Extinction ratio measurement device

Abstract

A problem with measuring extinction ratio over a small range has been that it is time-consuming to measure the entire surface of a specimen.　The present invention provides an extinction ratio measurement device that can measure the extinction ratio over many small ranges at once, the extinction ratio measurement device comprising: a light source unit; a light beam distribution unit that splits light from the light source unit into a plurality of light-emitting optical fibers to create a plurality of light beams; an extinction ratio detection unit that detects the plurality of light beams from the light source unit that have passed through a specimen; and a photoelectric conversion unit that converts the plurality of light beams from the extinction ratio detection unit into electrical signals, wherein the extinction ratio detection unit is provided with: a light-emitting unit that includes a light beam emitting unit that collimates the plurality of light beams and emits the collimated rays in parallel, and a polarizer for aligning the polarizations of the light beams in one direction; a light-receiving unit that includes a detector adjusted to be in a crossed-Nicols relationship with the polarizer, and a light beam receiving unit that receives each of the light beams that has passed through the detector; and a specimen placement space where the specimen is placed between the light beam emitting unit and the detector.

Description

Extinction ratio measuring device

[0001] The present invention relates to an apparatus for measuring extinction ratios used in measuring the polarization properties of a substance.

[0002] Measurements using polarized light are used in many situations, such as measuring the performance of polarizers, analyzing the stress of glass or plastics, and analyzing the components of chemical substances. High-precision measurements are also required. For example, in the detection of crystal defects in semiconductor wafers described in Patent Document 1, light whose polarization has been uniformed by a polarizer is passed through the semiconductor wafer, and the transmitted light is observed by passing it through an analyzer to find crystal defects.

[0003] If the wafer has no defects, the light whose polarization direction has been aligned by the polarizer will pass through as is. The light that passes through the polarizer cannot pass through the analyzer, so it appears completely dark when viewed from the back of the analyzer. On the other hand, if the wafer has defects, the polarization direction of the light that passes through the wafer will be disturbed and it will be able to pass through the analyzer. In other words, by measuring the darkness of the light that has passed through the object under test when viewed through the analyzer, the defect state of the wafer can be discovered.

[0004] Furthermore, glass or plastic can be used as the object to be measured instead of a wafer. When stress is applied to these materials, the polarization characteristics of the transmitted light change at that point. Therefore, by observing the transmitted light through an analyzer, it is possible to observe how stress is applied.

[0005] According to these measurement principles, the accuracy of the measurement is determined by the extinction ratio, which is the amount of light that can be blocked by the analyzer after the polarization direction has been aligned by the polarizer.One way to improve the accuracy of extinction ratio measurements for an object under test is to reduce the size of the light spot that is irradiated onto the object under test.

[0006] However, if the measuring light spot is made small, in order to measure the entire object to be measured, the spot must be moved each time the measurement is performed, which takes a long time. As a method to overcome this problem, Patent Document 1 discloses a crystal defect detection device that uses a linearly arranged LED point light source, aligns the polarization with a polarizer, and observes the light that passes through the object to be measured through an analyzer with an imaging unit, thereby making it possible to observe defects over a wide field of view at once.

[0007] Japanese Patent Application Laid-Open No. 2022-020435

[0008] The method of Patent Document 1 can observe the extinction ratio over a wide range, but since it is not configured to pass parallel light from the light-emitting side to the light-receiving side, it does not measure the extinction ratio for each small spot, and does not have the precision to measure defects in each small area of ​​the object being measured.

[0009] The present invention has been conceived in view of the above problems, and provides a measuring device capable of measuring the extinction ratio in a minute region.

[0010] More specifically, the extinction ratio measuring device according to the present invention comprises a light source unit, a light beam distribution unit that divides light from the light source unit into a plurality of light emitting optical fibers to generate a plurality of light beams, an extinction ratio detection unit that detects the plurality of light beams from the light source unit that have passed through an object under test, and a photoelectric conversion unit that converts the plurality of light beams from the extinction ratio detection unit into electrical signals, wherein the extinction ratio detection unit comprises: a light beam emitting unit that converts the plurality of light beams into parallel rays and emits them in parallel; a light emitting unit having a polarizer that aligns the polarization of the light beams in one direction; an analyzer adjusted to a crossed Nicol relationship with the polarizer; a light receiving unit having a light beam receiving unit that receives each of the light beams that have passed through the analyzer; and an object under test placement space for placing the object under test between the light beam emitting unit and the analyzer.

[0011] The extinction ratio measuring device according to the present invention emits a plurality of light beams with uniform polarization and has a light beam unit that receives each of the light beams through an analyzer, so that the extinction ratio of each minute region having a light beam diameter can be measured.

[0012] Furthermore, by using laser light as the light source, providing afocal parallel light between the emitting light beam unit and the receiving light beam unit, and placing a focusing lens immediately before the receiving light beam unit, and receiving the light with an optical fiber, it becomes difficult to receive scattered light from adjacent light emitting units, thereby improving the measurement accuracy of each receiving unit.

