CN203869666U - Macro-micro composite raster ruler measuring system based on vertical and horizontal conversion, amplification and subdivision - Google Patents

Abstract

The utility model relates to the field of optical length measurement, in particular to a macro-micro composite grating ruler measurement system based on vertical and horizontal conversion, amplification and subdivision, and a macro-micro composite grating ruler measurement system based on vertical and horizontal conversion, amplification and subdivision. Mobile macro-micro reading system and counting and image processing module. The macro-micro reading system is placed directly against the grating base surface and parallel to the grating scale. The processing module superimposes to form a superimposed image, and the measurement reference line forms a certain angle θ with the grating. Through the above structure, the utility model can be compatible with existing incremental and absolute types of grating rulers, and has strong applicability. It uses high-speed and low-precision grating rulers for macro-scale displacement measurement, and at the same time uses high-efficiency micro-scale reading modules based on mechanical optics. Subdivision technology is used to obtain reliable high-precision micro-scale displacement values, which is suitable for grating rulers with large pitch sizes and low cost.

Description

Macro-micro-composite grating ruler measurement system based on vertical and horizontal conversion, magnification and subdivision

count field

The utility model relates to the field of optical length measurement, in particular to a macro-micro composite grating ruler measurement system based on vertical and horizontal conversion, amplification and subdivision.

background count

The grating ruler is a measurement feedback device that uses the optical principle of the grating. It is one of the commonly used detection devices in the closed-loop position control system, especially in the field of precision processing and manufacturing. The basic principle of grating ruler measurement is: the relative movement between the scale and the scanning mask forms moiré fringes under the illumination of the light source, and the moiré fringes are converted into approximate sine and cosine electrical signals by photoelectric sensors, which is the original grating scanning signal. Then use different electronic subdivision methods to obtain counting pulse signals with different measurement steps. The pulse signals are generally two-way orthogonal signals. The step distance is the displacement measurement value of the grating ruler.

In order to improve the accuracy of displacement measurement, it is usually necessary to increase the density of grating lines, which will increase the amount of signal acquisition data. Especially in occasions requiring high speed and high precision, a high signal acquisition frequency is required, resulting in a large amount of signal acquisition data. This leads to the higher the measurement accuracy of the grating ruler, the lower the upper limit of its allowable measurement speed, which cannot meet the requirements of high-speed and high-precision measurement.

At present, the common grating scales on the market mainly use "Moiré fringes", and cooperate with detection and data processing modules such as electronic subdivision to obtain displacement values. The existing general-purpose grating ruler measurement system mainly has the following problems: in order to only improve the displacement measurement accuracy, it is often necessary to use a denser grid. The denser grid leads to an increase in the amount of data collected per unit displacement, which increases the phenomenon of "lost steps" in the data collection process and reduces the credibility of the data. Especially in the state of high-speed movement, the phenomenon of "lost step" will be more obvious. Blindly adopting devices with higher acquisition speeds will lead to a significant increase in the cost of the measurement system.

Patent CN200510010288.1 proposes a high-speed and high-precision displacement measurement method based on dual grating rulers. Its core idea is: the speed of the usual high-speed and high-precision positioning system is not high at the time of positioning, so it uses two grating rulers with different performances to complete the displacement measurement: a grating ruler suitable for high-speed and low-resolution measurement Coarse grating ruler. A grating ruler suitable for low-speed, high-resolution measurement). When the system moves from high speed to low speed, the counting pulses of the dual grating scales are switched, and the counting values are synthesized to obtain high-resolution displacement measurement values at the positioning moment. In its specific counting scheme, the switching speed threshold is set, and the displacement and speed are detected by the coarse grating ruler at high speed. When the speed is lower than the set threshold, the motion displacement is detected by the fine grating scale. This patent realizes the high-speed and high-precision displacement detection of the grating ruler. Its disadvantages are: 1. It does not realize the high-speed and high-precision displacement detection of the grating ruler in the whole process, and its application range is limited; 2. It uses two sets of grating rulers, and the cost is relatively high.

Utility model content

The utility model proposes a macro-micro composite grating ruler, which takes into account the high-speed and high-precision requirements of displacement measurement, and improves the displacement measurement accuracy with low cost under the premise of ensuring high measurement speed.

For this purpose, the utility model adopts the following counting scheme:

The macro-micro composite grating ruler measurement system based on vertical and horizontal conversion, zooming and subdivision includes a grating ruler, a macro-micro reading system that can move relative to the grating ruler, and a counting and image processing module.

