JP4832900B2 - Image output apparatus, image output method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image output apparatus and an image output method capable of displaying a display image easily viewed by a viewer by preventing deterioration in the visibility of the display image caused by external light. <P>SOLUTION: A luminance distribution detection circuit 301 in a luminance correction section 103 of a projector discriminates to which consecutive small intervals with the same widths a luminance value of each of pixels by one image is included within a maximum interval and a minimum interval which the luminance value can take and counts the number of pixels whose luminance values are included in each small interval, a coefficient calculation circuit 302 calculates a conversion coefficient proportional to the number of the pixels included in each small interval, and a luminance level adjustment circuit 303 uses the conversion coefficient and an offset generated by a correction value determining circuit 305 in response to the illuminance of the external light to correct the luminance value of each pixel. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an image output apparatus that outputs an image, and more particularly, to a technique for improving a reduction in visibility of the image due to external light.

When the illuminance of external light increases while an image output device such as a projector device is outputting an image, the contrast of the displayed image deteriorates and the image becomes difficult to see. One of the techniques for improving such an adverse effect on contrast caused by external light is an image processing apparatus disclosed in Patent Document 1.
When the image processing apparatus disclosed in Patent Document 1 receives an input video luminance signal, the image processing apparatus detects external light illuminance around the CRT, and a plurality of gradation corrections stored in the storage unit based on the detected external light illuminance A desired table is selected from the tables, and the visibility of the image is improved by correcting the input video luminance signal using the selected gradation correction table.
JP-A-9-190170

However, there are various kinds of images such as a bright image and a dark image as a whole, and it is not possible to simply perform tone correction using a tone correction table according to the external light level as in Patent Document 1. The visibility of the displayed image is not always improved.
For example, if a gradation correction table is prepared to correct a low-luminance part to a high luminance for a certain illuminance of external light, using the gradation correction table to correct an image that is originally mostly dark However, when correcting mostly bright images, the remaining dark areas are corrected brightly, and there is no contrast difference between the originally bright areas and the brightly corrected areas. It is also conceivable that the visibility of the image decreases.

In addition, if the gradation correction table is simply changed according to the photometric value of the ambient light illuminance, the luminance after the correction varies due to the fluctuation of the photometric value, and a flicker phenomenon may occur on the screen.
In view of the above problems, an object of the present invention is to provide an image output apparatus and an image output method capable of improving visibility reduction due to external light of a display image and displaying an image easy for a viewer to view.

  In order to solve the above-described problems, the present invention provides an image output apparatus that corrects and outputs the luminance of an original image according to the intensity of external light, and outputs an original image in which each pixel is expressed with luminance according to a predetermined specification. Storage means for storing, counting means for counting the number of pixels including the luminance value of each pixel of the original image for each of the luminance sections obtained by equally dividing the entire luminance area based on the specification, and each luminance section Calculating means for calculating an addition value proportional to the number of pixels counted with respect to the luminance value of each pixel, and for the luminance value of each pixel, the addition value counted for a luminance interval including the luminance value is used as the position of the luminance value in the luminance interval. The corrected brightness value obtained by adding the adjustment value adjusted based on the brightness value and the added value counted for each brightness section in which the upper limit value of the brightness section is smaller than the lower limit value of the brightness section in which the brightness value is included. Replace value And a conversion unit that.

  The image output apparatus according to the present invention has the above-described configuration, so that the larger the number of luminance values included in an image to be displayed, the higher the luminance contrast in the luminance section, and the smaller the number of luminance values included, the luminance. Since the brightness contrast in the section is lowered, the contrast in the brightness range most widely distributed in the image is improved, and an image with improved visibility for the viewer can be output. In addition, as in the case of correcting the luminance value using a fixed correction table without using the luminance distribution of the image, the dark portion that is the remaining small portion is corrected brightly with a focus on the video that is mostly bright. However, the overall visibility of the image can be improved without improving the visibility of the image, and the contrast of most of the bright areas can be improved, and an image with improved visibility for the viewer can be output.

  In addition, the calculation means includes a section pixel number calculation unit that calculates the number of section pixels by dividing the total number of pixels in the original image by the number of brightness sections, and the number of pixels including a brightness value for each brightness section. A conversion coefficient calculation unit for calculating a conversion coefficient by dividing the pixel value by the number of pixels in the section, and a difference value between the upper limit value and the lower limit value of the brightness section is multiplied by the conversion coefficient related to the brightness section to obtain an addition value. It is good also as including the area addition value calculation part to calculate.

Further, the conversion means is proportional to the difference between the lower limit value of the luminance section including the luminance value and the luminance value, with respect to the addition value counted for the luminance section including the luminance value. It may be calculated by multiplying by an adjustment coefficient.
According to this configuration, for the image to be displayed, the greater the number of luminance values included, the higher the luminance contrast in the luminance interval, and the smaller the number of luminance values included, the lower the luminance contrast in the luminance interval. The contrast of the most widely distributed luminance range in the image is improved, and an image with improved visibility for the viewer can be output.

  The image output device further includes photometric means for measuring external light intensity, and external light converting means for converting the external light intensity into an offset value related to luminance, and the conversion coefficient calculation unit includes the conversion coefficient. As a result, the division result is multiplied by ((the upper limit value of the entire luminance region−the offset value) / the upper limit value of the entire luminance region), and the conversion unit corrects the corrected luminance value obtained by adding the offset value. Thus, the luminance value may be replaced.

  The photometric means measures the external light intensity a plurality of times, and the external light conversion means calculates a change amount of the external light intensity, and corrects the recently measured external light intensity based on the change amount. An external light intensity correction unit, and an external light conversion unit that converts the corrected external light intensity into the offset value according to proportional conversion that proportionally distributes the range from the lower limit value to the upper limit value of the external light intensity to the entire luminance range And may be included.

According to this configuration, the luminance value of each pixel is corrected to a luminance value obtained by adding an offset value according to the external light intensity, so that the contrast of the displayed image is relatively lowered due to the influence of external light. Therefore, it is possible to output an image with improved visibility for the viewer.
Further, the external light intensity correction unit is configured to calculate a difference between the external light intensity measured last time and the external light intensity measured most recently, and when the difference is less than a predetermined lower limit, When the measured external light intensity is output and the difference is greater than a predetermined upper limit value, the most recently measured external light intensity is output, and the difference is greater than or equal to a predetermined lower limit value and less than or equal to a predetermined upper limit value And an adjustment unit that multiplies the external light intensity measured last time by a predetermined coefficient and outputs the result.

  According to this configuration, when the difference in external light intensity is between the predetermined lower limit value and the predetermined upper limit value, the external light intensity is multiplied by the predetermined coefficient, so that the change in the luminance value is moderated. be able to. In particular, when the measured value of the external light intensity fluctuates by about several percent, the correction value of the brightness value is reduced. Can be prevented.

  Further, the image output device further includes a minimum luminance that is a luminance section including a lower limit value of the entire luminance region when a minimum corrected luminance value that is the minimum among the corrected luminance values of the original image is larger than a predetermined threshold value. The range from the corrected brightness value related to the lower limit value of the minimum brightness section to the corrected brightness value related to the upper limit value of the minimum brightness section in the section, from the lower limit value of the minimum brightness section to the corrected brightness value related to the upper limit value of the minimum brightness section It is good also as providing the black correction | amendment means which correct | amends proportionally distributed to the range of.

According to this configuration, since the luminance value of the low luminance portion is further lowered, the blackness in the displayed image can be made clear and the image can be tightened.
The image output device further includes a skin color determination unit that determines whether or not the hue of each pixel is a skin color, and the calculation unit calculates an addition value related to each luminance section for the pixel determined to be a skin color. It may be multiplied by a predetermined number.

According to this configuration, it is possible to prevent the tone of the skin color portion from being suddenly corrected, and to output an image that does not impair the color tone of the skin color portion by the correction.
The image output apparatus further includes an average luminance calculating unit that calculates an average luminance value of the original image, and the calculating unit relates to each luminance section when the average luminance value is equal to or less than a predetermined value. The addition value may be multiplied by a predetermined number.

