A device and method for measuring the side profile of a conical workpiece

Abstract

The present invention discloses a device and method for measuring the side profile of a conical workpiece, and belongs to the field of photoelectric testing. The device for measuring the side profile of a conical workpiece includes a cylindrical light source, a collimating lens, a reflector, a digital micromirror device, and a surface array CCD. The micromirror element array of the digital micromirror device is controlled to present a horizontal reflection slit; the surface array CCD receives parallel light that is not blocked by the side of the conical workpiece and records data. Compared with the prior art, the device for measuring the side profile of a conical workpiece provided by the present invention is not limited by the minimum change in the rotation angle of the reflector, and the displacement scanning is linear, and the scanning accuracy is effectively improved.

Description

Technical Field

[0001] The invention relates to a device and method for measuring the side profile of a conical workpiece, and belongs to the field of photoelectric testing. Background Art

[0002] Conical workpieces are widely used in the equipment manufacturing industry, such as turned parts, positioning fixtures, etc., and their contour measurement is required to ensure product quality. The commonly used method is to perform line scanning on the conical workpiece and change the position of the scanning line on the workpiece by controlling the rotation angle of the reflector. The scanning accuracy of this method is limited by the minimum change in the rotation angle of the reflector, and the displacement scanning rate is nonlinear. Summary of the invention

[0003] In view of the above-mentioned prior art, the present invention provides a device and method for measuring the side profile of a conical workpiece to solve the above-mentioned problems.

[0004] The technical solution for realizing a conical workpiece side profile measuring device of the present invention is that the device comprises a cylindrical light source, a collimating lens, a reflector, a digital micromirror device and a surface array CCD.

[0005] The cylindrical light source passes through the focus of the collimating lens and is placed horizontally; the collimating lens is a cylindrical lens, which collimates the light from the cylindrical light source into parallel light; the reflector reflects the parallel light onto the digital micromirror device; the digital micromirror device is composed of a base surface and a two-dimensional micromirror element array; the micromirror element has two flip states, on and off. When it is in the on state, the micromirror element deflects +12°, and the incident light is reflected by the digital micromirror device to the side of the conical workpiece; when it is in the off state, the micromirror element deflects -12°, and the incident light wave is reflected out of the device by the digital micromirror device; the micromirror element array of the digital micromirror device is controlled to present a horizontal reflection slit; the area array CCD receives parallel light that is not blocked by the side of the conical workpiece and records data.

[0006] The present invention provides a method for measuring the side profile of a conical workpiece, which uses the above-mentioned device for measuring the side profile of a conical workpiece and follows the following steps:

[0007] Step 1: Power on the cylindrical light source to emit cylindrical waves through photoelectric conversion.

[0008] Step 2: The cylindrical wave is converted into a plane wave through the collimating lens and reflected onto the digital micromirror device through a reflector.

[0009] Step 3: Give the micromirror element array of the digital micromirror device an initial flip state, in which there is a horizontal reflective slit in the on state.

[0010] Step 4: at the next moment, the reflection slit is translated step by step, and the translation amount is the unit row of the micromirror element array of the digital micromirror device; the area array CCD receives the parallel light that is not blocked by the side of the conical workpiece, and records the two-point data of the side profile of the conical workpiece at the current time sequence n and

[0011] Step 5. After collecting two sets of point data on both sides in turn, use the least squares method to perform straight line fitting on the two sets of data to complete the side profile measurement of the conical workpiece; the straight line equations are:

[0012]

[0013] The number of measurement points obtained in each group is N, and the coefficients of the linear equation are calculated as follows:

[0014]

[0015]

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The conical workpiece side profile measurement device and method provided by the present invention utilize a digital micromirror device to step and translate the reflection slit to complete the conical workpiece profile scanning measurement. Compared with the prior art, the conical workpiece side profile measurement device provided by the present invention is not limited to the minimum change in the rotation angle of the reflector, and the displacement scanning is linear, and the scanning accuracy is effectively improved. The conical workpiece side profile measurement method provided by the present invention uses the least squares motion to fit the side profile edge line, and the measurement accuracy can reach the sub-pixel level. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A structural diagram of a conical workpiece side profile measuring device provided by the present invention;

[0019] Figure 2 This is a schematic diagram of scanning measurement of the present invention.

[0020] In the figure: 1- cylindrical light source, 2- collimating lens, 3- reflector, 4- digital micromirror device, 5- conical workpiece, 6- array CCD. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with specific implementation modes.

[0022] like Figure 1 As shown, a device for measuring the side profile of a conical workpiece of the present invention comprises a cylindrical light source 1, a collimating lens 2, a reflector 3, a digital micromirror device 4 and an area array CCD 6.

