JP2023102499A - Display method and display device - Google Patents

Abstract

To suppress degradation of reproducibility of a color in a case where an output image is displayed.SOLUTION: A display method comprises: performing first correction processing in which first brightness that is brightness of a first color component having highest brightness of a plurality of color components included in input pixel information indicating one pixel out of an input image composed of a plurality of pixels is multiplied by a first gain; performing second correction processing in which second brightness of a second color component being different from the first color component of the plurality of color components is multiplied by a second gain being smaller than the first gain; and displaying an output image using output pixel information which is obtained by performing the first correction processing and the second correction processing of the input pixel information.SELECTED DRAWING: Figure 8

Description

The present invention relates to a display method and a display device.

2. Description of the Related Art Conventionally, it has become popular to perform correction processing on an input image input to a display device according to the display characteristics of the display device. For example, Patent Document 1 below discloses a display device that performs gradation conversion on an input signal based on information on the luminance of the input signal and information on the display luminance in a low gradation range where the luminance of the input signal is lower than the branch point.

JP 2019-184629 A

However, the above-mentioned Patent Document 1 does not describe conversion of luminance for a plurality of color components when a pixel indicated by an input signal has a plurality of color components. If the conversion described in Patent Document 1 is performed using one luminance for each pixel, even if the luminance of the first color component of a pixel differs from the luminance of the second color component, the same correction is performed for high luminance and low luminance. As a result of performing the same correction for high luminance and low luminance, the balance between the first color component and the second color component is lost, and color reproducibility is sometimes deteriorated.

A display method according to an aspect of the present invention includes: performing a first correction process of multiplying a first lightness, which is the lightness of a first color component having the highest lightness among a plurality of color components included in input pixel information indicating one pixel among a plurality of pixels, by a first gain; performing a second correction process of multiplying a second lightness of a second color component different from the first color component among the plurality of color components by a second gain smaller than the first gain; and performing a second correction process of multiplying the input pixel information. displaying an output image using output pixel information obtained by executing the first correction process and the second correction process.

A display device according to an aspect of the present invention includes an optical device and a control circuit that controls the optical device, wherein the control circuit performs a first correction process of multiplying a first brightness, which is the brightness of a first color component having the highest brightness among a plurality of color components included in input pixel information indicating one pixel in an input image formed of a plurality of pixels, by a first gain, and a second brightness of a second color component, which is different from the first color component among the plurality of color components, and has a second brightness smaller than the first gain. executing a second correction process of multiplying the input pixel information by a second gain; and displaying an output image on the optical device using output pixel information obtained by executing the first correction process and the second correction process on the input pixel information.

1 is a schematic diagram illustrating a display system 1 according to a first embodiment; FIG. 2 is a diagram showing the configuration of a digital camera 20; FIG. FIG. 4 is a diagram showing an example of pixel information PX[1] to pixel information PX[M]; FIG. 4 is a diagram for explaining gamma correction executed by the control circuit 21; 2 is a diagram showing the configuration of a projector 10; FIG. FIG. 3 is a diagram showing an example of a projection device 18; 4 is a diagram showing functions of the projector 10. FIG. FIG. 4 is a diagram for explaining a first gamma function γ1 and a second gamma function γ2; FIG. 4 is a diagram for explaining the relationship between the first gamma function γ1 and the second gamma function γ2; FIG. 4 is a diagram showing a flowchart showing the operation of the projector 10; The figure which shows the function of the projector 10a of 2nd Embodiment. FIG. 5 is a diagram for explaining an example of correction by a second correction processing execution unit 112a; FIG. 5 is a diagram showing a flowchart showing the operation of the projector 10a. FIG. 5 is a diagram showing a specific example of lightness after correction; FIG. 15 is a diagram showing brightness ratios based on the numerical values in FIG. 14; FIG. 4 is a diagram showing a specific example of hue and saturation;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from the actual ones. In addition, the embodiments described below are preferred specific examples of the present invention, and therefore are subject to various technically preferable limitations. However, the scope of the present invention is not limited to these forms unless there is a description to the effect that the present invention is particularly limited in the following description.

1. First Embodiment FIG. 1 is a schematic diagram illustrating a display system 1 according to a first embodiment. The display system 1 displays the output image Po on the projection surface SC. The display system 1 has a projector 10 and a digital camera 20 . Note that the projector 10 is an example of a “display device”.

The projector 10 acquires input image information PDi from the digital camera 20 and projects an output image Po based on the input image information PDi onto the projection surface SC.

The digital camera 20 generates the input image information PDi by capturing an image of a person, a landscape, or the like captured by the user's operation of the digital camera 20 . The digital camera 20 outputs the generated input image information PDi to the projector 10 .

1.1. Configuration of Digital Camera 20 FIG. 2 is a diagram showing the configuration of the digital camera 20. As shown in FIG. The digital camera 20 has at least one control circuit 21 , a memory circuit 22 , a communication device 23 , an input device 26 , an output device 27 and a light receiving device 28 . The control circuit 21, the memory circuit 22, the communication device 23, the input device 26, the output device 27, and the light receiving device 28 are interconnected by a bus 29 for communicating information.

The control circuit 21 is a computer such as a CPU. CPU is an abbreviation for Central Processing Unit. Note that the control circuit 21 may be configured by one or more processors.

The storage circuit 22 is composed of a magnetic storage device, a flash ROM, or the like. ROM is an abbreviation for Read Only Memory. The storage circuit 22 is a recording medium readable by the control circuit 21, and stores a plurality of programs including a control program executed by the control circuit 21, various information used by the control circuit 21, and the like.

The communication device 23 is hardware that communicates with the projector 10 . The communication device 23 is, for example, a NIC (Network Interface Card).

The input device 26 is a device for a user to input information. The input device 26 is, for example, buttons provided on the back of the digital camera 20 .

The output device 27 is an output device that outputs information to the outside. The output device 27 is, for example, a display, a speaker, an LED lamp, or the like. LED is an abbreviation for Light Emitting Diode.

The light-receiving device 28 is an imaging element that detects light transmitted through a lens (not shown), and includes a plurality of light-receiving elements arranged in a matrix on a light-receiving surface. Each light receiving element is, for example, a photodiode, and generates a detection signal according to the amount of light received. A detection signal generated by one light receiving element indicates one pixel. For example, a known CMOS sensor and CCD are preferably used as the light receiving device 28 . CMOS is an abbreviation for Complementary MOS. MOS is an abbreviation for Metal Oxide Semiconductor. CCD is an abbreviation for Charge Coupled Device.

The light receiving device 28 generates detection signals generated by the plurality of light receiving elements as original image information PDg. An image indicated by the original image information PDg is hereinafter referred to as an “original image”. The original image is an example of the "first image before correction". The original image information PDg has M pieces of pixel information PX indicating one pixel. M indicates the number of pixels included in the original image information PDg. M is an integer of 2 or more. In the following, in order to distinguish between the M pieces of pixel information PX, the m-th pixel information PX may be referred to as pixel information PX[m]. m is an integer of 1 or more and M or less. For example, M is 1280×720=921,600 when the resolution of the image indicated by the original image information PDg is HD, 1920×1080=2,073,600 when the resolution is full HD, and 3840×2160=8,294,400 when the resolution is 4K. HD is an abbreviation for High Definition.

FIG. 3 is a diagram showing an example of pixel information PX[1] to pixel information PX[M]. The pixel information PX[m], which is the m-th pixel information PX in the original image information PDg, the input image information PDi described later, or the output image information PDo described later, has information indicating the lightness of a plurality of color components representing one pixel. The plurality of color components are three types of color components, red, green, and blue, in the illustration of FIG. The pixel information PX[m] indicates the level of lightness from the brightest lightness to the darkest lightness for each of the three color components of red, green, and blue. Hereinafter, the level of brightness difference, in other words, the level from the brightest brightness to the darkest brightness is referred to as "gradation". Also, the number of steps of lightness difference is described as "the number of gradations". The number of gradations that the pixel information PX[m] can take may be represented by "bit depth" using the number of bits of information indicating the lightness of one color component of the pixel information PX[m]. For example, if the bit depth of one color component is 8 bits, it means that the brightness difference can be expressed in 256 levels, and if the bit depth of one color component is 10 bits, it means that the brightness difference can be expressed in 1024 levels. HDR10, which is one of the HDR standards, has a bit depth of 10 bits. HDR is an abbreviation for High Dynamic Range. At HDR10, the highest brightness is 10000nit. nit is a unit of lightness. On the other hand, the maximum brightness that can be displayed by the projector 10 is less than 10000 nits, typically between several hundred nits and a thousand nits. Depending on the model of the projector, the maximum brightness that can be displayed by the projector may also fluctuate. For example, depending on the projector, the focus position of the output image Po may be adjustable. This projector may be able to adjust the size of the output image Po by changing the distance between the projector and the projection surface SC and adjusting the focal length of the output image Po. The maximum brightness that can be displayed by the projector also varies according to the size of the output image Po. However, in the first embodiment, for simplification of explanation, it is assumed that the maximum brightness that can be displayed by the projector 10 is a fixed value.

Returning to FIG. The control circuit 21 generates the input image information PDi by correcting the gradation of the image indicated by the plurality of pieces of pixel information PX included in the original image information PDg for the original image information PDg. More specifically, the control circuit 21 generates corrected pixel information PX[m] included in the input image information PDi by correcting the lightness of a plurality of color components included in one piece of pixel information PX[m] included in the original image information PDg. Therefore, the input image information PDi has M pieces of pixel information PX, which is the same number as the pixel information PX included in the original image information PDg. Hereinafter, the pixel information PX included in the original image information PDg may be referred to as "original pixel information PXg", and the pixel information PX included in the input image information PDi may be referred to as "input pixel information PXi". Also, the m-th original pixel information PXg may be described as original pixel information PXg[m], and the m-th input pixel information PXi may be described as input pixel information PXi[m]. A pixel indicated by the input pixel information PXi[m] is an example of "one pixel". Hereinafter, correcting the gradation of an image may be referred to as "gamma correction". The gamma correction executed by the control circuit 21 will be explained using FIG.

