Grating ruler displacement sensor based on oblique incidence light path

Abstract

This invention provides a grating ruler displacement sensor based on an oblique incidence optical path, relating to the field of optical measurement technology, to address to some extent the problem of excessively large readhead size hindering installation in small spaces. The grating ruler displacement sensor based on an oblique incidence optical path provided by this invention includes a readhead module and a grating ruler. The readhead module includes a housing, a PCB, and a light source. The top wall of the housing has a mounting plane for mounting the PCB, which is mounted on the mounting plane. The light source is integrated on the side of the PCB facing the top wall of the housing. A light-emitting aperture is formed on the top wall of the housing corresponding to the position of the light source, allowing light emitted from the light source to exit the housing. The mounting plane is obliquely positioned and forms an angle with the outer surface of the top wall of the housing. The grating ruler is parallel to the outer surface of the top wall of the housing. Using the structure provided in this application, the overall thickness of the readhead can be made very small, thus enabling easy installation in confined spaces such as micro-machine tools and precision displacement stages.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a grating ruler displacement sensor based on an oblique incident optical path. Background Technology

[0002] In advanced manufacturing, the miniaturization of high-precision grating ruler displacement sensors based on oblique incidence optical paths is increasingly urgent as position measurement feedback components. Existing grating ruler measuring devices employ digital cameras and optical lenses to acquire grating ruler fringes and measure displacement through changes in light intensity. However, the complex structure and large size of digital cameras and optical lenses result in an excessively large overall reader size, making them unsuitable for installation and use in confined spaces such as miniature machine tools and precision displacement stages.

[0003] Internationally advanced solutions are mostly based on the Talbot imaging principle. While this simplifies the optical structure to some extent, obtaining sufficient illumination area to ensure signal stability usually requires a large working distance or additional beam expanders. This still limits further reduction in readhead size and increases power consumption. Therefore, how to effectively reduce the readhead size while ensuring measurement accuracy, enabling flexible installation in confined spaces, has become a pressing technical problem. Summary of the Invention

[0004] The purpose of this invention is to provide a grating ruler displacement sensor based on an oblique incident optical path, so as to solve to some extent the problem that the large size of the read head is not conducive to small installation space.

[0005] This invention provides a grating ruler displacement sensor based on an oblique incidence optical path, comprising a read head module and a grating ruler; the read head module includes a housing, a PCB, and a light source, the top wall of the housing has a mounting plane for mounting the PCB, the PCB is mounted on the mounting plane, and the light source is integrated on the side of the PCB facing the top wall of the housing, the top wall of the housing has a light exit hole corresponding to the position of the light source, so that the light emitted by the light source exits the housing; the mounting plane is inclined and forms an angle with the outer surface of the top wall of the housing, and the grating ruler is arranged parallel to the outer surface of the top wall of the housing.

[0006] The reader module further includes a scanning plate, which is fixed inside the housing and located above the light source; a grating ruler is disposed outside the housing and located above the scanning plate, with the grating ruler and the scanning plate spaced apart, and the distance between the grating ruler and the scanning plate is the Talbot imaging distance.

[0007] Specifically, the read head module further includes a photodetector disposed on the PCB; a scanning slit is formed on the scanning plate, and the photosensitive surface of the photodetector is positioned facing the scanning slit.

[0008] Furthermore, the scanning plate is also provided with a light-transmitting hole, which faces the light-emitting surface of the light source.

[0009] Furthermore, the scanning slits on the scanning plate include four measurement scanning slits, which are arranged circumferentially on the scanning plate.

[0010] Furthermore, the photodetector includes four measurement photodetectors, which are arranged in a C-shape on the PCB and are respectively facing the four measurement scanning slits.

[0011] Furthermore, the center lines of the four measurement scanning slits are spaced nT+T / 4 apart along the scanning direction, where T is the fringe period of the grating ruler and n is a natural number.

[0012] The grating ruler includes an incremental grating region and a zero-position grating region; the scanning slit on the scanning plate also includes a zero-position scanning slit; the photodetector also includes a zero-position photodetector, which is directly opposite the zero-position scanning slit.

