JPH0266432A - Optical measuring instrument - Google Patents

Abstract

PURPOSE:To attain the simultaneous measurement of many items of an object by receiving three reflected light beams from the object to be measured, processing the received beams by corresponding processing circuits and outputting a brightness signal, a height signal, an inclined angle signal, and a scatterness signal. CONSTITUTION:Laser beams are projected to both the sides of the object to be measured, beams reflected to both the sides of the projected beams are detected by the 2nd and 3rd optical position detectors 27a, 27b and the reflected light from the object to be measured through a beam splitter is detected by the 1st optical position detector 27c. The outputs of the detectors 27a, 27b are processed by processing circuits 32, 34, a brightness signal Ba, a height signal Ha, a brightness signal Bb, and a height signal Hb are respectively outputted and the output of the detector 27c is processed by a processing circuit 33 to output a brightness signal Bc. The maximum or total of the signals Ba to Bc is selected by a selecting circuit 35, the signals Ba, Bb, Ha, Hb are received, the signals Ha, Hb having larger brightness are selected by a selecting signal 36 and the signals Ba to Bc are received by the circuits 37, 38 to obtain an inclined angle signal and a scatterness signal.

Description

[Detailed Description of the Invention] [Summary of the Invention] Regarding an optical measurement device that optically measures multiple items simultaneously on the shape and properties of an object, an object of the present invention is to enable the optical measurement device to measure more items simultaneously. A laser light source, a beam splitter, an optical scanner, a side mirror for the light reflected from the object to be measured on both sides of the projected light, and a first optical position detector that receives the reflected light that returns along the path of the projected light and passes through the beam splitter. , an optical system including second and third optical position detectors that receive the light reflected on both sides; a first processing circuit that receives the output of the tenth optical position detector and outputs a brightness signal; 2. Second and third processing circuits that receive the output of the third optical position detection circuit and output brightness signals and height signals; receive brightness signals from the first to third processing circuits and output the brightness signals; a brightness selection circuit that outputs the brightness signal or the sum of the brightness signals, and a height selection circuit that receives the brightness signal and the height signal from the second and third processing circuits and outputs the height signal of the one with the larger brightness signal. further comprising a tilt angle calculation circuit that receives brightness signals from the first to third processing circuits and outputs tilt angle signals; and/or a tilt angle calculation circuit that receives brightness signals from the first to third processing circuits and outputs scattering degree signals. and a signal processing system including a scattering degree calculation circuit.

[Industrial application field]

TECHNICAL FIELD The present invention relates to an optical measurement device that optically measures multiple items simultaneously on the shape and properties of an object.

Optical measurements are used in many applications.

The most common measurement item is brightness, which is measured by the amount of reflected light. Devices that optically measure the height of objects using trigonometry and the like have also been developed.

[Conventional technology]

A method of optically measuring the three-dimensional shape of an object is used as an effective method for automatically inspecting the mounting state of components mounted on a printed circuit board. An example is shown in FIG.

This is called a light cutting method, in which a sheet of light is projected from directly above the object 10 to be measured, and the object 10 and its stand 10 are
A light cutting line! is formed, and this is imaged from an oblique direction with a TV (television) camera 13 to obtain an image as shown in FIG. Bright line 2 on the stand 11. ．． 24 is the zero line, and the distance from this to the bright lines 1z and lz corresponds to the height of the object 10, so find this (scan in the X direction for each y value, and calculate the above distance from the y value of the bright line. ), camera 13
Object 1 is determined by trigonometry from the position (angle and distance) of
Calculate the height of 0.

FIG. 9 shows an optical system for three-dimensional shape measurement previously proposed by the present inventor. A laser beam from a laser light source 21 is made into parallel light by a collimating lens 22, and the object to be measured 10 is scanned with the parallel light by an optical system consisting of a rotating polygon mirror 23, a parabolic mirror 24, and a mirror 25. The system sends the reflected light to the imaging lens 26 and causes the photodetector 27 to receive the light. The output of the photodetector 27 is processed by a signal processing circuit 28,
A signal S indicating the height of the object to be measured 10 and, if necessary, a signal Sz indicating the brightness are output.