[0013] 11 is a diagram showing the configuration of an extinction ratio measuring device. FIG. 12 is an enlarged view of a light-emitting unit and a light-receiving unit. FIG. 13 is a diagram showing an extreme example of non-uniformity in the polarization characteristics of a polarization element. FIG. 14 is a diagram explaining the adjustment of a polarizer and an analyzer. FIG. 15 is a diagram showing a state in which a polarizer is adjustable for each light beam and is adjusted so that the transmission axis differs for each light beam. FIG. 16 is a diagram showing an enlarged view of a light-receiving unit. FIG. 17 is a flow chart showing the measurement flow of an extinction ratio measuring device. FIG. 18 is a diagram showing another embodiment of a light-emitting unit. FIG. 19 is a diagram showing a part of an extinction ratio detecting section combining the light-emitting unit of FIG. 8 and the light-receiving unit of FIG. 9. FIG. 19 is a diagram showing the improvement in the average value of the lower measurement limit values ​​and the deviation of the lower measurement limit values ​​when 14 pairs of light beam light-emitting elements and light beam receiving elements are arranged in parallel, and the analyzer is configured with one polarizer and multiple analyzers, and the analyzer is adjusted to be in a crossed Nicol state with respect to the polarizer. FIG. 11 is a graph showing the improvement in the average value of the lower measurement limit values ​​and the deviation of the lower measurement limit values ​​of FIG. 11.

[0014] The extinction ratio measuring device according to the present invention will be described below with reference to drawings and examples. Note that the following description exemplifies one embodiment of the present invention and one example, and the present invention is not limited to the following description. The following description can be modified within the scope of the present invention. Furthermore, embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. Furthermore, all documents described in this specification are incorporated herein by reference. In this specification, when a numerical range is described as "A to B," this description means "greater than or equal to A (greater than A including A) or less than B (smaller than B including B)."

[0015] 1 shows the configuration of an extinction ratio measuring apparatus 1 according to the present invention. The extinction ratio measuring apparatus 1 has a light source section 10, a light beam distributor 20, a light-emitting unit 22, a light-receiving unit 26, a photoelectric conversion section 14, a control section 16, and an input / output display section 18. The light-emitting unit 22 and the light-receiving unit 26 form an extinction ratio detection section 12. Although not shown, the extinction ratio measuring apparatus 1 also has a power supply section that supplies power to each necessary section.

[0016] The extinction ratio measuring device 1 basically measures the light intensity by receiving polarized light emitted from the light-emitting unit 22 with the light-receiving unit 26. At this time, the light-receiving unit 26 measures the polarization of the light emitted from the light-emitting unit 22 through an analyzer 50 adjusted to a crossed Nicol configuration. Crossed Nicol configuration refers to a state in which the polarization transmission axes of two polarizers arranged on the optical path are perpendicular. Ideally, no light is observed at this time by the light-receiving unit 26. However, in reality, a small amount of light leaks, and the light-receiving unit 26 receives the light and detects it with the photoelectric conversion unit 14. The optical power at this time is defined as the lower measurement limit value Ib.

[0017] Next, when a half-wave plate is placed between the light-emitting unit 22 and the light-receiving unit 26, the polarization of the emitted light rotates by 90°, and the amount of light transmitted through the analyzer 50 becomes maximum. The optical power at this time is defined as the calibration value Ref.

[0018] Next, when the object under test M is placed between the light-emitting unit 22 and the light-receiving unit 26 instead of the half-wave plate, the polarization state is disturbed due to defects in the object under test M, etc. The light intensity measured by the light-receiving unit 26 at this time is taken as the extinction value Im. In other words, the extinction value Im is the intensity of the transmitted light when the object under test M is placed between the polarizer 40 and the analyzer 50, which are adjusted to a crossed Nicol relationship. The extinction value Im is a light intensity greater than the normal measurement lower limit value Ib. The ratio of the calibration value Ref to the extinction value Im is taken as the extinction ratio PER. The extinction ratio PER can be calculated using equation (1). The extinction ratio measuring device 1 is a device that calculates this extinction ratio PER.

[0019]

[0020] Here, PER is the extinction ratio, Ref is the calibration value, Im is the extinction value, and Ib is the lower limit of measurement. Note that Ref>>Ib holds true.

[0021] The light-emitting unit 22 is formed by a light beam emitter 30 and a polarizer 40. The combination of the light beam emitter 30 and the polarizer 40 that emits one light beam is called a light beam light-emitting element 32. In other words, the light-emitting unit 22 can be said to be a plurality of light beam light-emitting elements 32 arranged in parallel.

