JP2012234081A - Illumination device and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device and an optical device that facilitate adjustment for obtaining high detection sensitivity regardless of the condition of a measurement object, and that can prevent generation of illumination light causing degradation in the detection sensitivity.SOLUTION: The illumination device includes: a plurality of LEDs as a light source configured to illuminate a given area 1; and a plurality of polarizers 12, 22, 32 having polarization directions 15, 25, 35, respectively, in different directions from one another, between the plurality of LEDs and the given area 1. The plurality of LEDs are configured in such a manner that the LEDs can be driven as divided into a plurality of LED groups 10, 20, 30 each comprising several to ten-odd LEDs, and that exiting light of each LED group passes only one corresponding polarizer.

Description

  The present invention relates to an illuminating device used in an optical device such as an optical microscope, an optical measuring instrument, and an image detecting device, and more particularly to an illuminating device using a light emitting diode (LED) as a light source and an optical device using the illuminating device. .

  An optical microscope that performs observation and measurement by enlarging the object to be measured and the part to be measured, an optical measuring instrument that inspects and measures the shape, dimensions, defects, etc. of the object to be measured using an optical system, an image observation device using a camera, etc. In the optical apparatus, an illuminating device for the object to be measured is extremely important for obtaining a clear image of the object to be measured.

  Conventional illumination devices include a method of irradiating a measurement object with illumination light from the same direction as the observation direction or the detection direction of scattered light, etc., or a direction oblique to the observation direction and detection direction. There is a method of irradiating an object to be measured with illumination light. In the latter case, a ring illumination device for irradiating illumination light from the periphery of the observation device disposed directly above the object to be measured is often used. Patent Document 1, Patent Document 2, Patent Document A specific example is shown in FIG. Such a ring illumination device is particularly effective when, for example, it is desired to detect a shadow of an edge portion or the like clearly in measurement of an object having many edge portions, convex portions, or concave portions.

  In recent years, light-emitting diodes (LEDs) have a small shape and low power consumption as a means of solving problems such as shape, power consumption, and heat generation when a conventional lamp light source such as a halogen lamp is used as the light source of an illumination device. It has been attracting attention for its features such as high-speed response and long life, and has begun to be used in various fields. Also in the ring illumination devices of Patent Documents 1, 2, and 3, LEDs are used.

  For example, in the ring illumination device of Patent Document 1, a plurality of LEDs are arranged concentrically, and individual LEDs are attached with their directions determined so that the light emission direction is directed to the object to be measured, or individual LEDs The light emitting direction is set parallel to the optical axis, a Fresnel lens is arranged in front of the light emitting direction, and the light is condensed on the object to be measured. In addition, multiple LEDs can be controlled to be turned on or off for each group by grouping them into concentric rows and circumferential fan-shaped areas. It can be adjusted.

  Moreover, in patent document 2, the lens array which has a condensing lens is arrange | positioned ahead of each LED, and illumination efficiency is improved.

  On the other hand, in an optical apparatus such as an optical microscope, an optical measuring machine, or an image observation apparatus, it is important to increase the detection sensitivity of a target object to be measured. For this reason, as described above, when it is not sufficient to select the illumination angle and light distribution method of the illuminating device, detection is performed using the difference due to the polarization of the scattered light or reflected light from the object to be measured. Is called. For example, in Patent Document 3, a polarizing element is provided on the exit side of the illumination device and on the incident side of a light receiving device on which scattered light or reflected light from a silicon wafer as an object to be measured is incident, and is generated from the light source of the illumination device. A method of improving detection sensitivity in appearance inspection by using a difference in polarization characteristics of reflected light and scattered light by blocking a specific direction of polarized light and irradiating the silicon wafer.

JP-A-10-54940 JP 2003-315678 A JP 2010-60415 A

  When the polarizing element is installed in the illumination device as in Patent Document 3, the detection sensitivity depends on the light incident surface of the object to be measured and the incident angle of the illumination light. For example, when p-polarized illumination light with a Brewster angle is incident on a uniform surface to be measured, no reflected light is generated. When there are scratches or protrusions on the incident surface, reflected light is generated even with respect to p-polarized illumination light. Therefore, detection sensitivity is generally highest when p-polarized illumination light is incident. Therefore, when the light incident surface of the object to be measured is not constant, in order to obtain high detection sensitivity, it is necessary to adjust the polarization component of the illumination light and the irradiation direction according to the light incident surface. When the type of the object to be measured and the installation angle of the object to be measured are not constant, such adjustment greatly increases the measurement man-hours.

