Optical measuring apparatus and optical measuring method
The optical measuring apparatus adjusts imaging parameters to maintain a constant light-emitting region size, enhancing compatibility and flexibility in speckle or sparkle contrast measurements.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- DAI NIPPON PRINTING CO LTD
- Filing Date
- 2024-02-05
- Publication Date
- 2026-05-19
AI Technical Summary
Existing speckle contrast measuring instruments lack flexibility in adjusting imaging conditions to be compatible with other measuring instruments having different imaging conditions.
An optical measuring apparatus and method that adjusts the imaging distance, focal length, and F-number of the optical system to maintain a constant size of the light-emitting region, ensuring compatibility of speckle or sparkle contrast under varying conditions.
Improves the flexibility of imaging conditions for speckle or sparkle contrast measurements by maintaining consistent speckle or sparkle contrast across different imaging conditions.
Smart Images
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Figure 0007861344000019 
Figure 0007861344000020
Abstract
Description
[Technical Field]
[0001] This disclosure relates to an optical measuring device and an optical measuring method. [Background technology]
[0002] For example, as disclosed in Patent Document 1, speckle caused by the coherence of laser light is measured. The speckle contrast measuring instrument described in Patent Document 1 is configured to image the laser light that has been diffused by a moving diffuser plate and projected onto a screen, and to measure the speckle contrast based on the imaging results. [Prior art documents] [Patent Documents]
[0003] [Patent Document 1] Japanese Patent Publication No. 2014-32371 [Overview of the project] [Problems that the invention aims to solve]
[0004] However, the speckle contrast measuring instrument described in Patent Document 1 does not offer any effective suggestions for improving the flexibility of imaging conditions by ensuring compatibility of speckle contrast with other measuring instruments that have different imaging conditions.
[0005] This disclosure has been made in consideration of the above points, and aims to provide an optical measuring apparatus and optical measuring method that can improve the degree of freedom of imaging conditions for the surface to be measured for speckle contrast or sparkle contrast. [Means for solving the problem]
[0006] The optical measuring apparatus described herein is An optical system for imaging light emitted from the surface to be measured of an emissive electronic display or emissive surface to be measured for speckle contrast or sparkle contrast, A sensor having a two-dimensional sensor array surface on which the emitted light is imaged, and capturing the emitted light, The system includes a calculation unit that calculates the speckle contrast or sparkle contrast based on the emitted light captured under imaging conditions in which the size of the light-emitting region on the surface to be measured, which contributes to the imaging of the diffraction-limited spot of the emitted light on the surface of the two-dimensional sensor array, is constant. The size of the light-emitting region is determined based on the size of the diffraction-limited spot and the magnification of the optical system, which is determined from the focal length of the optical system and the imaging distance from the surface to be measured to the optical system.
[0007] In the optical measuring device according to this disclosure, The calculation unit may calculate a speckle contrast or sparkle contrast equivalent to the speckle contrast or sparkle contrast based on
[0008] In the optical measuring device according to this disclosure, The imaging distance in the second imaging condition may differ from that in the first imaging condition.
[0009] In the optical measuring device according to this disclosure, The second imaging condition may have a different focal length for the optical system compared to the first imaging condition.
[0010] In the optical measuring device according to this disclosure, The second imaging condition may have a different F-number for the optical system compared to the first imaging condition.
[0011] In the optical measuring device according to this disclosure, A mechanism for adjusting at least one of the imaging distance and the focal length of the optical system may be provided so that the size of the light emitting region satisfies the following formula and remains constant.
Equation
[0012] In the optical measurement device according to the present disclosure, A mechanism for adjusting at least one of the imaging distance, the focal length of the optical system, and the F-number of the optical system may be provided so that the size of the light emitting region satisfies the following formula and remains constant.
Equation
Equation
[0013] In the optical measuring device according to this disclosure, The system may further include a support member for supporting the object having the surface to be measured.
[0014] In the optical measuring device according to this disclosure, The calculation unit may calculate a speckle contrast or sparkle contrast equivalent to that of the first imaging condition based on the emitted light captured under the second imaging condition within the movable range of the imaging distance, which replaces the first imaging condition that exceeds the movable range of the imaging distance.
[0015] In the optical measuring device according to this disclosure, The optical system may include a first lens corresponding to the first imaging condition and a second lens corresponding to the second imaging condition.
[0016] The optical measuring apparatus described herein is The system may further include a mechanism for moving the optical system to set the first imaging conditions and the second imaging conditions, respectively.
[0017] In the optical measuring device according to this disclosure, The emitted light may be incoherent light or light obtained by diffusing coherent light.
[0018] The optical measurement method described herein is: A step of imaging the emitted light from the surface to be measured of an emissive electronic display or emissive surface to be measured for speckle contrast or sparkle contrast by forming an image of the emitted light on a two-dimensional sensor array surface using an optical system, The process includes a step of calculating the speckle contrast or sparkle contrast based on the captured emitted light, The calculation of the speckle contrast or sparkle contrast is performed based on the emitted light captured under imaging conditions in which the size of the light-emitting region on the surface to be measured that contributes to the imaging of the diffraction-limited spot of the emitted light on the two-dimensional sensor array surface is constant. The size of the light-emitting region is determined based on the size of the diffraction-limited spot and the magnification of the optical system, which is determined from the focal length of the optical system and the imaging distance from the surface to be measured to the optical system.
[0019] In the optical measurement method according to this disclosure, The step of imaging the emitted light is as follows: A step of determining imaging conditions such that the size of the light-emitting region on the surface to be measured remains constant, The process may include a step of adjusting the optical system to achieve the determined imaging conditions.
