Contact displacement sensor and distance measurement method thereof

Abstract

The present application provides a contact displacement sensor and a distance measurement method thereof, wherein the contact displacement sensor comprises: a light source assembly for providing irradiation light; an absolute value coding scale, which is relatively fixedly connected to a measurement target and moves synchronously with the measurement target, wherein a plurality of coding units are arranged on the absolute value coding scale, wherein each coding unit comprises a plurality of coding bits represented by stripes of standard width, wherein the coding bits comprise a starting segment coding bit, a fixed coding bit and a unit identification coding bit; a linear image sensor, which is used to obtain an image of irradiation light transmitted through the absolute value coding scale; the image is recognized, the starting segment coding bit is recognized to determine the position of a target coding unit contained in the image, information of the unit identification coding bit is extracted based on the position of the target coding unit to calculate a fuzzy position, and information of the fixed coding bit is extracted to calculate a precise position, and a current motion displacement is obtained according to the fuzzy position and the precise position.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a contact displacement sensor and a distance measurement method based on the contact displacement sensor. Background Art

[0002] In the design research of high-precision sensors, the inventors of this application analyzed the principles, advantages and disadvantages of high-precision contact displacement sensors on the market, and divided the currently known contact displacement sensors into the following three types according to the detection principle:

[0003] First, the differential voltage LVDT (Linear Variable Differential Transformer), which works by generating a magnetic field when current passes through an internal coil. Figure 1 If a fiber core is inserted, the impedance of the coil changes according to the amount of insertion, and the signal level also changes. By detecting the change in the signal level, it is converted into the amount of movement.

[0004] The primary winding P of the LVDT is energized by a constant amplitude AC power supply. The resulting magnetic flux is coupled through the core to the adjacent secondary windings S1 and S2. Figure 1 As shown in (b), if the core is located in the middle of S1 and S2, equal magnetic flux is coupled to each secondary winding, so the E1 and E2 contained in the secondary windings S1 and S2 are equal, and at this reference middle core position (called the zero point), the differential voltage output (E1 - E2) is essentially zero. Figure 1 As shown in (a), if the core is moved so that its distance from S1 is smaller than its distance from S2, the magnetic flux coupled to S1 will increase, while the magnetic flux coupled to S2 will decrease, so the induced voltage E1 increases, while E2 decreases, thus generating a differential voltage (E1 - E2). Figure 1 As shown in (c), if the core moves closer to S2, the magnetic flux coupled into S2 will increase, while the magnetic flux coupled into S1 will decrease, so E2 increases and E1 decreases, resulting in a differential voltage (E2 - E1).

[0005] The advantage of this differential voltage LVDT is that the signal level changes according to the position of the spindle, so the "absolute position" can be measured (no zero point adjustment is required, and no tracking error occurs). The disadvantages are: (1) The accuracy decreases near the end of the spindle. Since the principle of the coil is used, the magnetic field is uniform near the center, but there is a tendency to lose balance near the end. (2) Linearity or temperature characteristics need to be considered. (3) The accuracy of common commercial products is about 5-50um.

[0006] Second, grating displacement sensor refers to a sensor that uses the grating fringe principle to measure displacement. Figure 2 The grating is a dense and equally spaced parallel engraved line on a long strip of optical glass, and the engraved line density is 10~200 lines / mm. The overlapping fringes formed by the grating have optical amplification and error averaging effects, thereby improving the measurement accuracy. The sensor is composed of a moving grating 51, a fixed grating 52, an optical path system 53 and a measuring system 54. The measuring system includes a frame 541, a measuring rod 542, an axle tube 543 mounted on the measuring rod 542, and a measuring probe 544 located at the end of the measuring rod 542. The moving grating 51 moves relative to the fixed grating 52, forming overlapping fringes of light and dark that are distributed roughly according to the sine law. These fringes move at the relative motion speed of the grating and are directly irradiated onto the photoelectric element, and a series of electrical pulses are obtained at their output ends, which generate digital signal outputs through the amplification, shaping, and counting systems, and directly display the measured displacement.

