Photometric / colorimetric device

Abstract

A photometric / colorimetric device with improved measurement accuracy is provided.　This photometric / colorimetric device comprises: an objective optical system that condenses light from a target object; a light guide unit that guides light incident via the objective optical system; and a photoelectric conversion unit that receives the light guided by the light guide unit and converts the light into an electrical signal. The light guide unit comprises a bundled fiber in which a plurality of fiber strands are fused together at an incident end portion.

Description

Photometric and colorimetric device

[0001] The present disclosure relates to a photometric and colorimetric device.

[0002] As a device for measuring the brightness and color of light in a measurement object, a photometric and colorimetric device is known (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2003-247891

[0004] In a photometric and colorimetric device, in order to perform measurement accurately, it is desirable to conduct light from the measurement object without leakage within a range of a predetermined emission angle or in a predetermined measurement region. However, the bundle fiber as a light guiding part disclosed in Patent Document 1 has a large number of gaps between a plurality of fiber strands, and light from the measurement object is not guided through these gaps. Therefore, there was room for improvement in improving the measurement accuracy by reducing the gaps of the bundle fiber.

[0005] The problem to be solved by the present disclosure is to provide a photometric and colorimetric device with improved measurement accuracy.

[0006] To solve the above problems, the photometric and colorimetric device of the present disclosure includes an objective optical system that condenses light from a target object, a light guiding part that guides the light incident by the objective optical system, and a photoelectric conversion part that receives the light guided by the light guiding part and converts it into an electrical signal. In the photometric and colorimetric device, the light guiding part includes a bundle fiber in which a plurality of fiber strands are fused at an incident end portion.

[0007] According to the present disclosure, the measurement accuracy in a photometric and colorimetric device can be improved.

[0008] This is a perspective view showing the appearance of a photometric colorimeter. This is a block diagram showing the functional configuration of a photometric colorimeter. This is a diagram showing the specific configuration of the objective optical system, light guide unit, and photoelectric conversion unit. This is a diagram showing the illumination range of the light beam emitted from the optical fiber. This is a perspective view showing the appearance of a bundled fiber. This is a partial enlarged view of the incident surface when fiber strands are held bundled together with adhesive. This is a cross-sectional view of the incident surface when fiber strands are held bundled together with adhesive. This is a partial enlarged view of the incident surface when fiber strands are fused together. This is a partial enlarged view of the incident surface when multiple fiber strands are fused together. This is a cross-sectional view of the incident surface when fiber strands are held bundled together by fusion. This is an optical path diagram of light incident from the display surface of a display to the bundled fiber when the objective optical system is a collimating system. This is a view of the bundled fiber from the incident surface side. This is an explanatory diagram of a display used for calibration. This is an explanatory diagram of a display having orientation characteristics in angular range β. This is an explanatory diagram of the Lambertsian distribution. This is a graph showing the brightness measurement values ​​during calibration. This is a graph showing the brightness measurement values ​​when a display having characteristics in a region where light cannot be received is measured. This is a graph showing the brightness measurement values ​​during calibration. This is a graph showing the brightness measurement values ​​when measuring a display with characteristics in a region where light cannot be received. This is an optical path diagram of light incident from the display surface of the display to the bundle fiber when the objective optical system is an imaging system. This is an explanatory diagram of the display used for calibration. This is an optical path diagram of light incident from the display surface of a display with brightness unevenness in region AR1 to the bundle fiber. This is a graph showing the brightness measurement values ​​when measuring a display with characteristics in a region where light cannot be received. This is an example of an image generated on the incident surface of the bundle fiber. This is an explanatory diagram of a method for measuring the variation f2g of a photometric colorimeter. This is a schematic diagram of the vicinity of the emission surface of a bundle fiber in which fiber strands are bundled with adhesive. This is a schematic diagram of a photoelectric conversion unit that receives light emitted from a bundle fiber in which fiber strands are bundled with adhesive. This is a schematic diagram of a photoelectric conversion unit that receives light emitted from a bundle fiber in which fiber strands are bundled by fusion splicing. This is an explanatory diagram of how light incident on a fiber strand is guided within the fiber strand.

[0009] Hereinafter, one or more embodiments of this disclosure will be described with reference to the drawings. However, the scope of this disclosure is not limited to the disclosed embodiments.

[0010] [Functional Configuration of Photometric Colorimeter] Figure 1 is a perspective view showing the external appearance of the photometric colorimeter 1. Figure 2 is a block diagram showing the functional configuration of the photometric colorimeter 1.

[0011] The photometric colorimeter 1 is used, for example, in the inspection process of a manufacturing line for liquid crystal displays or organic light-emitting diode (OLED) displays. The photometric colorimeter 1 measures, for example, the color, brightness, light waveform (change in light intensity), flicker, etc., of the display surface 12 of the display, which is the object to be measured. The photometric colorimeter 1 is positioned opposite the display surface 12 of the display at a predetermined distance (for example, 3 cm).

[0012] The configuration of the photometric colorimeter 1 will now be described. The photometric colorimeter 1 comprises an objective optical system 21, a light guide unit 24, a photoelectric conversion unit 25, an amplification unit 26, an A / D conversion unit 31, a storage unit 32, a control unit 36, a power supply unit 37, and a communication unit 38. Light from the display surface 12 of the display is photoelectrically converted into an electrical signal (analog signal), the converted analog signal is converted into a digital signal, and the converted digital signal is subjected to various processing. In addition, the photometric colorimeter 1 may also include an operation unit and a display unit (not shown).

[0013] The photometric colorimeter 1 may be connected to a personal computer (not shown) or the like. In this case, the operation unit and display unit (not shown) may be provided on the personal computer.