[0013] Specifically, the light-emitting aperture includes a clearance section and a light-emitting section. The diameter of the clearance section is larger than the diameter of the light-emitting section, and the diameter of the clearance section is not less than the maximum size of the scanning plate, and it can completely avoid the scanning plate.

[0014] Furthermore, the scanning plate is parallel to the mounting plane, and the angle between the mounting plane and the outer surface of the top wall is an acute angle.

[0015] Compared with existing technologies, the grating ruler displacement sensor based on oblique incident optical path provided by this invention has the following advantages: The present invention provides a grating ruler displacement sensor based on an oblique incident light path, including a read head module and a grating ruler; the read head module includes a housing, a PCB and a light source, the top wall of the housing is formed with a mounting plane for mounting the PCB, the PCB is mounted on the mounting plane, and the light source is integrated on the side of the PCB facing the top wall of the housing, the top wall of the housing is formed with a light outlet hole corresponding to the position of the light source, so that the light emitted by the light source can exit the housing; the mounting plane is set at an angle and is at an angle to the outer surface of the top wall of the housing, and the grating ruler is set parallel to the outer surface of the top wall of the housing.

[0016] Analysis shows that the cover provides a protective and mounting foundation for the entire read head module. The mounting plane for mounting the PCB is formed on the top wall inside the cover. The mounting plane provided in this application is not horizontal, but inclined and forms a preset angle with the outer surface of the top wall of the cover.

[0017] The PCB is fixed on the inclined mounting plane, and the light source is integrated on the side of the PCB facing the top wall of the enclosure. By opening a light hole in the top wall of the enclosure corresponding to the position of the light source, the light emitted by the light source can be emitted out of the enclosure.

[0018] The grating ruler is set parallel to the outer surface of the top wall of the enclosure, so that it can receive or receive light emitted from the light source.

[0019] Existing grating ruler displacement sensors based on oblique incidence optical paths typically require large working distances or additional beam expanders to achieve sufficient illumination area, resulting in excessively large readheads that are unsuitable for small-scale operating environments. This application employs an inclined mounting plane, tilting the PCB and light source at an angle relative to the grating ruler plane, thus achieving oblique incidence of the light source. The oblique incidence optical path extends the optical path compared to a vertical light-emitting structure. At the same readhead height, the actual optical path length between the light source and the grating ruler increases, allowing for a significant reduction in the physical working distance between the readhead and the grating ruler. Simultaneously, since the light emitted from the light source is divergent, oblique incidence significantly increases the projected area of ​​the beam on the grating ruler, achieving a large illumination area without any optical lenses or diffractive optical elements, thereby eliminating the need for beam expanders and directly reducing the readhead size.

[0020] Therefore, by adopting the structure provided in this application, the overall thickness of the read head can be made very small, so that it can be easily installed in narrow spaces such as micro machine tools and precision displacement stages. At the same time, since the beam expander lens is eliminated, the light energy loss is reduced and the power consumption of the sensor is reduced accordingly. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 A structural perspective view of the positional relationship between the grating ruler displacement sensor and the grating ruler based on an oblique incident optical path provided in an embodiment of the present invention; Figure 2 This is a perspective view of the overall structure of the grating ruler displacement sensor based on an oblique incident optical path provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the internal structure of the cover in the grating ruler displacement sensor based on an oblique incident optical path provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the scanning plate in the grating ruler displacement sensor based on an oblique incident optical path provided in an embodiment of the present invention; Figure 5 A schematic diagram of the light path after the light emitted by the light source in the grating ruler displacement sensor based on the oblique incident light path is projected onto the grating ruler and reflected, provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the grating ruler in the grating ruler displacement sensor based on the oblique incident optical path provided in an embodiment of the present invention.