[0007] The advantages of this grating displacement sensor are: (1) The accuracy is basically determined by the scale accuracy of the scale, and the accuracy is relatively high. (2) Whether near the center or the end of the scale, the scale width of the scale remains unchanged, so there is no need to consider linearity. (3) Even if there is a temperature change, the scale of the scale will not change much, so the temperature characteristics are better. (4) The accuracy of common commercial products is about 0.1-2um. The disadvantages are: (1) The manufacturing cost of high-precision gratings is high. (2) The relative measurement method cannot directly measure the absolute position, and the counting needs to be restarted from zero every time the machine is turned on. (3) When the spindle is violently moving due to vibration, the photoelectric sensor will not have time to respond, and tracking errors will occur.

[0008] Third, the grating scale pulse system, such as the KEYENCE GT2 series, has a built-in transmitter, receiver, and scale. However, like the general scale method, the GT2 series scale has a slit plate with a complex pattern embedded in it, and the position of the spindle can be determined by reading the pattern.

[0009] The advantages of this grating scale pulse system are: (1) It can detect absolute position information, so there is no need for zero point adjustment and no tracking error. (2) Because it is a scale method, high-precision operation can be achieved throughout the entire measurement range. (3) The temperature characteristics are better. The disadvantages are: (1) The overall algorithm is complex, involving FFT algorithm, and has high requirements on MCU performance. (2) The manufacturing process of the grating scale is relatively complex. In addition to the standard equally spaced precision grating scale, it also requires high-precision width encoding stripes. Summary of the invention

[0010] In order to solve the existing technical problems, the present application provides a contact displacement sensor and a distance measurement method thereof which have high accuracy, do not need to consider linearity and temperature characteristics, and can realize absolute value measurement.

[0011] In a first aspect, a contact displacement sensor is characterized by comprising:

[0012] A light source assembly, used for providing irradiation light;

[0013] An absolute value coding scale is relatively fixedly connected to a measurement target and moves synchronously with the measurement target. The absolute value coding scale is provided with a plurality of coding units, each of which includes a plurality of coding positions represented by stripes of standard width, and the coding positions include a starting segment coding position, a fixed coding position and a unit identification coding position;

[0014] A linear image sensor is used to obtain an image of the irradiated light transmitted through the absolute value coded scale, identify the image, identify the starting segment coding bit to determine the position of the target coding unit contained in the image, extract the information of the unit identification coding bit based on the position of the target coding unit to calculate the blurred position, and extract the information of the fixed coding bit to calculate the precise position, and obtain the current motion displacement according to the blurred position and the precise position.

[0015] In a second aspect, a distance measurement method of a contact displacement sensor provided in any embodiment of the present application is provided, comprising:

[0016] Acquire an image of the illumination light transmitted through the absolute value encoding scale acquired by the linear image sensor;

[0017] Extracting grayscale information of pixels in the image, calculating the half-height full width of the black etching stripes to identify the starting segment coding bit, and determining the position of the target coding unit in the image;

[0018] Based on the position of the target coding unit, extract the information of the unit identification coding bit contained in the target coding unit to determine the unit number code of the target coding unit, and calculate the fuzzy position based on the measurable range of the coding unit and the unit number code;

[0019] Based on the position of the target coding unit, extract information of the fixed coding bits contained in the target coding unit to determine the sub-pixel centroid position corresponding to the fixed coding bit, and calculate the precise position using the sub-pixel centroid position;

[0020] The current motion displacement is obtained according to the fuzzy position and the precise position.

[0021] The contact displacement sensor provided in the above embodiment is provided with an absolute value coding scale and a linear image sensor, and uses the unit identification coding bits on the absolute value coding scale to carry identification information for distinguishing different coding units, and uses the positions of different coding units to correspond to the effective measurable range that can be represented. The linear image sensor can identify the starting segment coding bits contained in the current image based on the image of the absolute value coding scale through which the irradiated light is transmitted, and determines the position of the corresponding target coding unit, extracts the information of the unit identification coding bits based on the position of the target coding unit, calculates the fuzzy position based on the effective measurable range that can be represented by the corresponding target coding unit, and extracts the information of the fixed coding bits to calculate the precise position, and obtains the current motion displacement according to the fuzzy position and the precise position. In this way, by using the combination of the absolute value coding scale and the linear image sensor, the amount of calculation can be effectively reduced, and high-precision absolute value position detection information can be obtained by avoiding complex calculations. The scale width of the absolute value coding scale is uniform and is not affected by temperature changes. There is no need to consider linearity and temperature characteristics, and high-precision measurement can be ensured.