[0014] Details of each part will be explained.

[0015] Figure 3 shows the specific configuration of the objective optical system 21, the light guide unit 24, and the photoelectric conversion unit 25. In this embodiment, measurements are taken using a direct reading of tristimulus values. Also, although Figure 3 shows an example of a collimating system, an imaging system may also be used.

[0016] The objective optical system 21 is provided as an incident section for receiving light from the display. The objective optical system 21 consists of a single lens or multiple lenses and has positive power.

[0017] The light guide unit 24 guides the light incident by the objective optical system 21. The light guide unit 24 includes an optical fiber 55 that propagates the incident light and divides it into three light beams, and condensing lenses 56p, 56q, and 56r having positive power. Hereafter, when it is not necessary to distinguish between the condensing lenses 56p, 56q, and 56r, they will be collectively referred to as the condensing lens 56. Note that the condensing lens 56 is not necessarily required.

[0018] The light guide unit 24 is located on the optical axis L1 of the light incident by the objective optical system 21. Hereinafter, "the optical axis L1 of the light incident by the objective optical system 21" will also be simply referred to as "the optical axis L1 of the objective optical system 21" or "the optical axis L1".

[0019] The optical fiber 55 is composed of multiple optical fiber strands bundled together. The bundled optical fiber strands of the optical fiber 55 branch into three in the middle, resulting in one optical beam incident surface A and three optical beam exit surfaces B1, B2, and B3. The optical fiber 55 is positioned such that the optical beam incident surface A is located at a distance of the focal length f of the objective optical system 21 from the image-side principal point PP of the objective optical system 21. In other words, the objective optical system 21 and the optical fiber 55 constitute a telecentric optical system. For the sake of explanation, in this embodiment, the image-side principal point is shown to be approximately the same as the object-side principal point.

[0020] The photometric colorimeter 1 is positioned at a predetermined distance from the display surface 12 of the display. At this time, of the light beams emitted from each part of the area under measurement AR, only those light beams with an emission angle of less than or equal to the maximum value α with respect to the normal direction of the area under measurement AR are incident on the light beam incident surface A of the optical fiber 55. The normal direction of the area under measurement AR is the direction parallel to the optical axis L1. Hereinafter, the maximum value α of the emission angle will also be called the "maximum emission angle α". The maximum emission angle α is determined by the focal length f of the objective optical system 21 and the diameter R at the light beam incident surface A of the optical fiber 55. The incident light beam is divided into three light beams within the optical fiber 55 and emitted from the light beam emission surfaces B1, B2, and B3, respectively. Hereinafter, when it is not necessary to distinguish between the light beam emission surfaces B1, B2, and B3, they will be collectively referred to as the light beam emission surface B.

[0021] Each fiber strand constituting the optical fiber 55 has a two-layer structure consisting of a core located in the center and a cladding surrounding the core. The core is designed to have a higher refractive index than the cladding, and light propagates confined within the core by total internal reflection. Further details about the optical fiber 55 will be described later.

[0022] The optical fiber 55 is bent into a predetermined shape while the light beam incident surface A and the light beam exit surface B are fixed. If there are no changes in state such as vibration, shock, or temperature changes, the position of the optical fiber 55 does not change, and the light incident on the light beam incident surface A exits from the light beam exit surface B at a predetermined angle. However, if there are changes in state such as vibration, shock, or temperature changes, the degree of bending of the optical fiber 55 changes, and the light incident on the light beam incident surface A exits from the light beam exit surface B at an angle that is shifted from the predetermined angle. In this case, since the angle of incidence of light to the filter 61, which will be described later, is shifted from the predetermined angle, it is preferable that the filter 61 does not depend on the angle of incidence in its spectral sensitivity characteristics.

[0023] Light emitted from the light beam emission surfaces B1, B2, and B3 of the optical fiber 55 enters the condensing lenses 56p, 56q, and 56r, respectively. The optical axis L21 of the condensing lens 56p coincides with the optical axis of the light emitted from the light beam emission surface B1 of the optical fiber 55. The optical axis L22 of the condensing lens 56q coincides with the optical axis of the light emitted from the light beam emission surface B2 of the optical fiber 55. The optical axis L23 of the condensing lens 56r coincides with the optical axis of the light emitted from the light beam emission surface B3 of the optical fiber 55. The condensing lens 56 focuses the incident light. Hereafter, when it is not necessary to distinguish between optical axes L21, L22, and L23, they will be collectively referred to as optical axis L2.

[0024] The photoelectric conversion unit 25 receives light guided by the light guide unit 24 and converts it into an electrical signal corresponding to its intensity. The photoelectric conversion unit 25 includes filters 61p, 61q, and 61r that transmit light in different wavelength ranges, and light receiving sensors 62p, 62q, and 62r that receive the transmitted light. Filters 61p, 61q, and 61r are filters for correcting to the spectral sensitivity of a standard observer as defined by the International Commission on Illumination (CIE), and light receiving sensors 62p, 62q, and 62r have the spectral sensitivity characteristics of a standard observer. Hereinafter, when it is not necessary to distinguish between filters 61p, 61q, and 61r, they will be collectively referred to as filter 61. When it is not necessary to distinguish between light receiving sensors 62p, 62q, and 62r, they will be collectively referred to as light receiving sensor 62.

