CN118999641B - Contact displacement sensor and distance measurement method thereof - Google Patents

Abstract

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

Description

Contact type displacement sensor and distance measuring method thereof

Technical Field

The application relates to the technical field of sensors, in particular to a contact type displacement sensor and a distance measuring method based on the contact type displacement sensor.

Background

In the design research of the high-precision sensor, the inventor analyzes the principle and advantages and disadvantages of the high-precision contact type displacement sensor on the market, and mainly divides the currently known contact type displacement sensor into the following three types according to the detection principle:

First, a differential voltage LVDT (Linear Variable Differential Transformer ) is based on the principle that a magnetic field is generated when a current is passed through an internal coil. Referring to fig. 1, if a core is inserted therein, the impedance of the coil varies according to the insertion amount, and the signal level also varies, and the variation of the signal level is detected to convert into a shift amount.

The primary winding P of the LVDT is energized by a constant amplitude ac power supply. The magnetic flux thus formed is coupled by the core to the adjacent secondary windings S1 and S2. As shown in fig. 1 (b), if the core is located in the middle of S1 and S2, an equal magnetic flux will be coupled to each secondary winding, so that E1 and E2 contained in each of the secondary windings S1 and S2 are equal, and the differential voltage output (E1-E2) is essentially zero at this reference middle core position (referred to as zero). As shown in fig. 1 (a), if the core is moved to have a smaller distance from S1 than from S2, the magnetic flux coupled into S1 increases and the magnetic flux coupled into S2 decreases, so that the induced voltage E1 increases and E2 decreases, thereby generating a differential voltage (E1-E2). Conversely, as shown in FIG. 1 (c), if the core moves closer to S2, the magnetic flux coupled into S2 increases and the magnetic flux coupled into S1 decreases, so E2 increases and E1 decreases, thereby producing a differential voltage (E2-E1).

The differential voltage LVDT has the advantage that the absolute position of the measurement can be grasped (zero point adjustment is not needed, and tracking error is not generated) because the signal level can be changed according to the position of the spindle. The disadvantage is (1) that the accuracy is reduced near the end of the spindle. Since the principle of the coil is utilized, the magnetic field is uniform near the center, but the balance tends to be lost near the ends. (2) linearity or temperature characteristics need to be considered. And (3) the precision of common commercial products is about 5-50 um.

And the second, grating type displacement sensor, refer to a sensor for measuring displacement by adopting grating stacking grating principle. Referring to FIG. 2, the grating is a rectangular optical glass with dense and equidistant parallel scribe lines, and the scribe line density is 10-200 lines/mm. The moire fringes formed by the gratings have an optical amplification effect and an error averaging effect, so that the measurement accuracy can be improved. The sensor consists of a moving grating 51, a fixed grating 52, an optical path system 53 and a measuring system 54. The measuring system comprises a frame 541, a measuring rod 542, a shaft tube 543 sleeved on the measuring rod 542, and a measuring probe 544 positioned at the end of the measuring rod 542. The movable grating 51 moves relative to the fixed grating 52 to form superimposed fringes with alternate light and dark portions distributed in a substantially sinusoidal pattern. The stripes move at the relative motion speed of the grating and directly irradiate the photoelectric element, a series of electric pulses are obtained at the output ends of the stripes, digital signals are generated by an amplifying, shaping and counting system to be output, and the measured displacement is directly displayed.

The grating displacement sensor has the advantages that (1) the precision is basically determined by the scale precision of the graduated scale, and the precision is higher. (2) The scale width of the scale is unchanged regardless of the vicinity of the center or the end of the scale, so that linearity is not required to be considered. (3) Even if there is a temperature change, the scale of the scale will not change greatly, so the temperature characteristic is better. (4) the precision of common commercial products is about 0.1-2 um. The disadvantage is (1) the high precision grating is costly to manufacture. (2) The relative measurement method cannot directly measure the absolute position, and the zero point is required to be restarted for counting each time of starting. (3) When the spindle is severely moved due to vibration or the like, the photoelectric sensor does not respond, and tracking errors occur.

Third, grating scale pulse systems, such as the ken GT2 series of products, incorporate transmitters, receivers and scales. However, as in the general scale method, a slit plate having a complicated pattern is embedded in the GT2 scale, and the position of the spindle can be specified by reading the pattern.

