JPS6360321B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical measuring device, and more particularly to an improvement in an optical measuring device that measures the dimensions of an object to be measured using a parallel scanning light beam.

Conventionally, a rotating scanning light beam (laser beam) is converted into a parallel scanning light beam passing between the collimator lens and a condensing lens by a collimator lens, and an object to be measured is placed between the collimator lens and the condensing lens. There is an optical measuring device that measures the dimensions of an object to be measured based on the length of time of a dark or bright area that occurs when the parallel scanning light beam is interrupted by the object.

For example, as shown in FIGS. 1 and 2, a laser beam 12 is oscillated from a laser tube 10 toward a fixed mirror 14, and the laser beam 12 reflected by the fixed mirror 14 is directed toward a polygonal rotating mirror 16. Therefore, it is converted into a rotating scanning light beam 17, which is passed through a collimator lens 18.
The object to be measured 2 placed between the collimator lens 18 and the condensing lens 22 is converted into a parallel scanning light beam 20 by the parallel scanning light beam 20.
4 is scanned at high speed, and the dimension of the object to be measured 24 in the scanning direction (Y direction) is measured from the length of time of a dark or bright area generated by the object to be measured 24 at that time. That is, the brightness and darkness of the parallel scanning light beam 20 is determined by the light receiving element 2 at the focal point position of the condenser lens 22.
The signal from the light receiving element 26 is input to the preamplifier 28, where it is amplified and then sent to the segment selection circuit 3.
Sent to 0. This segment selection circuit 30 is
A voltage V for opening the gate circuit 32 is generated from the output voltage of the light receiving element 26 and output to the gate circuit 32 only during the time t during which the object to be measured 24 is being scanned. Since the clock pulse CP is inputted to this gate circuit 32 from the clock pulse oscillator 34, the clock pulse P corresponding to the time t corresponding to the scanning direction dimension (for example, outer diameter) of the object to be measured 24 is output from the gate circuit to the counting circuit. 36. The counting circuit 36 counts the clock pulses P and outputs a counting signal to the digital display 38, and the digital display 38 digitally displays the dimension of the object 24 in the scanning direction, that is, the outer diameter. On the other hand, the rotating mirror 16
is generated in synchronization with the clock pulse CP output from the clock pulse oscillator 34 by a synchronous motor 44 which is synchronously driven by the output of a synchronous sine wave oscillator 40 and a power amplifier 42, which generates a sine wave in synchronization with the output of the clock pulse oscillator 34. rotated to maintain measurement accuracy.

Such high-speed scanning laser length measuring machines are becoming widely used because they can measure the length, thickness, etc. of moving objects and high-temperature objects with high precision in a non-contact manner.

However, during the rotation of the rotating mirror 16 in the high-speed scanning laser length measuring machine as described above, as shown in an enlarged view in FIG.
Since the distance of 6A in the scanning direction from the optical axis 18A of the collimator lens 18 changes periodically, there is a problem that the measurement accuracy fluctuates.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical measuring device that minimizes the influence of measurement errors caused by relative displacement of the reflection point of a rotating mirror. .

The present invention provides a parallel scanning light beam generator including a rotating mirror that reflects an incident light beam from a beam generator into a rotating scanning light beam, and a collimator lens that turns the rotating scanning light beam into a parallel scanning light beam; a light receiving element that detects the brightness or darkness of the parallel scanning light beam that has passed through the object to be measured; In an optical measuring device that determines the dimension of the object in the scanning direction by detecting the length of time of a dark or bright area that occurs when a part of the object is blocked, the beam generator directly or indirectly The incident optical axis of the light beam emitted to the rotating mirror and the optical axis of the collimator lens which makes the rotating scanning light beam reflected by the rotating mirror into a parallel scanning light beam are defined as the rotation center axis of the rotating mirror. The effect of the relative displacement of the reflection point by the rotating mirror is calculated by placing the rotation plane orthogonal to the plane of rotation and intersecting it at equal angles from mutually opposite directions. This is made to appear as a variation in the direction perpendicular to , thereby reducing measurement errors.

Further, in the optical measuring device, the incident optical axis and the optical axis of the collimator lens are arranged in the same plane that is orthogonal to the rotation plane and includes the rotation center axis, and the rotation This is designed to further minimize measurement errors due to variations in the reflection point of the mirror.

Embodiments of the present invention will be described below with reference to the drawings. Here, in this embodiment, the same or corresponding parts as those of the conventional optical measuring device shown in FIG. 1 are given the same reference numerals as in FIG. 1, and the explanation thereof will be omitted.

In this embodiment, as shown in FIGS. 4 and 5, in an optical measuring device similar to that shown in FIG. an incident optical axis of the light beam 12 emitted to the rotating mirror 16;
This light beam 12 is reflected by the rotating mirror 16 and the optical axis 1 of the collimator lens 18 converts the rotating scanning light beam 17 into a parallel scanning light beam 20.
8A is the rotation center axis 16B of the rotating mirror 16.
They are arranged so as to intersect at equal angles from opposite directions with respect to the rotation plane 16C, which is orthogonal to the rotation plane 16C.

That is, as shown in FIG. 2, the optical axis of the collimator lens 18 and the optical axis of incidence from the fixed mirror 14, which were conventionally arranged within the rotation plane of the rotation mirror 16, are moved in different directions with respect to the rotation plane 16C. (upper and lower in FIG. 5).

