JP6846307B2 - Luminance adjustment signal generator and its program, and video display device - Google Patents

Description

The present invention provides a luminance adjustment signal generator and its program for generating a signal for adjusting the luminance of a high dynamic range (HDR) video display device, and a luminance adjustment signal generator. Regarding the provided video display device.

HDR is a technology that expands the dynamic range of the brightness of shooting and display compared to the standard dynamic range (SDR), and expresses a wide bright and dark range of a subject richly in gradation and color on a display.
As one of the HDR video systems, the International Telecommunication Union Radiocommunication Sector (ITU-R) Recommendation BT. In 2100, a hybrid log-gamma (HLG: Hybrid Log-Gamma) method is defined (see Non-Patent Document 1).
In addition, Recommendation BT. As the transfer function of the HLG method, the 2100 is an optical transfer function (OETF: Opto-Electronic Transfer Function) and an electric-optical transfer function (EOTF: Electro-Optical Transfer Function) in consideration of compatibility with conventional SDR images. ), The optical transfer function (OOTF: Opto-Optical Transfer Function) is specified.

FIG. 7 shows the relationship between the transfer functions of the HLG method.
OETF of HLG method, as shown in FIG. 7, a transfer function that converts the scene light _{L S} to an electrical signal (video signal HLG type) E 'in 5 (imaging apparatus HDR video system) HDR imaging device.
Specifically, OETF is a linear signal E corresponding to the scene light L _S (normalized value when the [0:12] the level range of subject luminance), the following equation (1), a video signal It is a function that converts to E'.

Further, as shown in FIG. 7, the HLG system EOTF is a transfer function that converts the video signal E'into a signal corresponding to the display light L in the HDR display device (HDR video system video display device) 6. EOTF is composed of an inverse function of OETF (Inverse OETF: OETF ^-1 ) and OOTF.
Specifically, OETF- ¹ sets the video signal E'(normalized value when the level range of the video signal is [0: 1], hereinafter referred to as signal level E'when indicating a level). by the following equation (2) is a function that converts a linear signal E corresponding to the scene light L _S.

However, a, b, and c are the same as those in the above equation (1).
OOTF of HLG scheme is a transfer function representing the characteristic between the display light L and the scene light _{L S.}
Specifically, OOTF the color signal of the linear signal E corresponding to the scene light _{L S {R S, G S} , B S} , and the following equation (3), the display luminance L corresponding to the display light L _D color signal which is a function that converts _{{R D, G D, B} D} on.

Here, α and β are the contrast adjustment value and the brightness adjustment value represented by the following equation (4), respectively.

L _W is the video signal E '= 1 (100% level of the video signal) is the peak intensity of the HDR display device 6 at the time of being input (display _{^{brightness; cd / m 2), L}} B is the video signal E' = 0 ( ^{This is the black level luminance (display luminance; cd / m 2} ) of the HDR display device 6 when a 0% level video signal) is input.
Also, gamma indicates the degree of non-linearity between the display light L and the scene light L _S, is a system gamma that is defined by the following equation (5).

Recommendation BT. In 2100, as a standard viewing conditions, the peak luminance _{L W} is 1000 cd / ^{m 2} or more, the black level luminance _{L B} is defined as 0.005cd / ^{m 2} or less. In particular, the black level luminance L _B is adjusted according to the viewing environment, it is recommended to set.
Currently, for this adjustment, ITU-R Recommendation BT. A black level luminance setting signal (PLUGE [Picture Line Up Generation Equipment] signal) specified in 814 or the Association of Radio Industries and Businesses (ARIB) technical data BTA S-1002 is used (see Non-Patent Documents 2 and 3).

Here, the conventional PLUGE signal will be briefly described with reference to FIG.
FIG. 8A is an image in which the PLUGE signal is displayed on the screen of the image display device (for example, the HDR display device 6 of FIG. 7) to be adjusted for brightness. FIG. 8B is a diagram for explaining each region of the PLUGE signal. FIG. 8B is a diagram showing the arrangement of regions having different brightness of PLUGE signals corresponding to HDTV (High-definition television) of 1080I horizontal 1920 samples and vertical 1080 lines. The sample numbers and line numbers indicate the internal methods of the areas A, B, C (C ₁ , C ₂ ) and D (D ₁ , D _2). In addition, the line number in parentheses of the line number indicates the line number of the second field.

The region A is a region for displaying the _{peak luminance (peak white) L W} corresponding to the video signal E'= 1.
Region B is a region for displaying the black level luminance L _B corresponding to the video signal E '= 0.
The region C (C ₁ , C ₂ ) is a region for displaying the brightness corresponding to the video signal E'= + 0.02. This region C (C ₁ , C ₂ ) is slightly brighter than the black level of region B.
Here, the regions C ₁ and C ₂ having different line widths exist because the patterns in which the luminance can be easily discriminated are different in various displays, and therefore, whichever one is used when adjusting the luminance can be adjusted.
The region D (D ₁ , D ₂ ) is a region for displaying the brightness corresponding to the video signal E'= −0.02. This region D (D ₁ , D ₂ ) is slightly darker than the black level of region B.
Here, the _{reason why the regions D 1} and D ₂ having different line widths exist is the same reason as the regions C ₁ and C _2.

