JPH0424522A - Method for measuring intensity distribution of light beam - Google Patents

Abstract

PURPOSE:To make it possible to detect intensity distribution based on the positions of slits and the change in amount of received light by providing two kinds of the slits which form an angle of 45 deg. with respect to a perpendicular line regarding the moving direction and have the different slant directions, and making the slits cross a light beam at a right angle. CONSTITUTION:Two kinds of slits S1 and S2 which form 45 deg. with respect to a perpendicular line L regarding the moving direction and have the different slant directions are provided in a scanning plate 5. A micrometer 4 is operated, and the scanning plate 5 is moved in the direction of an arrow. Two axes X and Y are measured at the same time. Namely, when the slit S1 is moved from (a) to (b), (c), (d) and (e), the slit S1 has scanned in the direction of the X axis. Then, the scanning in the direction of the Y axis is performed with the slit S2. Therefore, the intensity distribution of the light in the directions of the X axis and the Y axis and the size and the shape of the cross section of the light beam are measured based on the amounts of the light passing the slits S1 and S2 and the advancing distance of the slits.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the intensity distribution of a light beam emitted from a light source such as a laser or a light emitting diode.

[Conventional technology]

Light sources such as lasers and light emitting diodes are used in a wide variety of fields, taking advantage of their respective characteristics, and there is a need to clarify the cross-sectional intensity distribution, shape, size, etc. of the light beams.

If you want to know the cross-sectional shape of a light beam, you can visually confirm the approximate shape by placing a screen perpendicular to the direction of travel, but if the beam diameter is small or invisible infrared or ultraviolet light cannot be confirmed. .

Therefore, there are several methods for measuring the cross-sectional shape, intensity distribution, size, etc. of these light beams, and some of them are actually used, which will be described below.

Pinhole method: Place a pinhole on a screen that does not allow light to pass through (a pinhole that is sufficiently smaller than the beam diameter to be measured; for example, if an accuracy of 1% is required, install a pinhole with an area of 1% or less of the beam diameter). By moving the pinhole, the light beam is scanned vertically, and by receiving the light passing through the pinhole with a photodetector, the intensity distribution of the light beam can be determined. Also, the diameter of the light beam can be determined from the travel distance required for the pinhole to cross the light beam. It is used to detect. However, when measuring the light beam diameter,
The pinhole must pass through the center of the light beam,
There are problems in that it is difficult to set the position of the pinholes, and that installing a large number of pinholes makes the positioning easier but becomes more expensive.

Wire method A moving wire is passed through a light beam, and the scattered light is received and measured by a photodetector, but since the light-receiving area of the photodetector is finite, this method receives all of the scattered light. The problem is that moving the wire changes the distance to the photodetector, which changes the angle of the received scattered light, so even if the intensity distribution is uniform, the received light intensity will change. Another problem is that the photodetector can be moved in synchronization with the wire in order to keep the light receiving angle constant, but this has the disadvantage that the structure becomes complicated.

Knifetsu method A knife is scanned, the light that passes through it is received by a photodetector, and the change in the light is extracted. This requires a large dynamic range in the photodetector. In addition, since the signal from the photodetector does not directly correspond to the intensity distribution, an electric circuit is required to extract changes from the signal, which results in a complicated configuration.

Slit method As shown in Figure 1, a slit 2 is provided on a scanning plate 1, a light beam is scanned by the slit 2, and the light passing through the slit 2 is received by a photodetector 3 and measured. It is widely used because it is easier to handle than other methods. In FIG. 1, numeral 4 indicates a micrometer, and B indicates a cross section of the light beam.

In contrast to the scanning method described above, there is also a method of scanning a light beam using a rotating mirror such as a Galpa meter, but this method is not often used because the device becomes large and the optical design is somewhat complicated.

On the other hand, when rapid measurement is required, a method is used in which a slit or the like is mounted on a rotating disk or a rotating cylinder and scanned. These methods can be fixed behind a slit etc. by using a photodetector with a light-receiving area larger than the diameter of the light beam being measured. Furthermore, since rotation is used, the scanning speed is stable and rapid measurement is possible.

However, the cross-section of the light beam to be measured is rarely point-symmetric, and often exhibits an ellipse or complex intensity distribution.When measuring the cross-sectional shape and intensity distribution of such a light beam - axial scanning clearly It won't happen. Therefore, it is necessary to scan in two axes, the X-axis and the Y-axis, and measure the state of each. However, in the conventional method explained so far, after measuring the ■ axis, the light source or scanning direction must be rotated 90 degrees to measure the second axis, making it impossible to measure in real time in the X and Y directions. could not. Furthermore, when measuring the focus, it is necessary to ensure that the front and back positions of the slit etc. do not change when the scanning direction is changed, so the measuring device is required to have high mechanical accuracy.

[Problem to be solved by the invention]

An object of the present invention is to provide a method that allows measurement of the intensity distribution in the X and Y axes of a cross section of a light beam by only one scan.

[Means to solve the problem]

The present invention was made to solve the above problems,
Two types of slits with different inclination directions making an angle of 45° with respect to the perpendicular to the moving direction are provided in a scanning body such as a scanning plate, a scanning rotating drum, a scanning disk, etc., and the slits are made to cross the light beam at right angles, and The light beam is characterized in that the light passing through the slit is received by a photodetector, and the intensity distribution of the light beam is detected from the position of the slit and the change in the amount of light received by the photodetector corresponding to the position. This is a method of measuring intensity distribution.

〔Example〕

FIG. 2 is a side view of an embodiment of the present invention, in which the scanning plate 5 is provided with SzSz (two types of swans with different diagonal directions) at an angle of 45° with respect to the perpendicular to the moving direction. In this case, the swan) SzSz are provided in a V-shape, but they may be provided in an inverted V-shape.