According to this configuration, overcorrection can be prevented. Therefore, for example, an image with many dark luminance components, such as an image showing the night sky, is not excessively overcorrected to prevent the night sky from appearing as a bright image. For an image having many bright luminance components, it is possible to prevent the scenery from becoming dark without over-correcting.
Further, the image output device further includes a maximum / minimum value detection unit that detects a maximum value and a minimum value of luminance values of pixels included in the original image, and the calculation unit calculates an addition value in each luminance interval, ((The upper limit value of the entire luminance region−the lower limit value of the entire luminance region) / (the maximum value of the luminance value of the pixel included in the original image−the minimum value of the luminance value of the pixel included in the original image)). It is good.

According to this configuration, since the luminance value of each pixel is expressed using the entire range from the minimum value to the maximum value that can be taken by the luminance value, it is possible to further enhance the contrast of the image and improve the visibility.
Further, the image output device further performs color adjustment for correcting the color difference value by multiplying the color difference value of each pixel by (the luminance value after correction by the conversion unit / the luminance value before correction by the conversion unit). Means may be provided.

According to this configuration, the luminance value of the pixel is corrected, and the color difference value of the pixel is also corrected by multiplying (the luminance value after correction / the luminance value before correction), so that only the luminance value is corrected. It is possible to prevent the pixel color caused by the increase from being thinned, and to output an image with excellent contrast and coloring and excellent visibility.
The image output method of the present invention stores an original image in which each pixel is expressed in luminance according to a predetermined specification, and corrects the luminance of the original image according to the intensity of external light and outputs the image. In the output method, a counting step of counting the number of pixels including the brightness value of each pixel of the original image for each of the brightness sections obtained by equally dividing the entire brightness area based on the specification, and counting for each brightness section A calculation step of calculating an addition value proportional to the number of pixels obtained, and, for the luminance value of each pixel, the addition value counted for the luminance interval including the luminance value is based on the position of the luminance value in the luminance interval. A corrected brightness value obtained by adding the adjusted adjustment value and the added value counted for each brightness section in which the upper limit value of the brightness section is smaller than the lower limit value of the brightness section including the brightness value. And a conversion step of replacing.

  The computer program of the present invention stores an original image in which each pixel is expressed in luminance with a predetermined specification, and corrects the luminance of the original image according to the intensity of external light and outputs the computer image. A counting step for counting the number of pixels in which the luminance value of each pixel of the original image is included for each of the luminance intervals obtained by equally dividing the entire luminance range based on the specification; A calculation step for calculating an addition value proportional to the number of pixels, and for the luminance value of each pixel, the addition value counted for the luminance section including the luminance value is adjusted based on the position of the luminance value in the luminance section. Correction obtained by adding the adjustment value and the added value counted for each luminance section in which the upper limit value of the luminance section is smaller than the lower limit value of the luminance section including the luminance value In degrees values, and a conversion step of replacing the luminance value.

  According to this configuration, for the image to be displayed, the greater the number of luminance values included, the higher the luminance contrast in the luminance interval, and the smaller the number of luminance values included, the lower the luminance contrast in the luminance interval. The contrast of the most widely distributed luminance range in the image is improved, and an image with improved visibility for the viewer can be output. In addition, as in the case of correcting the luminance value using a fixed correction table without using the luminance distribution of the image, the dark portion that is the remaining small portion is corrected brightly with a focus on the video that is mostly bright. However, the overall visibility of the image can be improved without improving the visibility of the image, and the contrast of most of the bright areas can be improved, and an image with improved visibility for the viewer can be output.

  An image output apparatus according to the present invention is an image output apparatus that outputs a corrected image by correcting the luminance of an original image in accordance with the intensity of external light, and stores an original image composed of a plurality of pixels. Means for counting, for the pixels included in the original image, counting means for counting the number of section pixels indicating the number of pixels having a luminance value included in the predetermined brightness section; and the section image for the total number of pixels constituting the original image. Calculating means for calculating a conversion coefficient for a pixel having a luminance value included in the luminance interval based on a ratio of the number, and for each pixel having a luminance value included in the luminance interval, based on the conversion coefficient, A conversion unit that converts a luminance value of a pixel and calculates a converted luminance value; an external light correction unit that corrects the calculated converted luminance value according to the intensity of external light and generates a corrected luminance value; Correction with corrected brightness value And an outputting means for outputting the corrected image composed of elements.

Hereinafter, embodiments of an image output apparatus and an image output method according to the present invention will be described with reference to the drawings, taking a projector apparatus as an example.
<1. First Embodiment>
<Overview>
The projector apparatus 1 according to an embodiment of the present invention relates to an image projected on a screen, prevents a decrease in contrast and gradation collapse due to the influence of external light around the projector apparatus 1, and is based on fluctuations in measured values of external light illuminance. This prevents the occurrence of the flicker phenomenon.

As shown in FIG. 1 as an example, the projector apparatus 1 is connected to a personal computer 10 using a video cable, receives a video signal output from the personal computer 10 via the video cable, and receives the received video signal. The signal is processed, developed on a built-in liquid crystal panel, and projected onto the screen 20.
As shown in FIG. 2 as an example, the projector apparatus 1 includes a video input terminal 21, an S video input terminal 22, an RGB / YPbPr input terminal 23, a remote control light receiving unit 24, a lens 25, a direction key 26, and a determination button. 27 and the external light sensor 28 are provided, the RGB / YPbPr input terminal 23 receives the luminance signal Y, the color difference signal Pb, and the color difference signal Pr output from the personal computer 10, and the external light sensor 28 is connected to the projector device 1. Detect ambient illuminance.

As an example, the resolution of the image represented by the video signal output from the personal computer 10 is VGA (Video Graphics Array) including 640 × 480 pixels on one screen.
Further, it is assumed that the projector device 1 is based on a specification that represents the minimum luminance to the maximum luminance with 256 gradations for each pixel.
<Configuration>
As shown in FIG. 3, the projector device 1 includes a control unit 101, a luminance correction unit 103, AD conversion processing units 104 to 106, input buffer units 107 to 109, output buffer units 110 to 112, and video signals. A processing unit 113 and a projection unit 116 are included.

Specifically, the projector device 1 includes a microprocessor, a ROM, a RAM, a lens, a light source lamp, a liquid crystal panel, a power supply unit, and the like. The RAM stores a computer program, and the microprocessor By operating according to the computer program, the projector device 1 achieves its functions.
The control unit 101 includes a microprocessor and its control program, and controls the overall operation of the projector apparatus 1.

The control unit 101 receives the luminance signal Y output from the personal computer 10 via the RGB / YPbPr input terminal 23, and detects the start timing and end timing of the vertical blanking period in the received luminance signal Y.
When the control unit 101 detects the start timing of the vertical blanking period, the control unit 101 transmits a correction start instruction to the luminance correction unit 103, and the luminance data accumulated in the input buffer unit 108 by the AD conversion processing unit 105 described later. All are copied to the output buffer unit 111 within the vertical blanking period, and all of the luminance data accumulated in the input buffer unit 109 by the AD conversion processing unit 106 described later is copied to the output buffer unit 112 within the vertical blanking period. .

The control unit 101 receives a correction end notification from the luminance correction unit 103 as a response to the correction start instruction.
Further, when the control unit 101 detects the end timing of the vertical blanking period, the control unit 101 instructs the video signal processing unit 113 to start signal processing, and also instructs the AD conversion processing units 104 to 106 at a predetermined timing. Instructs the start of AD conversion.

