JP2002005623A - Method for measuring displacement using laser light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress effects of measurement errors due to speckle pattern. SOLUTION: The method for irradiating an object with a laser light, focusing the image of reflected light on an image sensor and then measuring the displacement of the object, based on the focus position of the image on the image sensor, comprises a first step for moving the region of the object being irradiated with laser light by a micro amount at a time, a second step for focusing the image of reflected light on the image sensor, each time when the irradiating region is moved by the micro amount, a third step for compositing the images focused on the image sensor, and a fourth step for setting the focus position on the image sensor designated by the results of compositing as the focus position of the image of reflected light on the image sensor between micro movements of the irradiating region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring method using a laser beam, and more particularly, to a displacement measuring apparatus using a laser beam to which a triangulation method is applied. The displacement measurement method.

[0002]

2. Description of the Related Art Conventionally, as a device for measuring a moving amount of an object as an object, a size of the object, a shape of the object, etc., for example, a displacement measuring device using laser light to which a triangulation method is applied has been known. Are known.

FIG. 1 is a diagram illustrating a conceptual configuration of a displacement measuring apparatus using laser light to which such a triangulation method is applied.

[0004] The displacement measuring device 10 emits a laser beam of an appropriate wavelength (for example, a wavelength of 655 nm) and condenses the laser beam emitted from the laser diode 12. A lens 14 for irradiating an object 100 having an arbitrary shape as an object, a lens 16 for condensing laser light reflected by the laser diode 12 and reflected by the object 100, and a lens 16. Focused object 100
The CCD 18 as an image sensor that forms an image of the reflected light from the camera, the object 100 is placed, and the driving means such as a motor (not shown) independently drives the x-axis direction, the y-axis direction, and the z-axis direction. And a movable object mounting table 20.

In the above arrangement, for example, the height h (displacement in the z-axis direction) between the part A and the part B of the object 100 placed on the object ) Will be described.

In this case, first, a portion A of the object 100 placed on the object placing table 20 is irradiated with the laser light emitted from the laser diode 12 condensed by the lens 14, and the laser light The reflected light from the surface of the part A of the object 100 due to the irradiation of the
Then, the image of the reflected light is focused on the CCD 18 and the image forming position is specified.

Next, the object mounting table 20 is moved on the xy plane, and emitted from the laser diode 12 focused by the lens 14 to the part B of the object 100 mounted on the object mounting table 20. The reflected laser light is irradiated onto the object 100, and the reflected light from the surface of the part B of the object 100 due to the irradiation of the laser light onto the object 100 is collected by the lens 16, and the image of the collected reflected light is formed on the CCD 18. An image is formed, and the image forming position is specified.

Then, an image formation position on the CCD 18 specified when the laser light is irradiated on the portion A of the object 100 and an image formation position on the CCD 18 specified when the laser light is irradiated on the portion B of the object 100 The height h between the part A and the part B of the object 100 based on the change with the position
(Displacement in the z-axis direction) is obtained by calculation.

As described above, in the displacement measuring apparatus 10 using laser light to which triangulation is applied, the object 1 is irradiated with the laser light.
00 interference pattern (speckle
Pattern) also forms an image on the CCD 18, so that such a speckle pattern affects the specification of the imaging position of the reflected light on the CCD 18 and causes a measurement error. was there.

In the conventional displacement measuring device 10, in order to perform highly accurate measurement, a process of specifying an image forming position on the CCD 18 of the reflected light from the irradiation area of the object irradiated with the laser light is repeatedly performed. The imaging position is finally obtained based on the average value.

However, the speckle pattern is
In order to appear corresponding to the shape of the irradiation area of the object irradiated with the laser light, it is necessary to repeatedly calculate the imaging position while irradiating the same area of the object with the laser light, and just average the result, Although it may be possible to reduce the effect of the noise component contained in the reflected light, there is a problem that the measurement error due to the speckle pattern cannot be reduced in principle.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to reduce the influence of measurement errors due to speckle patterns. It is an object of the present invention to provide a displacement measuring method using a laser beam capable of reducing the displacement.