[0023] In the diagram: 1-Cover; 101-Mounting plane; 102-Light emission aperture; 1021-Avoidance section; 1022-Light emission section; 2-PCB; 201-Driver circuit; 202-Amplifier circuit; 203-Interpolation subdivision circuit; 204-Shaping circuit; 3-Light source; 301-Emitted beam; 302-Incremental beam; 303-Zero beam; 4-Scanning plate; 401-Light passage aperture; 402-Measurement scanning slit; 403-Zero scanning slit; 5-Measurement photodetector; 6-Zero photodetector; 7-Grating ruler; 701-Zero grating area; 702-Incremental grating area. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0025] In the description of the embodiments of this application, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] As used herein, the term “and / or” includes any one of the relevant items listed and any combination of any two or more items.

[0029] For ease of description, spatial relation terms such as “above,” “upper,” “below,” and “lower” may be used herein to describe the relationship between one element and another as shown in the accompanying drawings. Such spatial relation terms are intended to include not only the orientation depicted in the drawings but also the different orientations of the device during use or operation.

[0030] The terminology used herein is for the purpose of describing various examples only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms “comprising,” “including,” and “having” enumerate the stated features, quantities, operations, components, elements, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0031] Variations in the shapes shown in the accompanying drawings may occur due to manufacturing techniques and / or tolerances. Therefore, the examples described herein are not limited to the specific shapes shown in the accompanying drawings, but include changes in shape that may occur during manufacturing.

[0032] The features of the examples described herein can be combined in various ways that will be apparent upon understanding the disclosure of this application. Furthermore, although the examples described herein have various constructions, other constructions are possible, as will be apparent upon understanding the disclosure of this application. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis that they can be implemented by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0033] like Figures 1-3 As shown, the present invention provides a grating ruler 7 displacement sensor, including a read head module and a grating ruler 7; the read head module includes a cover 1, a PCB 2 and a light source 3, the top wall inside the cover 1 forms a mounting plane 101 for mounting the PCB 2, the PCB 2 is mounted on the mounting plane 101, and the light source 3 is integrated on the side of the PCB 2 facing the top wall inside the cover 1, the top wall of the cover 1 forms a light outlet hole 102 corresponding to the position of the light source 3, so that the light emitted by the light source 3 can be emitted out of the cover 1; the mounting plane 101 is inclined and forms an angle with the outer surface of the top wall of the cover 1, and the grating ruler 7 is set parallel to the outer surface of the top wall of the cover 1.

[0034] Compared with existing technologies, the grating ruler 7 displacement sensor provided by this invention has the following advantages: The grating ruler 7 displacement sensor provided by the present invention can provide a protective foundation and mounting foundation for the entire reading head module through the cover 1. The mounting plane 101 for mounting PCB2 is formed in the top wall inside the cover 1. The mounting plane 101 provided in this application is not horizontal, but is inclined and forms a preset angle with the outer surface of the top wall of the cover 1.

[0035] PCB2 is fixed on the inclined mounting plane 101. The light source 3 is integrated on the side of PCB2 facing the inner top wall of the cover 1. By opening a light hole 102 on the top wall of the cover 1 corresponding to the position of the light source 3, the light emitted by the light source 3 can be emitted out of the cover 1.

[0036] The grating ruler 7 is set parallel to the outer surface of the top wall of the cover 1, so that it can receive or receive light emitted from the light source 3.

[0037] Existing grating ruler 7 displacement sensors typically require a large working distance or additional beam expanders to obtain sufficient illumination area, resulting in excessively large readheads that are unsuitable for small-scale operating environments. This application employs an inclined mounting plane 101, tilting the PCB2 and light source 3 at an angle relative to the grating ruler 7 plane, thus achieving oblique incidence of the light source 3. The oblique incidence optical path extends the optical path compared to a vertical light-emitting structure. At the same readhead height, the actual optical path length between the light source 3 and the grating ruler 7 increases, allowing for a significant reduction in the physical working distance between the readhead and the grating ruler 7. Simultaneously, since the light emitted by the light source 3 is divergent, oblique incidence significantly increases the projected area of ​​the beam on the grating ruler 7, achieving a large illumination area without any optical lenses or diffractive optical elements, thereby eliminating the need for beam expanders and directly reducing the readhead size.