[0020] In the optical measurement method according to this disclosure, The surface to be measured may be the emission surface of the anti-glare layer in a display device having an anti-glare layer.
[0021] In the optical measurement method according to this disclosure, The surface to be measured may be the emission surface of the backlight device.
[0022] In the optical measurement method according to this disclosure, The surface to be measured may be the emission surface of a screen onto which light emitted from a projector is projected. [Effects of the Invention]
[0023] According to this disclosure, it is possible to improve the degree of freedom in imaging conditions of the surface to be measured for speckle contrast or sparkle contrast. [Brief explanation of the drawing]
[0024] [Figure 1] Figure 1 shows an example of an optical measuring device. [Figure 2]Figure 2 is an explanatory diagram illustrating the imaging conditions of the optical measuring device shown in Figure 1. [Figure 3] Figure 3 shows a specific example of the optical measuring device shown in Figure 1. [Figure 4] Figure 4 shows another specific example of the optical measuring device shown in Figure 1. [Figure 5] Figure 5 shows yet another specific example of the optical measuring device shown in Figure 1. [Figure 6] Figure 6 shows yet another specific example of the optical measuring device shown in Figure 1. [Figure 7] Figure 7 shows a speckle contrast measurement system using coherent light, as a reference example of the optical measurement apparatus shown in Figure 1. [Figure 8] Figure 8 shows the measurement results of speckle contrast using the measurement system shown in Figure 7. [Figure 9] Figure 9 shows an experimental example of the optical measurement apparatus shown in Figure 1, illustrating a speckle contrast measurement system using diffused coherent light. [Figure 10] Figure 10 shows the effective F-number and imaging distance as measurement conditions using the measurement system shown in Figure 9. [Figure 11] Figure 11 shows the measurement results of speckle contrast using the measurement system in Figure 9 under the measurement conditions in Figure 10. [Figure 12] Figure 12 shows the measurement results of speckle contrast using the measurement system in Figure 9 under different measurement conditions than those in Figure 10. [Figure 13] Figure 13 shows a modified example of the optical measuring device shown in Figure 1. [Figure 14] Figure 14 shows a modified example of the optical measurement method. [Figure 15] Figure 15 shows another variation of the optical measurement method. [Modes for carrying out the invention]
[0025] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that, for the sake of illustration and ease of understanding, the scale and aspect ratios of the drawings attached to this specification have been appropriately altered and exaggerated from those of the actual objects.
[0026] Furthermore, terms used in this specification to specify shapes, geometric conditions, and their degrees, such as "equivalent" and "identical," as well as values of length and angle, shall not be strictly interpreted, but shall be interpreted to include a range that allows for the expectation of similar functionality.
[0027] Figure 1 shows an example of the optical measuring device 1. Figure 2 is an explanatory diagram for explaining the imaging conditions of the optical measuring device 1 in Figure 1. Figure 3 shows a specific example of the optical measuring device 1 in Figure 1. Figure 4 shows another specific example of the optical measuring device 1 in Figure 1. Figure 5 shows yet another specific example of the optical measuring device 1 in Figure 1. Figure 6 shows yet another specific example of the optical measuring device 1 in Figure 1.
[0028] The optical measuring device 1 shown in Figure 1 can be used to measure the speckle contrast or sparkle contrast contained in the optical image formed on the surface to be measured 7 of an emissive electronic display or emissive surface. Hereinafter, the surface to be measured 7 of the emissive electronic display or emissive surface may be simply referred to as the surface to be measured 7.
[0029] Generally, speckle refers to irregular spatial modulation images resulting from the interference of coherent light on the sensor surface of the observer's visual system. Speckle contrast is a representative evaluation index for monochromatic speckle and is defined by the following formula.
[0030]
number
[0031] In contrast, the speckles measured in this disclosure are spatially modulated images based on coherent light with reduced coherence due to diffusion, and the speckle contrast of these speckles can be defined as the ratio of the standard deviation to the mean value of the speckle pattern, similar to equation (4).
[0032] Furthermore, sparkle refers to the irregular spatial modulation image that results from the imaging of the observer's visual system onto the sensor surface due to the combination of the pixel matrix of a direct-view display and a diffusion layer placed near the surface of the display. Sparkle contrast is a representative evaluation index of sparkle and can be defined as the ratio of the standard deviation to the mean value of the sparkle pattern, similar to equation (4).
[0033] In the example shown in Figure 1, the surface to be measured 7 is the surface of the anti-glare layer 9, or diffusion layer, laminated on the display device 8 having a pixel matrix 81 and a black matrix 82. Therefore, in the example shown in Figure 1, the optical measuring device 1 can measure the sparkle contrast of the surface to be measured 7. The display device 8 is typically a liquid crystal display device comprising a liquid crystal panel having a pixel matrix 81 and a black matrix 82, and a backlight device (not shown) installed on the back of the liquid crystal panel. The backlight device may be an edge-lit type that guides light emitted from a light source placed on the side of the light guide plate to the liquid crystal panel side by internal reflection within the light guide plate, or it may be a direct-lit type in which multiple light sources are evenly arranged directly beneath the liquid crystal panel. As a light source for the edge-lit type, for example, a cold cathode fluorescent lamp or a light-emitting diode (LED) that emits incoherent light can be used. As a light source for the direct-lit type, for example, a light-emitting diode can be used.
[0034] However, the display device is not limited to liquid crystal displays; for example, it may be an organic EL display or a quantum dot (QD) display. Alternatively, the display device may be configured using a screen 15 and a projector 16, as described later.
