JPH06213766A - Method for measuring scattering light and distribution of scattering angle - Google Patents

Abstract

PURPOSE:To provide a method for measuring the scattering light of an optical element and the distribution of the scattering angle easily by means of a same equipment while enhancing the detecting capacity in the vicinity of the axis of reflected light. CONSTITUTION:In a method for measuring the scattering light from an optical element using an integrating sphere, scattering light in the vicinity of the axis of reflected light leaked through a hole made in the integrating sphere in order to release the reflecting light is reflected on a concave mirror for reflecting the scattering light disposed around the extension of the axis of reflecting light at a position remote from the integrating sphere and returned back to the integrating sphere side thus enhancing the detecting capacity of scattering light in the vicinity of the axis of the reflecting light. Furthermore, the integrating sphere or a measuring sample is moved in parallel along the axis of incident light in an equipment for detecting the scattering light from an optical element using an integrating sphere, and the scattering light is measured at each position while limiting the scattering angle of the scattering light being taken into the integrating sphere thus obtaining the scattering angle distribution of scattering light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring scattered light and scattering angle distribution of an optical element used in various optical devices such as a laser oscillator and a laser processing machine.

[0002]

2. Description of the Related Art These optical elements generate scattered light due to surface roughness or scratches, and the scattered light causes a loss of reflected or transmitted energy or is detected as noise light to deteriorate optical performance. Therefore, it is necessary to quantitatively measure and confirm whether or not the scattered light and the scattering angle distribution are within a desired range.

Conventionally, as a method of measuring this kind of scattered light, for example, there is a method using an integrating sphere as shown in FIG. In this method, an optical element serving as a measurement sample and a detector for detecting scattered light are arranged on an integrating sphere, and when detecting scattered light with respect to incident light having an incident angle of 0 °, for example, in FIG. When light is incident from the incident / reflected light hole provided on the integrating sphere as shown in), the reflected light from the measurement sample surface is allowed to escape from the same hole, and scattered light is detected for incident light with an incident angle α. As shown in Fig. 1 (b), the reflected light from the sample surface is allowed to escape from the reflected light hole different from the incident light hole, only the scattered light is caught by the integrating sphere, and the light intensity of the scattered light is detected. It is something that is detected by a vessel. It should be noted that the calibration of the absolute value of the scattering intensity is 100% at the position of the measurement sample.
This is done by the ratio with the scattered intensity detected with a scattering object scattered.

The total amount of scattered light is detected by the method of FIG. 1 using an integrating sphere. Regarding the strong scattering intensity in which scattering angle direction (scattering angle distribution), the integrating sphere is used. It was measured by another device that was not used. This scattering angle distribution is measured by, for example, irradiating the measurement sample directly with incident light as shown in FIG. The scattered light from the surface of the measurement sample is measured.

[0005]

However, in the method of measuring scattered light described above, scattered light near the optical axis of the reflected light (where the scattering angle θ is close to 0 °) passes through the hole through which the reflected light passes. Since it escapes to the outside, the ability to detect scattered light near the optical axis is significantly reduced. When the incident angle is α, the scattered light leaks from the hole through which the incident light passes, but the scattered light in the vicinity of the reflected light is much larger than the scattered light in the vicinity of the incident light. Only the leakage of scattered light near the light becomes a problem. In this case, as a means of increasing the detection capability, it is sufficient to set the diameter of the hole as small as possible up to the optical path through which the reflected light passes, but in reality, due to problems such as adjustment problems, the diameter of the hole should have a certain margin. It was necessary and not a valid solution. Further, although the resolution is improved by increasing the distance A between the measurement sample and the hole through which the reflected light passes,
In this case, since the diameter of the integrating sphere becomes large, the intensity of light entering the photodetector decreases, and other problems such as an increase in size and cost of the device occur. The length of the distance A cannot be increased.

When a device different from the scattered light measuring device using the integrating sphere is used as in the method for measuring the scattered angle distribution of scattered light, it is necessary to prepare two types of devices. However, there is a problem in that the equipment cost is increased and the measurement sample must be replaced each time, which makes the work complicated. Therefore, in the present invention, a method of measuring scattered light of an optical element that solves the problems of these conventional techniques and improves the scattered light detection capability in the vicinity of the reflected light axis, and the scattering angle distribution of the scattered light can be easily performed by the same device. The purpose is to provide a method that can be measured.

[0007]

In the scattered light measuring method according to the present invention, a scattered light measuring method for detecting scattered light from an optical element using an integrating sphere is provided on the integrating sphere for allowing reflected light to escape. Scattered light near the reflected light axis leaking from the hole is reflected by a concave mirror for scattered light reflection arranged around the extension of the reflected light axis away from the integrating sphere and returned to the integrating sphere side. The ability to detect scattered light in the vicinity was improved.