[0038] Therefore, by adopting the structure provided in this application, the overall thickness of the read head can be made very small, so that it can be easily installed in narrow spaces such as micro machine tools and precision displacement stages. At the same time, since the beam expander lens is eliminated, the light energy loss is reduced and the power consumption of the sensor is reduced accordingly.

[0039] Optionally, such as Figure 1 As shown, the reader module also includes a scanning plate 4, which is fixed inside the housing 1 and located above the light source 3; a grating ruler 7 is set outside the housing 1 and located above the scanning plate 4, with the grating ruler 7 and the scanning plate 4 spaced apart, and the distance between the grating ruler 7 and the scanning plate 4 is the Talbot imaging distance.

[0040] The grating ruler 7 in this application is a reflective grating ruler 7. The Talbot effect for the reflective grating ruler 7 refers to the phenomenon where the grating self-images at a specific distance of reflection when illuminated by coherent light. This invention utilizes this principle to ensure that the Talbot image of the grating ruler 7 is precisely imaged on the scanning plate 4.

[0041] In practice, the scanning plate 4 is fixed inside the housing 1, maintaining a precise positioning relationship with the light source 3 and the photodetector. The distance from the grating ruler 7 to the scanning plate 4 is calculated and determined based on the grating period and the wavelength of the light source 3, ensuring that the plane on which the scanning plate 4 is located is precisely the imaging plane of the Taber image of the grating ruler 7.

[0042] This application sets up a scanning plate 4 and places the grating ruler 7 at the Talbot imaging distance, so that the grating ruler 7 forms a clear Talbot image on the scanning plate 4. When the grating ruler 7 and the read head are relatively displaced, the Talbot image also moves. The scanning slit on the scanning plate 4 performs spatial filtering on the moving Talbot image, thereby modulating the transmitted light intensity.

[0043] In practical applications, the optimal Tauber image contrast can be obtained by adjusting the distance between the grating ruler 7 and the scanning plate 4. Furthermore, by using the specially designed scanning plate 4, a complex optical imaging system is unnecessary; high-contrast displacement signal conversion can be achieved at close range solely through the Tauber effect, further simplifying the readhead structure and reducing its size and cost.

[0044] Optionally, such as Figure 1 Combination Figure 2 As shown, the read head module in this application also includes a photodetector, which is disposed on PCB2; a scanning slit is formed on the scanning plate 4, and the photosensitive surface of the photodetector is disposed facing the scanning slit.

[0045] In this application, the scanning slit is located on the scanning plate 4, and the photodetector is below the scanning plate 4. The light passing through the scanning slit directly illuminates the photosensitive surface of the photodetector, thereby converting the light intensity distribution of the Taber image on the scanning plate 4 into a measurable electrical signal.

[0046] By setting up photodetectors that correspond one-to-one with the scanning slits, when the image moves with the grating ruler 7, the scanning slits at different positions will transmit light of different phase intensities, and the photodetectors will generate photocurrents after receiving the light.

[0047] The scanning plate 4 in this application is made of an opaque material, and the scanning slit is a light-transmitting slit formed by etching or photolithography. Since the photodetector and the light source 3 in this application are jointly mounted on the same tilted PCB2, and all optical components maintain the same tilt reference, the assembly process can be simplified to a certain extent, and the consistency of the optical path can be guaranteed.

[0048] It should be noted that, in order to drive the light source 3 and process the weak electrical signal output by the photodetector, the read head module is also equipped with a signal processing circuit. These circuits are also integrated on PCB2, including a drive circuit, an amplifier circuit 202, a shaping circuit 204, and an interpolation subdivision circuit 203.

[0049] The driving circuit is electrically connected to the light source 3 to provide a stable current or voltage drive for the light source 3, ensuring that the light source 3 emits a beam of light with a constant intensity. The input terminal of the amplifier circuit 202 is electrically connected to the output terminal of the photodetector to convert the weak photocurrent signal generated by the photodetector into a voltage signal and amplify it so that its amplitude reaches a level that can be processed by subsequent circuits.