[0022] The light receiving unit 26 is made up of an analyzer 50 and a light beam receiving section 60. The combination of the analyzer 50 and the light beam receiving section 60 that receives one light beam is called a light beam receiving element 62. In other words, the light receiving unit 26 can be said to be a plurality of light beam receiving elements 62 arranged in parallel.

[0023] In addition, an object to be inspected space 24 for arranging an object to be inspected M is provided between the polarizer 40 and the analyzer 50. The components will be described in detail below. Also, please refer to FIG. 2, which is an enlarged view of the light emitting unit 22 and the light receiving unit 26.

[0024] <Light source unit 10> The light source unit 10 is composed of a laser light source. Any type of laser can be used as long as it can emit laser light. A semiconductor laser is suitable for reducing the bulk of the entire device. Laser light has excellent directivity and convergence, making it advantageous for forming a microbeam. As will be described later, the extinction ratio measuring device 1 according to the present invention uses multiple light beams, but it is also possible to prepare as many laser light sources as necessary for the required light beams.

[0025] <Light beam distribution unit 20> The light beam distribution unit 20 is composed of a coupler that distributes the laser light from the light source unit 10 to multiple optical fibers. If the light source unit 10 has one laser light source, the light beam distribution unit 20 is composed of a one-to-many coupler. If there are as many laser light sources as there are optical fibers, the light beam distribution unit 20 is composed of optical fibers only, or of as many one-to-one couplers as there are optical fibers. The laser light from the light source unit 10 is input into multiple optical fibers and sent to the light beam emission unit 30. The optical fibers from the light source unit 10 to the light beam emission unit 30 are called light-emitting optical fibers 34.

[0026] The laser light input to the light-emitting optical fiber 34 is called a light beam LB. A single-mode optical fiber can be suitably used as the light-emitting optical fiber 34 because it has low transmission loss and can form a minute light beam. Note that if the number of light source units 10 is the same as the number of light-emitting optical fibers 34, the light beam distributor 20 will include the light source units 10.

[0027] 2, the light beam emitter 30 is configured by arranging a plurality of light beam light emitting elements 32 in parallel, each of which is made up of an emission end 34a of a light-emitting optical fiber 34 and an emission-side collimator lens 36. Alternatively, a plurality of light-emitting optical fibers 34 may be arranged in parallel, and an emission-side lens array 36AR in which emission-side collimator lenses 36 are arrayed may be arranged in front of them (in the light beam emission direction). Each light beam light emitting element 32 converts a light beam LB (laser beam) emitted from the emission end 34a of the light-emitting optical fiber 34 into a parallel beam.

[0028] There is no limit to the number of light beam light emitting elements 32 arranged side by side, as long as there are multiple light beam light emitting elements 32. However, it is preferable to group together about 4, 8, or 16 light beam light emitting elements 32 into one light beam emitting unit 30. The position of the light beam light emitting element 32 may need to be finely adjusted so that the light beam LB can be suitably transmitted and received in a one-to-one relationship with the light beam receiving element 62 described below, and if many light beam light emitting elements 32 are grouped together in one light beam emitting unit 30, it will be difficult to make adjustments later.

[0029] It should be noted that a plurality of light beam emitters 30 each including a plurality of light beam light emitting elements 32 may be arranged in parallel. For example, two sets of light beam emitters 30 each including eight light beam light emitting elements 32 arranged in parallel may be arranged side by side.

[0030] <Polarizer 40> The polarizer 40 is a polarizing element PE that aligns the polarization direction of the parallel light beams emitted from the light beam emitter 30 in one direction. In other words, the polarizing element PE is a linear polarizing element. There are various types of polarizers 40, such as crystalline polarizing elements, but a glass polarizing element can be preferably used.

[0031] The polarizer 40 may be processed to the size of the light-emitting side lens array 36AR and placed in front of the light-emitting side lens array 36AR. In other words, one polarizer 40 can align the polarization directions of multiple light beams LB. Of course, one polarizer 40 may be provided for each light beam LB. In that case, each light beam light-emitting element 32 has a polarizer 40.

[0032] <Light-emitting unit 22> The light beam emitting section 30 and the polarizer 40 are collectively referred to as the light-emitting unit 22. The extinction ratio measuring device 1 may have a plurality of light-emitting units 22.

[0033] <Analyzer 50> The analyzer 50 is a polarizing element PE adjusted to a crossed Nicol state with respect to the polarization direction of the polarizer 40. Here, crossed Nicol means a state in which the polarization direction of the analyzer 50 is changed relative to the polarizer 40, and the amount of light passing through the analyzer 50 is minimized. In the case of an ideal polarizer 40 and analyzer 50, this state occurs when the polarization directions differ by 90°, but it can be said that the crossed Nicol state exists even if there is an unavoidable misalignment during the adjustment work.