The grating graduated scale pulse system has the advantages that (1) absolute position information can be detected, zero point adjustment is not needed, and tracking errors are not generated. (2) Because of the scale method, the whole measuring range can realize high-precision operation. (3) temperature characteristics are preferable. The method has the defects that (1) the whole algorithm is complex, the FFT algorithm is involved, and the requirement on the MCU performance is high. (2) The grating scale is complex in manufacturing process, and high-precision width coding stripes are required besides standard equal-interval precision grating scales.

Disclosure of Invention

In order to solve the existing technical problems, the application provides the contact type displacement sensor and the ranging method thereof, which have higher precision, do not need to consider linearity and temperature characteristics and can realize absolute value measurement.

In a first aspect, a contact displacement sensor includes:

a light source assembly for providing illumination light;

the absolute value coding graduated scale is fixedly connected with a measuring target relatively and synchronously moves with the measuring target, a plurality of coding units are arranged on the absolute value coding graduated scale, each coding unit comprises a plurality of coding bits represented by standard width stripes, and each coding bit comprises a starting section coding bit, a fixed coding bit and a unit identification coding bit;

The linear image sensor is used for acquiring an image of the absolute value coding scale through which the irradiation light is transmitted, identifying the image, identifying the initial segment coding bit to determine the position of a target coding unit contained in the image, extracting information of the unit identification coding bit based on the position of the target coding unit to calculate a fuzzy position, extracting information of the fixed coding bit to calculate a precise position, and obtaining current motion displacement according to the fuzzy position and the precise position.

In a second aspect, a ranging method of a contact displacement sensor according to any embodiment of the present application is provided, including:

Acquiring an image of the irradiation light acquired by the linear image sensor and transmitted through the absolute value coding scale;

Extracting gray information of pixels in the image, calculating the full width at half maximum of black etching stripes to identify initial segment coding bits, and determining the position of a target coding unit in the image;

Extracting information of unit identification coding bits contained in the target coding unit based on the position of the target coding unit to determine a unit number code of the target coding unit, and calculating a fuzzy position based on a measurable range of the coding unit and the unit number code;

Based on the position of the target coding unit, extracting information of a fixed coding bit contained in the target coding unit to determine a sub-pixel centroid position corresponding to the fixed coding bit, and calculating an accurate position by using the sub-pixel centroid position;

And obtaining the current motion displacement according to the fuzzy position and the accurate position.

According to the contact displacement sensor provided by the embodiment, the absolute value coding graduated scale and the linear image sensor are arranged, the unit identification coding bits on the absolute value coding graduated scale are used for carrying identification information for distinguishing different coding units, the effective measurable range which can be characterized by the position correspondence of the different coding units is used, the linear image sensor can identify the position of the corresponding target coding unit based on the image of the irradiation light transmitted through the absolute value coding graduated scale, the position of the corresponding target coding unit is determined based on the initial section coding bit contained in the current image, the information of the coding bit is extracted based on the position of the target coding unit, the fuzzy position is calculated based on the effective measurable range which can be characterized by the corresponding target coding unit, the information of the fixed coding bit is extracted to calculate the accurate position, and the current motion displacement is obtained according to the fuzzy position and the accurate position, so that the calculated amount can be effectively reduced by using the combination of the absolute value coding graduated scale and the linear image sensor, the absolute value position detection information with high precision can be obtained without complex operation, the graduation width of the absolute value coding graduated scale is uniform and the influence of temperature change is avoided, and the linearity and the high measurement precision can be ensured without considering the characteristics of linearity and temperature.

The distance measuring method based on the contact displacement sensor provided in the above embodiment belongs to the same concept as the corresponding contact displacement sensor embodiment, so that the distance measuring method has the same technical effect as the corresponding contact displacement sensor embodiment, and is not described herein.

Drawings

Fig. 1 is a schematic diagram of a measurement principle of a conventional differential voltage LVDT.

Fig. 2 is a schematic diagram of a measurement principle of a known grating displacement sensor.

Fig. 3 is a block diagram of a contact displacement sensor according to an embodiment.

Fig. 4 is a schematic structural diagram of a contact displacement sensor according to another embodiment.