[0050] The input of the shaping circuit 204 is connected to the output of the amplifier circuit 202. It is used to filter, compare, and shape the amplified voltage signal to eliminate noise and waveform distortion, converting the analog signal into a digital pulse signal with clear edges. The input of the interpolation subdivision circuit 203 is connected to the output of the shaping circuit 204. It is used to perform differential, counting, and interpolation subdivision processing on four orthogonal signals with a 90° phase difference, thereby subdividing one cycle of the grating ruler 7 into thousands or even tens of thousands of parts, realizing high-resolution displacement measurement, and simultaneously outputting A and B phase orthogonal square wave signals to determine the direction of movement.

[0051] Optionally, such as Figure 1 Combination Figure 2 and Figure 4 As shown, the scanned version 4 in this application also has a light-transmitting hole 401, which faces the light-emitting surface of the light source 3.

[0052] The light-transmitting aperture 401 is an opening on the scanning plate 4, positioned aligned with the center of the light source 3, allowing the light beam emitted from the light source 3 to pass through the scanning plate 4 without obstruction and reach the grating ruler 7. In the actual structure, the scanning plate 4 is usually located directly above the light source 3. Therefore, a light-transmitting aperture 401 is formed on the scanning plate 4 at a position corresponding to the light-emitting surface of the light source 3. Preferably, the aperture of the light-transmitting aperture 401 in this application is slightly larger than the light-emitting area of ​​the light source 3, thereby ensuring that all emitted light can pass through and avoiding the problem of the scanning plate 4 itself blocking the light source 3.

[0053] Optionally, such as Figures 4-6 As shown, the scanning slits on the scanning plate 4 in this application include four measurement scanning slits 402, which are arranged circumferentially on the scanning plate 4.

[0054] Because the light path of this invention is obliquely incident, the Tiber image generated by the grating ruler 7 is no longer arranged in a straight line as in vertical incident light, but rather in a circular arrangement. Specifically, under oblique incident conditions, the Tiber image fringes will be distributed in a concentric arc around the light emission center line of the light source 3.

[0055] In order to match this circularly arranged Tiber image, the scanning slits are no longer arranged equidistantly along a straight line, but are arranged one-to-one in correspondence along the circumference of the Tiber image. Therefore, by using the scanning plate 4 provided in this application and the four measurement scanning slits 402 formed on the scanning plate 4, the problem that conventionally linearly arranged scanning slits cannot adapt to the obliquely incident circular Tiber image, resulting in reduced signal contrast and increased subdivision error, can be solved.

[0056] Furthermore, by designing the four measurement scanning slits 402 to be arranged in a circular pattern, each slit corresponds exactly to the fringe region of a specific phase in the Timber image, thereby maximizing the extraction of displacement information. This significantly improves the contrast of the displacement detection signal, reduces subdivision error, and enhances the measurement accuracy and stability of the sensor.

[0057] Optionally, such as Figures 1-6 As shown, the photodetector in this application includes four measurement photodetectors 5, which are arranged in a C-shape on the PCB2 and are respectively facing the four measurement scanning slits 402.

[0058] Since the measurement scanning slits 402 on the scanning plate 4 are arranged in a circle, the corresponding photodetectors also need to be aligned with them one by one in space. That is, the present invention arranges the four measurement photodetectors 5 in a C-shape on the PCB2 so that they are located in relatively uniform positions in the Gaussian light intensity distribution. At the same time, the scanning slits are also arranged in a C-shape accordingly, which can compensate for the non-uniformity of the illumination surface caused by oblique incidence and make the amplitude of the four signals tend to be consistent.

[0059] By arranging the four detectors in a C-shape, they are positioned in a region of relatively gradual change in Gaussian light intensity distribution. Combined with the transmittance design of the scanning slit, the light flux received by each detector is approximately equal. This results in the voltage signal amplitudes of the four displacement signals being similar after photoelectric conversion, effectively reducing the subdivision error caused by amplitude inconsistency and improving the linearity and repeatability of displacement measurement.

