JPH025241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for forming a plurality of parallel scanning beams from a beam emitted from a single light source.

As a method of measuring the external dimensions of an object to be measured,
There is a method of scanning an object to be measured with a parallel light beam, detecting shadow parts, and measuring external dimensions without contact.

Figure 1 shows an overview of such a measurement method.
A light beam emitted from a light source 1 that generates a highly focused laser beam, etc. is reflected at a reflection angle between θ ₁ and _{θ 2} at a movable reflecting mirror 2a of a U-shaped tuning fork 2, and then collimated by a collimator lens 3. It is converted into a luminous flux. Then, this parallel light flux is the object to be measured S
The light is irradiated with light, is focused again by the focusing lens 4, and is incident on the light receiving element 5.

When the light received by the light receiving element 5 is converted into an electrical signal, a pulse waveform corresponding to the external dimension R of the object to be measured S can be obtained from the signal output from the light receiving element 5 in one scan. Although not shown, since the movement of the scanning light beam is sinusoidal when the deflector is a tuning fork 2, a part of the scanning light beam is taken out by a half mirror to create a sine wave that simulates the movement of the scanning light beam. If we read out the voltage of the sine wave at the falling and rising edges of the pulse waveform corresponding to the external dimension R of the measuring object S and extract the difference between the voltages, we will find that the voltage of the sine wave and the position of the scanning light beam have the same relationship. , the external dimension R of the object to be measured S can be measured in a non-contact manner.

Although the measurement method described above has already been put into practical use, as the external dimension R of the object to be measured S increases, it becomes difficult to increase the scanning width L of the parallel light beam by deflection due to the vibration of the U-shaped tuning fork 2. However, there is a problem that it becomes impossible to measure.

Therefore, as shown in FIG. 2, the collimated light beam made into a parallel light beam by the collimator lens 3 is separated into two light beams L ₁ and L ₂ by the half mirror 6, and the separated light beams L ₁ and L ₂ are reflected, respectively. The direction is changed by the mirrors 7, 8, and 9, and the external edge of the object to be measured S having large dimensions is irradiated, and the light beams (parallel light beams) L ₁ and L ₂ are sent to the light receiving element as in the case of Fig. 1. It is considered that the external dimension R is measured by detecting the outer edge of the object S to be measured by detecting the outer edge of the object S.

However, such an optical device has the drawback that the optical system becomes complicated due to the installation and adjustment of the reflecting mirrors 7, 8, 9 and the half mirror 6, and it is difficult to miniaturize the optical system.

Therefore, instead of the U-shaped tuning fork 2 as a deflector, a rotating polygon mirror may be placed at the position of the movable reflecting mirror 2a in FIG. 1 described above to widen the scanning width L of the parallel light beam.

However, in this case, the number of scans per unit time is limited by the number of divisions and rotation speed of the rotating polygon mirror, so the fewer the number of reflective surfaces of the polygon mirror and the larger the scanning width L, the more the number of scans. The disadvantage is that the measurement time is increased because the measured values are usually averaged over several scans. Therefore, as shown in FIG. 3, a half mirror 10 and a reflector 11 are provided for the light source P, and the luminous flux from the light source P is first made incident on the first reflector 12a attached to the U-shaped tuning fork 12. half mirror 10
It is formed by a first light flux A partially reflected by the mirror 10 and a second light flux B transmitted through the half mirror 10. In the first reflecting mirror 12a, the first and second light fluxes A and B The two beams are deflected by the vibrations of the two beams, and are incident on the collimator lens 13 as two beams of light. Then, by this collimator lens 13, the first parallel light beam _L1 and the second parallel light beam L1 are
It is conceivable to widen the scanning width by forming a parallel light beam L ₂ of .

However, in the case of such a scanning device, a collimator lens 13 is required to obtain a parallel light beam, and the aberration of the collimator lens 13 makes it difficult to obtain a highly accurate parallel light beam. Another problem is that a large aperture lens with no aberrations is expensive, leading to an increase in the cost of the optical device.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical device that can generate a parallel light beam that can measure the external dimensions of a relatively large object to be measured without using a collimator lens. This was done for the purpose of

FIG. 4 shows a first embodiment of the present invention, in which the collimator lens 13 in FIG. 3 is omitted to obtain a parallel light beam.

In the case of this embodiment, it is common that the light beam deflected by the U-shaped tuning fork 12 is formed by the first and second light beams A and B, but the vibration end of the U-shaped tuning fork 12 has a second First and second movable reflecting mirrors 12a and 12b are provided, and a fixed reflecting mirror 14 is placed in a position facing them.

Therefore, to explain the first luminous flux A, first, the light reflected by the first movable reflecting mirror 12a passes through the fixed reflecting mirror 14 and returns to the second movable reflecting mirror 12.
When the beam is incident on point b, it is deflected again.