1.2. Gamma Correction of Digital Camera 20 FIG. 4 is a diagram for explaining the gamma correction executed by the control circuit 21. As shown in FIG. A camera gamma characteristic gc shown in the graph 401 shown in FIG. 4 indicates the characteristic of the correction function used in the gamma correction of the control circuit 21. A correction function used in the gamma correction of the control circuit 21 is hereinafter referred to as "camera gamma function γc". The camera gamma function γc uses the brightness of the image indicated by the original pixel information PXg as a variable, and outputs the corrected brightness. The camera gamma function γc is an example of a “third correction function”. The camera gamma function γc may exist for each of the plurality of color components, or may be common among the plurality of color components. For simplicity of explanation, the camera gamma function γc is assumed to be common among a plurality of color components.

The horizontal axis of the graph 401 indicates possible gradations of the brightness of the original pixel information PXg[m], and the vertical axis of the graph 401 indicates possible gradations of the brightness of the input pixel information PXi[m]. The camera gamma function γc corrects the brightness belonging to the gradation TN1 of the dark portion to the brightness belonging to the gradation TN3, and corrects the brightness belonging to the gradation TN2 of the bright portion to the brightness belonging to the gradation TN4 among the gradations that the brightness of the original pixel information PXg can take. As shown in FIG. 4, there is a relationship of PXi[m]=γc(PXg[m]). As shown by the camera gamma characteristic gc, the number of gradations of TN1, the number of gradations TN2, the number of gradations TN3, and the number of gradations TN4 have the relationship represented by the following equation (1-1).

(Number of gradations of gradation TN3)/(Number of gradations of gradation TN1)>(Number of gradations of gradation TN4)/(Number of gradations of gradation TN2) (1-1)

Expression (1-1) is derived from the characteristic that human vision is more sensitive to the gradation TN1 of the dark area than to the gradation TN2 of the bright area. More specifically, for a predetermined number of gradations extracted from each of the dark gradation TN1 and the bright gradation TN2, the human eye can perceive the gradation of the dark gradation, but may not be able to perceive the gradation of the bright region. Since the human vision is less sensitive to the gradation TN2 of the bright area than the gradation TN1 of the dark area, the camera gamma function γc is corrected so that the gradation number of the gradation TN2 is reduced compared to the gradation number of the gradation TN1, thereby suppressing the bit depth of the input pixel information PXi to a low bit while expressing the gradation smoothly within the range perceivable by humans. In the following description, it is assumed that the input image information PDi conforms to HDR10. That is, the bit depth of one color component of the input pixel information PXi is 10 bits, and the input pixel information PXi can express 1024 levels of lightness from 0 to 1023 for one color component. Note that the bit depth of one color component of the original pixel information PXg may be 10 bits or more, or may be 10 bits or less.

The camera gamma function γc is represented by the following formula (1-2).

However, the lightness LgMAX is the maximum lightness that the original pixel information PXg can have. The lightness LgMAX may match or may differ from the maximum lightness that the input pixel information PXi can have. The coefficient γ is a gamma correction value. In the camera gamma function γc, the coefficient γ is a real number greater than 0 and less than 1. For example, the factor γ is approximately 0.45.

As shown in FIG. 4 and equation (1-2), the camera gamma function γc outputs 0 as the brightness of the input pixel information PXi[m] when the brightness of the original pixel information PXg[m] is 0, and outputs the maximum brightness of the input pixel information PXi[m] when the brightness of the original pixel information PXg[m] is the maximum value. Furthermore, the camera gamma function γc is a function in which the brightness of the input pixel information PXi[m] monotonously increases as the brightness of the original pixel information PXg[m] increases. Furthermore, the slope of the camera gamma function γc monotonously decreases as the brightness of the original pixel information PXg[m] increases.

The control circuit 21 generates input pixel information PXi[m] by inputting the brightness of the pixel indicated by the original pixel information PXg[m] to the camera gamma function γc. As specific implementations of the camera gamma function γc, there are the following two aspects. In the first aspect, the camera gamma function γc is a function for inputting the brightness of the image indicated by the original pixel information PXg[m] into Equation (1-2). In the second mode, the manufacturer or user of the digital camera 20 causes the storage circuit 22 to store the lookup table generated based on the formula (1-2). The lookup table is hereinafter referred to as "LUT". A LUT is a table that associates all input values that can be input to a function with output values obtained when the input values are input to the function. The LUT has information that associates all input values that can be input to a function with output values that correspond one-to-one to all input values. Hereinafter, for the sake of simplification of explanation, an LUT that associates all input values that can be input to a certain function with output values obtained when input values are input to a certain function may be referred to as "LUT corresponding to a certain function".

One or both of a one-dimensional LUT and a three-dimensional LUT may be utilized in image processing. A one-dimensional LUT is a table that associates an input value for one color component with an output value for one color component. A three-dimensional LUT is a table that associates input values for three color components with output values for three color components. In the following description, the term “LUT” is assumed to be a one-dimensional LUT unless otherwise specified.

The LUT generated based on the equation (1-2) is a table in which the brightness is input to the equation (1-2) for each brightness from the minimum brightness to the maximum brightness that the pixel can take, and the input brightness and the brightness output by the equation (1-2) are associated.

The control circuit 21 transmits the input image information PDi to the projector 10 via the communication device 23 .

1.3. Configuration of Projector 10 FIG. 5 is a diagram showing the configuration of the projector 10 . The projector 10 has at least one control circuit 11 , a memory circuit 12 , a communication device 13 , an input device 16 and a projection device 18 . The control circuit 11, the memory circuit 12, the communication device 13, the input device 16, and the projection device 18 are interconnected by a bus 19 for communicating information. The projection device 18 is an example of an "optical device".

The control circuit 11 is a computer such as a CPU. Note that the control circuit 11 may be configured by one or more processors. The control circuit 11 performs gamma correction on the input image information PDi to generate output image information PDo representing the output image Po. More specifically, the control circuit 11 performs gamma correction on the image indicated by the input pixel information PXi included in the input image information PDi, and generates corrected pixel information PX included in the output image information PDo. Therefore, the output image information PDo has M pieces of pixel information PX, which is the same number as the input pixel information PXi included in the input image information PDi. Hereinafter, the pixel information PX included in the output image information PDo may be referred to as "output pixel information PXo". Also, the m-th output pixel information PXo may be described as output pixel information PXo[m].

The storage circuit 12 is composed of a magnetic storage device, a flash ROM, or the like. The storage circuit 12 is a recording medium readable by the control circuit 11 . The storage circuit 12 stores a plurality of programs including a control program executed by the control circuit 11, various information used by the control circuit 21, and the like.

The communication device 13 is hardware that communicates with the digital camera 20 . The communication device 13 is, for example, a NIC. The communication device 13 receives input image information PDi from the digital camera 20 .

The input device 16 is a device for a user to input information. The input device 16 is, for example, a plurality of buttons including a function list display key for displaying a list of functions of the projector 10, an up key, a down key, a left key, a right key, an enter key, and a cancel key. Alternatively, the input device 16 may be composed of one or more types of devices such as a pointing device and a touch panel. Alternatively, the projector 10 may communicate with, as the input device 16 , a remote controller that communicates with the main body of the projector 10 and that has the plurality of buttons described above.

The projection device 18 projects the output image Po indicated by the output image information PDo onto the projection surface SC. A configuration of the projection device 18 will be described with reference to FIG.

FIG. 6 is a diagram showing an example of the projection device 18. As shown in FIG. The projection device 18 includes a light source 181, three liquid crystal light valves 182R, 182G, and 182B that are examples of light modulation devices, a lens 183 that is an example of a projection optical system, a light valve driver 184, and the like. The projection device 18 modulates the light emitted from the light source 181 with the liquid crystal light valve 182 under the control of the control circuit 11 to generate modulated light, and enlarges and projects the output image Po from the lens 183 . The output image Po is displayed on the projection surface SC.

The light source 181 includes a light source section 181a formed from a xenon lamp, an extra-high pressure mercury lamp, an LED, a laser light source, or the like, and a reflector 181b that reduces variations in the direction of light emitted from the light source section 181a. LED is an abbreviation for Light Emitting Diode. The light emitted from the light source 181 has its luminance distribution reduced by an integrator optical system (not shown), and is then separated into the three primary colors of light, red, green, and blue, by a color separation optical system (not shown). The red, green, and blue color light components enter liquid crystal light valves 182R, 182G, and 182B, respectively.

The liquid crystal light valve 182 is composed of a liquid crystal panel or the like in which liquid crystal is sealed between a pair of transparent substrates. The liquid crystal light valve 182 is formed with a rectangular pixel region 182a composed of a plurality of pixels 182p arranged in a matrix. In the liquid crystal light valve 182, it is possible to apply a driving voltage to the liquid crystal for each pixel 182p. When the light valve driving section 184 applies a driving voltage corresponding to the output image information PDo to each pixel 182p, each pixel 182p is set to have a light transmittance corresponding to the output image information PDo. Therefore, the light emitted from the light source 181 is modulated by passing through the pixel region 182a, and the output image Po projected onto the projection surface SC is formed for each color light.

1.4. Functions of Projector 10 FIG. 7 is a diagram showing functions of the projector 10 . The control circuit 11 functions as a first correction processing execution unit 111, a second correction processing execution unit 112, and a projection control unit 113 by reading out a control program from the storage circuit 12 and executing the read control program.

The first correction processing execution unit 111 executes the first correction processing of multiplying the first lightness of the first color component having the highest lightness among the lightnesses of the plurality of color components included in the input pixel information PXi[m] indicating one pixel in the input image indicated by the input image information PDi by the first gain. In the first correction process, the first gamma correction is applied to the first color component by inputting the first lightness to the first gamma function γ1 having the lightness as a variable.

The second correction process executing unit 112 executes a second correction process of multiplying a second lightness of a second color component different from the first color component among the plurality of color components by a second gain. In the second correction process, the first lightness is input to the first gamma function γ1, and the first and second lightnesses are input to the second gamma function γ2 having lightness as a variable, thereby applying the second gamma correction to the second color component. Also, the second correction processing execution unit 112 executes the second correction processing for the third lightness of the third color component different from the first color component and the second color component.

