Non-equal pitch angle grating coded disc and absolute photoelectric shaft angle encoder

Abstract

The invention provides a non-equal pitch angle grating coded disc and an absolute photoelectric shaft angle encoder. The non-equal pitch angle grating coded disc comprises a main grating with an equal pitch angle and a slit grating with a non-equal pitch angle. The slit grating is provided with a split-phase window, and the split-phase window comprises m reference grating lines and m gradient precise code grating lines arranged on the two sides of the reference grating lines. The reference grating grid lines are arranged at the positions of the middle bisectors of the Minger fringes which are spaced by each other when the Minger fringes are generated by the equal pitch angles; starting from the first reference grating grid line, the positions of the gradient fine code grating grid lines on the two sides of the reference grating grid line are sequentially adjusted, so that the grid lines, generating dark moire fringes, on the two adjacent sides of the reference grating grid line are progressively increased from the included angle of 0 degree in an arithmetic progression, and n times of gradient change is carried out to reach the target pitch angle. By designing the fine code arrangement mode of the slit grating, the photoelectric signals extracted from the generated moire fringes are closer to theoretical sine.

Description

Technical Field

[0001] The present invention relates to the technical field of encoders, and in particular to a non-uniform grating angle grating code disk and an absolute photoelectric shaft angle encoder. Background Art

[0002] A photoelectric encoder is a digital precision angle measurement device that integrates optics, mechatronics, and electronics. Using a high-precision metrological circular grating as an angular displacement reference, it integrates circular grating moiré fringe technology with photoelectric conversion technology to convert spatial angular displacement information into a digital code and output it in real time. Due to its high accuracy, high resolution, wide measurement range, reliability, long service life, and ease of maintenance, it is widely used in real-time control and dynamic measurement systems in aerospace, automatic control, radar, and other fields.

[0003] For traditional photoelectric encoders that utilize moiré fringe signals for measurement, extracting the sinusoidal quality of the original signal from the encoder is difficult to achieve. This requires a suitable light source divergence angle, grating pitch, and grating gap. Using a structure where one light-emitting diode illuminates and one phototransistor receives the signal, a pair of light-emitting diodes can only extract one signal. Since photoelectric encoders typically have over twenty signal channels, a large number of light-emitting devices are required, and each signal channel must have a correct phase relationship.

[0004] Simultaneously adjusting the phase of more than 20 signals is cumbersome and time-consuming. Furthermore, there are multiple issues with photoelectric signals being affected by multiple light sources, leading to unstable signals. Summary of the Invention

[0005] The purpose of the present invention is to provide a non-uniform grating angle grating code disk and an absolute photoelectric shaft encoder that can solve at least one of the above-mentioned technical problems. The specific solution is as follows:

[0006] According to a specific embodiment disclosed in the present invention, a first aspect of the present invention discloses a non-uniform grating angle grating code disk, comprising: a main grating with an equal grating angle and a slit grating with a non-uniform grating angle;

[0007] The slit grating has a phase-splitting window, wherein the phase-splitting window comprises: m reference grating lines and m gradient fine code grating lines arranged on both sides of the reference grating lines;

[0008] The reference grating lines are arranged at the midpoint of every other bright or dark moiré fringe when the moiré fringe is generated by the equal grating angle;

[0009] Starting with the first reference grating line, the positions of the gradient fine code grating lines on both sides of the reference grating line are adjusted in sequence, so that the grating lines on both sides of the adjacent reference grating line produce dark moiré fringes or bright moiré fringes, and the angle increases from 0° in an arithmetic progression, and gradually changes to the target grating pitch angle after multiple times.

[0010] Optionally, the number of gradients n is equal to the number m of the reference grating lines.

[0011] Optionally, the slit grating phase split window further includes: precision code grating lines with equal grating pitch angles located at both ends of the slit grating phase split window, and the number of the gradient precision code grating lines is at least half of the number of the precision code grating lines with equal grating pitch angles.

[0012] Optionally, the angles between the gradient fine code grating lines that generate dark moiré fringes or bright moiré fringes on adjacent sides of the reference grating lines and the reference grating lines are equal.

