JPH0227607B2 - ICHISOKUTEISOCHI - Google Patents

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 example, in a laser processing apparatus to measure the position of a processing surface of a workpiece.

[Technical background of the invention and its problems]

Conventionally, this type of device condenses light generated from a light source with a condenser lens and irradiates it onto the object to be measured, and the reflected light is placed at an arbitrary angle with respect to the optical axis of the irradiated light. 2. Description of the Related Art There is known an apparatus that uses a so-called triangulation method, which measures the position of the object to be measured by detecting light received by a light receiving system.

By the way, in this type of device, in order to improve the measurement resolution, it is necessary to make the irradiation spot of the irradiation light as small as possible. However, when 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 problems such as the measurable range being 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 0.1 mm spot can be maintained is only about ±1 mm. Therefore, in the past, attempts have been made to perform measurements using light with a small divergence angle, such as a He--Ne laser. For He-Ne laser, the irradiation spot is 0.5mm
A measurement range of ±200mm can be achieved. However, even if this He-Ne laser is used, it is naturally impossible to improve measurement accuracy beyond the performance of the laser itself and expand the measurement range.
When a He-Ne laser is used, 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, allowing highly accurate measurement over a wide range without increasing the size of the device.

[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. The difference between the imaging position of the reflected image formed on the lens and a preset reference position is detected, and the optical axis position of the movable lens is moved in accordance with this difference.

[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 includes a light projection system 2 that focuses and irradiates measurement light onto an object to be measured 1;
It is composed of a light receiving system 3 that receives and detects the light reflected by the object to be measured 1, and a focusing control circuit 4.

The light projecting system 2 has an optical axis 21 made of, for example, a semiconductor laser device, and collimates light 22 generated from this light source 21 with a collimating lens 23, and then collimates the light 22 through a movable lens 24 and a focusing lens 26, respectively. The object to be measured 1 is irradiated with the light. Here, the movable lens 24 is moved by a moving mechanism 25.
It is possible to move in the optical axis direction (arrow A direction).

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 1. Then, reflected light 31 from the object to be measured 1 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, and is, for example, a light spot position detector that outputs the center position of the light receiving spot on the light receiving surface as a coordinate value, or a line sensor using a solid-state image sensor. is used.

The focusing control circuit 4 includes a spot position detection circuit 41 that detects the peak position of the light receiving output signal of the light receiver 33, that is, the center position of the light receiving spot, and a control circuit main body (having a microprocessor as the main control section). CPU) 42 and this CPU4
a movement control circuit 4 that drives the movement mechanism 25 of the movable lens 24 in accordance with the control signal output from the movable lens 24;
It is composed of 3. The CPU 42 calculates the difference between the center position information of the light-receiving spot detected by the spot position detection circuit 41 and the reference position information stored in the internal memory in advance, and based on this difference, the center position information of the light receiving spot detected by the spot position detection circuit 41 is determined. A control signal is generated to minimize the diameter of the irradiation spot, and the movement of the movable lens 24 is thereby controlled.

Next, the operation of the device configured as above will be explained. Now, the movable lens 24 is set at the position shown in FIG. Assume that the image is focused on the position. The spot position information of the light receiver 33 at this time is stored in the internal memory of the CPU 42 as the reference position information BS.

Now, in this state, if the object to be measured 1 moves to the position indicated by the two-dot chain line 1' shown in FIG. The light will be received with a shift. At this time, the amount of deviation C of the reflected light 31' is:
This corresponds to the amount of movement L of the object to be measured 1. When the reflected light 31' is received, the light receiver 33 outputs a light reception signal including the light reception position element, and this signal is guided to the spot position detection circuit 41.
FIG. 3A shows an example of the waveform of this light reception signal. When this light reception signal is introduced, the spot position detection circuit 41 detects the peak of the light reception signal A and uses the peak position as center position information of the light reception spot.
Output to CPU 42 as DS. Then the CPU
42 first inputs the position information DS of the light receiving spot according to the control procedure shown in FIG.
The reference position information BS is read from the internal memory, and then the difference CS between these position information DS and BS is determined. Then, this difference CS is multiplied by a predetermined constant to create a movement control signal, and this movement control signal is given to the movement control circuit 43. Then, the movement control circuit 43
The moving mechanism 25 is driven, and as a result, the movable lens 24 is moved in the optical axis direction by an amount specified by the movement control signal. Therefore, if the constant to be multiplied by the difference CS is appropriately selected, the movable lens 24
moves by an amount corresponding to the amount of movement L between the objects to be measured 1 and 1', and as a result, the diameter of the irradiation spot on the object to be measured 1' becomes minimum.

In this way, according to this embodiment, even if a laser with a narrow range in which the spot diameter can be kept small is used, the optical axis position of the movable lens 24 can be varied in accordance with the difference between the position of the light receiving spot and the reference position. This makes it possible to focus on the object 1 to be measured and minimize the diameter of the irradiation spot, no matter where the object 1 is located. 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 a semiconductor laser can be used,
Compared to the case where a He--Ne laser 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, the collimating lens may be integrated with the movable lens. Further, instead of the CPU of the focusing control circuit, a decoder using a ROM or the like may be provided to read movement control information corresponding to the difference CS and supply it to the movement control circuit 43.
In addition, the configurations of the light receiver, the light source, the focusing control circuit, etc. can be modified in various ways without departing from the gist of the present invention.

〔Effect of the invention〕

As described in detail above, the present invention provides a movable lens movable in the direction of the optical axis between the light source and the focusing lens, and also a focusing control circuit. The difference between the image formation position of the formed reflected image and a preset reference position is detected, and the optical axis position of the movable lens is varied according to this difference.

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

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a position measuring device according to an embodiment of the present invention, Figs. 2 to 4 are used to explain the operation of the device, and Fig. 2 is a trajectory of illumination light and reflected light. FIG. 3 is a diagram showing the received light output waveform, and FIG. 4 is a flowchart showing the control procedure. 1, 1'...Object to be measured, 2...Light projection system, 3
... Light receiving system, 4 ... Focusing control circuit, 21 ... Light source, 24 ... Movable lens, 25 ... Movement mechanism, 3
3... Light receiver, 41... Spot position detection circuit,
42...CPU, 43...Movement control circuit.

Claims (1)

[Claims] 1. 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. A position measuring device for measuring the position of an object to be measured by means of a movable lens disposed between the light source and the focusing lens so as to be movable in the direction of the optical axis thereof, and an image forming part on the light receiving section of the light receiving system. The image forming position of the reflected image when the spot diameter of the reflected image is the minimum is used as a reference, and the image forming position of the reflected image in the light receiving section is detected, and the difference between this detected position and the above reference position is determined. a focusing control circuit that moves the optical axis position of the movable lens by an amount corresponding to .