[0025] Filter 61p is sensitive to the R (red) wavelength region. Due to this filter characteristic, the light receiving sensor 62p is corrected to have a light receiving sensitivity of a color matching function (X-bar-lambda) that has high sensitivity in the red wavelength region. Filter 61q is sensitive to the G (green) wavelength region. Due to this filter characteristic, the light receiving sensor 62q is corrected to have a light receiving sensitivity of a color matching function (Y-bar-lambda) that has high sensitivity in the green wavelength region. Filter 61r is sensitive to the B (blue) wavelength region. Due to this filter characteristic, the light receiving sensor 62r is corrected to have a light receiving sensitivity of a color matching function (Z-bar-lambda) that has high sensitivity in the blue wavelength region. The light receiving sensor 62 outputs a received signal corresponding to the tristimulus values ​​(X, Y, Z). Each filter 61 is positioned appropriately between the light receiving sensor 62 and the condensing lens 56.

[0026] The light receiving sensor 62p is located on the optical axis L21 of the condensing lens 56p. The light receiving sensor 62q is located on the optical axis L22 of the condensing lens 56q. The light receiving sensor 62r is located on the optical axis L23 of the condensing lens 56r. The light receiving sensor 62 is positioned such that the illumination range of the light focused by the condensing lens 56 is included in the light receiving range of the light receiving sensor 62.

[0027] Figure 4 shows the illumination range of the light beam emitted from the bundle fiber. The focusing lens 56p focuses the light beam emitted from the light beam emission surface B1 of the optical fiber 55 onto the light receiving sensor 62p, and makes the illumination range LA of the light beam approximately coincide with the light receiving range SA of the light receiving sensor 62p. As shown in Figure 4, it is preferable that the entire illumination range LA of the light beam is included within the light receiving range SA.

[0028] Similarly, the focusing lens 56q focuses the light beam emitted from the light beam emission surface B2 of the optical fiber 55 onto the light receiving sensor 62q, and adjusts the illumination range of the light beam to approximately match the light receiving range of the light receiving sensor 62q. The focusing lens 56r focuses the light beam emitted from the light beam emission surface B3 of the optical fiber 55 onto the light receiving sensor 62r, and adjusts the illumination range of the light beam to approximately match the light receiving range of the light receiving sensor 62r.

[0029] In this way, the focusing lens 56 can focus the light beam emitted from the optical fiber 55 into the light-receiving range of the light-receiving sensor 62. This allows the light-receiving sensor 62 to be miniaturized and its junction capacitance to be reduced, thereby reducing random noise generated in the amplification unit 26.

[0030] The light beam incident on the optical fiber 55 is incident on the light receiving sensor 62 in three equal parts. The light beam here refers to all the light beams emitted from each part of the measurement area AR of the display, with an emission angle α or less relative to the normal direction in the measurement area AR. In other words, even if the light receiving sensor 62 is miniaturized by using the focusing lens 56, the amount of light received by the light receiving sensor 62 does not decrease.

[0031] The amplification unit 26 amplifies the electrical signal output from the light receiving sensor 62, for example, by integrating it. By having the amplification unit 26 simultaneously integrate the electrical signal output from the light receiving sensor 62, the tristimulus values ​​(X, Y, Z) can be converted into a synchronized time-series signal. In other words, simultaneity can be ensured.

[0032] Even if the amplification unit 26 does not guarantee simultaneity, if the delay time of each signal is known in advance, the time difference in each signal of the final output stimulus value can be corrected to ensure simultaneity in each signal. In other words, if the time difference in each signal of the final output stimulus value can be corrected, each signal can be considered a synchronous time-series signal.

[0033] The amplification unit 26 may be amplified by an integrating circuit or by another transimpedance amplifier circuit. Alternatively, the light guide unit 24 and the photoelectric conversion unit 25 may be configured as four channels, with three of these channels amplified by an integrating circuit to obtain the aforementioned tristimulus values, and the remaining channel amplified by a transimpedance amplifier circuit to obtain a signal for flicker measurement. Flicker refers to the flickering of a display, and it is common to use a signal corrected to a color matching function (wye-bar-lambda) as the light receiving sensitivity.

[0034] The A / D conversion unit 31 converts the electrical signal (analog signal) input from the amplification unit 26 into a digital signal.

[0035] The memory unit 32 stores the digital signals output from the A / D conversion unit 31.

[0036] The control unit 36 ​​controls the measurement operation by centrally controlling the operation of each part within the photometric colorimeter 1. The control unit 36 ​​uses the measurement data stored in the memory unit 32 to perform predetermined calculations, such as correction of dark output. The control unit 36 ​​also calculates tristimulus values ​​(X, Y, Z), xyY (chromaticity coordinates, luminance) as defined by the CIE, TΔuvY (correlated color temperature, color difference from blackbody locus, luminance), etc. Furthermore, the control unit 36 ​​may also derive an index for flicker.

[0037] The control unit 36 ​​controls the photoelectric conversion unit 25, the amplification unit 26, the A / D conversion unit 31, the storage unit 32, the power supply unit 37, and the communication unit 38. The control unit 36 ​​may also be connected to the object to be measured. By connecting to the object to be measured, the emission conditions of the object during measurement can be set.

[0038] The power supply unit 37 transforms the voltage of the power supplied from an external AC adapter (not shown) and supplies power to each component via the control unit 36.

[0039] The communication unit 38 outputs the calculation results from the control unit 36 ​​to the outside. The output calculation results are displayed in the form of a data list, graph, etc., on a personal computer (not shown). In addition, various information related to the measurement is input from the personal computer via the communication unit 38. Examples of such information include measurement instructions, display mode settings, and measurement range.

[0040] [Structure of Bundle Fibers] The structure of bundle fibers according to this embodiment and the effects obtained by this structure will be described below.

[0041] The aforementioned optical fiber 55 is a bundled fiber. Figure 5 is a perspective view showing the appearance of the bundled fiber.