[0035] As a specific configuration for measuring sparkle contrast, in the example shown in Figure 1, the optical measuring device 1 comprises an optical system 3, a two-dimensional sensor array 4, an imaging condition setting unit 5, and a calculation unit 6. The components of this optical measuring device 1 will be described in detail below.
[0036] (Optical system 3) The optical system 3 includes a lens 31 and an aperture 32 provided with an aperture 321.
[0037] The optical system 3 refracts the light L emitted from the surface 7 of the sparkle contrast sensor to form an image on the two-dimensional sensor array surface 41 of the two-dimensional sensor array 4.
[0038] The parameters of optical system 3 affect the magnitude of the sparkle contrast.
[0039] For example, the smaller the aperture 321 of the aperture 32, that is, the larger the F-number of the lens 31, the more pronounced the diffraction effect on the emitted light L at the aperture 321 of the aperture 32 becomes. This increased diffraction of the emitted light L leads to a larger spread of the diffraction-limited spot, or Airy disk, of the emitted light L imaged on the two-dimensional sensor array surface 41. As a result, the diffraction-limited spot extends not only to one pixel 42 of the two-dimensional sensor array 4, but also to other adjacent pixels 42.
[0040] This diffusion-limiting spot spread occurs at each diffraction-limiting spot imaged on each pixel 42 of the two-dimensional sensor array 4. When focusing on a specific pixel 42, the sparkle pattern is averaged because the emitted light L that has passed through different parts of the anti-glare layer 9 overlaps on that specific pixel 42. Similarly, as with the sparkle, the same averaging occurs in speckle contrast measured under conditions where temporal coherence is reduced by a rotating diffuser or the like.
[0041] The greater the degree of averaging of the speckle and sparkle patterns on the pixels 42, the lower the speckle contrast and sparkle contrast become. In other words, the larger the F-number of the lens 31, the lower the speckle contrast and sparkle contrast become due to the averaging effect on the pixels 42.
[0042] On the other hand, if the F-number becomes too small, the average particle size constituting the speckle or sparkle pattern formed on the two-dimensional sensor array surface 41 becomes smaller than that of the pixels 42, which also reduces the speckle contrast and sparkle contrast. This is because the diffraction-limited spot spread is too narrow relative to the pixels 42, resulting in a distribution of light reception within a single pixel 42, and this distribution causes the speckle or sparkle pattern to be averaged within that single pixel 42. In other words, if the F-number of the lens 31 becomes too small, the averaging effect within the pixels 42 reduces the speckle contrast and sparkle contrast.
[0043] As described above, the F-number of lens 31 affects speckle contrast and sparkle contrast. A decrease in contrast occurs due to the averaging effect caused by the overlapping of different patterns on pixels 42 as the F-number increases, and a decrease in speckle or sparkle contrast also occurs due to the averaging effect within pixels 42 as the F-number decreases.
[0044] In the example shown in Figure 1, the optical system 3 has one lens 31, but the optical system 3 may have multiple lenses. In this case, the multiple lenses may have a power combination suitable for reducing the aberration of the emitted light L. The optical system 3 may also include optical filters 33. Specifically, these may be Y filters, XYZ filters, RGB filters, linear polarizing filters, circular polarizing filters, ND filters, etc. For example, Figure 1 shows an example in which an optical filter 33 is placed between the aperture 32 and the lens 31, but the number and position of the optical filters 33 are not limited to the example in Figure 1.
[0045] (2D sensor array 4) The two-dimensional sensor array 4 has a two-dimensional sensor array surface 41 on which the light L emitted from the surface to be measured 7 is imaged, and it captures the emitted light L.
[0046] The two-dimensional sensor array 4 has multiple adjacent pixels 42, and the surfaces of the pixels 42 constitute the two-dimensional sensor array surface 41. The emitted light L received by the pixels 42 is converted into an electrical signal by photoelectric conversion, and the converted electrical signal is used to calculate speckle contrast or sparkle contrast.
[0047] The two-dimensional sensor array 4 is an image sensor having a solid-state image element, and may be, for example, a CCD (Charge Coupled Device) sensor or a CMOS sensor.
[0048] (Imaging condition setting unit 5) The imaging condition setting unit 5 sets the imaging conditions for the surface to be measured 7, i.e., the imaging conditions for the emitted light L, to the optical measuring device 1. The imaging condition setting unit 5 may also have a mechanism for moving, i.e., adjusting, the optical system 3 in order to set the imaging conditions for the surface to be measured 7.
[0049] For example, as shown in Figure 3, the imaging condition setting unit 5 may include a lens exchange mechanism 51 that selectively moves a plurality of lenses 31A, 31B with different focal lengths onto the optical axis OA, and a control unit 50 that controls the operation of the lens exchange mechanism 51. In the example shown in Figure 3, there are two lenses, but the lens exchange mechanism 51 may exchange three or more lenses. The specific form of the lens exchange mechanism 51 is not particularly limited, and for example, the lens exchange mechanism 51 may be configured by an actuator having a power source such as a motor. According to the example shown in Figure 3, the imaging condition setting unit 5 can set or change the magnification of the optical system 3 as an imaging condition.
[0050] Furthermore, as shown in Figure 4, for example, the imaging condition setting unit 5 may include an imaging distance adjustment mechanism 52 that adjusts the imaging distance d by moving the optical system 3 in the optical axis direction D1, and a control unit 50 that controls the operation of the imaging distance adjustment mechanism 52. The specific form of the imaging distance adjustment mechanism 52 is not particularly limited, and for example, the imaging distance adjustment mechanism 52 may be configured by an actuator having a power source such as a motor. According to the example shown in Figure 4, the imaging condition setting unit 5 can set or change the imaging distance d from the surface to be measured 7 to the optical system 3 as an imaging condition.
