JPH01265134A - Measuring instrument for energy absorption factor of condensing lens - Google Patents

Abstract

PURPOSE:To measure a temperature of a condensing lens in a stable thermal equilibrium state by placing a shielding plate in a focus of a laser beam between the condensing lens and an integrating sphere. CONSTITUTION:A condensing lens 1, a scattering reflected light shielding plate 2 having a pin hole, and an integrating sphere 3 are placed in a laser optical path. By moving one of said three along the optical axis, the shielding plate 2 is placed in a focal position of a laser beam, only the laser beam is allowed to pass through, and also, shielding is executed so that the condensing lens is not irradiated by the scattering reflected light. Also, the integrating sphere is placed so as to receive through an aperture 11 of the laser beam which has passed through the pin hole of the shielding plate 2. Under this arrangement, the laser beam is led into the condensing lens 1 being an object to be measured, its passing light is received by the integrating sphere 3 through the shielding plate 2, and a temperature variation of the condensing lens 1 is detected by a thermocouple. Subsequently, this detected value and a detector signal of the integrating sphere are sent to a data logger, and the energy absorption factor of the condensing lens is derived.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a condenser lens, which is one of optical components for a laser;
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This invention relates to an energy absorption rate measuring device for industrial optical lenses for high-output lasers such as CO, YAG, etc.

(Prior art) When measuring the energy absorption rate of a laser condensing lens using the laser calorimetry method, the focal length of the condensing lens, which is the object to be measured, varies. It was difficult to capture this with a power meter, making accurate measurement impossible. In addition, there are problems in that the scattered reflected light from a power meter, etc. disturbs the thermal equilibrium around the condenser lens, and the condenser lens is directly irradiated, giving an error in the measured value of the temperature change of the condenser lens. Ta.

(Problems to be Solved by the Invention) The present invention solves the above problems and accurately determines the energy absorption rate of a condenser lens with various focal lengths by eliminating the influence of scattered reflected light. The aim is to provide a device that can perform measurements.

(Means for Solving the Problems) The present invention provides an apparatus for measuring the energy absorption rate of a condensing lens using a laser calorimetry method. A light shielding plate and an integrating sphere with the aperture facing the laser beam path are placed, a moving means is provided to place the shielding plate at the focal position of the laser beam, and a thermocouple is attached to the side surface of the condensing lens. and a data logger that collects signals from a detector of an integrating sphere. Note that the shielding plate is made of a material having a property of reflecting infrared light, such as copper or aluminum.

(Function) FIG. 1 is a conceptual diagram of an apparatus for measuring energy absorption rate of a condenser lens, which is a specific example of the present invention.

By arranging a condensing lens 11, a scattered reflection light shielding plate 2 having a pinhole, and an integrating sphere 3 in the laser beam path, and moving any one of the above three along the optical axis, the focal length of the laser beam can be adjusted. A shielding plate 2 is placed to allow only the laser beam to pass through and to shield the scattered reflected light from irradiating the condenser lens. Furthermore, the integrating sphere 3 is arranged so as to receive all of the laser light that has passed through the pinhole of the shielding plate 2 through the aperture.

Under the above arrangement, the laser beam is introduced into the condensing lens that is the object to be measured, passes through the pinhole and aperture of the shielding plate, is received by the integrating sphere, and the temperature change of the condensing lens is detected by a thermal lightning pair. This is sent together with the signal from the integrating sphere detector to the data logger to determine the energy absorption rate of the condenser lens.

In this way, by placing the shielding plate at the focal point of the laser beam between the condenser lens and the integrating sphere, all of the laser beam that has passed through the condenser lens is introduced into the integrating sphere via the pinhole, and It was possible to prevent the scattered reflected light from the integrating sphere from irradiating the condenser lens, and as a result, it became possible to measure the temperature of the condenser lens in a stable thermal equilibrium state.

(Example) Using the apparatus shown in FIG. 1, the temperature rise of the condenser lens due to laser light irradiation and the temperature drop after laser light cutoff were measured.

The condenser lens was made of Zn5e and had a focal length of 63.51. The shielding plate was made of Cu, had a thickness of 2 cm, and had a pinhole diameter of 0.5 mm. Also, the integrating sphere is Cur
M has a diameter of 152 cm, the target is a cone with a diameter of 25.4 m and a height of 5 cm, and the aperture diameter is 25.4 -
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Figure 2 is a graph showing the above experimental results, and shows the absolute sum of the differential coefficients at the same temperature when the temperature of the condensing lens increases due to laser beam irradiation and when the temperature decreases after shielding the laser beam. It was found that the variation in points was within 1.01%, indicating that the temperature was in a stable thermal equilibrium state.

Note that when an experiment similar to the above was conducted without using a shielding plate, the variation was 10 times greater than the above.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an apparatus for measuring the energy absorption rate of a condensing lens as a specific example of the present invention, and FIG. 2 is a graph showing the results of measuring the absorption rate of the condensing lens in the example.

Claims (1)

[Claims] In an apparatus for measuring the energy absorption rate of a condensing lens using the laser calorimetry method, a condensing lens, which is an object to be measured, a scattered reflection light shielding plate having a pinhole, and an aperture are directed toward the laser beam path. Place an integrating sphere, provide a means for moving the shielding plate to the focal position of the laser beam, attach a thermocouple to the side surface of the condensing lens, and input signals from the thermocouple and the detector of the integrating sphere to a data logger. An apparatus for measuring energy absorption rate of a condenser lens, characterized in that: