Extinction ratio measuring 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

Technical Field

[0001] The present invention relates to an apparatus for measuring an extinction ratio used when measuring the polarization characteristics of a substance.

Background Art

[0002] Measurements using the polarization of light are used in many aspects such as measuring the performance of polarizers, stress analysis of glass and plastics, and component analysis of chemical substances. Also, high-precision measurements may be required. For example, in detecting crystal defects in a semiconductor wafer of Patent Document 1, light whose polarization is made uniform by a polarizer is passed through the semiconductor wafer, and the passed light is observed by passing it through an analyzer to find crystal defects.

[0003] If there are no defects in the wafer, the light whose polarization direction is made uniform by the polarizer passes through as it is. Since the light that has passed through the polarizer cannot pass through the analyzer, it appears completely dark when viewed from the back side of the analyzer. On the other hand, if there are defects in the wafer, the polarization direction of the light that has passed through the wafer is disturbed and can pass through the analyzer. That is, by measuring the darkness of the light when the light that has passed through the object to be measured is viewed through the analyzer, the defect state of the wafer can be found.

[0004] Also, instead of the wafer, glass or plastic can be used as the object to be measured. When stress is applied to these substances, the polarization characteristics of the transmitted light change in that part. Therefore, by observing the transmitted light through the analyzer, the way the stress is applied can be observed.

[0005] According to these measurement principles, the extinction ratio, which indicates how much the light whose polarization direction is made uniform by the polarizer can be blocked by the analyzer, determines the accuracy of the measurement. As a method for improving the accuracy of the extinction ratio measurement for the object to be measured, it is conceivable to reduce the spot of the light irradiated on the object to be measured.

[0006] However, if the spot of light used for measurement is made small, measuring the entire object to be measured requires moving the spot repeatedly, which takes time. To overcome this problem, Patent Document 1 discloses a crystal defect detection device that uses a point light source of LEDs arranged in a line, aligns the polarization with a polarizer, and observes the light that has passed through the object to be measured through an analyzer in an imaging unit, thereby enabling the observation of defects over a wide field of view at once. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-020435 [Overview of the project] [Problems that the invention aims to solve]

[0008] While the method described in Patent Document 1 allows observation of extinction ratios over a wide range, it does not involve passing parallel light from the light-emitting side to the light-receiving side. Therefore, it does not measure the extinction ratio for each small spot, and does not have the accuracy to measure defects in minute areas of the object being measured. [Means for solving the problem]

[0009] This invention was conceived in view of the above-mentioned problems, and provides a measuring device capable of measuring the extinction ratio in a minute area.

[0010] More specifically, the extinction ratio measuring device according to the present invention is: Light source section, The light from the aforementioned light source is split into multiple light-emitting optical fibers to form multiple light beams. The light beam distribution section, An extinction ratio detection unit that detects the plurality of light beams from the light source unit that have passed through the object to be inspected, The unit includes a photoelectric conversion unit that converts the plurality of light beams from the extinction ratio detection unit into electrical signals. The extinction ratio detection unit is, A light beam emitting unit that makes the plurality of light beams parallel and emits them in parallel, having a polarizer that aligns the polarization of the light beam in one direction Then, linearly polarized light is shone onto the object to be inspected. to form a light emitting unit, an analyzer adjusted to the relationship between the polarizer and crossed nicols , the light beam that has passed through the object to be inspected passes through to form an analyzer unit, death, The aforementioned light beam receiving unit has a light beam receiving element corresponding to each of the plurality of light beams, The aforementioned light beam receiving element is A light-receiving collimator lens that focuses the aforementioned light beam, The optical fiber for receiving light has an input end into which light focused by the light-receiving collimator lens is received. to form a light receiving unit, and a test object placement space provided between the light beam emitting unit and the analyzer for placing the test object characterized in that.

Advantages of the Invention

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

[0012] Also, by using laser light as the light to be used, making the space between the light beam emitting unit that emits the light and the light beam receiving unit that receives the light an afocal parallel light, arranging a condenser lens immediately before the light beam receiving unit, and receiving the light with an optical fiber, it is possible to make it difficult to receive scattered light from adjacent light emitting units and improve the measurement accuracy of each light receiving unit.

