Brightness correction device, brightness correction method, and program

Abstract

The luminance acquisition unit (300) acquires the measured luminance, which is the luminance of the measured surface (S) measured by the luminance meter (2). The field of view acquisition unit (302) acquires the field of view (α) of the luminance meter (2). The measurement angle acquisition unit (304) acquires the measurement angle (θ), which is the angle formed by the normal (N) of the measured surface (S) and the light-receiving axis (RA) of the luminance meter (2). The correction unit (308) corrects the error of the measured luminance relative to the ideal luminance based on the field of view (α) and the measurement angle (θ). The ideal luminance is the luminance of the measured surface (S) that should be measured by the luminance meter (2) when the measurement distance (d), which is the distance between the luminance meter (2) and the measurement position (MP) on the measured surface (S), and the field of view (α) are kept the same, and the measurement angle (θ) is set to 0 degrees.

Description

Technical Field

[0001] This disclosure relates to a brightness correction device, a brightness correction method, and a procedure. Background Technology

[0002] A luminance meter is known as a device for measuring the brightness of objects such as displays and lighting devices. Summary of the Invention

[0003] The problem that the invention aims to solve When using a luminance meter to measure the luminance of a surface at an angle relative to the surface being measured, it is sometimes impossible to obtain an accurate measurement value (hereinafter referred to as "measured luminance").

[0004] When the surface being measured satisfies Lambert's cosine law (i.e., when the surface being measured is a Lambert surface), the luminance of the surface being measured by the luminance meter is fixed and independent of the measurement angle formed by the normal to the surface being measured and the emitted light. For example, the surface of a display, lighting device, etc., can be regarded as a Lambert surface.

[0005] According to this law, in brightness measurement by a luminance meter, the surface being measured can be regarded as a Lambertian surface. If the measurement distance and the field of view, which are the distances between the luminance meter and the measurement position on the surface being measured, are fixed, then the measured brightness should be fixed and independent of the measurement angle.

[0006] However, in reality, even if the surface being measured can be considered a Lambertian surface, and the measurement distance and field of view are fixed, the measured brightness obtained by a luminance meter can sometimes vary depending on the measurement angle. That is, the aforementioned law stating that brightness is fixed regardless of the measurement angle holds true based on the condition that the field of view is sufficiently small. However, luminance meters possess optical systems, and their construction inherently results in a field of view that cannot be ignored. Therefore, in brightness measurements performed by a luminance meter, there are sometimes situations where the aforementioned law does not hold true.

[0007] The present invention was made in view of the above-mentioned problems, and its object is to provide a brightness correction device, brightness correction method and procedure that can obtain accurate brightness measurement even when the brightness of the measured surface is measured at an angle relative to the measured surface using a luminance meter.

[0008] Solution for solving the problem The brightness correction device of the present invention comprises: a brightness measurement acquisition unit for acquiring a measured brightness, which is the brightness of a measured surface measured by a luminance meter; a field of view acquisition unit for acquiring the field of view of the luminance meter; a measurement angle acquisition unit for acquiring a measurement angle, which is the angle formed by the normal of the measured surface and the light-receiving axis of the luminance meter; and a correction unit for correcting the error of the measured brightness relative to an ideal brightness based on the field of view and the measurement angle, wherein the ideal brightness is the brightness of the measured surface that should be measured by the luminance meter when the measurement distance (which is the distance between the luminance meter and the measurement position on the measured surface) and the field of view are kept the same, and the measurement angle is set to 0 degrees. Attached Figure Description

[0009] Figure 1 This is a diagram showing the configuration of a brightness measurement system incorporating a brightness correction device according to an embodiment of the present invention.

[0010] Figure 2 This is a three-dimensional diagram showing the situation where the brightness of the measured surface is measured from the front relative to the surface under conditions where the field of view is sufficiently small.

[0011] Figure 3 This is a three-dimensional diagram illustrating the situation where the brightness of the measured surface is measured from an oblique angle relative to the surface being measured, given a sufficiently small field of view.

[0012] Figure 4A This is a side view showing the situation where the brightness of the measured surface is measured from the front relative to the surface under a large field of view.