[0042] The bundled fiber 70 is formed by bundling a plurality of fiber strands 80 together at the incident end portion 71 (entrance) and branching them randomly into a plurality of strands and bundling them respectively at the emission end portion 73 (exit). In the present embodiment, the "incident end portion" refers to the end portion including the incident surface, and the "emission end portion" refers to the end portion including the emission surface. The length of the end portion is not limited, and the incident end portion 71 or the emission end portion 73 only needs to include at least the incident surface 72 or the emission surface 74 respectively. Since the fiber strands are bundled and held at the end portion, that is, the positions of the respective fiber strands are fixed, if the length of the end portion is too long, it is difficult to obtain the flexibility of the bundled fiber, and the degree of freedom is likely to decrease. From such a viewpoint, the length of the end portion is preferably within the range of 5 to 20 mm.

[0043] In the present embodiment, in the bundled fiber 70, the portion bundled together is defined as the central portion 75, and the branched portion is defined as the branching portion 76. From the viewpoint of flexibility, it is preferable that the positions of the respective fiber strands are not fixed in the portion excluding the incident end portion 71 of the central portion 75 and the portion excluding the emission end portion 73 of the branching portion 76.

[0044] The diameter of the fiber strand is not particularly limited, but is preferably within the range of 0.03 to 0.3 mm. The number of fiber strands to be bundled is not particularly limited, but is preferably within the range of several hundreds to several thousands. On the emission side, the bundled fiber 70 branches into three, for example, corresponding to the three stimulus values (X, Y, Z). The material of the fiber strand is not particularly limited, and may be a multi-component glass or may be plastic.

[0045] Conventionally, an adhesive was filled between the respective fiber strands and cured to maintain the state in which the fiber strands were bundled. FIG. 6 is a partially enlarged view of the incident surface in the case where the fiber strands are held in a bundled state by an adhesive. The adhesive 81 enters between the plurality of fiber strands 80, and then, by curing the adhesive 81, the fiber strands 80 can be held in a bundled state. [[ID=IO]]

[0046] If the adhesive 81 does not penetrate between the fiber strands 80, the fiber strands 80 cannot maintain a bundled state. Therefore, the adhesive 81 always penetrates between the fiber strands 80. That is, in the incident cross-section of adjacent fiber strands 80, the center-to-center distance between their respective geometric centers is greater than twice the radius of the fiber strand 80.

[0047] Let the geometric center of the fiber strand 801 be point C1, the geometric center of the fiber strand 802 be point C2, and the radius of the fiber strands 801 and 802 be r. It can be seen that the center-to-center distance of the geometric centers, that is, the distance between point C1 and point C2, is greater than twice the radius r of the fiber strands 801 and 802 by the amount that the adhesive 81 penetrates.

[0048] FIG. 7 is a cross-sectional view of the incident surface when the fiber strands are held in a bundled state by an adhesive. When the fiber strands 80 are held in a bundled state by the adhesive 81, in the incident surface 72, a region 82 where the fiber strands exist and a gap between the fiber strands 80, that is, a region 83 where no fiber strands exist, are formed. The light incident in the region 82 where the fiber strands exist is guided in the fiber strands 80, but the light incident in the region 83 where no fiber strands exist is not guided. That is, a part of the light incident on the bundle fiber 70 is not guided. In this case, let the diameter of the bundle fiber be h1.

[0049] On the other hand, in this embodiment, the bundled state of the fiber strands is maintained by fusing multiple fiber strands together. Figure 8 is a partially enlarged view of the incident surface when the fiber strands are fused together. In fusion, a portion of the fiber strands is melted and pressure is applied in the direction that bundles multiple fiber strands together, causing adjacent fiber strands to become one, and then solidifying to join adjacent fiber strands. In addition, no other material enters between adjacent fiber strands during fusion. Furthermore, when the fiber strands 80 are melted, their degree of freedom in shape increases, and they are easily deformed to fill the gaps between each fiber strand 80 when pressure is applied afterward. Therefore, it can be seen that the distance between the centers of the geometric centers of the fiber strands, i.e., the distance between point C1 and point C2, is smaller than twice the radius r of the fiber strands 801 and 802.

[0050] Figure 9 is a magnified view of a portion of the incident surface when multiple fiber strands are fused together. In the example shown in Figure 9, the fiber strands are deformed from circular to hexagonal due to fusion. In this case as well, no other material enters between adjacent fiber strands, and it can be seen that the distance between the centers of the geometric centers of the fiber strands, i.e., the distance between points C1 and C2, is smaller than twice the radius r of the fiber strands 801 and 802. By deforming to a hexagon, the gaps between the fiber strands can be further reduced, bringing it closer to a close-packed structure. Furthermore, by achieving a close-packed structure, the incident surface 72 can be limited to a region 82 where only fiber strands exist.

[0051] Figure 10 is a cross-sectional view at the incident surface when the same number of fiber strands as in Figure 9 are held bundled together by fusion. When the fiber strands 80 are held bundled together by fusion, the area of ​​the gaps between each fiber strand 80, i.e., the area where no fiber strands exist, can be made as small as possible at the incident surface 72. Preferably, the area of ​​the gaps is 5% or less of the area of ​​the cross-section of the incident end, i.e., the area of ​​the incident surface 72. In the bundled fiber where the fiber strands are bundled with adhesive as shown in Figure 7, the area of ​​the gaps is about 20% of the area of ​​the incident surface 72.

