JP2001183256A - Coating film inspection apparatus and inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a inspection apparatus and inspection method for accurately and quickly evaluating the performance of a coating film of an optical part. SOLUTION: This coating film inspection film apparatus for inspecting the coating film 28 of an optical part for ultraviolet light is provided with a inspection light radiating device 43 for applying inspection light 45 to the coating film 28 of the optical part, and a non-contact thermometer 48 for measuring the temperature of the coating film 28 to test the coating film 28 according to a temperature change of the coating film 28. The apparatus is provided with a light intensity measuring device for measuring the intensity of scattered light 35 irregularly reflected from the coating film 28 to inspect the coating film 28 according to the intensity of the scattered light 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for inspecting a coating film of an optical component for ultraviolet light.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique of inspecting an optical component by measuring the light absorption of a translucent optical component.
For example, it is disclosed in JP-A-11-72416.
FIG. 10 shows a light absorbance measuring apparatus disclosed in the publication, and a conventional technique will be described below with reference to FIG.

[0003] In FIG.
An inspection laser beam 102 having a predetermined energy density oscillated from the inspection laser 101 is applied to a prism 103 for a predetermined time.
The temperature rise of the prism 103 is measured by bringing a temperature sensor 104 such as a resistance temperature detection type into contact with the surface of the prism 103 through which the inspection laser beam 102 does not pass. Then, the prism 103 whose temperature has risen above the acceptance standard is determined to be inappropriate, and the prism 103 is inspected so as not to be incorporated in the laser device. At this time, the reference temperature sensor 105 is provided near the prism 103 to measure the ambient temperature to improve the inspection accuracy.

[0004]

However, the prior art has the following problems. That is, it is general to coat the surface of an optical component for ultraviolet light such as that used for an ultraviolet laser with a coating film made of a dielectric multilayer film in order to prevent loss due to irregular reflection or absorption of ultraviolet light. . However, in this coating step, if impurities are mixed in the coating film or the thickness does not reach a predetermined value, the coating film absorbs the inspection laser beam 102 and takes on heat, and the refractive index may fluctuate. As a result, the inspection laser light 10
The wavefront 2 may be disturbed, and the performance such as the center wavelength, the line width, the beam profile, or the power may be reduced. In extreme cases, the heat may cause the optical components to deteriorate or be damaged. Therefore, when inspecting the performance of an optical component, it is necessary to examine whether or not the heat absorption of such a coating film is within an allowable range.

However, in the prior art, the temperature sensor 104 is brought into contact with the prism 103 to measure the temperature rise.
03, the temperature rise of the entire coating film cannot be measured independently. Therefore, it is necessary to determine whether the rise in the temperature of the prism 103 is caused by a defect in the coating film or is caused by a cause other than the coating film, for example, the non-uniformity of the optical material used for the prism 103. Is difficult. That is, in the prior art, all optical components that cause heat absorption are defective, so even if it is effective as an acceptance test, the cause of the optical component failure cannot be determined, and based on the result, the defect of the optical component is determined. It is also difficult to reduce the rate.

Also, since the prism 103 has a larger heat capacity than the coating film, the temperature change of the prism 103 is smaller than the temperature change of the coating film. However, the refractive index of the coating film fluctuates even with a slight change in temperature, and the wavefront is disturbed, which adversely affects the wavelength. Therefore, there is a problem that the inspection means for measuring the temperature of the prism 103 has insufficient accuracy to detect a change in the refractive index due to a slight change in the temperature of the coating film. In addition, due to the heat capacity of the prism 103, a time delay occurs before the temperature change of the coating film affects the temperature of the prism 103. Therefore, the prism 10
There is a problem that it takes a long time for the inspection to measure the temperature of No. 3.

If the defect of the coating film causes heat absorption, the optical material can be reused by peeling off the coating film of the optical component and recoating. However, according to the prior art, the cause of heat absorption cannot be separated into those caused by defective coating and those caused by other factors. Therefore, a part determined to be abnormal must be discarded as a defective product or re-melted, which causes a problem that the optical material is wasted and that it takes much time for reproduction.