In the following, for ease of explanation, it is assumed that the "first color component" having the highest lightness of the plurality of color components included in the input pixel information PXi[m] is the blue component, the "second color component" is the green component, and the "third color component" is the red component. Therefore, the brightness of the blue component corresponds to the "first brightness", the brightness of the green component corresponds to the "second brightness", and the brightness of the red component corresponds to the "third brightness". The first gamma function γ1 is an example of a "first correction function". The second gamma function γ2 is an example of a "second correction function". However, since the "first color component" is the color component with the highest brightness among the plurality of color components, the "first color component" is not always the blue component, and may be the green component or the red component. Also, when the "first color component" is the blue component, the "second color component" may be the red component.

As illustrated in FIG. 7, the memory circuit 12 stores a first LUT 121 and a second LUT 122. FIG. The first LUT 121 corresponds to the first gamma function γ1. A second LUT 122 corresponds to a second gamma function γ2. The first LUT 121 and the second LUT 122 are stored in the storage circuit 12 by the operation of the developer of the projector 10, for example.

The first correction process is a process of correcting the brightness Bi of the blue component included in the input pixel information PXi[m] using the following formula (1-3).

Bo=γ2(Bi)×γ1(MAXi)/γ2(MAXi) (1-3)

However, Bo indicates the lightness of the blue component included in the output pixel information PXo[m]. γ1( ) indicates the first gamma function γ1. γ2( ) indicates the second gamma function γ2. MAXi means the highest lightness among the lightnesses of a plurality of color components included in the input pixel information PXi[m], and is the lightness Bi of the blue component in the first embodiment. Therefore, since γ2(Bi) appears in the denominator and numerator on the right side of equation (1-3), equation (1-3) can be transformed into equation (1-4) below.

Bo=γ1(Bi) (1-4)

As shown in equation (1-4), the first correction process applies the first gamma correction to the blue component by inputting the brightness Bi, which is an example of the first brightness, to the first gamma function γ1. More specifically, the first correction process is a process of outputting the output value associated with the brightness Bi from the first LUT 121 as the brightness Bo.

The second correction process is a process of correcting the lightness Gi of the green component included in the input pixel information PXi[m] using the following formula (1-5).

Go=γ2(Gi)×γ1(MAXi)/γ2(MAXi) (1-5)

However, Go indicates the lightness of the green component included in the output pixel information PXo[m]. As shown in formula (1-5), the second correction process includes, as a coefficient, γ1 (MAXi) obtained by inputting the brightness Bi, in other words MAXi, into the first gamma function γ1, and the second gamma correction is applied to the green component by inputting the brightness Bi and the brightness Gi into the second gamma function γ2. More specifically, the second correction process acquires the output value associated with the brightness Gi and the output value associated with the brightness Bi from the second LUT 122, acquires the output value associated with the brightness Bi from the first LUT 121, and calculates the brightness Go by substituting the acquired three values into the equation (1-5). Note that "γ1(MAXi)" in the formula (1-5) is an example of "a value obtained by inputting the first lightness to the first correction function".

For the red component as well, the second correction process execution unit 112 performs the second correction process to correct the lightness Ri of the red component included in the input pixel information PXi[m] according to the following equation (1-6).

Ro=γ2(Ri)×γ1(MAXi)/γ2(MAXi) (1-6)

However, Ro indicates the lightness of the red component included in the output pixel information PXo[m]. As shown in equation (1-6), in the second correction process for the red component lightness Ri, the lightness Bi is input to the first gamma function γ1, and the lightness Bi and the lightness Ri are input to the second gamma function γ2, thereby applying the second gamma correction to the red component.

The projection control section 113 controls the projection device 18 . Specifically, the projection control unit 113 causes the projection device 18 to project the output image Po using the output pixel information PXo obtained by performing the first correction process and the second correction process on the input pixel information PXi. More specifically, the projection control unit 113 transmits output image information PDo representing the output image Po to the projection device 18 .

The projection device 18 projects the output image Po based on the output image information PDo. The first gamma function γ1 and the second gamma function γ2 will be explained using FIG.

1.5. Characteristics of First Gamma Function γ1 and Second Gamma Function γ2 FIG. 8 is a diagram for explaining the first gamma function γ1 and the second gamma function γ2. A graph 801 shown in FIG. 8 shows a display gamma characteristic gd, a first gamma characteristic g1, and a second gamma characteristic g2. The horizontal axis of the graph 801 indicates the brightness of the input pixel information PXi. The vertical axis of the graph 801 indicates the ratio [%] of the brightness of the output pixel information PXo to the maximum brightness that can be displayed by the projector 10 . The display gamma characteristic gd, the first gamma characteristic g1, and the second gamma characteristic g2 represent characteristics of different correction functions. The display gamma characteristic gd indicates the characteristic of the inverse function of the camera gamma function γc. Hereinafter, the inverse function of the camera gamma function γc will be referred to as "display gamma function γd". A first gamma characteristic g1 indicates a characteristic of the first gamma function γ1, and a second gamma characteristic g2 indicates a characteristic of the second gamma function γ2.

The display gamma function γd is an inverse function of the camera gamma function γc and is represented by the following formula (1-7).

where γd( ) represents the display gamma function γd. LiMAX is the maximum lightness that the input pixel information PXi can take, and is 1023 in the first embodiment. When γ is 0.45, 1/γ is 2.2. The first correction process uses the first gamma function γ1, and the second correction process uses the first gamma function γ1 and the second gamma function γ2. On the other hand, the display gamma function γd is shown in FIG. 8 for comparison with the first gamma function γ1 and the second gamma function γ2, and the control circuit 11 does not use the display gamma function γd.

As shown in FIG. 8, the display gamma function γd, the first gamma function γ1, and the second gamma function γ2 output the brightness of the output pixel information PXo as 0 when the brightness of the input pixel information PXi[m] is 0, and output the brightness of the output pixel information PXo[m] as the highest value when the brightness of the input pixel information PXi[m] is the highest value of 1023. Furthermore, the display gamma function γd, the first gamma function γ1, and the second gamma function γ2 are functions in which the brightness of the output pixel information PXo[m] monotonically increases as the brightness of the input pixel information PXi[m] increases. The slope of the display gamma function γd monotonously increases as the brightness of the input pixel information PXi[m] increases. The slope of the first gamma function γ1 monotonously increases when the brightness of the input pixel information PXi[m] ranges from 0 to Lg1, and monotonously decreases when the brightness of the input pixel information PXi[m] ranges from Lg1 to 1023, approaching 0. The slope of the first gamma function γ1 is approximately 0 when the lightness of the input pixel information PXi[m] is near the maximum value. The slope of the second gamma function γ2 monotonically increases when the brightness of the input pixel information PXi[m] ranges from 0 to Lg2, and decreases monotonously when the brightness of the input pixel information PXi[m] ranges from Lg2 to 1023. Lightness Lg1 is lower than lightness Lg2.

As illustrated in FIG. 8, when the same brightness is input to the first gamma function γ1, the second gamma function γ2, and the display gamma function γd, the brightness output from the first gamma function γ1 is higher than the brightness output from the second gamma function γ2, and the brightness output from the second gamma function γ2 is higher than the brightness output from the display gamma function γd. An example will be described in which the brightness of the blue component is the brightness Bi and the brightness of the green component is the brightness Gi in one piece of input pixel information PXi[m] included in the input image information PDi. As shown in FIG. 8, the brightness Bi is higher than the brightness Gi. The brightness B1 is obtained by inputting the brightness Bi into the first gamma function γ1. By inputting the brightness Bi to the first gamma function γ1, the first gamma function γ1 can be said to output the brightness B1 obtained by multiplying the brightness Bi by the first gain Ga1. The first gain Ga1 is B1/Bi. The brightness B2 is obtained by inputting the brightness Bi into the second gamma function γ2. The brightness Bd is obtained by inputting the brightness Bi into the display gamma function γd. As shown in FIG. 8, brightness B1 is higher than brightness B2, and brightness B2 is higher than brightness Bd.

Similarly, the brightness G1 is obtained by inputting the brightness Gi to the first gamma function γ1. The brightness G2 is obtained by inputting the brightness Gi to the second gamma function γ2. In the second correction process, as shown in equation (1-5), the brightness Bi is input to the first gamma function γ1, and the brightness Bi and the brightness Gi are input to the second gamma function γ2, thereby outputting the brightness Go by multiplying the brightness Gi by the second gain Ga2. The second gain Ga2 is smaller than the first gain Ga1. The brightness Gd is obtained by inputting the brightness Gi into the display gamma function γd. As shown in FIG. 8, the brightness G1 is higher than the brightness G2, and the brightness G2 is higher than the brightness Gd. In the example of FIG. 8, the brightness Go is a value between the brightness G1 and the brightness G2. The relationship between the first gamma function γ1 and the second gamma function γ2 will be further explained using FIG.

FIG. 9 is a diagram for explaining the relationship between the first gamma function γ1 and the second gamma function γ2. The relationship between the first gamma function γ1 and the second gamma function γ2 is shown using two pixels included in the input image indicated by the input image information PDi. Let the first pixel be the a-th pixel and the second pixel be the b-th pixel. a and b are integers different from each other and are 1 or more and M or less. Furthermore, it is assumed that the difference ΔLia between the blue component brightness Bi and the green component brightness Gi of the a-th pixel is greater than the difference ΔLib between the blue component brightness Bi and the green component brightness Gi of the b-th pixel. Hereinafter, the brightness Bi of the blue component included in the input pixel information PXi[m] may be referred to as brightness Bi[m], and the brightness G of the green component may be referred to as brightness Gi[m].