By the way, when the tuning fork 12 is vibrating, the deflection angles of the first and second movable reflecting mirrors 12a and 12b are the same and have opposite phases, so that one
When the reflecting surface changes by +Δθ, the other 12b
The reflective surface changes by -Δθ.

Therefore, the first movable reflecting mirror 12 is adjusted so that the first luminous flux A becomes a luminous flux A' as shown by the dotted line.
When reflected by a, the light beam A' reflected by the fixed reflecting mirror 14 and incident on the second movable reflecting mirror 12b is incident on a different position from the first light beam A. However, as mentioned above, the first and second movable reflecting mirrors 12
Since a and 12b form reflective surfaces at the same angle and in opposite directions, the light flux A' emitted from the second movable reflecting mirror 12b ends up in the same direction as the first light flux A, and The luminous flux A and the luminous flux when deflected
A′ will form the first parallel light beam L ₁ .

Similarly, regarding the second light beam B, the light beam deflected by the vibration of the tuning fork 12 becomes B', and the reflection path is different, but when it is reflected by the second movable reflecting mirror 12b, the direction is the second light beam B. The light beams B and B' form a second parallel light beam _L2 .

In the case of this embodiment, the collimator lens 13 is not required, so the influence of lens aberration is eliminated.
The optical device also has the advantage of being cheaper.

FIG. 5 shows a second embodiment of the present invention in which rotating polygon mirrors are used as the first and second movable reflecting mirrors in place of the U-shaped tuning fork in the embodiment of FIG.

In this figure, 18 is a first rotating polygon mirror, 19 is a second rotating polygon mirror rotating in the opposite direction in synchronization with the first rotating polygon mirror 18, and 20 is a fixed reflecting mirror.

In this embodiment, the first and second movable reflecting mirrors 12 to which the U-shaped tuning fork 12 shown in FIG.
First and second rotating polygon mirrors 1 in place of a and 12b
This corresponds to the case where 8 and 19 are provided, and the parallel light flux L _A ,
The method for obtaining L _B is also the same. However, mask 1
Parallel light beams L _A and L _B due to the first and second light beams A and B that have passed through 6 are generated in the same space in a time-division manner.

As explained above, in the parallel beam scanning device of the present invention, the light beam incident on the movable reflector is separated into a plurality of light beams, and the light beam is incident on the first movable reflector that deflects the light beam, and the light beam is incident on the first movable reflector. The light beam reflected from the mirror is further incident on a fixed reflecting mirror, and the light beam reflected from the fixed reflecting mirror is incident on a second movable reflecting mirror, and the first and second movable reflecting mirrors The deflection angles of the two are driven in opposite directions to obtain multiple parallel beams, and the interval between the resulting parallel beams can be set arbitrarily, making it possible to scan a substantially wide range. It has the advantage that parallel light beams can be obtained very easily.

Furthermore, since an expensive collimator lens with a small aberration and a large diameter is not used, the effect of lens aberration is eliminated, and a parallel light beam with good parallelism can be obtained at low cost and with high precision.

[Brief explanation of drawings]

Figures 1, 2, and 3 are schematic diagrams of a conventional method for measuring the external shape of an object to be measured.
The figure is a schematic diagram of an apparatus showing one embodiment of the invention, and FIG. 5 is a schematic diagram of an apparatus showing another embodiment of the invention. In the figure, 10 is a half mirror, 11 is a reflective mirror, 12
is a U-shaped tuning fork, 12a is a movable reflector, 13,1
7 is a collimator lens, 14 and 20 are fixed reflecting mirrors, and 15, 18, and 19 are rotating polygon mirrors.

Claims (1)

[Scope of Claims] 1. A first movable reflecting mirror disposed at a position to receive two or more incident light beams having different incident angles and arranged so as to change the reflection angle of the incident light beams;
a fixed reflector that reflects two or more light beams reflected by the movable reflector at different angles in proportion to the incident angle of the incident light beam; and a fixed reflector that receives the two or more reflected light beams reflected by the fixed reflector; A second movable reflector arranged to change the reflection angle of the approximately reflected light beam is provided, and the deflection angle of the first movable reflector and the deflection angle of the second movable reflector are in opposite directions. 1. A parallel beam scanning device comprising a driving means for driving the parallel beam scanning device. 2. Claim 1, wherein the driving means is a U-shaped tuning fork, and the first and second movable reflecting mirrors are fixed to respective free ends of the U-shaped tuning fork. parallel beam scanning device. 3. The parallel light beam scanning device according to claim 1, wherein the first and second movable reflecting mirrors are composed of rotating polygon mirrors rotating in opposite directions.