[0034] The analyzer 50 is processed to the size of the light-receiving-side lens array 66AR of the light-beam receiving elements 62 constituting the light beam receiving unit 60, which will be described later, and is placed in front of the light-receiving-side lens array 66AR (between the object M and the light-receiving-side lens array 66AR). In other words, a plurality of light beams LB are blocked by one analyzer 50. Alternatively, an analyzer 50 may be provided for each light-beam receiving element 62.

[0035] <Light beam receiving unit 60> In the light beam receiving unit 60, light beam receiving elements 62 each composed of a light-receiving-side collimator lens 66 and an incident end 64a of a light-receiving optical fiber 64 are arranged at a position corresponding to each light beam LB. Note that a plurality of light-receiving optical fibers 64 may be arranged in parallel, and a light-receiving-side lens array 66AR in which light-receiving-side collimator lenses 66 are arrayed may be arranged behind them (in the opposite direction to the traveling direction of the light beam).

[0036] Each light-receiving-side collimator lens 66 converges the light beam LB (laser beam) that has passed through the analyzer 50 and is now parallel, and makes it incident on the incident end 64a of the light-receiving optical fiber 64. The light-receiving optical fiber 64 sends the light beam LB that has passed through the analyzer 50 to the photoelectric conversion unit 14. A multimode optical fiber can be suitably used for the light-receiving optical fiber 64.

[0037] <Light-receiving unit 26> The analyzer 50 and the light beam receiving section 60 are collectively referred to as the light-receiving unit 26. The extinction ratio measuring device 1 may have a plurality of light-receiving units 26. Note that the light-receiving unit 26 is composed of light beam receiving elements 62, the number of which is the same as the number of light beams LB emitted by the light-emitting unit 22.

[0038] <Photoelectric Conversion Unit 14 > The photoelectric conversion unit 14 converts the light transmitted from the light-receiving optical fibers 64 into an electrical signal. Then, the electrical signal for each light-receiving optical fiber 64 is transmitted to the control unit 16.

[0039] <Control unit 16> The control unit 16 can be configured with a CPU (Central Processor Unit) and memory. The control unit 16 sends instruction signals to the light source unit 10 to turn on / off the emission of laser light, to the photoelectric conversion unit 14 to send data, and to the input / output display unit 18 to display display data. The control unit 16 also receives instruction signals from the input / output display unit 18 from the user and received signals for photoelectric output data from the photoelectric conversion unit 14.

[0040] The control unit 16 can also calculate the ratio of the calibration value Ref obtained by inserting a half-wave plate during calibration to the extinction value Im when the test object M is placed in the test object placement space 24 described below as the extinction ratio PER according to equation (1), and transmit it to the input / output display unit 18 for display.

[0041] <Input / Output Display Unit 18> The input / output display unit 18 displays the measured extinction ratio PER and inputs various settings for measurement. The input / output display unit 18 can be configured with a display and a touch panel using transparent electrodes.

[0042] <Inspection object placement space 24> The space between the polarizer 40 and the analyzer 50 is called the inspection object placement space 24. It may also be called the space formed between the light emitting unit 22 and the light receiving unit 26. The inspection object placement space 24 is configured at a distance such that the light beam LB emitted from a specific light beam emitting element 32 of the light beam emitting section 30 can be received by the light beam receiving element 62 of the corresponding light beam receiving section 60, but an adjacent light beam LB is not received by the light beam receiving element 62.

[0043] <Extinction ratio detection section 12> The light emitting optical fiber 34, the light emitting unit 22, the object placement space 24, the light receiving unit 26, and the light receiving optical fiber 64 are collectively referred to as the extinction ratio detection section 12. It is preferable that the extinction ratio detection section 12 be able to block light so that other light does not enter when the light receiving unit 26 measures the light beam LB.

[0044] The light-emitting unit 22 and the light-receiving unit 26 are collectively referred to as an optical device for detecting extinction ratios. The optical device for detecting extinction ratios is sufficient if the polarizer 40 of the light-emitting unit 22 and the analyzer 50 of the light-receiving unit 26 are adjusted to a crossed Nicol relationship for each light beam LB. In other words, as long as the light-emitting unit 22 and the light-receiving unit 26 are a set, they do not actually need to be in a state where the light beam LB can pass through.

[0045] This is because, as long as the light-emitting unit 22 and the light-receiving unit 26 are adjusted to a crossed Nicol relationship for each light beam LB, the extinction ratio detecting section 12 of the extinction ratio measuring apparatus 1 according to the present invention can be formed simply by attaching them to predetermined positions. In other words, the optical device for extinction ratio detection can be sold as such.

[0046] <Polarizer 40 and Analyzer 50> The light beam LB, whose polarization direction is aligned in one direction by the polarizer 40, is ideally completely blocked by the analyzer 50, which is adjusted to a crossed Nicol configuration (adjusted so that the polarization direction is rotated 90 degrees and different). However, it is rare for the polarizing element PE to have uniform polarization characteristics over a wide area. Therefore, in reality, a small amount of the light beam LB passes through the analyzer 50 due to differences in polarization characteristics depending on the location on the polarizing element PE.