[0013]

In order to achieve the above object, a displacement measuring method using laser light according to the present invention comprises:
In consideration of the appearance of the speckle pattern corresponding to the three-dimensional shape in the irradiation area irradiated with the laser light, when the irradiation area of the laser light on the object is shifted by a small amount, By synthesizing the reflected light image to be imaged, it is possible to average the speckle pattern itself and obtain a reflected light image with less influence of the speckle pattern on the image sensor. Thus, the effect of the speckle pattern on specifying the image forming position of the reflected light on the image sensor is reduced.

That is, according to the first aspect of the present invention, an object is irradiated with a laser beam to form an image of light reflected from the object on an image sensor, and In the displacement measuring method using a laser beam for measuring the displacement of the object based on the image forming position of the image of the reflected light on the sensor, a first step of moving a laser beam irradiation area on the object by a small amount And a second step of forming an image of the reflected light from the object on the image sensor each time the irradiation area of the laser light on the object moves by a small amount in the first step. A step of combining the images formed on the image sensor in the second step, and a result of the combining in the third step. The image forming position on the image sensor is defined as an image forming position on the image sensor of the image of the reflected light from the object during the movement of the irradiation region of the laser light on the object by a small amount. 4 steps.

According to a second aspect of the present invention, in the first aspect of the present invention, the second step includes the step of irradiating the object with a very small amount of laser light irradiation area. The laser light is turned on and off for a short period of time in synchronization with the movement of the object, and images of the reflected light from the object are formed on the image sensor by multiple exposure.

According to a third aspect of the present invention, in the first aspect of the present invention, the second step includes the step of detecting a minute amount of a laser light irradiation area on the object. By continuously irradiating a laser beam having a weak output during each movement, an image of the reflected light from the object is continuously formed on the image sensor by continuous multiple exposure. It was made.

According to a fourth aspect of the present invention, the object is irradiated with a laser beam to form an image of light reflected from the object on an image sensor, and the image- In the displacement measuring method using a laser beam for measuring the displacement of the object based on the image forming position of the image of the reflected light on the sensor, a first step of moving a laser beam irradiation area on the object by a small amount And flashing the laser light for a small amount of time in synchronization with the movement of the laser light irradiation area on the object by the minute amount in the first step. Forming an image of light reflected from the object on the image sensor in the second step, and forming an image of light reflected from the object on the image sensor in the second step. In each of the third step, the output value of the image sensor is stored in the storage means, and the output value of the image sensor stored in the storage means is sequentially added. The imaging position on the image sensor indicated by the result of the sequential addition of the output values of the image sensor, the reflected light from the object during the movement of the laser light irradiation area on the object by a small amount And a fourth step of setting an image forming position of the image on the image sensor.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a displacement measuring method using laser light according to the present invention will be described in detail with reference to the accompanying drawings.

The displacement measuring method using a laser beam according to the present invention can be carried out for a displacement measuring apparatus 10 having a conventional configuration as shown in FIG.

However, it is assumed that the object mounting table 20 on which the object 100 is mounted is configured to be able to move by a minute distance independently in the x-axis direction, the y-axis direction, and the z-axis direction.

It is assumed that the laser diode 12 can irradiate laser light for a short period of time or stop irradiation of laser light. In other words,
The laser diode 12 repeats emission and extinguishing of the laser light for a very short time, and is capable of blinking the laser light.

Further, it is assumed that the laser diode 12 can continuously irradiate a laser beam having a weak output.

The control of the movement of the object mounting table 20 by a small distance and the control of the laser diode 12 for emitting and turning off the laser beam are performed by the micro-controller.
This is performed by a computer (not shown).

In the above configuration, a first embodiment of the displacement measuring method using laser light according to the present invention will be described with reference to FIG.

In the first embodiment of the displacement measuring method using laser light according to the present invention, the object mounting table 20 on which the object 100 is mounted is set to a small amount in the x-axis direction by 10
The laser light emitted from the laser diode 12 on the object 100 is moved by 10 μm by a small amount.