When the AD conversion processing unit 104 receives an AD conversion end notification that is output after the AD conversion is completed, the control unit 101 receives the Y conversion result of the luminance signal Y from the AD conversion result register included in the AD conversion processing unit 104. Data is read out and stored in the input buffer unit 107.
Here, the predetermined timing is a timing at which a luminance signal corresponding to each pixel constituting the image is input. That is, since the resolution of the image represented by the luminance signal Y is VGA, the control unit 101 transmits 640 × 480 AD conversion start instructions to the AD conversion processing unit 104 during the effective video period corresponding to one image. Then, 640 × 480 pieces of Y data are acquired from the AD conversion processing unit 104 and stored in the input buffer unit 107. One Y data as a result of AD conversion in the AD conversion processing unit 104 represents the luminance of one pixel in one image.

  When the AD conversion processing unit 105 receives an AD conversion end notification output after the AD conversion is completed, the control unit 101 indicates the AD conversion result of the color difference signal Pb from the AD conversion result register included in the AD conversion processing unit 105. The Pb data is read out and stored in the input buffer unit 108. Further, when the AD conversion processing unit 106 receives an AD conversion end notification output after AD conversion ends, Pr data that is the AD conversion result of the color difference signal Pr is received from the AD conversion result register included in the AD conversion processing unit 106. The data is read out and stored in the input buffer unit 109.

  Similarly, when receiving the AD conversion end notification from the AD conversion processing unit 105, the control unit 101 reads out Pb data that is an AD conversion result of the color difference signal Pb from the AD conversion result register included in the AD conversion processing unit 105. When the AD conversion processing unit 106 receives the AD conversion end notification from the AD conversion processing unit 106, the Pr data that is the AD conversion result of the color difference signal Pr is stored in the input buffer unit 108. Is stored in the input buffer unit 109.

As described above, the control unit 101 transmits an AD conversion start instruction 640 × 480 times to the AD conversion processing unit 105 during the effective video period, and 640 × 480 color difference signals Pb are transmitted from the AD conversion processing unit 105. Pb data which is the AD conversion result is acquired and stored in the input buffer unit 108.
Similarly, for the color difference signal Pr, the control unit 101 transmits 640 × 480 AD conversion start instructions to the AD conversion processing unit 106 during the effective video period, and 640 × 480 signals from the AD conversion processing unit 106. Pr data that is the AD conversion result of the color difference signal Pr is acquired and stored in the input buffer unit 109.

  Through the above-described control performed by the control unit 101, the projector device 1 performs luminance correction processing described later by the luminance correction unit 103 within the vertical blanking period, stores the luminance correction result in the output buffer unit 110, and performs vertical feedback. Outside the line period, an image that has been subjected to the luminance correction process is displayed based on the luminance data after the correction process stored in the output buffer unit 110. That is, as schematically shown in FIG. 4 as an example, the projector apparatus 1 receives and accumulates a video signal related to the image 1 from the personal computer 10 during a time t1 to t2 that is an effective video period. The luminance of the video signal related to the stored image 1 is corrected between times t2 and t3 which are vertical blanking periods.

The projector apparatus 1 receives the video signal related to the image 2 from the personal computer 10 during the next effective video period t3 to t4, and performs AD conversion and accumulation, and also the image 1 that is the corrected image 1 'Is projected, and the luminance of the video signal related to the stored image 2 is corrected during the next vertical blanking period from time t4 to t5.
The projector device 1 receives the video signal related to the image 3 during time t5 to t6, which is the next effective video period, stores it after AD conversion, and projects the image 2 ′, which is the corrected image 2.

Hereinafter, the projector device 1 repeats correcting the luminance during the vertical blanking period and projecting the corrected image within the effective video period.
The AD conversion processing unit 104 includes an AD conversion result register that is a readable register, receives the luminance signal Y output from the personal computer 10 via the RGB / YPbPr input terminal 23, and receives the AD signal from the control unit 101. When the conversion start instruction is received, AD conversion is executed, Y data as an AD conversion result is held in the AD conversion result register, and an AD conversion end notification is transmitted to the control unit 101.

  The AD conversion processing unit 105 includes an AD conversion result register that is a readable register, receives the color difference signal Pb output from the personal computer 10 via the RGB / YPbPr input terminal 23, and receives an AD conversion signal from the control unit 101. When the conversion start instruction is received, AD conversion is executed, Pb data as an AD conversion result is held in the AD conversion result register, and an AD conversion end notification is transmitted to the control unit 101.

  The AD conversion processing unit 106 includes an AD conversion result register that is a readable register, receives the color difference signal Pr output from the personal computer 10 via the RGB / YPbPr input terminal 23, and receives an AD conversion signal from the control unit 101. When the conversion start instruction is received, AD conversion is executed, Pr data as an AD conversion result is held in the AD conversion result register, and an AD conversion end notification is transmitted to the control unit 101.

Here, it is assumed that the AD conversion processing units 104 to 106 convert an input analog signal into 8-bit 256 gradation digital data.
The input buffer unit 107 is a buffer capable of storing Y data corresponding to 640 × 480 pixels for one screen.
The output buffer unit 110 is a buffer capable of accumulating Y ′ data, which is a result of correcting the Y data accumulated in the input buffer unit 107 by the luminance correction unit 103, for one screen.

The input buffer unit 108 and the output buffer unit 111 are buffers that can store Pb data corresponding to each pixel for one screen.
The input buffer unit 109 and the output buffer unit 112 are buffers that can store Pr data corresponding to each pixel for one screen.
When receiving the signal processing start from the control unit 101, the video signal processing unit 113 reads Y ′ data for one screen stored in the output buffer unit 110, and generates a luminance signal Y ′ from the read Y ′ data. Then, the Pb data for one screen stored in the output buffer unit 111 is read out, the color difference signal Pb ′ is generated from the read Pb data, and the Pr data for one screen stored in the output buffer unit 112 is obtained. The color difference signal Pb ′ is generated from the read Pr data, and the luminance signal Y ′, the color difference signal Pb ′, and the color difference signal Pr ′ are output to the projection unit 116.

Here, as described with reference to FIG. 4, the color difference signal Pb ′ is a signal obtained by delaying the color difference signal Pb by one screen, and the color difference signal Pr ′ is a signal obtained by delaying the color difference signal Pr by one screen. The luminance signal Y ′ is a signal obtained by correcting the luminance signal Y and delaying it by one screen.
The projection unit 116 receives the luminance signal Y ′, the color difference signal Pb ′, and the color difference signal Pr ′ from the video signal processing unit 113 and performs signal processing, thereby performing the luminance signal Y ′, the color difference signal Pb ′, and the color difference. An image generated from the signal Pr ′ is developed on the built-in liquid crystal panel and projected onto the screen 20.
(Luminance correction unit 103)
Next, the brightness correction unit 103 will be described in detail.

  The luminance correction unit 103 reads Y data one by one from the input buffer unit 107, corrects the input luminance data DI, which is the read Y data, to output luminance data DO by the following equation, and is corrected DO data. The Y ′ data is stored in the output buffer unit 110.

Details of the above formula will be described later. Moreover, although the fractional part of the calculation result in the brightness correction unit 103 is rounded off as an example, it may be rounded down or rounded up.
As shown in FIG. 5 as an example, the luminance correction unit 103 includes a luminance distribution detection circuit 301, a coefficient calculation circuit 302, a luminance level adjustment circuit 303, an external light detector 304, a correction value determination circuit 305, an offset level adjustment circuit 306, And an adder circuit 307.
(Luminance distribution detection circuit 301)
The luminance distribution detection circuit 301 receives a correction start instruction from the control unit 101, sequentially reads Y data for one screen stored in the input buffer unit 107, and counts the number of Y data for each luminance range.

  Specifically, for each Y data of one screen stored in the input buffer unit 107, a first luminance range whose value is 0 to 63, a second luminance range which is 64 to 127, and 128 to 191. It is determined which one of the third luminance range and the fourth luminance range of 192 to 255 belongs, and the number of Y data corresponding to the belonging luminance range is counted up. Thereby, regarding the Y data for one screen, the number of Y data belonging to each of the first to fourth luminance ranges can be counted.

