Image signal converting apparatus and image display apparatus

The image signal converting apparatus is used in a lighting unit. The lighting unit includes a liquid crystal panel modulating a red component light according to a red image signal, a liquid crystal panel modulating a green component light according to a green image signal, and a liquid crystal panel modulating a blue component light according to a blue image signal. Yellow component light is superimposed on any of the red component light, the green component light and the blue component light. The image signal converting apparatus includes a controlling unit which controls a superimposition amount of yellow component light based on a specific image signal among a red image signal, a green image signal, and a blue image signal. A color corresponding to the specific image signal has a hue adjacent to a hue corresponding to the yellow component light. The controlling unit controls a reduction amount of the specific image signal based on the superimposition amount.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2007-258087, filed on Oct. 1, 2007; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image signal converting apparatus and an image display apparatus using fourth color component light in addition to red component light, green component light and blue component light.

2. Description of the Related Art

Three-plate projection image display apparatuses have heretofore been widely known, which include a red liquid crystal panel modulating a red component light, a green liquid crystal panel modulating a green component light and a blue liquid crystal panel modulating a blue component light.

To increase luminance and to reduce power consumption, proposed is a projection image display apparatus which uses fourth color component light (e.g., yellow component light) in addition to red component light, green component light, and blue component light (e.g., Japanese Patent Application Publication No. 2002-287247 (claims 1 and 4, FIG. 1 and the like)).

Specifically, in such projection image display apparatus, an improvement of the luminance of an image projected on a screen can be achieved by using yellow component light in addition to red component light, green component light and blue component light.

However, in the above-described projection image display apparatus, a mere addition of the yellow component light causes an image to be shifted to the yellow side. Thus, color reproducibility of the image is deteriorated by using the yellow component light.

SUMMARY OF THE INVENTION

A first aspect of the invention is summarized as an image signal converting apparatus used in a lighting apparatus that includes a red-light imager (liquid crystal panel30R) modulating a red component light according to a red image signal, a green-light imager (liquid crystal panel30G) modulating a green component light according to a green image signal, and a blue-light imager (liquid crystal panel30B) modulating a blue component light according to a blue image signal, in the lighting apparatus, a fourth color component light being superimposed on any of the red component light, the green component light, and the blue component light. The image signal converting apparatus comprises a controlling unit (controlling unit130) for controlling a superimposition amount of the fourth color component light based on a specific image signal among the red image signal, the green image signal, and the blue image signal. A color corresponding to the specific image signal is one having a hue adjacent to a hue corresponding to the fourth color component light. The controlling unit controls a reduction amount of the specific image signal based on the superimposition amount.

According to this aspect, the color corresponding to the specific image signal is one having a hue adjacent to a hue corresponding to the fourth color component light. The controlling unit controls a reduction amount of the specific image signal based on the superimposition amount.

Therefore, while intending to improve the luminance of an image by using the fourth color component light, deterioration of color reproducibility of the image caused by the use of fourth color component light can be controlled.

According to this aspect, the controlling unit controls the superimposition amount using a color reproduction parameter α for controlling a light amount of the fourth color component light. The color reproduction parameter α is a parameter determined so that the light amount of the fourth color component light increases along with an increase in saturation of an image.

According to this aspect, the controlling unit controls the superimposition amount using a luminance parameter β1for controlling a light amount of the fourth color component light. The luminance parameter β1is a parameter determined so that the light amount of the fourth color component light decreases along with an increase in saturation of an image.

According to this aspect, the controlling unit controls the superimposition amount using a luminance parameter β2for controlling a light amount of the fourth color component light. The luminance parameter β2is a parameter determined so that the light amount of the fourth color component light increases until the luminance of an image reaches a predetermined threshold value, and that the light amount of the fourth color component light decreases after the luminance of the image exceeds the predetermined threshold value.