The coating film is for transmitting or reflecting the incident laser light 11 with as little loss as possible, and it is better that the absorption or irregular reflection which causes loss is smaller. However, if there is unevenness or unevenness in the thickness of the coating film, the coating film may irregularly reflect the laser light in a direction other than a predetermined direction, and the transmittance and the reflectance of the optical component decrease, resulting in energy loss. . Also, the diffusely reflected light is mixed with the oscillating laser light and emitted,
The wavelength quality of the laser light may be degraded. However, since the scattered light irregularly reflected does not increase the temperature of the coating film, the conventional technique of measuring only the heat absorption of the prism 103 cannot inspect such a defect of the coating film. There is.

Further, according to the prior art, the temperature sensor 104 is pressed against the prism 103 by a spacer such as Teflon in order to improve the accuracy of temperature measurement. However, since the inspection laser light 102 is irregularly reflected and scattered on the surface of the prism 103 and the like, the inspection laser light 102 is also applied to the Teflon resin. As a result, an impurity gas of an organic substance is generated from Teflon, and the impurity gas may adhere to the prism 103 and contaminate it. When the inspection laser beam 102 is applied to the contaminated portion, the prism 103 is damaged by heat. Further, if a metal spacer is used instead of the Teflon spacer, there is a problem that the metal spacer absorbs the heat of the prism 103 and an error in temperature measurement increases. Further, for example, if the temperature sensor 104 is attached to the prism 103 with an adhesive or the like, there is also a problem that the adhesive is irradiated with the inspection laser beam 102 to generate an impurity gas. That is, it is very difficult to accurately measure the temperature of the optical component using only the contact temperature sensor 104 without damaging the optical component.

Further, the prior art only describes a technique for inspecting a translucent optical component such as the prism 103, but does not describe an inspection of a reflective optical component such as a mirror. As described above, there is a demand for an inspection means capable of determining the quality of a coating film for all optical components such as a mirror.

The present invention has been made in view of the above problems, and has as its object to provide an inspection apparatus and an inspection method for accurately and quickly evaluating the performance of a coating film of an optical component. I have.

[0012]

In order to achieve the above object, a first invention is a coating film inspection apparatus for inspecting a coating film of an optical component for ultraviolet light. An inspection light irradiator that irradiates inspection light and a non-contact type thermometer that measures the temperature of the coating film are provided.

According to the first invention, the temperature of the coating film of the optical component is measured by the non-contact type thermometer, and the coating film is evaluated based on the measurement. The coating film absorbs ultraviolet light and takes heat,
The refractive index fluctuates. Therefore, by measuring the temperature, fluctuation or deterioration of the refractive index can be detected, and the performance of the coating film can be evaluated. In addition, since the radiation thermometer is used at the time of temperature measurement, it is possible to accurately measure the temperature change of the coating film surface without being affected by the heat capacity of the optical component. Therefore, the state of the coating film can be directly grasped, and strict performance evaluation of the coating film becomes possible. Further, since the temperature change of the coating film is measured, there is no time delay of the temperature change due to the influence of the heat capacity of the optical component, and the temperature can be measured quickly and accurately. Therefore, the time required for the inspection is shortened, and the inspection accuracy is improved. Also, by using a non-contact type thermometer, there is no need to use, for example, Teflon or an adhesive to make the temperature sensor contact the optical component,
Optical components are not contaminated by generation of impurity gas.
Further, if a defect of the coating film is found, the inspection result is fed back to the coating process to improve the yield. Since it is easy to re-manufacture the optical component only by performing the coating process again, there is no need to re-melt the optical component and re-create the optical component, or to discard the optical material. Therefore, the cost for manufacturing the optical component is reduced, the labor is reduced, and the expensive optical material is not wasted.

