TWI451064B - Laser displacement measuring device and method combined with image measuring instrument - Google Patents

Description

Laser displacement measuring device and method combined with image measuring instrument

The invention relates to a laser displacement measuring device and method, in particular to a laser displacement measuring device and method combined with an image measuring instrument.

The current technology is changing with each passing day, and the specifications of the products are highly demanded. In recent years, the manufacturers have been working hard to improve the precision measurement capability, and the means of precision and detection technology have been improved.

The measurement of geometrical dimensions is an important means of quality control and quality. The traditional measurement of displacement and surface topography is mostly contact probe detection, which has the following disadvantages:

(1) The workpiece to be measured will be deformed during contact, especially a soft or vulnerable surface;

(2) The probe is prone to wear;

(3) There is a contact filtering effect.

The traditional image measuring instrument is mainly used for plane measurement, and can only detect the two-dimensional (2D) shape of an object, and cannot measure the height and depth of the object.

As shown in FIG. 1 , the conventional triangulation measurement is such that the laser light 11 emitted from the laser module 10 is projected on the object to be tested 2 to display a light spot A, and then scattered to form an energy distribution light cone, which is imaged by the lens 12 . On the photodetector 13. The photodetector 13 can be a position detecting element (PSD), a CMOS photodetector, or a charge coupled sensor (CCD). It can be seen from the geometrical optics that if the object 2 is moved by a distance Δd, the corresponding spot on the photodetector 13 is also displaced by a distance x, for example, the object 2 is moved upward by a distance Δd, and the spot position is The spot A moves to the spot B, and the position of the corresponding spot moves from the spot A' to the spot B' position, and there is a specific relationship between the spot moving distance x and the moving distance Δd of the object to be tested 2, which is also the basic of the triangular measurement. principle. The triangulation measurement can be classified into a scattering type and a reflection type in principle. Triangulation can be roughly classified into direct and oblique types on the detection architecture.

As shown in FIG. 1 , the direct-radiation measurement system is configured such that the laser light 11 emitted from the laser module 10 is projected on the object to be tested 2 to display a light spot A and projected on the object to be tested 2 to move upward. a position of Δd is displayed, a spot B is projected, and a position of the object to be tested 2 is moved downward by a distance Δd to display a spot C, which is projected with the laser beam 11 emitted by the laser module 10 The axes coincide and the corresponding spot A', spot B' and spot C' are respectively produced on the photodetector 13, which is also the most common architecture. The light spot A, the light spot B, and the light spot C of this structure are the same measurement positions on the object 2 to be tested.

As shown in FIG. 2, the oblique triangular measurement architecture is such that the laser light 11 emitted from the laser module 10 is projected onto the object to be tested at the same tilt angle to display a spot A and is projected on the object to be tested 2 Moving to a position above the distance Δd to display a light spot B, projecting a position of the object 2 to be moved downward by a distance Δd to display a light spot C, and respectively generating a corresponding spot A on the photodetector 13 , spot B' and spot C'. The light spot A, the light spot B, and the light spot C of this structure are different positions on the object 2 to be tested, respectively. When the object 2 is moved by a distance Δd, the position of the spot projected on the object to be tested 2 changes with the lateral displacement between the original measurement position, thus causing a measurement error.

Taiwan Patent No. I279522 discloses a displacement measuring method and a displacement sensor. No. I292814 discloses a displacement meter and a displacement measuring method, and No. I278598 discloses a three-dimensional shape measuring device. The above patents disclose measurement techniques using laser light and position detecting elements (PSD), respectively, but do not disclose related techniques for measuring with a combined image measuring instrument.

The present invention has been proposed in order to further improve a triangular measuring device and method which are known to utilize laser light and photodetectors.

The main object of the present invention is to provide a laser displacement measuring device and method combining the image measuring instrument to improve the precision measuring capability of the laser displacement measuring device.

Another object of the present invention is to provide a laser displacement measuring device and method combined with an image measuring instrument, which combines a triangulation method with an image measuring instrument to measure the height, depth and surface shape of the object to be tested. appearance.

For other purposes and functions of the present invention, please refer to the drawings and the embodiments, which are described in detail below.

The invention adopts the concept development system of non-contact measurement, combines the triangulation method with the image measuring instrument, and can measure the height, depth and surface topography of the object to be tested. However, the two systems collide on the optical path. To solve this problem, the present invention changes the laser light to oblique incidence to make the optical path staggered, but the position of the measurement point may change in consideration of the displacement, so the image measuring instrument is used. Monitor the position of the observation point and feedback the angle of incidence to control the oblique direction to ensure that the observation point on the object to be tested is the same point as the measurement point.