[0051] Furthermore, as shown in Figure 5, for example, the imaging condition setting unit 5 may have an aperture adjustment mechanism 53 for adjusting the size of the aperture 321 of the diaphragm 3. The aperture adjustment mechanism 53 can be configured by an actuator such as a motor. According to the example shown in Figure 5, the imaging condition setting unit 5 can set or change the F-number of the optical system 3 as an imaging condition.
[0052] Furthermore, as shown in Figure 6, the imaging condition setting unit 5 may have all of the multiple mechanisms 51, 52, and 53 that move the optical system 3 shown in Figures 3 to 5.
[0053] Furthermore, the imaging condition setting unit 5 may also be able to change the size of the pixels 42 of the two-dimensional sensor array 4 as an imaging condition.
[0054] With the above configuration, the imaging condition setting unit 5 sets imaging conditions such that the size of the light-emitting region on the surface to be measured 7 that contributes to imaging the diffraction-limited spot of the emitted light L on the two-dimensional sensor array surface 41 remains constant, in order to ensure compatibility of speckle contrast or sparkle contrast based on emitted light L captured under different imaging conditions.
[0055] For example, the control unit 50 may pre-store, or determine, a second imaging condition for which the size of the light-emitting region on the surface to be measured 7 that contributes to imaging the diffraction-limited spot of the emitted light L onto the two-dimensional sensor array surface 41 is constant, i.e., the same, for the first imaging condition, and then control the operation of mechanisms 51, 52, and 53, i.e., adjust the optical system 3, to set the stored second imaging condition. Such a control unit 50 can be composed of hardware such as a CPU and memory. Part of the control unit 50 may also be composed of software.
[0056] The detailed significance of the imaging conditions under which the size of the light-emitting region on the surface to be measured 7, which contributes to the imaging of the diffraction-limited spot of the emitted light L on the two-dimensional sensor array surface 41, remains constant will be described later.
[0057] (Calculation section 6) The calculation unit 6 calculates speckle contrast or sparkle contrast based on the emitted light L imaged under imaging conditions in which the size of the light-emitting region on the surface under measurement 7 that contributes to the imaging of the diffraction-limited spot of the emitted light L onto the two-dimensional sensor array surface 41 is constant. More specifically, the calculation unit 6 calculates speckle contrast or sparkle contrast based on the emitted light L imaged under a second imaging condition in which the size of the light-emitting region on the surface under measurement 7 that contributes to the imaging of the diffraction-limited spot of the emitted light L onto the two-dimensional sensor array surface 41 is constant compared to the first imaging condition. The calculation unit 6 outputs the calculated speckle contrast or sparkle contrast. The output destination of the calculated speckle contrast or sparkle contrast may be a memory that stores the calculation results, or a display that shows the calculation results. The calculation unit 6 is composed of hardware such as a CPU and memory. Part of the calculation unit 6 may be composed of software.
[0058] The following explains in detail the significance of imaging conditions under which the size of the light-emitting region on the surface to be measured 7, which contributes to the imaging of the diffraction-limited spot of the emitted light L on the two-dimensional sensor array surface 41, remains constant.
[0059] The size of the light-emitting region on the measurement surface 7 that contributes to the imaging of the diffraction-limited spot of the emitted light L onto the two-dimensional sensor array surface 41 is determined as follows based on the size of the diffraction-limited spot, the magnification of the optical system 3, which is obtained from the focal length of the optical system 3 and the imaging distance d from the measurement surface 7 to the optical system 3.
[0060]
Equation
[0061] Here, as shown in FIG. 2, on the two-dimensional sensor array surface 41, the emitted light L from the measurement surface 7 is imaged as a diffraction-limited spot PS, that is, a point image, that straddles a plurality of pixels 42 according to the PSF (point spread function). In FIG. 2, for the sake of explaining the spread of the diffraction-limited spot PS according to the PSF, the two-dimensional sensor array 4 is illustrated in an enlarged manner compared to FIG. 1.
[0062] Thus, since the diffraction-limited spot PS centered on one pixel 42 is received not only by that pixel 42 but also by other adjacent pixels 42, it can be considered that the image of the diffraction-limited spot PS on one pixel 42 is contributed to by the emitted light L from multiple light-emitting points P on the surface under measurement 7.
[0063] Furthermore, the light-emitting region on the surface under measurement 7 that contributes to the imaging of the diffraction-limited spot PS of the emitted light L onto the two-dimensional sensor array surface 41 can be considered as a collection of multiple light-emitting points P. Therefore, the size of the light-emitting region can be considered as the size S of the image projected onto the surface under measurement 7 from the diffraction-limited spot PS on the two-dimensional sensor array 4 side through the optical system 3, as shown in Figure 2. Note that in Figure 2, the projected image of the diffraction-limited spot PS onto the surface under measurement 7 is represented as the projected image of the PSF. In the example shown in Figure 2, the projected image of the diffraction-limited spot PS onto the surface under measurement 7 is larger than the diffraction-limited spot PS, which is due to the magnification of the optical system 3.
[0064] In this disclosure, we have found that if the size S of the light-emitting region on the surface under measurement 7 that contributes to imaging of such diffraction-limited spots PS is constant, then compatibility of speckle contrast or sparkle contrast based on emitted light L imaged under different imaging conditions can be ensured. The reason why this compatibility can be ensured is as follows.