The procedure for measuring the height of an object to be measured will be explained with reference to FIG.
and B-A is the height.

The parallel light L1 from the lens 22 passes through the rotating polygon mirror 2 as shown in the figure.
3. The light enters the object 10 via the parabolic mirror 24 and the mirror 28. The reflected light from the low part A is as shown by a solid line L2, and that from the high part B is shown as a dotted line L3, and the positions where the light is incident on the photodetector 27 are A' and B'.

The incident points A' and B' on the photodetector vary depending on the inclination angle of the mirror 25, etc., but basically they vary depending on the positions of parts A and B, and the distance between A' and B' is the distance between AB (of the object). height). Therefore, if a light spot position detector (PSD), for example, is used as the photodetector 27, a detection output of the incident light points A' and B' and thus the height of the object to be measured can be obtained.

The PSD is based on a PN junction and a resistance layer, and as shown in FIG. 11, when spot light is incident, photocurrents Ia and Ib flow depending on the position of the incident light.

If it is in the center, Ia=Ib, if it is above the drawing, Ia>Ib according to the deviation, and vice versa if it is below. If the height of the object is set so that the reflected light point A' from the low part of the object 10 (the top surface of the table on which the object 10 is placed) A is at the center of the PSD, the height of the object is (I a - I
b) / (1a+Ib). Note that Ia+I
b indicates the incident light to the PSD and therefore the reflected light (brightness) of the object to be measured. Therefore, this optical system can output the height and brightness of the object to be measured.

[Problem to be solved by the invention]

Conventional optical measurement devices measure the height and brightness (reflectance) of an object.
etc., and does not measure many more items at the same time.

However, in recognition (image reading) systems, such as systems that automatically recognize whether parts are mounted on a printed board as normal or abnormal,
In addition to the height and brightness of the object (component), the angle of inclination (such as whether it is installed at an angle) and the degree of light scattering (such as whether the part in question is the intended one) are also important.

Therefore, an object of the present invention is to enable an optical measuring device to measure more items simultaneously.

[Means to solve the problem]

In the present invention, the optical system shown in FIG. 1 is used and the signal processing shown in FIG. 2 is performed to obtain a tilt angle signal and/or a scattering degree signal in addition to a brightness signal and a height signal.

As in all figures, parts that are the same as in other figures are given the same reference numerals.

In FIG. 1, (a) is a top view, Φ) is a front view, and (C) is a side view, all of which are schematic views (explanatory views). 31 is a polarizing beam splitter which directs the laser beam from the laser light source 21 to the rotating polygon mirror 23, and directs the laser beam from the rotating polygon mirror 23 to the lens 26 and, as a result, to the photodetector 27.

24A is an fθ lens, which has the same function as the parabolic mirror 24A. Two mirrors 25 are provided as shown in FIGS. 1A and 1C, and the light projected onto the object to be measured 10 passes through the middle of these mirrors. Reflected light L Za+ at object 10
L zb is reflected by mirrors 25a and 25b, passes through fθ lens 24A1 rotating polygon mirror 23, lenses 26a and 26b, and enters photodetectors 27a and 27b. That is, three lenses 26 and three photodetectors 27 are provided, two on each side of the lens 26 and three photodetectors 27 for reflected light, and one in the center for direct light from the laser light source 21 split by the beam splitter 31.

In FIG. 2, 32 to 34 are processing circuits, and photodetectors 27a to 2
7c. 35 is a brightness selection circuit, which receives brightness signals Ba-Bc from processing circuits 32 to 34;
is input and brightness signal B is output. 36 is a height selection circuit which receives brightness signals Ba and Bb from processing circuits 32 and 34;
and height signals Ha and Hb are input, and a height signal H is output. Further, 37 is a tilt angle calculation circuit, and the processing circuits 32 to 34
It inputs brightness signals Ba-Bc from , and outputs a tilt angle signal A. Furthermore, 38 is a scattering degree calculation circuit, and the processing circuit 3
The brightness signals from 2 to 34 are input, and the scattering degree signal S is output.

Depending on the application, either the tilt angle calculation circuit or the scattering degree calculation circuit may be omitted.

