An anti-stain measurement method for a quasi-absolute photoelectric encoder

Abstract

An anti-stain measurement method for a quasi-absolute photoelectric encoder relates to the technical field of photoelectric encoders, and solves the problem that the existing anti-stain methods have strict requirements for sealing and use environments, and once the code disk is contaminated, the encoder will not be able to be used. The method includes: the first measurement probe, the second measurement probe, and the third measurement probe perform angle measurement to obtain the measured angle, and send the measured angle to the general processor; the three measurement probes, namely the first measurement probe, the second measurement probe, and the third measurement probe, work independently of each other, and each measurement probe can complete angle measurement to obtain the measured angle; the general processor obtains the fused angle value according to the measured angles of at least two measurement probes that have not passed through the contaminated code disk area. The present invention does not need to reinforce the sealing of its code disk, greatly reduces the requirements for the use environment, improves the environmental adaptability, and improves the measurement accuracy and reliability of the encoder.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic encoders, and particularly to a stain-resistant measurement method for a quasi-absolute optoelectronic encoder. Background Art

[0002] An optoelectronic encoder, also known as an optoelectronic angular position sensor, is a digital angle measuring device integrating optics, mechanics, and electronics, and is a displacement sensor that converts physical quantities such as rotational angular position, angular displacement, and angular velocity into electrical signals. Classified by the measurement principle, optoelectronic encoders can be divided into: image type and Moiré fringe type; classified by the coding method, they can be divided into: absolute type, incremental type, and quasi-absolute type.

[0003] On the basis of an incremental optoelectronic encoder, a quasi-absolute optoelectronic encoder adds multiple reference points to the zero-position coding ring. While inheriting the advantages of the incremental optoelectronic encoder such as simple coding method, stable and reliable operation, and fast response speed, it also has the advantage of high efficiency in finding the absolute position, that is, it can find the absolute position by rotating only a small angle. During use, due to reasons such as the environment and poor sealing, the code disk of the quasi-absolute optoelectronic encoder is easily contaminated, resulting in jump codes in the output angle data. Currently, the main solutions are to strengthen the sealing and maintain the cleanliness of the use environment. However, it is impossible to completely seal the optoelectronic encoder. Even if it is completely sealed, there will be sealing leaks due to use and other reasons, and the use environment is more uncontrollable. Stains in the environment during use are extremely likely to contaminate the code disk, resulting in incorrect output angles of the encoder and jump code phenomena, making the quasi-absolute optoelectronic encoder unusable.

[0004] For the Moiré fringe quasi-absolute optoelectronic encoder among them, its stain-resistant method is also only the above-mentioned strengthening of sealing and maintaining the cleanliness of the use environment, and no improvement has been proposed in the measurement method so far. Based on this, a stain-resistant measurement method for the Moiré fringe quasi-absolute optoelectronic encoder is developed. Summary of the Invention

[0005] In view of the above problems, the present invention provides a stain-resistant measurement method for a quasi-absolute optoelectronic encoder to solve the disadvantages of the existing stain-resistant methods that have strict requirements for sealing and use environment and the encoder will be unusable once the code disk is contaminated.

[0006] The technical solution adopted by the present invention to solve the technical problems is as follows:

[0007] A stain-resistant measurement method for a quasi-absolute optoelectronic encoder includes the following steps:

[0008] The first measurement probe, the second measurement probe, and the third measurement probe perform angle measurement to obtain a measured angle, and send the measured angle to the general processor; the three measurement probes, namely the first measurement probe, the second measurement probe, and the third measurement probe, work independently of each other, and each measurement probe can complete angle measurement to obtain a measured angle;

[0009] The general processor obtains a fused angle value based on the measured angles of at least two measurement probes of the non-contaminated code disk areas.

[0010] A quasi-absolute optical encoder adopting the anti-stain measurement method of the quasi-absolute optical encoder described above, the optical encoder includes a code disk, a first measurement probe, a second measurement probe, a third measurement probe, and a general processor, the code disk includes a reference coding ring for determining the absolute position and a fine code coding ring for obtaining the Moiré fringe signal, the first measurement probe, the second measurement probe, and the third measurement probe are arranged corresponding to the code disk and are all connected to the general processor.