[0023] The cylindrical light source 1 passes through the focus of the collimating lens 2 and is placed horizontally; the collimating lens 2 is a cylindrical lens, which collimates the light from the cylindrical light source into parallel light; the reflector 3 reflects the parallel light onto the digital micromirror device 4; the digital micromirror device 4 is composed of a base surface and a two-dimensional micromirror element array; the micromirror element has two flip states, on and off. When it is in the on state, the micromirror element deflects +12°, and the incident light is reflected by the digital micromirror device 4 to the side of the conical workpiece 5. When it is in the off state, the micromirror element deflects -12°, and the incident light wave is reflected out of the device by the digital micromirror device 4; the micromirror element array of the digital micromirror device 4 is controlled to present a horizontal reflection slit; the area array CCD6 receives parallel light that is not blocked by the side of the conical workpiece and records data.

[0024] like Figure 2 As shown, a method for measuring the side profile of a conical workpiece proposed by the present invention uses the above-mentioned device for measuring the side profile of a conical workpiece and follows the following steps:

[0025] Step 1: Power on the cylindrical light source 1 to emit cylindrical waves through photoelectric conversion.

[0026] Step 2: The cylindrical wave is converted into a plane wave by the collimating lens 2 and reflected to the digital micromirror device 4 by the reflector 3.

[0027] Step 3: The micromirror element array of the digital micromirror device 4 is initially flipped to a state in which there is a horizontal reflective slit in an on state.

[0028] Step 4: At the next moment, the reflection slit is translated step by step, and the translation amount is the unit row of the micromirror element array of the digital micromirror device 4; the area array CCD6 receives the parallel light that is not blocked by the side of the conical workpiece 5, and records the two-point data of the side profile of the conical workpiece 5 at the current time sequence n and

[0029] Step 5. After collecting two sets of point data on both sides in turn, use the least squares method to perform straight line fitting on the two sets of data to complete the 5-side profile measurement of the conical workpiece. The straight line equations are:

[0030]

[0031] The number of measurement points obtained in each group is N, and the coefficients of the linear equation are calculated as follows:

[0032]

[0033]

[0034] Example:

[0035] The present invention is further described in detail below by taking a conical workpiece with a bottom diameter of 3 mm and a height of 5 mm as an example:

[0036] A cylindrical light source 1 with a length greater than 3 mm is selected, the surface size of the digital micromirror device 4 is 20 mm×10 mm, and the size of the area array CCD 6 is the same as that of the digital micromirror device 6 .

[0037] The size of the micromirror element of the digital micromirror device 4 is 7.6um×7.6um, so the line width of the scanning light passing through the reflection slit is 7.6um, and the area array CCD records two groups of 658 contour points each, that is, N=658.

[0038] According to the least squares accuracy estimation, the measurement accuracy is within 0.02um.

[0039] Although the present invention has been described above in conjunction with the drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many modifications without departing from the purpose of the present invention, all of which are within the protection of the present invention.

Claims

1. A device for measuring the side profile of a conical workpiece, characterized in that: It comprises a cylindrical light source (1), a collimating lens (2), a reflector (3), a digital micromirror device (4) and an area array CCD (6); The cylindrical light source (1) passes through the focus of the collimating lens (2) and is placed horizontally; the collimating lens (2) is a cylindrical lens, which collimates the light from the cylindrical light source into parallel light; the reflector (3) reflects the parallel light onto the digital micromirror device (4); the digital micromirror device (4) is composed of a base surface and a two-dimensional micromirror element array; the micromirror element has two flip states, on and off; when in the on state, the micromirror element deflects +12°, and the incident light is reflected by the digital micromirror device (4) to the side of the conical workpiece (5); when in the off state, the micromirror element deflects -12°, and the incident light wave is reflected out of the device by the digital micromirror device (4); the micromirror element array of the digital micromirror device (4) is controlled to present a horizontal reflection slit; the surface array CCD (6) receives the parallel light that is not blocked by the side of the conical workpiece and records the data.

2. A method for measuring the side profile of a conical workpiece, characterized in that: Scanning measurement using the conical workpiece side profile measuring device as claimed in claim 1 comprises the following steps: Step 1, energizing the cylindrical light source (1) to emit cylindrical waves through photoelectric conversion; Step 2: The cylindrical wave is converted into a plane wave by the collimating lens (2), and is reflected to the digital micromirror device (4) by the reflecting mirror (3); Step 3, giving the micromirror element array of the digital micromirror device (4) an initial flip state, wherein there is a horizontal reflective slit in an on state; Step 4: at the next moment, the reflection slit is translated stepwise, and the translation amount is a unit row of the micromirror element array of the digital micromirror device (4); the area array CCD (6) receives parallel light that is not blocked by the side of the conical workpiece (5), and records two point data of the side profile of the conical workpiece (5) at the current time sequence n and Step 5: After collecting two sets of point data on both sides in sequence, the two sets of data are respectively fitted with a least square method to complete the side profile measurement of the conical workpiece (5). The linear equations are: The number of measurement points obtained in each group is N, and the coefficients of the linear equation are calculated as follows:

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