Brief Description of the Drawings

[0013] [Figure 1] It is a diagram showing the configuration of an extinction ratio measuring device. [Figure 2] It is an enlarged view of the light emitting unit and the light receiving unit. [Figure 3]This is a figure that extremely shows an example of the non-uniformity of the polarization characteristics of a polarizing element. [Figure 4] This is a figure explaining the adjustment state of a polarizer and an analyzer. [Figure 5] This is a figure showing that a polarizer is adjustable for each light beam and is adjusted so that the transmission axes are different for each light beam. [Figure 6] This is a figure showing an enlarged view of a light receiving unit. [Figure 7] This is a flowchart showing the measurement flow of an extinction ratio measuring device. [Figure 8] This is a figure showing another embodiment of a light emitting unit. [Figure 9] This is a figure showing another embodiment of a light receiving unit. [Figure 10] This is a figure showing a part of an extinction ratio detection unit combining the light emitting unit of FIG. 8 and the light receiving unit of FIG. 9. [Figure 11] This is a figure showing the improvement amount of the average value of the measurement lower limit value and the deviation of the measurement lower limit value when 14 pairs of light beam emitting elements and light beam receiving elements are arranged in parallel, the polarizer is composed of one sheet, the analyzer is composed of a plurality of sheets, and the analyzer is adjusted to be cross-nicol with respect to the polarizer. [Figure 12] This is a graph showing the improvement amount of the average value of the measurement lower limit value and the deviation of the measurement lower limit value of FIG. 11.

Embodiments for Carrying Out the Invention

[0014] The extinction ratio measuring device according to the present invention will be described below with reference to drawings and examples. The following description illustrates one embodiment and one example, and the present invention is not limited to the following description. The following description may be modified without departing from the spirit of the present invention. 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 references cited herein are incorporated herein by reference. In this specification, when a numerical range is described as "A to B", it is intended to mean "A or greater (including A and greater than A) to B or less (including B and less than B)".

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

[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. In this case, the light-receiving unit 26 measures the light intensity by passing it through an analyzer 50 that is adjusted to crossed nicols with respect to the polarization of the light emitted from the light-emitting unit 22. Crossed nicols refer to a state in which the polarization transmission axes of two polarizers placed in the optical path are perpendicular. Ideally, no light should be observed in the light-receiving unit 26 at this time. However, in reality, a small amount of light leaks out, and the light-receiving unit 26 receives this light, which is detected by the photoelectric conversion unit 14. The light power at this time is defined as the lower limit of measurement 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 transmitted light to the analyzer 50 becomes maximum. The optical power at this time is defined as the calibration value Ref.

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

[0019]

number

[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.

[0021] The light-emitting unit 22 is formed from a light beam emitting section 30 and a polarizer 40. Furthermore, the combination of the light beam emitting section 30 and the polarizer 40 that emit a single light beam is called a light beam light-emitting element 32. In other words, the light-emitting unit 22 can be described as having multiple light beam light-emitting elements 32 arranged in parallel.

[0022] The light-receiving unit 26 is formed from an analyzer 50 and a light beam receiving section 60. The combination of the light beam receiving section 60 that receives a single light beam and the analyzer 50 is called a light beam receiving element 62. In other words, the light-receiving unit 26 can be said to be a configuration in which multiple light beam receiving elements 62 are arranged in parallel.

[0023] Furthermore, a space 24 for placing the object to be inspected M is provided between the polarizer 40 and the analyzer 50. The components are described in detail below. Please also refer to Figure 2, which is an enlarged view of the light-emitting unit 22 and the light-receiving unit 26.

[0024] <Light source part 10> The light source unit 10 is composed of a laser light source. Any type of laser is acceptable as long as it can emit laser light. Semiconductor lasers are preferable when reducing the overall size of the device. Laser light has excellent directivity and focusing properties, making it advantageous when forming a minute beam. 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 enough laser light sources to produce the required number of light beams.

[0025] <Optical beam distribution unit 20> The optical beam distribution unit 20 consists of couplers that distribute 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 optical beam distribution unit 20 consists of one-to-many couplers. If there are multiple laser light sources, the optical beam distribution unit 20 consists of only optical fibers, or one-to-one couplers for each optical fiber. The laser light from the light source unit 10 is input to multiple optical fibers and sent to the optical beam emission unit 30. The optical fibers from the light source unit 10 to the optical 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 the optical beam LB. A single-mode optical fiber is preferably used for the light-emitting optical fiber 34 because it has low transmission loss and can form a minute optical beam. If there are the same number of light source units 10 as light-emitting optical fibers 34, the optical beam distribution unit 20 will include the light source units 10.