[0011] The beneficial effects of the present invention are:

[0012] The anti-stain measurement method of the quasi-absolute optical encoder of the present invention simultaneously measures the code disk information through three measurement probes, and the general processor then obtains a fused angle value based on the measured angles of at least two measurement probes of the non-contaminated code disk areas. The method of using three measurement probes replaces the traditional method relying on the encoder sealing technology. When the quasi-absolute optical encoder works, it is not necessary to reinforce the sealing of its code disk, which greatly reduces the requirements for the use environment and improves the environmental adaptability; by fusing the measurement angle data of two or three measurement probes, the measurement accuracy of the quasi-absolute optical encoder can also be improved, and the reliability of the quasi-absolute optical encoder is enhanced.

[0013] The optical encoder of the present invention has a simple mechanism, does not require a sealing structure, has a simple manufacturing process, and has high angle measurement accuracy. Description of the Drawings

[0014] Figure 1 It is a schematic structural diagram of the optical encoder of the anti-stain measurement method of the quasi-absolute optical encoder of the present invention.

[0015] Figure 2 It is a schematic structural diagram of the code disk of the anti-stain measurement method of the quasi-absolute optical encoder of the present invention.

[0016] Figure 3 It is a flow chart for determining the absolute position of the anti-stain measurement method of the quasi-absolute optical encoder of the present invention.

[0017] Figure 4 It is a schematic diagram of the phase difference of the anti-stain measurement method of the quasi-absolute optical encoder of the present invention.

[0018] Figure 5 This is a flowchart of a stain-resistant measurement method for a quasi-absolute optical encoder of the present invention. Detailed implementation manners

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] A stain-resistant measurement method for a quasi-absolute optical encoder includes the following steps:

[0021] Step 1: The first measurement probe, the second measurement probe, and the third measurement probe perform angle measurement to obtain the measured angle, and send the measured angle to the general processor; the three measurement probes, namely the first measurement probe, the second measurement probe, and the third measurement probe, work independently of each other, and each measurement probe can complete angle measurement to obtain the measured angle.

[0022] Step 2: The general processor obtains the fused angle value based on the measured angles of at least two measurement probes in the non-contaminated code disk areas.

[0023] The optical encoder includes a code disk, three measurement probes, and a general processor. A reference coding ring and a fine code coding ring are provided on the code disk. The measurement probes are arranged corresponding to the code disk. The measurement probes work independently of each other. Each measurement probe can independently complete angle measurement to obtain the measured angle, and is connected to the general processor, and can send the measured angle to the general processor. The optical encoder based on this is a Moiré fringe type quasi-absolute optical encoder, which has three measurement probes, called the first measurement probe, the second measurement probe, and the third measurement probe. The measurement probes work independently of each other, and each measurement probe can independently complete angle measurement. In this embodiment, the first measurement probe, the second measurement probe, and the third measurement probe have the same structure. Each measurement probe is composed of a light-emitting diode, a receiving diode, and a processing circuit. The light emitted by the light-emitting diode forms Moiré fringes after passing through the code disk and the slit. The receiving diode converts the Moiré fringes into electrical signals, and the processing circuit converts the electrical signals into angles. The processing circuit includes a shaping amplifier and a microprocessor (ARM, DSP, and FPGA), etc. The Moiré fringes enter the microprocessor after being shaped and amplified. The microprocessor can complete coarse code counting, fine code subdivision, and the combination of fine and coarse correction to obtain the measured angle and complete angle measurement. The general processor is connected to the processing circuits of each measurement probe, and each processing circuit sends the obtained measured angle to the general processor. The general processor can obtain the fused angle value based on the measured angles of at least two measurement probes in the non-contaminated code disk areas. The processing circuits of the three measurement probes can be integrated on the same circuit board, or the general processor and the processing circuits of the three measurement probes can be integrated on the same circuit board.