[0013] Figure 4B This is a three-dimensional diagram illustrating the situation where the brightness of the measured surface is measured from the front relative to the surface under conditions of a large field of view.

[0014] Figure 5A This is a side view diagram showing the situation where the brightness of the measured surface is measured from an oblique angle relative to the surface under conditions of a large field of view.

[0015] Figure 5B This is a three-dimensional diagram illustrating the situation where the brightness of the measured surface is measured from an oblique angle relative to the surface under conditions of a large field of view.

[0016] Figure 5C It is shown in a top view. Figure 5B A map of the measurement area.

[0017] Figure 5D It means Figure 5A A diagram showing the geometric relationship between the luminance meter and the surface being measured.

[0018] Figure 6This is a flowchart illustrating the operation of the brightness correction device according to an embodiment of the present invention. Detailed Implementation

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0020] [1. Composition of the brightness measurement system] Figure 1 This is a diagram illustrating the configuration of a brightness measurement system 1 that includes the brightness correction device 3 according to an embodiment of the present invention. As shown in the figure, the brightness measurement system 1 includes a brightness meter 2 and a brightness correction device 3.

[0021] [Luminometer] The luminance meter 2 is a device used to measure the luminance of a surface of an object to be measured. The object to be measured may be, for example, a display or a light source. However, the object to be measured is not limited to displays or light sources with light-emitting mechanisms; it may also be an object without light-emitting mechanisms, such as the wall of a building. The luminance meter 2 is connected to the luminance correction device 3 (described later) and outputs the measured luminance to the luminance correction device 3. This measured luminance is the luminance of the surface being measured, as determined by the luminance meter 2. The luminance meter 2 may include, for example, an optical system 20, a visibility correction filter 21, a photoelectric conversion unit 22, a viewfinder 23, a control unit 24, a storage unit 25, an operation unit 26, and a display unit 27.

[0022] The optical system 20 is a mechanism for focusing light from the surface being measured. The optical system 20 can have any structure, and for example, it may include one or more lenses, one or more apertures, and one or more mirrors. The optical system 20 includes a detection optical system for imaging the image of the surface being measured toward the photoelectric conversion unit 22, and a viewfinder optical system for imaging the image of the surface being measured toward the viewfinder 23 (described later). The field of view of the luminance meter 2 (described later) is determined by the optical system 20. Specifically, the field of view of the luminance meter 2 is determined based on the focal length, aperture size, etc., of the optical system 20.

[0023] The visibility correction filter 21 converts the light focused by the optical system 20 into light with a wavelength distribution corresponding to human visibility.

[0024] The photoelectric conversion unit 22 converts the light passing through the visibility correction filter 21 into an electrical signal. The photoelectric conversion unit 22 may be, for example, a photomultiplier tube (PMT), a silicon photodiode, or an avalanche photodiode.

[0025] The viewfinder 23 is an observation window for the user to visually view the image of the surface being measured. The user can adjust the optical system 20 while observing the viewfinder 23 to focus on the surface being measured.

[0026] The control unit 24 controls the optical system 20, the photoelectric conversion unit 22, etc., and converts the electrical signals output from the photoelectric conversion unit 22 into digital values ​​and sends them to the brightness correction device 3. The control unit 24 may include, for example, an amplifier, an A / D converter, a microcomputer, etc.

[0027] The storage unit 25 is, for example, an information recording medium such as ROM (Read Only Memory), RAM (Random Access Memory), or a hard disk, and is used to store the program executed by the control unit 24. Furthermore, the storage unit 25 can also function as the working memory of the control unit 24.

[0028] The operation unit 26 includes buttons, touch panels, etc., for users to perform various operations related to brightness measurement. Based on the user's operation, the operation unit 26 outputs the content of that operation to the control unit 24.

[0029] Display unit 27 is, for example, a liquid crystal display (LCD) or an organic EL (electroluminescence) display. Display unit 27 displays measurement results, etc., according to instructions from control unit 24.