When setting this PLUGE signal black level luminance L _B with adjustment while observing the peak white area A, you can identify the luminance difference between the region B and the region _C (C _1, C ₂₎ , the regions B and _D (D _1, D ₂₎ so that it can not identify the luminance difference, by adjusting the brightness of the display, set the black level luminance L _B.
As a result, when subjectively evaluating the image quality of a video, the subjective evaluation can be performed under unified viewing conditions.

“Image parameter values for high dynamic range television for use in production and international program exchange”, Recommendation ITU-R BT.2100-0, 07/2016 “Specification and alignment procedures for setting of brightness and contrast of displays”, Recommendation ITU-R BT.814-2, 09/2016 "HDTV Standard Viewing Condition Technical Data (BTA S-1002)", Version 1.1, Association of Radio Industries and Businesses, revised on March 19, 2008

The conventional PLUGE signal is basically assumed to be used for setting the black level luminance of the SDR display device.
The peak brightness and black level brightness of the SDR display device are described in the ITU-R Recommendation BT. In 2035, the peak luminance is 100 cd / ^{m 2,} the black level luminance is defined as less than 0.01cd / ^{m 2.}

That is, in the SDR display device, the region A (see FIG. 8) corresponding to the video signal E'= 1 of the conventional PLUGE signal is displayed at ^{100 cd / m 2.}
On the other hand, in the HDR display device, the region A corresponding to the video signal E'= 1 of the conventional PLUG signal is displayed at 1000 cd / m ² or more, and the brightness is 10 times or more higher than that of the SDR display device.

Therefore, when the black level brightness of the HDR display device is adjusted using the conventional PLUGE signal, the black level brightness is set high due to the fact that the area A is displayed with high brightness, and the ITU-R is set to high. Recommendation BT. There is a risk that the appropriate black level brightness (0.005 cd / m ^{2 or less) specified as the standard viewing condition in 2100 may not be satisfied.}
As described above, when the conventional PLUGE signal is used, it is difficult to adjust the appropriate black level brightness with the HDR display device, and it is not possible to perform subjective evaluation of the HDR image under unified viewing conditions. There's a problem.

Therefore, the present invention makes it possible to adjust the brightness of the region having the highest brightness, which is a reference for brightness adjustment, in a video display device that displays an HDR image by the HLG method, and to set the brightness at the black level. An object of the present invention is to provide a luminance adjustment signal generator for generating an adjustment signal (black level luminance setting signal), a program thereof, and a video display apparatus including the luminance adjustment signal generator.

In order to solve the above problems, the luminance adjustment signal generation device according to the present invention generates a luminance adjustment signal for generating a luminance adjustment signal for adjusting the luminance of the image display device that displays an HDR image by the HLG method. The apparatus is configured to include a designated luminance input means, a signal level calculation means, and a signal generation means.

In such a configuration, the luminance adjustment signal generation device inputs the luminance of the region having the highest luminance, which is a reference of the luminance adjustment when the luminance adjustment signal is displayed on the display means, as the designated luminance by the designated luminance input means.
Then, the luminance adjusting signal generator uses the signal level calculation means to generate a video signal corresponding to the specified luminance by the light-optical transfer function (OOTF) and the optical-electrical transfer function (OETF), which are transfer functions of the HLG method. Calculate the signal level of. That is, the signal level calculating means calculates the normalized linear signal corresponding to the designated luminance from the designated luminance by OOTF, and calculates the signal level of the video signal from the linear signal by OETF.

Then, the brightness adjusting signal generation device includes the signal level region calculated by the signal level calculation means and the first black signal level region in the image region of the first black signal level corresponding to the black level brightness of the display means by the signal generation means. A brightness adjustment signal is generated in which each region of the second black signal level and the third black signal level having a predetermined level difference centered on the black signal level is arranged at a predetermined position. That is, in the image region of the first black signal level, only the brightness of the signal level region calculated by the signal level calculating means is variable according to the designated luminance.
As a result, the luminance adjustment signal generator can generate the luminance adjustment signal in which the specified luminance is set in the region having the highest luminance.

Further, in order to solve the above problems, the luminance adjusting signal generation device according to the present invention is configured to include a signal level input means and a signal generation means.

In such a configuration, the luminance adjustment signal generator is a signal of a video signal corresponding to the luminance in the highest luminance region which is a reference for the luminance adjustment when the luminance adjustment signal is displayed on the display means by the signal level input means. Enter the level.