[0047] FIG. 3 shows an extreme example of the non-uniformity of the polarization characteristics of the polarizing element PE. The vertical line represents the transmission axis Tax. That is, light passes through the polarizing element PE from the front surface to the back surface of the paper. Here, the transmission axis Tax0 near the center of the polarizing element PE and the transmission axis Tax1 near the edge differ by an angle φ. Therefore, the polarization direction is different near the center and near the edge. However, even with such a polarizing element PE, the transmission axis Tax2 can be considered to be almost constant in the infinitesimal portion SA.

[0048] Therefore, at least one of the polarizer 40 and the analyzer 50 is configured to be able to be adjusted individually for each light beam LB.

[0049] That is, the light emitting unit 22 is configured with one polarizer 40, and the light beam receiving elements 62 are configured with analyzers 50 attached to each of the light beam receiving elements 62 so that they can be individually adjusted. Alternatively, conversely, the light beam emitting elements 32 are individually attached with polarizers 40 so that they can be individually adjusted, and the light receiving unit 26 is configured with only one analyzer 50.

[0050] By doing so, even if the polarization characteristics of the polarizing element PE itself are not constant depending on the location, the measurement lower limit value Ib can be adjusted to be small, and the extinction ratio PER can be increased for each light beam LB. In other words, even if the extinction value Im of the object M to be inspected is small, the extinction ratio PER can be calculated. In other words, the extinction ratio PER can be measured over a wide dynamic range.

[0051] Of course, each of the light-emitting unit 22 and the light-receiving unit 26 may be configured with a single polarizer 40 and analyzer 50. Also, each of the light-emitting unit 22 and the light-receiving unit 26 may be configured to have the same number of polarizers 40 and analyzers 50 as the number of light beams LB.

[0052] 4(i) shows the polarizer 40 and the light beam emitting element 32 as viewed from the inspection object placement space 24, and FIG. 4(ii) shows the analyzer 50 and the light beam receiving element 62 as viewed from the inspection object placement space 24. FIG. 4(a) shows the case where both the polarizer 40 and the analyzer 50 are formed from a single glass polarizing element.

[0053] 4(b), the polarizer 40 is formed from a single glass polarizing element PE, but the analyzer 50 uses a glass polarizing element PE that covers two light beam receiving elements 62, and the angle of each analyzer 50 is adjusted so that the measurement lower limit value Ib is lower. In other words, the transmission axis Tax50 of each analyzer 50 is adjusted to be in a crossed Nicol state with respect to the transmission axis Tax40 of the polarizer 40. Note that the angle adjustment may include adjustment of not only the rotation angle of the glass polarizing element PE in a plane perpendicular to the light beam LB but also the tilt angle with respect to the light beam LB.

[0054] In this way, when the light beam emitter 30 and light beam receiver 60 emit and receive a plurality of light beams LB and use a plurality of polarizers 40 or analyzers 50 to adjust the measurement lower limit Ib, this is referred to as "polarizers or analyzers that can be individually adjusted" or "individually adjustable." The number of individually adjustable polarization elements PE may be two or more and equal to or less than the number of light beam receivers 60 in one light-emitting unit 22.

[0055] Therefore, taking the light beam receiving element 62 as an example, an analyzer 50 that can be individually adjusted may be arranged for each individual light beam receiving element 62, or one individually adjustable analyzer 50 may be arranged for every two light beam receiving elements 62 as shown in Figure 4(b).

[0056] Furthermore, it is sufficient if multiple polarizers 40 or analyzers 50 are provided in one light-emitting unit 22 or light-receiving unit 26. If an individually adjustable polarization element PE is used in one of the light-emitting unit 22 or light-receiving unit 26, it is not necessary to use it in the other. In other words, it is sufficient if at least one of the polarizer 40 and the analyzer 50 can be individually adjusted. Figure 4 shows a case where the analyzer 50 side can be individually adjusted.

[0057] By individually adjusting the polarizer 40 or analyzer 50 for each light beam LB, the extinction ratio PER for each light beam LB can be measured in a leveled state. If the extinction ratio PER is measured with multiple light beams LB, the extinction ratio PER can be measured at multiple locations at once. However, when measuring the extinction ratio PER of the same region, the measured value cannot be trusted unless the measured values ​​of the extinction ratio PER for each light beam LB are leveled. As will be shown in the examples described later, it is preferable that the polarizer 40 or analyzer 50 be individually adjustable for each light beam LB.

[0058] 5 shows an example in which the polarizer 40 and analyzer 50 can be individually adjusted for each light beam emitting element 32 and light beam receiving element 62. Fig. 5(b) shows the arrangement of the polarizers 40 for each light beam emitting element 32, and Fig. 5(a) shows the transmission axis Tax indicated by an arrow. Fig. 5(c) shows the arrangement of the analyzers 50 for the light beam receiving element 62, and Fig. 5(d) shows the transmission axis Tax indicated by an arrow.