[0024] When the code disk is stationary, rotating the measurement probe clockwise (i.e., the first measurement probe, the second measurement probe, or the third measurement probe) will increase the angle value measured by the measurement probe, and rotating the measurement probe counterclockwise will decrease the angle value measured by the measurement probe. The first measurement probe, the second measurement probe, and the third measurement probe are arranged in sequence counterclockwise. The first measurement probe and the second measurement probe are separated by an angle α counterclockwise, and the third measurement probe and the first measurement probe are separated by an angle β counterclockwise. That is, the second measurement probe coincides with the first probe after rotating counterclockwise by an angle α, and the third measurement probe coincides with the first probe after rotating counterclockwise by an angle β. Let the angles measured by the three measurement probes be Angle 1 , Angle 2 , Angle 3 . The fused angle value Angle is:

[0025]

[0026] γ 1 , γ 2 , and γ 3 at most one of them is equal to 0

[0027]

[0028] In this embodiment, the three measurement probes are evenly arranged, that is, a measurement probe is placed at a position 120° apart above the code disk. That is, the second measurement probe is 240° different from the first measurement probe in the counterclockwise direction, and the third measurement probe is 120° different from the first measurement probe in the counterclockwise direction, as Figure 1 shown. If none of the three measurement probes pass through the contaminated code disk area, the final angle Angle is calculated as follows:

[0029]

[0030] The meaning of the formula is that Angle 2 , Angle 3 is rotated to Angle 1 , and then the average value of the three angles is taken as the final result Angle of the optical encoder.

[0031] If exactly one measurement probe passes through the contaminated area of the code disk (i.e., the contaminated code disk area), the measured angle obtained by it will be incorrect and needs to be discarded. The average value of the measured angles of the other two measurement probes is taken as Angle. For example, assume that the third measurement probe passes through the contaminated area of the code disk, then Angle 3 needs to be discarded. Therefore, Angle is the angle fusion of the first measurement probe and the second measurement probe, as shown in the following formula:

[0032]

[0033] If both two / three measurement probes pass through the contaminated area of the code disk and the contamination of the code disk is too serious, the photoelectric encoder of the present invention cannot obtain Angle.

[0034] As Figure 2 shown, it is a pattern design of the code disk of a commonly used quasi-absolute photoelectric encoder. The pattern of the photoelectric code disk is divided into two coding rings, namely a reference coding ring and a fine code coding ring. The outer ring is the fine code coding ring for generating Moiré fringes to obtain Moiré fringe signals. The measurement probe can collect fine code signals from the fine code coding ring, that is, the total processor can calculate the phase difference based on the fine code signals; the inner ring is the absolute position coding ring, also known as the reference coding ring, used to determine the absolute position. The reference coding ring is arranged in a certain pattern around the circumference of the code disk, and the fine code coding ring is evenly arranged. The general arrangement rule of the reference coding ring is as follows: Step 1, insert reference points into the code disk according to the number of evenly divided fine code lines m, and the number of them is n. The number of fine code lines between every two reference points is m / n, where both m and n are positive integers; Step 2, then insert n reference points between every two reference points obtained in Step 1 (at this time, there are a total of 2n reference points), and finally 2n reference points are obtained. The reference coding ring includes 2n reference points. The method of inserting all reference points is according to the following formula: The measurement probe can perform rough code counting on the reference coding ring, that is, find the absolute position based on the rough code counting.

[0035]

[0036] N i represents the number of fine code lines between the i-th reference point and the (i + 1)-th reference point, i = 1, 2, 3, 4,..., 2n - 1, N 2n represents the number of fine code lines between the 2n-th reference point and the 1st reference point. In the above formula, N 1 ~N 2n are arranged counterclockwise in sequence from the zero point, and the obtained code disk pattern is shown in Figure 2. One side of N 2n is N 2n-1 and the other side is N 1 . Select the gap between a certain two adjacent numbers of fine code lines as the above zero point.

[0037] However, for any setting rule of reference points, there are the following problems: The maximum number of fine code lines between two adjacent reference points in one circumference of the code disk is set to N 2n-1 , and the minimum number of fine code lines between adjacent reference points is set to N 2n ; then the size relationship among the three is: N 2n-1 >N 1 >N 2n . If N 2n-1 <N 1+N 2n , it is necessary to continuously pass through three reference points in the same direction to determine the absolute position; if N 2n-1 ≥N 1 +N 2n , it is necessary to continuously pass through four reference points in the same direction to determine the absolute position. And so on, the larger N 2n-1 is, the fewer the number of fine code lines between adjacent reference points, and the more reference points need to be passed through to determine the absolute position. In order to improve the zero seeking efficiency of the quasi-absolute type, when designing the corresponding code disk pattern of the present invention, the reference point setting rule is designed so that it is necessary to pass through four reference points to determine its absolute position. The method flow chart for determining the absolute position by passing through four reference points is as Figure 3 shown. When N 1 ~N 2n any area reference point coding ring is contaminated, or any several area reference point coding rings are contaminated, as long as the remaining three consecutive areas (i.e., 4 reference points) are not contaminated, the absolute position can be obtained. After completing the absolute position recognition, except for the case where the fine code coding ring is contaminated, the reference coding ring recognition is no longer performed. The present invention can eliminate the output angle error caused by the contamination of the reference coding ring.