Then, the brightness adjusting signal generation device uses the signal generation means to include the signal level region input by the signal level input means and the first black signal level region in the image region of the first black signal level corresponding to the black level brightness of the display means. A brightness adjustment signal is generated in which each region of the second black signal level and the third black signal level having a predetermined level difference centered on the black signal level is arranged at a predetermined position. That is, in the image region of the first black signal level, only the brightness of the region of the signal level input by the signal level input means is variable according to the signal level.
As a result, the luminance adjustment signal generator can generate the luminance adjustment signal in which the specified luminance is set in the region having the highest luminance.
The brightness adjustment signal generation device can be operated by a brightness adjustment signal generation program for operating the computer as each of the above-mentioned means.

Further, in order to solve the above problems, the image display device according to the present invention is an image display device that displays an HDR image by the HLG method, and is a brightness adjustment signal generation device, an inverse photoelectric conversion means, and a color component. The configuration includes a conversion means, a display means, and an adjustment means.

In such a configuration, the video display device generates a brightness adjustment signal in which the brightness of the region having the highest brightness is set by a designation from the outside by the brightness adjustment signal generation device.
Then, the image display device converts the image signal input from the outside or the luminance adjustment signal generated by the luminance adjustment signal generator by the inverse photoelectric conversion means into the inverse of the HLG optical transfer function (OETF). The function converts it into a linear signal corresponding to the scene light.
Then, the image display device converts the linear signal converted by the inverse photoelectric conversion means by the color component conversion means into an RGB color signal corresponding to the display light by the light-optical transfer function (OOTF) of the HLG method. ..

Then, the video display device displays the RGB color signal converted by the color component conversion means by the display means. As a result, the video signal and the brightness adjustment signal are displayed as the HDR video of the HLG system.
Then, the image display device adjusts the brightness and contrast by changing each value of the brightness adjustment and the contrast adjustment used for the light-optical transfer function (OOTF) in the color component-based conversion means by an external instruction by the adjusting means. To do.
As a result, the video display device can adjust the brightness while displaying the brightness adjustment signal on the display means.

The present invention has the following excellent effects.
According to the present invention, even in an HDR image having a high peak brightness, it is possible to set the brightness of the white area, which is a reference area for brightness adjustment, to be lower than the black level brightness in advance.
As a result, the present invention can prevent the black level brightness from being set high by suppressing the difference in brightness on the screen displaying the brightness adjustment signal, and can unify the viewing conditions for HDR images. Can be subjectively evaluated.

It is a block block diagram which shows the structure of the image display device which concerns on embodiment of this invention. It is a figure for demonstrating the PLUGE signal generated by the image display apparatus which concerns on embodiment of this invention, (a) is a figure for demonstrating each region of a PLUGE signal, (b) is each region of a PLUGE signal. It is a figure which shows the signal level of. It is a flowchart which shows the PLUGE signal generation | display operation of the image display apparatus which concerns on embodiment of this invention. It is a flowchart which shows the brightness adjustment operation of the image display device which concerns on embodiment of this invention. It is a block block diagram which shows the structure which separated the signal generation apparatus for luminance adjustment which concerns on the modification of this invention from an image display apparatus. It is a block block diagram which shows the structure of the signal generator for luminance adjustment which concerns on the modification of this invention. It is explanatory drawing for demonstrating the relationship between an HDR image pickup apparatus of an HLG system and an HDR display apparatus. It is a figure for demonstrating the conventional PLUGE signal, (a) is the figure which shows the image which displayed the PLUGE signal, and (b) is the figure for explaining the arrangement of each region of the PLUGE signal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Video display device configuration]
First, the configuration of the image display device 1 according to the embodiment of the present invention will be described with reference to FIG.

The image display device 1 displays a brightness adjustment signal (black level brightness setting signal; hereinafter referred to as a PLUGE signal), adjusts the brightness (black level brightness), and displays an HDR image by the HLG method. In this PLUGE signal, the luminance of the region (region A in FIG. 8) for displaying the peak luminance (peak white) of the conventional PLUGE signal can be specified so as to correspond to the HDR image.
Here, the image display device 1 includes a storage means 10, a switching means 11, a luminance adjusting signal generating means 12, an inverse photoelectric conversion means 13, a color component converting means 14, a display means 15, and an adjusting means 16. And.

The storage means 10 stores various information used in the video display device 1, and can be configured by a semiconductor memory or the like.
The storage unit 10, the peak luminance L _W, black level luminance L _B, the system gamma gamma, and stores the value β values α and brightness adjustment contrast adjustment predetermined by the initial value, adjusted by the adjusting means 16 If so, the updated value is also stored.

The peak luminance L _W is the luminance of the display (display means 15) when the video signal of the maximum level (E'= 1) in the level range of the video signal is input.
Black level luminance L _B is the brightness of the display (display unit 15) when the video signal of minimum level (E '= 0) in the level range of the video signal is input.
For example, if the display unit 15, the peak luminance ^{_{L W = 1000 (cd / m}} 2), and a display of the black level luminance ^{_{L B = 0 (cd / m}} 2), the storage unit 10 in advance peak luminance _{L W} as 1000 cd / ^{m 2,} setting the 0 cd / ^{m 2} as an initial value as the black level luminance _{L B.}

The system gamma gamma is a gamma value indicating the degree of non-linearity between the scene light and the display light. For example, when the display means 15 is a display having a peak brightness of L _W = 1000 (cd / m ² ), the storage means 10 is set to the value "1.2" obtained by the above equation (5) as an initial value. I will do it.

