JP2666032B2 - Measurement method of scattering light and scattering angle distribution - Google Patents

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 scattered angle distribution of an optical element used for various optical devices such as a laser oscillator and a laser beam machine.

[0002]

2. Description of the Related Art In these optical elements, scattered light is generated due to surface roughness or scratches, and the scattered light causes loss of reflected or transmitted energy or is detected as noise light, thereby deteriorating optical performance. Therefore, it is necessary to quantitatively measure and confirm whether the scattered light and the scattering angle distribution are within a desired range.

Conventionally, as a method for measuring this kind of scattered light, 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 provided in an integrating sphere. For example, when detecting scattered light with respect to incident light having an incident angle of 0 °, FIG. ), Light is made to enter from the incident and reflected light hole provided in the integrating sphere so that the reflected light from the measurement sample surface escapes from the same hole, and the scattered light is detected with respect to the incident light at the incident angle α. As shown in FIG. 1 (b), the reflected light from the sample surface is allowed to escape from a reflected light hole different from the incident light hole, and only the scattered light is captured by an integrating sphere to detect the light intensity of the scattered light. It is detected by a container. The absolute value of the scattering intensity is calibrated by 100% at the position of the measurement sample.
This is performed by the ratio of the scattering intensity detected by placing a scattering object to be scattered.

[0004] The total amount of scattered light is detected by the method of FIG. 1 using an integrating sphere. The intensity of the scattered light and the intensity of the scattered light (scattering angle distribution) are determined by using the integrating sphere. It was measured by another instrument not used. In the method of measuring the scattering angle distribution, for example, as shown in FIG. 2, a measurement sample is directly irradiated with incident light, and a photodetector disposed in front of the measurement sample is sequentially moved at predetermined angle positions. This is for measuring the scattered light from the measurement sample surface.

[0005]

However, in the method for measuring the scattered light described above, the 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 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 near the reflected light is much larger than the scattered light near the incident light. Only leakage of scattered light in the vicinity of light becomes a problem. In this case, as a means of improving the detection capability, the diameter of the hole may be set as small as possible to the optical path through which the reflected light passes.However, in practice, the diameter of the hole having a certain margin due to adjustment problems or the like may be reduced. Necessary and not a valid solution. 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, other problems such as a decrease in the light intensity entering the photodetector due to an increase in the diameter of the integrating sphere and an increase in the size of the device and an increase in cost occur. The length of the distance A cannot be increased.

In the case of using another device different from the scattered light measuring device using an integrating sphere as in the method of measuring the scattered light scattering angle distribution described above, it is necessary to prepare two types of devices. However, there is a problem that the equipment cost is increased and the measurement sample must be replaced each time, so that the operation becomes complicated. Therefore, in the present invention, a method of measuring the scattered light of an optical element that solves these problems of the prior art and improves the ability of detecting scattered light in the vicinity of the reflected light axis, and the scattering angle distribution of the scattered light with the same apparatus can be easily achieved. The purpose is to provide a method that can be measured.

[0007]

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

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 an incident optical axis, The scattered light at each position is measured with the scattering angle of the scattered light taken into the integrating sphere 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 embodiment. FIG. 3 shows an embodiment for improving the scatter detection ability near the reflected light axis. As shown in FIG. 3, an integrating sphere is provided with an optical element serving as a measurement sample and a scattered light detector. For example, when detecting scattered light with respect to incident light having an incident angle of 0 °, light is made incident from an incident / reflective light hole provided in an integrating sphere as shown in FIG. When the reflected light is allowed to escape from the same hole and the scattered light is detected with respect to the incident light having the incident angle α, the reflected light from the sample surface is reflected differently from the incident light hole as shown in FIG. The light is allowed to escape from the light hole, only the scattered light is captured by an integrating sphere, and the light intensity of the scattered light is detected by a detector. A scattered light reflecting concave mirror for reflecting the scattered light near the reflected light axis leaking outside through a hole for releasing the reflected light to the integrating sphere side around the extension of the reflected light axis away from the integrating sphere. Are arranged.

In this embodiment, a perforated concave mirror is disposed as a scattered light reflecting concave mirror so as to be orthogonal to the reflected optical axis.
This perforated concave mirror allows the reflected light to pass through as it is through the through hole formed in the center located on the reflected optical axis,
The scattered light in the vicinity of the reflected optical axis that has escaped through the reflected light hole of the integrating sphere is reflected by the concave portions on both sides of the through hole and returned to the integrating sphere. This substantially increases the distance A between the measurement sample and the hole through which the reflected light passes, thereby improving the ability to detect scattered light near the reflected light axis. 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 reduce the size of the apparatus to reduce the cost. The concave mirror for reflecting scattered light may not be a perforated concave mirror as in the illustrated embodiment, but may be simply provided around the extension of the reflected optical axis.

FIG. 4 shows a method for measuring the scattering angle distribution of scattered light using an integrating sphere. In this method, the same apparatus as that for measuring the scattered light described above is used, and the integrating sphere or the measurement sample can be translated along the incident optical axis. If one of the integrating sphere and the measurement sample of this apparatus is translated along the incident optical axis, the scattering angle taken into the integrating sphere changes according to the distance between the integrating sphere and the measurement sample. When the scattered light is measured by the detector each time while changing the relative positions of the two, a scattering angle distribution is obtained. For example, when the distance between the two is increased, only the scattered light having a small scattering angle is captured in the integrating sphere, and when the distance between the two is reduced, even the scattered light with a large scattering angle can be captured in the integrating sphere. The intensity of the scattered light taken into the integrating sphere in a state where the distances are variously approached and separated is sequentially measured by a detector, and the dependence of the scattered intensity on each scattering angle, that is, the scattering angle distribution is measured.

When the integrating sphere and the measurement sample are relatively moved, either the fixing of the measuring sphere and the moving of the integrating sphere or the fixing of the integrating sphere and the moving of the measurement sample may be performed. It is desirable to measure the angle of the sample with respect to the incident light due to the mechanical error during movement. May change. In the method of measuring the scattering angle distribution, the scattering angle distribution can be measured only by translating the integrating sphere or the measurement sample along the incident optical axis using the same apparatus as that for measuring the scattered light. 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]

According to the method for measuring scattered light according to the present invention, a concave mirror for reflecting scattered light disposed around an extension of the reflected light axis away from the integrating sphere to the outside through a hole through which reflected light escapes. The leaked scattered light in the vicinity of the reflected light axis is reflected toward the integrating sphere, and the distance A between the measurement sample and the hole through which the reflected light passes is substantially increased. It is possible to increase the light intensity of the scattered light detector by reducing the diameter of the integrating sphere to be used and to reduce the size of the apparatus to reduce the cost. 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 apparatus 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 extremely easy because there is no need to replace the measurement sample each time.

[Brief description of the drawings]

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

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

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

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

Claims (2)

(57) [Claims] 1. A scattered light measuring method for detecting scattered light from an optical element using an integrating sphere, wherein the scattered light in the vicinity of a reflected light axis leaking from a hole provided in the integrating sphere for allowing the reflected light to escape. It is characterized by improving the ability to detect scattered light near the reflected optical axis by reflecting it with a scattered light reflecting concave mirror arranged around the extension of the reflected optical axis away from the integrating sphere and returning it to the integrating sphere side. Scattered light measurement method. 2. An apparatus for detecting scattered light from an optical element using an integrating sphere, wherein an integrating sphere or a measurement sample 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 scattered light distribution of scattered light, wherein the scattered light at each position is measured in a state where the scattered light is measured.