According to a second aspect of the present invention, there is provided the coating film inspection apparatus according to the first aspect, further comprising a light intensity measuring device for measuring the intensity of scattered light irregularly reflected from the coating film.

According to the second invention, in addition to the non-contact type thermometer of the first invention, a light intensity measuring device for measuring the intensity of scattered light irregularly reflected from the coating film is provided. The coating film is for lowering the loss of ultraviolet light, and the film having an ultraviolet light absorptivity of at least causing irregular reflection has poor performance. Therefore, the performance of the coating film can be more comprehensively evaluated by measuring not only the absorptance of the inspection light but also the intensity of the irregularly reflected inspection light.

According to a third aspect of the present invention, there is provided an inspection method for inspecting a coating film of an optical component for ultraviolet light, wherein the coating film of the optical component is irradiated with inspection light to measure the temperature of the coating film, and the coating film is measured based on the temperature. We are evaluating the film.

According to the third aspect, the coating film is evaluated by measuring the temperature of the coating film irradiated with the inspection light. By measuring the temperature of the coating film, the absorptance of the inspection light absorbed by the coating film can be detected. Based on this absorptivity, it is possible to predict the fluctuation or deterioration of the refractive index of the coating film. That is, by measuring the temperature of the coating film, the performance of the coating film can be accurately evaluated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings. In each embodiment, the same reference numerals are given to the same elements as those used in the description of the related art and the drawings used in the description of the embodiment earlier than the embodiment, and the overlapping description will be omitted. I do. Less than,
The optical components used in the ultraviolet laser device will be described.

First, a first embodiment will be described. In FIG.
The structure of an ultraviolet laser device in which optical components are actually used will be described using an excimer laser as an example. In the figure,
An excimer laser 1 is a laser chamber 2 in which a laser gas is sealed and an internal discharge is performed, and a laser beam 11 is oscillated.
Windows 7 and 9 attached to the front and rear portions of the laser chamber 2 and transmitting the laser light 11, and a band narrowing unit 20 provided behind the laser chamber 2 and narrowing the wavelength of the laser light 11. And a front mirror 8 provided in front of the laser chamber 2 to transmit a part of the laser beam 11 and emit it to the outside. Prisms 22, 22 for expanding the beam width of the laser beam 11 emitted from the window 9, a grating 23 for diffracting the laser beam 11 to narrow the wavelength, and a laser beam 11 A total reflection mirror 24 for controlling the wavelength by controlling the reflection angle is provided. The laser beam 11 emitted from the front mirror 8 enters a beam splitter 12, a part of which is sampled and enters a wavelength measuring device 30. The wavelength measuring device 30 includes, for example, a monitor etalon 33, and measures the wavelength of the laser beam 11 based on the generated interference fringes.

The surfaces of the windows 7, 9, the front mirror 8, the prisms 22, 22, the grating 23, and the total reflection mirror 24 are coated with a coating film for preventing absorption of the laser beam 11 and loss due to irregular reflection. In addition, the transmittance and the reflectance of the laser beam 11 are improved. The coating film inspection apparatus of the present invention can inspect the coating films of these optical components. The surface of the beam splitter 12, the monitor etalon 33, and the like, on which the laser beam 11 is incident after the laser beam 11 exits from the front mirror 8, is also coated, so that these optical components can be inspected.

FIG. 2 shows a configuration diagram of an apparatus for inspecting a coating film of an optical component according to the present embodiment. The test object in the figure is a total reflection mirror 24 used in the band narrowing unit 20, and a surface thereof is coated with a total reflection coating film 28 for increasing the reflectance. The coating film inspection apparatus includes an inspection laser device 43 that oscillates an inspection laser beam 45 in the ultraviolet region, and an inspection that shapes the inspection laser beam 45 and irradiates the inspection target with the total reflection coating film 28 of the total reflection mirror 24, which is the inspection object. An optical system 44, a radiation thermometer 48 for measuring the temperature of the coating film 28 in a non-contact manner, and an inspection controller 49 for controlling an inspection device are provided. Since the center wavelength of the inspection laser beam 45 needs to be substantially the same as the center wavelength of the laser beam 11 oscillated from the excimer laser 1 using the total reflection mirror 24,
The inspection laser device 43 is also preferably an excimer laser. However, in the excimer laser 1, the wavelength is narrowed by the band narrowing unit 20 in order to perform precision processing well, but the band narrowing is not necessary in the inspection laser device 43.