The contrast adjustment value α is an adjustment value for adjusting the contrast (brightness ratio) of the image displayed by the display means 15.
The brightness adjustment value β is an adjustment value for adjusting the brightness (brightness, brightness) of the image displayed by the display means 15.
The α and beta, the peak luminance _{L W,} black level luminance _{L B,} a value obtained by the equation from the system gamma gamma (4), the peak luminance ^{_{L W = 1000 (cd / m}} 2), the black level luminance ^{_{L B = 0 (cd / m}} 2), if the system gamma γ = 1.2, α = 50.69702849, a beta = 0, is set in advance as an initial value.

The switching means 11 switches either the video signal or the PLUGE signal to the display target. For example, the switching means 11 may display the setting screen via the display means 15 and receive an instruction for switching the video signal or the PLUGE signal, or the switching instruction may be given by an external switch or the like (not shown). It may be accepted.

The switching means 11 basically outputs a video signal input from the outside to the inverse photoelectric conversion means 13, but when the switching instruction is received, the luminance adjusting signal generating means 12 is notified of the PLUGE signal (luminance adjustment). Signal) is instructed to be generated.
The switching means 11 outputs the video signal or the PLUGE signal to be displayed to the inverse photoelectric conversion means 13. Here, the signal (video signal or PLUGE signal) output from the switching means 11 is indicated by E'.

The brightness adjustment signal generation means (brightness adjustment signal generation device) 12 generates a PLUGE signal corresponding to the HLG method. Here, the luminance adjusting signal generating means 12 includes a designated luminance input means 12a, a signal level calculating means 12b, and a signal generating means 12c.

The designated luminance input means 12a inputs the highest luminance (display luminance) as a reference for the luminance adjustment when the PLUGE signal is displayed on the display means 15 as the designated luminance L _REF .
For example, the designated luminance input means 12a may display the setting screen via the display means 15 and input the designated luminance, or may use means for changing the luminance level such as a slider (not shown). The specified brightness may be input.

^{When, for example, 100 cd / m 2,} which is the peak brightness of the SDR display device, is input as the specified brightness L _REF , the image display device 1 sets the black level brightness in a viewing environment substantially equivalent to that of the SDR display device. can do.
The designated luminance input means 12a outputs the designated luminance L _REF to the signal level calculating means 12b.

The signal level calculating means 12b calculates the signal level (video signal level) of the video signal for displaying the designated luminance input from the designated luminance input means 12a.
The signal level calculating means 12b calculates the signal level corresponding to the _{designated luminance L REF} by the transfer functions OOTF and OETF of the HLG method.
Specifically, the signal level calculating means 12b calculates the signal level E'corresponding to the designated luminance L _REF by the following equations (6) and (7).

However, α, β, γ, a, b, and c are the same as those in the above equations (1), (4), and (5).
Formula (6), in the transfer function OOTF (Formula (3)) and a gray color of a color to be black and white, the color signal of the formula _{(3) {R S, G} S, B S} Is an equation obtained from the fact that each is the same.

For example, when the signal level calculation means 12b ^{inputs 100 cd / m 2,} which is the peak brightness of the SDR display device, as _{the designated brightness L REF} , the contrast adjustment is stored in the storage means 10 according to the above equation (6). the value α (= 50.69702849), the value β (= 0) of brightness adjustment using a system gamma gamma (= 1.2), calculates a linear signal _E S = 1.761359121.
Then, the signal level calculation means 12b calculates the signal level E'= 0.629620322≈0.63 by the above equation (7).

As a result, the signal level calculating means 12b can calculate the signal level of the designated luminance when the signal level E'= 1 of the peak luminance and the signal level E'= 0 of the black level luminance are set. When α, β, etc. are updated by the adjusting means 16, the signal level calculating means 12b calculates E'using the updated values.
The signal level calculating means 12b outputs the calculated signal level of the designated luminance to the signal generating means 12c.

The signal generation means 12c generates a PLUGE signal in which the signal level in the white region having the highest brightness is set to the signal level of the designated brightness calculated by the signal level calculation means 12b.
Here, with reference to FIG. 2, the pattern of the PLUGE signal generated by the signal generation means 12c will be described. FIG. 2A is an image in which the PLUGE signal is displayed on the screen of the display means 15, and the positions of the regions having different brightness are the same as those in FIG. FIG. 2B shows the signal levels of the PLUGE signals shown in FIG. 2A in which the brightness of each region is different.