Fig. 5 is a schematic structural diagram of an absolute value encoding scale according to an embodiment.

Fig. 6 is a schematic diagram showing a distance measurement method of a touch displacement sensor according to an embodiment.

Reference numerals illustrate:

The LED light source comprises a light source assembly 10, an LED light source 11, a single lens 12, a reflecting mirror 13, a wedge-shaped mirror 14, an absolute value coding scale 20, a coding unit 21, a start section coding bit 23, a fixed coding bit 24, a unit identification coding bit 25, an interval coding bit 26 and a linear image sensor 30;

Primary winding P, secondary windings S1, S2, moving grating 51, fixed grating 52, optical path system 53, measurement system 54, frame 541, measurement rod 542, shaft tube 543, measurement probe 544.

Detailed Description

The technical scheme of the invention is further elaborated below by referring to the drawings in the specification and the specific embodiments.

The present application will be further described in detail with reference to the accompanying drawings, for the purpose of making the objects, technical solutions and advantages of the present application more apparent, and the described embodiments should not be construed as limiting the present application, and all other embodiments obtained by those skilled in the art without making any inventive effort are within the scope of the present application.

In the following description, reference is made to the expression "some embodiments" which describe a subset of all possible embodiments, it being 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.

In the following description, the terms "first, second, third" and the like are used merely to distinguish between similar objects and do not represent a specific ordering of the objects, it being understood that the "first, second, third" may be interchanged with a specific order or sequence, as permitted, to enable embodiments of the application described herein to be practiced otherwise than as illustrated or described herein.

Referring to fig. 3 and 4 in combination, a schematic structural diagram of a touch displacement sensor according to an embodiment of the application is provided, and the touch displacement sensor includes a light source assembly 10, an absolute value encoding scale 20 and a linear image sensor 30.

Wherein the light source assembly 10 is used for providing illumination light. The absolute value coding scale 20 is fixedly connected with the measuring target relatively and synchronously moves with the measuring target, a plurality of coding units 21 are arranged on the absolute value coding scale 20, each coding unit 21 comprises a plurality of coding bits characterized by standard width stripes, and each coding bit comprises a start section coding bit 23, a fixed coding bit 24 and a unit identification coding bit 25. A linear image sensor 30 for acquiring an image in which the irradiation light is transmitted through the absolute value encoding scale 20, recognizing the image, recognizing the start section encoding bit 23 to determine the position of the target encoding unit 21 contained in the image, extracting information of the unit identification encoding bit 25 based on the position of the target encoding unit 21 to calculate a blurred position, and extracting information of the fixed encoding bit 24 to calculate a precise position, and obtaining the current motion displacement from the blurred position and the precise position.

The absolute value coding scale 20 is provided with a plurality of coding units 21 which are repeatedly arranged along the length direction, and the coding units 21 at different positions can carry identification information representing the identity of the coding units by using the unit identification coding bits 25, so that the linear image sensor 30 performs image detection by using an imaging image of the absolute value coding scale 20, and the identity of the coding units 21 contained in the current image can be confirmed by extracting the information of the unit identification coding bits 25, so that the fuzzy position can be calculated according to the effective measuring range which can be represented by the position of the corresponding coding units 21 on the absolute value coding scale 20. Each coding unit 21 further includes the same initial segment coding bit 23, so that the linear image sensor 30 can more accurately and rapidly determine the position of the coding unit 21 in the image by using the imaging image of the absolute value coding scale 20, and further extract the information of all coding bits included in the coding unit 21, such as the information of the unit identification coding bit 25 and the fixed coding bit 24, which is beneficial to improving the detection efficiency, reducing the calculation amount, reducing the interference of non-effective information in the image and improving the measurement accuracy. The fixed encoding bit 24 is set, and the centroid position of the corresponding standard width stripe can be extracted to calculate the accurate position, so that high-precision measurement is realized.

It should be noted that, the calculation process of acquiring the image of the linear image sensor 30, identifying and determining the target coding unit 21, extracting the information of each section of coding bits in the target coding unit 21 to calculate the ranging displacement may be completed by the linear image sensor 30 or may be completed by an independent processing chip, which is not limited in the present application and falls within the scope of protection of the present application.