[Effect]

The laser light from the laser light source 21 passes through the beam splitter 31
It is reflected by the rotating polygon mirror 23, and is reflected by the fθ lens 24.
At point A, the beam becomes a spot beam and enters the object to be measured 10 perpendicularly. When the laser light from the laser light source 21 is linearly polarized (semiconductor lasers are normally linearly polarized), it is efficiently reflected by the polarization beam splitter 31. As the polygon mirror 23 rotates, the path of the laser beam moves within the dotted line range, and the object 10
scan. Among the reflected lights, those indicated by Lzi and Lzb enter the photodetectors 27a and 27b through the mirrors 25a and 25b, the fθ lens 24A1 rotating polygon mirror 23, and the lens imaging lenses 26a and 26b.

The reflected light L2□ Lo is symmetrical with respect to the incident light L+,
Detection using this light means that the object is viewed from the left and right sides. Some components are reflected along the same path as the incident light L1, and this component passes through the beam splitter 31 and enters the imaging lens 26c, and further enters the photodetector 27c.

Both f-theta lenses and parabolic mirrors have similar functions (parallel light creation/focusing), but f-theta lenses are better for handling symmetrical rays like reflected light L2a and LH, while parabolic mirrors have similar functions. It is impossible in principle to be symmetrical.

Although not shown, if the height of the light incident point portion of the object to be measured 10 changes, the locus of the reflected light 12mI Lzb changes, and the light incident points on the photodetectors 27a and 27b also change.

The direction of reflected light that follows the same path as the incident light is perpendicular, so it does not change even if the height changes. Therefore, the photodetector
When D is used, the brightness signal from the left and right photodetectors 27a and 27b is as Ta+Ib, and (Ia-1b)
A height signal is obtained as / (Ia+Ib), and a brightness signal is obtained as Ia+Ib from the central photodetector 27c. Processing circuits 32-34 in FIG. 2 perform this processing.

The brightness selection circuit 35 in FIG.
maximum value) and set this as brightness signal B. The sum of the brightness signals Ba-Bc may be calculated and used as the brightness signal, and the point is that this brightness signal is a signal indicating how dimly the object to be measured appears when irradiated with light.

Further, the height selection circuit 36 receives the brightness signals Ba, Bb and the height signals Ha, Hb from the processing circuits 32 and 34, selects the height signal with the larger brightness signal, and selects the height signal to be determined. Output as signal H.

The darker height signal is from the shadow area and may not indicate the true height.

The inclination angle of the object to be measured can be determined as follows. As shown in Fig. 3, if the reflection angles of the reflected lights Ba to Bc (indicated by the same symbols as the brightness) are θa to θC, then the average reflection angle θ is θ= (Baθa+Bbθb+Bcθ
c) / (Ba + Bb + Bc)...
(1). The inclination angle A is half the average reflection angle, that is, the following equation (the inclination angle is half the reflection angle).

A=θ/2 ・・・・・・(
2) Next, the degree of scattering indicates the degree of dispersion of reflected light in each direction, and is related to the material of the object. This is (3)
It is expressed as the average deviation σ of the equation.

Ba+Bb+Bc ・・・・・・(3) In addition to the average deviation, standard deviation and variance may also be used.

〔Example〕

FIG. 4 shows an embodiment of the brightness selection circuit 35.

41.42 is a comparator, and 43.44 is a selector.

The comparator 41 compares the brightness signals Ba and Bb, and selector 4
Let 3 pass the larger one. For example, if Ba>Bb, the comparator 41 produces a positive output, and the selector 43, which is two analog gates, turns on the Ba side and outputs the Ba. The comparator 42 compares the brightness signal Bc with the brightness signal Bc output by the selector 43, and similarly passes the larger one to the selector 44. Maximum value selection is now performed.

Processing may also be performed digitally. That is, the processing circuit 32
.about.34 outputs a brightness signal and a height signal as digital values, the comparator is constituted by a digital comparator, and the selector is loaded with the larger one and sets it as a register.

The tilt angle calculation circuit 37 calculates the above equations (1) and (2), and the scattering degree calculation circuit 38 calculates the above equation (3), but digital processing using a processor is easier and more accurate. .