The object 100 is 10 μm in the x-axis direction.
Each time the laser diode 12 moves, the laser diode 12 is turned on / off (OF) for a very short time in synchronization with this movement.
F) is repeated, and the laser diode 12 repeatedly emits and extinguishes the laser light to blink.

At this time, the laser
Until the irradiation area of the laser beam irradiated from the diode 12 moves from “x = 0” to “x = 70 μm”, C
An image of the reflected light from the object 100 is formed on the CD 18 by multiple exposure, and the charge of each pixel in the CCD 18 at each x coordinate is added.

That is, the irradiation area of the laser beam emitted from the laser diode 12 on the object 100 is represented by “x”.
= 0 ”to“ x = 70 μm ”
When the irradiation area of the laser beam irradiated from the laser diode 12 on the object 100 moves from “x = 0” to “x = 70 μm”, the result of the addition is analog / digital. The digital (A / D) conversion is performed, the result is written into the memory, and the imaging position of the reflected light during the movement of the irradiation area is specified based on the addition result.

Next, a second embodiment of the displacement measuring method using laser light according to the present invention will be described with reference to FIG.

In the first embodiment of the displacement measuring method using laser light according to the present invention, the object mounting table 20 on which the object 100 is mounted is set to a small amount in the x-axis direction by 10
The laser light emitted from the laser diode 12 on the object 100 is moved by 10 μm by a small amount.

The object 100 is 10 μm in the X-axis direction.
During the movement, the laser diode 12 is turned on (ON), and the laser diode 12 continuously emits laser light.

At this time, the laser
Until the irradiation area of the laser beam irradiated from the diode 12 moves from “x = 0” to “x = 70 μm”, C
An image of reflected light from the object 100 is continuously formed on the CD 18 by multiple exposure, and the CCD 1 at each x-coordinate is formed.
8, the charges of the respective pixels are continuously added.

That is, the irradiation area of the laser beam irradiated from the laser diode 12 on the object 100 is “x
= 0 ”to“ x = 70 μm ”
18 are continuously added, and the object 10
The irradiation area of the laser beam irradiated from the laser diode 12 at 0 is from “x = 0” to “x = 70 μm”
To the analog / digital (A
/ D) is converted and written into the memory, and the imaging position of the reflected light during the movement of the irradiation area is specified based on the addition result.

Next, a third embodiment of the displacement measuring method using laser light according to the present invention will be described with reference to FIG.

In the first embodiment of the displacement measuring method using a laser beam according to the present invention, the object mounting table 20 on which the object 100 is mounted is set to a very small amount in the x-axis direction.
The laser light emitted from the laser diode 12 on the object 100 is moved by 10 μm by a small amount.

The object 100 is 10 μm in the x-axis direction.
Each time the laser diode 12 moves, the laser diode 12 is turned on / off (OF) for a very short time in synchronization with this movement.
F) is repeated, and the laser diode 12 repeats the emission and extinguishing of the laser light to blink.

At this time, the irradiation area of the laser beam is set to 10 μm.
Each time it is moved by m, an image of the reflected light from the object 100 is formed on the CCD 18.

Here, every time an image of the reflected light from the object 100 is formed on the CCD 18, a digital value obtained by analog / digital (A / D) conversion of the output value of the CCD 18 is expressed by
The output value of the CCD 18 stored in the memory is sequentially added on the memory.

The image formation position on the CCD 18 indicated by the result of the addition on the memory is changed from “x = 0” to “x = 70” of the laser light irradiation area on the object 100.
It is specified as an image forming position of the image of the reflected light during the movement to “μm”.

Here, FIGS. 5 (a) through 8 (b) show:
With respect to the third embodiment described above, the output waveform of the CCD 18 at each x coordinate of the laser light irradiation region is shown. That is, FIG. 5A shows an output waveform of the CCD 18 when the x coordinate is “x = 0”, and FIG.
FIG. 6A shows the output waveform of the CCD 18 when the x coordinate is “x = 10 μm”, and FIG.
FIG. 6B shows the output waveform of the CCD 18 when the x coordinate is “x = 30 μm”, and FIG. 7A shows the output waveform of the CCD 18 when the X coordinate is “20 μm”. FIG. 7B shows an output waveform of the CCD 18 when the x coordinate is “x = 40 μm”.
μm ”, the output waveform of the CCD 18 is shown.
FIG. 8A shows the CC when the x coordinate is “x = 60 μm”.
The output waveform of D18 is shown. FIG. 8B shows the output waveform of CCD 18 when the x coordinate is “x = 70 μm”.

FIG. 9 shows the state shown in FIGS.
A waveform diagram showing a waveform obtained by synthesizing (averaging) the waveform shown in (b) is shown. The waveform shown in FIG. 9 is very similar to the waveform diagram showing an ideal CCD output waveform without interference shown in FIG. It is an approximation.

That is, according to the first to third embodiments, the influence of the speckle pattern can be reduced.

Then, as shown in FIG. 11, the ideal CCD output waveform without interference shown in FIG. 10 and the waveforms shown in FIGS. 5 (a) through 8 (b) shown in FIG. Since the waveform indicating the difference from the synthesized (averaged) waveform becomes flat, it is hard to appear as a calculation error of the center position of the incident point of the laser beam, and it is possible to perform highly accurate measurement.

The above-described embodiment may be modified as described in the following (1) to (4).

(1) In the above embodiment, the object mounting table 20 on which the object 100 is mounted as a minute amount is moved by 10 μm in the x-axis direction, and the laser irradiated from the laser diode 12 on the object 100 Although the light irradiation area is moved by 10 μm as a minute amount, it is needless to say that the light irradiation area is moved by 10 μm. The minute amount of
It can be any value.

(2) In the above embodiment, the case where the irradiation area of the laser beam irradiated from the laser diode 12 on the object 100 is moved in the x-axis direction has been described, but the present invention is not limited to this. Needless to say, the moving direction of the irradiation area of the laser beam irradiated from the laser diode 12 on the object 100 is an arbitrary three-dimensional direction constituted by the x-axis direction, the y-axis direction, and the z-axis direction. It may be a direction.

(3) In the above embodiment, the object 100 is irradiated with laser light by the laser diode 12, but it is needless to say that the present invention is not limited to this. A device that outputs various laser beams, such as a -Ne laser oscillator, may be used.

(4) The above-described embodiments and the modifications shown in (1) to (3) may be appropriately combined.

[0049]

According to the present invention, there is provided a displacement measuring method using a laser beam, which can reduce the influence of a measurement error due to a speckle pattern because it is configured as described above. It has an excellent effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a conceptual configuration of a displacement measuring device using laser light to which a triangulation method is applied.

FIG. 2 is an explanatory diagram for describing a first embodiment of a displacement measuring method using laser light according to the present invention.

FIG. 3 is an explanatory diagram for explaining a second embodiment of the displacement measuring method using laser light according to the present invention.

FIG. 4 is an explanatory diagram for explaining a third embodiment of the displacement measuring method using laser light according to the present invention.

5A and 5B are waveform diagrams showing an output waveform of a CCD including an interference pattern (speckle pattern). FIG. 5A shows a position of an irradiation area of a laser beam on an object in the x-axis direction represented by “x”.
= 0 ", and (b) shows the case where the position of the irradiation area of the laser beam on the object in the x-axis direction is" x = 10 m ".

FIG. 6 is a waveform diagram showing an output waveform of a CCD including an interference pattern (speckle pattern).
= 20 μm ”, and (b) shows that the position of the irradiation area of the laser beam on the object in the x-axis direction is“ x = 30 μm ”.
m ”.

7A and 7B are waveform diagrams showing output waveforms of a CCD including an interference pattern (speckle pattern), and FIG. 7A is a diagram in which the position of an object irradiated with laser light in the x-axis direction is “x
= 40 μm ”, and (b) shows that the position of the irradiation area of the laser beam on the object in the x-axis direction is“ x = 50 μm ”.
m ”.