[0065] If the emitted light L from each light-emitting point P on the surface under measurement 7 that is incident on the pixel 42 is incoherent or, even if coherent, its coherence is reduced by diffusion, then on the pixel 42, the emitted light L from each light-emitting point P on the surface under measurement 7 hardly interferes, and a simple superposition of light wavefronts occurs.
[0066] As a result, a group of diffraction-limited spots is formed in which speckles or sparkles are averaged, depending on the number of light-emitting points P on the surface 7 being measured corresponding to the pixels 42. The degree of this averaging of speckles or sparkles depends on the number of light-emitting points P on the surface 7 being measured corresponding to the pixels 42, i.e., the size S of the light-emitting region on the surface 7 being measured.
[0067] Therefore, by keeping the size S of the light-emitting region on the surface to be measured 7 constant, even if the imaging conditions are different, it is possible to obtain almost identical speckle contrast or sparkle contrast with a common degree of speckle or sparkle averaging.
[0068] For the reasons stated above, compatibility between speckle contrast and sparkle contrast can be ensured. Therefore, the imaging condition setting unit 5 sets imaging conditions such that S is constant, and the calculation unit 6 calculates speckle contrast or sparkle contrast based on the emitted light L captured under imaging conditions such that S is constant. In other words, the imaging condition setting unit 5 adjusts at least one of the imaging distance d and the focal length f of the optical system 3 so that S is constant, and the calculation unit 6 calculates speckle contrast or sparkle contrast based on the emitted light L captured under imaging conditions set by the adjustment.
[0069] With this configuration, interchangeable speckle contrast or sparkle contrast can be obtained based on the emitted light L captured under different imaging conditions, thereby improving the flexibility of imaging conditions.
[0070] More specifically, the calculation unit 6 can calculate a speckle contrast or sparkle contrast equivalent to that based on the emitted light L captured under the first imaging condition, based on the emitted light L captured under the second imaging condition, which has the same size S of the light-emitting region as the first imaging condition.
[0071] The first imaging conditions may be within the movable range of the imaging distance of the optical measuring device 1, or they may be beyond the movable range of the imaging distance of the optical measuring device 1.
[0072] If the first imaging condition exceeds the movable range of the imaging distance of the optical measuring device 1, the speckle contrast or sparkle contrast that would be obtained if the first imaging condition were set can be calculated based on the emitted light L captured under the second imaging condition, which is within the movable range of the imaging distance of the optical measuring device 1. This makes it possible to alleviate the structural constraints of the optical measuring device 1 on the measurement of speckle contrast or sparkle contrast.
[0073] If the first imaging condition falls within the movable range of the imaging distance of the optical measuring device 1, by selectively setting both the first and second imaging conditions, the speckle contrast or sparkle contrast measured under the first imaging condition and the speckle contrast or sparkle contrast measured under the second imaging condition can be appropriately compared using only one optical measuring device 1.
[0074] The second imaging condition may have a different imaging distance d compared to the first imaging condition. In this case, as shown in Figure 4, the imaging condition setting unit 5 can set the second imaging condition or both the second and first imaging conditions by adjusting the imaging distance d by moving the optical system 3 in the direction of the optical axis OA using the imaging distance adjustment mechanism 52.
[0075] Furthermore, the focal length of the optical system 3 may differ from that of the first imaging condition for the second imaging condition. In this case, the imaging condition setting unit 5 can set the second imaging condition or both the second and first imaging conditions by exchanging the lenses 31A and 31B used for imaging using the lens exchange mechanism 51, as shown in Figure 3. In this case, lens 31A may function as the first lens corresponding to the first imaging condition, and lens 31B may function as the second lens corresponding to the second imaging condition.
[0076] Furthermore, the second imaging condition may have a different F-number for the optical system 3 compared to the first imaging condition. In this case, as shown in Figure 5, the imaging condition setting unit 5 can set the second imaging condition or both the second and first imaging conditions by adjusting the size of the aperture 321 of the aperture 53 using the aperture adjustment mechanism 53.
[0077] However, if the F-number differs between the first imaging conditions and the second imaging conditions, the calculation unit 6 calculates the speckle contrast or sparkle contrast based on the emitted light L captured under imaging conditions where the size S of the light-emitting region satisfying the following equation remains constant. That is, the imaging condition setting unit 5 adjusts the F-number of the optical system 3 and, if necessary, the imaging distance d and the focal length f of the optical system 3 so that S in the following equation remains constant, and the calculation unit 6 calculates the speckle contrast or sparkle contrast based on the emitted light L captured under imaging conditions set by the adjustment.
[0078]
number
number
[0079] By calculating the speckle contrast or sparkle contrast based on the emitted light L captured under imaging conditions where S shown in equation (2) is constant, equivalent speckle contrast or sparkle contrast can be obtained even when the F-number of the optical system 3 is different as an imaging condition.
[0080] Next, we will describe experimental examples to demonstrate the effectiveness of the optical measuring device 1 configured as described above. Before describing the experimental examples, we will first describe, as a reference example, an example of measuring speckle contrast using perfectly coherent light that is not diffused.
[0081] (Reference example) Figure 7 shows a measurement system for speckle contrast using coherent light with extremely high temporal and spatial coherence.
[0082] The measurement system shown in Figure 7 consists of a He-Ne laser 11 that emits laser light with a wavelength of 543.7 nm as coherent light, a spatial filter 12 having a lens and a pinhole, a screen 80, and an imaging camera 10.