FIG. 5 shows an embodiment of the height selection circuit 36. Comparator 45
receives the brightness signals Ba and Bb, and for example, if Ba>Bb, it produces a positive output and passes Ha to the selector 46, and if Ba<
If it is Bb, a negative output is generated and the selector 46 passes Hb.

FIG. 6 shows an example of a signal processing circuit for a photodetector (PSD). Since the PSD 27 generates photocurrents 1a and Ib, these are converted into voltages Va and Vb by current-voltage converters 51 and 52,
It is input to a subtracter 53 and an adder 54. The output of the adder 54 becomes the brightness signal Bx, which is sent to the subtracter 5 by the division circuit 55.
3 divided by the output of adder 54 is the height signal H.
Becomes x.

FIG. 7 shows the system configuration of the measuring device of the present invention. 61
1 is the optical system shown in FIG. 1, and 62 is the signal processing circuit shown in FIG. 2, etc. 63 is an image memory, 64 is a movable stage on which the object to be measured IO is placed, and 65 is a processor, which are connected to a system bus 66. In the quality/failure inspection of the component mounting state of a printed board, the printed board is placed on a stage 64 and optically scanned by an optical system 61 to obtain the signals Ba to Bc, Ha, )(b), and the signal processing circuit 62 Signals B, H, A, and S are obtained and these are sequentially stored in the image memory 6.
Store in 3. The above signal group is obtained for the entire surface of the printed board including the movement of the stage, and is stored in the image memo U 63.

In the pass/fail test, the signal group of the printed board in a normally mounted state, which has been stored in advance in the image memory 63, etc., and the signal group stored in the memory are compared by sequential memory reading, View matches/non-matches. If they all match, the mounting status is good. The processor 65 performs the digital signal processing described above, stores the obtained signals in memory, and controls stage movement.

[Effects of the Invention] As explained above, according to the present invention, the height, brightness, inclination angle, and degree of light scattering of an object can be measured simultaneously, which is effective for use in inspecting the state of component mounting on prints, etc. .

[Brief explanation of the drawing]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is a block diagram of the signal processing system of the present invention, Fig. 3 is an explanatory diagram of reflected light, and Fig. 4 is a block diagram showing an embodiment of the brightness selection circuit. Fig. 5 is a block diagram showing an embodiment of the height selection circuit, Fig. 6 is a block diagram of the signal processing circuit of the optical position detector, Fig. 7 is a block diagram showing the configuration of the measurement system, and Fig. 8 9 is an explanatory diagram of the height detection method, FIG. 9 is an explanatory diagram of the already proposed measurement system, FIG. 10 is an explanatory diagram of the height measurement principle, and FIG. 11 is an explanatory diagram of the optical position detector. In Fig. 1, 21 is a laser light source, 31 is a beam splitter,
23 is a rotating polygon mirror, 24A is an fθ lens, 25 is a mirror, 10 is an object to be measured, and 27a to 27C are optical position detectors.

Claims (1)

[Claims] 1. Laser light source (21), beam splitter (31),
Optical scanners (23, 24A), side mirrors (25a, 25b) for the light (L_2_a, L_2_b) reflected from the object to be measured (10) on both sides of the projected light, and the beam splitter (31) that returns along the path of the projected light. a first optical position detector (27c) that receives the reflected light that has passed through the
, 27b), a first processing circuit (33) that receives the output of the first optical position detector (27c) and outputs a brightness signal, and second and third optical position detection circuits. Second and third processing circuits (32, 34) that receive the output and output a brightness signal and a height signal; receive the brightness signals from the first to third processing circuits and calculate the maximum value or the sum of the brightness signals; Brightness selection circuit (3) that outputs the object (B)
5), a height selection circuit (36) receiving the brightness signal and the height signal from the second and third processing circuits and outputting the height signal (H) with the larger brightness signal; A tilt angle calculation circuit (37) receives brightness signals from the first to third processing circuits and outputs a tilt angle signal (A), and/or receives brightness signals from the first to third processing circuits and outputs a scattering degree signal (A). An optical measuring device comprising: a signal processing system including a scattering degree calculation circuit (38) that outputs S).