Of the Y data for one screen, the number of Y data determined to belong to the first luminance range is F1, the number of Y data determined to belong to the second luminance range is F2, and the third luminance range is set. The number of Y data determined to belong is F3, and the number of Y data determined to belong to the fourth luminance range is F4.
6A shows an example of the distribution of the number of Y data for each luminance of 0 to 255 included in the Y data for one screen, and FIG. 6B shows the Y data having such a distribution. Based on this, the number of Y data belonging to each luminance range counted by the luminance distribution detection circuit 301 is graphed.

The luminance distribution detection circuit 301 notifies the coefficient calculation circuit 302 of the counted F1, F2, F3, and F4 for Y data for one screen.
(Coefficient calculation circuit 302)
When the coefficient calculation circuit 302 receives the number F1, F2, F3, and F4 of each luminance range from the luminance distribution detection circuit 301, the coefficient calculation circuit 302 calculates a correction coefficient Ci (i = 1 to 4) for correcting gradations by the following equation. Calculate using.

Here, i corresponds to the aforementioned luminance range, i = 1 corresponds to the first luminance range, i = 2 corresponds to the second luminance range, and i = 3 corresponds to the first luminance range. Corresponding to 3 luminance ranges, i = 4 corresponds to the fourth luminance range.
The coefficient calculation circuit 302 calculates all of C1 to C4.
Here, P is the total number of pixels in one image, and coincides with the total number of luminance data in one image, and Fi (i = 1 to 4) is data included in the i-th luminance range as described above. Represents the number of. That is,

It is.
The coefficient calculation circuit 302 notifies the luminance level adjustment circuit 303 of the calculated correction coefficient Ci in the order of C1, C2, C3, and C4.
(External light detector 304)
The external light detector 304 receives an electric signal generated by the external light sensor 28 according to the illuminance (0 to 400 lux as an example) of the received external light, and AD converts the electric signal with 8-bit resolution, The external light detector 304 that transmits the external light luminance data as the AD conversion result to the correction value determination circuit 305 is assumed to perform the above-described AD conversion processing once every 30 seconds as an example.
(Correction value determination circuit 305)
The correction value determination circuit 305 receives external light luminance data output by the external light detector 304 every 30 seconds, and a change amount ΔL between the received external light luminance data L2 and the previously received external light luminance data L1. = The correction value Q to be output is determined according to | L2-L1 |.

Q is the formula Q = L1 + G × (L2-L1)
Determined by
Specifically, the gain G is determined in the following cases (a) to (c) according to the value of ΔL.

The relationship between ΔL and G is as shown in the characteristic diagram of FIG. The vertical axis in FIG. 8 is the gain G, and the horizontal axis is ΔL. In FIG. 8, ls represents a gain change start position at which the gain G is changed with respect to the amount of fluctuation in external light, and le represents a start position at which the gain is maximized.
(A) When 0 ≦ ΔL ≦ ls Gain G is zero.

Therefore, Q = L1 + 0 × (L2-L1) = L1.
(B) When ls ≦ ΔL ≦ le The gain G is G = 0.1 × (ΔL−ls).
(C) When le ≦ ΔL ≦ 255, the gain G = 1.

Therefore, Q = L1 + 1 × (L2-L1) = L2.
Here, the correction values determined by the correction value determination circuit 308 will be described as an example where L1 = 10 and L2 = 20.
The correction value determination circuit 305 calculates ΔL = | 20−10 | = 10, and ΔL corresponds to the above (b), so the following calculation is performed.

G = 0.1 × (10 −5) = 0.5
Q = 10 + 0.5 × (20−10) = 15
From the above, the value of the correction value Q is determined to be “15”.
Here, the correction value Q will be supplementarily described.
In the above equation (1), DO corresponds to the above-described Y ′ data. When Q fluctuates, DO also fluctuates. However, when DO fluctuates, the image finally projected on the screen also causes a flicker phenomenon.

The correction value determination circuit 305 suppresses the above-described DO fluctuation by suppressing the Q fluctuation by not changing the gain G while ΔL is 0 to 1s.
And if ΔL changes the gain suddenly between ls and le, the brightness of the screen fluctuates. Therefore, according to the characteristics shown in FIG. 8, the gain is changed following the change in illuminance. The screen brightness can be changed according to the change in the external light level without feeling uncomfortable.

When ΔL is greater than le and the ambient illuminance changes, the gain is maximized.
As a result, when the gradation correction is performed by a sensor such as an illuminance sensor, the correction value determination circuit 305 performs gradation correction according to the amount of change in peripheral luminance, thereby suppressing the flicker phenomenon on the screen and providing a good image.
(Luminance level adjustment circuit 303)
The brightness level adjustment circuit 303 adjusts the correction coefficient Ci received from the coefficient calculation circuit 302 based on the correction value Q received from the correction value determination circuit 305. In other words, the luminance level adjustment circuit 303 uses the correction coefficient Q indicated by the correction value determination circuit to adjust the correction coefficient Ci according to the following equation to calculate Ci ′.

  The luminance level adjustment circuit 303 calculates DK by the following equation.

Here, DI is luminance data before correction and belongs to the nth luminance range (n is any one of 1 to 4).
The brightness level adjustment circuit 303 adjusts the correction coefficient, so that the correction coefficient has the corrected brightness data in the range from 0 to 255 as shown in FIG. As shown in FIG. 7B, proportional distribution is performed within a range from 0 to (255-Q).

The luminance level adjustment circuit 303 outputs the calculated DK to the adder 307.
The calculated C1 ′, C2 ′, C3 ′, and C4 ′ are output to the offset level adjustment circuit 306.
(Offset level adjustment circuit 306)
The offset level adjustment circuit 306 acquires C1 ′, C2 ′, C3 ′, and C4 ′ from the luminance level adjustment circuit 306, and acquires the correction value Q from the correction value determination circuit 305.

  The offset level adjustment circuit 306

Based on the above, DL is calculated, and the calculation result DL is output to the adder 307.
Due to the DL, even in the pixel with the lowest input luminance, the luminance is raised to the luminance Q according to the brightness signal.
Thus, the offset level adjustment circuit 305 generates DL for adjusting the luminance of each pixel belonging to the effective video period of the video luminance signal using the correction coefficient Ci ′ obtained by the luminance level adjustment circuit 303. .
(Adder 307)
The adder 307 acquires DK from the brightness level adjustment circuit 303, acquires DL from the offset level adjustment circuit 306, and adds DK and DL to obtain DO which is the addition result shown in Expression (1). Write to the output buffer unit 110.

The writing is performed at a predetermined address corresponding to the pixel corresponding to each luminance data after correction (supplementary explanation about luminance correction by the luminance correction unit 103).
Here, the luminance correction by the luminance correction unit 103 will be supplementarily described with reference to FIG.
As described above, the luminance correction unit 103 corrects the input luminance data DI to output luminance data DO.

FIG. 7A is a diagram illustrating a relationship between DI and DO when the luminance correction unit 103 performs correction using the correction coefficient Ci on the input luminance data DI.
Here, the slope of the graph shown by the solid line in FIG. 7A is Ci.
For example, when there is much luminance data included in the first luminance range for the correction target image, C1 is 1 or more, and output luminance data larger than the input luminance data is output.

For example, when C1 is 1.1 and the input luminance data is 30, the luminance correction unit 103 outputs the output luminance data 33.
FIG. 7B is a diagram illustrating a relationship between DI and DO when the luminance correction unit 103 performs correction only by multiplying the input luminance data DI by the correction coefficient Ci ′.
Here, the slope of the graph indicated by the solid line in FIG. 7B is Ci ′.

When the brightness correction unit 103 corrects using the correction coefficient Ci, as shown in FIG. 7A, when the DO is within the range from 0 to 255 as shown in FIG. 7A, the DO is corrected using the correction coefficient Ci ′. As shown in (b), the corrected DO is proportionally distributed within the range from 0 to (255-Q).
For example, if C1 is 1.1, Q is 30, and DI is 30, C1 ′ becomes C1 ′ = (256-30) /256×C1=1.05 from Equation (4), and DO1 Becomes 29.