  In the case of a ring illumination device, the irradiation area near the center axis of the ring is irradiated with light obliquely from the surrounding direction. Even if the oblique angle is set to the Brewster angle, the entire emitted light Is set to one polarization direction, only the irradiation light from a specific direction with respect to the set polarization direction satisfies the condition of the Brewster angle that minimizes the reflected light intensity as p-polarized light. . That is, in this case, the irradiation light from other directions increases the reflected light intensity, so that a bias-like light intensity is given, and conversely, the sensitivity is deteriorated.

  Therefore, the subject of the present invention is an illumination device that can be easily adjusted to obtain high detection sensitivity regardless of the state of the object to be measured, and can prevent generation of illumination light that causes deterioration in detection sensitivity. And an optical device using the illumination device.

  In order to achieve the above object, an illuminating device of the present invention is an illuminating device configured to illuminate a certain area, and includes a plurality of LEDs as a light source, and the plurality of LEDs and the certain area are There are a plurality of polarizers having at least two different polarization directions in between, and the plurality of LEDs are configured to be divided into a plurality of LED groups and driven, Each of the emitted lights is configured to pass through only one of the plurality of polarizers.

  Here, it is preferable that the plurality of LEDs and the plurality of polarizers are integrally held in one casing. In this case, the casing has a ring shape, and the certain region includes the predetermined area. The vicinity of the center axis of the ring shape is desirable.

  Further, the lighting device includes an optical system in which the plurality of LEDs are arranged substantially concentrically with respect to the central axis, and the emitted light from the plurality of LEDs is condensed in the certain region, The LEDs may be divided in the ring-shaped circumferential direction to constitute the plurality of LED groups, and the plurality of polarizers may be disposed on the respective emission sides of the LED groups.

  An optical device according to the present invention is arranged on the incident side of the above-described illumination device according to the present invention, a photodetector configured to receive light scattered or reflected from the certain region, and the photodetector And a shutter that opens and closes in synchronization with the driving of the LED group. In this case, a polarizer may be disposed on the incident side of the photodetector.

  Another optical device according to the present invention opens and closes in synchronization with the driving of the illumination device according to the present invention, a camera that captures an image of the certain area, and the LED group disposed on the incident side of the camera. And a shutter. In this case, a polarizer may be disposed on the incident side of the camera.

  In the illuminating device of the present invention, a plurality of LEDs are divided into a plurality of LED groups and driven, and light emitted from each LED group passes through different polarizers and is measured on an object to be measured disposed in the same irradiation region. Irradiated. Therefore, by selecting the LED group to be driven, it is possible to select the polarization state and the irradiation direction of the light irradiated to the object to be measured. Thereby, the adjustment of the irradiation direction and the polarization state can be performed by selecting the LED group to be driven from among a plurality of LED groups arranged in advance so as to have various emission directions and polarization states. Regardless of the state of the object, adjustment for obtaining high detection sensitivity can be easily performed. Further, by not driving other LEDs other than the selected LED group, it is possible to prevent the generation of illumination light that causes deterioration in detection sensitivity.

  In the optical device using the illumination device according to the present invention, the light scattered or reflected from the object to be measured is opened or closed in synchronization with the driving of the LED group on the incident side of the photodetector or the camera. A high detection sensitivity can be obtained by providing the shutter to be opened and setting the shutter to open only during the time when the illumination light from the LED group that provides a high detection sensitivity is incident. In this case, the sensitivity is further improved by arranging the polarizer on the incident side of the photodetector or the camera.

  As described above, according to the present invention, an illumination device that can be easily adjusted to obtain high detection sensitivity regardless of the state of the object to be measured and can prevent generation of illumination light that causes deterioration in detection sensitivity. And an optical device using the illumination device.

It is a typical block diagram of 1st Embodiment of the illuminating device of this invention. It is sectional drawing of the typical side surface of 2nd Embodiment of the illuminating device of this invention. It is a typical bottom view of 2nd Embodiment of the illuminating device of this invention. It is sectional drawing of the typical side surface of embodiment of the optical apparatus of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an illumination device and an optical device according to the present invention will be described in detail based on the drawings.

  FIG. 1 is a schematic configuration diagram of a first embodiment of a lighting device according to the present invention. In FIG. 1, the illuminating device of the present embodiment is an illuminating device configured to illuminate a certain area 1, and has a plurality of LEDs as a light source. , Three polarizers 12, 22, and 32 having different polarization directions 15, 25, and 35, respectively, and a plurality of LEDs each include three LED groups 10 each consisting of several to dozens of LEDs. , 20 and 30 so that the output light 14 of the LED group 10 can be driven only by the polarizer 12, the output light 24 of the LED group 20 can be driven only by the polarizer 22, and the LED group 30 can be driven. The outgoing light 34 is configured to pass only through the polarizer 32.