As shown in FIG. 9, as the difference between the blue component brightness Bi and the green component brightness Gi of the input pixel information PXi[m] is large, the difference between the blue component brightness B1 whose brightness Bi is corrected by the first gamma function γ1 and the green component brightness G2 whose brightness Gi is corrected by the second gamma function γ2 increases. Description will be made using more specific values. By inputting the brightness Bi[a] into the first gamma function γ1, the brightness B1[a] is obtained. By inputting the brightness Bi[b] into the first gamma function γ1, the brightness B1[b] is obtained. By inputting the brightness Gi[a] into the second gamma function γ2, the brightness G2[a] is obtained. By inputting the brightness Gi[b] into the second gamma function γ2, the brightness G2[b] is obtained. As illustrated in FIG. 9, the difference ΔLia between the brightness Bi[a] and the brightness Gi[a] is larger than the difference ΔLib between the brightness Bi[b] and the brightness Gi[b]. Note that in this specification, the difference is the absolute value of the difference between two values. Since the difference ΔLia is greater than the difference ΔLib, the difference ΔLa between the brightness B1[a] and the brightness G2[a] is greater than the difference ΔLb between the brightness B1[b] and the brightness G2[b].

The brightness Bi[a] is an example of the "seventh value", and the brightness B1[a] is an example of the "eighth value". The brightness Bi[b] is an example of the "ninth value", and the brightness B1[b] is an example of the "tenth value". The brightness Gi[a] is an example of the "eleventh value", and the brightness G2[a] is an example of the "twelfth value". The brightness Gi[b] is an example of the "13th value", and the brightness G2[b] is an example of the "14th value". The difference ΔLia is an example of "the difference between the seventh value and the eleventh value". The difference ΔLib is an example of "the difference between the ninth value and the thirteenth value". The difference ΔLa is an example of "the difference between the eighth value and the twelfth value". The difference ΔLb is an example of "the difference between the 10th value and the 14th value".

Returning to FIG. A situation in which the display gamma function γd is used will be described. If a display device having a maximum displayable brightness of 10000 nit or more displays an image based on the input image information PDi, by displaying the image indicated by the image information obtained by inputting the input image information PDi into the display gamma function γd, the original image indicated by the original image information PDg generated by the light receiving device 28 can be accurately reproduced. On the other hand, even if a display device having a maximum displayable brightness of less than 10000 nit, specifically the projector 10, projects an image indicated by image information obtained by inputting the input image information PDi to the display gamma function γd, the image projected onto the projection surface SC is darker than the original image as a whole.

Therefore, in order to brighten the image projected onto the projection surface SC, it is conceivable to correct the input image information PDi according to the characteristics of the first gamma function γ1 indicated by the first gamma characteristics g1. The first gamma correction can be said to be correction of the input image information PDi used for brightly displaying the output image Po. However, when the input image information PDi is corrected according to the characteristics of the first gamma function γ1, color reproducibility may deteriorate. Color reproducibility means the degree of matching between the pixel color indicated by the output pixel information PXo[m] and the pixel color indicated by the original pixel information PXg[m]. Specifically, the color reproducibility decreases as the lightness ratio of the plurality of color components included in the output pixel information PXo[m] deviates from the lightness ratio of the plurality of color components included in the original pixel information PXg[m].

An example of deterioration in color reproducibility will be described using the aforementioned brightness Bi and brightness Gi. If the input pixel information PXi is corrected using the display gamma function γd, the same information as the original pixel information PXg can be obtained. However, even if the input pixel information PXi is corrected using the display gamma function γd, it may not be exactly the same as the original pixel information PXg, but substantially the same information may be obtained due to rounding errors that may occur during correction. Inputting the brightness Bi into the display gamma function γd yields the brightness Bd. Inputting the brightness Gi into the display gamma function γd yields the brightness Gd. The ratio of the brightness of the green component to the brightness of the blue component in the input pixel information PXi is Gd:Bd, and the value of this ratio is Gd/Bd. Hereinafter, the value of the ratio of a given brightness to the highest brightness among the brightnesses of a plurality of color components may be referred to as "brightness ratio". In addition, when a color component with a certain brightness is a blue component, it may be described as "lightness ratio of blue component", when a color component with a certain brightness is a green component, it may be described as "lightness ratio of green component", and when a color component with a certain lightness is a red component, it may be described as "lightness ratio of red component". In the example of FIG. 8, the brightness ratio Gd/Bd of the green component obtained by correcting the display gamma function γd is about 54%. As the lightness ratio of the green component deviates from Gd/Bd, ie, about 54%, color reproducibility deteriorates. On the other hand, the brightness ratio of the green component indicated by the pixel information PX[m] after the output of the first gamma function γ1 is G1/B1. In the example of FIG. 8, G1/B1 is approximately 94%.

In the first embodiment, the first correction process corrects the lightness Bi to the lightness B1 according to the formula (1-4), and the second correction process corrects the lightness Gi to the lightness Go=G2×G1/B2 according to the formula (1-5). Therefore, in the first embodiment, the brightness ratio of the green component indicated by the output pixel information PXo[m] is (G2×G1/B2)/B1=(G2×G1)/(B1×B2). In the example of FIG. 8, (G2*G1)/(B1*B2) is about 74% and is closer to Gd/Bd compared to G1/B1. That is, according to the first embodiment, it is possible to improve the color reproducibility as compared with the mode in which only the first gamma function γ1 is used to correct the input pixel information PXi[m]. In the following description, "correcting the input pixel information PXi using only one gamma function" means correcting the output value obtained by inputting the lightness Bi into one gamma function as the lightness of the blue component, correcting the output value obtained by inputting the lightness Gi into the one gamma function as the lightness of the green component, and correcting the output value obtained by inputting the lightness Ri into the one gamma function as the lightness of the red component.

1.6. Operation of Projector 10 FIG. 10 is a flowchart showing the operation of the projector 10 . The flowchart shown in FIG. 10 operates regardless of whether the color component with the highest lightness among the lightnesses of the plurality of color components included in the input pixel information PXi[m] is a blue component, a green component, or a red component.

In step S<b>2 , the control circuit 11 acquires the input image information PDi from the communication device 13 . Next, in step S4, the control circuit 11 substitutes 1 for the variable m. Then, in step S6, the control circuit 11 specifies the brightness MAXi of the highest color component among the brightness Gi of the blue component, the brightness Gi of the green component, and the brightness Ri of the red component of the input pixel information PXi[m].

Next, in step S8, the control circuit 11 calculates the blue component brightness Bo of the output pixel information PXo[m] by inputting the blue component brightness Bi and the brightness MAXi of the input pixel information PXi[m] into the equation (1-3). After step S6, in step S10, the control circuit 11 calculates the green component brightness Go of the output pixel information PXo[m] by inputting the green component brightness Gi and the brightness MAXi of the input pixel information PXi[m] into the equation (1-5). After step S6, in step S12, the control circuit 11 calculates the red component brightness Bo of the output pixel information PXo[m] by inputting the red component brightness Ri and the brightness MAXi of the input pixel information PXi[m] into the equation (1-6).

Among the processing of step S8, the processing of step S10, and the processing of step S12, the processing of the steps related to the color component having the brightness MAXi is the first correction processing and corresponds to the first correction processing execution unit 111, and the processing of the remaining steps is the second correction processing and corresponds to the second correction processing execution unit 112. For example, when the brightness MAXi is the brightness Bi, the process of step S<b>8 is the first correction process and corresponds to the first correction process executing section 111 . The process of step S10 and the process of step S12 are the second correction process and correspond to the second correction process execution unit 112 .

After the processing of steps S8, S10, and S12 is completed, the control circuit 11 adds 1 to the variable m in step S14. Then, in step S16, the control circuit 11 determines whether or not the variable m is greater than M, which is the number of pieces of input pixel information PXi. If No in step S16, that is, if the variable m is M or less, the control circuit 11 returns the process to step S6. If Yes in step S16, the control circuit 11 outputs output image information PDo in step S18. In step S18, the control circuit 11 may correct the output image information PDo based on the three-dimensional LUT stored in the storage circuit 12 before outputting the output image information PDo. After completing the process of step S18, the control circuit 11 ends the series of processes shown in FIG.

The order of the flowcharts shown in FIG. 10 may be changed as long as there is no contradiction. For example, the control circuit 11 may execute the processing of step S8, the processing of step S10, and the processing of step S12 in any order or in parallel.

1.7. Summary of First Embodiment Hereinafter, a summary of the first embodiment will be described using an example in which the “first color component” is the blue component, the “second color component” is the green component, the “third color component” is the red component, the “first brightness” is the brightness Bi of the blue component, the “second brightness” is the brightness Gi of the green component, and the “third brightness” is the brightness Ri of the red component.

The display method performed by the projector 10 is to perform a first correction process of multiplying the brightness Bi by a first gain Ga1 among a plurality of color components included in input pixel information PXi[m] indicating a certain pixel in an input image composed of a plurality of pixels; and displaying an output image Po using the resulting output pixel information PXo.

According to the first embodiment, since the first gain Ga1 is greater than the second gain Ga2, it is possible to display the output image Po brighter than in the case where the correction process of multiplying the brightness Bi by the second gain Ga2 is executed. In addition, when the lightness of all of the plurality of color components is increased, overexposure tends to occur and color reproducibility tends to deteriorate. However, according to the first embodiment, since the second gain Ga2 is smaller than the first gain Ga1, it is possible to suppress deterioration in color reproducibility compared to the mode in which the correction process of multiplying the lightness Gi by the first gain Ga1 is executed.

In the first correction process, the blue component is subjected to the first gamma correction by inputting the brightness Bi to the first gamma function γ1 having the brightness as a variable. The second correction process includes applying a second gamma correction to the green component by inputting the lightness Gi to a second gamma function γ2 with lightness as a variable. More specifically, the second correction process applies the second gamma correction to the green component by inputting the brightness Gi and the brightness Bi into the second gamma function γ2 and the brightness Bi into the first gamma function γ1, as shown in equation (1-5). When the same brightness is input to the first gamma function γ1 and the second gamma function γ2, the brightness output from the first gamma function γ1 is higher than the brightness output from the second gamma function γ2.

According to the first embodiment, in the first correction process, by correcting the highest brightness Bi using the first gamma function γ1, the output image Po can be displayed brighter than when the brightness Bi is corrected using the second gamma function γ2. Furthermore, according to the first embodiment, in the second correction process, by correcting the lightness Gi using the second gamma function γ2, it is possible to suppress deterioration in color reproducibility compared to correcting the input pixel information PXi using only the first gamma function γ1. In particular, when the lightness of a plurality of color components included in the input pixel information PXi is high to some extent, in a mode in which only the first gamma function γ1 is used to correct the input pixel information PXi, a phenomenon in which the gradation of bright portions is lost, so-called whiteout occurs, and color reproducibility deteriorates.