[0022] The distance measurement method based on the contact displacement sensor provided in the above embodiment belongs to the same concept as the corresponding contact displacement sensor embodiment, and thus has the same technical effect as the corresponding contact displacement sensor embodiment, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the measurement principle of a known differential voltage LVDT.

[0024] Figure 2 Schematic diagram of the measurement principle of a known grating displacement sensor.

[0025] Figure 3 A structural block diagram of a contact displacement sensor provided in one embodiment.

[0026] Figure 4 A schematic structural diagram of a contact displacement sensor provided in another embodiment.

[0027] Figure 5 A schematic structural diagram of an absolute value coding scale provided in one embodiment.

[0028] Figure 6 A distance measurement method for a contact displacement sensor is provided in an embodiment.

[0029] Component Symbols:

[0030] Light source assembly 10, LED light source 11, single lens 12, reflector 13, wedge mirror 14, absolute value coding scale 20, coding unit 21, start segment coding position 23, fixed coding position 24, unit identification coding position 25, interval coding position 26, linear image sensor 30;

[0031] Primary winding P, secondary windings S1 and S2, movable grating 51, fixed grating 52, optical path system 53, measuring system 54, frame 541, measuring rod 542, shaft tube 543, and measuring probe 544. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0033] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present application. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0034] In the following description, the expression "some embodiments" is involved, which describes a subset of all possible embodiments. It should be noted that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.

[0035] In the following description, the terms "first, second, third" involved are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first, second, third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0036] Please refer to Figure 3 and Figure 4 , is a schematic structural diagram of a contact displacement sensor provided in an embodiment of the present application, wherein the contact displacement sensor includes a light source assembly 10, an absolute value encoding scale 20 and a linear image sensor 30.

[0037] The light source assembly 10 is used to provide irradiation light. The absolute value coded scale 20 is relatively fixedly connected to the measurement target and moves synchronously with the measurement target. The absolute value coded scale 20 is provided with a plurality of coding units 21, each coding unit 21 includes a plurality of coding positions represented by standard width stripes, and the coding positions include a starting segment coding position 23, a fixed coding position 24 and a unit identification coding position 25. The linear image sensor 30 is used to obtain an image of the irradiation light transmitted through the absolute value coded scale 20, identify the image, identify the starting segment coding position 23 to determine the position of the target coding unit 21 contained in the image, extract the information of the unit identification coding position 25 based on the position of the target coding unit 21 to calculate the fuzzy position, and extract the information of the fixed coding position 24 to calculate the precise position, and obtain the current motion displacement according to the fuzzy position and the precise position.

[0038] The absolute value coding scale 20 is provided with a plurality of coding units 21 repeatedly arranged along its length direction. The coding units 21 at different positions can use the unit identification coding bit 25 to carry identification information representing their identities. In this way, the linear image sensor 30 uses the imaged image of the absolute value coding scale 20 for image detection. The identity of the coding unit 21 contained in the current image can be confirmed by extracting the information of the unit identification coding bit 25, so that the fuzzy position can be calculated according to the effective measurement range that can be represented by the position of the corresponding coding unit 21 on the absolute value coding scale 20. Each coding unit 21 also includes the same and consistent starting segment coding bit 23, so that the linear image sensor 30 uses the imaged image of the absolute value coding scale 20 for image detection, and can more accurately and quickly determine the position of the coding unit 21 in the image, and then extract the information of all the coding bits contained in the coding unit 21, such as the unit identification coding bit 25 and the fixed coding bit 24, which is conducive to improving the detection efficiency, reducing the amount of calculation, reducing the interference of non-effective information in the image, and improving the measurement accuracy. The setting of the fixed coding bit 24 can provide a method for extracting the centroid position of the corresponding standard width stripe to calculate the precise position and achieve high-precision measurement.

[0039] It should be noted that the process of acquiring the image of the linear image sensor 30, identifying and determining the target coding unit 21, and extracting the information of each coding bit in the target coding unit 21 to calculate the ranging displacement can be completed by the linear image sensor 30 or by an independent processing chip. This application does not impose any restrictions on this and it falls within the protection scope of this application.