The inspection controller 49 is composed of, for example, a personal computer or the like, reads temperature data on the surface of the coating film 28 measured by a radiation thermometer 48 electrically connected thereto, and displays the temperature distribution on a display or prints out the data. Or Then, the coating film 28 is evaluated based on the temperature distribution and the temperature change. In the following description, the term “temperature or temperature distribution” refers to a relative temperature based on an initial temperature when the test object is not irradiated with the test laser. Further, the temperature data means not only the specific numerical value of the temperature itself, such as 50 degrees, but also a parameter that reflects the temperature, such as the intensity distribution of light emitted from the coating film 28. In addition, a shutter 46 is disposed in the optical path of the inspection laser light 45, and the irradiation of the inspection laser light 45 can be cut off for a predetermined time based on a signal from the inspection controller 49.

The inspection laser device 43 has an inspection laser beam 45
Inspection laser controller 50 for controlling the oscillation of
It has. The inspection laser controller 50 is electrically connected to the inspection controller 49 and can exchange signals with each other, and controls the power of the inspection laser device 43 based on a command from the inspection controller 49.

The inspection optical system 44 shapes the inspection laser beam 45 so that the inspection laser beam 45 approaches the laser beam 11 irradiated on the inspection object in the excimer laser 1. That is, the inspection laser beam 45 is
Is shaped into the same beam profile (intensity distribution) as the laser beam 11 incident on the total reflection mirror 24 inside the narrow band unit 20 shown in FIG. FIG. 3 shows an intensity distribution of the laser beam 11 emitted from the excimer laser 1. As shown in the figure, the intensity distribution of the laser beam 11 is substantially uniform in one direction (the X direction in the figure), and the central portion is often higher in the Y direction in the figure, which is perpendicular to the direction. . The inspection optical system 44 includes the inspection laser light 4
5 is shaped so as to have such an intensity distribution, and the beam width in the X direction is widened in the same manner as that performed by the prisms 22 and 22 in the band narrowing unit 20 to irradiate the total reflection mirror 24. The incident angle at which the inspection laser light 45 enters the total reflection mirror 24, which is the object to be inspected, is made substantially equal to the incident angle at which the laser light 11 enters the total reflection mirror 24 inside the narrow band unit 20. As a result, the inspection can be performed under conditions close to the actual use conditions, and the reliability of the inspection result is improved.

A radiation thermometer 48 is placed obliquely forward of the total reflection mirror 24, and measures the temperature of the total reflection coating film 28 accompanying the irradiation of the inspection laser beam 45. Radiation thermometer 4
Numeral 8 measures the surface temperature of the test object in a non-contact manner by measuring the amount of infrared radiation emitted from the test object. still,
The inspection laser light 45 reflected by the total reflection mirror 24 is absorbed by the damper 25.