As shown in FIG. 2, the signal generation means 12c generates _{a PLUGE signal having regions A, B, C (C 1} , C ₂ ) and D (D ₁ , D ₂ ) having different signal levels.
The area A is an area for displaying the brightness corresponding to the signal level E'(for example, 0.63) calculated by the signal level calculating means 12b. Here, the peak white level of the signal level E'= 1 corresponds to the pixel value "235" in the 8-bit system, and the black level luminance of the signal level E'= 0 becomes the pixel value "16" in the 8-bit system. Equivalent to. That is, in the case of an 8-bit system, the area A corresponds to the pixel value "154".

Regions B, C (C ₁ , C ₂ ) and D (D ₁ , D ₂ ) are the same as the conventional PLUGE signal described with reference to FIG.
In other words, the region B is a region for displaying the black level luminance L _B corresponding to the signal level E '= 0 (the first black signal level). For example, in the case of an 8-bit system, it corresponds to the pixel value "16".

Regions C (C ₁ , C ₂ ) and D (D ₁ , D ₂ ) have a predetermined level difference (± 0.02) centered on the signal level E'= 0 (first black signal level). ..
The region C (C ₁ , C ₂ ) is a region for displaying the luminance corresponding to the signal level E'= + 0.02 (second black signal level). For example, in the case of an 8-bit system, it corresponds to the pixel value "20". This region C (C ₁ , C ₂ ) is slightly brighter than the black level luminance of region B.

The area D (D ₁ , D ₂ ) is an area for displaying the luminance corresponding to the signal level E'= −0.02 (third black signal level). For example, in the case of an 8-bit system, it corresponds to the pixel value "12". This region D (D ₁ , D ₂ ) is slightly darker than the black level luminance of region B.
The arrangement of the regions shown in FIG. 2 is an example, and the size and position of each region are not limited to this.
As described above, the brightness adjusting signal generation means 12 can set the signal level (video signal level) of the video signal in the white region having the highest brightness in the PLUGE signal by an instruction from the outside.

Returning to FIG. 1, the configuration of the video display device 1 will be described.
The signal generation means 12c outputs the generated PLUGE signal to the switching means 11. That is, the PLUGE signal is output to the inverse photoelectric conversion means 13 via the switching means 11.

The inverse photoelectric conversion means 13 converts the HLG system HDR video signal (or PLUGE signal) E'(hereinafter, simply referred to as signal E') input via the switching means 11 into a linear signal E corresponding to the scene light. It is to convert to. The processing of the inverse photoelectric conversion means 13 ^{corresponds to the inverse function (OETF -1} ) processing of the transfer function OETF.

Specifically, the inverse photoelectric conversion means 13 converts the signal E'into a linear signal E corresponding to the scene light by the above equation (2).
The signal E 'is RGB color signals for each pixel _{{R S', G S '} , B S'} is composed of _{(E '= {R S'} , G S ', B S'}), the inverse photoelectric converting means 13, the formula (2) is calculated for each color signal, a color signal corresponding to the scene light to produce a _{{R S, G S, B} S} linear signal E consists of.
Inverse photoelectric conversion unit 13 outputs a linear signal _E converted _{{R S, G S, B} S} and the color component conversion unit 14.

The color component conversion means 14 applies a system gamma for each color component to the linear signal corresponding to the scene light converted by the inverse photoelectric conversion means 13, so that the linear signal is proportional to the intensity of the display light. It is to convert to. The processing of the color component converting means 14 corresponds to the processing of the transfer function OOTF.

Specifically, the color component conversion unit 14, by the equation (3), the linear signal _{E {R S, G S,} B S} color signals _{R D of the display brightness _{L D} corresponding to the display light, G Convert to _D , _BD}.
The color component converting means 14 generates a _{color signal {RD} , G _D , _BD } by using the contrast adjustment value α, the brightness adjustment value β, and the system gamma γ stored in the storage means 10. .. At this time, the color component converting means 14 uses the initial value when only the initial value is stored in the storage means 10, and uses the updated value when the updated value is stored, and uses the color signal {R. _D , G _D , _BD } is generated.

The color component converting means 14 basically reads α, β, and γ from the storage means 10 once, and then holds the values to generate a color signal. However, when the color component converting means 14 receives a notification from the adjusting means 16 that the contrast or the like has been adjusted, the color component converting means 14 reads α, β, and γ from the storage means 10 again.
As a result, the color component converting means 14 can generate a color signal that reflects the adjusted brightness and contrast.
The color component conversion means 14 outputs the generated color signals { _RD , G _D , _BD } to the display means 15.

The display means (display) 15 is a general display that displays a signal (color signal) proportional to the intensity of the display light generated by the color component conversion means 14, and is, for example, a liquid crystal display or the like. By the display means 15, the image display device 1 allows the observer to visually recognize the image signal (or PLUGE signal) as an image.

The adjusting means 16 changes the brightness and contrast of the image displayed by the display means 15 by an instruction from the outside. Here, the adjusting means 16 includes a brightness adjusting means 16a and a contrast adjusting means 16b.