In the touch displacement sensor provided in the above embodiment, the absolute value coding scale 20 is used to set a plurality of coding units 21, the unit identification coding bits 25 of different coding units 21 correspondingly carry identification information for distinguishing different coding units 21, the linear image sensor 30 can identify the initial segment coding bit 23 contained in the current image based on the image of the absolute value coding scale 20 transmitted by the irradiation light, so as to lock the position of the coding unit 21 (target coding unit 21) contained in the current image in the image, further the information of the unit identification coding bit 25 and the fixed coding bit 24 of the target coding unit 21 can be extracted more rapidly, the fuzzy position is calculated based on the effective measurable range which 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 fuzzy position and the precise position.

Referring to fig. 3, in some embodiments, each code bit in the code unit 21 corresponds to a standard width stripe on the absolute value code scale 20, and the standard width stripe is a black etched stripe or a white transparent etching-free stripe. The value of the black etching stripe corresponding to the coding bit is 1, and the value of the white transparent etching-free stripe corresponding to the coding bit is 0. The black etched stripe is understood broadly herein, and may be a gray etched stripe, for example, if the black etched stripe can have a certain gray scale when the linear image sensor 30 is imaged when the irradiation light is projected through the corresponding position.

In some embodiments, the start segment encoding bits 23 include a first predetermined number of black etched stripes arranged in succession, the fixed encoding bits 24 include a second predetermined number of white transparent non-etched stripes, and the unit identification encoding bits 25 include a third predetermined number of black etched stripes arranged in groups, the number of black etched stripes arranged in succession in each group being less than the first predetermined number. The initial segment encoding bits 23 are sequentially arranged and have a first preset number of black etching stripes, so that when the linear image sensor 30 performs image recognition, the initial segment encoding bits 23 can be accurately recognized by extracting gray data of pixels in the image and performing statistics. The fixed encoding bits 24 are a second preset number of white transparent etching-free stripes and are arranged next to the initial segment encoding bits 23, so that the sub-pixel centroid positions of the target encoding units 21 determined according to the initial segment encoding bits 23 can be rapidly and accurately extracted for calculating the accurate positions. 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 which can be distinguished by the unit identification coding bit 25, for example, the unit identification coding bit 25 is 9 bits, and each bit can take a value of 0 or 1, so that 512 identifications capable of identifying different coding unit identities can be provided. In this embodiment, the total number of the encoding bits included in the unit identification encoding bits 25, that is, the third preset number is greater than the first preset number, and the third preset number of black etching stripes in the unit identification encoding bits 25 are arranged in groups, and the number of black etching stripes continuously arranged in each group is smaller than the first preset number, so that it is beneficial to accurately distinguish the initial segment encoding bits 23 and the unit identification encoding bits 25 when the linear image sensor 30 performs image recognition.

In an alternative specific example, the third preset number is 9 bits, and in the unit identification coding bit 25, adjacent groups of black etching stripes are separated by a spacing coding bit 26, and in this embodiment, the spacing coding bit 26 in the unit identification coding bit 25 is a white transparent etching-free stripe. The black etched stripes in the unit identification coded bits 25 are grouped by adopting white transparent non-etched stripes, so that the number of coded bits contained in the initial segment coded bits 23 is larger than the number of black etched stripes continuously arranged in each group in the unit identification coded bits 25, and confusion between the third preset number of unit identification coded bits 25 and the first preset number of initial segment coded bits 23 can be avoided in the image identification process.

In some embodiments, the number of consecutively arranged black etched stripes in each set is no greater than 5 bits, and the first predetermined number is 6 bits. In an alternative example, each coding unit 21 includes 20 bits, 1bit corresponds to a black etched stripe or white transparent non-etched stripe of standard width on the absolute value coding scale 20, the black etched stripe corresponds to a coding bit of bit0, and the white transparent non-etched stripe corresponds to a coding bit of bit1. The first 8 bits of each coding unit 21 are identical bit bits, wherein the first 8 bits comprise a 6-bit initial segment coding bit 23, and correspond to 6 black etched stripes which are arranged in series in front of the coding units 21 on the absolute value coding scale 20, so as to mark the unified initial position of one coding unit 21, the first 8 bits comprise 1-bit fixed coding bit 24, correspond to 1 white transparent non-etched stripe on the absolute value coding scale 20, and provide identical spot characteristics for the subsequent extraction of sub-pixel centroids, and then the fixed coding bit 24 and the unit identification coding bit 25 are separated by adopting 1bit corresponding to 1 black etched stripe, so that the accurate position of the white transparent non-etched stripe of the sub-pixel centroids can be more conveniently extracted, and the first 8 bit bits of each coding unit 21 are identical, such as 0b00000010.

