JPS6095306A - Position measuring device - Google Patents

Abstract

PURPOSE:To obtain a titled device which has a high accuracy and also is inexpensive by providing a focusing controlling circuit for moving a movable lens provided so as to be movable in the optical axis direction between a light source and a focusing lens, in the direction for reducing a spot diameter of a reflected image formed on a photodetecting part. CONSTITUTION:A projecting system 2 converts a light 22 generated from a light source 21 consisting of a semiconductor laser device, to parallel lights by a collimating lens 23, and thereafter, irradiates them to an object to be measured 1 through a movable lens 24 and a focusing lens 26. Also, a photodetecting system 3 is provided at a prescribed angle against the optical axis of the projecting system 2, photodetects a reflected light 31 by a photodetector 33 through an image forming lens 32, and also detects a light quantity distribution of a photodetecting spot. Also, a focusing controlling circuit 4 consists of a spot diameter detecting circuit 41, a CPU42 and a movement controlling circuit 43, and moves the lens 24 in the direction A so that the spot diameter becomes minimum, by driving a moving mechanism 25.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a position measuring device used for measuring the position of a processing surface of a workpiece in a laser processing device, for example. Background and Problems] Conventionally, this type of device uses a converging lens to dim the light generated from a light source and irradiates it onto the object to be measured, and the reflected image is set at an arbitrary angle with respect to the optical axis of the irradiated light. The position of the object to be measured is measured by receiving and detecting light with a light receiving system placed apart from the object. Devices applying the so-called triangulation method are known.

By the way, in this Koshiki device, in order to increase the measurement resolution, it is necessary to make the irradiation spot of the irradiation light as small as possible. However, if this irradiation spot is made smaller, the range in the optical axis direction in which the spot diameter can be kept small becomes narrower, resulting in a problem that the measurable range is limited to a small range. For example, when trying to obtain an irradiation spot of 0.1 mm using a semiconductor laser, the range in which this Q, l mm spot can be maintained is only about ±l Mln. Therefore, in the past, attempts have been made to perform measurements using light with a small divergence angle, such as a He--Ne laser.

In the case of this He-N e laser, the irradiation spots a, s
A measurement range of ±20@feces can be achieved in um. However, even if this He-N'e laser is used, it is naturally impossible to improve the measured treetop resistance beyond the performance of the laser itself and to expand the gl11 constant range.
Using a laser has disadvantages in that the device becomes large and expensive, making it unsuitable for practical use.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a position measuring device that is small, inexpensive, and has extremely high measurement performance, without increasing the size of the device (which can perform highly accurate measurements over a wide range).

[Summary of the invention]

In order to achieve the above object, the present invention disposes a movable lens movable in the optical axis direction between the light source and the focusing lens, and also provides a focusing control circuit, which controls the focusing f1.
One circuit detects the spot diameter of the reflected image formed on the light receiving section.

The oT&II lens is moved in a direction to reduce the spot diameter.

[Embodiments of the invention]

FIG. 1 is a schematic configuration diagram of a position measuring device according to an embodiment of the present invention. This device is designed to fill a fixed phantom object r
It is composed of a projection system 2 that condenses and irradiates light for determining Vcit+j, a light receiving system 3 that receives and detects the reflected light from the above-mentioned VC, and a focusing braking circuit 4. There is.

The light projection system 2 includes a light source 2 consisting of, for example, a semiconductor laser device.
The light 22 generated from the light source 21 is made into parallel light by the collimating lens 23, and then the movable lens 24
and a converging lens 26, respectively, to irradiate a fixed object 6111. Here the above movable one
24c, utJJr's drawing 25 makes it possible to move in the optical axis direction (in the direction of the arrow).

On the other hand, the light receiving system 3 is arranged at a predetermined angle with respect to the optical axis of the light projecting system 2, diagonally above the irradiation spot formation position on the object to be measured l.

Then, the reflected light 31 from the above-mentioned (11 constant object I) is received by a light receiver 33 via an imaging lens 32. This light receiver 33 detects the light intensity distribution of the light receiving spot of the reflected image. For example, industrial television (ITV)
It consists of a line sensor using a camera and a solid-state image sensor.

Now, the focusing control circuit 4 includes a spot diameter detection circuit 41 that detects the diameter of the light receiving spot from the output of the light receiver 33 of the light receiving system 3, a control circuit main body (CPU) 42 having a microprocessor as a central control section, and It is comprised of a movement control circuit 43 that drives the moving mechanism 25 of the movable lens 24 in response to a control signal from the CPU 42, and moves the movable lens 24 in the optical axis direction. Above c P
U 4z generates a control signal for reducing the spot diameter based on the spot diameter information detected by the spot diameter detection circuit 41.

Next, the operation of the device configured as above will be explained.