[0060] Preferably, the center lines of the four measuring scanning slits 402 in this application are spaced nT+T / 4 apart along the scanning direction, where T is the fringe period of the grating ruler 7 and n is a natural number.

[0061] As the image moves with the grating ruler 7, its light intensity distribution shifts spatially with the grating period T. The measurement scanning slit 402 acts as a spatial filter; when the distance between two measurement scanning slits 402 is an odd multiple of T / 4, a 90° phase difference will occur between their output light intensity signals.

[0062] This invention employs four measurement scanning slits 402, with the distance between adjacent slits 402 along the scanning direction being nT+T / 4. This results in four signals with a sequential phase difference of 90°, forming orthogonal signal pairs of sine, cosine, negative sine, and negative cosine. Therefore, by defining the interval between the measurement scanning slits 402, this application can extract electrical signals with orthogonal phase relationships from a single grating displacement for direction discrimination and subdivision.

[0063] This application achieves high resolution by precisely designing and measuring the spacing of the scanning slit 402, so that when the grating ruler 7 moves for one cycle T, the four detectors output four signals with a phase offset of 90° in sequence. The four orthogonal signals can be directly used for the subsequent interpolation subdivision circuit 203 to achieve high resolution and determine the direction of movement, thereby meeting the requirements for high-precision, bidirectional displacement measurement.

[0064] Optionally, such as Figures 4-6 As shown, the grating ruler 7 in this application includes an incremental grating region 702 and a zero-position grating region 701; the scanning slit on the scanning plate 4 also includes a zero-position scanning slit 403, and the photodetector also includes a zero-position photodetector 6, which is directly opposite the zero-position scanning slit 403.

[0065] The incremental grating region 702 is used to generate periodic displacement signals, but it cannot provide an absolute reference position. Therefore, this application further forms a zero-position grating region 701 on the grating ruler 7. The zero-position grating region 701 in this application is a grating line that generates a single Taber image pulse only at a specific position.

[0066] Accordingly, a zero-position scanning slit 403 is formed on the scanning plate 4 in this application, and its shape and position match the zero-position Tuber image. At the same time, the zero-position photodetector 6 is facing the zero-position scanning slit 403 to receive the zero-position signal. Therefore, through the zero-position grating region 701, the zero-position scanning slit 403 and the corresponding zero-position photodetector 6, a unique reference zero point can be provided for displacement measurement, avoiding accumulated errors.

[0067] Furthermore, by introducing the zero-position grating region 701 and the corresponding zero-position scanning slit 403, the zero-position photodetector 6 outputs a pulse signal whenever the read head passes the zero-position mark on the grating ruler 7. This signal is used to calibrate the starting point of the incremental count.

[0068] In actual implementation, the zero-position grating region 701 in this application is located in the middle position corresponding to the incremental grating region 702. The zero-position scanning slit 403 and the four measurement scanning slits 402 are independently arranged on the scanning plate 4, thereby enabling absolute reference position detection. This allows the sensor to accurately find the origin after power-on or zero-return operation, improving the reliability and ease of use of the system. It is particularly suitable for precision machining equipment that requires periodic zero-return calibration.

[0069] like Figure 4As shown, in this application, the emitted light beam 301 emitted by the light source 3 is projected onto the grating ruler 7 after passing through the cover 1. Since the zero-position grating region 701 and the incremental grating region 702 are formed on the grating ruler 7, the zero-position beam 303 and the incremental beam 302 can be formed after reflection. The zero-position beam 303 illuminates the zero-position scanning slit 403 of the scanning plate 4, and the incremental beam 302 illuminates the measurement scanning slit.

[0070] Optionally, such as Figures 1-3 As shown, the light-emitting aperture 102 in this application includes a clearance section 1021 and a light-emitting section 1022. The diameter of the clearance section 1021 is larger than the diameter of the light-emitting section 1022, and the diameter of the clearance section 1021 is not less than the maximum size of the scanning plate 4, and can completely avoid the scanning plate 4.