  Here, the drive circuits 11, 21, and 31 of the LED groups 10, 20, and 30 are connected to the output port of the switch 7, and the output of the power supply 8 is connected to the input port of the switch 7. By switching the switch 7, power is supplied to any one of the drive circuits 11, 21, and 31, and any one of the LED groups 10, 20, and 30 is driven to emit light. Each LED has a lens on the exit side to suppress the spread of light emission. Further, a focusing lens array or a Fresnel lens may be provided between each LED group and each polarizer, or on the exit side of each polarizer. Here, as the polarizers 12, 22, and 32, film-like or plate-like polarizers such as a polarizing film and polarizing glass can be used.

  In FIG. 1, the LED group 10, the drive circuit 11, and the polarizer 12 are in the housing 13, the LED group 20, the drive circuit 21, and the polarizer 22 are in the housing 23, and the LED group 30, the drive circuit 31, and the polarizer. Although 32 is respectively hold | maintained integrally with the housing | casing 33, these three housings | casings 13, 23, and 33 may be hold | maintained further integrally.

  In the illumination device of the present embodiment, the emitted lights 14, 24, and 34 from the three LED groups have different irradiation directions with respect to the object to be measured 6 placed in the fixed region 1, and They have different polarization states. For this reason, the detection sensitivity differs depending on the direction of the portion to be observed or detected of the DUT 6. For example, when the measurement surface is close to the Brewster angle with respect to the irradiation light and the polarization state of the irradiation light is close to the polarization direction where the reflection is small, other irradiation light is used for detection of protrusions and defects on the measurement surface. High sensitivity can be obtained. Therefore, observation or detection is facilitated by driving only the LED group capable of obtaining the high sensitivity. In this case, if there is illumination light from another LED group, it becomes a deterioration factor of detection sensitivity.

  In the case of this embodiment, switching of the switch 7 for selecting the LED group may be performed manually when a person performs observation or measurement, or is automatically scattered or reflected by a photodetector. When the detection is performed, it may be configured such that only high-sensitivity measurement data is captured by automatically switching with a control circuit or the like.

  Although FIG. 1 shows a case where there are three LED groups, more LED groups having different combinations of irradiation directions and polarization states may be provided, so that irradiation light with higher sensitivity can be selected. It becomes possible to do. The type of polarization state may be not only the difference in polarization direction in linearly polarized light but also the difference between linearly polarized light and circularly polarized light.

  FIG. 2 is a schematic cross-sectional side view of a second embodiment of a lighting device according to the present invention, and FIG. 3 is a schematic bottom view. 2 and 3, the illumination device according to the present embodiment is an illumination device configured to illuminate a certain region 70, and has a plurality of LEDs 3 as a light source. Between the region 70, there are eight polarizers 51, 52, 53, 54, 55, 56, 57, 58 having four kinds of polarization directions, and each of the plurality of LEDs is several to dozens. The LED group 41 is configured to be divided into eight LED groups 41, 42, 43, 44, 45, 46, 47, and 48, and the emitted light of the LED group 41 is only the polarizer 51. The emitted light from the LED group 42 is only the polarizer 52, the emitted light 53 from the LED group 43 is only the polarizer 53, the emitted light from the LED group 44 is only the polarizer 54, and the emitted light from the LED group 45 is the polarizer 55. Only the output light of the LED group 46 is a polarizer 56. Only the outgoing light of the LED group 47 is only polarizer 57, light emitted from the LED group 48 is only polarizer 58, are configured to respectively pass. In addition, the arrow in FIG. 3 has shown the polarization direction of each polarizer. Further, the object to be measured is arranged in a certain region 70.

  Here, the eight LED groups 41 to 48 including the plurality of LEDs 3 and the eight polarizers 51 to 58 are integrally held in one casing 40, and the casing 40 has a ring shape and has a certain region 70. Is a region in the vicinity of the ring-shaped central axis 50. Further, the plurality of LEDs 3 are arranged substantially concentrically with respect to the optical axis 50, and a Fresnel lens 60 is provided on the emission side of each LED group as an optical system for condensing the emitted light from the plurality of LEDs 3 in a certain region 70. Have. The plurality of LEDs 3 are divided in a ring-shaped circumferential direction to constitute a plurality of fan-shaped LED groups 41 to 48, and the plurality of polarizers 51 to 58 are arranged on the respective emission sides of the LED groups. Here, the Fresnel lens 60 may be a single integrated Fresnel lens having a ring shape, or may be separately divided for each LED group. Further, instead of the Fresnel lens 60, a condensing optical system including a prism and a lens array is used, and each LED group is inclined and installed so that the emission direction of each LED group faces a certain region 70. Is also possible.