FIG. 7C is a diagram illustrating the relationship between DI and DO when the luminance correction unit 103 performs the actual correction described so far.
Here, the slope of the graph shown by the solid line in FIG. 7C is Ci ′. Further, in FIG. 7C, compared to FIG. 7B, the luminance data of the entire screen is increased by the correction value Q.

For example, if C1 is 1.1, Q is 30, and DI is 30, C1 ′ becomes C1 ′ = (256-30) /256×C1=1.05 from Equation (4), and DO1 Is 29 + Q = 59.
<Operation>
Next, the operation of the projector device 1 will be described with reference to FIG. 9, particularly focusing on correction processing by the luminance correction unit 103.

  The projector device 1 receives the luminance signal Y, the color difference signal Pb, and the color difference signal Pr output from the personal computer 10 via the RGB / YPbPr input terminal 23. From the RGB / YPbPr input terminal 23, the control unit 101 and the AD conversion processing unit 104 receive the luminance signal Y, the AD conversion processing unit 105 receives the color difference signal Pb, and the AD conversion processing unit 106 receives the color difference signal Pr. .

The control unit 101 detects the end timing of the vertical blanking period, and instructs the AD conversion processing units 104 to 106 to start AD conversion at a predetermined timing (step S600).
Each of the AD conversion processing units 104 to 106 performs AD conversion, and transmits an AD conversion end notification to the control unit 101.
When the control unit 101 receives an AD conversion end notification from the AD conversion processing unit 104, the control unit 101 reads out Y data, which is an AD conversion result of the luminance signal Y, from the AD conversion result register included in the AD conversion processing unit 104, and inputs it. The data is stored in the buffer unit 107.

  Similarly, when receiving the AD conversion end notification from the AD conversion processing unit 105, the control unit 101 reads out Pb data that is an AD conversion result of the color difference signal Pb from the AD conversion result register included in the AD conversion processing unit 105. When the AD conversion processing unit 106 receives the AD conversion end notification from the AD conversion processing unit 106, the Pr data that is the AD conversion result of the color difference signal Pr is stored in the input buffer unit 108. Is stored in the input buffer unit 109.

Thereby, Y data for one screen is stored in the input buffer unit 107, Pb data for one screen is stored in the input buffer unit 108, and Pr data for one screen is stored in the input buffer unit 109.
Next, the control unit 101 detects the start timing of the vertical blanking period (step S601), transmits a correction start instruction to the luminance correction unit 103, and vertically converts all luminance data accumulated in the input buffer unit 108. All the luminance data copied to the output buffer unit 111 during the blanking period and accumulated in the input buffer unit 109 are copied to the output buffer unit 112 during the vertical blanking period (step S620).

The luminance distribution detection circuit 301 in the luminance correction unit 103 receives the correction start instruction, and the number of Y data belonging to the first to fourth luminance ranges in the Y data for one screen accumulated in the input buffer unit 107 , F1, F2, F3, and F4 are counted, and F1, F2, F3, and F4 are output to the coefficient calculation circuit 302 (step S602).
The coefficient calculation circuit 302 receives F1 to F4, calculates C1 to C4 using F1 to F4, and outputs them to the luminance level adjustment circuit 303 (step S603).

The external light sensor 28 receives external light, generates an electrical signal corresponding to the illuminance of the external light, and outputs it to the external light detector 304 (step S604).
The external light detector 304 receives the electric signal, AD converts the electric signal once every 30 seconds, and transmits external light luminance data as an AD conversion result to the correction value determination circuit 305.
When the external light luminance data is received, the correction value determination circuit 305 calculates the correction value Q using the external light luminance data received this time and the previous time, and transmits the correction value Q to the luminance level adjustment circuit 303 (step S605).

The luminance level adjustment circuit 303 receives C1 to C4 from the coefficient calculation circuit 302, receives the correction value Q from the correction value determination circuit 305, calculates C1 ′ to C4 ′ using C1 to C4 and Q, and C1 'To C4' is output to the offset level adjustment circuit 306 (step S606).
The luminance level adjustment circuit 303 determines whether or not the luminance data DI for one screen has been read from the input buffer unit 107 (step S607). If it is determined that it has not been read (step S607: NO), the DI to be read is determined. After reading one and determining the luminance range to which DI belongs, a value “n” indicating the nth luminance range is transmitted to the offset level adjustment circuit 306 (step S608).

The offset level adjustment circuit 306 uses the C1 to C4, n received from the brightness level adjustment circuit 303 and the Q received from the correction value determination circuit 305 to calculate DL by the above-described equation (6), The data is output to the adder 307 (step S609).
The luminance level adjustment circuit 303 calculates DK using the above-described equation (5) using n, C1 ′ to C4 ′, and DI, and outputs the DK to the adder 307 (step S610). .

The adder 307 adds DI and DK to generate DO, writes it in a location corresponding to DI in the output buffer unit 110, and proceeds to step S607 (step S611).
If it is determined in step S607 described above that reading of all DIs for one screen has been completed (step S607: YES), the process proceeds to step S612 described later.
The luminance correction unit 103 repeats steps S607 to S611 for the number of DIs for one screen, that is, the number of Y data.

The control unit 101 detects the end timing of the vertical blanking period (step S612).
When the control unit 101 succeeds in detecting the end timing of the vertical blanking period, the process proceeds to step S600.
When the control unit 101 detects the end timing of the vertical blanking period in step S612, the control unit 101 transmits a signal processing start instruction to the video signal processing unit 113 (step S621).

  When receiving the signal processing start from the control unit 101, the video signal processing unit 113 reads Y ′ data for one screen stored in the output buffer unit 110, and generates a luminance signal Y ′ from the read Y ′ data. Then, the Pb data for one screen stored in the output buffer unit 111 is read out, the color difference signal Pb ′ is generated from the read Pb data, and the Pr data for one screen stored in the output buffer unit 112 is obtained. The color difference signal Pb ′ is generated from the read Pr data, and the luminance signal Y ′, the color difference signal Pb ′, and the color difference signal Pr ′ are output to the projection unit 116.

The projection unit 116 generates an image based on the luminance signal Y ′ and the color difference signals Pb ′ and Pr ′ received from the video signal processing unit 113, develops the image on the built-in liquid crystal panel, and projects the image on the screen 20, and step S601. (Step S622).
<Summary>
As described above, the projector device according to the embodiment of the present invention calculates the correction coefficient Ci by detecting how many pixels of the luminance value are included in the image to be displayed. Since the luminance value is corrected using the correction coefficient Ci, an appropriate correction result corresponding to the luminance of the image to be displayed can be obtained.

  According to the present invention, an offset is added to the luminance value of a low-brightness pixel based on a correction table corresponding to the ambient light level, which has been caused by correction according to the prior art, even though there are many high-brightness pixels. Therefore, the contrast of the entire image is not lowered, and when the image includes many high-brightness pixels, a correction coefficient Ci that can obtain the contrast in the high-brightness pixels is calculated. Using the calculated Ci, it is possible to realize correction that improves the contrast of high-brightness pixels.

In addition, unlike the prior art, the ambient illuminance of external light is not directly reflected as an offset to the brightness value, but a correction value Q that is an offset is determined according to the amount of change in ambient illuminance and added to the brightness value. The occurrence of the flicker phenomenon due to the rapid change of the offset can be reduced.
<2. Second Embodiment>
Next, a second embodiment of the present invention will be described.

The projector device according to the present embodiment is substantially the same as the projector device according to the first embodiment, except that flesh-colored pixels are detected from the pixels in the image and the gradation is smoothly corrected.
In general, skin-colored pixels can easily recognize subtle differences in color tone, so if skin-colored pixels are included in a luminance range with a low frequency distribution, the gradation may be crushed. In the present embodiment, tone correction is not performed for the flesh color portion abruptly, but the correction amount is smoothly changed to correct the tone without impairing the tone of the flesh color portion in the image.