Next, a procedure for performing the inspection will be described. First, as an example of an inspection procedure performed manually, the coating film 28 is set before the inspection laser beam 45 is irradiated after the total reflection mirror 24 as an object to be inspected is set in the inspection apparatus.
Measure the initial temperature of. Then, the power and the irradiation time of the inspection laser light 45 are input to the inspection controller 49 based on the predetermined irradiation conditions, and the inspection laser light 45 is irradiated on the total reflection mirror 24. The inspection controller 49 displays a temperature distribution on the display based on the measurement data of the radiation thermometer 48 based on the initial temperature before the irradiation of the test object immediately after the end of the irradiation. The evaluation of the coating film 28
This is performed by observing the temperature distribution with the naked eye. As an example of the evaluation, the simplest and most effective method is to determine whether the maximum temperature of the coating film 28 after the irradiation for a predetermined time exceeds a predetermined allowable temperature. That is, if there is even one place where the heat absorption of the coating film 28 is larger than the allowable value, the heat intensively absorbed there spreads to the surroundings, and the contamination of the coating film 28 spreads. FIG. 4 shows the inspection controller 49.
5 shows an example of the temperature distribution displayed on the screen of FIG. For example, assuming that the area 26 indicated by oblique lines is a range exceeding the allowable temperature, the coating film 28 of the total reflection mirror 24 is defective even if there is at least one place where the temperature exceeds the allowable temperature. It is judged that it is, and coating is redone.

Next, an example in which the inspection controller 49 automatically inspects the coating based on a predetermined procedure will be described. The inspector sets the total reflection mirror 24 in the inspection apparatus, adjusts the inspection optical system, and inputs the type of the object to be inspected to the inspection controller 49. The inspection controller 49 determines the irradiation condition including the irradiation power and the irradiation time based on the type of the inspection object. Then, first, the coating film 28 is irradiated with no inspection laser light 45.
After the temperature is measured, the inspection laser beam 45 is oscillated with a preset power, a signal is transmitted to the shutter 46 to open and close, and the inspection laser beam 45 is irradiated to the inspection object for a predetermined time. That is, the irradiation conditions are changed depending on the inspection object, and the evaluation conditions may change accordingly. The radiation thermometer 48 displays the coating film 28 from the start of the irradiation of the inspection laser beam 45 until a predetermined time after the end of the irradiation.
Is transmitted to the inspection controller 49.

The inspection controller 49 controls the inspection laser beam 4
Based on the temperature change from the start of the irradiation of No. 5, the performance of the coating film 28 is evaluated, for example, as follows. In FIG.
An example of a temperature change at a specific portion of the coating film 28 is shown in a graph. In the figure, the horizontal axis is the irradiation time t, and the vertical axis is the temperature T based on the initial temperature T0 before the irradiation. That is, irradiation starts at time t1, and time t2
The temperature rise has started at a gradient k1. Then, the temperature gradually becomes saturated, and at time t3, the temperature T becomes the maximum temperature T.
M, and after the irradiation stops at time t4, the temperature T
Is falling at a gradient k2.

The evaluation condition of the coating film 28 in this example may be based on, for example, the maximum temperature TM as described above, or may be based on the temperature rise gradient k1. That is, if the temperature rise gradient k1 is equal to or higher than the predetermined gradient, it is determined that the coating film 28 is defective even if the maximum temperature TM does not reach the allowable temperature. Further, the inspection laser light 4
Based on the temperature change after time t4 when the irradiation of No. 5 was completed,
The coating film 28 is formed on the basis of the temperature drop gradient k2.
May be evaluated. At this time, it is preferable that the determination is not made based on only one determination condition such as the maximum temperature TM or the like, but is performed in combination with several conditions. For example, the maximum temperature TM
If the temperature exceeds the allowable temperature, it is determined to be defective. However, even if the individual conditions are within the allowable range, it is possible that the overall determination may be made to determine the defect.

Furthermore, the evaluation conditions are different between the prism 2 that transmits the laser beam 11 and the total reflection mirror 24 that totally reflects the light, and based on such a combination of criteria in accordance with the optical components used. It should be evaluated. In the above description, the temperature change at one specific point has been described, but the evaluation is preferably performed based on the temperature changes at a plurality of points. For example, the measurement may be performed for a plurality of predetermined points on the surface of the coating film 28, or, for example, may be performed by selecting several points of the coating film 18 where the temperature change is large.