FIG. 8 is a waveform diagram showing an output waveform of a CCD including an interference pattern (speckle pattern).
= 60 μm ”, and (b) shows that the position of the irradiation area of the laser beam on the object in the x-axis direction is“ x = 70 μm ”.
m ”.

FIG. 9 is a waveform diagram showing a waveform obtained by synthesizing (averaging) the waveforms shown in FIGS. 5 (a) to 8 (b).

FIG. 10 is a waveform diagram showing an ideal CCD output waveform without interference.

11 shows an ideal CCD output waveform without interference shown in FIG. 10 and FIGS. 5A to 8 shown in FIG. 9;
FIG. 7 is a waveform chart showing a difference from a waveform obtained by synthesizing (averaging) the waveform shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Displacement measuring device 12 Laser diode 14 Lens 16 Lens 18 CCD 20 Object mounting table 100 Object

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Teruhisa Koshiba 1-6-4 Shintoda, Hamamatsu City, Shizuoka Prefecture Roland D. Gee. Co., Ltd. (72) Inventor Tomoko Ishibashi 1-6-4 Shintoda, Hamamatsu-shi, Shizuoka Pref. Gee. Co., Ltd. (72) Inventor Koji Owada 1-6-4 Shintoda, Hamamatsu-shi, Shizuoka Pref. Gee. Incorporated F term (reference) 2F065 AA04 AA53 BB05 BB29 DD03 FF24 FF56 GG06 HH04 JJ02 JJ25 MM14 QQ03 QQ24 QQ28 2F112 AA08 BA06 CA13 DA25 EA03 FA03 FA07 FA21 FA45

Claims (4)

[Claims] An object is irradiated with laser light to form an image of reflected light from the object on an image sensor, and the image is formed based on an image forming position of the image of the reflected light on the image sensor. A displacement measuring method using laser light for measuring the displacement of the object, wherein a first step of moving a laser light irradiation area on the object by a small amount at a time; Each time the laser beam irradiation area moves by a small amount, the image
A second step of forming an image of reflected light from the object on a sensor, and a third step of combining the images formed on the image sensor in the second step, The imaging position on the image sensor indicated by the result of the synthesis in the third step is defined as the position of the image of the reflected light from the object during the movement of the irradiation area of the laser light on the object by a small amount. And a fourth step of setting an image forming position on the image sensor. 2. The displacement measurement method using laser light according to claim 1, wherein the second step is performed for a very short time in synchronization with a very small movement of a laser light irradiation area on the object. A displacement measuring method using a laser beam, which blinks a laser beam and forms an image of the reflected light from the object by multiple exposure on the image sensor. 3. The displacement measurement method using laser light according to claim 1, wherein the second step includes the step of generating a weak output when the irradiation area of the laser light on the object moves by a very small amount. By continuously irradiating laser light, the image
A displacement measuring method using laser light, which continuously forms an image of the reflected light from the object by continuous multiple exposure on a sensor. 4. An object is irradiated with laser light to form an image of reflected light from the object on an image sensor, and the image is formed on the image sensor based on an image forming position of the reflected light image on the image sensor. A displacement measuring method using laser light for measuring the displacement of the object, wherein a first step of moving a laser light irradiation area on the object by a small amount at a time; The laser light is turned on and off for a very short time in synchronization with the movement of the laser light irradiation area by a very small amount, and the image of the reflected light from the object is formed on the image sensor every time the small amount of movement is made. A second step of imaging, and an output value of the image sensor each time an image of reflected light from the object is formed on the image sensor in the second step Is stored in the storage means,
A third step of sequentially adding the output values of the image sensor stored in the storage means; and a step of sequentially adding the output values of the image sensor in the third step, on the image sensor indicated by a result of the addition. A fourth step of setting an image forming position to an image forming position on the image sensor of an image of the reflected light from the object during the movement of the irradiation area of the laser light on the object by a small amount. Displacement measurement method using laser light.