[0052] In particular, in the close-packed structure shown in Figure 10, the area of ​​the gaps between each fiber strand 80 can be reduced to zero, leaving only the region 82 where the fiber strands exist. In other words, almost all of the light incident on the bundle fiber 70 is guided. Also, in the close-packed structure shown in Figure 10, the diameter of the bundle fiber 70 can be reduced by the amount that the distance between points C1 and C2 of each fiber strand 80 in Figure 9 becomes less than twice the radius r. If the diameter of the bundle fiber 70 in this case is h2, then h2 is smaller than the aforementioned h1.

[0053] From the viewpoint of flexibility, it is preferable that each fiber strand in a bundled fiber is not fixed in position except at the ends; in other words, it is preferable that it is not fused except at the ends. This allows the radius of the fiber strand to be measured from the cut surface by cutting the fiber strand at the unfused portion. From the obtained radius measurement, it is possible to determine whether the distance between the centers of the geometric centers of each fiber strand in the incident cross-section of the bundled fiber is less than twice the radius of the fiber strand.

[0054] Next, we will explain how minimizing the area where fiber strands are absent in a bundled fiber improves the accuracy of measurements in a photometric colorimeter.

[0055] Figure 11 is an optical path diagram of light incident from the display surface to the bundle fiber when the objective optical system is a collimating system. Figure 12 is a view of the bundle fiber from the incident surface side. In Figures 11 and 12, the bundle fiber 70 has its fiber strands bundled together with adhesive at the incident end, and the incident surface 72 has a region 83 where no fiber strands are present. For illustrative purposes, the area of ​​the region 83 where no fiber strands are present is made relatively large and circular.

[0056] As shown in Figure 11, light emitted from point A within the display surface 12 of the display in an angular range α enters the incident surface 72 of the bundle fiber 70 and is guided by the bundle fiber 70. However, of this light, light that enters the region 83 where no fiber strands exist, i.e., light emitted from point A in an angular range β, is not guided by the bundle fiber 70 and is not measured. Although not shown in Figure 11, the same applies to points B and C; light emitted in an angular range β is not guided by the bundle fiber 70 and is not measured, just like at point A. In other words, in a collimated system, because there is a region 83 within the bundle fiber 70 where no fiber strands exist, light emitted in an angular range β cannot be received.

[0057] Light emitted from a display has orientation characteristics. If there is a portion (angle range) of the display's orientation characteristics that differs from the Lambertsian distribution used during calibration, and that angle range falls within the angle range β where light cannot be received, then brightness cannot be measured correctly.

[0058] Typically, when using a photometric colorimeter, calibration is performed before the actual measurement. Specifically, calibration is performed using a display with a distribution close to the Lambertian distribution as shown in Figure 13, and then the actual measurement is performed. Figure 15 is an explanatory diagram of the Lambertian distribution. If the infinitesimal area of ​​the light source surface is dA, the solid angle is dΩ, and the luminous intensity in the direction normal to the light source surface is IdΩdA, then the luminance (luminous intensity / infinitesimal area) is expressed as IdΩdA / dA = IdΩ. The luminous intensity of the Lambertian distribution changes in direct proportion to cos(θ) when the angle from the direction normal to the light source surface is θ, and the luminous intensity at angle θ is expressed as Icos(θ)dΩdA. The apparent infinitesimal area at this time is expressed as A・cos(θ), and the luminance (luminous intensity / apparent infinitesimal area) is expressed as Icos(θ)dΩdA / (A・cos(θ)) = IdΩ. In other words, in the Lambertian distribution, the luminance is uniform regardless of the angle of measurement relative to the light source surface.

[0059] As mentioned above, when using bundled fibers in which fiber strands are bundled together with adhesive, there is an angular range β in which light cannot be received. A photometric colorimeter with an angular range β in which light cannot be received is calibrated using a display with a distribution close to that of the Lambertsian distribution as shown in Figure 13, and the luminance measurement value at this time is set to 100, as shown in Figure 16. Next, as the main measurement, a display with a portion having orientation characteristics different from the Lambertsian distribution as shown in Figure 14 is measured. Note that in the display shown in Figure 14, the portion with orientation characteristics different from the Lambertsian distribution falls within the angular range β in which light cannot be received, and the other angular ranges are the same as the Lambertsian distribution used during calibration. In this case, it is not possible to capture the change in luminance due to the portion with different orientation characteristics, and the luminance measurement value is 100, the same as during calibration, as shown in Figure 17.

[0060] On the other hand, in this embodiment, there is no angular range β in which light cannot be received, or the angular range β is extremely small. A photometric colorimeter in which there is no angular range β in which light cannot be received is calibrated using a display with a distribution close to that of the Lambertsian distribution as shown in Figure 13, and the luminance measurement value at this time is set to 100, as shown in Figure 18. Next, as the actual measurement, a display with a portion having orientation characteristics different from the Lambertsian distribution as shown in Figure 14 is measured. In this embodiment, it is possible to capture the change in luminance due to the portion with different orientation characteristics, and as shown in Figure 19, the luminance measurement value is higher than the 100 at the time of calibration, for example, to 110. In other words, in this embodiment, luminance can be measured more accurately.

[0061] Figure 20 is an optical path diagram of light incident from the display surface of the display to the bundle fiber when the objective optical system is an imaging system. The view of the bundle fiber 70 from the incident surface 72 side is shown in Figure 12.

[0062] As shown in Figure 20, light emitted from the measurement area AR (area from point D to point G) on the display surface 12 of the display forms an image at the incident surface 72 of the bundle fiber 70 and is guided by the bundle fiber 70. However, of this light, light incident on area 83 where no fiber strands exist, i.e., light emitted from area AR1 (area from point E to point F), is not guided by the bundle fiber 70 and is not measured. In other words, in the imaging system, because there is an area 83 in the bundle fiber 70 where no fiber strands exist, light emitted from area AR1 cannot be received.