[0027] <Light beam emitting section 30> Referring also to Figure 2, the light beam emission unit 30 is configured by arranging multiple light beam light-emitting elements 32 in parallel, each of which is composed of an output end 34a of a light-emitting optical fiber 34 and a light-emitting collimator lens 36. Alternatively, multiple light-emitting optical fibers 34 may be arranged in parallel, and a light-emitting lens array 36AR, which is an array of light-emitting collimator lenses 36, may be placed in front of them (in the direction of light beam emission). Each light beam light-emitting element 32 converts the light beam LB (laser beam) emitted from the output 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 that can be placed side by side, as long as there are multiple elements. However, it is preferable to group together about 4, 8, or 16 elements to form a single light beam emitting section 30. This is because the position of the light beam light-emitting elements 32 may need to be finely adjusted to ensure a suitable one-to-one relationship between them and the light beam receiving elements 62, which will be described later. If many light beam light-emitting elements 32 are grouped together in a single light beam emitting section 30, it becomes difficult to make these adjustments later.

[0029] Furthermore, multiple light beam emitting units 30, which are composed of multiple light beam emitting elements 32, may be arranged in parallel. For example, two sets of light beam emitting units 30, each with eight light beam emitting elements 32 arranged in parallel, may be placed side by side.

[0030] <Polarizer 40> The polarizer 40 is a polarizing element PE that aligns the polarization direction of parallel light rays emitted from the light beam emission unit 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 is preferably used.

[0031] The polarizer 40 can also be a single polarizer 40, machined to the size of the light-emitting lens array 36AR, and placed in front of the light-emitting lens array 36AR. That is, one polarizer 40 can be used to align the polarization direction 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 will have its own polarizer 40.

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

[0033] <Detector 50> The analyzer 50 is a polarizing element PE that is adjusted to crossed nicols with the polarization direction of the polarizer 40. Here, crossed nicols refers to the state in which the polarization direction of the analyzer 50 is changed relative to the polarizer 40 so that the least amount of light passes through the analyzer 50. In the case of an ideal polarizer 40 and analyzer 50, this state is achieved when the polarization directions differ by 90°, but even if there is an unavoidable deviation during the adjustment process, it can still be said that the state is crossed nicols.

[0034] The analyzer 50 is a single analyzer, machined to the size of the light-receiving lens array 66AR of the light beam receiving element 62 that constitutes the light beam receiving unit 60 described later, and placed in front of the light-receiving lens array 66AR (between the object under inspection M and the light-receiving lens array 66AR). In other words, multiple light beams LB are shielded by a single analyzer 50. Alternatively, an analyzer 50 may be provided on each of the light beam receiving elements 62.

[0035] <Optical beam receiving unit 60> The optical beam receiving unit 60 has an optical beam receiving element 62, which is composed of a receiving collimator lens 66 and the incident end 64a of a receiving optical fiber 64, positioned at a location corresponding to each optical beam LB. Alternatively, multiple receiving optical fibers 64 may be arranged in parallel, and an array of receiving collimator lenses 66, known as a receiving lens array 66AR, may be placed behind them (in the opposite direction to the direction in which the optical beam travels).

[0036] Each light-receiving collimator lens 66 focuses the parallel light beam LB (laser beam) that has passed through the analyzer 50 and directs it into the input 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 preferably be used as the light-receiving optical fiber 64.

[0037] <Light receiving unit 26> The analyzer 50 and the light beam receiving unit 60 are collectively referred to as the light receiving unit 26. The extinction ratio measuring device 1 may have multiple light receiving units 26. The light receiving unit 26 is composed of the same number of light beam receiving elements 62 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 fiber 64 into an electrical signal. It then sends the electrical signal for each light-receiving optical fiber 64 to the control unit 16.

[0039] <Control Unit 16> The control unit 16 can consist of a CPU (Central Processor Unit) and memory. The control unit 16 sends instruction signals to the light source unit 10 to turn the laser light emission ON / OFF, to the photoelectric conversion unit 14 to transmit data, and to the input / output display unit 18 to display the display data. It also receives instruction signals from the user in the input / output display unit 18 and reception signals for photoelectric output data from the photoelectric conversion unit 14.

[0040] Furthermore, the control unit 16 can calculate the extinction ratio PER as shown in equation (1), which is the ratio of the calibration value Ref obtained by inserting a half-wave plate during calibration to the extinction value Im when the object under inspection M is placed in the object under inspection placement space 24 described later, 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 provides input for various settings for measurement. The input / output display unit 18 can be composed of a display and a touch panel with transparent electrodes.