[0040] The contact displacement sensor provided in the above embodiment uses the absolute value coding scale 20 to set a plurality of coding units 21, and the unit identification coding positions 25 of different coding units 21 correspond to carrying identification information for distinguishing different coding units 21. The linear image sensor 30 can identify the starting segment coding position 23 contained in the current image based on the image of the irradiated light transmitted through the absolute value coding scale 20, so as to lock the position of the coding unit 21 (target coding unit 21) contained in the current image in the image, thereby more quickly extracting the unit identification coding position 25 and the fixed coding position 23 of the target coding unit 21. The information of the target coding unit 24 is used to calculate the blurred position based on the effective measurable range that can be represented by the corresponding target coding unit 21, and the information of the fixed coding bit 24 is extracted to calculate the precise position, and the current motion displacement is obtained according to the blurred position and the precise position. In this way, the combination of the absolute value coding scale 20 and the linear image sensor 30 can effectively reduce the amount of calculation, avoid complex calculations, and obtain high-precision absolute value position detection information. The scale width formed by the coding unit 21 on the absolute value coding scale 20 is uniform and is not affected by temperature changes. There is no need to consider linearity and temperature characteristics, and high-precision measurement can be ensured.

[0041] See also Figure 3 In some embodiments, each coding position in the coding unit 21 corresponds to a standard width stripe on the absolute value coding scale 20, and the standard width stripe refers to a black etched stripe or a white transparent non-etched stripe. The value of the coding position corresponding to the black etched stripe is 1, and the value of the coding position corresponding to the white transparent non-etched stripe is 0. It should be noted that the black etched stripe should be understood in a broad sense here, as long as the irradiated light is projected through the corresponding position, it can have a certain grayscale when imaging on the linear image sensor 30, such as the black etched stripe can also be a gray etched stripe.

[0042] In some embodiments, the starting segment coding position 23 includes a first preset number of black etching stripes arranged in a row; the fixed coding position 24 includes a second preset number of white transparent non-etching stripes; and the unit identification coding position 25 includes a third preset number of black etching stripes arranged in groups, and the number of black etching stripes arranged in a row in each group is less than the first preset number. The starting segment coding position 23 uses the first preset number of black etching stripes arranged in a row, so that when the linear image sensor 30 performs image recognition, the starting segment coding position 23 can be accurately identified by extracting the grayscale data of the pixel points in the image for statistics. The fixed coding position 24 uses the second preset number of white transparent non-etching stripes and is set adjacent to the starting segment coding position 23, so as to facilitate the position of the target coding unit 21 determined according to the starting segment coding position 23, and quickly and accurately extract the sub-pixel centroid position of the unit for calculating the precise position. The total number of black etching stripes in the unit identification coding bit 25 correspondingly determines the number of coding bits contained in the unit identification coding bit 25 of each coding unit 21, and further determines the number of coding units 21 that can be distinguished by the unit identification coding bit 25. For example, the unit identification coding bit 25 is 9 bits, each bit can take a value of 0 or 1, and 512 identifiers that can identify the identities of different coding units can be provided. In this embodiment, the total number of coding bits contained in the unit identification coding bit 25, that is, the third preset number is greater than the first preset number, and in the unit identification coding bit 25, the third preset number of black etching stripes are arranged in groups, and the number of continuously arranged black etching stripes in each group is less than the first preset number, so as to facilitate the linear image sensor 30 to accurately distinguish the starting segment coding bit 23 and the unit identification coding bit 25 when performing image recognition.

[0043] In an optional specific example, the third preset number is 9 bits; in the unit identification code bit 25, adjacent groups of black etching stripes are separated by a spacing code bit 26. In this embodiment, the spacing code bit 26 in the unit identification code bit 25 is a white transparent non-etched stripe. The black etching stripes in the unit identification code bit 25 are grouped by using white transparent non-etched stripes, so that the number of code bits included in the starting segment code bit 23 is greater than the number of black etching stripes arranged continuously in each group in the unit identification code bit 25. In this way, in the image recognition process, the third preset number of unit identification code bits 25 can be avoided from being confused with the first preset number of starting segment code bits 23.