Further, the first correction processing includes outputting corrected brightness B1 by inputting brightness Bi to the first gamma function γ1. Further, if the lightness output by inputting the lightness Gi to the second gamma function γ2 is lightness G2, the lightness output by inputting the lightness Bi to the second gamma function γ2 is lightness B2, and the lightness of the green component after correction by the second correction process is lightness Go, the second correction process outputs the lightness Go according to the following equation (1-8). The formula (1-8) matches the formula (1-5) in which γ2(Gi) is replaced by G2, γ1(MAXi) is replaced by B1, and γ2(MAXi) is replaced by B2.

Go=G2×B1/B2 (1-8)

The brightness B1/brightness B2 shown in the formula (1-8) is a value greater than 1 as shown in FIG. In the mode in which the lightness R2 is the lightness after correction in the second correction process, the output image Po tends to be dark. Therefore, by multiplying the lightness G2 by the lightness B1/lightness B2, which is a value greater than 1, the output image Po can be displayed brighter than in the case where the lightness G2 is the lightness after correction in the second correction process while suppressing the deterioration of the color reproducibility.

In addition, a generalized equation of equation (1-8) that can be applied to any of the plurality of color components having the highest lightness is described as equation (1-9) below. The first correction process includes outputting the corrected first lightness by inputting the first lightness to the first gamma function γ1. Let γ2B be the lightness output when the second lightness is input to the second gamma function γ2, γ1A be the first lightness after correction, γ2A be the lightness output when the first lightness is input to the second gamma function γ2, and L2 be the second lightness after correction.

L2=γ2B×γ1A/γ2A (1-9)

The input image indicated by the input image information PDi is an image obtained by correcting the original image using the camera gamma function γc whose variable is the brightness of the original image indicated by the original image information PDg. The second gain Ga2 is between the gain when the brightness Gi is corrected by the first correction process and the inverse function of the camera gamma function γc, that is, the gain when the second brightness is input to the display gamma function γd. In other words, using FIG. 8, the brightness Go is between the brightness G1 and the brightness Gd.

According to the first embodiment, since the lightness Go is higher than the lightness Gd, it is possible to display the output image Po brighter than when the input pixel information PXi is corrected using only the display gamma function γd for the lightness Gi. Furthermore, since the lightness Go is lower than the lightness G1, it is possible to suppress deterioration in color reproducibility compared to the mode of correcting the input pixel information PXi using only the first gamma function γ1 for the lightness Gi.

As described above, the plurality of color components are a blue component, a green component, and a red component, and the display method performed by the projector 10 further includes performing a second correction process on the brightness Ri of the red component.

According to the first embodiment, the processing can be simplified compared to the aspect of correcting the input pixel information PXi for the lightness Ri of the red component by a correction process different from the first correction process and the second correction process.

Further, as shown in FIG. 9, the first gamma function γ1 corrects the brightness Bi[a] to the brightness B1[a] when the brightness Bi is the brightness Bi[a], and corrects the brightness Bi[b] to the brightness B1[b] when the brightness Bi is the brightness Bi[b]. The second gamma function γ2 corrects the lightness Gi[a] to the lightness G2[a] when the lightness Gi is the lightness Gi[a], and corrects the lightness Gi[b] to the lightness G2[b] when the lightness Gi is the lightness Gi[b]. When the difference ΔLia between the lightnesses Bi[a] and Gi[a] is greater than the difference ΔLib between the lightnesses Bi[b] and Gi[b], the difference ΔLa between the lightnesses B1[a] and G2[a] is greater than the difference ΔLb between the lightnesses B1[b] and G2[b].

If the difference ΔLia is larger than the difference ΔLib, that is, if the difference in brightness within the pixel is large in the input image information PDi, the difference ΔLa is larger than the difference ΔLb, that is, the difference in brightness within the pixel can also be increased in the output image information PDo.

2. 2nd Embodiment Hereinafter, 2nd Embodiment of this invention is described. In the embodiments exemplified below, the reference numerals used in the description of the first embodiment are used for the elements whose actions and functions are the same as those of the first embodiment, and the detailed description of each element is appropriately omitted. In the first embodiment, the blue component brightness Bi, the green component brightness Gi, and the red component brightness Ri are corrected based on equations (1-3), (1-5), and (1-6), respectively. On the other hand, in the second embodiment, when the change in gradation of the original image is constant, the change in gradation of the output image Po can approach a constant change.

2.1. Functions of Projector 10a FIG. 11 is a diagram showing functions of the projector 10a according to the second embodiment. The projector 10 a differs from the projector 10 in that it has a control circuit 11 a instead of the control circuit 11 . The control circuit 11a is different from the control circuit 11 in that it functions as a first correction process execution section 111a instead of the first correction process execution section 111, and functions as a second correction process execution section 112a instead of the second correction process execution section 112.

In the second embodiment as well, it is assumed that the "first color component" having the highest brightness among the plurality of color components is the blue component, the "second color component" is the green component, and the "third color component" is the red component.

The first correction processing execution unit 111a corrects the brightness Bi of the blue component included in the input pixel information PXi[m] according to the following formula (2-1).

Bo=Xb×(1−V ⁴ )+γ1(Bi) (2−1)

The factor Xb is a correction factor for the blue component. The value V is a value obtained by normalizing the highest brightness included in the input pixel information PXi[m]. The value V is a real number between 0 and 1 inclusive. The value V has the following two aspects. The value V in the first mode is the ratio of the highest lightness among the lightnesses of the plurality of color components of the output pixel information PXo[m] to the maximum lightness that the input pixel information PXi[m] can take. For example, when the maximum possible brightness of the input pixel information PXi[m] is 1023 and the highest brightness among the multiple color components of the output pixel information PXo[m] is 850, the value V is approximately 0.83. The value V in the second mode is the ratio of the value obtained when the highest lightness among the lightnesses of the plurality of color components of the output pixel information PXo[m] is input to the first gamma function γ1 with respect to the maximum lightness that the output pixel information PXo[m] can take. In the following description, the value V is described as being the first aspect. The first correction processing execution unit 111a obtains the coefficient Xb according to the following formula (2-2).

Xb=γ2(Bi)×γ1(MAXi)/γ2(MAXi)−γ1(Bi) (2-2)

In the second embodiment, as in the first embodiment, MAXi means the highest lightness among the lightnesses of a plurality of color components included in the input pixel information PXi[m], and in the second embodiment, it is the lightness Bi of the blue component. Therefore, the first term of the formula (2-2) is γ1(Bi), so the coefficient Xb is 0. Since the coefficient Xb is 0, the formula (2-1) can be transformed into the above formula (1-4).

The second correction processing execution unit 112a executes processing for correcting the lightness Gi of the green component included in the input pixel information PXi[m] according to the following equation (2-3) by the second correction processing.

Go=Xg×(1−V ⁴ )+γ1(Gi) (2−3)

The factor Xg is the correction factor for the green component. The second correction processing execution unit 112a obtains the coefficient Xg according to the following formula (2-4).

Xg=γ2(Gi)×γ1(MAXi)/γ2(MAXi)−γ1(Gi) (2-4)

The first term of equation (2-4) is the same as the right side of equation (1-5). As can be understood from the formulas (2-3) and (2-4), as the value V approaches 0, the brightness Go in the second embodiment approaches the brightness Go in the first embodiment. On the other hand, as the value V approaches 1, the brightness Go in the second embodiment approaches γ1(Gi). In other words, the brightness Go in the second embodiment approaches γ1(Gi) as the highest brightness included in the input pixel information PXi[m] increases.

The second correction process execution unit 112a executes the process of correcting the lightness Ri of the red component included in the input pixel information PXi[m] according to the following equation (2-5) by the second correction process.

Ro=Xr×(1−V ⁴ )+γ1(Ri) (2−5)

The coefficient Xr is a correction coefficient for the red component. The second correction processing execution unit 112a obtains the coefficient Xr according to the following formula (2-6).

Xr=γ2(Ri)×γ1(MAXi)/γ2(MAXi)−γ1(Ri) (2-6)

An example of correction by the second correction processing execution unit 112a will be described with reference to FIG.

FIG. 12 is a diagram for explaining a correction example of the second correction processing execution unit 112a. A correction example of the second correction processing execution unit 112a will be described using two pixels included in the input image indicated by the input image information PDi. Let the first pixel be the c-th pixel and the second pixel be the d-th pixel. c and d are integers different from each other and are 1 or more and M or less. Furthermore, the brightness Bi[d] is higher than the brightness Bi[c]. Furthermore, the brightness Gi[c] is the same value as the brightness Gi[d].

In the second embodiment, as the highest lightness included in the input pixel information PXi[m] increases, the lightness Go in the second embodiment approaches γ1(Gi). Description will be made using more specific values. By inputting the brightness Bi[c] into the first gamma function γ1, the brightness B1[c] is obtained. By inputting the brightness Bi[c] into the second gamma function γ2, the brightness B2[c] is obtained. By inputting the brightness Gi[c] into the first gamma function γ1, the brightness G1[c] is obtained. By inputting the brightness Gi[c] into the second gamma function γ2, the brightness G2[c] is obtained. By inputting the brightness Bi[d] into the first gamma function γ1, the brightness B1[d] is obtained. By inputting the brightness Bi[d] into the second gamma function γ2, the brightness B2[d] is obtained. By inputting the brightness Gi[d] into the first gamma function γ1, the brightness G1[d] is obtained. By inputting the brightness Gi[d] into the second gamma function γ2, the brightness G2[d] is obtained. Since the lightness Gi[d] is the same value as the lightness Gi[c], the lightness G1[d] is the same value as the lightness G1[c], and the lightness G2[d] is the same value as the lightness G2[c].

The second correction processing execution unit 112a uses equations (2-3) and (2-4) to calculate the green component brightness Go[c] included in the output pixel information PXo[c] and the green component brightness Go[d] included in the output pixel information PXo[d]. In calculating the brightness Go[c], the value V in the equation (2-3) is Bi[c]/1023. Similarly, in calculating the brightness Go[d], the value V in the equation (2-3) is Bi[d]/1023. As shown in FIG. 12, the difference ΔLd between the lightness G1[d] and the lightness Go[d] is smaller than the difference ΔLc between the lightness G1[c] and the lightness Go[c].