[0063] When measuring the display surface of a display, it is necessary to accurately measure within the measurement area AR. For example, even if a certain area within the measurement area AR exhibits characteristics, if that area falls within the area AR1 where light cannot be received, the brightness in the measurement area AR cannot be measured correctly.

[0064] Typically, when using a photometric colorimeter, calibration is performed before the actual measurement. Specifically, calibration is performed using a display with consistent brightness and no unevenness or gaps in the AR area under measurement, as shown in Figure 21, and then the actual measurement is performed. In Figure 21, the vertical axis represents the position on the display surface, and the horizontal axis represents brightness.

[0065] As mentioned above, when using bundled fibers in which fiber strands are bundled together with adhesive, there is a region AR1 in which light cannot be received. A photometric colorimeter with region AR1 in which light cannot be received is calibrated using a display with uniform brightness and no unevenness or gaps in the measurement region AR as shown in Figure 21, and the brightness measurement value at this time is set to 100 as shown in Figure 16. Next, as the main measurement, a display with brightness unevenness in region AR1 as shown in Figure 22 is measured. Note that in the display shown in Figure 22, the brightness in all regions other than region AR1 is the same as the display used during calibration, and the brightness in region AR1 is set to be lower than in the other regions. In this case, it is not possible to capture the brightness change due to brightness unevenness, and the brightness measurement value is 100, the same as during calibration, as shown in Figure 17.

[0066] On the other hand, in this embodiment, there is no region AR1 that cannot receive light, or the region AR1 is extremely small. A photometric colorimeter without a region AR1 that cannot receive light is calibrated using a display with uniform and constant brightness in the measurement region AR, as shown in Figure 21. As shown in Figure 18, the brightness measurement value at this time is set to 100. Next, as the actual measurement, a display having brightness uniformity in the region AR1, as shown in Figure 22, is measured. In this embodiment, it is possible to capture the brightness change due to brightness uniformity, and as shown in Figure 23, the brightness measurement value is lower than the calibration value of 100, for example, to 90. In other words, in this embodiment, brightness can be measured more accurately.

[0067] Each light-emitting dot on a display emits light in RED, GREEN, or BLUE, and these three dots form a single pixel. Gaps are provided between the light-emitting dots and between pixels, and these gaps do not emit light. In other words, the display surface of a display contains a mixture of areas that emit light and areas that do not.

[0068] Figure 24 shows an example of an image generated at the incident surface of a bundled fiber. Image 90 is generated when light emitted from the display surface of the display is imaged at the incident surface of the bundled fiber. In image 90, the red dot image 91, the green dot image 92, and the blue dot image 93 are images corresponding to light-emitting dots of each color. The fiber strands 94 are bundled together with adhesive, and regions 95 where no fiber strands exist are formed between the fiber strands 94.

[0069] In the case of bundled fibers, where fiber strands are bundled together with adhesive, the light of an image generated within the fiber strands 94 is guided, but the light of an image generated in the region 95 where no fiber strands exist is not guided. For example, when an image corresponding to the gaps between light-emitting dots and pixels (non-emitting areas) is generated in the region 95 where no fiber strands exist, the amount of light guided differs from when it is generated in the region 94 where fiber strands exist, making accurate measurement difficult. On the other hand, in this embodiment, since the region 95 where no fiber strands exist is less likely to form, accurate measurement is possible.

[0070] Furthermore, in the case of bundled fibers in which fiber strands are bound together with adhesive, the size and location of areas where fiber strands are absent vary from one bundled fiber to another. Therefore, variations in measurement results are likely to occur between individual photometric colorimeters. On the other hand, in this embodiment, areas where fiber strands are absent are less likely to form, thus reducing variations in measurement results between individual photometric colorimeters.

[0071] In this embodiment, the directional response (f2g) grade as defined in German industrial standard DIN 5032-7 can be improved. In German industrial standard DIN 5032-7, the directional response (f2g) item specifies the variation f2g of the received light intensity in the angular distribution of the received light intensity.

[0072] The variation f²g is a numerical value that indicates the variation in the received light intensity of light emitted from a point light source within a 90% range of the measurement angle. The point light source is a light source that occupies a 5% range of the measurement angle as viewed from the photometric colorimeter.

[0073] German industrial standard DIN 5032-7 defines the classes of photometric colorimeters that satisfy the following variability values ​​for f2g: f2g < 2%, f2g < 3%, and f2g < 6%, respectively as L class, A class, and B class.

[0074] The variation f2g can be measured by the following method. Figure 25 is an explanatory diagram of the method for measuring the variation f2g of the photometric colorimeter. Light 111 emitted from a point light source 110 is received by the photometric colorimeter 1, and the received light intensity of 111 is measured by the photometric colorimeter 1. The point light source 110 is a light source that occupies 5% of the measurement angle as viewed from the photometric colorimeter 1. By having the photometric colorimeter 1 measure the received light intensity while changing the receiving angle, the angular distribution of the received light intensity is obtained, and this variation is calculated. The receiving angle can be changed by rotating the photometric colorimeter 1 around the rotation axis 112. Here, "measurement angle" refers to the angular range (width) that can be measured by the photometric colorimeter 1. "Receiving angle" refers to the angle at which the photometric colorimeter 1 receives light, that is, the inclination angle of the received light with respect to the optical axis L1 shown in Figure 3.

[0075] Next, we will explain how, in bundled fibers, aligning the central axis of each fiber strand perpendicular to the output surface improves the accuracy of measurements in a photometric colorimeter.

