination of the light source (1) and the mirror (2) constitutes the second coding area by the shadow line stripes generated by the incremental scale grid line (4), exceeding the milestone flag (3) coding window The image of the grid line stripe after the last milestone flag (3) is digitally acquired by the CMOS sensor, and the binary digital code is obtained to form the second coded barcode. The last two grid lines are less than one step. The quantity is encoded by CMOS pixel insertion. This is the third code segment, and the three-segment code is combined to obtain a valid position code. The position code corresponds to an absolute position on the scale, in other words, on the scale. Any absolute position has an absolute code consisting of three segments, as long as a reliable indicator is obtained. The absolute encoding of the starting position, you can get the absolute distance of the stroke by the difference.

6. The image encoding method according to claim 5, wherein said lower side

13

Replacement page (Article 26) The CMOS sensor (7) directly acquires the image coding information of the milestone flag bit (3), and the coded value is the first absolute position code segment, that is, the absolute position corresponding to the milestone flag bit (3) is

M _x ' = N _x xd

The upper CMOS sensor (6) directly captures the image of the incremental scale grid (4) and encodes it as follows: When the milestone flag (3) stripe group appears completely on the monitor array of the lower CMOS sensor (7), The stripe of the corresponding incremental scale grid (4) also appears instantaneously on the array of upper CMOS sensors (6), which will be locked by the upper CMOS sensor (6), exceeding the milestone flag (3) stripe The set of ruler grid lines will be saved and encoded in the form of an image. From the image, the number of gate lines can be quickly identified as A. The scale line spacing is δ, then the precise incremental distance beyond the absolute position mark is Obtained by the number of dark lines in the incremental grid diagram, as follows:

L = K 6 , this is the second code segment;

When the left end line of the indicating pupil shading area (19) is between the adjacent grid lines of the incremental scale grating (4), the margin displacement is less than the spacing between one scale grid lines (15), and the margin between the scale lines is set. (16) For, L, the measurement accuracy of this displacement will directly affect the global measurement accuracy and the objectivity of absolute coding, due to the presence of CMOS pixels (14) with left and right CMOS pixel spacing (18), CMOS pixel size (17) is also getting smaller and smaller, the coding of the measurement margin (16) between the scale grid lines is the third section absolute coding; the spacing between the above-mentioned scale grid lines (15) is between the two adjacent grid lines of the indicator scale grating Straight line distance, the measurement margin between the scale grid lines (16) refers to the left side of the light-shielding area (19)

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Replacement page (Article 26) The linear distance from the end line to the leftmost point of the milestone, the CMOS cell size (17) refers to the width of the CMOS cell, and the CMOS cell pitch (18) refers to the linear distance between two adjacent CMOS cells, indicating the pupil shading area. (19) refers to the area indicating the opaque light, that is, the non-opening area, which indicates that the measurement end area is exceeded. The measurement margin between the CMOS pixels (20) refers to the left end line of the light-shielding area (19). The linear distance from the nearest CMOS pixel to the left end; the third segment of absolute coding is divided into two parts, that is, the measurement margin between the scale grid lines (16) is inserted into the integer CMOS pixel (14) and the numerical code is A. Part of the encoding; the traveling subdivision value of the CMOS inter-pixel measurement margin (20) encodes C, which expands the encoding to the resolution level, and the encoding of the inter-gate inter-line measurement margin (16) is expressed by the following formula:

B Χ σ C

\L + X σ

10 1280

The final absolute position coding consists of three parts: the coding of the milestone flag (3), the gate line coding of the incremental scale grating (4), the coding of the measurement margin between the scales (16), due to the measurement between the scales of the scale The remainder of the (16) subdivision position coding is only the resolution level, so only the part is saved, and the three sections are encoded and decoded to obtain any absolute position.

Β X σ

Μ _χ = Ν _χ X d + Κ XS + _{ιο The} above-mentioned moire fringes generated by the grating (10) are compared as the low-precision coding and the absolute position obtained by the CMOS. If the error is within a reasonable range, the code is determined to be normal. If the error range is exceeded, the coding error is considered, and the image information is re-read for correlation.

15

Replacement page (Article 26) The coding comparison, if the new code value is equal to one of the previous analysis data, it is considered that the re-encoded code value is correct, and vice versa, the grating rule fault alarm information is output.

7. The image encoding method according to claim 6, wherein said milestone flag bit (3) is composed of 14 equal-width gate line bits, which exhibit binary code, and 14 gate lines can be composed from 0-6383. digital.

8. The image encoding method according to claim 6, wherein the spacing (15) between the last scale lines is averaged by a factor of 10 using a projection micro-amplification technique, and an average of 100 pixel units are distributed within the distance. The distance between the scales of the scale grids (15) is equally divided into 100 parts, that is, the measurement accuracy is ο· ¹ , that is, one tenth of the CMOS pixel pitch (18).

9. The image encoding method according to claim 8, wherein said scale inter-wire measurement margin (16) is accurately quantized according to the accuracy of said one-tenth CMOS pixel pitch (18), and said indicating aperture The distance traveled between the pixels on the left end line of the shading area (19), that is, the measurement margin between the CMOS pixels (20) is electronically subdivided into 128 copies.

σ

The resolution is within.

10. The image encoding method according to claim 6, wherein said upper CMOS sensor (6) is aligned with the incremental scale gate line (4), and the lower CMOS sensor (7) is aligned with the milestone flag (3). When moving at high speed, use the landmark mark (3) to locate, reduce the amount of data collected by the image, and increase the speed of the linear motion. When the target of the motion is near, decelerate the acquisition and analysis of the coding information of the incremental scale grid (4).

16 - Replacement page (Article 26)