[0038] After the three groups of probes are installed, the phase difference between them is fixed. The fine code phase differences measured by the three groups of measurement probes are as Figure 4 shown. The phase of the first measurement probe is A, the phase of the second measurement probe is B, and the phase of the third measurement probe is C. The phase differences are shown in the following formula:

[0039]

[0040] |A - B| is the phase difference between the first measurement probe and the second measurement probe, |B - C| is the phase difference between the second measurement probe and the third measurement probe, |A - C| is the phase difference between the first measurement probe and the third measurement probe. The theoretical set value of the phase difference between the first measurement probe and the second measurement probe is Δθ 1 , the theoretical set value of the phase difference between the second measurement probe and the third measurement probe is Δθ 2 , the theoretical set value of the phase difference between the first measurement probe and the third measurement probe is Δθ 3 , Δθ 1 , Δθ 2 and Δθ 3 are all constants. If the code disk passed by any group of probes is contaminated, then two values in the phase difference are not equal to their corresponding theoretical set values. For example: if the first measurement probe passes through the contaminated code disk area, the phase difference formula becomes:

[0041]

[0042] Δθ 1 , Δθ2 and Δθ 3 These three theoretically set phase differences can be calculated using trigonometric function formulas as follows:

[0043]

[0044] where sinA and cosA are the sine and cosine signals measured by the first measurement probe, sinB and cosB are the sine and cosine signals measured by the second measurement probe, and sinC and cosC are the sine and cosine signals measured by the third measurement probe.

[0045] Each measurement probe determines its absolute position using four reference points, such as Figure 3 , and the method for determining the absolute position through the four reference points is as follows:

[0046] Step 0.1: Clear the coarse code count of the measurement probe (the coarse code count is to record the reference point).

[0047] Step 0.2: The measurement probe starts coarse code counting and determines whether it encounters a reference point. When it encounters a reference point (the first time it encounters a reference point), the coarse code count is cleared and coarse coding counting is restarted. When it encounters a reference point (the second time it encounters a reference point), the count of the coarse code counter is x 1 , the coarse code counter is cleared, and with x 1 as the address, according to the reference point pattern of the reference coding ring, the theoretical count value x 2 (or: with x 1 as the address, according to the reference point setting pattern of the reference coding ring, the theoretical count value x 2 when the coarse code counter is cleared and then encounters the next reference point is obtained), and then coarse coding counting is restarted. When it encounters a reference point (the third time it encounters a reference point), the count of the coarse code counter is x 3 , the measurement probe determines whether x 2 = x 3 holds. If it holds, proceed to step 0.3; if not, return to step 0.1, that is, re-execute step 0.1 and step 0.2.

[0048] Step 0.3: The measurement probe uses x 3 as the address, and according to the reference point setting pattern of the reference coding ring, obtains the theoretical count value x 4 when the coarse coding count of the measurement probe encounters the next reference point. The coarse code count of the measurement probe is cleared, and coarse coding counting is restarted. When it encounters a reference point (the fourth time it encounters a reference point), the count of the coarse code count of the measurement probe is x 5 , determines whether x 4 = x 5Whether it holds. If not, return to Step 0.1, that is, re-execute Step 0.1 and Step 0.2. If it holds, proceed to Step 0.4;

[0049] Step 0.4: The measuring probe determines the absolute position according to the reference points encountered in Step 0.2 and Step 0.3. The flowchart of the anti-stain measurement method of a quasi-absolute photoelectric encoder of the present invention is as Figure 5 shown,

[0050] Step 1: The first measuring probe, the second measuring probe, and the third measuring probe search for the absolute position through the reference coding ring, and search for the absolute position of each measuring probe according to the Figure 3 process. After all three measuring probes find the absolute position, proceed to Step 2.

[0051] Step 2: The three groups of measuring probes respectively collect the fine code signals, that is, the sine and cosine signals, and calculate the phase differences of the fine code signals of the three groups of measuring probes.