[0013] According to a specific embodiment disclosed in the present invention, a second aspect of the present invention discloses an absolute shaft angle photoelectric encoder, comprising:

[0014] The non-uniform grating angle grating code disk is used to generate moiré fringes;

[0015] Multiple receiving devices are arranged on one side of the non-uniform grating angle grating code disk to respectively detect the moiré fringes generated by each channel and output multi-channel precise code photoelectric signals;

[0016] A light source assembly is arranged on the other side of the non-uniform grating angle grating code disk, so that the illumination area of a beam of parallel light generated by the light source assembly covers the receiving area of the multiple receiving devices;

[0017] The signal processing circuit extracts the precise code photoelectric signals of the multiple receiving devices.

[0018] Optionally, the light source assembly includes: an infrared point light source and a beam shaping mirror, wherein the beam shaping mirror is a spherical lens or an aspherical lens;

[0019] The infrared point light source and the beam shaping mirror satisfy the matching relationship:

[0020] R=tanθ×f

[0021] Wherein, R is the radius of the beam shaping mirror, and f is the focal length of the beam shaping mirror;

[0022] θ is the half divergence angle of the infrared point light source.

[0023] Optionally, the lens is an aspheric lens, and the image plane relationship satisfies: BFL@587.6nm is 15.19mm.

[0024] Optionally, the grating gap of the non-uniform grating angle grating code disk is ≥0.3 mm.

[0025] Optionally, the photoelectric signal contrast is greater than 3.

[0026] Compared with the prior art, the above solution of the embodiment disclosed in the present invention has at least the following beneficial effects:

[0027] The present invention forms moiré fringes by using a slit grating with a gradient pitch angle and a precise code arrangement, so that the sinusoidality of the photoelectric signal extracted from the moiré fringes is closer to the theoretical sine, and relaxes the strict restrictions on the light source divergence angle and grating gap in the design and adjustment stages.

[0028] By employing a one-to-many illumination scheme where one photoelectric transmitter corresponds to multiple receivers, strict phase matching of individual signals is no longer necessary during the alignment of the photoelectric encoder, improving alignment efficiency. Furthermore, the use of a non-uniformly spaced grating code disk allows for a larger grating gap and stronger photoelectric signal contrast. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are incorporated into and constitute a part of the specification, illustrating embodiments consistent with the present disclosure and, together with the specification, explaining the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort. In the drawings:

[0030] Figure 1 a is a schematic diagram of the distribution of grating lines at the phase-slit opening of a slit grating code disk with non-uniform grating pitch angle provided by an embodiment of the present invention;

[0031] Figure 1 b is Figure 1 a Partial enlarged view of both ends;

[0032] Figure 2 The waveform of the moiré fringe signal extracted from the equal-pitch grating code disk;

[0033] Figure 3 The Lissajous circle generated by the photoelectric signal measured by the unequal-pitch slit grating provided in the embodiment of the present invention;

[0034] Figure 4 A schematic structural diagram of an absolute shaft angle photoelectric encoder provided by an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of a conventional photoelectric light emitting device and a receiving device using a one-lighting-one-receiving arrangement;

[0036] Figure 6 A schematic diagram of a one-to-many arrangement of a photoelectric light emitting device and a receiving device provided in an embodiment of the present invention;

[0037] Figure 7 Photoelectric signal contrast diagram of Example 1 of the present invention;

[0038] Figure 8 This is a photoelectric signal contrast diagram of Example 2 of the present invention;

[0039] Figure 9 This is a comparison diagram of the static accuracy test diagram of Example 1 of the present invention;

[0040] Figure 10 This is a comparison chart of the dynamic accuracy test chart of Example 2 of the present invention.

[0041] Reference numerals:

[0042] 1-Infrared point light source; 2-Beam shaping mirror; 3-Non-uniform grating angle grating code disk; 4-Receiver device. DETAILED DESCRIPTION

[0043] To further clarify the objectives, technical solutions, and advantages of the present invention, a device for extracting photoelectric signals from an absolute encoder disclosed herein will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a portion of the embodiments disclosed herein, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments disclosed herein without inventive effort are intended to fall within the scope of protection disclosed herein.