FIG. 6 shows an example of an inspection apparatus for inspecting the prism 22. In the figure, the inspection optical system 44
Is the prism 2 inside the narrow band unit 20 shown in FIG.
The laser beam 11 is shaped by the inspection optical system 44 to have the same intensity distribution and beam diameter as the laser beam 11 incident on the laser beam 2. The inspection laser light 45 is supplied to the inspection laser light 45 having the same power by the beam splitter 42 and the mirror 39.
A, 45B, and divided into two prisms 22A, 22B, respectively.
2B is irradiated. At this time, both surfaces of the prism 22A are coated with the non-reflective coating film 28, but the surface of the prism 22B is not coated.

The surface temperatures of these prisms 22A and 22B are measured by radiation thermometers 48A and 48B, respectively, and the coating film 28 is evaluated. That is, by simultaneously measuring the temperature of the prism 22B without the coating film 28, it is possible to cancel the influence of temperature change due to factors other than the coating film 28, such as heat absorption inside the prism 22. Therefore, the temperature change of the coating film 28 alone can be grasped more accurately, and the accuracy of the inspection of the coating film 28 is improved. When inspecting the non-reflective coating film 28 on the other surface of the prism 22A, a total reflection mirror is disposed instead of the damper 25, and the inspection laser beam 45 reflected by the total reflection mirror irradiates the inspection laser beam 45. The temperature rise of the coating film 28 on the side surface is measured. Alternatively, the arrangement of the prism 22A may be changed and the inspection laser light 45 may be incident from the other surface. In this case, however, it is necessary to change the intensity distribution of the inspection laser light 45 by the inspection optical system 44.

In such an inspection apparatus, the following is an example in which the inspection of the coating film 28 of the prism 22 is actually performed. That is, the inspection laser beam 45 of 40 W / cm 2, which is almost the same as the energy density normally applied to the prism 22 as the object to be inspected.
Was irradiated for about 2 minutes. If the temperature of the coating film 28 rises by 1 degree or more, even if only partially, the prism 22 is actually mounted on the excimer laser 1, and a wavefront disorder is observed. 28 was confirmed to be defective.

At the time of such an inspection, a laser irradiated in a normal use state is anticipated in consideration of a safety factor so that heat absorption of the coating film 28 does not occur even when the optical component is used for a long time. It is preferable to irradiate the inspection laser light 45 with an energy density of one to several tens times the energy density of the light 11. Therefore, it is preferable that the inspection laser device 43 has an ability to oscillate the inspection laser light 45 at an energy density several times to several tens times that of the excimer laser 1. As for the temperature rise, since the allowable value of the maximum temperature TM was 1 degree in the embodiment, an allowable value of, for example, about 0.5 degree or less was set as an allowable value. Then, it is possible to further increase the safety factor.

As described above, according to this embodiment,
The inspection laser light 45 is irradiated on the optical component, and the temperature of the coating film 28 on the surface is measured to evaluate the coating film 28. The refractive index of the coating film 28 fluctuates by absorbing the laser beam 11 and taking heat. Therefore, by measuring the temperature when the inspection laser beam 45 is irradiated, it is possible to observe the refractive index fluctuation and deterioration, and to evaluate the performance of the coating film 28 before incorporating it into the laser device. Further, since the non-contact radiation thermometer 48 is used for temperature measurement, it is possible to accurately measure the temperature change on the surface of the coating film 28 without being affected by the heat capacity of the optical component body. . Therefore, the state of the coating film 28 can be directly grasped, and strict performance evaluation of the coating film 28 can be performed. In addition, since the coating film 28 can be inspected as described above, the inspection result can be fed back to the coating process to improve the yield. In addition, since the temperature change of the coating film 28 is directly measured, there is no time delay due to the influence of the heat capacity of the prism 22, and a quick and accurate temperature measurement is possible. Therefore, the time required for the inspection is shortened, and the inspection accuracy is improved. Also,
By using the non-contact radiation thermometer 48, it is not necessary to use, for example, Teflon or an adhesive for bringing the temperature sensor into contact with the optical component, and the optical component is not contaminated. Further, if it is found that the coating film 28 is defective, it is easy to re-manufacture the optical component by performing only the coating process again. Therefore, it is necessary to re-melt the optical component and re-create the optical component, or discard the optical material. Absent.
Therefore, the cost for manufacturing the optical component is reduced, the labor is reduced, and the optical material is not wasted.