[0030] It should be noted that the configuration of luminance meter 2 is not limited to the structure described above. For example, luminance meter 2 may also include various optical filters such as light-reducing filters. Furthermore, luminance meter 2 may also include a spectrometer that decomposes the light from the measured surface into wavelength components. That is, luminance meter 2 may also be a spectral radiometer.

[0031] [Brightness correction device] The brightness correction device 3 corrects the measured brightness, which is the brightness of the surface being measured by the luminance meter 2. The brightness correction device 3 is implemented by a commonly used computer. Specifically, the brightness correction device 3 includes a control unit 30, a storage unit 32, an input unit 34, and an output unit 36.

[0032] The control unit 30 is composed of a CPU (Central Processing Unit) and the like, and operates based on a program. For example, the control unit 30 operates as various functional units such as the brightness measurement acquisition unit 300, the field of view acquisition unit 302, the measurement angle acquisition unit 304, the correction coefficient calculation unit 306, and the correction unit 308, which will be described later, according to the executed program.

[0033] The storage unit 32 is a ROM, RAM, hard disk, etc., which stores various programs and data used in the control unit 30 and inputs and outputs this information to and from the control unit 30. The program using the brightness correction method of this embodiment can be stored in a semiconductor memory or other computer-readable information storage medium and read from that medium into the computer constituting the brightness correction device 3.

[0034] The input unit 34 includes a keyboard, mouse, touch panel, etc., for users to operate the brightness correction device 3. The output unit 36 ​​includes a monitor, printer, etc., for displaying the processing results of the brightness correction device 3 to the user through screen display, printing, etc.

[0035] [2. Theoretical Background] When the surface being measured satisfies Lambert's cosine law, the luminance of that surface, as measured by a luminance meter, is constant and independent of the measurement angle formed by the normal to the surface and the emitted light (hereinafter, this law will be referred to as the "fixed luminance law"). Here, Lambert's cosine law states that the luminance observed on the surface being measured is directly proportional to the cosine of the measurement angle. A surface that satisfies Lambert's cosine law is called a Lambert surface. For example, the surfaces of displays, lighting devices, etc., can be considered Lambert surfaces.

[0036] According to the law of constant brightness, in brightness measurement by a luminance meter, the surface being measured can be regarded as a Lambertian surface. If the measurement distance and the field of view, which are the distance between the luminance meter and the measurement position on the surface being measured, are fixed, then the measured brightness should be fixed and independent of the measurement angle.

[0037] However, in practice, the surface being measured can be considered a Lambertian surface. Even with a fixed measurement distance and field of view, the measured brightness obtained by a luminance meter can sometimes vary depending on the measurement angle. That is, this is because the law of constant brightness holds true only when the field of view is sufficiently small. Luminance meters possess optical systems, and their construction inherently results in a field of view that cannot be ignored. Therefore, in brightness measurements performed using a luminance meter, there are sometimes situations where the law of constant brightness does not hold. The following will use... Figures 2 to 5D The paper explains the cases where the brightness law holds true when the field of view is sufficiently small and the brightness law does not hold true when the field of view is large.

[0038] (1) When the field of view is small enough First, use Figure 2 and Figure 3 The following explanation addresses the case where the field of view is sufficiently small, i.e., when the constant brightness law holds. It should be noted that in the following explanation, the term "brightness constant law" will be used. Figure 1 The luminance meter 2 shown measures the luminance of the surface S of the object 4. Furthermore, the surface S can be considered a Lambertian surface.

[0039] (1-1) When measuring the brightness of the surface being measured from the front relative to the surface being measured. Figure 2 This is a three-dimensional diagram illustrating the measurement of the brightness of the measured surface S from the front, with a sufficiently small field of view. It should be noted that... Figure 2 The illustration of luminance meter 2 is omitted. Figure 2 The following scenario illustrates the measurement of the brightness of the emitted light EL, which is directed along the normal direction of the measured surface S from the measurement area MA, using a luminance meter 2. It should be noted that... Figure 2 For ease of explanation, only the light emitted from the measurement position MP is represented as the emitted light EL measured by the luminance meter 2. However, in reality, all the light emitted from the measurement area MA is measured by the luminance meter 2 as the emitted light EL. Figures 3 to 5D (The same applies to the middle). Here, the measurement position MP is the intersection of the measured surface S and the light-receiving axis RA of the luminance meter 2.