[0044] In some embodiments, the number of consecutively arranged black etched stripes in each group is not greater than 5 bits, and the first preset number is 6 bits. In an optional example, each coding unit 21 includes 20 bits, and 1 bit corresponds to a black etched stripe or a white transparent non-etched stripe of a standard width on the absolute value coding scale 20. The coding bit corresponding to the black etched stripe is bit0, and the coding bit corresponding to the white transparent non-etched stripe is bit1. The first 8 bits of each coding unit 21 are identical and consistent, including 6 starting segment coding bits 23, corresponding to 6 consecutively arranged black etched stripes on the absolute value coding scale 20 in front of the coding unit 21, for the purpose of marking a uniform starting position of a coding unit 21; followed by 1 fixed coding bit 24, corresponding to 1 white transparent non-etched stripe on the absolute value coding scale 20, to provide consistent spot features for subsequent extraction of sub-pixel centroids; and then 1 bit corresponding to 1 black etched stripe is used to separate the fixed coding bit 24 and the unit identification coding bit 25, so as to facilitate the extraction of the precise position of the white transparent non-etched stripe of the sub-pixel centroid. In this way, the first 8 bits of each coding unit 21 are exactly the same, such as 0b00000010.

[0045] In some embodiments, each coding bit corresponds to 3 to 6 pixels in the image obtained by imaging the linear image sensor; each coding bit corresponds to a standard width stripe of 30 to 100 um. Still taking the example that each coding unit 21 includes 20 bits of coding bits, a single coding unit 21 can support a measurement range of 2 mm, and the unit identification code includes 9 bits, which can achieve a total of 512 valid values ​​from 0b000000000 to 0b1111111111, so that a total of 512 coding units 21 can be distinguished accordingly, and effective measurement within a range of 1024 mm can be achieved. In order to avoid confusion between the 9-bit unit identification code and the starting segment code using 6-bit coding bits, the 9-bit unit identification code is divided into two groups, and the two groups are separated by white transparent non-etched stripes. The longest continuous code length in each group is 5 bits of coding bits. Figure 3 In the example shown, each coding unit 21 includes 20 bit coding bits, including 6 black bit coding bits as the starting segment coding bits 23, 1 bit coding bit for sub-pixel centroid extraction position, 1 bit coding bit as a black spacing bit, 9 bit coding bits for unit identification coding, and 3 bit coding bits as white spacing bits. It can be seen that each coding unit 21 can be identified by using 9 unit identification coding bits, such as (0b011010010), except for the multiple identical bit coding bits in front of each coding unit 21 and the bit coding bits used for spacing.

[0046] Please refer again Figure 3In some embodiments, the light source assembly 10 includes an LED light source 11, and a lens group disposed between the LED light source 11 and the absolute value coding scale 20; the lens group reflects and refracts the light emitted by the LED light source 11 to form a parallel expanded beam directed to the absolute value coding scale 20. The LED light source 11 may be a high-brightness LED, such as a high-brightness LED product with consistent divergence angles of the fast and slow axes. The lens group reflects and refracts the light beam emitted by the LED light source 11 to ultimately form a parallel beam with uniform brightness and an emission range that meets the requirements.

[0047] Optionally, the lens group includes a single lens 12, a reflector 13 and a wedge mirror 14; the single lens 12 is a plano-convex spherical lens, and the single lens 12 converts the emitted light of the LED light source 11 into a parallel light beam of a first diameter; the reflector 13 totally reflects the light emitted by the single lens 12 to form a parallel light beam of a second diameter; the wedge mirror 14 transmits the light reflected by the reflector 13 to form a parallel light beam of a third diameter and uniform brightness; the third diameter is greater than the second diameter, and the second diameter is greater than the first diameter. The lens material of the single lens 12 can be optical glass or optical plastic. After passing through the single lens 12, the light beam becomes a parallel light with a diameter of about 3-6 mm. The reflector 13 can be made of a high-reflectivity dielectric film or a high-refractive-index glass. By using the principle of total reflection at large-angle incidence, the spot diameter will increase to 5-10 mm after reflection, and it is still a parallel light beam. The parallel light beam after the reflector 13 is incident obliquely on the wedge mirror 14. The wedge mirror 14 can further increase the spot diameter to 6-12mm, keep it as a parallel light beam, and use the wide spectrum characteristics of the LED light source 11 to even out the brightness spatial distribution of the spot and prevent the formation of laser speckle. In this way, through the lens group, a parallel light beam with uniform brightness and a width of 6-12mm (3-6mm in height in the vertical direction of the paper) can be formed, and the divergence angle of the parallel light beam in the vertical direction is less than 2mrad. It is used to illuminate the absolute value encoding scale 20 that moves synchronously with the target to be measured, and finally form light and dark stripes on the linear image sensor 30CMOS.

[0048] See also Figure 5 On the other hand, the present application also provides a distance measurement method of a contact displacement sensor, comprising:

[0049] S101, acquiring an image of the irradiated light transmitted through the absolute value encoding scale, which is acquired by a linear image sensor.

[0050] S103, extracting grayscale information of pixels in the image, calculating the half-height full width of the black etching stripes to identify the start segment coding bit, and determining the position of the target coding unit in the image.

[0051] S105, based on the position of the target coding unit, extract the information of the unit identification coding bit contained in the target coding unit to determine the unit number code of the target coding unit, and calculate the fuzzy position based on the measurable range of the coding unit and the unit number code.

[0052] S107, based on the position of the target coding unit, extract the information of the fixed coding bits contained in the target coding unit to determine the sub-pixel centroid position corresponding to the fixed coding bit, and calculate the precise position using the sub-pixel centroid position.

[0053] S109, obtaining the current motion displacement according to the fuzzy position and the precise position.

[0054] In the process of distance measurement of the contact displacement sensor, the absolute value coding scale 20 is rigidly connected to the measurement target and moves up and down with the measurement target. The linear image sensor 30 is used to image the absolute value coding scale 20 in the moving process. The linear image sensor 30 can act as a fixed grating and detection element in the contact displacement sensor by taking advantage of the good pixel spacing consistency.

[0055] Since the absolute value coding scale 20 can move up and down, the linear image sensor 30 receives the imaging of the light source through the black and white standard width stripes moving up and down, determines the approximate displacement according to the identification of the coding unit 21 in the current imaging, and then determines the precise position according to the sub-pixel centroid position of the white transparent non-etched stripes corresponding to the fixed coding position 24 in the coding unit 21. In an optional example, the distance measurement method mainly includes:

[0056] First, the grayscale information (GrayValue) of each pixel (pixel) of the linear image sensor 30 (Linear CMOS) is extracted.

[0057] Calculate the half-maximum full width (HMFW) of each black etched stripe, find the maximum value near the center of the CMOS, corresponding to 6 bits (which is also the widest black etched stripe), and determine the starting pixel position of the unit.

[0058] According to the unit starting pixel position, read the pixel gray value corresponding to the bit coding position contained in the coding unit 21, and determine the corresponding value of each bit coding position as 0 / 1 according to the overall gray value, and finally merge to obtain the 9-bit coding unit 21 identification, determine the unit number, and determine the approximate position according to the unit number code. For example, 0b011010010 corresponds to 210 in decimal, and the unit width is 2mm, then the corresponding unit position is 420mm.

[0059] According to the unit start position, the sub-pixel position of the encoding unit 21 is extracted. The sub-pixel extraction algorithm can be a conventional centroid method, such as the sub-pixel centroid position is 248.46, corresponding to the precise position 0.8535mm.

[0060] The final position is the unit position plus the exact position, such as 420.8535mm in the example.

[0061] The contact displacement sensor and the distance measurement method thereof provided in the embodiments of the present application have at least the following characteristics:

[0062] First, an absolute value coding scale 20 is designed, and a plurality of coding units 21 are arranged on the absolute value coding scale 20. The starting segment of each coding unit 21 is marked with fixed 6 black stripes, which helps the MCU (single-chip microcomputer) to quickly extract and identify the entire unit.

[0063] Second, the combination of reflection and refraction methods is used to achieve uniform and parallel illumination light, which is beneficial to ensure the imaging quality of the black and white interval stripes.

[0064] Third, the unit coding of the absolute value coded scale uses equal-width black and white standard-width stripes to realize binary, so that the number of effective codes of the coding unit 21 can be as high as 2 to 9. When the measurable range of a single unit is 2 mm, effective measurement within the range of 1024 mm can be achieved.

[0065] Fourthly, the coding unit 21 of the absolute value coding scale 20 is interrupted by white standard width stripes set at specific positions, so as to effectively distinguish the starting section of the coding unit 21 by using fixed 6 black standard width stripes, which is conducive to quickly identifying the regional position of the entire coding unit 21.