[0052] Step 3: Compare the calculated phase differences with the theoretically set phase difference values calculated according to formula (6), and determine γ 1 , γ 2 and γ 3 values according to the comparison results. It can be divided into three cases; in the first case, the phase differences between the three groups of measuring probes are all equal to the theoretically set phase difference values, then none of the three groups of measuring probes have passed through the contaminated code disk area, and the data are all valid, proceed to Step 4; in the second case, two of the phase differences between the three groups of measuring probes are not equal to the theory, and one is equal to the theory, then one of the three groups of measuring probes has passed through the contaminated code disk area, and the other two groups of measuring probes are working normally without passing through the contaminated area, and the data of the normally working measuring probes are all valid, proceed to Step 4; in the third case, the phase differences between the three groups of measuring probes are not equal to the theoretical values, then all three / two groups of measuring probes have passed through the contaminated code disk area, and the data of the three groups of measuring probes are all unavailable, and at the same time it also means that the contaminated code disk area of the code disk is too large and too much, then the code disk cannot be used, return to Step 1 to start over or stop the angle measurement.

[0053] Step 4: According to the γ n value obtained in Step 3, use formula (1) to calculate the angle measurement result Angle. After judgment in Step 3, calculate the measurement angles of the measuring probes that have not passed through the contaminated code disk area according to formula (1), and the angle measurement is completed.

[0054] An anti-stain measurement method for a quasi-absolute photoelectric encoder of the present invention measures the code disk information through three measurement probes. The general processor then obtains the fused angle value by using the measurement angles of at least two measurement probes in the non-contaminated code disk areas. The method of using three measurement probes replaces the traditional method relying on encoder sealing technology. When the quasi-absolute photoelectric encoder is working, there is no need to reinforce the sealing of its code disk, which greatly reduces the requirements for the use environment and improves the environmental adaptability. By fusing the measurement angle data of two or three measurement probes, the measurement accuracy of the quasi-absolute photoelectric encoder can also be improved, and the reliability of the quasi-absolute photoelectric encoder is enhanced. The photoelectric encoder of the present invention has a simple structure without a sealing structure, a simple manufacturing process, and a high angle measurement accuracy.

[0055] Specifically, the present invention measures the code disk information through three measurement probes simultaneously, then judges the probe passing through the code disk contamination area by using the phase relationship of the three measurement probes, discards the data of the probe passing through the code disk contamination area, and determines the absolute position of each probe by using multiple groups of reference points to avoid the error in absolute position recognition caused by the contamination of the reference point coding ring. From the perspective of pure electrical signal processing, the present invention uses the method of three measurement probes and multiple groups of reference points to replace the traditional method relying on encoder sealing technology. When the quasi-absolute photoelectric encoder is working, there is no need to reinforce the sealing of its code disk, and there is no need to worry about seal leakage. Only three measurement probes need to be installed in the structure. Such a design can greatly reduce the requirements for the use environment and improve the environmental adaptability.

Claims

1. An anti-stain measurement method for a quasi-absolute optical encoder, characterized in that, it includes the following steps: The first measurement probe, the second measurement probe, and the third measurement probe perform angle measurement to obtain the measured angle, and send the measured angle to the general processor; the three measurement probes of the first measurement probe, the second measurement probe, and the third measurement probe work independently of each other, and each measurement probe can complete angle measurement to obtain the measured angle; The general processor obtains the fused angle value according to the measured angles of at least two measurement probes in the non-contaminated code disk area; The first measurement probe, the second measurement probe, and the third measurement probe are arranged in sequence in the counterclockwise direction. The first measurement probe and the second measurement probe are separated by an angle α in the counterclockwise direction. The second measurement probe rotates counterclockwise by an angle α and coincides with the first probe. The third measurement probe and the first measurement probe are separated by an angle β in the counterclockwise direction. The third measurement probe rotates counterclockwise by an angle β and coincides with the first probe; the formula for the general processor to obtain the fused angle value according to the measured angle is: γ 1 , γ 2 and γ 3 At most one of them is equal to 0 Among them, Angle 1 is the measured angle obtained by the first measurement probe for angle measurement, Angle 2 is the measured angle obtained by the second measurement probe for angle measurement, Angle 3 is the measured angle obtained by the third measurement probe for angle measurement, and Angle is the fused angle value.