[0044] The terms used in the examples of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms "a," "the," and "the" used in the examples of this application and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0045] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0046] It should be understood that although the terms first, second, third, etc. may be used to describe in the embodiments of the present application, these should not be limited to these terms. These terms are only used to distinguish. For example, without departing from the scope of the embodiments of the present application, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0047] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprising a" does not exclude the presence of other identical elements in the product or device comprising the element.

[0048] The following is combined with Figure 1-10 Alternative embodiments of the present invention are described in detail.

[0049] like Figure 1 As shown, according to a specific embodiment of the present invention, a first aspect of the present invention provides a non-uniform grating angle grating code disk, comprising: a main grating with an equal grating angle and a slit grating with a non-uniform grating angle.

[0050] The core indicators of photoelectric shaft encoder design include final resolution and accuracy. After the parameters such as the mechanical diameter of the encoder and the area of the receiver are known, the pitch angle and number of grating lines of the main grating and slit grating in the grating code disk can be initially set.

[0051] Specifically, the basic resolution and subdivision multiple are determined by the final resolution, the number of coarse code lines of the main grating is determined according to the basic resolution, and the pitch angle of the main grating can be calculated according to the number of coarse code lines. In this embodiment, the main grating has an equal pitch angle.

[0052] The slit grating fine code channel has four split phase windows with phase differences between them, and fine code lines are arranged in each split phase window. In this embodiment, the fine code lines in the split phase window can be divided into: reference grating lines, gradient fine code grating lines, and equidistant fine code grating lines with equal grating angles.

[0053] According to the principle of moiré fringe formation, the period of the slit grating should be equal to that of the main grating. Therefore, when designing a gradual change in the pitch angle of the slit grating, the pitch angle of two adjacent pairs of fine code lines is fixed, namely, the pitch angle of the main grating. After the pitch angle is determined, the number of fine code lines in the slit grating is further determined by the area of the receiver. In this embodiment, the two adjacent pairs of fine code lines refer to the fine code lines that produce two pairs of alternating light and dark moiré fringes.

[0054] Furthermore, after determining the number of fine code lines in each split-phase window, the positions of the reference grating lines are determined. All fine code lines can be selected as gradient fine code grating lines for gradient pitch design, or some fine code lines can be selected for gradient design to determine the gradient number n.

[0055] Specifically, to complete n-times of gradual change to a fixed target pitch angle, the positions of 2m fine code grating lines need to be adjusted. Therefore, m reference grating lines and 2m gradual change fine code grating lines are required.

[0056] In this embodiment, the reference grating lines are the midlines of every other moiré fringe produced when the grating pitch angle is equal. That is, the midlines of the nth, n+2th, n+4th, etc. moiré fringe are respectively used as the reference grating lines. Figure 1 In (b), positions a and b are the reference grating lines.

[0057] Taking the first reference grating line at position a as the adjustment reference, the gradient fine code grating lines on both sides of the reference grating line are changed sequentially so that the angle between the dark moiré fringes generated on the left side of position a and the dark moiré fringes generated on the right side of position a is 0°. Therefore, there is actually no reference grating line engraved at position a.

[0058] The positions of the gradient fine code grating lines that produce dark moiré fringes on the left and right sides of the second reference grating line at position b are then adjusted so that their included angle increases in an arithmetic progression until the included angle of the dark moiré fringes on the left and right sides of the mth reference grating line returns to the target pitch angle, which is the pitch angle of the main grating. At this point, the fine code pitch that produces the corresponding dark moiré fringes remains unchanged, and the fine code pitch that produces the dark moiré fringes increases in an arithmetic progression.

[0059] In other embodiments, the fine code grating lines that generate dark moiré fringes can be used as reference grating lines, and the fine code pitch corresponding to the bright moiré fringes can be adjusted to achieve the design of a non-uniform grating angle grating code disk.

[0060] Furthermore, in other embodiments, at least half or two-thirds of the fine code grating lines in the middle of the split phase window are selected for gradient pitch design. The fine code grating lines at both ends of the split phase window are retained at a fixed pitch angle consistent with the main grating, which plays a role in homogenization and improves the fitting effect.