In this embodiment, the fixed mirror 14 for reflecting the laser beam 12 emitted from the laser tube 10 is located below the rotating plane 16C in the figure, and the collimator lens 18 is located below the rotating plane 16C.
They are placed above C. Further, in the same plane that is orthogonal to the rotation plane 16C of the light beam 12 and that includes the rotation center axis 16B, the incident optical axis and the collimator lens 18 are located.
The optical axis of is arranged.

Therefore, in this embodiment, by rotating the hexagonal rotating mirror 16, the reflection point 16 is
A is a fixed mirror 14 and a collimator lens 18
The distance from
Since it mainly appears in the direction perpendicular to the scanning direction of the rotational scanning light beam 17 and the parallel scanning light beam 20 (in the vertical direction in the figure), the measurement-side error is significantly reduced.

That is, in the conventional rotating mirror 16 shown in FIG. 3, the reflection point 16A moves with the rotation of the rotating mirror 16, but the directional components of the movement are (1) the optical axis direction of the collimator lens 18 (left-right direction in FIG. 3), and (2) Scanning direction (vertical direction in Figure 3).

On the other hand, in the case of the embodiments shown in FIGS. 4 and 5,
Similarly, the directional components of the movement of the reflection point 16A due to the rotation of the rotating mirror 16 are (3) the optical axis direction of the collimator lens 18 (horizontal direction in FIG. 5) and (4) the direction perpendicular to the scanning direction of the parallel scanning light beam 20 ( Fig. 5 (vertical direction).

Comparing the two, (1) and (3) have a common error factor. However, when (2) and (4) are compared, (2) causes an error in the scanning direction (that is, a measurement error), whereas (4) does not affect the measured value. Therefore, Figure 4,
In the case of the embodiment shown in FIG. 5, the measurement error is reduced compared to the conventional example shown in FIG.

In the above case, even if the parallel scanning light beam 20 fluctuates in the vertical direction, the measurement object 24 is scanned and measured in a direction perpendicular to this fluctuation, so that the vertical fluctuation does not affect the object 24.

Note that in the above embodiment, the optical axis of incidence of the laser beam 12 on the rotating mirror 16 and the collimator lens 18 are
The optical axis 18A of the collimator lens 18 is arranged in a plane that is perpendicular to the rotation plane 16C and includes the rotation center axis 16B, but the present invention is not limited to this. This also includes cases where the plane containing the optical axis intersects the rotation plane 16C at an angle smaller than 90 degrees (excluding 0 degrees).

Here, if the incident optical axis and the optical axis 18A are arranged in a plane orthogonal to the rotation plane 16C, the influence of intersection due to the relative displacement of the reflection point 16A of the rotation mirror 18 will be greatest in the direction perpendicular to the scanning direction. , the measurement error in this case is the smallest. In other words, the error is minimum when the intersection angle is 90 degrees, and the third
As shown in the figure, the error is maximum when the intersection angle is 0 degrees. Therefore, even if the crossing angle is larger than 0 degrees and smaller than 90 degrees, the measurement error can be reduced compared to the conventional method.

Since the present invention is configured as described above, it has the advantage of being able to significantly reduce the influence of changes in the relative distance of the polygonal rotating mirror to the beam generator and the collimator lens on measurement errors with a simple configuration. It has a good effect.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional optical measuring device, Fig. 2 is a front view of the same, and Fig. 3 is an enlarged view of the relationship between the rotating mirror, its incident optical axis, and the collimator lens in the same optical measuring device. FIG. 4 is a plan view showing an enlarged main part of an embodiment of the optical measuring device according to the present invention, and FIG. 5 is a front view thereof. 10... Laser tube (beam generator), 12...
Laser beam, 16...Rotating mirror, 16B...
Rotation center axis, 16C... Rotating plane, 17... Rotating scanning light beam, 18... Collimator lens, 1
8A...Optical axis, 20...Parallel scanning light beam, 2
4... Object to be measured, 26... Light receiving element.

Claims (1)

[Claims] 1. Parallel scanning light beam generation, including a rotating mirror that reflects an incident light beam from a beam generator into a rotating scanning light beam, and a collimator lens that turns the rotating scanning light beam into a parallel scanning light beam. and a light-receiving element that detects the brightness of the parallel scanning light beam that has passed through the object to be measured, and the object to be measured is placed between the parallel scanning light beam generator and the light-receiving element. In an optical measuring device that determines the dimension of the object in the scanning direction by detecting the length of time of a dark area or a bright area that occurs when a part of the light beam is interrupted, the beam generator directly or The incident optical axis of the light beam that is indirectly emitted to the rotating mirror and the optical axis of the collimator lens that makes the rotating scanning light beam reflected by the rotating mirror into a parallel scanning light beam are connected to the rotating mirror. An optical measuring device characterized in that the optical measuring device is arranged so as to intersect at equal angles from opposite directions with respect to a rotation plane perpendicular to a rotation center axis. 2. The optical system according to claim 1, wherein the incident optical axis and the optical axis of the collimator lens are arranged in the same plane that is orthogonal to the rotation plane and includes the rotation center axis. Optical measuring device.