2. An anti-stain measurement method for a quasi-absolute optical encoder according to claim 1, characterized in that, The first measurement probe and the second measurement probe are separated by 120°, and the first measurement probe and the third measurement probe are separated by 120°.

3. An anti-stain measurement method for a quasi-absolute optical encoder according to claim 1, characterized in that, The specific process of the anti-stain measurement method is: Step1: The first measurement probe, the second measurement probe, and the third measurement probe all find the absolute position through the reference coding ring; Step2: The first measurement probe, the second measurement probe, and the third measurement probe respectively collect the fine code signals, and calculate the phase differences corresponding to each other between the fine code signals of the three measurement probes; Step 3. Calculate the phase difference obtained in Step 2 and compare it with the theoretically set value of the phase difference, and obtain γ according to the comparison result and formula (2). 1 , γ 2 and γ 3 values; Step4. Based on the γ n value obtained in Step3, calculate the fused angle value Angle using formula (1), and the angle measurement is completed.

4. An anti-stain measurement method for a quasi-absolute optical encoder according to claim 3, characterized in that, Step 3 is specifically as follows: Compare each phase difference obtained in Step 2 with the corresponding theoretically set value of the phase difference. If the comparison result shows that all three phase differences are equal to their corresponding theoretically set values of the phase differences, it means that none of the three groups of measurement probes have passed through the contaminated code disk area, that is, γ 1 , γ 2 and γ 3 are all 1, and proceed to Step 4; if the comparison result shows that only one of the three phase differences is equal to its corresponding theoretically set value of the phase difference, it means that the two measurement probes corresponding to this phase difference have not passed through the contaminated code disk area, while the other measurement probe has passed through the contaminated code disk area. Calculate the values of γ 1 , γ 2 and γ 3 according to formula (2), and proceed to Step 4; if the comparison result shows that all three phase differences are not equal to their corresponding theoretically set values of the phase differences, it means that all three groups of measurement probes have passed through the contaminated code disk area, that is, γ 1 , γ 2 and γ 3 are all 0, and return to Step 1 to restart or stop the angle measurement.

5. An anti-stain measurement method for a quasi-absolute optical encoder according to claim 3, characterized in that, In Step1, each measurement probe needs to use four reference points to determine the absolute position.

6. An anti-stain measurement method for a quasi-absolute optical encoder according to claim 5, characterized in that, The method for each measurement probe to use four reference points to determine the absolute position is: Step 0.1: Clear the coarse code count of the measurement probe; Step 0.2: The measurement probe starts coarse code counting for the reference coding ring and determines whether it encounters the reference point. When the reference point of the reference coding ring is encountered, the coarse code count is cleared; the coarse code counting is restarted. When the reference point is encountered, the count of the coarse code count of the measurement probe is x 1 , with x 1 as the address, according to the setting rule of the reference point of the reference coding ring, the theoretical count value x 2 when the coarse code count of the measurement probe encounters the next reference point is obtained. The coarse code count is cleared; the coarse code counting is restarted. When the reference point is encountered, the coarse code count of the measurement probe is x 3 , determine whether x 2 = x 3 holds. If it holds, proceed to Step 0.3; if not, return to Step 0.1 and restart Steps 0.1 and 0.2 Step 0.3: Using x 3 as the address, obtain the theoretical count value x of the coarse code count of the measurement probe when encountering the next reference point according to the reference point setting rule of the reference coding ring 4 , and clear the coarse code count; restart the coarse code count. When encountering the reference point, the coarse code count of the measurement probe is x 5 , and determine whether x 4 = x 5 holds. If it does not hold, return to Step 0.1, that is, restart Step 0.1 and Step 0.

2. If it holds, proceed to Step 0.4; Step 0.4: The measurement probe determines the absolute position according to the reference points encountered in Step 0.2 and Step 0.

3.

7. A quasi-absolute optical encoder using the anti-stain measurement method for a quasi-absolute optical encoder according to any one of claims 1 to 6, characterized in that, The optical encoder includes a code disk, a first measurement probe, a second measurement probe, a third measurement probe, and a general processor. The code disk includes a reference coding ring for determining the absolute position and a fine code coding ring for obtaining the Moiré fringe signal. The first measurement probe, the second measurement probe, and the third measurement probe are arranged corresponding to the code disk and are all connected to the general processor.

Images