JPH0247525A - Light beam diameter measuring device - Google Patents

Abstract

PURPOSE:To make it easy to set a light beam in the central part of a visual field by providing two transparent flat plates in an optical path of the light beam to a two-dimensional image pickup element so that the axes of rotation of the plates are specified. CONSTITUTION:The radius of a light beam 10 is magnified by a lens 30 and picked up on a two-dimensional image pickup element 41 of a TV camera 40, a signal from the camera 40 is processed by a beam radius calculating device 42, and the radius of the beam 10 is measured therefrom. On the occasion, two transparent flat plates 20a and 20b are provided rotatably in the course of an optical path of the beam 10, the axes of rotation of the plates are made to intersect the optical axis of the beam 10 perpendicularly, and the axes of the flate plates 20a and 20b are made to intersect each other perpendicularly.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for measuring the diameter of an original beam using a two-dimensional imaging sensor, and in particular to a device for measuring the diameter of an original beam using a two-dimensional imaging sensor, and in particular for measuring the diameter of a laser beam used in an optical recording/reproducing device. This invention relates to a device for measuring the diameter of an original beam that can be measured with good accuracy.

[Conventional technology]

In a light beam diameter measuring device using a solid-state image sensor as a light receiving sensor, the original beam diameter is generally calculated by measuring the light intensity at each pixel. for example,
In Japanese Unexamined Patent Publication No. 59-44628, the position of a pixel having a large output level and 1/e'' of the maximum output level are disclosed.
The light beam diameter is calculated from the position of the pixel having the output level. Also, % opening 60-256
According to Publication No. 019, horizontal, vertical! i [The light intensity distribution in two directions is memorized, and the original beam diameter is calculated from the number of pixels whose light intensity exceeds a certain threshold.

In these publications, the calculation of the optical beam diameter is performed using the pixel as a basic unit, so the accuracy does not increase beyond the size of the pixel, and an error equivalent to the size of the pixel occurs. Therefore, in order to reduce the measurement error, the light beam image projected onto the sensor receiving surface can be enlarged to increase the measured value, and the error corresponding to the pixel can be made relatively small. This can be easily done by using a lens or the like. For this reason, in the case of Japanese Patent Laid-Open No. 59-44628, a lens for enlarging the original beam is provided in front of the image sensor.

[Problem to be solved by the invention]

However, when projecting an enlarged light beam image onto an image sensor, the field of view for capturing the original beam and measuring the diameter becomes narrower. For example, even if the size of the light receiving part of the image sensor is 8.8 x 6.6 m, the original beam is
When magnified twice, the field of view is 0.88 x O,6
It is 6wm and becomes small when harvested.

If the field of view is narrow, the original beam may no longer be projected onto the image sensor due to a shift in the optical axis of the original beam.

This means that the projected original beam image is likely to be chipped. Therefore, it is necessary to capture the light beam in the center of the field of view, but since the field of view is small, it is not easy to make the original beam enter the field of view, and the work efficiency is greatly reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an fC and original beam diameter measuring device that can easily capture the original beam within the field of view even when the field of view becomes narrow due to expansion of the original beam image.

[Means to solve the problem]

The above purpose is to enable two transparent flat plates (both of which are rotatable) whose rotational axes are orthogonal to each other, with the rotational axis perpendicular to the optical axis of the light beam, during the path of the light beam to the two-dimensional image sensor. This is achieved by establishing a

[Effect]

When the transparent flat plate is perpendicular to the light beam original axis, the original beam simply travels straight through the transparent flat plate, but when the transparent flat plate is not perpendicular to the original axis, the original beam travels straight through the transparent flat plate due to the law of refraction. This means that the original beam axis should be parallel to the original beam axis and should be emitted in a state slightly deviated from that direction. The amount of deviation depends on the rotating state of the transparent flat plate, but since the direction of the deviation is constant, the deviation direction is perpendicular to each other for a small amount of t (in both cases, the two transparent flat plates are rotatably provided). In this case, depending on the adjustment of the rotational state of the two transparent flat plates, the original beam can be divided into two
The light must be in good condition to be incident on the original image sensor.

〔Example〕

The present invention will be explained below with reference to FIGS. 1 to 5.

First, to explain the principle of the present invention, as shown in FIG. It is designed to be imaged and detected as an enlarged projected image 11. The video signal from the TV right camera 0 is processed in a predetermined manner by the beam diameter "X/fl device f!t42, so that the beam diameter of the light beam 10 can be measured with good accuracy. However, the position of the original beam enlarged projection image 11 on the two-dimensional image sensor 41 can be changed by the rotating state of the transparent flat plate 20 inserted in the optical path of the secondary beam 10.The transparent flat plate 20 itself It is rotatably supported by a support frame 22 with its rotation axis perpendicular to the original axis of the original beam 10, and its rotation state can be easily changed using a rotation knob 21.

Therefore, if the transparent flat plate 20 is in a state perpendicular to the optical axis of the light beam 10, the light beam enlarged projected image 1
1 is entirely on the two-dimensional image sensor 41, the beam diameter of the light beam 10 is measured in this state.
g 51fflla+). X
If the beam protrudes in the direction (see FIG. 3 [bl]), by appropriately rotating the transparent flat plate 20, the entire original beam enlarged projected image 11 can be positioned on the two-dimensional image pickup device 41. This enables imaging and detection (see FIG. 3, 1cI).

As described above, when the original axis of the original beam 10 is deviated in the X direction, the beam diameter can be measured by appropriately rotating the transparent flat plate 20, but in general, Since the original axis of the original beam 10 may be deviated in the X direction, or in the x and It would be a good idea to set one up. FIG. 1 shows the structure F'N in that case. The transparent flat plates 20a and 20b are provided corresponding to the y direction and the x direction, respectively. Regardless of the direction in which the original axis of the ll'yt beam 10 is deviated, the beam diameter of the original beam 10 can be defined. That is, by simultaneously adjusting the rotational state of either or both of the transparent flat plates 20a and 20b, the entire light beam enlarged projection image 11 can be positioned on the two-dimensional image sensor 41,
In this state, the beam diameter of the light beam 10 is measured.

〔Effect of the invention〕

As explained above, since the optical axis of the original beam can be arbitrarily shifted to another optical axis parallel to this, the entire original beam image can be easily positioned on the two-dimensional imaging device. The beam diameter will be measured in this state.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of an example of the optical beam diameter footing device according to the present invention, Fig. 2, Fig. 3 (α), lbl, lcl.
is a diagram for explaining the principle. 10... Original beam, 11... Original beam enlarged projection image,
20 α child, 20b...transparent flat plate, 4 2...beam diameter calculation device. ...2D image sensor

Claims (1)

[Claims] 1. A light beam diameter measuring device designed to measure the diameter of a light beam by making the light beam incident on a two-dimensional image sensor, which includes: A light beam diameter measuring device characterized by a structure comprising rotatably provided at least two transparent flat plates whose rotational axes are orthogonal to the optical axis of the light beam and whose rotational axes are orthogonal to each other.