[0059] The transmission axis Tax of the polarizer 40 differs for each light beam LB, and the polarizer 40 and the analyzer 50 are adjusted to a crossed Nicol relationship. In this way, it is possible to measure changes for each incident polarization direction in a minute region of the inspection object M, and to obtain results that depend on the crystal orientation.

[0060] <Light beam receiving element 62> The light beam receiving element 62 is composed of the analyzer 50, an incident end 64a of a light-receiving optical fiber 64, and a light-receiving-side collimator lens 66. The incident end 64a of the light-receiving optical fiber 64 and the light-receiving-side collimator lens 66 constitute the light beam receiving unit 60. The advantages of using the light-receiving optical fiber 64 and the light-receiving-side collimator lens 66 will now be described. Figure 6 shows the object under test M, the analyzer 50, the light-receiving-side collimator lens 66, the light-receiving optical fiber 64, and its incident end 64a. Here, the case where scattered light R is generated in an optically heterogeneous region D of the object under test M and passes through the analyzer 50 is shown.

[0061] Suppose that scattered light R cannot be received by a given light beam receiving unit 60α and instead enters the light receiving-side collimator lens 66β of the adjacent light beam receiving unit 60β. However, if the scattered light R incident on the light receiving-side collimator lens 66β is incident at an angle greater than the NA of the light receiving optical fiber 64β, it cannot be guided through the light receiving optical fiber 64β. In this way, when the light beam receiving element 62 is configured with the light receiving-side collimator lens 66 and the light receiving optical fiber 64, scattered light R from the adjacent light beam LB is not guided. As a result, it is possible to accurately capture extremely small optical power from a minute region irradiated with the light beam LB without being affected by scattered light R from the object M to be inspected.

[0062] <Measurement Flow> Next, the operation of the extinction ratio measurement apparatus 1 will be described. Fig. 7 shows the measurement flow of the control unit 16. Referring to Fig. 7, when measurement is started by the extinction ratio measurement apparatus 1 (step S100), an end determination is made (step S102). If the measurement is to be ended (Y branch of step S102), the extinction ratio measurement apparatus 1 is stopped (step S104). If the measurement is to be continued (N branch of step S102), the processing flow proceeds to the next step.

[0063] Next, the calibration value Ref is measured (step S106). Specifically, it is confirmed that a half-wave plate adjusted to maximize the light receiving power at the light receiving unit 26 is placed in the inspection object placement space 24 (N branch of step S106). Once this is confirmed (Y branch of step S106), the process proceeds to the next step.

[0064] Next, the control unit 16 confirms that the extinction ratio detection unit 12 is shielded from the outside (step S108). This confirmation may be made by opening or closing a door that can access the extinction ratio detection unit 12, or by detecting a light intensity sensor disposed near the light receiving unit 26. If this is confirmed (Y branch in step S108), the process proceeds to the next step.

[0065] Next, the light beam LB is measured as the calibration value Ref (step S110). Specifically, the light beam LB is emitted from the light emitting unit 22, and each light beam LB is received by the light receiving unit 26. Since a half-wave plate is disposed in the inspection object placement space 24, the polarized light aligned in one direction by the polarizer 40 passes through the analyzer 50.

[0066] The received light is converted into an electrical signal by the photoelectric conversion unit 14, and then digitized by an AD converter or the like. That is, the light intensity is measured for each light beam LB and obtained as a numerical value. These measured values ​​are recorded in the memory of the control unit 16 as the calibration value Ref of each light beam LB. At this time, a message such as "Calibration value recording completed" may be displayed on the input / output display unit 18.

[0067] Next, the process waits for the object M to be placed in the object placement space 24 (N branch of step S112). At this time, a message prompting the user to place the object M in the object placement space 24 may be displayed on the input / output display unit 18.

[0068] When the object under test M is placed in the object under test placement space 24 (Y branch of step S112), it is confirmed again that the extinction ratio detection unit 12 is shielded (N branch of step S114).

[0069] When the extinction ratio detector 12 is shielded (Y branch in step S114), the light beam LB is measured again to obtain the extinction value Im (step S116).

[0070] Next, the extinction ratio PER is calculated (step S118). The extinction ratio PER can be found using equation (1). The calculated extinction ratio PER is displayed on the input / output display unit 18, and the process returns to the end determination step (step S102). In this manner, the extinction ratio PER can be measured.