As shown in FIG. 3, the laser displacement measuring device 1 of the present invention combined with an image measuring instrument comprises a laser module 10, a lens 12, a photodetector 13, a mirror 14, an image measuring instrument 15 and an information processing unit. 16 components. The information processing unit 16 electrically connects the photodetector 13 and the image measuring instrument 15. The photodetector 13 of the present invention may be a position detecting element (PSD), a CMOS photodetector or a charge coupled sensor (CCD); the mirror 14 may be combined with a power unit 141, and the power unit 141 drives the mirror 14 to change the mirror surface. The power unit 141 can be a motor, a microelectromechanical component, a device that rotates the mirror, or a general scanning mirror device; the information processing unit 16 can be an electronic circuit, a microprocessor, or a computer.

As shown in FIGS. 4 and 5, the position detecting element (PSD) 30 has a structure in which a bottom layer 31 is an N layer, an intermediate layer 32 is a high-resistance substrate I layer, and an uppermost layer 33 is a P layer; A, B It is the two terminal electrodes above the P layer. The surface of the position detecting element 30 is irradiated with a light beam to generate an electron and a hole pair; if the I layer is irradiated with laser light to generate photogenerated carriers, the number of electrons and holes reaching the electrode joint (current magnitude) and The incident position of the light spot is inversely proportional to the distance to the electrode, so that the current value can correspond to the position of the incident light spot. The spot irradiation position is Q, and the electrodes on the P layer are denoted by A, B, and the electrodes of the N layer are C.

FIG. 5 is an equivalent circuit model of FIG. 4, and the distance from the midpoint of the electrode A to the electrode B to the Q point is X. The distance from electrode A to electrode B is L, the current is I _a and I _{b respectively} , the resistance between the two ends is R _S , ρ is the resistivity, and A is the cross-sectional area of the semiconductor, which can be expressed as follows:

Where K is a proportional constant.

It can be seen from the above equation that X is only related to (I _b -I _a )/(I _b +I _a ) on the right side of the equal sign, regardless of other parameters, this position is the centroid position of the incident light energy. As long as according to the relationship X, the signal processing circuit can appropriately measure the centroid position of the spot.

As shown in FIGS. 3 and 6, the present invention adopts an oblique triangular measurement architecture, but utilizes a rotatable mirror 14 and an image measuring instrument 15 to overcome the position of the light spot projected on the object 2 to be tested. The movement of the object 2 changes, thereby causing a problem of measurement error.

The laser light 11 emitted from the laser module 10 of the present invention is reflected by the mirror 14 and projected at a measuring position of the object 2 at an oblique angle to display a spot A, and is imaged by the lens 12 to the photodetector 13. A corresponding spot A' is generated on the photodetector 13, and the image measuring instrument 15 picks up the image of the spot A on the object 2 to be tested.

If the angle of the projection of the laser light 11 is constant, when the object 2 is moved upward or downward by a distance Δd, the image measuring instrument 15 will ingest, as shown in FIG. 2, the laser light 11 is projected on the object 2 to be tested. When the image of the light spot B or the light spot C is displayed by measuring the position, instead of the image of the laser light 11 being projected at the correct measurement position, the information processing unit 16 is used to read and process the image information output by the image measuring instrument 15 , confirming whether the centroid position of the spot on the object 2 is the correct measurement position, and then outputting the control signal to the scanning mirror device via the analog-digital conversion unit 17, as shown in FIG. 6, controlling the rotatable type in the scanning mirror device The mirror 14 rotates its mirror angle so that the laser light 11 is respectively projected to the correct measurement position, that is, the position of the light spot B or the light spot C as shown in FIG. 3, and then the photodetector 13 is measured, and A corresponding spot B' or spot C' is generated on the photodetector 13; the analog digital conversion unit 17 transmits the signal output from the photodetector 13 to the information processing unit 16 for processing; the information processing unit 16 can be based on the spot B' or the spot. Information on the location of C' is calculated 2 was moving distance, thereby measuring the amount of analyte can height, depth and morphology of 3D 2. The PSD signal can also be used to monitor the power of the source and provide a basis for further signal processing and improved accuracy.

The image measuring instrument 15 detects whether the position of the light spot falling on the object to be tested 2 is correct, and then controls the mirror angle of the mirror 14 to adjust the position of the light spot projected by the laser light 11 on the object to be tested 2, and locks Perform the measurement after the correct position. The present invention obtains a correspondence table between the test data and the standard deviation of the displacement (Δd) and (I _b -I _a )/(I _b +I _a ) as shown in FIG. 7 through a plurality of tests, and as shown in FIG. Corresponding diagram of displacement (Δd) and (I _b -I _a )/(I _b +I _a ); wherein Figure 7 is the average of 50 data grabs per point for sampling rate 1K (takeout frequency 100K Hz); In Fig. 8, the horizontal axis is the displacement distance (mm), and the vertical axis is to normalize the output signals at both ends of the PSD, and the straight line is the curve fitting result. From the above test data, it is shown that the information processed displacement (Δd) is linearly proportional to (I _b -I _a )/(I _b +I _a ), so that the present invention can be proved by the signal outputted by the photodetector 13 The feasibility of measuring the moving distance of the object 2.

As shown in FIG. 9, the laser displacement measuring method of the present invention combined with the image measuring instrument comprises the following steps:

(1) causing the laser light emitted from the laser module to be reflected by the rotatable mirror, projecting on the object to be tested at an oblique angle to display a spot on the object to be tested, and imaging the photodetector via the lens;

(2) causing the image measuring instrument to take the image information of the light spot on the object to be tested, and causing the information processing unit to read and process the image information;

(3) The information processing unit confirms whether the spot projected on the object to be tested is at the correct measurement position, if not in the correct measurement position, the process proceeds to step (4), and if it is at the correct measurement position, the process proceeds to the step ( 5);

(4) rotating the rotatable mirror to change the reflection angle of the mirror surface, so that the laser light is projected onto the object to be tested at another oblique angle, changing the position of the light spot, and then proceeding to step (3);

(5) causing the information processing unit to read and process the measurement signal output by the photodetector to obtain the value of the measurement position.

After moving the object to be tested, the mirror can be rotated all the time, and the image measuring instrument always outputs the captured image information, and the photodetector always outputs the measuring signal; the information processing unit processes the image information to confirm the projection to the object to be tested. The light spot is that the information processing unit reads and processes the measurement signal output by the photodetector at the correct measurement position to obtain the value of the measurement position.

The laser displacement measuring method combined with the image measuring instrument of the present invention includes the technical content of the laser displacement measuring device described above in connection with the image measuring instrument of the present invention, and will not be described again.

The invention uses an image measuring instrument to observe the position of the light spot falling on the object to be tested, and then calculates whether the centroid position of the light spot on the object to be tested is the correct measuring position by the software or the firmware, and then controls The mirror angle of the mirror adjusts the position of the light spot, locks it at the correct position, and then measures it. The analog digital conversion unit sends the signal of the output of the position detecting component to the information processing unit for signal processing to measure the object. Height and depth and 3D topography. The invention can improve the precision measuring capability of the laser displacement measuring device.

The above descriptions are only examples of the use of the technical content of the present invention, and any modifications and variations made by those skilled in the art using the present invention are within the scope of the patent claimed.

1. . . Laser displacement measuring device combined with image measuring instrument

10. . . Laser module

11. . . laser

12. . . lens

13. . . Photodetector

14. . . Reflector

141. . . Power unit

15. . . Image measuring instrument

16. . . Information processing unit

17. . . Analog digital conversion unit

2. . . Analyte

30. . . Position detecting element

31. . . Bottom layer

32. . . middle layer

33. . . Peak

(1), (2), (3), (4), (5) are the step numbers in the flowchart of the present invention, respectively.

Figure 1 is a schematic diagram of the architecture of a direct triangular measurement.

Figure 2 is a schematic diagram of the architecture of the oblique triangular measurement.

FIG. 3 is a schematic diagram of a laser displacement measuring device combined with an image measuring instrument according to the present invention.

4 is a schematic cross-sectional view of a position detecting element.

Fig. 5 is a schematic diagram of a corresponding circuit model corresponding to a position detecting element.

FIG. 6 is a schematic diagram showing the working procedure of the laser displacement measuring device combined with the image measuring instrument of the present invention.

Figure 7 is a correspondence table between test data and standard deviation of displacement (Δd) and (I _b -I _a )/(I _b +I _a ) of the present invention.