[0061] The design method of the present invention is described below through an embodiment.

[0062] According to the design specifications, it is determined that 8192 coarse code grating lines are arranged on the entire circumference of the main grating, and the pitch angle of each coarse code grating line pair is 0.0439453125°.

[0063] Based on the receiver area, the slit grating draws 60 pairs of fine code lines corresponding to the fine code area, and the pitch angle of each fine code line pair is 0.0439453125°. Therefore, the angle between the two fine code lines that produce the dark moiré fringes, that is, the angle of the light-shielding portion, is 0.02197265625°.

[0064] If the non-uniform grating design is not performed, the waveform obtained by extracting the moiré fringe signal using a parallel light source will be an irregular waveform between a triangle wave and a sine wave. Figure 2 shown.

[0065] Figure 1 Figure a is a schematic diagram of the grid lines drawn when 60 pairs of fine code grid lines are drawn in the fine code area of this embodiment. The area where the 40 pairs of fine code grid lines in the middle area of the figure are located is a gradient area with non-uniform grid spacing, that is, the number of gradients is 20. Ten pairs of fine code grid lines with equal grid spacing angles are drawn at each end.

[0066] Specifically, such as Figure 1 As shown in b, the angle between the 11th and 12th black lines is 0° when they are combined. The angle between the 13th and 14th black lines becomes 0.0010986328125°. After 20 transformations, the angle between the 39th and 40th black lines is restored to 0.02197265625°.

[0067] Figure 3 As can be seen, because the use of a graduated grating pitch incorporates more diffraction, the quality of the original photoelectric signal obtained is higher, and the quality of the Lissajous circle, that is, the orthogonality and circularity, is higher, and the subsequent angular measurement accuracy after subdivision is higher. This relaxes the strict restrictions on the light source divergence angle and grating gap during the design and adjustment stages, which helps enhance photoelectric signal contrast and improve the accuracy of encoder photoelectric signal extraction.

[0068] Therefore, if Figure 4 As shown, the second aspect of the present invention provides an absolute photoelectric shaft encoder, comprising:

[0069] Non-uniform grating angle grating code disk 3, generating moiré fringes on multiple channels;

[0070] Multiple receiving devices 4 are arranged on one side of the non-uniform grating angle grating code disk 3 to detect the moiré fringes generated by each channel and output multi-channel precise code photoelectric signals;

[0071] A light source assembly is provided on the other side of the non-uniform grating angular grating code disk 3, so that the illumination area of a beam of parallel light generated by the light source assembly covers the receiving area of the plurality of receiving devices 4;

[0072] The signal processing circuit extracts the precise code photoelectric signals of the multiple receiving devices 4.

[0073] Traditional transmissive photoelectric encoders use a signal extraction method where each light-emitting diode (LED) receives a corresponding phototransistor, resulting in a pair of light-emitting diodes only capturing one signal. Whether for single-turn or multi-turn absolute encoders, recording a wide range of absolute positions typically requires at least ten channels, and the position of each LED must be rigorously calibrated to ensure signal phase relationships.

[0074] At the same time, due to the large divergence angle of a single infrared point light source, achieving high extraction accuracy requires, in addition to optical subdivision and interpolation to reduce the number of channels, a larger fine code pitch and a smaller gap between the slit grating and the main grating are required. However, a larger fine code pitch directly increases the diameter of the grating code disk, limiting the resolution by the physical dimensions of the code disk. A smaller gap is sensitive to code disk eccentricity and vibration, making it susceptible to failure due to wear and thermal deformation over long-term operation, and also prone to scratching between the main grating and the slit grating. Therefore, the absolute photoelectric shaft encoder in this embodiment relaxes the strict restrictions on the gap by using a non-uniformly pitched grating code disk 3. Furthermore, it employs a one-to-many illumination method, where one photoelectric transmitter corresponds to multiple receivers, simultaneously enhancing the contrast of the photoelectric signal. Furthermore, during calibration of the photoelectric shaft encoder, strict phase matching of the individual signals is not required, improving calibration efficiency.