[0071] 8 shows a first modification of the light-emitting unit 22. The light-emitting unit 22 is composed of two light beam emitting elements 32, a beam splitter 80, a total reflection mirror 82, and a polarizer 40. The parallel light beam LB emitted from the light beam emitting elements 32 is １ is the component L B reflected on the surface of the beam splitter 80 ３ The component LB that is refracted and transmitted through the beam splitter 80 is ２ The transmitted component LB ２ The reflected component LB passes through the polarizer 40 and its polarization direction is aligned. ３ is totally reflected by the total reflection mirror 82 and strikes the surface of the beam splitter 80 again.３ and the component LB transmitted through the beam splitter 80 ２ It is divided into:

[0072] In this way, the parallel light beam LB emitted from one light beam emitting element 32 １ A plurality of light beams LB can be generated by splitting the light beam into a plurality of beams using a beam splitter 80 and a total reflection mirror 82. With this configuration, a large number of light beams LB can be generated using a small number of light beam emitting elements 32, and the cost of the extinction ratio measuring device 1 itself can be reduced.

[0073] Furthermore, since the light beam light emitting elements 32 have a predetermined width 32w, it is not possible to generate adjacent light beams LB with a width narrower than when the light beam light emitting elements 32 are closely attached. However, with this configuration, by adjusting the distance between the beam splitter 80 and the total reflection mirror 82 and the angle θ between the light beams LB from the light beam light emitting elements 32, the width W between the light beam light emitting elements 32 can be adjusted. ３２ Narrower spacing W ＬＢ A light beam LB can be generated by

[0074] (Variation 2) Fig. 9 shows a variation of the light receiving unit 26. The light beam receiving elements 62 of the light receiving unit 26 also have a physical size, and even if the light beam receiving elements 62 are closely attached to each other, there are cases where they cannot receive the light beams LB from the light emitting unit 22 at the intervals between them. As shown in Fig. 9, the direction of the light beam LB that has passed through the analyzer 50 is changed by a total reflection prism 84, and the intervals W between the light beams LB are adjusted by an optical path changing unit 86 that combines a rhomboid prism, a Dove prism, or the like. ＬＢ The spacing width W ６２ The beam is spread to a wavelength of 1000 nm, and can be received by the light beam receiving element 62. The initial total reflection prism 84 may be omitted.

[0075] 10 shows a configuration in which the light-emitting unit 22 of Modification 1 and the light-receiving unit 26 of Modification 2 are combined. It can be said that this shows a part of the extinction ratio detection unit 12 (the light beam distribution unit 20 is omitted). The light-receiving unit 26 is composed of two light-receiving units, a light-receiving unit 26a and a light-receiving unit 26b. This allows for a narrow light beam interval W without being limited by the physical size of the light-emitting unit 22 and the light-receiving unit 26. ＬＢ That is, the extinction ratio PER in a narrow area can be measured.

[0076] Example 1 A light emitting unit 22 and a light receiving unit 26 were configured by combining 14 pairs of light beam emitting elements 32 and light beam receiving elements 62. Furthermore, adjustments were made so that the light beam LB from each light beam emitting element 32 could be received by the corresponding light beam receiving element 62. The light beam emitting elements 32 and light beam receiving elements 62 associated in this manner are called channels. Therefore, in this example, optical paths for 14 channels of light beam LB were configured. The channels were arranged in parallel with a distance of 2 mm between them.

[0077] The analyzer 50 on the light-receiving unit 26 side was one for 14 light beam receiving elements 62, and the number of polarizers 40 on the light-emitting unit 22 side was changed to examine the lower measurement limit value Ib. In this case, nothing was placed in the inspection object placement space 24 formed between the light-emitting unit 22 and the light-receiving unit 26. In other words, it can be said that the extinction ratio of air was measured. The polarizer 40 was adjusted so that it was in a crossed Nicol position with respect to the analyzer 50 for each group of shared light beam emitting elements 32.

[0078] The results are shown in Fig. 11. Fig. 11(a) shows the state of the light beam emitting unit 30 as viewed from the inspection object placement space 24 when the polarizer 40 is divided into two, Fig. 11(b) shows the state of the polarizer 40 when divided into seven, and Fig. 11(c) shows the state of the polarizer 40 when divided into 14. Each figure shows that the polarizer 40 is divided into 14 channels.

[0079] Due to the non-uniformity of the measurement lower limit transmission axis Tax, the average measurement lower limit for each channel was not the same. The right side of each figure shows the improvement in the average measurement lower limit Ib for the 14 channels and the deviation of the measurement lower limit.

[0080] The improvement in the average value of the measurement lower limit value Ib for 14 channels was determined by taking the average value of the measurement lower limit value Ib (average value of 14 channels) when the polarizer 40 in Figure 11 (a) is divided into two as 0 dB, and using this as the improvement from the value when it is divided into two (the decrease amount, since it is the measurement lower limit value Ib).

[0081] The more negative this improvement is, the lower the measurement limit Ib becomes, which is preferable. If the improvement in the measurement limit Ib is large, the difference between the calibration values ​​Ref in each channel is small, and a high extinction ratio PER can be measured.