[0042] <Space for placing objects under inspection 24> The space between the polarizer 40 and the analyzer 50 is called the space under inspection 24. It can also be described as the space formed between the light-emitting unit 22 and the light-receiving unit 26. The space under inspection 24 is configured such that a light beam LB emitted from a specific light beam light-emitting element 32 of the light beam emitting unit 30 can be received by the corresponding light beam light-receiving element 62 of the light beam light-receiving unit 60, while adjacent light beams LB are not received by the light beam light-receiving elements 62.

[0043] <Extinction ratio detection unit 12> The light-emitting optical fiber 34, the light-emitting unit 22, the space for placing the object under inspection 24, the light-receiving unit 26, and the light-receiving optical fiber 64 are collectively referred to as the extinction ratio detection unit 12. It is preferable that the extinction ratio detection unit 12 be able to shield light so that other light does not enter when the light beam LB is measured by the light-receiving unit 26.

[0044] The light-emitting unit 22 and the light-receiving unit 26 together are called an extinction ratio detection optical device. For the extinction ratio detection optical device to function, it is sufficient that 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, it is not necessary for the light beam LB to actually be able to pass through them.

[0045] If 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 detection unit 12 of the extinction ratio measuring device 1 according to the present invention can be formed simply by mounting them in a predetermined position. In other words, the optical device for extinction ratio detection can be sold as is.

[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 crossed nicols (adjusted so that the polarization direction is rotated 90° and different). However, polarizing elements PE rarely have uniform polarization characteristics over a large 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 of the polarizing element PE.

[0047] Figure 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 to the back 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 almost constant in the minute portion SA.

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

[0049] In other words, the light-emitting unit 22 is composed of one polarizer 40, and the light beam receiving element 62 is configured so that an analyzer 50 is attached to each of the light beam receiving elements 62 and can be adjusted individually. Alternatively, the opposite is true: each of the light beam light-emitting elements 32 is individually fitted with a polarizer 40 and can be adjusted individually, and the light-receiving unit 26 is composed of only one analyzer 50.

[0050] In this way, even if the polarization characteristics of the polarizing element PE itself are not constant depending on the location, the lower limit of measurement Ib can be adjusted to be small, so that the extinction ratio PER can be increased for each light beam LB. In other words, even if the extinction value Im of the object under inspection M is small, the extinction ratio PER can be calculated. To put it another way, the extinction ratio PER can be measured with a wide dynamic range.

[0051] Of course, both the light-emitting unit 22 and the light-receiving unit 26 may be composed of a single polarizer 40 and analyzer 50. Alternatively, both the light-emitting unit 22 and the light-receiving unit 26 may be configured with as many polarizers 40 and analyzers 50 as there are light beams LB.

[0052] Figure 4 shows (i) a view of the polarizer 40 and light beam light-emitting element 32 from the space 24 where the object to be inspected is located, and (ii) a view of the analyzer 50 and light beam photodetector 62 from the space 24 where the object to be inspected is located. Figure 4(a) shows the case where both the polarizer 40 and the analyzer 50 are formed from a single glass polarizing element.

[0053] On the other hand, in Figure 4(b), the polarizer 40 is formed from a single glass polarizing element PE, while the analyzer 50 uses a glass polarizing element PE that covers two light beam receiving elements 62, and each is shown with angle adjustments made so that the lower limit of measurement Ib is lower. That is, the transmission axis Tax 50 of each analyzer 50 is adjusted to be crossed nicols with respect to the transmission axis Tax 40 of the polarizer 40. Note that angle adjustments may include 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 relative to the light beam LB.

[0054] In this manner, when the light beam emission unit 30 and light beam receiving unit 60, which emit and receive multiple light beams LB, allow for adjustment of the lower limit of measurement Ib using multiple polarizers 40 or analyzers 50, it is said that "the polarizers or analyzers can be individually adjusted" or "individually adjustable." The number of individually adjustable polarizing elements PE in one light emission unit 22 should be two or more, or less than or equal to the number of light beam receiving units 60.