Note that the brightness Bi[c] is an example of the "first value". The brightness Gi[c] and the brightness Gi[d] are examples of the "second value". Brightness Go[c] is an example of the “third value”. Brightness Bi[d] is an example of the "fourth value". Brightness Go[d] is an example of the “fifth value”. The brightness G1[c] and the brightness G2[d] are examples of the "sixth value".

2.2. Operation of Projector 10a FIG. 13 is a flowchart showing the operation of the projector 10a. The flowchart shown in FIG. 13 operates regardless of whether the color component with the highest brightness among the brightness of the plurality of color components included in the input pixel information PXi[m] is a blue component, a green component, or a red component.

In step S<b>22 , the control circuit 11 a acquires the input image information PDi from the communication device 13 . Next, in step S24, the control circuit 11a substitutes 1 for the variable m. Then, in step S26, the control circuit 11a specifies the brightness MAXi of the highest color component among the brightness Gi of the blue component, the brightness Gi of the green component, and the brightness Ri of the red component of the input pixel information PXi[m].

Next, in step S28, the control circuit 11a calculates the value V, the coefficient Xb, the coefficient Xg, and the coefficient Xr. Specifically, the control circuit 11a calculates MAXi/1023 as the value V, calculates the coefficient Xb based on the formula (2-2), calculates the coefficient Xg based on the formula (2-4), and calculates the coefficient Xr based on the formula (2-6).

After the process of step S28 is completed, in step S30, the control circuit 11a calculates the blue component brightness Bo of the output pixel information PXo[m] by inputting the blue component brightness Bi of the input pixel information PXi[m], the coefficient Xb, and the value V into equation (2-1). After step S28, in step S32, the control circuit 11a calculates the green component brightness Go of the output pixel information PXo[m] by inputting the green component brightness Gi of the input pixel information PXi[m], the coefficient Xg, and the value V into equation (2-3). Further, after step S28, in step S34, the control circuit 11a calculates the red component brightness Ro of the output pixel information PXo[m] by inputting the red component brightness Ri of the input pixel information PXi[m], the coefficient Xr, and the value V into the equation (2-5).

After the processing of steps S30, S32, and S34 is completed, the control circuit 11a adds 1 to the variable m in step S36. Then, in step S38, the control circuit 11a determines whether or not the variable m is greater than M, which is the number of pieces of pixel information PX. If No in step S38, that is, if the variable m is M or less, the control circuit 11a returns the process to step S26. If Yes in step S38, the control circuit 11a outputs output image information PDo in step S40. In step S40, the control circuit 11a may correct the output image information PDo based on the three-dimensional LUT stored in the storage circuit 12 before outputting the output image information PDo. After completing the process of step S40, the control circuit 11 ends the series of processes shown in FIG.

As with the flowchart shown in FIG. 13, the order of the flowchart shown in FIG. 10 may be changed as long as there is no contradiction.

2.3. Summary of Second Embodiment Hereinafter, a summary of the second embodiment will be described using an example in which the “first color component” is the blue component, the “second color component” is the green component, the “third color component” is the red component, the “first brightness” is the brightness Bi of the blue component, the “second brightness” is the brightness Gi of the green component, and the “third brightness” is the brightness Ri of the red component.

As shown in FIG. 12, the difference ΔLd between the lightness G1[d] and the lightness Go[d] is smaller than the difference ΔLc between the lightness G1[c] and the lightness Go[c]. That is, in the second embodiment, according to the highest brightness among the blue component brightness Bi, the green component brightness Gi, and the red component brightness Ri, the corrected values of the brightnesses other than the highest brightness approach the values corrected only by the first gamma function γ1.

As shown in FIG. 12, the first gamma function γ1 has the following two features. The first feature is that the slope of the first gamma function γ1 is approximately 0 near 1023, which is the maximum lightness value of the input pixel information PXi[m]. That is, when the lightness of the input pixel information PXi"m" is near the maximum value, the output value of the first gamma function γ1 is substantially the same value. The second feature is that the slope of the first gamma function γ1 is greater from the vicinity of 512, where the lightness of the input pixel information PXi“m” is medium, to the vicinity of the maximum value, compared to the vicinity of the maximum value. If the brightness Gi is corrected according to the first embodiment, the value obtained by inputting the brightness Bi to the first gamma function γ1 is included in the formula (1-5). Therefore, the change in the brightness Go is steep from the intermediate level to the vicinity of the maximum value of the brightness Bi, while the change in the brightness Go is almost flat near the maximum value of the brightness Bi. Therefore, even if the change in gradation is constant in the original image, the change in gradation fluctuates in the output image Po according to the first embodiment, resulting in deterioration of the image quality of the output image Po.

In the second embodiment, even when the brightness Bi is near the maximum value, the value of the first term of the formula (2-3) changes depending on the value V, as shown in the formula (2-3). Therefore, according to the second embodiment, compared with the first embodiment, even if the brightness Bi is near the maximum value, the change in the brightness Go can be increased. More specifically, it is assumed that there are two luminosities Bi[e] and luminosity Bi[f] near the highest luminosity, the luminosity Bi[f] is higher than the luminosity Bi[e], and the luminosity Gi[e] has the same value as the luminosity Gi[f]. e and f are integers different from each other and are integers of 1 or more and M or less. The lightness Go[f] is calculated as a value closer to the value obtained by inputting the lightness Gi into the first gamma function γ1 than the lightness Go[e]. As described above, when the change in gradation is constant in the original image, the output image Po in the second embodiment has a more constant change in gradation than in the first embodiment, so the image quality of the output image Po can be improved.

3. Numerical Examples Specific numerical examples of brightness in each of the display gamma function γd, the first gamma function γ1, the second gamma function γ2, the first embodiment, and the second embodiment will be described with reference to FIG.

FIG. 14 is a diagram showing a specific example of lightness after correction. FIG. 14 illustrates a correction example in which the input pixel information PXi[m] indicating one pixel has a blue component with a brightness of 850, a green component with a brightness of 768, and a red component with a brightness of 660. FIG. Note that the value obtained when the lightness is input to the first gamma function γ1 or the second gamma function γ2 is also lightness, but in FIG. 14, in order to facilitate comparison among a plurality of color components, the ratio of the value obtained when the lightness is input to the first gamma function γ1 or the second gamma function γ2 to the maximum lightness that the output pixel information PXo[m] can take is shown.

As shown in FIG. 14, by inputting the brightness of the blue component, the brightness of the green component, and the brightness of the red component of the input pixel information PXi[m] to the display gamma function γd, 30%, 10%, and 5% are obtained, respectively. By inputting the brightness of the blue component, the brightness of the green component, and the brightness of the red component of the input pixel information PXi[m] to the first gamma function γ1, 95%, 80%, and 60% are obtained, respectively. By inputting the brightness of the blue component, the brightness of the green component, and the brightness of the red component of the input pixel information PXi[m] to the second gamma function γ2, 85%, 50%, and 20% are obtained, respectively. According to the first embodiment, the brightness of the blue component, the brightness of the green component, and the brightness of the red component of the input pixel information PXi[m] are corrected to 95.0%, 55.9%, and 22.4%, respectively. According to the second embodiment, the brightness of the blue component, the brightness of the green component, and the brightness of the red component of the input pixel information PXi[m] are corrected to 95.0%, 67.4%, and 40.3%, respectively.

As shown in FIG. 14, 95%, which is the brightness of the blue component after correction in the first embodiment, is higher than 85%, which is the brightness of the blue component after correction by the second gamma function γ2. Therefore, according to the first embodiment, the output image Po can be displayed brighter than when the correction process of multiplying the brightness Bi by the second gain Ga2 is executed. Since the lightness of the blue component after correction in the second embodiment is also the same value as the lightness of the blue component after correction in the first embodiment, according to the second embodiment, the output image Po can be displayed brighter than when the correction process is performed by multiplying the lightness Bi by the second gain Ga2. A brightness ratio based on the numerical values in FIG. 14 will be described with reference to FIG.

FIG. 15 is a diagram showing brightness ratios based on the numerical values in FIG. As shown in FIG. 15, the brightness ratio of the blue component in the display gamma function γd is 100%, the brightness ratio of the green component is 33%, and the brightness ratio of the red component is 17%. The brightness ratio of the blue component in the first gamma function γ1 is 100%, the brightness ratio of the green component is 84%, and the brightness ratio of the red component is 63%. The brightness ratio of the blue component in the second gamma function γ2 is 100%, the brightness ratio of the green component is 59%, and the brightness ratio of the red component is 24%. The brightness ratio of the blue component in the first embodiment is 100%, the brightness ratio of the green component is 59%, and the brightness ratio of the red component is 24%. The lightness ratio of the blue component in the second embodiment is 100%, the lightness ratio of the green component is 71%, and the lightness ratio of the red component is 42%.

As shown in FIG. 15, 59%, which is the brightness ratio of the green component after correction in the first embodiment, is closer to 33%, which is the brightness ratio of the green component after correction by the display gamma function γd, compared to 84%, which is the brightness ratio of the green component after correction by the first gamma function γ1. According to the first embodiment, it is possible to suppress deterioration in color reproducibility compared to a mode in which the correction process of multiplying the lightness Gi by the first gain Ga1 is executed. Similarly, 24%, which is the lightness ratio of the red component after correction in the first embodiment, is closer to 17%, which is the lightness ratio of the red component after correction by the display gamma function γd, compared to 63%, which is the lightness ratio of the red component after correction by the first gamma function γ1.

Further, 71%, which is the lightness ratio of the green component after correction in the second embodiment, is closer to 33%, which is the lightness ratio of the green component after correction by the display gamma function γd, compared to 84%, which is the lightness ratio of the green component after correction by the first gamma function γ1. According to the second embodiment, it is possible to suppress deterioration in color reproducibility compared to the mode of executing the correction process of multiplying the lightness Gi by the first gain Ga1. Similarly, 42%, which is the lightness ratio of the red component after correction in the second embodiment, is closer to 17%, which is the lightness ratio of the red component after correction by the display gamma function γd, compared to 63%, which is the lightness ratio of the red component after correction by the first gamma function γ1.