[0075] Specifically, the light source assembly includes an infrared point light source 1 and a beam shaping mirror 2. The beam shaping mirror 2 shapes the light beam emitted by the infrared point light source 1 into a parallel light beam that can cover the receiving areas of multiple receiving devices 4.

[0076] Furthermore, for a rotating absolute grating code disk, a spherical mirror or an aspherical mirror can be used to generate a highly uniform circular light spot that can cover the slit grating phase window area.

[0077] When a spherical lens or an aspherical lens is selected, the infrared point light source 1 is set at the focus of the beam shaping lens 2, and the positional relationship with the lens is as follows:

[0078] R = tanθ × f.

[0079] Where R is the radius of the lens and f is the focal length of the lens;

[0080] θ is the half divergence angle of the infrared point light source.

[0081] By using a single infrared point light source in conjunction with a lens system, the present invention ensures optical path consistency across all channels, directly generating phase-aligned A / B signals. Furthermore, the use of a single infrared point light source avoids the signal instability that can occur when multiple light sources are used, leading to improved photoelectric signal contrast.

[0082] The light-emitting diode of a traditional photoelectric encoder has a large divergence angle. This large divergence angle requires a larger precision code pitch and a smaller grating gap. The following relationship exists between the photoelectric signal contrast and the grating gap:

[0083] t=nP 2 / λ.

[0084] Where t represents the photoelectric signal contrast, and P represents the grating pitch;

[0085] n is an integer and λ is the grating spacing.

[0086] Analysis of the above formula shows that the smaller the grating gap λ, the stronger the photoelectric signal contrast t. Although photoelectric signal contrast can be enhanced by reducing the grating gap, too small a grating gap increases the risk of mechanical interference between the main grating and the slit grating. On the other hand, an excessively large grating pitch, on the one hand, enhances the light diffraction effect, especially for high-density gratings, and reduces the photoelectric signal contrast. On the other hand, due to the mechanical size limitations of the grating disk, the number of grating lines in the precision code is reduced, reducing the moiré fringe contrast and affecting measurement accuracy.

[0087] Existing absolute photoelectric encoders typically have a grating gap range of 0.15-0.22mm, with an allowable eccentricity of ±5 to ±15μm, corresponding to an assembly difficulty level of 3-4. At the same time, the photoelectric signal contrast decreases as the gap increases. The best achievable photoelectric signal contrast within this grating gap range is 2.5.

[0088] By using the absolute photoelectric shaft angle encoder of this embodiment, the grating gap between the main grating and the slit grating can be increased to 0.3 mm, which not only reduces the assembly difficulty level, but also reduces the diameter of the grating code disk and increases the photoelectric signal contrast to greater than 3.

[0089] In one embodiment of the present invention, a point infrared light source with a wavelength of 890 nm and a divergence angle of 50° is selected for illumination. An aspherical lens is used as the beam shaper. At a wavelength of 587.6 nm, the back focal length of the aspherical lens is 15.19 mm from the receiving device, resulting in a BFL @ 587.6 nm of 15.19 mm. In other embodiments, a spherical lens can be used for beam shaping, producing a parallel beam with a circular spot that covers the grating code disk.

[0090] like Figure 5 As shown, the area enclosed by the red lines represents the illumination area on the grating code disk formed by the infrared point light source after being collimated by the aspheric lens. The multiple areas enclosed by the yellow lines represent the receiving areas of the individual receivers. The area of the red coil covers the entire area of the yellow areas. Within the area formed by the red coil, this embodiment has 12 receivers installed based on the specific arrangement of the fine code grating lines. The distance between the plane where the receivers are located and the slit grating is 0.5 mm.

[0091] Figure 6 To correspond to this embodiment, the prior art adopts a schematic diagram of a one-to-one setting of light-emitting receiving devices. The illumination area formed by each point light source on the light spot code disk should correspondingly cover the receiving area of each receiving device. Therefore, there are problems of difficulty in installation and adjustment and the mutual influence of multiple point light sources.

[0092] The absolute photoelectric shaft encoder of this embodiment was tested, and the results are as follows:

[0093] Figure 7-Figure 8 This is a test chart of the axial-angle photoelectric signal contrast obtained for a device with 12 receiving devices but at different grating intervals in this embodiment. The horizontal axis is the number of sampling points, and the vertical axis is the value of the photoelectric signal contrast.