Assume now that when the position of the movable lens 24 is set to {circle around (2)} with respect to the object to be measured 1' as shown in FIG. 2, the diameter of the irradiation spot becomes the minimum.

In this state, for example, if the position of the object to be measured reaches the position indicated by the two-dot chain line l" in the figure, the irradiation light will be defocused and the diameter of the irradiation spot will increase, and the light receiver 33 will move accordingly.
The diameter of the light-receiving spot formed becomes larger. Then, the increase in the diameter of the light receiving spot is detected by the spot diameter detection circuit 4Z and introduced to the CPU 4z. Here, the diameter of the light-receiving spot is detected as the width of the value e of the light-receiving intensity at two centers in the spot, for example.

Then, a control signal for moving the spot diameter detection value M force
The optical axis position of No. 4 is moved. When this movement is completed, the detected value of the spot diameter detection circuit 41 is introduced again, and this detected value N is compared with the previously detected detected value M.
If M≧N, it is determined that the moving direction of the movable lens 24 is correct, and thereafter the movable lens 24 is moved by a fixed amount in the direction of arrow A' while monitoring the detected value of the spot diameter. On the other hand, if the result of the above comparison is M(N), the movable lens 24 is moved by a certain amount in the direction of arrow A" opposite to the direction of arrow A'. After this movement, the detected value of the spot diameter is When this value becomes less than the initially input value M, the direction of movement of the movable lens 24 is changed to the direction of the arrow A' force, and the movable lens 24 is moved by a fixed amount @h.In this way, the object to be measured i The movement of the optical axis position of the movable lens 24 is controlled so that the diameter of the irradiation spot on // is minimized.

The dotted chain line @ in Figure 2 indicates the movable lens 2 after this movement control.
4, and the two-dot chain lines θ and O indicate the trajectories of the irradiated light and reflected light at that time.

In this way, with the device of this example, even if a laser with a narrow range that can keep the spot diameter small is used,
The diameter of the light-receiving spot is monitored and the movable lens 24 is moved so that this diameter is always the minimum, so no matter where the object to be measured is located, the spot diameter is always the minimum for this object. The irradiation light can be irradiated so that the That is, as a result, the range in which the spot diameter can be kept small can be greatly expanded. Therefore, highly accurate position measurement can be performed over a wide range.

Moreover, since light with a not-so-small divergence angle, such as a semiconductor laser, can be used as the measurement light, He-Ne
Compared to the case where a laser or the like is used, the device can be made smaller and can be provided at a lower cost.

Note that the present invention is not limited to the above embodiments.

For example, in the above embodiment, the diameter of the light receiving spot is detected as a range having an intensity of e relative to the peak value, and the OT dynamic lens is moved in a direction to reduce the diameter. The movement of the movable lens may be controlled so that the peak value is maximized. Also.

In the above embodiment, the movable lens 24 is controlled to be moved by a constant amount, but the amount of movement may be variably set according to the detected value of the spot diameter. In this way, the time 1145 during movement control of the movable lens 24 can be further shortened. Furthermore, the collimator lens and the movable lens may be integrated, and the control signal may be created using a logic circuit or a decoder instead of the CPU0 (ゝO [Effects of the Invention] As described in detail above) According to the present invention, a movable lens movable in the optical axis direction is disposed between the light source and the focusing lens, and a focusing control circuit is also provided, and this circuit controls the reflected image formed on the light receiving section. The spot diameter is detected and the movable lens is moved in a direction to reduce the spot diameter.

Therefore, according to the present invention, it is possible to provide a position measuring device that is small, inexpensive, and has excellent measurement performance, which can perform highly accurate measurements over a wide range without increasing the size of the device. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a position measuring device according to an embodiment of the present invention, Figs. 2 and 3 are for use before the operation of the device, and Fig. 2 shows the focusing control operation. The schematic diagram shown in FIG. 3 is a flowchart showing the control procedure of the CPU. 1.1', l"... Object to be measured, 2... Projection C system, 3... Light receiving system, 4... Focusing control circuit, 21.
... Light source, 24... Wtfj lens, 25... Moving mechanism, 26... Focusing lens, 32... Imaging lens,
33... Light receiver. 41... Spot diameter detection circuit, 42... CPU, 4
3...Movement control circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] Light generated from a light source is focused by a focusing lens and irradiated onto the object to be measured, and the reflected image is received and detected by a light receiving system arranged at an arbitrary angle with respect to the optical axis of the irradiated light. In a position measuring device for measuring the position of an object to be measured, a movable lens is disposed between the light source and the focusing lens so as to be movable in the direction of the optical axis thereof, and a movable lens is disposed between the light source and the focusing lens, and A position measuring device comprising: a focusing control circuit that detects a spot diameter of a formed reflected image and moves the movable lens in a direction to reduce the spot diameter.