FIG. 7 shows an example of a configuration in which the coating films 28 of a large number of front mirrors 8 are inspected simultaneously. As shown in the figure, the inspection laser light 45 is divided into equal powers by the beam splitter 42, each of which is irradiated to a plurality of front mirrors 8, and the incident side of the front mirror 8 (the side facing the laser chamber 2). An inspection is performed by measuring the temperature of the partially reflective coating film 28 coated on the surface. The front mirror 8 is also coated with an anti-reflection coating film 28 on the emission side, and measures the temperature of the anti-reflection coating film 28 at the same time to perform the inspection. In this way, a plurality of optical components can be inspected at once,
Inspection time is reduced.

FIG. 8 shows an example in which temperature is measured using a thermocouple 37 in addition to the radiation thermometer 48. A thermocouple 37 is attached near the partial reflection coating film 28 coated on the beam splitter 12 to measure the temperature of the beam splitter 12. That is, by simultaneously measuring the heat absorption inside the beam splitter 12 due to a defective material or the like, the partial reflection coating film 28 is formed.
The effect of temperature changes due to other causes can be canceled.
Therefore, a temperature change due to a defect of the coating film 28 can be more accurately grasped, and the accuracy of the coating film inspection is improved.

Next, a second embodiment will be described. FIG. 9 is a configuration diagram of an inspection device according to the second embodiment. In the figure, in addition to the inspection device of the first embodiment, the inspection device includes a scattered light collector 38 that collects scattered light 35 irregularly reflected from the test object, and a photoelectric sensor 36 that detects the intensity of the scattered light 35. ing. When the inspection laser light 45 is made incident on the scattered light collector 38 whose inside is hollowed out from the entrance 52 penetrating from the outside, the inspection laser light 45 is provided through the outside on the opposite side of the entrance 52. Exit 5
The object to be inspected (the window 7 in the figure) attached to 3 is irradiated. The scattered light collector 38 is provided with a temperature measurement hole 54 penetrating from the outside. A radiation thermometer 48 is attached to the temperature measurement hole 54, and measures the temperature of the anti-reflection coating film 28 on the surface of the window 7 as in the first embodiment.

On the other hand, a part of the inspection laser light 45 is irregularly reflected by the non-reflective coating film 28 coated on the surface of the window 7 and becomes scattered light 35 scattered in various directions. The inner surface of the scattered light collector 38 is plated with a highly reflective material such as gold, or
It is coated with total reflection by a dielectric film. Therefore, the scattered light 35 is not absorbed and is repeatedly reflected for a long time, and finally most of the scattered light is collected in the sensor hole 55 provided inside the scattered light collector 38. A photoelectric sensor 36 that converts the power of incident light into a voltage is attached to the sensor hole 55.

The photoelectric sensor 36 includes an inspection controller 49
And the intensity of the scattered light 35 irregularly reflected by the non-reflective coating film 28 is measured. The inspection controller 49
The magnitude of the scattered light 35 is compared with a predetermined allowable value.
Is determined to be of poor quality. The scattered light collector 38
Is for improving the measurement accuracy by collecting more scattered light 35, and is not necessarily required. Instead, the photoelectric sensor 36 is arranged alone near the coating film 28 so that Is also good.