The macro-micro reading system includes a macro-scale reading module and a micro-scale reading module, the positions of the macro-scale reading module and the micro-scale reading module are relatively fixed, and the surface of the grating ruler is provided with a grating band composed of grating lines, so The macro-micro reading system is facing the grating base surface and placed parallel to the grating ruler, and the macro-micro reading system is kept at a certain distance from the grating ruler;

The macro-scale reading module and the micro-scale reading module are connected to the counting and image processing module through a communication cable; the micro-scale reading module includes an image sensor and a lens, and the lens is placed on the front of the image sensor;

It also includes a measurement reference straight line, the measurement reference straight line is a straight line or a plurality of parallel straight line groups, the measurement reference straight line and the grating acquired by the image sensor are superimposed and formed in the counting and image processing module A superimposed image, on which the measurement reference line forms a certain angle θ with the grating.

The measurement reference straight line is a reticle set on the lens.

The measurement reference straight line is set in the counting and image processing module.

It also includes an auxiliary light source facing the range of action of the image sensor, which is fixed to the image sensor; the grating ruler is installed on a fixed frame, and the macro-micro reading system is fixed to the moving parts; the macro-micro reading system and The distance between the grating rulers is 0.5mm to 1.5mm.

The included angle θ satisfies the relationship of tanθ=W/B, wherein W is the grating pitch of the grating ruler, and B is the width of the grating strip.

The image sensor is a CCD or CMOS camera.

The macro-scale reading module is a grating ruler reading head with reflective structure Moiré fringe technology measurement principle, or a photoelectric sensing element that directly scans the grating.

Through the above structure, the utility model can be compatible with existing incremental and absolute types of grating rulers, and has strong applicability. It uses high-speed and low-precision grating rulers for macro-scale displacement measurement, and at the same time uses high-efficiency micro-scale reading modules based on mechanical optics. Subdivided counting to obtain reliable high-precision micro-scale displacement values, suitable for grating rulers with large pitch sizes, and low cost. In particular, the measurement system proposed by the utility model can also perform image processing on multiple gratings to further average the manufacturing errors of the gratings, and further improve the displacement measurement accuracy.

Description of drawings

Fig. 1 is a structural representation of an example of the utility model.

Fig. 2 is a schematic diagram of a superimposed image of a measurement reference line and a grid pattern acquired by an image sensor of an example of the present invention.

Fig. 3 is a schematic diagram of superimposed images of a plurality of measurement reference lines and grating lines obtained in an example of the present invention.

Fig. 4 is a schematic diagram of the included angle between lens reticles and grating lines in an example of the present invention.

Fig. 5 is the measurement schematic diagram of an example of the utility model

Among them: grating ruler 1, grating pattern 101, macro-micro reading system 2, macro-scale reading module 201, image sensor 202, lens 203, measurement reference line 204a, intersection point 204b, and reticle 205.

Detailed ways

The counting scheme of the present utility model will be further described below in conjunction with the accompanying drawings and through specific implementation methods.

As shown in Figure 1, the macro-micro composite grating scale measurement system based on vertical and horizontal conversion, amplification and subdivision includes a grating scale 1, a macro-micro reading system 2 that can move relative to the grating scale 1, and a counting and image processing module.

As shown in Figure 1, the macro-micro reading system 2 includes a macro-scale reading module 201 and a micro-scale reading module, the positions of the macro-scale reading module and the micro-scale reading module are relatively fixed, and the surface of the grating ruler 1 is provided with a The grating belt composed of grating 101, the macro-micro reading system 2 is facing the base surface of the grating 101 and placed parallel to the grating scale 1, and the macro-micro reading system 2 and the grating scale 1 are kept at a certain distance. distance;

The macro-scale reading module 201 and the micro-scale reading module are connected to the counting and image processing module through a communication cable; as shown in Figure 1, the micro-scale reading module includes an image sensor 202 and a lens 203, and the lens 203 is placed the front side of the image sensor 202;

As shown in FIG. 2 or FIG. 3 , it also includes a measurement reference straight line 204a, the measurement reference straight line 204a is a straight line or a plurality of parallel straight line groups, and the measurement reference straight line 204a is the same as the image sensor 202 acquired. The grating 101 is superimposed in the counting and image processing module to form a superimposed image, and on the superimposed image, the measurement reference line 204 a forms a certain angle θ with the grating 101 .