  Also in the present embodiment, each LED group is provided with an independent drive circuit, and each drive circuit is configured to operate independently by a control circuit or the like. For example, as shown in FIG. 2, a drive circuit 73 is installed in the LED group 43, and a drive circuit 77 is installed in the LED group 47. Also in the present embodiment, as in the first embodiment, the switching of driving of each LED group may be performed manually when a person performs observation or measurement, or automatically by a photodetector. In the case of detecting scattered light or reflected light, it may be configured to automatically switch by a control circuit or the like so as to capture only high-sensitivity measurement data. Further, the driving of the LED groups may be configured to drive two or more LED groups at the same time according to the required sensitivity.

  In the present embodiment, each LED group and the polarizer are arranged by dividing the ring shape into eight in the circumferential direction of the ring shape. However, the number of divisions may be as small as two or three. There may be many divisions, 16 divisions and the like. Further, by combining a plurality of lighting devices of the present embodiment in the height direction, or by combining a plurality of lighting devices of the present embodiment having different diameters in the horizontal direction with respect to the same central axis, the illumination of the present invention. It is also possible to configure the device.

  FIG. 4 is a schematic side sectional view showing an embodiment of an optical device according to the present invention. 4, the optical device according to the present embodiment includes an illumination device 80 according to the second embodiment illustrated in FIGS. 2 and 3, a camera 81 that captures an image of a certain region 70, and a camera 81. And a shutter 82 that opens and closes in synchronization with the driving of the LED group disposed on the incident side. Further, a polarizer 83 having a specific polarization direction is disposed on the incident side of the camera 81. The driving circuit of each LED group and the shutter 82 are connected to the control circuit 84. An object to be observed to be observed is placed in a certain area 70.

  The operation of the optical device according to the present embodiment is performed by switching the LED group that is sequentially driven by controlling the shutter 82 to be opened only when one LED group emits light, and selecting the LED group that can obtain the best observation state. After the selection, control is performed so that the shutter is opened in synchronization with the driving of the selected LED group. Thereby, observation is always possible by irradiation with only good illumination light.

  It is also possible to configure an optical device that automatically detects scattered light and reflected light from the object to be measured by installing a photodetector instead of the camera 81. In this case, the LED group that is sequentially driven by the control circuit 84 is automatically switched to automatically select the LED group from which high-sensitivity measurement data can be obtained, and then synchronized with the driving of the selected LED group. Control the shutter to open. This makes it possible to measure with high sensitivity by always irradiating only good illumination light.

  Needless to say, the present invention is not limited to the illumination device and the optical device of the above-described embodiment, and the design can be changed according to the purpose and application. For example, the arrangement of each LED group and the polarizer can be arbitrarily determined according to the desired direction of the illumination light and the desired polarization state with respect to a certain region where the object to be measured is placed, and the plurality of LED groups and the polarizer are separately provided. It may be housed in a housing.

1, 70 Constant area 3 LED
6 Device to be measured 7 Switch 8 Power supply 10, 20, 30, 41, 42, 43, 44, 45, 46, 47, 48 LED groups 11, 21, 31, 73, 77 Drive circuit 12, 22, 32, 51, 52, 53, 54, 55, 56, 57, 58, 83 Polarizers 13, 23, 33, 40 Cases 15, 25, 35 Polarization direction 50 Central axis 80 Illumination device 81 Camera 82 Shutter 84 Control circuit

Claims (8)

  A lighting device configured to illuminate a certain area, and a plurality of LEDs as a light source, and a plurality of LEDs having at least two different polarization directions disposed between the plurality of LEDs and the certain area The plurality of LEDs are configured to be divided into a plurality of LED groups and can be driven, and light emitted from the plurality of LED groups is one of the plurality of polarizers, respectively. An illumination device configured to pass through only a polarizer.   The lighting device according to claim 1, wherein the plurality of LEDs and the plurality of polarizers are integrally held in one housing.   The lighting device according to claim 2, wherein the casing has a ring shape, and the certain region is in the vicinity of a central axis of the ring shape.   An optical system for condensing the light emitted from the plurality of LEDs in the fixed region, the plurality of LEDs being arranged substantially concentrically with respect to the optical axis, and divided in the circumferential direction of the ring shape The lighting device according to claim 3, wherein the plurality of LED groups are configured, and the plurality of polarizers are arranged on an emission side of each of the plurality of LED groups.   5. The illumination device according to claim 1, a photodetector configured to receive light scattered or reflected from the certain region, and an incident side of the photodetector An optical device comprising: a shutter that opens and closes in synchronization with driving of the LED groups arranged.   The optical device according to claim 5, wherein a polarizer is disposed on an incident side of the photodetector.   5. The illumination device according to claim 1, a camera that captures an image of the certain region, and a shutter that opens and closes in synchronization with driving of the LED group disposed on the incident side of the camera. And an optical device.   The optical device according to claim 7, wherein a polarizer is disposed on an incident side of the camera.

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