In the above description, the ability to suppress deterioration in color reproducibility according to the first and second embodiments has been described using the lightness ratio, but it can also be described using hue and saturation. It can be said that deterioration in color reproducibility can be further suppressed as one or both of the hue and saturation of the pixel after correction approaches one or both of the hue and saturation of the pixel corrected by the display gamma function γd. The hue of a certain pixel is obtained by the following formula (3-1). The unit of hue obtained by the formula (3-1) is indicated by the frequency method. However, formula (3-1) assumes that among the blue component brightness B, the green component brightness G, and the red/blue component brightness R included in certain pixel information PX, the blue component brightness B is the highest, the green component brightness G is the second highest, and the red component brightness R is the lowest.

However, H indicates the hue of a certain pixel. Also, the saturation of a certain pixel is obtained by the following formula (3-2).

S=MAX-MIN/MAX (3-2)

However, S indicates the saturation of a certain pixel. MAX indicates the highest lightness among the lightness B of the blue component, the lightness G of the green component, and the lightness R of the red/blue component included in the pixel information PX indicating a certain pixel. MIN indicates the lowest lightness among the lightness B of the blue component, the lightness G of the green component, and the lightness R of the red/blue component included in certain pixel information PX.

The difference between the hue of the pixel indicated by the output pixel information PXo[m] and the hue of the pixel indicated by the original pixel information PXg[m] is smaller than the difference between the hue of the pixel indicated by the first pixel information PX1 and the hue of the pixel indicated by the original pixel information PXg[m]. The first pixel information PX1 is information obtained by correcting the input pixel information PXi[m] only by the first gamma function γ1. That is, the first pixel information PX1 is information obtained when the first gamma correction is applied to the blue component by inputting the brightness Bi [m] to the first gamma function γ1, the first gamma correction is applied to the green component by inputting the brightness Gi [m] to the first gamma function γ1, and the first gamma correction is applied to the red component by inputting the brightness Ri [m] to the first gamma function γ1. Also, the difference between the saturation of the pixel indicated by the output pixel information PXo[m] and the saturation of the pixel indicated by the original pixel information PXg[m] is smaller than the difference between the saturation of the pixel indicated by the first pixel information PX1 and the saturation of the pixel indicated by the original pixel information PXg[m].

The pixel indicated by the output pixel information PXo[m] corresponds to the input pixel information PXi[m] and corresponds to "the pixel corresponding to one pixel in the input image indicated by the output pixel information". That the first pixel in one image corresponds to the second pixel in the other image means that the position of the first pixel in one image is the same as the position of the second image in the other image. The pixel indicated by the original pixel information PXg[m] corresponds to the input pixel information PXi[m] and corresponds to "a pixel in the first image that corresponds to one pixel in the input image". A pixel indicated by the first pixel information PX1 corresponds to the input pixel information PXi[m], and corresponds to "a pixel corresponding to one pixel in the input image indicated by the first pixel information".

Based on the numerical examples shown in FIG. 14, the hue determined using equation (3-1) and the saturation determined using equation (3-2) will be described with reference to FIG.

FIG. 16 is a diagram showing a specific example of hue and saturation. As shown in FIG. 16, the hue of the pixel obtained by correcting the input pixel information PXi[m] only by the display gamma function γd is 228 degrees and the saturation is 0.83. A pixel obtained by correcting the input pixel information PXi[m] only by the display gamma function γd corresponds to the pixel indicated by the original pixel information PXg[m].

The first pixel information PX1 obtained by correcting the input pixel information PXi[m] only by the first gamma function γ1 has a hue of 205.7 degrees and a saturation of 0.37. A pixel whose input pixel information PXi[m] is corrected only by the second gamma function γ2 has a hue of 212.3 degrees and a saturation of 0.76. The hue of the pixel indicated by the output pixel information PXo[m] obtained by correcting the input pixel information PXi[m] according to the first embodiment is 212.3 degrees and the saturation is 0.76. The hue of the pixel indicated by the output pixel information PXo[m] obtained by correcting the input pixel information PXi[m] according to the second embodiment is 210.3 degrees and the saturation is 0.58.

In the first embodiment, the difference between the hue of the pixel indicated by the output pixel information PXo[m] and the pixel obtained by correcting the input pixel information PXi[m] only by the display gamma function γd, that is, the hue of the pixel indicated by the original pixel information PXg[m] is |212.3-228|, which is 15.7 degrees. |x| means the absolute value of x. On the other hand, the difference between the hue of the pixel indicated by the first pixel information PX1 and the hue of the pixel indicated by the original pixel information PXg[m] is 22.3 degrees from |205.7-228|. Therefore, the hue of the pixel indicated by the output pixel information PXo[m] in the first embodiment is closer to the hue of the pixel indicated by the original pixel information PXg[m] than the hue of the pixel indicated by the first pixel information PX1. Also, the difference between the saturation of the pixel indicated by the output pixel information PXo[m] and the saturation of the pixel indicated by the original pixel information PXg[m] is |0.76−0.83|, which is 0.07. On the other hand, the saturation of the pixel indicated by the first pixel information PX1 and the saturation of the pixel indicated by the original pixel information PXg[m] are |0.37−0.83|, so 0.46. Therefore, the saturation of the pixel indicated by the output pixel information PXo[m] in the first embodiment is closer to the saturation of the pixel indicated by the original pixel information PXg[m] than the saturation of the pixel indicated by the first pixel information PX1. As described above, the pixels indicated by the output pixel information PXo[m] in the first embodiment can have improved hue reproducibility and chroma reproducibility compared to the pixels indicated by the first pixel information PX1.

In the second embodiment, the difference between the hue of the pixel indicated by the output pixel information PXo[m] and the pixel obtained by correcting the input pixel information PXi[m] only by the display gamma function γd, that is, the hue of the pixel indicated by the original pixel information PXg[m] is |210.3-228|, which is 17.7 degrees. Therefore, the hue of the pixel indicated by the output pixel information PXo[m] in the second embodiment is closer to the hue of the pixel indicated by the original pixel information PXg[m] than the hue of the pixel indicated by the first pixel information PX1. Also, the difference between the saturation of the pixel indicated by the output pixel information PXo[m] and the saturation of the pixel indicated by the original pixel information PXg[m] is |0.58−0.83|, which is 0.25. On the other hand, the saturation of the pixel indicated by the first pixel information PX1 and the saturation of the pixel indicated by the original pixel information PXg[m] are 0.46. Therefore, the saturation of the pixel indicated by the output pixel information PXo[m] in the second embodiment is closer to the saturation of the pixel indicated by the original pixel information PXg[m] than the saturation of the pixel indicated by the first pixel information PX1. As described above, the pixels indicated by the output pixel information PXo[m] in the second embodiment can have improved hue reproducibility and saturation reproducibility compared to the pixels indicated by the first pixel information PX1.

4. Modifications Each of the above forms can be modified in various ways. Specific modification modes are exemplified below. Two or more aspects arbitrarily selected from the following examples can be combined as appropriate within a mutually consistent range. It should be noted that, in the modifications illustrated below, the reference numerals referred to in the above description will be used for the elements that have the same actions and functions as those of the embodiment, and the detailed description of each will be omitted as appropriate.

4.1. First Modification In the first embodiment, the second correction process is described as inputting the lightness Gi and the lightness Bi into the second gamma function γ2 and the lightness Bi into the first gamma function γ1 as shown in equation (1-5), thereby applying the second gamma correction to the green component. However, this is not the only option. For example, the second correction process may apply the second gamma correction to the green component only by inputting the lightness Gi to the second gamma function γ2 having the lightness as a variable. Specifically, the second correction process applies the second gamma correction to the green component according to the following formula (4-1).

Go=γ2(Gi) (4-1)

Similarly, the second correction process applies the second gamma correction to the red component according to the following formula (4-1).

Ro=γ2(Ri) (4-2)

Even in the first modified example, similarly to the first embodiment, in the second correction process, the second gamma function γ2 is used to correct the lightness Gi, thereby suppressing deterioration in color reproducibility compared to the mode in which only the first gamma function γ1 is used to correct the input pixel information PXi.

4.2. Second Modification In each aspect described above, the first LUT 121 shows the correspondence relationship between all possible input values of the first gamma function γ1 and the output values obtained when each of these input values is input to the first gamma function γ1, but the present invention is not limited to this. For example, the first LUT 121 may indicate a correspondence relationship between a partial input value among all possible input values of the first gamma function γ1 and an output value obtained when each of the partial input values is input to the first gamma function γ1. When calculating the formula (1-3), the first correction process execution unit 111, if there is a value that matches the brightness Bi among some of the input values included in the first LUT 121, outputs the output value corresponding to the input value as the output result of the formula (1-3). On the other hand, if the input value of the first LUT 121 does not have a value that matches the brightness Bi, the first correction processing execution unit 111 outputs a value obtained by performing interpolation processing based on a value close to the brightness Bi among some of the input values included in the first LUT 121, as the output result of equation (1-3). Interpolation processing includes linear interpolation, cubic spline interpolation, and the like. Although the above description describes the first LUT 121, the same applies to the second LUT 122 as well.

4.3. Third Modification In each aspect described above, it is assumed that the maximum brightness displayable by the projector 10 is a fixed value, but the maximum brightness displayable by the projector 10 may vary. The control circuit 11 may select the first gamma function γ1 from a plurality of gamma functions that are candidates for the first gamma function γ1. Each of the plurality of gamma functions has a one-to-one correspondence with the maximum brightness that can be displayed by the projector 10 .