[0083] A diffuse reflection target, model SRT-99-050, manufactured by Labsphere, was used as screen 80. As shown in Figure 7, screen 80 was positioned 1.2 m away from the He-Ne laser 11 so that the incident angle of the laser light was 30°. For the imaging camera 10, a lens with a CCD pixel size of 6.45 μm and a focal length of 50 mm was selected. The imaging distance d from screen 80 to imaging camera 10 was fixed at 0.4 m.
[0084] In the measurement system shown in Figure 7, the laser light emitted from the He-Ne laser 11 is adjusted in the spatial filter 12 to become a near-ideal spherical wave, and then irradiated onto the screen 80, where it is diffusely reflected. The diffusely reflected laser light is received by the imaging camera 10, and the speckle contrast is measured.
[0085] In the measurement example shown in Figure 7, the speckle contrast was measured for each effective F-number while varying the effective F-number of the optical system of the imaging camera 10 from 3.2 to 42. The measured speckle contrast values obtained were then compared with the calculated speckle contrast values described below.
[0086] The calculated speckle contrast is a value calculated based on the following theory. As shown in Figure 7, when using perfectly coherent light that is not diffused, the speckle contrast has little dependence on the effective F-number of the imaging camera 10. This is because when using coherent light with extremely high temporal and spatial coherence, the coherent region on the imaging camera 10 becomes very large. On the other hand, the average speckle size R, which is almost equivalent to the diffraction-limited spot size R described above, depends on the effective F-number of the imaging camera 10, as shown in the following equation.
[0087]
number
[0088] The speckles are integrated across multiple finite areas of the sensor of the imaging camera 10. The speckle contrast of these integrated speckles is defined by the following equation.
[0089]
number
[0090] Figure 8 compares the calculated speckle contrast value obtained according to formula (6) with the measured speckle contrast value obtained using the measurement system in Figure 7. In Figure 8, the measured and calculated values are normalized to a value of 1 for an effective F number of 42.
[0091] As shown in Figure 8, the measured speckle contrast values are consistent with the calculated values.
[0092] As shown in Figure 8, even when using coherent light with extremely high temporal and spatial coherence, where the dependence of speckle contrast on the effective F-number is low (spatial superposition of speckle pattern intensities does not occur), the speckle contrast does not remain constant with respect to changes in the effective F-number, and it was confirmed that the speckle contrast decreases as the effective F-number decreases. In other words, as shown in Figure 8, it was demonstrated that the speckle contrast decreases due to the averaging effect within the pixel.
[0093] (Example of experiment) Next, as an experimental example of the optical measurement device 1 shown in Figure 1, we will describe an example of measuring speckle contrast using diffused coherent light. Figure 9 shows a measurement system for speckle contrast using coherent light whose diffusion state is changed over time.
[0094] The measurement system shown in Figure 9 consists of an SHG laser 111 that emits laser light with a wavelength of 533 nm as coherent light, a rotating diffuser 13, a screen 80, and an imaging camera 10.
[0095] The rotating diffuser 13 diffuses the laser light emitted from the SHG laser 111 to reduce coherence. The laser light diffused by the rotating diffuser 13 as a spot beam with a diameter of approximately 1 cm is projected onto a screen 80 located 1.2 m away from the rotating diffuser 13. The screen 80 diffusely reflects the diffused light projected from the rotating diffuser 13 towards the imaging camera 10. The diffusely reflected light is received by the imaging camera 10 and the speckle contrast is measured.
[0096] When the rotating diffuser 13 is used in this way, an averaging effect occurs on the sensor due to the superposition of different speckle pattern intensities. In this case, the speckle contrast is defined by the following equation.
[0097]
number
[0098] To obtain such measured speckle contrast values, in the experimental example, first, as a first measurement under imaging conditions according to the above formula (1), the effective F number F# was set so that S remained constant according to Figure 10. image The combination of the focal length and imaging distance d was varied, and the speckle contrast based on the laser light captured under the imaging conditions for each combination was measured. In the first measurement, the focal length f of the lens of the imaging camera 10 was kept constant.
[0099] Figure 11 shows the measurement results of the speckle contrast obtained from the first measurement. Specifically, the measured values shown as rectangular plots in Figure 11 are the measured values from the first measurement. In addition to the measured values from the first measurement, Figure 11 also shows the measured and calculated values when using coherent light with extremely high temporal and spatial coherence as shown in Figure 8.
[0100] As shown in Figure 11, it was confirmed that when measuring speckle contrast using diffused coherent light under imaging conditions where S is constant, the same measurement results as when using coherent light with extremely high temporal and spatial coherence can be obtained. This is equivalent to demonstrating that, assuming the reduction in speckle contrast due to the averaging effect within pixels is eliminated, the speckle contrast is constant when S is constant.
[0101] Next, in the experimental example, a second measurement was performed under imaging conditions according to equation (1), measuring the speckle contrast using two lenses with different focal lengths. The focal lengths f of the two lenses were 35 mm and 50 mm, respectively. The imaging distance d corresponding to the lens with a focal length of f = 35 mm was set to 0.42 mm, and the imaging distance d corresponding to the lens with a focal length of f = 50 mm was set to 0.62 m. In other words, in the second measurement, S was kept constant by keeping d / f in equation (1) constant. In the second measurement, the CCD pixel size of the imaging camera 10 was set to 9 μm.
[0102] Figure 12 shows the results of the second measurement. As shown in Figure 12, it was confirmed that even with different imaging conditions, the speckle contrast was almost identical if S was constant.