[0040] The measurement area MA is the region traversed by the measurement space MS within the measured surface S. The measurement space MS is the space determined by the field of view of the luminance meter 2. Figure 2 In this case, because the field of view is sufficiently small, the measurement space MS becomes cylindrical. Therefore, when the luminance meter 2 is directly opposite the measured surface S... Figure 2 In the middle, the measured area MA becomes a perfect circle.

[0041] Here, if the luminance of the emitted light EL emitted from the measurement area MA in the direction of the normal to the measured surface S is set as I0, and the area of ​​the measurement area MA is set as A0, then the measured luminance L0 measured by the luminance meter 2 is expressed by the following formula (1). It should be noted that when the focal point of the optical system 20 of the luminance meter 2 coincides with the measurement position MP on the surface being measured S (focusing), the luminance meter 2 only measures the brightness of the emitted light EL from the measurement area MA on the surface being measured S. Figure 2 In the process, the optical system 20 of the luminance meter 2 is adjusted to focus on the measurement position MP on the surface being measured S (in Figures 3 to 5D The same applies to China.

[0042] (1-2) When measuring the brightness of the surface being measured from an oblique angle relative to the surface being measured. Figure 3 This is a three-dimensional diagram illustrating the measurement of the brightness of the measured surface S from an oblique angle when the field of view is sufficiently small. It should be noted that... Figure 3 The illustration of luminance meter 2 is omitted. Figure 3The following situation is illustrated: the measurement distance and field of view, which are the distances between the luminance meter 2 and the measurement position MP, are compared with... Figure 2 The luminance of the surface being measured is measured by moving the luminance meter 2 by an angle θ relative to the normal N of the surface being measured, while keeping the conditions the same. Angle θ is the measurement angle formed by the normal N of the surface being measured and the light-receiving axis RA of the luminance meter 2.

[0043] Here, if the luminance of the component of the emitted light EL emitted from the measurement area MA with the normal N relative to the measured surface S in the direction of the angle θ is set as I, then the measured luminance L measured by the luminance meter 2 is expressed by the following formula (2). It should be noted that the denominator of equation (2) (the apparent area of ​​the measurement region MA) should be the product of the area A of the measurement region MA when the luminance meter 2 is offset by an angle θ from the normal N of the measured surface S and is opposite to the measured surface S, and the cosine of the measurement angle θ. This becomes the area A0 of the measurement region MA when the luminance meter 2 is directly opposite the measured surface S (refer to (1-1)). This is because the luminance meter 2 is designed for luminance measurement performed from the front relative to the measured surface.

[0044] Next, the luminosity I of the component of the emitted light EL emitted from the measurement area MA, which is angularly θ relative to the normal N of the measured surface S, is calculated using the following equation (3). In equation (3), I ⊥ It is the luminosity of the component of the emitted light EL emitted from the measurement area MA in the direction of the normal N of the measured surface S. Photometric I ⊥ It is obtained by the following formula (4). Here, I0 is the luminance of the emitted light EL emitted from the measurement area MA in the direction of the normal N of the measured surface S when the luminance meter 2 is facing the measured surface S (refer to...). Figure 2 A is the area of ​​the measurement region MA when the direction of the luminance meter 2 is offset by an angle θ from the normal N relative to the measured surface S and is opposite to the measured surface S. Here, the area A of the measurement region MA is calculated using the following formula (5). It should be noted that the measurement region MA is the area traversed by the measurement space MS in the measured surface S. Therefore, the luminance meter 2 is positioned relative to the measured surface S in a direction offset by an angle θ from the normal N relative to the measured surface S. Figure 3 In the measurement area MA, the region becomes elliptical. If equations (4) and (5) are substituted into equation (3), the result is shown in equation (6) below, which shows that the luminous intensity I is equal to the luminous intensity I0. Then, if we substitute equation (6) into equation (2), we can obtain the following equation (7). Finally, based on equations (1) and (7), we can obtain equation (8). Based on the above, when the field of view is sufficiently small, the measured brightness remains unchanged when measuring the brightness of the measured surface S from the front and from an oblique angle. That is, when the field of view is sufficiently small, the measured surface S can be considered a Lambertian surface; if the measurement distance and field of view are fixed, the measured brightness remains constant regardless of the measurement angle θ.