Hereinafter, the difference from the first embodiment will be mainly described.
As shown in FIG. 10, the projector device according to the present embodiment includes a control unit 101, a luminance correction unit 501, AD conversion processing units 104 to 106, an input buffer unit 107, input buffer units 502 to 503, and an output. The buffer units 110 to 112, the video signal processing unit 113, and the projection unit 116 are configured.

In the second embodiment, components having the same reference numerals as those in the first embodiment have the same functions.
The input buffer unit 502 is different from the input buffer unit 108 in that it is also read from the luminance correction unit 503 in addition to the output buffer unit 111. The input buffer unit 503 is a luminance correction unit in addition to the output buffer unit 112. It is different from the input buffer unit 109 in that the data is also read from 503.

As shown in FIG. 11, the luminance correction unit 501 includes a luminance distribution detection circuit 301, a coefficient calculation circuit 302, a luminance level adjustment circuit 511, an external light detector 304, a correction value determination circuit 305, an offset level adjustment circuit 306, and skin color detection. Circuit 512.
The skin color detection circuit 512 reads the Y data corresponding to each pixel from the input buffer unit 107, reads the Pb data of the pixel corresponding to the Y data from the input buffer unit 502, and converts the Y data from the input buffer unit 503 to the Y data. Read Pr data of the corresponding pixel and use the Y data, Pb data, and Pr data to generate R data, G data, and B data representing the chromaticities of the three primary colors red, green, and blue To do.

R, G, and B satisfy the following relationship.
Pb = B−Y = 0.30R−0.39G−0.89B
Pr = R−Y = 0.70R−0.59G−0.11B
Using the red component R data, green component G data, and blue component B data of the pixel, it is determined whether or not the pixel contains a large amount of white component.

If the values of R data, G data, and B data are approximately the same, the pixel is close to white, so the skin color detection circuit 512 determines whether or not the white component of the pixel contains a large amount of R data. It is determined whether the values of the G data and the B data are about the same, and as an example, the difference between the values of the R, G, and B data is within a threshold value (20 as an example).
When it is determined that a large amount of the white component of the pixel is included, the skin color detection circuit 512 transmits a correction coefficient adjustment notification to the luminance level adjustment circuit 511.

When the correction coefficient adjustment notification is received, the luminance level adjustment circuit 511 uses the value of C1 to C4 multiplied by the adjustment coefficient.
As an example, the luminance level adjustment circuit 511 uses 0.5 as an adjustment coefficient.
FIG. 12 is a diagram illustrating the relationship between DI and DO when the luminance correction unit 501 performs correction using the correction coefficient Ci ″ on the input luminance data DI. For pixels for which the white component is determined to be greater than or equal to the threshold, adjustment is made to C1 to C4, which is the slope of the graph 702, instead of the correction coefficients C1 to C4 that are the slope of the graph 701 that does not consider skin color correction. Input luminance data is converted to output luminance data using C1 ″ to C4 ″ multiplied by a coefficient of 0.5.
<3. Third Embodiment>
Next, a third embodiment of the present invention will be described.

The projector device according to the present embodiment is substantially the same as the projector device according to the first embodiment, but calculates the average luminance of the image, adjusts the correction coefficient Ci (i = 1 to 4), and prevents overcorrection. It is different in point.
For example, an image with a lot of dark luminance components, such as an image showing the night sky, may result in a bright and floating image if the image is excessively over-corrected. If an overcorrection is performed on an image having many bright luminance components such as an image, the landscape may become dark. In this embodiment, such an excessive overcorrection is prevented.

Hereinafter, the difference from the first embodiment will be mainly described.
The projector apparatus of this embodiment is obtained by replacing the luminance correction unit 103 of the first embodiment with a luminance correction unit 530. The luminance correction unit 530 includes a luminance distribution detection circuit 301, a coefficient, as shown in FIG. The calculation circuit 302, the luminance level adjustment circuit 531, the external light detector 304, the correction value determination circuit 305, the offset level adjustment circuit 306, and the average luminance calculation circuit 532 are configured.

The average luminance calculation circuit 532 relates to all the pixels included in one image stored in the input buffer unit 107 in parallel with the detection of the luminance distribution by the luminance distribution detection circuit 301 described in the first embodiment. The average luminance of the luminance indicated by the Y data is calculated, and the average luminance is notified to the luminance level adjustment circuit 531.
The luminance level adjustment circuit 531 receives the average luminance, and, when the average luminance is equal to or higher than a predetermined upper limit value, multiplies the correction coefficient Ci by a predetermined upper limit adjustment coefficient (0.3 as an example). use.

Similarly, when the average luminance is equal to or lower than a predetermined lower limit value, the luminance level adjustment circuit 531 uses a predetermined lower limit adjustment coefficient (for example, 0.2) multiplied by the correction coefficient Ci.
Here, the lower limit adjustment coefficient and the upper limit adjustment coefficient are not distinguished, and the same coefficient may be used by multiplying the correction coefficient Ci.
FIG. 14 is a diagram illustrating a relationship between DI and DO when the luminance correction unit 530 performs correction using the correction coefficient Ci ″ on the input luminance data DI. When it is determined that the average luminance is equal to or lower than the predetermined lower limit value, correction coefficients C1 to C4 indicated by the slope of the graph 711 that does not consider the average luminance when correcting the luminance value related to the pixels of the entire image. Instead, as indicated by the slope of the graph 712, the input luminance data is converted into the output luminance data using C1 ″ to C4 ″ obtained by multiplying C1 to C4 by the adjustment coefficient 0.2.
<4. Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described.

The projector device according to the present embodiment is substantially the same as the projector device according to the first embodiment, but differs in that the black level of the image is further corrected after the gradation is corrected.
The projector apparatus of this embodiment is obtained by replacing the luminance correction unit 103 of the first embodiment with a luminance correction unit 550. The luminance correction unit 550 includes a luminance distribution detection circuit 301, a coefficient, as shown in FIG. The calculation circuit 302, the luminance level adjustment circuit 551, the external light detector 304, the correction value determination circuit 305, the offset level adjustment circuit 306, and the black level correction circuit 552 are configured.

The black level correction circuit 552 reduces the luminance of the low luminance part.
FIG. 16 is a diagram illustrating the relationship between DI and DO when the luminance correction unit 550 performs correction using the correction coefficient Ci ″ on the input luminance data DI, and the output luminance data is predetermined. When the luminance value related to the pixels of the entire image is corrected, the correction coefficient C1 ′ indicated by the slope of the graph 721 below the predetermined lower limit value is represented by a graph 722. When the input luminance data is 0, the correction coefficient C1 ″ is converted so that the output luminance data becomes 0.

Therefore, in the first embodiment, when the correction value Q is large due to strong external light or the like, it may be considered that the luminance of the lowest luminance portion after the correction becomes high and the screen floats. In this embodiment, since the black level correction circuit 552 lowers the luminance of the low luminance portion, the blackness can be sharpened and the video can be tightened.
The black level correction circuit 552 reduces the output luminance of the low luminance portion by smoothly adjusting the output luminance data corresponding to the input luminance data.
<5. Fifth Embodiment>
Next, a fifth embodiment of the present invention will be described.

The projector device according to this embodiment is substantially the same as the projector device according to the first embodiment, but corrects the luminance distribution by detecting the minimum and maximum luminance values during the effective video period of the video luminance signal. It is different in point.
The projector device of this embodiment is obtained by replacing the brightness correction unit 103 of the first embodiment with a brightness correction unit 570. The brightness correction unit 570 includes a brightness level adjustment circuit 571, a brightness level adjustment circuit 571, and a brightness level adjustment circuit 571 as shown in FIG. A distribution detection circuit 572, a maximum value detection circuit 573, a minimum value detection circuit 574, a coefficient calculation circuit 302, an external light detector 304, a correction value determination circuit 305, and an offset level adjustment circuit 306 are configured.