As described above, according to the present embodiment, in addition to the temperature distribution of the coating film 28 measured in the first embodiment,
The intensity of the scattered light 35 irregularly reflected on the surface is measured, and the intensity of the scattered light 35 is set as one of the evaluation conditions for the coating film 28. Thereby, in addition to the heat absorption of the coating film 28, the loss of the laser light due to the irregular reflection can be evaluated, so that it is possible to obtain the coating film 28 having a smaller loss and a higher performance. Therefore, the performance of the optical component is improved, and the reliability of the excimer laser 1 using such an optical component is improved.

In each of the embodiments described above, the inspection laser beam 45 is irradiated under conditions that are actually used inside the excimer laser 1, but the present invention is not limited to this. For example, focus the inspection laser light,
The object may be irradiated. Further, if the coating film 28 has a defect at an end portion of an optical component which is not normally irradiated with light, the coating film 28 may gradually come off while being irradiated with diffusely reflected light or the like due to long-time use. In order to detect a defect of the coating film 28 due to such a cause in advance, for example, an inspection laser beam 45 having an intensity distribution as shown in FIG. The coating film 28 may be inspected. Alternatively, the inspection laser light 45 may be spread by using the inspection optical system 44 as an expander, and the inspection may be performed by irradiating the inspection laser light 45 over the entire surface of the optical component. In this manner, by irradiating the entire surface of the optical component, a defect of the coating film 28 in a normally unused area can be detected, and the accuracy of the inspection is improved.

Although the excimer laser has been described,
The present invention is applicable to other ultraviolet laser devices in general, such as an F2 laser. Further, the present invention can be applied not only to lasers but also to general optical components that reflect and transmit ultraviolet light.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an excimer laser.

FIG. 2 is a configuration diagram of a coating film inspection apparatus according to the first embodiment.

FIG. 3 is an explanatory view showing a beam profile of a laser beam.

FIG. 4 is an explanatory diagram showing a distribution example of a temperature rise.

FIG. 5 is a graph showing a temperature rise of a coating film.

FIG. 6 is a configuration diagram of an inspection device when inspecting a prism.

FIG. 7 is a configuration example when a large number of optical components are inspected simultaneously.

FIG. 8 is a configuration diagram of an inspection device using a thermocouple together.

FIG. 9 is a configuration diagram of an inspection device according to a second embodiment.

FIG. 10 is a light absorption measuring device according to a conventional technique.

[Explanation of symbols]

1: excimer laser, 2: laser chamber, 7: window, 8: front mirror, 9: window, 11: laser beam, 12: beam splitter, 20: band narrowing unit, 22: prism, 23: grating, 24:
Total reflection mirror, 25: damper, 26: area, 28: non-reflective coating film, 30: wavelength measuring device, 33: monitor etalon, 34: interference fringe, 35: scattered light, 36: photoelectric sensor, 37: thermocouple, 38: scattered light collector, 39: mirror, 42: beam splitter, 43: inspection laser device,
44: inspection optical system, 45: inspection laser beam, 46: shutter, 48: radiation thermometer, 49: inspection controller, 5
0: inspection laser controller, 52: entrance, 53: exit, 54: temperature measurement hole, 55: sensor hole.

Continued on the front page F term (reference) 2G051 AA90 AB01 AB06 BA05 BA10 BC03 CA01 CA20 CB05 2G086 EE05 EE08 HH07

Claims (3)

[Claims] A coating film for an optical component for ultraviolet light (28)
Inspection light irradiator (43) that irradiates inspection light (45) to the coating film (28) of the optical component, and non-contact type thermometer that measures the temperature of the coating film (28) (Four
8) A coating film inspection apparatus, comprising: 2. The coating film inspection apparatus according to claim 1, further comprising a light intensity measuring device (36) for measuring the intensity of scattered light (35) irregularly reflected from the coating film (28). Film inspection equipment. 3. A coating film for an optical component for ultraviolet light.
In the inspection method for inspecting, the inspection light (45) is irradiated to the coating film (28) of the optical component,
An inspection method characterized by measuring the temperature of the coating film (28) in a non-contact manner and evaluating the coating film (28) based on the temperature change.