[0045] (2) Cases with large field of view Next, use Figures 4A to 5D This section explains the case where the field of view is large, i.e., the case where the constant brightness law does not hold.

[0046] (2-1) When measuring the brightness of the surface being measured from the front relative to the surface being measured. Figure 4A This is a side view showing the situation where the brightness of the measured surface S is measured from the front relative to the measured surface S when the field of view is large. Figure 4B This is a three-dimensional diagram illustrating the measurement of the brightness of the measured surface S from the front when the field of view is large. It should be noted that... Figure 4B The illustration of luminance meter 2 is omitted.

[0047] exist Figure 4A and Figure 4B In the middle, the field of view is relatively large, therefore... Figure 2 and Figure 3 Unlike other examples, the measuring space MS' is not cylindrical but conical. Since the measuring region MA' is the area traversed by the measuring space MS' on the measured surface S, the luminance meter 2 and the measured surface S face each other... Figure 4A and Figure 4B In the middle, the measured area MA' becomes a perfect circle.

[0048] The area A0' of the measurement region MA' is calculated using the following formula (9). In the following formula (9), d is the measurement distance and α is the field of view angle. Here, if the luminance of the emitted light EL emitted from the measurement area MA' in the direction of the normal to the measured surface S is set as I0', then the measured luminance L0' measured by the luminance meter 2 is expressed by the following formula (10). (2-2) When measuring the brightness of the surface being measured from an oblique angle relative to the surface being measured. Figure 5A This is a side view showing the situation where the brightness of the measured surface S is measured from an oblique angle relative to the measured surface S when the field of view is large. Figure 5B This is a three-dimensional diagram illustrating the measurement of the brightness of the measured surface S from an oblique angle when the field of view is large. It should be noted that... Figure 5B The illustration of luminance meter 2 is omitted.

[0049] exist Figure 5A and Figure 5B The following scenario is illustrated: the measurement distance d, which is the distance between the luminance meter 2 and the measurement position MP, and the field of view α are shown in the figure. Figure 4A and Figure 4B The luminance of the surface being measured is measured by moving the luminance meter 2 by an angle θ relative to the normal N of the surface being measured, while keeping the conditions the same. Angle θ is the measurement angle formed by the normal N of the surface being measured and the light-receiving axis RA of the luminance meter 2.

[0050] Here, if the luminance of the component of the emitted light EL emitted from the measurement area MA' with the normal N relative to the measured surface S at an angle θ is set as I', then the measured luminance L' measured by the luminance meter 2 is obtained by the following formula (11). The denominator of formula (11) (the apparent area of ​​the measurement area MA') should be the product of the area A' of the measurement area MA' when the luminance meter 2 is offset by an angle θ from the normal N of the measured surface S and is opposite to the measured surface S, and the cosine of the measurement angle θ. The reason why it is the area A0' of the measurement area MA' when the luminance meter 2 is directly opposite the measured surface S (refer to (2-1)) is as described above. The luminosity I' is obtained by the following equation (12). In equation (12), I ⊥ 'The luminosity of the component of the emitted light EL emitted from the measurement area MA in the direction of the normal N to the measured surface S.' Photometric I ⊥ 'It is obtained by the following formula (13). Here, I0' is the luminance of the emitted light EL emitted from the measurement area MA' in the direction of the normal N of the measured surface S when the luminance meter 2 is facing the measured surface S (refer to Figure 4A and Figure 4B A' is the area of ​​the measurement region MA' when the direction of the luminance meter 2 is offset by an angle θ from the normal N of the measured surface S and is opposite to the measured surface S. If we substitute equation (13) into equation (12), we can obtain the following equation (14). The following is for reference Figure 5C and Figure 5D The derivation process of the area A' of the measured region MA' is explained. Figure 5C It is shown in a top view. Figure 5B The diagram of the measurement area MA'. Figure 5D It means Figure 5A A diagram showing the geometric relationship between the luminance meter 2 and the surface S being measured. It should be noted that... Figure 5D The illustration of luminance meter 2 is omitted.