[0071] The light-emitting hole 102 on the top wall of the cover 1 in this application is not a through hole, but a stepped hole. The section closer to the outside of the cover 1 is the light-emitting section 1022, which has a smaller diameter and is used to limit the divergence angle of the beam 301 emitted by the light source 3, while the section closer to the inside of the cover 1 is the avoidance section 1021, which has a larger diameter and can thus prevent interference between the scanning plate 4 and the cover 1.

[0072] Optionally, such as Figure 1 Combination Figure 2 As shown, the scanned version 4 in this application is parallel to the mounting plane 101, and the angle between the mounting plane 101 and the outer surface of the top wall is an acute angle.

[0073] Since the scanning slits on the scanning plate 4 need to be precisely aligned with the photosensitive surface of the photodetector on the PCB2, if the scanning plate 4 is not parallel to the PCB2, the distance from the slits to the detector will be different at different positions, leading to defocusing and signal inhomogeneity. Simultaneously, the angle between the mounting plane 101 and the outer surface of the top wall is acute, which allows the light emitted from the light source 3 to form an oblique incident light path. Furthermore, it ensures the parallelism between the scanning plate 4 and the photodetector to guarantee clear imaging.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A grating ruler displacement sensor based on an oblique incident optical path, characterized in that, Includes the read head module and the grating ruler; The read head module includes a housing, a PCB, and a light source. The top wall of the housing has a mounting plane for mounting the PCB. The PCB is mounted on the mounting plane, and the light source is integrated on the side of the PCB facing the top wall of the housing. The top wall of the housing has a light-emitting hole corresponding to the position of the light source, so that the light emitted by the light source can exit the housing. The mounting plane is inclined and forms an angle with the outer surface of the top wall of the cover, and the grating ruler is set parallel to the outer surface of the top wall of the cover.

2. The grating ruler displacement sensor based on an oblique incident optical path according to claim 1, characterized in that, The reader module also includes a scanning plate, which is fixed inside the housing and located above the light source; The grating ruler is disposed outside the cover and above the scanning plate. The grating ruler and the scanning plate are spaced apart, and the distance between the grating ruler and the scanning plate is the Talbot imaging distance.

3. The grating ruler displacement sensor based on an oblique incident optical path according to claim 2, characterized in that, The read head module also includes a photodetector, which is disposed on the PCB; A scanning slit is formed on the scanning plate, and the photosensitive surface of the photodetector is positioned facing the scanning slit.

4. The grating ruler displacement sensor based on an oblique incident optical path according to claim 3, characterized in that, The scanning plate is also provided with a light-transmitting hole, which is directly opposite the light-emitting surface of the light source.

5. The grating ruler displacement sensor based on an oblique incident optical path according to claim 3, characterized in that, The scanning slits on the scanning plate include four measurement scanning slits, which are arranged circumferentially on the scanning plate.

6. The grating ruler displacement sensor based on an oblique incident optical path according to claim 5, characterized in that, The photodetector includes four measurement photodetectors, which are arranged in a C-shape on the PCB and are respectively facing the four measurement scanning slits.

7. The grating ruler displacement sensor based on an oblique incident optical path according to claim 6, characterized in that, The center lines of the four measurement scanning slits are spaced nT+T / 4 apart along the scanning direction, where T is the fringe period of the grating ruler and n is a natural number.

8. The grating ruler displacement sensor based on an oblique incident optical path according to claim 3, characterized in that, The grating ruler includes an incremental grating region and a zero-position grating region; The scanning slit on the scanning plate also includes a zero-position scanning slit, and the photodetector also includes a zero-position photodetector, which is directly opposite the zero-position scanning slit.

9. The grating ruler displacement sensor based on an oblique incident optical path according to claim 2, characterized in that, The light-emitting aperture includes a clearance section and a light-emitting section. The diameter of the clearance section is larger than the diameter of the light-emitting section, and the diameter of the clearance section is not less than the maximum size of the scanning plate, and it can completely avoid the scanning plate.

10. The grating ruler displacement sensor based on an oblique incident optical path according to claim 2, characterized in that, The scanning plate is parallel to the mounting plane, and the angle between the mounting plane and the outer surface of the top wall is an acute angle.

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