Figure 8 is a corresponding diagram of the displacement (Δd) and (I _b -I _a )/(I _b +I _a ) of the present invention.

FIG. 9 is a flow chart of a method for measuring laser displacement in combination with an image measuring instrument according to the present invention.

(1), (2), (3), (4), (5) are the step numbers in the flowchart of the present invention, respectively.

Claims (15)

A laser displacement measuring device combined with an image measuring instrument, comprising: a laser module; a mirror; a lens; a photodetector; an image measuring instrument; an information processing unit, electrically connecting the light detecting And the image measuring instrument; wherein the laser module emits a laser beam and projects the object to be tested through the mirror, displays a light spot on the object to be tested, and images the light through the lens. The image measuring instrument is configured to capture image information of the light spot; the information processing unit is configured to read and process the image information, and then confirm whether the light spot is in the correct measurement position; if the light spot is not in the correct position Measuring position, changing the angle of the mirror surface of the mirror, causing the laser light to be projected to the correct measurement position, and then causing the information processing unit to read and process the measurement signal output by the photo detector to obtain the The value of the measurement position. The laser displacement measuring device combined with the image measuring instrument according to claim 1, wherein the mirror is combined with a power unit for driving the mirror to change the angle of the mirror. The laser displacement measuring device according to the second aspect of the invention, wherein the power unit is one of a motor, a microelectromechanical element or a device for rotating a mirror surface. The laser displacement measuring device combined with the image measuring instrument according to claim 2, wherein the power unit is a scanning mirror device. The laser displacement measuring device according to the fourth aspect of the invention, wherein the information processing unit is electrically connected to an analog-to-digital conversion unit; the analog digital conversion unit electrically connects the photodetector, The measurement signal outputted by the photodetector is transmitted to the information processing unit; the analog digital conversion unit electrically connects the scanning mirror device, and transmits a control signal for controlling the mirror rotation angle of the mirror to the scanning mirror device . The laser displacement measuring device combined with the image measuring instrument according to any one of claims 1 to 5, wherein the photodetector is a position detecting element, a CMOS photodetector or a charge coupled sensor One of the laser light is projected onto the object to be tested at an oblique angle. The laser displacement measuring device combined with the image measuring instrument according to claim 6, wherein the information processing unit is one of a microprocessor, an electronic circuit or a computer. A laser displacement measuring method combined with an image measuring instrument comprises the following steps: (1) causing a laser beam emitted from a laser module to be reflected by a mirror, and projecting on a test object to display on the object to be tested a light spot and imaged by a lens to a photodetector; (2) causing an image measuring instrument to take image information of the light spot on the object to be tested, and causing an information processing unit to read and process the image (3) The information processing unit confirms whether the spot projected on the object to be tested is at the correct measurement position, and if not in the correct measurement position, proceeds to step (4), if at the correct measurement position Going to step (5); (4) changing the angle of the mirror surface of the mirror, causing the laser light to be projected onto the object to be tested at another angle, changing the position of the light spot, and then proceeding to step (3); (5) The information processing unit reads and processes the measurement signal output by the photodetector to obtain the value of the measurement position. The laser displacement measuring method of the combined image measuring instrument according to claim 8, wherein the laser light of the step (1) is projected onto the object to be tested at an oblique angle. The laser displacement measuring method of the combined image measuring instrument according to claim 9, wherein the mirror is combined with a power unit for driving the mirror to change the angle of the mirror. The laser displacement measuring method of the combined image measuring instrument according to claim 10, wherein the power unit is one of a motor, a microelectromechanical element or a device for rotating the mirror. The laser displacement measuring method of the combined image measuring instrument according to claim 10, wherein the power unit is a scanning mirror device. The method for measuring a laser displacement of a combined image measuring instrument according to claim 12, wherein the information processing unit is electrically connected to an analog-digital conversion unit; the analog-to-digital conversion unit electrically connects the photodetector, The measurement signal outputted by the photodetector is transmitted to the information processing unit; the analog digital conversion unit electrically connects the scanning mirror device, and transmits a control signal for controlling the mirror rotation angle of the mirror to the scanning mirror device . The laser displacement measuring method of the combined image measuring instrument according to any one of claims 8 to 13, wherein the photodetector is a position detecting element, a CMOS photodetector or a charge coupled sensor. one of them. The laser displacement measuring method of the combined image measuring instrument according to claim 14, wherein the information processing unit is one of a microprocessor, an electronic circuit or a computer.