[0051] like Figure 5C As shown, the measurement area MA' is the region traversed by the measurement space MS in the measured surface S. Therefore, when the luminance meter 2 is obliquely opposite to the measured surface S... Figure 3 In the middle, the measurement area MA' becomes elliptical.

[0052] Here, when the major radius of the measurement region MA' is set as a and the minor radius as b, the area A' of the measurement region MA' is calculated by the following formula (15) according to the formula for the area of ​​an ellipse. like Figure 5C and Figure 5D As shown, when the major axis LA of the measurement area MA' is divided into two at the measurement position MP, the length of the part LA1 closer to the luminance meter 2 is set as l1, and the length of the part LA2 farther from the luminance meter 2 is set as l2.

[0053] Consider using l1 and l2 to represent the major radius a and minor radius b of the measurement region MA'. First, the major radius a can be represented by the following equation (16). Next, using the equation of an ellipse, the minor radius b is calculated. The intersection of the perpendicular PL from the major axis LA passing through the measurement position MP and the outer edge of the measurement area MA' is set as X (refer to...). Figure 5C In a coordinate plane with the center C of the measured area MA' as the origin, the major axis LA as the x-axis, and the minor axis SA as the y-axis, the coordinates of point X are represented by the following formula (18). By substituting the coordinates of point X, as expressed by equation (17), into the equation of the ellipse, we can obtain the following equation (18). By substituting equation (16) into equation (18) and transforming it, we can obtain the short radius b expressed by equation (19). Next, we consider using the measurement distance d, the field of view angle α, and the measurement angle θ to represent l1 and l2. Here, we define d1 as the distance between the foot of the perpendicular line F1 of the line from the intersection point P1 of line LA1 and the outer side of the measurement space MS' to the light-receiving axis RA and the measurement position MP (refer to...). Figure 5D Furthermore, the distance between the foot of the perpendicular F2 of the perpendicular line from the intersection point P2 of line LA2 and the outer side of the measurement space MS' to the light-receiving axis RA and the measurement position MP is set as d2. At this time, l1 and l2 are represented by the following equations (20) and (21), respectively. Here, regarding the distance between point P1 and point F1, the following equation (22) holds. Furthermore, regarding the distance between point P2 and point F2, the following equation (23) holds. According to equations (22) and (23), d1 and d2 can be represented by equations (24) and (25) respectively. By substituting equations (24) and (25) into equations (20) and (21) respectively, we can obtain equations (26) and (27). By substituting equations (16), (19), (26), and (27) into equation (15) and transforming it, the measured area A' can be obtained as expressed by equation (28). If we substitute equation (28) into equation (14), we can obtain the luminosity I' expressed by equation (29). Finally, if we substitute equations (9) and (29) into equation (11), we can obtain equation (30) according to equation (10). According to equation (30), when the field of view α is large, the measured brightness may change when the brightness of the measured surface S is measured from the front relative to the measured surface S and when the brightness of the measured surface S is measured from the oblique direction relative to the measured surface S. That is, when the field of view α is large, even if the measured surface S can be regarded as a Lambertian surface, and the measurement distance d and the field of view α are fixed, the measured brightness may still change according to the measurement angle θ.

[0054] According to the brightness correction device 3 of this embodiment, the error of the measured brightness L' when the measured surface S is measured from an oblique angle relative to the measured brightness L0' when the measured surface S is measured from the front angle can be corrected (refer to formula (30)). That is, according to the brightness correction device 3, even when the brightness of the measured surface S is measured from an oblique angle relative to the measured surface S using the luminance meter 2, an accurate measured brightness can be obtained. Hereinafter, the brightness correction device 3 will be described in detail.