[0082] When divided into two (0 dB improvement), the deviation of the measurement lower limit value Ib between each channel was 2.58. When divided into seven, the average value of the measurement lower limit value Ib decreased by 2.4 dB (improvement), and the deviation at that time was 1.87. When divided into 14 further, the average value of the measurement lower limit value Ib decreased by 4.3 dB (improvement), and the deviation at that time was 0.73.

[0083] This is shown in a graph in Figure 12. Referring to Figure 12, the horizontal axis indicates the number of divisions of the polarizer 40 for the 14 channels, and the left vertical axis indicates the average value (dB) of the measurement lower limit value. The right vertical axis indicates the deviation of the measurement lower limit value (unitless). By making the number of divisions of the polarizer 40 the same as the number of light beam emitters 30 and adjusting each light beam emitter 30 to be in a cross-Nicol state with the analyzer 50, the average value and deviation of the measurement lower limit value Ib for the 14 channels became smaller.

[0084] In this way, even if a large number of light beam emitters 32 and light beam receivers 62 are arranged in parallel at intervals of 2 mm, an extinction ratio measuring device can be constructed that can achieve a high extinction ratio PER and that also averages out measurement variations between channels.

[0085] The extinction ratio measuring device according to the present invention can be suitably used when measuring the extinction ratio of a substance.

[0086] 1 Extinction ratio measuring device 10 Light source unit 12 Extinction ratio detection unit 14 Photoelectric conversion unit 16 Control unit 18 Input / output display unit 20 Light beam distribution unit 22 Light emitting unit 24 Inspection object placement space 26 Light receiving unit 30 Light beam emitting unit 32 Light beam emitting element 34 Light emitting optical fiber 34a (of light emitting optical fiber) Emission end 32w (of light emitting optical fiber) Width 36 Light emitting side collimator lens 36AR Light emitting side lens array 40 Polarizer 50 Analyzer 60 Light beam receiving unit 62 Light beam receiving element 64 Light receiving optical fiber 64a (of light receiving optical fiber) Incident end 66 Light receiving side collimator lens 66AR Light receiving side lens array 80 Beam splitter 82 Total reflection mirror 84 Total reflection prism 86 Optical path changing section Ib Measurement lower limit value Ref Calibration value M Inspected object Im Extinction value PER Extinction ratio LB Light beam PE Polarizing element Tax Transmission axis SA Minute area R Scattered light

Claims

1. An extinction ratio measuring device comprising: a light source section; a light beam distributor section that divides light from said light source section into a plurality of light-emitting optical fibers to generate a plurality of light beams; an extinction ratio detector section that detects the plurality of light beams from said light source section that have passed through an object under test; and a photoelectric converter section that converts the plurality of light beams from said extinction ratio detector section into electrical signals, wherein said extinction ratio detector section comprises: a light beam emitter section that collimates the plurality of light beams and emits them in parallel; a light emitting unit having a polarizer that aligns the polarization of the light beams in one direction; an analyzer adjusted to a crossed Nicol relationship with said polarizer; and a light receiving unit having a light beam receiver section that receives each of the light beams that have passed through the analyzer; and an object under test placement space provided for placing said object under test between said light beam emitter section and said analyzer.

2. The extinction ratio measuring device according to claim 1, wherein said light beam receiving unit has a light beam receiving element corresponding to each of said plurality of light beams, and said light beam receiving element has a receiving-side collimator lens that focuses said light beams, and a receiving optical fiber having an incident end into which the light focused by said receiving-side collimator lens is incident.

3. An extinction ratio measuring device according to claim 1, wherein the polarizer has a different transmission axis for each of the light beams.

4. An extinction ratio measuring device according to claim 1, wherein either said polarizer or said analyzer is configured to be individually adjustable for each of said light beams.

5. An extinction ratio measuring device according to any one of claims 1 to 4, wherein the light beam emitting unit has a light beam light emitting element corresponding to the light beam, and the light beam light emitting element has the light emitting optical fiber and a light emitting side collimator lens that converts the light emitted from the emission end of the light emitting optical fiber into a parallel beam.

6. An extinction ratio measuring device according to any one of claims 1 to 4, wherein the light beam emitting unit comprises: the light emitting optical fiber; a light emitting side collimator lens that converts the light emitted from the output end of the light emitting optical fiber into parallel rays; a beam splitter that transmits part of the light from the light emitting side collimator lens and reflects part of it; and a total reflection mirror that totally reflects the light reflected by the beam splitter and irradiates it back onto the beam splitter.

7. An optical device for detecting extinction ratios, comprising a pair of a light emitting unit having a light beam emitting section that converts input light beams into parallel rays and emits them in parallel, and a polarizer that aligns the polarization of the light beams in one direction, and a light receiving unit having an analyzer adjusted to a crossed Nicol relationship with the polarizer and a light beam receiving section that receives each of the light beams that pass through the analyzer.

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