The brightness adjusting means 16a adjusts the brightness of the image displayed by the display means 15.
Specifically, the brightness adjustment means 16a inputs an adjustment value (brightness adjustment value β) changed by the adjuster via a level changing means such as a rotary encoder or a slider (not shown). The brightness adjustment unit 16a is written and stored in the storage unit 10 and the value β of brightness adjustment which is adjusted and the black level luminance L _B as an update value. Note that, as shown in the equation (4), and the value β of the brightness adjustment, the black level luminance L _B of the same value.

At this time, brightness adjustment unit 16a is, with the update of the black level luminance L _B, so as not to change the value α of the contrast adjustment, according to the equation (4) and (5), the peak luminance L _W and the system gamma γ Is calculated, and is written and stored in the storage means 10 as an update value.

Thus, brightness adjustment unit 16a writes the peak luminance L _W is changed by the brightness _adjustment, black level luminance L _B, the value β of the system gamma γ and brightness adjustment, the storage unit 10 as a respective update value, adjustment Notifies the color component conversion means 14 that the above has been performed.

The contrast adjusting means 16b adjusts the contrast of the image displayed by the display means 15.
Specifically, the contrast adjusting means 16b inputs an adjusting value (contrast adjusting value α) changed by the adjuster via a level changing means such as a rotary encoder or a slider (not shown). Then, the contrast adjusting means 16b writes and stores the adjusted contrast adjustment value α as an update value in the storage means 10.

_{At this time, the contrast adjusting means 16b calculates the peak luminance L W} and the system gamma γ by the above equations (4) and (5) as the contrast adjusting value α is updated, and the storage means 10 is used as the updated value. Write and memorize in.

In this way, the contrast adjusting means 16b _{writes the peak luminance L W} , the system gamma γ, and the contrast adjusting value α changed by the contrast adjustment to the storage means 10 as the respective update values, and indicates that the adjustment has been performed. Notify the color component conversion means 14.

By configuring the video display device 1 as described above, the video display device 1 can display the white region having the highest brightness of the PLUGE signal with the brightness set from the outside. As a result, if the brightness of the white region is set to, for example, 100 cd / m ² which is the same as that of the SDR display device, the image display device 1 adjusts the brightness with a brightness difference between white and black which is almost the same as that of the SDR display device. This makes it possible to prevent the black level brightness from being adjusted unnecessarily high.
The video display device 1 can be operated by a program (video display program) for operating the computer as each of the above-mentioned means.

[Operation of video display device]
Next, the operation of the image display device 1 according to the embodiment of the present invention will be described. Here, as the operation of the video display device 1, the operation of generating and displaying the PLUGE signal and the operation of adjusting the brightness will be described separately.

(PLUGE signal generation / display operation)
First, an operation of generating and displaying a PLUGE signal of the video display device 1 will be described with reference to FIG. 3 (see FIG. 1 for the configuration as appropriate). Incidentally, the storage means 10 is intended to advance the peak luminance L _W, black level luminance L _B, the system gamma gamma, the value β values α and brightness adjustment of the contrast adjustment is stored.
Further, it is assumed that the switching means 11 is switched so as to output the PLUGE signal to the inverse photoelectric conversion means 13.

_{The image display device 1 inputs the designated luminance L REF,} which is the luminance of the white region having the highest luminance in the PLUGE signal, by the designated luminance input means 12a of the luminance adjusting signal generating means 12 (step S1).

Then, the video display device 1 calculates the signal level of the video signal corresponding to the _{designated luminance L REF} by the signal level calculating means 12b of the luminance adjusting signal generating means 12 (step S2).
That is, the signal level calculation means 12b uses the system gamma γ, the contrast adjustment value α, and the brightness adjustment value β stored in the storage means 10 to perform simultaneous equations of the above equations (6) and (7). By solving, the signal level _{E'corresponding} to the specified luminance L REF is obtained.

Then, the video display device 1 generates a PLUGE signal by the signal generation means 12c of the brightness adjustment signal generation means 12 (step S3).
At this time, as shown in FIG. 2, the signal generation means 12c determines the black level luminance when the signal level of the black level luminance of the video signal is “0” and the signal level of the peak white luminance is “1”. images on (region B), the region of the signal level slightly bright "+0.02" than the black level luminance (regions _C 1, _{C 2),} the signal level of a darker "-0.02" than the black level luminance A PLUGE signal is generated by arranging the regions (areas D ₁ and D ₂ ) and further arranging the white region (region A) of the signal level calculated in step S2 in the center of the screen.

Then, the image display device 1 performs inverse photoelectric conversion, that is, calculation of the inverse function (OETF ^-1 ) of the transfer function OETF, on the PLUGE signal generated in step S3 by the inverse photoelectric conversion means 13. It is converted into a linear signal corresponding to light (step S4).

Then, the image display device 1 applies the system gamma for each color component to the linear signal E generated in step S4 by the color component conversion means 14 according to the above equation (3), and the intensity of the display light is increased. A color signal { _RD , G _D , _BD } proportional to is generated (step S5).

Then, the image display device 1 displays the color signals { _RD , G _D , _BD } generated in step S5 as an image by the display means 15 (step S6).
By the above operation, the video display device 1 can display the white region having the highest brightness of the PLUGE signal with the brightness specified from the outside.