[0094] Example 1

[0095] The grating gap is 0.30 mm and the photoelectric signal contrast is about 9.

[0096] Example 2

[0097] The grating gap is 0.35 mm and the photoelectric signal contrast is about 8.

[0098] Figure 9-10 The test diagrams of Examples 1 and 2 show that compared with the traditional photoelectric shaft angle encoder, this embodiment increases the overall accuracy of the system and improves the static accuracy and dynamic accuracy error values of the photoelectric shaft angle encoder. Figure 9 (b) 2.12″ is reduced to Figure 9 (a) is 0.75″, and the improvement is at least 1″, and the dynamic accuracy error value is from Figure 10 (a) 40 is reduced to Figure 10 (b) 10 code values.

[0099] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. References to the common and similar parts between the various embodiments will be sufficient. For the systems or devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, their descriptions are relatively simple; for relevant details, refer to the descriptions of the methods.

[0100] The above embodiments are only used to illustrate the technical solutions disclosed in the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments disclosed in the present invention.

Claims

1. A non-uniform grating angle grating code disk, characterized in that: include: Main grating with uniform grating pitch angle and slit grating with non-uniform grating pitch angle; The slit grating has a phase-splitting window, wherein the phase-splitting window comprises: m reference grating lines and m gradient fine code grating lines arranged on both sides of the reference grating lines; The reference grating lines are arranged at the midpoint of every other bright or dark moiré fringe when the moiré fringe is generated by the equal grating angle; Starting with the first reference grating line, the positions of the gradient fine code grating lines on both sides of the reference grating line are adjusted in sequence, so that the grating lines on both sides of the adjacent reference grating line produce dark moiré fringes or bright moiré fringes, and the angle increases from 0° in an arithmetic progression, and gradually changes to the target pitch angle after multiple times.

2. The non-uniform grating angle grating code disk according to claim 1, characterized in that: The number of gradients n is equal to the number m of the reference grating lines.

3. The non-uniform grating angle grating code disk according to claim 2, characterized in that: The slit grating phase split window also includes: precision code grating lines with equal grating pitch angles located at both ends of the slit grating phase split window, and the number of the gradient precision code grating lines is at least half of the number of the precision code grating lines with equal grating pitch angles.

4. The non-uniform grating angle grating code disk according to claim 2, wherein the gradient fine code grating lines that generate dark moiré fringes or bright moiré fringes on both sides of the reference grating lines have the same included angle with the reference grating lines.

5. An absolute photoelectric shaft encoder, characterized in that: include: The non-uniform angular grating code disk according to any one of claims 1 to 4, used to generate moiré fringes; Multiple receiving devices are arranged on one side of the non-uniform grating angle grating code disk to respectively detect the moiré fringes generated by each channel and output multi-channel precise code photoelectric signals; A light source assembly is arranged on the other side of the non-uniform grating angle grating code disk, so that the illumination area of a beam of parallel light generated by the light source assembly covers the receiving area of the multiple receiving devices; The signal processing circuit extracts the precise code photoelectric signals of the multiple receiving devices.

6. The absolute photoelectric shaft encoder according to claim 5, characterized in that: The light source assembly includes: an infrared point light source and a beam shaping lens, wherein the beam shaping lens is a spherical lens or an aspherical lens; The infrared point light source and the beam shaping mirror satisfy the matching relationship: R=tanθ×f Wherein, R is the radius of the beam shaping mirror, and f is the focal length of the beam shaping mirror; θ is the half divergence angle of the infrared point light source.

7. The absolute photoelectric shaft encoder according to claim 6, characterized in that: The lens is an aspheric lens, and the image plane relationship satisfies: BFL@587.6nm is 15.19mm.

8. The absolute photoelectric shaft encoder according to claim 5, characterized in that: The grating gap of the non-uniform grating angle grating code disk is ≥0.3 mm.

9. The absolute photoelectric shaft encoder according to claim 5, characterized in that: Photoelectric signal contrast>3.

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