[0076] In bundled fibers, where fiber strands are bound together with adhesive, there is some freedom in the position of the fiber strands before the adhesive hardens. Therefore, after hardening, the central axes of each fiber strand are not necessarily fixed in parallel. In other words, the central axis of each fiber strand is not necessarily perpendicular to the injection surface of the bundled fiber.

[0077] Figure 26 is a schematic diagram of the area near the injection surface of a bundled fiber, in which fiber strands are bundled together with adhesive. In Figure 26, the central axis S1 of the fiber strand 803 is perpendicular to the injection surface 74. On the other hand, the central axis S2 of the fiber strand 804 is not perpendicular to the injection surface 74, and the angle between axis S1, which is perpendicular to the injection surface 74, and axis S2 is represented by θ3.

[0078] In the fiber strand 803, when θ1 is the angle of light reflected between the core 85 and the cladding 86, and θ2 is the angle at which the reflected light is emitted from the emission surface 74, θ2 is expressed by the following equation (i), where n represents the refractive index of the fiber strand. Equation (i) θ2 = sin －１ (n × sinθ¹)

[0079] In the fiber strand 804, when θ1 is the angle of light reflected between the core 85 and the cladding 86, and θ4 is the angle at which the reflected light is emitted from the emission surface 74, θ4 is expressed by the following equation (ii). n represents the refractive index of the fiber strand. Equation (ii) θ4 = sin －１ {n×sin(θ1+θ3)}

[0080] In bundled fibers, where fiber strands are bonded together with adhesive, the angle θ3 differs for each fiber strand, resulting in variations in the angle θ4 of the light emitted from the emission surface 74. As a result, variations occur in the angle of light incident on the filter (not shown) of the photoelectric conversion unit. If the filter's spectral sensitivity characteristics depend on the incident angle, the degree of agreement of the color matching functions decreases, and the accuracy and precision of the measurement tend to decline. The same phenomenon occurs on the incident surface (not shown), resulting in variations in the angular range of light guided by each fiber strand.

[0081] In this embodiment, it is preferable that the injection ends are fused together. In this case, the central axes of each fiber strand are fixed so as to be parallel, and the central axis of each fiber strand is perpendicular to the injection surface of the bundle fiber. That is, the angle of the light emitted from the injection surface 74 is constant at θ2, and high accuracy and precision can be obtained in measurements.

[0082] Next, we will explain how reducing the diameter of the bundled fiber while keeping the diameter and number of fiber strands unchanged improves the accuracy of measurements in a photometric colorimeter.

[0083] When the diameter of the fiber strands and the number of strands bundled together are the same, a bundled fiber, in which the fiber strands are bundled with adhesive at the injection end, will have a larger diameter at the injection surface than the fused bundled fiber in this embodiment.

[0084] Figure 27 is a schematic diagram of a photoelectric conversion unit that receives light emitted from a bundle fiber, which is made by bundling fiber strands together with adhesive. Figure 28 is a schematic diagram of a photoelectric conversion unit that receives light emitted from a bundle fiber, which is made by bundling fiber strands together by fusion splicing. Since the angular range of light emitted from the emission surface 74 is approximately the same for both bundle fibers 70, the filter 61 and the light receiving sensor 62 become larger as the size of the emission surface 74 increases. In other words, in this embodiment, the diameter of the bundle fiber can be reduced (h2 < h1), so the light receiving sensor 62 can be reduced (k2 < k1). By reducing the size of the light receiving sensor 62, the capacitance of the input section for the amplification unit 26 is reduced, so the noise in the amplification unit 26 is reduced, and the S / N ratio (signal-to-noise ratio) can be improved.

[0085] As a way to make the light-receiving sensor 62 smaller, a focusing lens (not shown) may be provided between the exit surface 74 of the bundle fiber 70 and the filter 61. However, if the exit surface 74 is relatively large, a stronger power is required for the focusing lens, so the focusing lens tends to be larger, and the device tends to be relatively large. On the other hand, if the exit surface 74 is relatively small, a relatively strong power is not required for the focusing lens, so the focusing lens can be made smaller, and the device can also be made relatively small.

[0086] [Role of Bundle Fibers] The role of bundle fibers, that is, the effects obtained by using bundle fibers as light guides, will be explained.

[0087] As shown in Figure 3, the light emitted from the measurement area AR at angle α is incident on the upper end Fi1 of the light beam incident surface A of the optical fiber 55. In other words, the angle of the light emitted from the measurement area AR is related to the incident position on the incident surface of the bundle fiber.

[0088] However, in bundled fibers, as shown in Figure 5, multiple fiber strands bundled together at the incident surface 72 branch randomly at the branching section 76. Therefore, the exit position at the exit surface is random with respect to the incident position at the incident surface. In other words, in bundled fibers, random branching at the branching section 76 allows the light incident on the bundled fiber to be branched uniformly regardless of the angle. This reduces the influence of the angle of the light emitted from the measurement area AR on the measurement results.

[0089] Figure 29 is an explanatory diagram illustrating how light incident on a fiber optic wire is guided within the fiber optic wire. Light incident on the fiber optic wire 80 is repeatedly guided by total internal reflection between the core 85 and the cladding 86 due to the difference in refractive index. In other words, theoretically, light incident on the fiber optic wire 80 is emitted from the fiber optic wire 80 while maintaining its angle.

[0090] However, in reality, the fiber strand 80 has a certain length, and within that length, the reflected light is affected by local differences in refractive index (strain), local differences in diameter, and curvature of the reflective surface due to bending. Therefore, it is difficult for light incident on the fiber strand 80 to be emitted from the fiber strand 80 while maintaining its angle, and the light incident on the fiber strand 80 is emitted with changes in its incident position and incident angle. In particular, if the fiber strand 80 is of a predetermined length or longer, the incident light is emitted with a uniform incident position and incident angle, and the angular distribution of the emitted light approaches the numerical aperture NA inherent to the fiber strand 80. This reduces the influence of the angle of the light emitted from the measured area AR on the measurement results.