Now, like the conventional device shown in Fig. 1, the micrometer 4
By operating the scanning plate 5 to move it in the direction of the arrow, it becomes possible to simultaneously measure the two axes of X and Y by scanning at -degrees.

That is, as shown in FIG. 3(a), when the slit S+ moves from a to c, d, and e, the slit S becomes
This means scanning in the axial direction, and then scanning in the Y-axis direction by the slit S2.

That is, in this case, if the moving speed of the scanning plate 5 is 1, S3. By setting Sz at 45 degrees with respect to the perpendicular, the movement speed is in the X-axis direction, and scanning in the X and Y axes directions is performed at the same movement speed.

Therefore, slit S1. The light intensity distribution in the X-axis and Y-axis directions and the size and shape of the light beam cross section can be measured from the amount of light passing through S2 and the slit traveling distance.

Since the method of processing the detection signal is obvious from the prior art, the description thereof will be omitted.

FIG. 4 shows an embodiment of a device for measuring the intensity distribution and intensity 50% of a light beam and the cross-sectional diameter of an intense light beam when a scanning rotary drum is used as a scanning body. 8 is a scanning device according to the present invention, 8 is an oscilloscope, and 9 is a light beam diameter digital display device.

5 and 6 show the internal structure of the scanning device 7, with FIG. 5 being a partially cutaway plan view and FIG. 6 being a partially cutaway side view.

71 is a scanning rotary drum driven by a motor 72, and the side wall has four slits S, 1°S1□+ at equal intervals.
S Zl+ S Z□ are provided as shown in the developed view of FIG. The sets of slits S, , S, □ have a slit width of 2μ, and the sets of slits Sz+, Sz□O have a slit width of 25μ, and both are installed at an angle of 45° with respect to the perpendicular to the moving direction. ing.

Reference numeral 73 denotes a speed and rotational position detection disk fixed on the scanning rotary drum 71, and the speed and rotational position are detected by sensors 74 and 75 and by a sensor 76, respectively.

77 is a photodetector attached to the motor 72, and when a light beam enters a window 78 provided in the housing, Surin+-S,...
, S, □ + 321 + S Z The signal is sent to the oscilloscope 8 via a light beam diameter digital display 9.

When the slit switching knob 91 is set to the 25μ display, the slit SII is selected.

The detection signal of the amount of received light that has passed through S +z is selected, and 2μ
When the signal is adjusted to the display 92a, the detection signal of the amount of light received passing through the slit Sz+ + Sz□ is selected.

92b displays the X-axis and Y-axis light beam diameters of the light intensity portion set by the level setters 93a and 93b. Usually, the diameter of the light beam at 50% intensity or 13.5% intensity of the light beam is displayed.

On the other hand, the display screen of the oscilloscope 8 shows two waveforms generated by the slit S III 5I21 as shown in the figure.
The intensity distribution in the X-axis direction and the intensity distribution in the Y-axis direction are displayed.

The scanning device 7 is rotatably attached to the stand 80, so pinch the knob 79 and rotate the scanning device 7 around the incident optical axis to change the X-axis and the X-axis. The shape of the cross section of the light beam can be determined by observing changes in the displayed waveform.

That is, from the image of the oscilloscope 8, the intensity distribution of the light on the X- and Y-axes and the cross-sectional shape of the light beam are displayed, and the diameter of the X- and Y-axes at the set level is displayed in real time using the light beam diameter digital display device 9. You can find out.

Above, the embodiment shown in FIG. 2 using a scanning plate and the embodiment shown in FIGS. 4 and 5 using a scanning rotating drum have been illustrated as scanning bodies, but when using a rotating disk The present invention is also applicable to

However, the method applied to a rotating disk causes more errors than the other two cases because the speeds at both ends of the slit are different, so it is not very suitable for specifications that require precision.

〔Effect of the invention〕

According to the present invention, it is possible to simultaneously detect the intensity distribution of light in the X-axis direction and the Y-axis direction in real time, and it is also possible to detect the diameters of the X-axis and Y-axis and the cross-sectional shape of the light beam. .

[Brief explanation of the drawing]

FIG. 1 is a side view of a scanning device using the conventional slit method, FIG. 2 is a side view of an embodiment of the present invention, FIG. 3 is an explanatory diagram of the scanning principle of the present invention, and FIG. 4 is a different embodiment of the present invention. 5 is a partially cut-away plan view of the scanning device in the embodiment shown in FIG. 4; FIG. 6 is a partially cut-away side view of the scanning device; FIG. FIG. 7 is a developed view showing the arrangement of the slits. 1.5...Scanning plate 2...Slit 3...Photodetector 4...Micrometer 6...Laser generator 7...Scanning device 7I...Scanning rotating drum 72... Motor 73...speed and rotational position detection disc 74.75
．． 76...Sensor 77...Photodetector 78...Empty 79...Knob 80...Stand 8...Oscilloscope 9...Light beam diameter digital display device 91.94...Switching knob 92a, 92b...Display portions 93a, 93b...Level setter St7...Scanning device 71...Scanning rotary drum 72...Motor 73...Speed and rotational position detection disc for 74.75
．． 76...Sensor 77...Photodetector 78...Window

Claims (1)

[Claims] Two types of slits with different inclination directions making an angle of 45 degrees with respect to the perpendicular to the moving direction are provided in a scanning body such as a scanning plate, a scanning rotation drum, a scanning disk, etc., and the slits are made to cross the light beam at right angles, and A light beam characterized in that the light passing through the slit is received by a photodetector, and the intensity distribution of the light beam is detected from the position of the slit and the change in the amount of light received by the photodetector corresponding to the position. How to measure the intensity distribution of.