The maximum value detection circuit 573 detects the maximum value of the Y data stored in the input buffer unit 107 and transmits the maximum value to the luminance distribution detection circuit 572.
The minimum value detection circuit 574 detects the minimum value of Y data and transmits the minimum value to the luminance distribution detection circuit 572.
The luminance distribution detection circuit 572 distributes the luminance frequency distributed in the range from the received minimum value to the maximum value in the range from 0 to 255 to obtain a luminance distribution.

  FIG. 18 is a diagram illustrating the relationship between DI and DO when the luminance correction unit 570 performs correction using the correction coefficient Ci ″ on the input luminance data DI. In place of the correction coefficient Ci indicated by the slope of the graph 731, Ci is changed from the input luminance within the range from the minimum value to the maximum value during the effective video period of the video luminance signal to the luminance within the range of 0 to 255. The input luminance data is corrected to output luminance data using the correction coefficient Ci ″ converted as described above.

In this way, it is possible to further enhance the visibility by further enhancing the contrast of the image.
<6. Sixth Embodiment>
Next, a sixth embodiment of the present invention will be described.
The projector device according to the present embodiment is substantially the same as the projector device according to the first embodiment, but differs in that the video color signal is corrected by the amount of change in the input / output of the video luminance signal.

Hereinafter, the difference from the first embodiment will be mainly described.
As shown in FIG. 19, the projector apparatus according to the present embodiment replaces the luminance correction unit 103 of the first embodiment with a luminance correction unit 590, replaces the input buffer unit 108 with an input buffer unit 502, and inputs the input buffer unit 109. The buffer unit 503 is replaced, the output buffer unit 111 is replaced with the output buffer unit 591, and the output buffer unit 112 is replaced with the output buffer unit 592.

The input buffer unit 502 is different from the input buffer unit 108 in that it is connected to the luminance correction unit 590, and the input buffer unit 503 is different from the input buffer unit 108 in that it is connected to the luminance correction unit 590.
The output buffer unit 591 is different from the output buffer unit 111 in that it is connected to the luminance correction unit 590, and the output buffer unit 592 is different from the output buffer unit 112 in that it is connected to the luminance correction unit 590.

As shown in FIG. 20, the luminance correction unit 590 includes a luminance distribution detection circuit 301, a coefficient calculation circuit 302, a luminance level adjustment circuit 595, an external light detector 304, a correction value determination circuit 305, an offset level adjustment circuit 306, and color adjustment. Circuit 596.
The color adjustment circuit 596 acquires the luminance data DI before correction and the luminance data DO after correction, reads Pb data related to the same pixel as the luminance data DI from the input buffer unit 502, and converts the Pb data to DO / Multiply DI and store in output buffer 591. Similarly, the Pr data relating to the same pixel as the luminance data DI is read from the input buffer unit 503, and the Pr data is multiplied by DO / DI and stored in the output buffer unit 592.

As described above, the luminance data is corrected and the color difference data of the pixel related to the luminance data is also corrected. Therefore, by increasing only the luminance data by correction, the color of the pixel related to the luminance data becomes lighter. Therefore, it is possible to display an image with excellent contrast and color and excellent visibility.
<Modification>
The embodiment described above is an example of the implementation of the present invention, and the present invention is not limited to this embodiment at all, and can be implemented in the main mode without departing from the scope of the present invention. . The following cases are also included in the present invention.

(1) In the above embodiment, the projector apparatus has been described as an example. However, the present invention is not limited to this, and the present invention may be applied to an image output apparatus other than the projector apparatus. In particular, it is suitable for application to an image output apparatus that makes it difficult to see the screen due to the influence of external light or the like.
(2) In the above embodiment, the case where the external light sensor is exclusively attached to the projector apparatus main body has been described. However, it goes without saying that the present invention is not limited to this, and the external light sensor is integrated with the projector apparatus main body. Even if it is not, the effect of the present invention can be obtained. For example, an external light sensor may be attached to the front of the screen in order to measure the intensity of external light incident on the screen. The external light sensor may be removed from the projector device and used so that the brightness can be measured at an appropriate position according to the environment in which the projector device is used.

(3) In the above embodiment, the case where the correction coefficient is determined by dividing the luminance of 256 gradations into four stages has been described, but it goes without saying that the present invention is not limited to this and a plurality of stages other than four. The correction coefficient may be determined separately. Further, even if the number of gradations other than 8 bits: 256 gradations such as 10 bits: 1024 gradations is used, the effect of the present invention is not changed.
(4) Although not particularly mentioned in the above embodiment, the image processing apparatus according to the present invention is a program that receives a signal indicating the intensity of external light and executes the above-described tone correction. It may be a dedicated LSI (Large Scale Integration).

  (5) In the above embodiment, the case where the correction coefficient Ci ′ is obtained by adjusting all the correction coefficients Ci (i = 1 to 4) has been described, but it goes without saying that the present invention is not limited to this. The correction coefficient Ci may be adjusted only for the low luminance part. In this case, the coefficient to be adjusted may be only the correction coefficient C1 of the portion having the lowest luminance, or C1 and C2, or C1 to C3 may be adjusted.

(6) Although not particularly mentioned in the above embodiment, the value of the correction coefficient Q in the first embodiment may be up to about 80 in the case of 256 gradations. In the case of 512 gradations, it may be at most about 160. In this way, problems such as a decrease in contrast due to narrowing of the output luminance range can be minimized.
(7) In the above embodiment, when calculating the average luminance level of the image, all the pixels of the image are sampled. However, thinning sampling such as every two pixels or every four pixels may be performed. In this way, the circuit scale can be reduced.

  (8) The present invention may be the method described above. Further, the present invention may be a computer program that realizes these methods by a computer, or may be a digital signal composed of the computer program. The present invention also provides a computer-readable recording medium such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray Disc). ), Recorded in a semiconductor memory or the like. Further, the present invention may be the computer program or the digital signal recorded on these recording media. In the present invention, the computer program or the digital signal may be transmitted via an electric communication line, a wireless or wired communication line, a network represented by the Internet, or the like. The present invention may be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor operates according to the computer program. In addition, the program or the digital signal is recorded on the recording medium and transferred, or the program or the digital signal is transferred via the network or the like, and is executed by another independent computer system. It is good.

(9) The above embodiment and the above modifications may be combined.

The image output apparatus of the present invention is used particularly when displaying an image under the influence of external light, and is manufactured, sold, etc. by a manufacturer who handles electrical equipment.

It is a block diagram which shows the structure of the projector apparatus which concerns on one Embodiment of this invention. 1 is an external view of a projector device according to an embodiment of the present invention. It is a block diagram which shows the internal structure of the projector apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically the display timing of the output image with respect to an input image. It is a block diagram which shows the internal structure of the brightness correction part which concerns on one Embodiment of this invention. It is a graph which illustrates the luminance distribution in the effective image | video period of the luminance signal for 1 screen. It is a figure which shows typically the relationship between the data before adjustment about the brightness | luminance data adjusted by a brightness correction part, and after adjustment. It is the schematic which shows the relationship between the variation | change_quantity of external light, and the correction value to output. It is a flowchart which shows the correction process by the projector apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the internal structure of the projector apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the internal structure of the brightness correction part which concerns on 2nd Embodiment. It is a figure explaining the correction coefficient computed by the brightness correction part concerning a 2nd embodiment. It is a block diagram which shows the internal structure of the brightness correction part which concerns on 3rd Embodiment. It is a figure explaining the correction coefficient computed by the brightness correction part concerning a 3rd embodiment. It is a block diagram which shows the internal structure of the brightness correction part which concerns on 4th Embodiment. It is a figure explaining the correction coefficient computed by the brightness correction part concerning a 4th embodiment. It is a block diagram which shows the internal structure of the brightness correction part which concerns on 5th Embodiment. It is a figure explaining the correction coefficient computed by the brightness correction part concerning a 5th embodiment. It is a block diagram which shows the internal structure of the projector apparatus which concerns on 6th Embodiment. It is a block diagram which shows the internal structure of the brightness correction part which concerns on 6th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Projector apparatus 10 Personal computer 20 Screen 23 RGB / YPbPr input terminal 28 External light sensor 101 Control part 103 Brightness correction part 104-106 AD conversion process part 107-109 Input buffer part 110-112 Output buffer part 113 Video signal process part 116 Projection unit 301 Luminance distribution detection circuit 302 Coefficient calculation circuit 303 Luminance level adjustment circuit 304 External light detector 305 Correction value determination circuit 306 Offset level adjustment circuit 307 Adder