(Brightness adjustment operation)
Next, the brightness adjusting operation of the video display device 1 will be described with reference to FIG. 4 (see FIG. 1 for the configuration as appropriate). Here, the operation of setting the black level luminance in the state where the PLUGE signal is displayed as an image will be described.

The image display device 1 adjusts the brightness (luminance) of the image of the PLUGE signal displayed by the display means 15 by the brightness adjustment means 16a of the adjustment means 16 according to the brightness adjustment value β set by the adjuster (step S10). ..
_{That is, the adjuster can discriminate the brightness difference between the area B and the area C (C 1} , C ₂ ) while observing the white area having the highest brightness in the area A shown in FIG. 2, but the area B and the area D The brightness is adjusted so that the difference in brightness cannot be distinguished from (D ₁ , D _2).

_{At this time, the brightness adjusting means 16a calculates the peak luminance L W} and the system gamma γ by the above equations (4) and (5) so as not to change the contrast adjustment value α, and stores the system gamma γ as updated values. Write and memorize in 10. Then, the brightness of the image of the PLUGE signal is adjusted by applying the new α, β, and γ to the color component converting means 14.

Then, the image display device 1 adjusts the contrast (brightness ratio) of the image of the PLUGE signal displayed by the display means 15 according to the contrast adjustment value α set by the adjuster by the contrast adjusting means 16b of the adjusting means 16 ( Step S11).
_{Since the peak luminance L W} changes depending on the operation of step S10, the highest luminance of the PLUGE signal also changes. Therefore, in step S11, the adjuster adjusts the contrast so that the brightness of the white area in the center of the screen is substantially the same as the set brightness (brightness before brightness adjustment).

The brightness adjustment operation of the video display device 1 does not necessarily end with one operation of steps S10 and S11. In the image of the PLUGE signal shown in FIG. 2, the adjuster can distinguish the brightness difference between _{the area B and the area C (C 1} , C _{2) because the brightness of the central area A becomes the desired brightness.} Adjustment is performed by repeating the operations of steps S10 and S11 as appropriate so that the luminance difference cannot be distinguished from the region D (D ₁ , D _2).

By the above operation, the video display device 1 can present an image of the PLUGE signal in which the white region having the highest brightness is displayed with the brightness specified from the outside, and the adjuster can adjust the brightness appropriately.
Although the configuration and operation of the video display device 1 according to the embodiment of the present invention have been described above, the present invention is not limited to this embodiment.

[Modification example]
(Modification example 1)
Here, the luminance adjusting signal generating means (luminance adjusting signal generating device) 12 is provided inside the image display device 1. However, the luminance adjusting signal generating means 12 may be configured separately from the video display device 1.
For example, as shown in FIG. 5, the luminance adjusting signal generating means 12 separated from the image display device 1 may be configured as the luminance adjusting signal generating device 12B.

The luminance adjustment signal generation device 12B generates a PLUGE signal corresponding to the HLG method, and includes a designated luminance input means 12Ba, a signal level calculation means 12Bb, and a signal generation means 12c. Since the signal generating means 12c is the same as that described with reference to FIG. 1, the description thereof will be omitted.

The designated luminance input means 12Ba inputs the luminance of the white region having the highest luminance, which is a reference for the luminance adjustment when the PLUGE signal is displayed on the display means 15, as the designated luminance L _REF . This function is the same as the designated luminance input means 12a described with reference to FIG.
However, specifying the brightness input means 12Ba is due to that it has an independent device luminance adjustment signal generator 12B, in addition to the specified luminance L _REF, and inputs the peak luminance L _W, black level luminance L _B, the system gamma γ Or, it will be memorized in advance.

The signal level calculating means 12Bb calculates the signal level (video signal level) of the video signal for displaying the designated luminance input from the designated luminance input means 12Ba. This function is the same as the signal level calculating means 12b described with reference to FIG.
However, the signal level calculating unit 12Bb, the peak luminance L _W required for calculating the signal _level, the black level luminance L _B, the system gamma gamma, to get through the specified luminance input means 12Ba. Then, the signal level calculating unit 12Bb, the peak luminance L _W, black level luminance L _B, the system gamma gamma, according to the equation (4) to calculate the value β values α and brightness adjustment of contrast adjustment.

Since the process of calculating the signal level after obtaining the contrast adjustment value α and the brightness adjustment value β of the signal level calculation means 12Bb is the same as that of the signal level calculation means 12b described with reference to FIG. 1, the description thereof will be omitted. ..
The signal level calculating unit 12Bb, in cooperation with the image display device 1B, the peak luminance L _W, black level luminance L _B, the system gamma gamma, the value β values α and brightness adjustment of the contrast adjustment, the image display device 1B It may be obtained from.