In some embodiments, each code bit corresponds to 3-6 pixels in an image imaged by the linear image sensor, and each code bit corresponds to a standard width stripe of 30-100 um. Still taking each coding unit 21 as an example including 20bit coding bits, a single coding unit 21 can support a measurement range of 2mm, and the unit identification coding includes 9 bit bits, so that a total of 512 effective values from 0b000000000 to 0b111111111 can be realized, and thus 512 coding units 21 can be correspondingly distinguished, and effective measurement within a range of 1024mm can be realized. In order to avoid confusion between the unit identification codes of 9 bits and the initial section codes of 6 bits, the unit identification codes of 9 bits are divided into two groups, white transparent etching-free stripes are adopted between the two groups to separate, and the longest continuous coding length in each group is 5 bits. In the example shown in fig. 3, each of the encoding units 21 includes 20bit encoding bits including 6 black bit encoding bits as the start segment encoding bits 23,1 bit encoding bit for the sub-pixel centroid extraction position, 1 bit encoding bit as the black interval bit, 9 bit encoding bits for the unit identification encoding, and 3 bit encoding bits as the white interval bit, whereby each of the encoding units 21 removes a plurality of identical bit encoding bits and bit encoding bits for the interval in front of each of the encoding units 21, and 9 unit identification encoding identifiers such as (0 b 011010010) can be used.

Referring again to fig. 3, in some embodiments, the light source assembly 10 includes an LED light source 11, a lens set disposed between the LED light source 11 and the absolute value encoding scale 20, and the lens set reflects and refracts the outgoing light of the LED light source 11 to form a parallel expanded beam directed to the absolute value encoding scale 20. The LED light source 11 may be a high-brightness LED, for example, a high-brightness LED product with a uniform divergence angle of the fast axis and the slow axis. The lens group reflects and refracts the light beam emitted from the LED light source 11 to finally form a parallel light beam having uniform brightness and an emission range satisfying the demand.

Optionally, the lens group includes a single lens 12, a reflecting mirror 13 and a wedge-shaped mirror 14, the single lens 12 is a plano-convex spherical lens, the single lens 12 changes the emergent light of the LED light source 11 into parallel light beams with a first diameter, the reflecting mirror 13 totally reflects the emergent light of the single lens 12 to form parallel light beams with a second diameter, the wedge-shaped mirror 14 transmits the light reflected by the reflecting mirror 13 to form parallel light beams with a third diameter and uniform brightness, and the third diameter is larger than the second diameter, and the second diameter is larger than the first diameter. The lens material of the single lens 12 may be optical glass or optical plastic, and after passing through the single lens 12, the light beam becomes parallel light with a diameter of about 3-6 mm. The reflecting mirror 13 can adopt a high-reflectivity dielectric film or high-refractive index glass, and the diameter of a light spot can be increased to 5-10mm and still be a parallel light beam after reflection by utilizing the principle of large-angle incidence total reflection. The parallel light beam after passing through the reflecting mirror 13 is obliquely incident on the wedge-shaped mirror 14, the wedge-shaped mirror 14 can further enlarge the diameter of the light spot to 6-12mm, the light spot is kept as the parallel light beam, and the wide spectral characteristic of the LED light source 11 is utilized to homogenize the brightness space distribution of the light spot and prevent the formation of similar laser speckles. Thus, by the lens group, a parallel light beam having a uniform brightness and a vertical width of 6-12mm (height of 3-6mm in the direction perpendicular to the paper surface) can be finally formed, and the divergence angle of the parallel light beam in the vertical direction is smaller than 2mrad. The absolute value coding scale 20 for illuminating the synchronous motion following the object to be measured and finally forming the stripe with alternate brightness and darkness on the linear image sensor 30 CMOS.

Referring to fig. 5, in another aspect of the present application, there is provided a ranging method of a contact displacement sensor, including:

S101, acquiring an image of the irradiation light acquired by the linear image sensor and transmitted through the absolute value coding scale.