Claims (11)

An image output apparatus for correcting and outputting the brightness of an original image according to the intensity of external light,
Storage means for storing an original image in which each pixel is expressed in luminance according to a predetermined specification;
Counting means for counting the number of pixels in which the luminance value of each pixel of the original image is included for each of the luminance sections obtained by equally dividing the entire luminance area based on the specification;
A photometric means for measuring external light intensity;
An external light converting means for converting the external light intensity into an offset value related to luminance;
By dividing the total number of pixels in the original image by the number of luminance intervals, the number of interval pixels is calculated. For each luminance interval, the number of pixels including the luminance value is divided by the number of interval pixels, and the division result is calculated. , ((The upper limit value of the entire luminance region−the offset value) / the upper limit value of the entire luminance region),
Section added value calculation means for calculating an added value by multiplying the difference value between the upper limit value and the lower limit value of the brightness section by a conversion coefficient related to the brightness section;
Regarding the luminance value of each pixel,
An adjustment value obtained by adjusting the added value counted for the luminance interval including the luminance value based on the position of the luminance value in the luminance interval;
A total addition value calculated by the section addition value calculation means for each of the luminance sections in which the upper limit value of the luminance section is smaller than the lower limit value of the luminance section including the luminance value;
An image output apparatus comprising: conversion means for replacing the brightness value with a corrected brightness value obtained by adding the offset value . The photometric means measures the external light intensity a plurality of times,
The external light converting means is
An outside light intensity correction unit that calculates the amount of change in outside light intensity and corrects the recently measured outside light intensity based on the amount of change;
An external light conversion unit that converts the corrected external light intensity into the offset value according to proportional conversion that proportionally distributes a range from a lower limit value to an upper limit value of the external light intensity to the entire luminance range. The image output apparatus according to claim 1 . The external light intensity correction unit is
A difference calculation unit for calculating a difference between the external light intensity measured last time and the external light intensity measured most recently;
When the difference is less than a predetermined lower limit value, output the external light intensity measured last time, and when the difference is greater than a predetermined upper limit value, output the external light intensity measured most recently, 3. The image output according to claim 2 , further comprising: an adjustment unit that multiplies the external light intensity measured last time by a predetermined coefficient and outputs the difference when the difference is not less than a predetermined lower limit value and not more than a predetermined upper limit value. apparatus. The image output device further includes:
When the minimum corrected luminance value that is the minimum among the corrected luminance values related to the original image is larger than a predetermined threshold, the lower limit value of the minimum luminance section in the minimum luminance section that is the luminance section that includes the lower limit value of the entire luminance area. Black for correction that proportionally distributes the range from the corrected luminance value to the corrected luminance value related to the upper limit value of the minimum luminance interval to the range from the lower limit value of the minimum luminance interval to the corrected luminance value related to the upper limit value of the minimum luminance interval The image output apparatus according to claim 3, further comprising a correction unit. The conversion means adjusts the adjustment value in proportion to the difference between the lower limit value of the luminance interval including the luminance value and the luminance value to the addition value counted for the luminance interval including the luminance value. The image output device according to claim 1, wherein the image output device is calculated by multiplying The image output device further includes:
Skin color judging means for judging whether the hue of each pixel is a skin color,
The image output apparatus according to claim 1, wherein the conversion unit multiplies the addition value calculated by the section addition value calculation unit for each luminance section by a predetermined number for pixels determined to be skin color. . The image output device further includes:
Average luminance calculation means for calculating an average luminance value of the original image,
The image output apparatus according to claim 1, wherein the conversion unit multiplies the addition value calculated by the section addition value calculation unit by a predetermined number when the average luminance value is equal to or less than a predetermined value. The image output device further includes:
A maximum / minimum value detecting means for detecting a maximum value and a minimum value of luminance values of pixels included in the original image;
The conversion means calculates the addition value calculated by the section addition value calculation means in each luminance section as ((the upper limit value of the entire luminance area−the lower limit value of the entire luminance area) / (of the pixels included in the original image). 2. The image output device according to claim 1, wherein the maximum value of the luminance value−the minimum value of the luminance value of the pixels included in the original image)) is multiplied. The image output device further includes:
The color adjustment unit for correcting the color difference value by multiplying the color difference value of each pixel by (the luminance value after correction by the conversion unit / the luminance value before correction by the conversion unit). 2. The image output apparatus according to 1. An image output method used in an image output device that stores an original image in which each pixel is expressed in luminance with a predetermined specification, and corrects and outputs the luminance of the original image according to the intensity of external light,
A counting step for counting the number of pixels including the luminance value of each pixel of the original image for each of the luminance sections obtained by equally dividing the entire luminance area based on the specification;
A photometric step for measuring the external light intensity;
An external light conversion step of converting external light intensity into an offset value related to luminance;
By dividing the total number of pixels in the original image by the number of luminance intervals, the number of interval pixels is calculated. For each luminance interval, the number of pixels including the luminance value is divided by the number of interval pixels, and the division result is calculated. , ((The upper limit value of the entire luminance region−the offset value) / the upper limit value of the entire luminance region), and a conversion coefficient calculating step for outputting the result as a conversion coefficient;
A section addition value calculating step of calculating an addition value by multiplying the difference value between the upper limit value and the lower limit value of the brightness section by a conversion coefficient related to the brightness section;
Regarding the luminance value of each pixel,
An adjustment value obtained by adjusting the added value counted for the luminance interval including the luminance value based on the position of the luminance value in the luminance interval;
A total addition value calculated by the section addition value calculation means for each of the luminance sections in which the upper limit value of the luminance section is smaller than the lower limit value of the luminance section including the luminance value;
A conversion step of replacing the luminance value with a corrected luminance value obtained by adding the offset value . A computer program used for an image output device that stores an original image in which each pixel is expressed in luminance according to a predetermined specification, corrects the luminance of the original image according to the intensity of external light, and outputs the corrected image.
A counting step for counting the number of pixels including the luminance value of each pixel of the original image for each of the luminance sections obtained by equally dividing the entire luminance area based on the specification;
A photometric step for measuring the external light intensity;
An external light conversion step of converting external light intensity into an offset value related to luminance;
By dividing the total number of pixels in the original image by the number of luminance intervals, the number of interval pixels is calculated. For each luminance interval, the number of pixels including the luminance value is divided by the number of interval pixels, and the division result is calculated. , ((The upper limit value of the entire luminance region−the offset value) / the upper limit value of the entire luminance region), and a conversion coefficient calculating step for outputting the result as a conversion coefficient;
A section addition value calculating step of calculating an addition value by multiplying the difference value between the upper limit value and the lower limit value of the brightness section by a conversion coefficient related to the brightness section;
Regarding the luminance value of each pixel,
An adjustment value obtained by adjusting the added value counted for the luminance interval including the luminance value based on the position of the luminance value in the luminance interval;
A total addition value calculated by the section addition value calculation means for each of the luminance sections in which the upper limit value of the luminance section is smaller than the lower limit value of the luminance section including the luminance value;
A computer program comprising: a conversion step of replacing the luminance value with a corrected luminance value obtained by adding the offset value .

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