Further, as an image display device in which the brightness adjusting signal generation means 12 of FIG. 1 is separated, the image display device 1B is configured by omitting the switching means 11 in FIG.
In this case, the image display device 1B may be connected to the brightness adjustment signal generation device 12B by a signal line at the time of brightness adjustment, and may be connected to a device for transmitting a video signal (not shown) by a signal line at the time of image display. Of course, the video signal or the PLUGE signal may be switched by providing the switching means 11 inside or outside the video display device 1B.

(Modification 2)
Further, here, the luminance adjusting signal generating means 12 (see FIG. 1) and the luminance adjusting signal generating device 12B (see FIG. 5) are provided with the signal level calculating means 12b and 12Bb.
However, the calculation of the signal level of the designated luminance performed by the signal level calculation means 12b and 12Bb can be calculated externally in advance.

In that case, as shown in FIG. 6, the brightness adjustment signal generation device (luminance adjustment signal generation means) 12C may be configured.
That is, the luminance adjusting signal generating device (luminance adjusting signal generating means) 12C may be configured to include the signal level input means 12d and the signal generating means 12c. Since the signal generating means 12c is the same as the signal generating means 12c described with reference to FIG. 1, the description thereof will be omitted.

The signal level input means 12d inputs the signal level of the video signal corresponding to the brightness of the region having the highest brightness, which is a reference for the brightness adjustment when the PLUGE signal is displayed on the display means 15. For example, when the brightness of the region A (see FIG. 2) having the highest brightness of the PLUGE signal is 100 cd / m ² , which is the peak brightness of the SDR display device, the signal level E described in the signal level calculation means 12b of FIG. ′ = 0.63 may be used.

The brightness adjustment signal generation devices 12B and 12C described in the first and second modifications can be operated by a program (brightness adjustment signal generation) for operating the computer as each of the above-mentioned means.

(Modification example 3)
Further, here, an example has been described in which _{the designated luminance L REF} ^{is set to 100 cd / m 2} , which is the peak white (= peak luminance) of the SDR display device.
However, this is to prevent the black level brightness from being set high due to the high brightness in the area A (see FIG. 2) of the PLUGE signal, and is necessarily 100 cd, which is the same as the peak white of the SDR display device. It does not have to be / m ^2. For example, even if it is about 200 cd / m ² , the purpose can be sufficiently achieved.

1,1B video display device 10 Storage means 11 Switching means 12, 12B, 12C Luminance adjustment signal generation means (luminance adjustment signal generation device)
12a, 12Ba Designated luminance input means 12b, 12Bb Signal level calculation means 12c Signal generation means 12d Signal level input means 13 Inverse photoelectric conversion means 14 Color component conversion means 15 Display means (display)
16 Adjusting means 16a Brightness adjusting means 16b Contrast adjusting means

Claims (4)

A brightness adjustment signal generator that generates a brightness adjustment signal for adjusting the brightness of an image display device that displays HDR images in the HLG system.
A designated luminance input means for inputting the luminance of the region having the highest luminance as a reference for the luminance adjustment when the luminance adjusting signal is displayed on the display means as the designated luminance, and a designated luminance input means.
A signal level calculating means for calculating the signal level of the video signal corresponding to the specified luminance by the light-optical transfer function and the optical-electric transfer function which are the transfer functions of the HLG method.
Within the image region of the first black signal level corresponding to the black level brightness of the display means, a predetermined level difference between the region of the signal level calculated by the signal level calculation means and the first black signal level is set. A signal generation means for generating the luminance adjusting signal in which the regions of the second black signal level and the third black signal level are arranged at predetermined positions, and
A signal generation device for luminance adjustment, which comprises. A brightness adjustment signal generator that generates a brightness adjustment signal for adjusting the brightness of an image display device that displays HDR images in the HLG system.
A signal level input means for inputting a signal level of a video signal corresponding to the brightness of the region having the highest brightness, which is a reference for brightness adjustment when the brightness adjustment signal is displayed on the display means, and a signal level input means.
Within the image region of the first black signal level corresponding to the black level brightness of the display means, a predetermined level difference between the region of the signal level input by the signal level input means and the first black signal level is set. A signal generation means for generating the brightness adjustment signal in which the regions of the second black signal level and the third black signal level are arranged at predetermined positions, and
A signal generation device for luminance adjustment, which comprises. A luminance adjustment signal generation program for causing a computer to function as the luminance adjustment signal generator according to claim 1 or 2. It is a video display device that displays HDR video in the HLG system.
The luminance adjusting signal generator according to claim 1 or 2.
The inverse function of converting the video signal input from the outside or the brightness adjustment signal generated by the brightness adjustment signal generator into a linear signal corresponding to the scene light by the inverse function of the light-electric transmission function of the HLG method. Photoelectric conversion means and
A color component converting means for converting a linear signal converted by the inverse photoelectric conversion means into a color signal corresponding to display light by the light-optical transfer function of the HLG method.
A display means for displaying the color signal converted by the color component conversion means, and
An adjustment means for changing each value of brightness adjustment and contrast adjustment used for the light-light transfer function in the color component conversion means, and an adjustment means.
An image display device characterized by being provided with.

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