S103, extracting gray information of pixels in the image, calculating the full width at half maximum of the black etching stripes to identify the coding bit of the initial segment, and determining the position of the target coding unit in the image.

S105, extracting information of unit identification coding bits contained in the target coding unit based on the position of the target coding unit to determine a unit number code of the target coding unit, and calculating a fuzzy position based on the measurable range of the coding unit and the unit number code.

S107, based on the position of the target coding unit, extracting the information of the fixed coding bit contained in the target coding unit to determine the sub-pixel centroid position corresponding to the fixed coding bit, and calculating the accurate position by using the sub-pixel centroid position.

And S109, obtaining the current motion displacement according to the fuzzy position and the accurate position.

The contact type displacement sensor is rigidly connected to the measurement target by the absolute value encoding scale 20 and moves up and down along with the measurement target during the ranging process. The absolute value coding scale 20 in the moving process is imaged by the linear image sensor 30, and the characteristic of good consistency of pixel intervals of the linear image sensor 30 can be used as a fixed grating and a detection element in the contact displacement sensor.

Because the absolute value coding scale 20 can move up and down, the linear image sensor 30 receives the imaging of the light source in the process of moving up and down through the standard width stripes with alternate black and white, determines the approximate displacement according to the mark of the coding unit 21 in the current imaging, and determines the accurate position according to the sub-pixel centroid position of the white transparent etching-free stripes corresponding to the fixed coding bits 24 in the coding unit 21. In an alternative example, the ranging method mainly includes:

first, gradation information (Gray Value) of each pixel (pixel) of the Linear image sensor 30 (Linear CMOS) is extracted.

The full width at Half Maximum (HMFW) of each black etch stripe is calculated, the maximum near the center of the CMOS is found, corresponding to 6 bits (also the widest black etch stripe), and the cell start pixel position is determined.

According to the initial pixel position of the unit, the pixel gray value corresponding to the bit coding bit contained in the coding unit 21 is read, the corresponding value of each bit coding bit is determined to be 0/1 according to the total gray value, the 9bit coding unit 21 identification is finally obtained through combination, the unit number is determined, and the approximate position is determined according to the unit number coding. If 0b011010010 corresponds to 10 system 210 and the cell width is 2mm, then the corresponding cell position is 420mm.

The sub-pixel position of the present coding unit 21 is extracted based on the unit start position. The sub-pixel extraction algorithm may be a conventional centroid method, for example, the sub-pixel centroid position is 248.46, corresponding to the accurate position 0.8535mm.

The final position is the cell position plus the exact position, such as 420.8535mm in the example.

The contact type displacement sensor and the distance measuring method thereof provided by the embodiment of the application have the following characteristics:

firstly, an absolute value coding graduated scale 20 is designed, a plurality of coding units 21 are arranged on the absolute value coding graduated scale 20, and the initial section of each coding unit 21 adopts 6 fixed black stripe marks, so that the MCU (single chip microcomputer) can be helped to rapidly extract and identify the whole unit.

Second, the combination of reflection method and refraction method can realize uniform and parallel irradiation light, which is beneficial to ensuring the imaging quality of black-white interval stripes.

Thirdly, the unit coding of the graduated scale of absolute value coding realizes binary system by using standard width stripes with equal width and black and white, so that the number of effective coding units 21 can be up to 2-9, and the effective measurement in 1024mm can be realized under the condition that the measurable range of a single unit is 2 mm.

Fourth, the coding unit 21 of the absolute value coding scale 20 is broken by setting white standard width stripes at specific positions, so that the starting section of the coding unit 21 is effectively distinguished to adopt fixed 6 black standard width stripe marks, and the position of the area of the whole coding unit 21 is favorably and rapidly identified.

Fifth, in the single coding unit 21 in the absolute value coding scale 20, 1 standard white standard width stripe is used for sub-pixel centroid extraction, and the centroid of the spot with a specific width is extracted, so that the consistency and precision of sub-pixel centroid extraction can be ensured.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

From the above description of the embodiments, it will be clear to those skilled in the art that the above-described embodiment method may be implemented by means of software plus a necessary general hardware platform, but of course may also be implemented by means of hardware, but in many cases the former is a preferred embodiment. Based on such understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium (e.g. ROM/RAM, magnetic disk, optical disk) comprising several instructions for causing a terminal (which may be a mobile phone, a computer, a server, or a network device, etc.) to perform the method of the various embodiments of the present invention.