[0066] Fifth, in a single coding unit 21 in the absolute value coding scale 20, a standard white standard width stripe is used to set up a sub-pixel centroid extraction method to extract the centroid of a light spot of a specific width, which can ensure the consistency and accuracy of the sub-pixel centroid extraction.

[0067] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0068] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods of various embodiments of the present invention.

[0069] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A contact displacement sensor, characterized in that: include: A light source assembly, used for providing irradiation light; An absolute value coding scale is relatively fixedly connected to a measurement target and moves synchronously with the measurement target. The absolute value coding scale is provided with a plurality of coding units, each of which includes a plurality of coding positions represented by stripes of standard width, and the coding positions include a starting segment coding position, a fixed coding position and a unit identification coding position; A linear image sensor is used to obtain an image of the irradiated light transmitted through the absolute value coded scale; identify the image, identify the starting segment coding bit to determine the position of the target coding unit contained in the image, extract the information of the unit identification coding bit based on the position of the target coding unit to calculate the fuzzy position, and extract the information of the fixed coding bit to calculate the precise position, and obtain the current motion displacement according to the fuzzy position and the precise position; wherein the linear image sensor extracts the information of the unit identification coding bit contained in the target coding unit based on the position of the target coding unit to determine the unit number code of the target coding unit, and calculates the fuzzy position based on the measurable range of the coding unit and the unit number code; extracts the information of the fixed coding bit contained in the target coding unit based on the position of the target coding unit to determine the sub-pixel centroid position corresponding to the fixed coding bit, and calculates the precise position using the sub-pixel centroid position; Each of the coding bits corresponds to a set number of pixels in the image obtained by imaging the linear image sensor, each of the coding bits corresponds to a standard width stripe of 30-100 um, and the set number is 3-6; The light source assembly comprises an LED light source, and a lens group disposed between the LED light source and the absolute value coding scale; the lens group reflects and refracts the light emitted from the LED light source to form a parallel expanded beam directed toward the absolute value coding scale; wherein the lens group comprises a single lens, a reflector, and a wedge mirror, the single lens being a plano-convex spherical lens, the single lens converts the light emitted from the LED light source into a parallel beam of a first diameter, the reflector totally reflects the light emitted from the single lens to form a parallel beam of a second diameter, the wedge mirror transmits the light reflected from the reflector to form a parallel beam of a third diameter and uniform brightness, the third diameter being greater than the second diameter, and the second diameter being greater than the first diameter; The measurable range of each coding unit is 2 mm; the unit identification coding bit includes 9 coding bits, which can achieve effective measurement within a range of 1024 mm.

2. The contact displacement sensor according to claim 1, characterized in that: The standard width stripes are either black etched stripes or white transparent non-etched stripes.

3. The contact displacement sensor according to claim 1, characterized in that: The start segment coding bits include a first preset number of black etching stripes arranged continuously; The fixed coding bits include a second preset number of white transparent non-etched stripes; The unit identification coding bits include a third preset number of black etching stripes arranged in groups, and the number of the black etching stripes arranged continuously in each group is less than the first preset number.

4. The contact displacement sensor according to claim 3, characterized in that: The third preset number is 9 bits; In the unit identification code bit, adjacent groups of the black etched stripes are separated by a white transparent non-etched stripe.

5. The contact displacement sensor according to claim 3, characterized in that: The number of the black etching stripes arranged continuously in each group is no more than 5 bits, and the first preset number is 6 bits.

6. A distance measurement method based on the contact displacement sensor according to any one of claims 1 to 5, characterized in that: include: Acquire an image of the illumination light transmitted through the absolute value encoding scale acquired by the linear image sensor; Extracting grayscale information of pixels in the image, calculating the half-height full width of the black etching stripes to identify the starting segment coding bit, and determining the position of the target coding unit in the image; Based on the position of the target coding unit, extract the information of the unit identification coding bit contained in the target coding unit to determine the unit number code of the target coding unit, and calculate the fuzzy position based on the measurable range of the coding unit and the unit number code; Based on the position of the target coding unit, extract information of the fixed coding bits contained in the target coding unit to determine the sub-pixel centroid position corresponding to the fixed coding bit, and calculate the precise position using the sub-pixel centroid position; The current motion displacement is obtained according to the fuzzy position and the precise position.

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