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

[0056] Furthermore, it is sufficient to have multiple polarizers 40 or analyzers 50 within a single light-emitting unit 22 or light-receiving unit 26. If an individually adjustable polarizing element PE is used in either the light-emitting unit 22 or the light-receiving unit 26, it does not need to be used in the other. In other words, it is sufficient for at least one of the polarizers 40 and analyzers 50 to be individually adjustable. Figure 4 shows the case where the analyzer 50 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 standardized state. Measuring the extinction ratio PER with multiple light beams LB allows for measuring the extinction ratio PER at multiple locations simultaneously. However, when measuring the extinction ratio PER in the same region, the measured values ​​cannot be trusted if the measured values ​​of the extinction ratio PER for each light beam LB are not standardized. As will be shown in the embodiments described later, it is preferable to make the polarizer 40 or analyzer 50 individually adjustable for each light beam LB.

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

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

[0060] <Optical beam receiving element 62> The light beam receiving element 62 consists of an analyzer 50, the incident end 64a of a light-receiving optical fiber 64, and a light-receiving collimator lens 66. The incident end 64a of the light-receiving optical fiber 64 and the light-receiving collimator lens 66 constitute the light beam receiving section 60. The advantages of using the light-receiving optical fiber 64 and the light-receiving collimator lens 66 will now be explained. Figure 6 shows the object under inspection M, the analyzer 50, the light-receiving collimator lens 66, and the light-receiving optical fiber 64 and its incident end 64a. Here, scattered light R is generated in the optically heterogeneous region D of the object under inspection M and is shown passing through the analyzer 50.

[0061] Suppose the scattered light R cannot be received by the designated light beam receiving unit 60α and instead enters the receiving-side collimator lens 66β of the adjacent light beam receiving unit 60β. However, if the scattered light R incident on the receiving-side collimator lens 66β is incident at an angle larger than the NA of the receiving optical fiber 64β, it cannot guide the receiving optical fiber 64β. Thus, when the light beam receiving element 62 is composed of a receiving-side collimator lens 66 and a receiving optical fiber 64, it does not guide the scattered light R from the adjacent light beam LB. As a result, it is possible to accurately capture the minute optical power from a minute region irradiated by the light beam LB without being affected by the scattered light R from the object M under inspection.

[0062] <Measurement Flow> Next, the operation of the extinction ratio measuring device 1 will be explained. Figure 7 shows the measurement flow of the control unit 16. Referring to Figure 7, when measurement starts with the extinction ratio measuring device 1 (step S100), a termination decision is made (step S102). If the measurement is to be terminated (Y branch in step S102), the extinction ratio measuring device 1 is stopped (step S104). If the measurement is to continue (N branch in step S102), the processing flow moves 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 space 24 where the object to be inspected is located (N branch in step S106). Once confirmed (Y branch in step S106), the process moves on 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 done by opening and closing a door that can open the extinction ratio detection unit 12, or by detecting it with a light intensity sensor located near the light receiving unit 26. If confirmed (Y branch in step S108), the process proceeds to the next step.

[0065] Next, the optical beam LB is measured to obtain the calibration value Ref (step S110). Specifically, the optical beam LB is emitted from the light-emitting unit 22, and the individual optical beams LB are received by the light-receiving unit 26. Since a half-wave plate is placed in the space 24 where the object to be inspected is located, the polarization aligned in one direction by the polarizer 40 passes almost completely 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. In other words, 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 for each light beam LB. At this time, a message such as "Calibration value recording complete" may be displayed on the input / output display unit 18.

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

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

[0069] If the extinction ratio detection unit 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 is obtained using equation (1). The calculated extinction ratio PER is displayed on the input / output display unit 18, and the process returns to the termination determination (step S102). In this manner, the extinction ratio PER can be measured.

[0071] (Variation 1) Figure 8 shows a modified example 1 of the light-emitting unit 22. The light-emitting unit 22 consists of two light beam-emitting elements 32, a beam splitter 80, a total reflection mirror 82, and a polarizer 40. Parallel light rays LB1 emitted from the light beam-emitting elements 32 are split into a component LB3 that is reflected at the surface of the beam splitter 80 and a component LB2 that is refracted and transmitted through the beam splitter 80. The transmitted component LB2 passes through the polarizer 40 and its polarization direction is aligned. The reflected component LB3 is totally reflected by the total reflection mirror 82 and strikes the surface of the beam splitter 80 again. It then splits again into a component LB3 that is reflected and a component LB2 that is transmitted through the beam splitter 80.