The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any person skilled in the art will readily appreciate variations or alternatives within the scope of the present application. Therefore, the protection scope of the application is subject to the protection scope of the claims.

Claims (6)

1. A contact type displacement sensor, characterized by comprising the following steps:

a light source assembly for providing illumination light;

the absolute value coding graduated scale is fixedly connected with a measuring target relatively and synchronously moves with the measuring target, a plurality of coding units are arranged on the absolute value coding graduated scale, each coding unit comprises a plurality of coding bits represented by standard width stripes, and each coding bit comprises a starting section coding bit, a fixed coding bit and a unit identification coding bit;

A linear image sensor for acquiring an image of the illumination light transmitted through the absolute value encoding scale; the linear image sensor is used for extracting the information of the unit identification coding bit contained in the target coding unit based on the position of the target coding unit, so as to determine the unit number coding of the target coding unit, calculating the fuzzy position based on the measurable range of the coding unit and the unit number coding, extracting the information of the fixed coding bit contained in the target coding unit based on the position of the target coding unit, so as to determine the sub-pixel centroid position corresponding to the fixed coding bit, and calculating the accurate position by utilizing the sub-pixel centroid position;

Each coding bit corresponds to a set number of pixels in an image imaged by the linear image sensor, each coding bit corresponds to standard width stripes of 30-100 um, and the set number is 3-6;

The light source assembly comprises an LED light source and a lens group arranged between the LED light source and the absolute value coding scale, wherein the lens group reflects and refracts emergent light rays of the LED light source to form parallel beam expanding light beams which irradiate the absolute value coding scale, the lens group comprises a single lens, a reflecting mirror and a wedge-shaped mirror, the single lens is a plano-convex ball lens, the single lens changes the emergent light rays of the LED light source into parallel light beams with a first diameter, the reflecting mirror totally reflects the emergent light rays of the single lens to form parallel light beams with a second diameter, the wedge-shaped mirror transmits the light rays reflected by the reflecting mirror to form parallel light beams with a third diameter and uniform brightness, and the third diameter is larger than the second diameter and the second diameter is larger than the first diameter;

Each coding unit corresponds to a measurable range of 2mm, 9 coding bits are included in the unit identification coding bits, and effective measurement within a 1024mm range can be realized.

2. The touch displacement sensor of claim 1, wherein the standard width stripe is a black etched stripe or a white transparent non-etched stripe.

3. The touch displacement sensor of claim 1, wherein the start segment code bits comprise a first predetermined number of black etched stripes arranged in succession;

the fixed coding bits comprise a second preset number of white transparent etching-free stripes;

The unit identification coding bits comprise a third preset number of black etching stripes which are arranged in groups, and the number of the black etching stripes which are continuously arranged in each group is smaller than the first preset number.

4. A touch displacement sensor according to claim 3, wherein the third predetermined number is 9 bits;

And in the unit identification coding bit, a white transparent etching-free stripe interval is arranged between adjacent groups of the black etching stripes.

5. A touch sensor as recited in claim 3, wherein the number of black etched stripes arranged consecutively in each group is no more than 5 bits, and the first predetermined number is 6 bits.

6. A distance measurement method based on the contact displacement sensor according to any one of claims 1 to 5, comprising:

Acquiring an image of the irradiation light acquired by the linear image sensor and transmitted through the absolute value coding scale;

Extracting gray information of pixels in the image, calculating the full width at half maximum of black etching stripes to identify initial segment coding bits, and determining the position of a target coding unit in the image;

Extracting information of unit identification coding bits contained in the target coding unit based on the position of the target coding unit to determine a unit number code of the target coding unit, and calculating a fuzzy position based on a measurable range of the coding unit and the unit number code;

Based on the position of the target coding unit, extracting information of a fixed coding bit contained in the target coding unit to determine a sub-pixel centroid position corresponding to the fixed coding bit, and calculating an accurate position by using the sub-pixel centroid position;

And obtaining the current motion displacement according to the fuzzy position and the accurate position.