[0103] The above experimental examples demonstrate the effectiveness of optical measuring device 1 in obtaining equivalent speckle contrast by keeping S constant.
[0104] Although one embodiment has been described with several specific examples, the above-described examples are not intended to limit this embodiment. The above-described embodiment can be implemented with various other examples, and various configurations can be omitted, replaced, modified, or further configurations added without departing from its essence.
[0105] The embodiments described above will be further explained below by describing other specific examples with reference to the drawings. In the following description and the drawings used therein, parts that can be configured in the same way as in the specific examples described above will be given the same reference numerals as those used for the corresponding parts in the specific examples described above, and redundant explanations will be omitted.
[0106] (First variation) Figure 13 shows a modified version of the optical measuring device 1 of Figure 1, as a first modified example. In the example shown in Figure 13, the main body of the optical measuring device 1, which consists of an optical system 3, a two-dimensional sensor array 4, an imaging condition setting unit 5, and a calculation unit 6, is housed in a housing 101. The optical measuring device 1 further has a support member 102 extending from the housing 101 toward the display device 8. The support member 102 supports the anti-glare layer 9 and the display device 8, which are objects having the surface to be measured 7, while ensuring a certain imaging distance between the surface to be measured 7, which is the surface of the anti-glare layer 9, and the optical system 3. In the example shown in Figure 13, the support member 102 supports the display device 8 and the anti-glare layer 9 by fitting into a part of the display device 8 and the anti-glare layer 9, but the form of the support member 102 is not limited to that shown in Figure 13.
[0107] As shown in Figure 13, when the display device 8 and the anti-glare layer 9 are supported by the support member 102, the imaging distance d between the surface to be measured 7 and the optical system 3 is naturally constrained.
[0108] However, by setting imaging conditions other than the imaging distance d so that S in equation (1) remains constant, it is possible to measure a speckle contrast or sparkle contrast equivalent to that based on the emitted light L imaged at an imaging distance d that cannot be achieved with the optical measuring device 1 in Figure 13 (for example, an imaging distance exceeding the dimensions of the support member 102).
[0109] (Second variation) Up to this point, we have described an example in which the surface to be measured 7 is the surface of the anti-glare layer 9 laminated on the display device 8. In contrast, as shown in Figure 14, the surface to be measured 7 may be the emission surface of the backlight device 14. In the example shown in Figure 14, the backlight device 14 consists of a light source 141, a light guide plate 142 that guides the light emitted from the light source 141, a reflector plate 143 laminated on the back of the light guide plate 142, and a diffuser plate 144 laminated on the front of the light guide plate 142. The surface to be measured 7 is the surface of the diffuser plate 144. In the example shown in Figure 14, the backlight device is an edge-lit type, but the optical measuring device 1 may measure the speckle contrast or sparkle contrast of a direct-lit type backlight device.
[0110] (Third variation) Furthermore, as shown in Figure 15, the surface to be measured 7 may also be the output surface of the screen 15. In the example shown in Figure 15, the screen 15 is a device that transmits and displays coherent light projected from the projector 16 as an image. Note that when measuring such projection light, speckle occurs but sparkle does not. As mentioned above, the target of sparkle contrast measurement is limited to direct-view displays with an anti-glare layer.
[0111] In addition, while numerous modifications applicable to the embodiments described above have been explained, it is naturally possible to combine and apply multiple modifications as appropriate. [Explanation of symbols]
[0112] 1 Optical measurement device 7 Surface to be measured 4. Two-dimensional sensor array 41 Two-dimensional sensor array surface 6. Calculation Section
Claims
1. An optical system for imaging the light emitted from the surface to be measured of a light-emitting electronic display or light-emitting surface that is the target of measuring sparkle contrast, A two-dimensional sensor array having a two-dimensional sensor array surface on which the emitted light is imaged, and a two-dimensional sensor array that captures the emitted light, The system includes a calculation unit that calculates the sparkle contrast based on the emitted light captured under imaging conditions in which the size of the light-emitting region on the surface to be measured, which contributes to the imaging of the diffraction-limited spot of the emitted light on the surface of the two-dimensional sensor array, is constant. The size of the light-emitting region is determined based on the size of the diffraction-limited spot, the focal length of the optical system, and the magnification of the optical system, which is determined from the imaging distance from the surface to be measured to the optical system. An optical measuring device comprising a mechanism for adjusting at least one of the imaging distance and the focal length of the optical system such that the size of the light-emitting region satisfying the following formula remains constant. [Math 1] however, S: Size of the light-emitting region R: Size of the diffraction-limited spot m: Magnification of the optical system F# ｉｍａｇｅ : F-number of the optical system on the image side d: The imaging distance f: Focal length of the optical system F# ｓｕｒｆａｃｅ : F number of the optical system on the surface to be measured
2. An optical system for imaging the light emitted from the surface to be measured of a light-emitting electronic display or light-emitting surface that is the target of measuring sparkle contrast, A two-dimensional sensor array having a two-dimensional sensor array surface on which the emitted light is imaged, and a two-dimensional sensor array that captures the emitted light, The system includes a calculation unit that calculates the sparkle contrast based on the emitted light captured under imaging conditions in which the size of the light-emitting region on the surface to be measured, which contributes to the imaging of the diffraction-limited spot of the emitted light on the surface of the two-dimensional sensor array, is constant. The size of the light-emitting region is determined based on the size of the diffraction-limited spot, the focal length of the optical system, and the magnification of the optical system, which is determined from the imaging distance from the surface to be measured to the optical system. An optical measuring device comprising a mechanism for adjusting the imaging distance, the focal length of the optical system, and at least one of the F-number of the optical system such that the size of the light-emitting region satisfying the following formula remains constant. [Math 2] [Math 3] however, M: Integration parameter S: Size of the light-emitting region R: Size of the diffraction-limited spot m: Magnification of the optical system F# ｉｍａｇｅ : F-number of the optical system on the image side d: The imaging distance f: Focal length of the optical system F# ｓｕｒｆａｃｅ : F number of the optical system on the surface to be measured A Ｃ : The size of the coherent region on the surface of the two-dimensional sensor array. A ｍ : The size of the uniform square detection element on the two-dimensional sensor array surface erf: Standard error function
3. The optical measuring apparatus according to claim 1 or 2, wherein the calculation unit calculates a sparkle contrast equivalent to that based on the emitted light captured under the first imaging condition, based on the emitted light captured under a second imaging condition in which the size of the light-emitting region is the same as that of the first imaging condition.