As shown in FIG. 2 or FIG. 3 , the counting and image processing module identifies the superimposed image, and determines the center line equation of the grating pattern 101 and the measurement reference straight line 204a. There is an included angle θ between the center line of the grid pattern 101 and the measurement reference straight line 204a, ensuring that the center line equation has an intersection point 204b. When the positions of the grating scale 1 and the macro-micro reading system 2 are displaced relative to each other, the position of the intersection point 204b will move relative to the center line of the measurement reference line 204a. The proportional relationship of its moving distance is Wherein Δs is the relative displacement between the grating ruler 1 and the macro-micro reading system 2, Δl is the superimposed image of the measurement reference line 204a and the grating 101 acquired by the counting and image processing module, the The position of the intersection point 204b will be measured along the relative movement amount of the center line of the reference line 204a.

The measurement reference straight line 204a contained in the counting and image processing module is obtained by the following methods: A. physical method: as shown in Figure 4, the lens 203 is provided with a slender reticle 205 or multiple parallel reticles 205, the line direction of the line 205 or line group forms a certain angle θ with the direction of the grating 101, and the image of the measurement reference line 204a included in the counting and image processing module is the The reticle 205 image of the camera lens 203 that image sensor 202 obtains; B. software method: described counting and image processing module carry out image processing to the image of grating 101 that described image sensor 202 obtains, and described counting and image processing module are built-in There is a straight line generation algorithm to generate a straight line or a group of parallel straight lines forming an angle θ with the length direction of the grid pattern 101, and the image of the measurement reference straight line 204a included in the counting and image processing module is the straight line or group of straight lines generated by the built-in algorithm image.

It also includes an auxiliary light source facing the range of action of the image sensor 202, which is fixed to the image sensor 202 and can move synchronously with the image sensor 202. The irradiation range of the auxiliary light source is concentrated on the image processing of the image sensor 202 The area provides illumination light for the image sensor 202, so that the image sensor 202 can obtain high-quality images.

The grating ruler 1 is installed on a fixed frame, and the macro-micro reading system 2 is fixed on moving parts.

The distance between the macro-micro reading system 2 and the grating ruler 1 is 0.5 mm to 1.5 mm.

The included angle θ satisfies the relationship of tanθ=W/B, wherein W is the pitch size of the grating ruler 1, and B is the width dimension of the grating band. Through this proportional relationship, the grating ruler 1 can be improved. Dimensional measurement accuracy within a unit pitch.

The image sensor 202 is a CCD or CMOS camera.

The macro-scale reading module 201 is a grating reading head based on the measurement principle of Moiré fringe technology with a reflective structure, or a photoelectric sensor element that directly scans the grating 101 .

The measurement method of the macro-micro composite grating ruler measurement system based on vertical and horizontal conversion, amplification and subdivision:

A. The macro-scale reading module 201 uses the principle of "Moiré fringes" or a photosensitive element to count the grid stripes 101 passing through during the relative movement, and the counting and image processing module counts the number of pulses counted by the grid stripes 101 and The grid pitch is multiplied to obtain the macro-scale displacement value of a unit pitch accuracy level;

B. The image sensor 202 in the micro-scale reading module acquires the image of the grating 101 and superimposes it with the image of the measurement reference line 204a in the counting and image processing module. The counting and image processing module performs image processing on the superimposed image, and acquires the reference central line equation 1 of the grating pattern in the image of the grating pattern 101 and the reference central line equation 2 of the measurement reference straight line. The counting and image processing module calculates the coordinates of the intersection point 204b of the reference center line equation 1 and the reference center line equation 2. Select an initial intersection point P0, as shown in Figure 5, when the relative displacement occurs between the macro-micro reading system 2 and the grating scale 1, the intersection point 204b of the reference center line equation 1 and the reference center line equation 2 is in the A movement occurs on the datum center line equation 2, and the intersection point after the movement is set as P1. The counting and image processing module calculates the moving distance between points P0 and P1, and sets the moving distance as L0. pass The proportional relationship, counting and image processing module obtains the microscale relative displacement s between the macro and micro reading system 2 and the grating ruler 1 within a unit pitch size range. The displacement s is a high-precision microscale displacement value within a unit pitch size range. When the reference center line equation 1 and the reference center line equation 2 form an intersection group, the counting and image processing module obtains multiple sets of micro-scale relative displacement measurement values, and the counting and image processing module takes the measured average value as the final micro-scale displacement value. The micro-scale reading module performs cyclic measurement of the displacement within the single pitch range of the grating ruler 1, and does not perform cumulative measurement of displacement values of multiple grid sizes;

C. The counting and image processing module separates the relative displacement between the macro-micro reading system 2 and the grating ruler 1 into the macro-scale displacement of an integer multiple of the grid pitch size and the micro-scale displacement of less than one unit of the grid pitch size. . Wherein, the macro-scale displacement of an integer multiple grating pitch size is obtained by multiplying the integer grating count pulse number and the grating pitch, and the micro-scale displacement within a unit pitch size is obtained by the image analysis method. Through the macro-micro composite of the displacement values obtained by the above two reading modules, the macro-micro composite dual-reading head grating ruler system proposed by the utility model can obtain high-precision displacement values at high speed.