In the method for measuring the scattering angle distribution of scattered light according to the present invention, an integrating sphere or a measurement sample in an apparatus for detecting scattered light from an optical element using an integrating sphere is moved in parallel along the incident optical axis, The scattered light at each position is measured with the scattering angle of the scattered light taken into the integrating sphere being limited.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below in detail with reference to the illustrated embodiments. FIG. 3 shows an embodiment for improving the scattering detection capability in the vicinity of the reflected light axis. As shown in this drawing, an integrating sphere is provided with an optical element serving as a measurement sample and a scattered light detector. However, for example, in the case of detecting scattered light with respect to incident light having an incident angle of 0 °, light is made incident through the incident / reflected light hole provided on the integrating sphere as shown in FIG. When the reflected light is allowed to escape from the same hole and the scattered light with respect to the incident light of the incident angle α is detected, the reflected light from the sample surface is different from the incident light hole as shown in FIG. 3B. The light is allowed to escape from the light hole, only the scattered light is captured by the integrating sphere, and the light intensity of the scattered light is detected by the detector. Further, around the extension of the reflected light axis away from the integrating sphere, a concave mirror for scattering light reflection that reflects scattered light in the vicinity of the reflected light axis leaking to the outside through a hole for letting the reflected light escape to the integrating sphere side Is provided.

In this embodiment, a concave mirror with a hole is arranged as a concave mirror for scattering light reflection in a mode orthogonal to the reflection optical axis,
This perforated concave mirror allows the reflected light to pass through through a through hole formed in the center located on the reflected light axis,
The scattered light in the vicinity of the reflected light axis that has escaped to the outside through the reflected light hole of the integrating sphere is reflected by the concave surface portions on both sides of the through hole and returned to the integrating sphere. As a result, the distance A between the measurement sample and the hole through which the reflected light passes is substantially increased, and the ability to detect scattered light near the reflected light axis is improved. Further, in this method, the diameter of the integrating sphere can be small, so that it is possible to increase the light intensity with respect to the photodetector or downsize the device to reduce the cost. The concave mirror for scattering light reflection may not be a perforated concave mirror as in the illustrated embodiment, but a concave mirror may be simply arranged around the extension line of the reflected light axis.

Next, FIG. 4 shows a method of measuring the scattering angle distribution of scattered light using an integrating sphere. For this method, the same device as the above-mentioned method for measuring scattered light is used, and the integrating sphere or the measurement sample can be moved in parallel along the incident optical axis. When one of the integrating sphere and the measurement sample of this device is translated along the incident optical axis, the scattering angle taken into the integrating sphere changes in accordance with the distance between the integrating sphere and the measurement sample. The scattered angle distribution can be obtained by measuring the scattered light with the detector each time while changing the relative position of the two. For example, if the distance between the two is increased, only the scattered light having a small scattering angle is taken into the integrating sphere, and if the distance between the two is decreased, the scattered light having a large scattering angle can be taken into the integrating sphere. The intensity of scattered light taken into the integrating sphere is sequentially measured by a detector in the state where the distances are variously separated from each other, and the dependence of the scattering intensity on each scattering angle, that is, the scattering angle distribution is measured.

When the integrating sphere and the measurement sample are moved relative to each other, the measuring sample may be fixed and the integrating sphere may be moved, or the integrating sphere may be fixed and the measuring sample may be moved. This is desirable because it allows easier measurement while maintaining mechanical accuracy.In the latter case, when the angle of the measurement sample with respect to the incident light changes due to mechanical error during movement, the direction of the reflected light becomes delicate. May change. In this method of measuring the scattering angle distribution, the scattering angle distribution can be measured simply by translating the integrating sphere or the measurement sample along the incident optical axis using the same device as the scattered light measurement. The equipment cost can be reduced as compared with the method, and the operation is extremely easy because it is not necessary to replace the measurement sample each time.

[0013]

In the method for measuring scattered light according to the present invention, a concave mirror for scattering scattered light, which is arranged around the extension of the reflected light axis away from the integrating sphere, allows the reflected light to escape to the outside through the hole. The leaked scattered light near the reflected light axis is reflected to the integrating sphere side, and the distance A between the measurement sample and the hole through which the reflected light passes is substantially increased to improve the detection ability for scattered light near the reflected light axis. In addition to the improvement, it is possible to reduce the cost by reducing the diameter of the integrating sphere used to increase the light intensity of the scattered photodetector and downsizing the device. Further, in the method for measuring the scattering angle distribution of scattered light according to the present invention, the scattering angle distribution can be obtained by simply translating the integrating sphere or the measurement sample along the incident optical axis using the same device as the above-described method for measuring scattered light. Because you can measure
The equipment cost can be reduced as compared with the conventional method, and the operation is very easy because it is not necessary to replace the measurement sample each time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a method for measuring scattered light according to a conventional example.

FIG. 2 is an explanatory diagram showing a method of measuring a scattering angle distribution of scattered light according to a conventional example.

FIG. 3 is an explanatory diagram showing a method for measuring scattered light according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a method for measuring a scattering angle distribution of scattered light according to an embodiment of the present invention.

Claims (2)

[Claims] 1. A scattered light measuring method for detecting scattered light from an optical element using an integrating sphere, wherein scattered light near a reflected light axis leaking from a hole provided in the integrating sphere for letting the reflected light escape , Characterized in that it is reflected by a concave mirror for scattered light reflection disposed around the extension line of the reflected light axis away from the integrating sphere and returned to the integrating sphere side to improve the ability to detect scattered light in the vicinity of the reflected light axis. For measuring scattered light. 2. An integrating sphere or a measurement sample in an apparatus for detecting scattered light from an optical element using an integrating sphere is moved in parallel along an incident optical axis to limit a scattering angle of scattered light taken into the integrating sphere. A method for measuring the scattering angle distribution of scattered light, which comprises measuring the scattered light at each position in the above state.