4. The optical measuring apparatus according to claim 3, wherein the second imaging condition is different from the first imaging condition in terms of the imaging distance.
5. The optical measuring apparatus according to claim 3 or 4, wherein the second imaging condition is different in focal length from that of the first imaging condition.
6. The optical measuring apparatus according to any one of claims 3 to 5, wherein the second imaging condition is different from the F-number of the optical system with respect to the first imaging condition.
7. The optical measuring apparatus according to any one of claims 1 to 6, further comprising a support member for supporting an object having the surface to be measured.
8. The optical measuring apparatus according to claim 3, wherein the calculation unit calculates a sparkle contrast equivalent to that of the first imaging condition based on the emitted light captured under the second imaging condition within the movable range of the imaging distance, which replaces the first imaging condition that exceeds the movable range of the imaging distance.
9. The optical measuring apparatus according to any one of claims 3 to 6 and 8, wherein the optical system comprises a first lens corresponding to the first imaging condition and a second lens corresponding to the second imaging condition.
10. The optical measuring apparatus according to any one of claims 3 to 6, 8, and 9, further comprising a mechanism for moving the optical system to set the first imaging condition and the second imaging condition, respectively.
11. The optical measuring apparatus according to any one of claims 1 to 10, wherein the emitted light is incoherent light or light obtained by diffusing coherent light.
12. A step of imaging the emitted light from the surface to be measured of an emissive electronic display or emissive surface to be measured for sparkle contrast by forming an image of the emitted light on a two-dimensional sensor array surface using an optical system, The process includes a step of calculating the sparkle contrast based on the captured emitted light, The calculation of the sparkle contrast is performed based on the emitted light captured under imaging conditions in which the size of the light-emitting region on the surface to be measured, which contributes to the imaging of the diffraction-limited spot of the emitted light on the two-dimensional sensor array surface, is constant. The size of the light-emitting region is determined based on the size of the diffraction-limited spot, the focal length of the optical system, and the magnification of the optical system, which is determined from the imaging distance from the surface to be measured to the optical system. An optical measurement method comprising the step of adjusting at least one of the imaging distance and the focal length of the optical system such that the size of the light-emitting region satisfying the following formula remains constant. [Math 1] however, S: Size of the light-emitting region R: Size of the diffraction-limited spot m: Magnification of the optical system F# ｉｍａｇｅ : F-number of the optical system on the image side d: The imaging distance f: Focal length of the optical system F# ｓｕｒｆａｃｅ : F number of the optical system on the surface to be measured
13. A step of imaging the emitted light from the surface to be measured of an emissive electronic display or emissive surface to be measured for sparkle contrast by forming an image of the emitted light on a two-dimensional sensor array surface using an optical system, The process includes a step of calculating the sparkle contrast based on the captured emitted light, The calculation of the sparkle contrast is performed based on the emitted light captured under imaging conditions in which the size of the light-emitting region on the surface to be measured, which contributes to the imaging of the diffraction-limited spot of the emitted light on the two-dimensional sensor array surface, is constant. The size of the light-emitting region is determined based on the size of the diffraction-limited spot, the focal length of the optical system, and the magnification of the optical system, which is determined from the imaging distance from the surface to be measured to the optical system. An optical measurement method comprising the step of adjusting the imaging distance, the focal length of the optical system, and at least one of the F-number of the optical system such that the size of the light-emitting region satisfying the following formula remains constant. [Math 2] [Math 3] however, M: Integration parameter S: Size of the light-emitting region R: Size of the diffraction-limited spot m: Magnification of the optical system F# ｉｍａｇｅ : F-number of the optical system on the image side d: The imaging distance f: Focal length of the optical system F# ｓｕｒｆａｃｅ : F number of the optical system on the surface to be measured A Ｃ : The size of the coherent region on the surface of the two-dimensional sensor array. A ｍ : The size of the uniform square detection element on the two-dimensional sensor array surface erf: Standard error function
14. The step of imaging the emitted light is as follows: A step of determining imaging conditions such that the size of the light-emitting region on the surface to be measured remains constant, The optical measurement method according to claim 12 or 13, further comprising the step of adjusting the optical system to achieve the determined imaging conditions.
15. The optical measurement method according to any one of claims 12 to 14, wherein the surface to be measured is the emission surface of the anti-glare layer in a display device having an anti-glare layer.
16. The optical measurement method according to any one of claims 12 to 14, wherein the surface to be measured is the emission surface of a backlight device.
17. The optical measurement method according to any one of claims 12 to 14, wherein the surface to be measured is the emission surface of a screen that projects light emitted from a projector.