[0091] In this embodiment, the photometric colorimeter 1 comprises an objective optical system 21 that collects light from a target object, a light guide unit 24 that guides the light incident by the objective optical system 21, and a photoelectric conversion unit 25 that receives the light guided by the light guide unit 24 and converts it into an electrical signal. The light guide unit 24 comprises a bundle fiber 70 in which a plurality of fiber strands 80 are fused together at the incident end 71. This makes it possible to reduce the region 83 in which no fiber strands exist, thereby improving the accuracy of the measurement.

[0092] In this embodiment, the photometric colorimeter 1 includes an objective optical system 21 that collects light from a target object, a light guide unit 24 that guides the light incident by the objective optical system 21, and a photoelectric conversion unit 25 that receives the light guided by the light guide unit 24 and converts it into an electrical signal. The light guide unit 24 includes a bundle fiber 70 in which a plurality of fiber strands 80 are bundled together. At the cross-section of the incident end of the bundle fiber (incident surface 72), the distance between the centers of the geometric centers of each fiber strand 80 (distance between point C1 and point C2) is less than twice the radius r of the fiber strand 80. This makes the region 83 where no fiber strands exist smaller, and improves the accuracy of the measurement.

[0093] In this embodiment, the area of ​​the gap between each fiber strand 80 at the incident end 71 of the bundle fiber 70 (the region 83 where no fiber strands exist) is preferably 5% or less of the area of ​​the cross-section of the incident end (incident surface 72). This makes the region 83 where no fiber strands exist even smaller, improving the accuracy of the measurement.

[0094] In this embodiment, the bundle fiber 70 is preferably provided with branching sections 76 that branch into multiple branches on the output side, and the photoelectric conversion unit 25 receives the light branched at each branching section 76. This allows the photometric colorimeter 1 to measure not only luminance but also chromaticity.

[0095] In this embodiment, it is preferable that multiple fiber strands 80 are fused together at multiple injection ends 73 of the branching section 76. This improves the accuracy and precision of the measurement. In addition, the light receiving sensor 62 can be made smaller, and the signal-to-noise ratio can be improved.

[0096] In this embodiment, the cross-sectional shape of the multiple fused fiber strands 80 is preferably hexagonal. This further reduces the region 83 where no fiber strands are present, thereby improving the accuracy of the measurement.

[0097] In this embodiment, the light guide unit 24 is provided with a plurality of focusing lenses 56 on the exit side of the branching portion 76 of the bundle fiber 70, each focusing the light branched at the branching portion 76. The photoelectric conversion unit 25 preferably includes a plurality of filters 61 that transmit light in different wavelength ranges, and a plurality of light receiving sensors 62 that receive the light that has passed through the plurality of filters 61. This allows the photometric colorimeter 1 to measure not only luminance but also chromaticity. In addition, the light receiving sensors 62 can be made smaller, and the signal-to-noise ratio can be improved.

[0098] This disclosure makes it possible to improve the accuracy of measurements in a photometric colorimeter.

[0099] 1 Photometric colorimeter 12 Display surface 21 Objective optical system 24 Light guide unit 25 Photoelectric conversion unit 26 Amplification unit 31 A / D conversion unit 32 Memory unit 37 Power supply unit 38 Communication unit 55 Optical fiber 56p, 56q, 56r Focusing lens 61p, 61q, 61r Filter 62p, 62q, 62r Light receiving sensor 70 Bundle fiber 71 Incident end 72 Incident surface 73 Exit end 74 Exit surface 76 Branching section 80 Fiber strand

Claims

1. A photometric colorimeter comprising: an objective optical system for collecting light from a target object; a light guide unit for guiding the light incident by the objective optical system; and a photoelectric conversion unit for receiving the light guided by the light guide unit and converting it into an electrical signal, wherein the light guide unit comprises a bundle fiber in which a plurality of fiber strands are fused together at the incident end.

2. A photometric colorimeter comprising: an objective optical system for collecting light from an object; a light guide unit for guiding the light incident by the objective optical system; and a photoelectric conversion unit for receiving the light guided by the light guide unit and converting it into an electrical signal, wherein the light guide unit comprises a bundle fiber in which a plurality of fiber strands are bundled together, and in the cross-section of the incident end of the bundle fiber, the distance between the centers of the geometric centers of each fiber strand is less than twice the radius of the fiber strand.

3. The photometric colorimeter according to claim 2, wherein the area of ​​the gap between each fiber strand at the incident end of the bundle fiber is 5% or less of the area of ​​the cross-sectional area of ​​the incident end.

4. The photometric and colorimetric apparatus according to claim 1, wherein the bundle fiber is provided with a plurality of branching sections on the exit side, and the photoelectric conversion section receives the light branched at each of the branching sections.

5. The photometric and colorimetric apparatus according to claim 4, wherein the plurality of fiber strands are fused together at the plurality of injection ends of the branch section.

6. The photometric and colorimetric apparatus according to claim 1 or 5, wherein the cross-sectional shape of the plurality of fused fiber strands is hexagonal.

7. The photometric and colorimetric apparatus according to claim 5, wherein the light guide unit is provided with a plurality of focusing lenses on the exit side of the branching portion of the bundle fiber for focusing the light branched at the branching portion, and the photoelectric conversion unit is provided with a plurality of filters that transmit light in different wavelength ranges, and a plurality of light receiving sensors that receive the light that has passed through the plurality of filters.

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