[0055] [3. Functions achieved by the brightness correction device] The brightness correction device 3 includes a brightness measurement acquisition unit 300, a field of view acquisition unit 302, a measurement angle acquisition unit 304, a correction coefficient calculation unit 306, and a correction unit 308. The brightness measurement acquisition unit 300, the field of view acquisition unit 302, the measurement angle acquisition unit 304, the correction coefficient calculation unit 306, and the correction unit 308 are mainly implemented by the control unit 30.

[0056] [Brightness Measurement and Acquisition Unit] The luminance acquisition unit 300 acquires the measured luminance, which is the luminance of the measured surface S measured by the luminance meter 2. The luminance acquisition unit 300 can acquire the measured luminance stored in the storage unit 25 of the luminance meter 2 and output from the luminance meter 2 to the luminance correction device 3, or it can acquire the measured luminance manually input by the user via the input unit 34.

[0057] [Field of view acquisition unit] The field of view acquisition unit 302 acquires the field of view α of the luminance meter 2 (refer to...). Figure 5A (etc.). The field of view acquisition unit 302 can acquire the field of view α stored in the storage unit 25 of the luminance meter 2 and output from the luminance meter 2 to the luminance correction device 3, or it can acquire the field of view α manually input by the user via the input unit 34.

[0058] [Angle Measurement Unit] The angle acquisition unit 304 acquires the measurement angle θ, which is the angle formed by the normal N of the measured surface S and the light-receiving axis RA of the luminance meter 2 (see reference). Figure 5A(etc.). The measuring angle acquisition unit 304 can acquire the measuring angle θ stored in the storage unit 25 of the luminance meter 2 and output from the luminance meter 2 to the luminance correction device 3, or it can acquire the measuring angle θ manually input by the user via the input unit 34.

[0059] [Correction Coefficient Calculation Department] The correction factor calculation unit 306 calculates the correction factor K, which represents the ratio of ideal luminance to measured luminance, based on the field of view angle α and the measurement angle θ. C Ideal brightness is the brightness of the surface S measured by luminance meter 2, which is the distance between luminance meter 2 and the measurement position MP on the surface S being measured, and the field of view angle α are kept constant, with the measurement angle θ set to 0 degrees. (Refer to...) Figure 4A and Figure 4B Specifically, the ideal brightness is represented by equation (10).

[0060] Specifically, the correction coefficient K C It is expressed by the following equation (31). That is, the correction coefficient K C It is the reciprocal of the factor related to the brightness L0' of equation (30). Correction coefficient K C It can also be the value obtained by multiplying the ratio of the measured area to the ideal measured area by the cosine of the measured angle θ, or the value obtained by dividing the ratio of the measured area to the ideal measured area by the cosine of the measured angle θ. The measured area is the area of ​​the measured region MA' determined by the measured distance d, the field of view α, and the measured angle θ (see...). Figure 5B Specifically, it is represented by expression (28). The ideal measurement area is the area of ​​the measurement region when the measurement distance d and the field of view angle α are kept the same, and the measurement angle θ is set to 0 degrees (refer to...). Figure 4B Specifically, it is represented by equation (9). In this embodiment, the correction coefficient K C It is the value obtained by dividing the ideal measured area by the measured area and then dividing the value by the cosine of the measured angle θ.

[0061] [Correction Department] The correction unit 308 corrects the correction coefficient K. C It is used to correct the error of the measured brightness relative to the ideal brightness when measuring brightness. Specifically, the correction unit 308 corrects the error by multiplying the measured brightness by a correction factor K. C This is used to correct the error in measuring brightness relative to ideal brightness.

[0062] [4. Operation of the brightness correction device] Figure 6 This is a flowchart illustrating the operation of the brightness correction device 3 according to an embodiment of the present invention. Figure 6The processing shown is performed by the control unit 30 according to the program stored in the storage unit 32.