[0072] In this way, by splitting a parallel light beam LB1 emitted from a single light beam light-emitting element 32 into multiple beams using a beam splitter 80 and a total reflection mirror 82, multiple light beams LB can be generated. With this configuration, many light beams LB can be generated with fewer light beam light-emitting elements 32, thereby reducing the cost of the extinction ratio measuring device 1 itself.

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

[0074] (Modification 2) Figure 9 shows a modified example of the light receiving unit 26. The light beam receiving elements 62 of the light receiving unit 26 also have physical size, and even if the light beam receiving elements 62 are placed in close contact with each other, there are cases where light cannot be received due to the distance between the light beams LB from the light emitting unit 22. As shown in Figure 9, the direction of the light beam LB that has passed through the analyzer 50 is changed by the total internal reflection prism 84, and the distance W between the light beams LB is changed by the optical path changing section 86 which is a combination of a rhomboid prism, a dove prism, etc. LBThe interval width W 62 The beam is widened so that it can be received by the light beam receiving element 62. Note that the initial total internal reflection prism 84 is optional.

[0075] (Variation 3) Figure 10 shows a configuration combining the light-emitting unit 22 of Modification 1 and the light-receiving unit 26 of Modification 2. It can be said that it 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, light-receiving unit 26a and light-receiving unit 26b. The narrow light beam spacing W is not limited by the physical size of the light-emitting unit 22 and the light-receiving unit 26. LB This can be achieved. In other words, it is possible to measure the extinction ratio PER in a narrow area. [Examples]

[0076] (Example 1) Fourteen pairs of light beam light-emitting elements 32 and light beam photodetectors 62 were combined to form a light-emitting unit 22 and a light-receiving unit 26. Furthermore, the light beam LB from each light beam light-emitting element 32 was adjusted so that it could be received by the corresponding light beam photodetector 62. A set of light beam light-emitting elements 32 and light beam photodetectors 62 arranged in this way is called a channel. Therefore, an optical path for 14 channels of light beam LB was constructed here. The channels were arranged in parallel at a distance of 2 mm from each other.

[0077] The number of analyzers 50 on the light-receiving unit 26 was set to one for every 14 light beam photodetectors 62, and the number of polarizers 40 on the light-emitting unit 22 was changed to investigate the lower limit of measurement Ib. In this case, nothing was placed in the space 24 where the object under inspection was placed, which was 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 polarizers 40 were adjusted so that they were crossed nicols with respect to the analyzer 50 for each group of shared light beam light-emitting elements 32.

[0078] The results are shown in Figure 11. Figure 11(a) shows the view of the light beam emission unit 30 from the space 24 where the object under inspection is placed, when the polarizer 40 is divided into 2 parts, when the polarizer 40 is divided into 7 parts, and when the polarizer 40 is divided into 14 parts. Each figure shows that the polarizer 40 is divided into 14 channels.

[0079] Due to the non-uniformity of the Tax transmission axis of the lower limit of measurement, the average lower limit values ​​for each channel were not the same. On the right side of each figure, the improvement in the average value of the lower limit Ib and the deviation of the lower limit are shown for 14 channels.

[0080] The improvement in the average value of the lower limit Ib for all 14 channels was calculated by setting the average value of the lower limit Ib (average value of 14 channels) when the polarizer 40 in Figure 11(a) was divided into two as 0 dB, and then determining the improvement from the value when it was divided into two (this is the lower limit Ib, so it is the drop).

[0081] The more negative the improvement, the lower the detection limit Ib, which is desirable. If the improvement in the detection limit Ib is large, the calibration value Ref in each channel will have little difference between channels, and a high extinction ratio PER can be measured.

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

[0083] Figure 12 shows this in graph form. Referring to Figure 12, the horizontal axis shows the number of divisions of the polarizer 40 for the 14 channels, and the left vertical axis shows the average value (dB) of the lower limit of measurement. The right vertical axis shows the deviation (dimensionless) of the lower limit of measurement. By setting the number of divisions of the polarizer 40 to be the same as the number of light beam emission units 30, and adjusting each light beam emission unit 30 to have crossed nicols with the analyzer 50, the average value and deviation of the lower limit of measurement Ib for the 14 channels were reduced.