Preferably, the range of the image processing area detected and processed by the counting and image processing module is limited to an elongated strip-shaped area with the measurement reference straight line 204a as the center line.

The image processing speed of the counting and image processing module is inversely proportional to the number of pixels contained in the image to be processed. The smaller the range of the image processing area, the higher the image processing speed. This technical solution can greatly improve the image processing speed .

Through the above structure, the utility model can be compatible with existing incremental and absolute types of grating rulers, and has strong applicability. It uses high-speed and low-precision grating rulers for macro-scale displacement measurement, and at the same time uses high-efficiency micro-scale reading modules based on mechanical optics. Subdivided counting to obtain reliable high-precision micro-scale displacement values, suitable for grating rulers with large pitch sizes, and low cost. In particular, the measurement system proposed by the utility model can also perform image processing on multiple gratings to further average the manufacturing errors of the gratings, and further improve the displacement measurement accuracy.

The counting principle of the present utility model has been described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the utility model, and cannot be construed as limiting the protection scope of the utility model in any way. Based on the explanations here, counters in the field can think of other specific implementations of the utility model without creative work, and these modes will all fall within the protection scope of the utility model.

Claims (9)

1. based on conversion in length and breadth, amplify grand micro-composite grating chi measuring system of segmentation, comprise grating scale, the grand micro-frame of reference and counting and the image processing module that can relatively described grating scale relatively move, it is characterized in that:

Described grand micro-frame of reference includes grand yardstick reading module and microscale reading module, described grand yardstick reading module is relative fixing with microscale reading module position, described grating scale surface is provided with the grid line band being comprised of grid line, described grand micro-frame of reference over against described grid line basal plane and with the parallel placement of described grating scale, described grand micro-frame of reference and described grating scale keep certain distance;

Described grand yardstick reading module is connected with counting and image processing module by telecommunication cable with microscale reading module; Described microscale reading module includes imageing sensor and camera lens, and described camera lens is placed in the front of described imageing sensor;

Also comprise witness mark straight line, described witness mark straight line is straight line or many straight line groups that are parallel to each other, the described grid line that described witness mark straight line and described imageing sensor obtain superposes and forms superimposed image in described counting and image processing module, on described superimposed image, described witness mark straight line and described grid line form certain angle theta.

2. the grand micro-composite grating chi measuring system based on conversion amplification is segmented in length and breadth according to claim 1, is characterized in that: described witness mark straight line is the groove of being located on described camera lens.

3. the grand micro-composite grating chi measuring system based on conversion amplification is segmented in length and breadth according to claim 1, is characterized in that: described witness mark straight line is located at described counting and image processing module.

4. the grand micro-composite grating chi measuring system based on conversion amplification is segmented in length and breadth according to claim 1, is characterized in that: also comprise the secondary light source towards described imageing sensor reach, it is fixed on described imageing sensor.

5. the grand micro-composite grating chi measuring system based on conversion amplification is segmented in length and breadth according to claim 1, is characterized in that: described grating scale is arranged on fixed frame, and described grand micro-frame of reference is fixed on moving component.

6. the grand micro-composite grating chi measuring system based on conversion amplification is segmented in length and breadth according to claim 1, is characterized in that: the distance between described grand micro-frame of reference and described grating scale is that 0.5mm is to 1.5mm.

7. according to claim 1 based on changing in length and breadth grand micro-composite grating chi measuring system of amplifying segmentation, it is characterized in that: described angle theta meets the relation of tan θ=W/B, the pitch size that wherein W is described grating scale, B is the width dimensions of described grid line band.

8. the grand micro-composite grating chi measuring system based on conversion amplification is segmented in length and breadth according to claim 1, is characterized in that: described imageing sensor is CCD or CMOS camera.

9. according to claim 1 based on changing in length and breadth grand micro-composite grating chi measuring system of amplifying segmentation, it is characterized in that: the grating ruler reading head of the Moire fringe technology measuring principle that described grand yardstick reading module is reflective structure, or for directly described grid line being carried out the photo electric sensitive element of scanning technique.