A specific aspect of the third modification will be described. For example, the storage circuit 12 stores LUTs corresponding to each of a plurality of gamma functions that are candidates for the first gamma function γ1. Alternatively, the storage circuit 12 may store LUTs corresponding to each of a predetermined number of gamma functions among the plurality of gamma functions. When a gamma function other than the gamma function corresponding to the LUT stored in the storage circuit 12 is selected as the first gamma function γ1, the control circuit 11 generates the LUT corresponding to the first gamma function γ1 based on the selected gamma function or the LUT stored in the storage circuit 12. When generating the LUT corresponding to the first gamma function γ1 based on the LUTs stored in the storage circuit 12, the control circuit 11 selects, for example, two LUTs from among the plurality of LUTs stored in the storage circuit 12, and performs interpolation processing based on the selected two LUTs to generate the LUT corresponding to the first gamma function γ1. When generating the LUT corresponding to the first gamma function γ1, the control circuit 11 may generate an LUT indicating the correspondence between all possible input values of the first gamma function γ1 and the output values obtained when each of these input values are input to the first gamma function γ1, or LUT indicating the correspondence between some of the possible input values of the first gamma function γ1 and the output values obtained when each of these partial input values are input to the first gamma function γ1. UT may be generated.

There are the following two aspects regarding which gamma function to select as the first gamma function γ1 from among the plurality of gamma functions. In the first mode, the control circuit 11 selects the first gamma function γ1 from the plurality of gamma functions according to the user's operation of the projector 10 . In the second mode, the control circuit 11 identifies the maximum brightness that can be displayed by the projector 10 at present, and selects the gamma function corresponding to the identified maximum brightness as the first gamma function γ1. As a method of specifying the maximum brightness that can be displayed by the projector 10, for example, it can be specified from the focus position of the output image Po. For example, the projector 10 has a focus lens, and adjusts the focus position of the output image Po by moving the focus lens along the optical axis of the output image Po. The control circuit 11 identifies the focus position of the output image Po based on the position of the focus lens.

4.4. Fourth Modification In each aspect described above, the device that provides the input image information PDi to the projector 10 is not limited to the digital camera 20, and may be a PC, a smartphone, or the like. PC is an abbreviation for Personal Computer.

4.5. Fifth Modification In each aspect described above, it was described that the input image information PDi conforms to HDR10, but the present invention is not limited to this. For example, the input image information PDi may conform to HDR10+ or may conform to SDR. SDR is an abbreviation for Standard Dynamic Range.

4.6. Sixth Modification Although the liquid crystal light valve 182 is used as the light modulation device in the projection device 18 in each aspect described above, the light modulation device is not limited to the liquid crystal light valve 182 and can be changed as appropriate. For example, the light modulation device may be configured using three reflective liquid crystal panels. Further, the optical modulation device may have a configuration using one liquid crystal panel, a method using three digital mirror devices, a method using one digital mirror device, or the like. If only one liquid crystal panel or digital mirror device is used as the light modulation device, members corresponding to the color separating optical system and the color synthesizing optical system are unnecessary. In addition to liquid crystal panels and digital mirror devices, a configuration capable of modulating light emitted from a light source can also be employed as a light modulation device.

4.7. Seventh Modification In each aspect described above, the projector 10 is an example of the “display device”, but the invention is not limited to this. For example, another example of the display device may be an organic EL display or a liquid crystal display. EL is an abbreviation for Electro Luminescence.

In each aspect described above, all or part of the elements realized by the control circuit 11 executing the control program may be realized in hardware by an electronic circuit such as FPGA or ASIC, or may be realized by cooperation between software and hardware. FPGA is an abbreviation for Field Programmable Gate Array. ASIC is an abbreviation for Application Specific IC.

Reference Signs List 1 display system 10, 10a projector 11, 11a control circuit 12 storage circuit 13 communication device 16 input device 18 projection device 19 bus 20 digital camera 21 control circuit 22 storage circuit 23 communication device 26 input device 27 output device 28 light receiving device 29 bus 111, 111a first correction processing execution unit 112, 112a second correction processing execution unit 113 projection control unit 121 first LUT 122 first LUT 181 light source 181a light source unit 181b reflector 182, 182B, 182G, 182R liquid crystal light valve 182a pixel area 182p pixel 183 lens 184 light valve driving unit 401, 80 1 Graph B, B1, B2, Bd, Bi, Bo, G, G1, G2 Brightness Ga1 First gain Ga2 Second gain Gd, Gi, Go, Lg1, Lg2, LgMAX, MAXi, R, R2, Ri Brightness PDg Original image information PDi Input image information PDo Output image information PX Pixel information PX1 First pixel information PX g... original pixel information, PXi... input pixel information, PXo... output pixel information, Po... output image, SC... projection surface, TN1, TN2, TN3, TN4... gradation, Xb, Xg, Xr... coefficient, g1... first gamma characteristic, g2... second gamma characteristic, gc... camera gamma characteristic, gd... display gamma characteristic, ΔLa, ΔLb, ΔLc, ΔLd, ΔLia, ΔLib... difference, γ... coefficient, γ1: first gamma function, γ2: second gamma function, γc: camera gamma function, γd: display gamma function.

Claims (10)

executing a first correction process of multiplying a first lightness, which is the lightness of a first color component having the highest lightness among a plurality of color components included in input pixel information indicating one pixel in an input image composed of a plurality of pixels, by a first gain;
executing a second correction process of multiplying a second lightness of a second color component different from the first color component among the plurality of color components by a second gain smaller than the first gain;
displaying an output image using output pixel information obtained by performing the first correction process and the second correction process on the input pixel information;
Display method. The first correction process includes applying a first gamma correction to the first color component by inputting the first lightness into a first correction function having lightness as a variable;
The second correction process includes applying a second gamma correction to the second color component by inputting the second lightness into a second correction function having lightness as a variable;
When the same brightness is input to the first correction function and the second correction function, the brightness output from the first correction function is higher than the brightness output from the second correction function.
The display method according to claim 1. The first correction process includes outputting the corrected first lightness by inputting the first lightness into the first correction function,
Let γ2B be the lightness output by inputting the second lightness to the second correction function, γ1A be the first lightness after correction, γ2A be the lightness output by inputting the first lightness to the second correction function, and L2 be the second lightness after correction.
L2=γ2B×γ1A/γ2A (1)
The display method according to claim 2. The first correction process includes applying a first gamma correction to the first color component by inputting the first lightness into a first correction function having lightness as a variable;
The second correction process includes applying a second gamma correction to the second color component by inputting the first lightness and the second lightness into a second correction function having lightness as a variable;
The second correction function is
including a value obtained by inputting the first lightness into the first correction function as a coefficient;
The second correction process includes
correcting the second value to a third value when the first lightness is a first value and the second lightness is a second value;
correcting the second value to a fifth value when the first lightness is a fourth value greater than the first value and the second lightness is the second value;
The first correction function corrects the second value to a sixth value when the second lightness is a second value,
the difference between the fifth value and the sixth value is smaller than the difference between the third value and the sixth value;
The display method according to claim 1. wherein the input image is an image obtained by correcting the first image with a third correction function having the lightness of the first image before correction as a variable;
The second gain is between the gain when the second lightness is corrected by the first correction process and the gain when the second lightness is input to the inverse function of the third correction function,
The display method according to any one of claims 1 to 4. the plurality of color components are the first color component, the second color component, and the third color component;
further comprising performing the second correction process on a third lightness of the third color component;
The display method according to any one of claims 1 to 5. The first correction process includes applying a first gamma correction to the first color component by inputting the first lightness into a first correction function having lightness as a variable;
The second correction process includes applying a second gamma correction to the second color component by inputting the first lightness and the second lightness to a second correction function in which a value obtained by inputting the first lightness to the first correction function is included as a coefficient, and the lightness is a variable;
The first correction function is
when the first lightness is the seventh value, correcting the seventh value to the eighth value;
when the first lightness is the ninth value, correcting the ninth value to the tenth value;
The second correction function is
when the second lightness is the eleventh value, correcting the eleventh value to the twelfth value;
correcting the thirteenth value to a fourteenth value when the second lightness is the thirteenth value;
when the difference between the seventh value and the eleventh value is greater than the difference between the ninth value and the thirteenth value, the difference between the eighth value and the twelfth value is greater than the difference between the tenth value and the fourteenth value;
The display method according to claim 1. the plurality of color components are the first color component, the second color component, and the third color component;
the input pixel information includes information indicating the first lightness, information indicating the second lightness, and information indicating the third lightness of the third color component;
wherein the input image is an image obtained by correcting the first image with a third correction function having the lightness of the first image before correction as a variable;
the difference between the hue of the pixel corresponding to the one pixel indicated by the output pixel information and the hue of the pixel corresponding to the one pixel in the first image is smaller than the difference between the hue of the pixel corresponding to the one pixel indicated by the first pixel information and the hue of the pixel corresponding to the one pixel in the first image;
The first pixel information is information obtained when the first gamma correction is applied to the first color component by inputting the first lightness to the first correction function, the first gamma correction is applied to the second color component by inputting the second lightness to the first correction function, and the first gamma correction is applied to the third color component by inputting the third lightness to the first correction function.
The display method according to any one of claims 2 to 4. the plurality of color components are the first color component, the second color component, and the third color component;
the input pixel information includes information indicating the first lightness, information indicating the second lightness, and information indicating the third lightness of the third color component;
wherein the input image is an image obtained by correcting the first image with a third correction function having the lightness of the first image before correction as a variable;
the difference between the saturation of the pixel corresponding to the one pixel indicated by the output pixel information and the saturation of the pixel corresponding to the one pixel in the first image is smaller than the difference between the saturation of the pixel corresponding to the one pixel indicated by the first pixel information and the saturation of the pixel corresponding to the one pixel in the first image;
The first pixel information is information obtained when the first gamma correction is applied to the first color component by inputting the first lightness to the first correction function, the first gamma correction is applied to the second color component by inputting the second lightness to the first correction function, and the first gamma correction is applied to the third color component by inputting the third lightness to the first correction function.
The display method according to any one of claims 2 to 4. an optical device;
a control circuit that controls the optical device;
The control circuit is
executing a first correction process of multiplying a first lightness, which is the lightness of a first color component having the highest lightness among a plurality of color components included in input pixel information indicating one pixel in an input image composed of a plurality of pixels, by a first gain;
executing a second correction process of multiplying a second lightness of a second color component different from the first color component among the plurality of color components by a second gain smaller than the first gain;
causing the optical device to display an output image using output pixel information obtained by performing the first correction process and the second correction process on the input pixel information;
display device.

Images