[0084] In this way, even when a large number of light beam light-emitting elements 32 and light beam photodetectors 62 are arranged in parallel at 2 mm intervals, a high extinction ratio PER can be achieved, and an extinction ratio measuring device can be constructed that also equalizes measurement variations between channels. [Industrial applicability]

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

[0086] 1 Extinction ratio measuring device 10 Light source section 12 Extinction ratio detection unit 14 Photoelectric conversion unit 16 Control Unit 18 Input / Output Display Unit 20. Light beam distribution section 22 Light-emitting units 24 Space for placing the object under inspection 26 Light receiving unit 30 Light beam emission section 32 Light beam light-emitting element 34 Light-emitting optical fibers 34a (Output end of light-emitting optical fiber) 32w (width of the output end of the light-emitting optical fiber) 36. Collimator lens on the light-emitting side 36AR Emitting-side lens array 40 polarizers 50 Photometer 60 Light beam receiving section 62 Light beam photodetector 64 Optical fiber for receiving light 64a (Input end of optical fiber for receiving light) 66 Light-receiving collimator lens 66AR Receiver-side lens array 80 Beam Splitter 82 Total Reflection Mirror 84 Total Internal Reflection Prism 86 Optical path changing section Ib lower limit of detection Ref Calibration Value M Test object Im extinction value PER extinction ratio LB Light Beam PE polarizing pixels Tax transparent axis SA minute part R Scattered light

Claims

1. Light source section, The light from the aforementioned light source is split into multiple light-emitting optical fibers to form multiple light beams. The light beam distribution section, An extinction ratio detection unit that detects the plurality of light beams from the light source unit that have passed through the object to be inspected, The unit includes a photoelectric conversion unit that converts the plurality of light beams from the extinction ratio detection unit into electrical signals. The extinction ratio detection unit is, A light beam emitting unit that converts the plurality of light beams into parallel rays and emits them in parallel, The system has a polarizer that aligns the polarization of the light beam in one direction, and applies linear polarization to the object under inspection. Irradiate Light-emitting unit and The relationship between the polarizer and the crossed nicols is adjusted, and the light beam that has passed through the object under inspection The analyzer through which the frame passes, It has a light beam receiving unit that receives light for each light beam that has passed through the analyzer, The aforementioned light beam receiving unit has a light beam receiving element corresponding to each of the plurality of light beams, The aforementioned light beam receiving element is A light-receiving collimator lens that focuses the aforementioned light beam, A light-receiving optical element having an incident end into which light focused by the light-receiving collimator lens is incident. Having Light receiving unit, The object to be inspected is placed between the light beam emitter and the analyzer. A space for placing the object to be inspected was provided. Extinction ratio measuring device.

2. The polarizer is a light extinction ratio measuring device according to claim 1, in which the transmission axis differs for each of the light beams. 。

3. Either the polarizer or the analyzer is configured to be individually adjustable for each light beam. The extinction ratio measuring device according to claim 1.

4. The light beam emitting unit has a light beam emitting element corresponding to the light beam, The aforementioned light beam light-emitting device is The light-emitting optical fiber, Light-emitting collimator that makes the light emitted from the output end of the aforementioned light-emitting optical fiber into parallel rays. An extinction ratio measuring device according to any one of claims 1 to 3, comprising a lens.

5. The aforementioned light beam emission unit is The light-emitting optical fiber, Light-emitting collimator that makes the light emitted from the output end of the aforementioned light-emitting optical fiber into parallel rays. Lens and, A beam split occurs when some of the light from the light-emitting collimator lens is transmitted and some is reflected. Ta and, The light reflected by the beam splitter is subjected to total internal reflection and irradiated back onto the beam splitter. Extinction ratio measuring device according to any one of claims 1 to 3, having a total reflection mirror. 。

6. The system includes a control unit that calculates the extinction ratio of the object under inspection for each signal from the light-receiving optical fiber. An extinction ratio measuring device according to any one of claims 1 to 3.

7. A light beam emitting unit that converts multiple input light beams into parallel rays and emits them in parallel, The system has a polarizer that aligns the polarization of the aforementioned light beam in one direction, and irradiates the object to be inspected with linearly polarized light. Light-emitting unit and, The light beam, adjusted to the relationship between the polarizer and the crossed nicols, has passed through the object under inspection. The analyzer through which it passes, It has a light beam receiving unit that receives light for each light beam that has passed through the analyzer, The aforementioned light beam receiving unit has a light beam receiving element corresponding to each of the plurality of light beams, The aforementioned light beam receiving element is A light-receiving collimator lens that focuses the aforementioned light beam, The optical fiber has an input end into which light focused by the light-receiving collimator lens is incident. An optical device for detecting extinction ratio, consisting of a pair of light-receiving units.

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