[0063] Specifically, first, the control unit 30 acquires the measured brightness (S600). Next, the control unit 30 acquires the field of view angle α (S602) and the measurement angle θ (S604). The control unit 30 calculates the correction coefficient K based on the field of view angle α and the measurement angle θ. C (S606). Then, the control unit 30 uses the correction coefficient K C The measurement of luminance is used to correct the error between the measured luminance and the ideal luminance (S608). Finally, the control unit 30 displays the correction result on the output unit 36 ​​(S610) and the process ends.

[0064] [5. Summary] The brightness correction device 3 of this embodiment described above can correct the error of the measured brightness relative to the ideal brightness. Therefore, even when the brightness of the measured surface is measured at an angle relative to the measured surface using a luminance meter, an accurate measured brightness can be obtained.

[0065] It should be noted that the present invention is not limited to the embodiments described above. Furthermore, the specific texts and values ​​described above, as well as the specific texts and values ​​in the accompanying drawings, are illustrative and not limiting.

[0066] For example, the correction factor K C It can also be the reciprocal of the value shown in equation (31). In this case, the correction unit 308 can divide the measured brightness by the correction coefficient K. C This is used to correct the error in measuring brightness relative to ideal brightness.

Claims

1. A brightness correction device, comprising: The brightness acquisition unit acquires the measured brightness, which is the brightness of the surface being measured as determined by a brightness meter. A field of view acquisition unit acquires the field of view of the luminance meter; The measurement angle acquisition unit acquires the measurement angle, which is the angle formed by the normal of the measured surface and the light-receiving axis of the luminance meter. as well as The correction unit corrects the error in the measured brightness relative to the ideal brightness based on the field of view and the measurement angle. The ideal brightness is the brightness of the surface to be measured by the luminance meter when the measurement distance (the distance between the luminance meter and the measurement position on the surface to be measured) and the field of view are kept the same, and the measurement angle is set to 0 degrees.

2. The brightness correction device according to claim 1, further comprising: The correction coefficient calculation unit calculates a correction coefficient representing the ratio of the ideal luminance to the measured luminance based on the field of view and the measurement angle. The correction unit corrects the error by applying the correction coefficient to the measured brightness.

3. The brightness correction device according to claim 2, wherein, The correction coefficient is a value obtained by multiplying the ratio of the measured area to the ideal measured area by the cosine of the measured angle, or by dividing the ratio of the measured area to the ideal measured area by the cosine of the measured angle. The measured area is the area of ​​the measurement region determined based on the measurement distance, the field of view, and the measurement angle. The ideal measurement area is the area of ​​the measurement region when the measurement distance and the field of view are kept the same, and the measurement angle is set to 0 degrees.

4. The brightness correction device according to claim 3, wherein, The measurement area is the region traversed by the conical measurement space in the measured surface, determined according to the field of view.

5. The brightness correction device according to claim 3 or 4, wherein, The measurement area has an elliptical shape.

6. A brightness correction method, comprising: The brightness measurement acquisition step involves acquiring the measured brightness, which is the brightness of the surface being measured measured by a brightness meter. The field of view acquisition step involves acquiring the field of view of the luminance meter. The measurement angle acquisition step involves acquiring the measurement angle, which is the angle formed by the normal of the measured surface and the light-receiving axis of the luminance meter. as well as The calibration step corrects for the error in the measured brightness relative to the ideal brightness based on the field of view and the measurement angle. The ideal brightness is the brightness of the surface to be measured by the luminance meter when the measurement distance (the distance between the luminance meter and the measurement position on the surface to be measured) and the field of view are kept the same, and the measurement angle is set to 0 degrees.

7. A program that enables a computer to function as a unit: The brightness acquisition unit acquires the measured brightness, which is the brightness of the surface being measured by a brightness meter. A field of view acquisition unit acquires the field of view of the luminance meter; The measurement angle acquisition unit acquires the measurement angle, which is the angle formed by the normal of the measured surface and the light-receiving axis of the luminance meter. as well as The correction unit corrects the error in the measured brightness relative to the ideal brightness based on the field of view and the measurement angle. The ideal brightness is the brightness of the surface to be measured by the luminance meter when the measurement distance (the distance between the luminance meter and the measurement position on the surface to be measured) and the field of view are kept the same, and the measurement angle is set to 0 degrees.

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