A second aspect of the invention is summarized as an image display apparatus that includes a red-light imager modulating a red component light according to a red image signal, a green-light imager modulating a green component light according to a green image signal, and a blue-light imager modulating a blue component light according to a blue image signal. A fourth color component light is superimposed on any of the red component light, the green component light, and the blue component light. The image display apparatus comprises a color combining unit (cross dichroic cube60) for combining red component light emitting from the red light imager, green component light emitting from the green light imager, and blue component light emitting from the blue light imager. The image display apparatus also comprises a controlling unit (controlling unit130) for controlling a superimposition amount of the fourth color component light based on a specific image signal among the red image signal, the green image signal, and the blue image signal. A color corresponding to the specific image signal is one having a hue adjacent to a hue corresponding to the fourth color component light. The controlling unit controls a reduction amount of the specific image signal based on the superimposition amount.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the embodiments of the present invention are described with reference to the accompanying drawings. Note that, in the description of the following drawings, the same or similar parts are denoted by the same or similar symbols.

However, it should be noted that the drawings are diagrammatical and each dimension ratio is different from the actual one. Therefore, the following description should be taken into consideration to judge specific dimensions and the like. Also, a part in which dimensional relationship and ratio are different between drawings is of course included.

(Schematic Description of Projection Image Display Apparatus)

A summary of a projection image display apparatus of the first embodiment is described below with reference to drawings.FIG. 1is a schematic diagram of the projection image display device100of the first embodiment of the invention.

As shown inFIG. 1, the projection image display apparatus100includes a projection lens unit110, and projects image light magnified by the projection lens unit110on a screen200. As described later, the projection image display apparatus100uses yellow component light as fourth color component light in addition to red component light, green component light and blue component light.

(Schematic Configuration of Lighting Unit)

A schematic configuration of a lighting unit of the first embodiment is described below with reference to the drawings.FIG. 2is a view showing a schematic configuration of the lighting unit120of the first embodiment. It should be noted that inFIG. 2, fly-eye lenses which uniformize light emitted from a light source10, a Polarized Beam Splitter (PBS) which aligns a polarization direction of the light emitted from the light source10, and the like are omitted.

As shown inFIG. 2, the lighting unit120includes the light source10, a plurality of liquid crystal panels30(a liquid crystal panel30R, a liquid crystal panel30G, a liquid crystal panel30B and a liquid crystal panel30Ye), and a cross dichroic cube60. Incidentally, it should be noted that inFIG. 2, while being depicted, the projection lens unit110is not included in the lighting unit120.

The light source10is a UHP lump which emits white light. That is, light emitted from the light source10at least includes the red component light, the green component light, the blue component light and the yellow component light. Further, as shown inFIG. 3, among red, green, and blue, red and green are colors having hues adjacent to yellow.

In addition, when using three primary colors (red, green and blue) of light, in a broad sense, it may be considered that a complementary color of red is cyan, a complementary color of green is magenta, and a complementary color of blue is yellow.

Further, the yellow component light is superimposed on any one of or on both of the red component light and the green component light. In this embodiment, the yellow component light is superimposed on the red component light, and enters the liquid crystal panel30R.

As described later, the liquid crystal panel30R modulates the red component light according to a red image signal (a red output signal Routcalculated from a red input signal Rin). In addition, on the light entering side and the light emitting side of the liquid crystal panel30R, a pair of polarizing plates (not shown) is provided.

Similarly, the liquid crystal panel30G modulates the green component light according to a green image signal (a green output signal Goutcalculated from a green input signal Gin), and the liquid crystal panel30B modulates the blue component light according to a blue image signal (a blue output signal Boutcalculated from a blue input signal Bin). In addition, on the light entering sides and the light emitting sides of the liquid crystal panel30G and the liquid crystal panel30B, pairs of polarizing plates (not shown) are provided.

Meanwhile, the liquid crystal panel30Ye modulates the yellow component light according to a control signal (yellow control signal) calculated based on specific image signals (a red image signal and a green image signal). In addition, at least on one of the light entering side and the light emitting side of the liquid crystal panel30Ye, a polarizing plate (not shown) may be provided.

Here, colors (red and green) corresponding to the specific image signals (the red image signal and the green image signal) have hues adjacent to hue corresponding to the fourth color component light (yellow component light).

Light emitting from the liquid crystal panel30Ye enters the liquid crystal panel30R. That is, the liquid crystal panel30R is disposed on a light path of the light emitting from the liquid crystal panel30Ye, and is in between a position where light emits from the liquid crystal panel30Ye and a position where the light emitting therefrom enters a cross dichroic cube60.

Incidentally, it should be noted that the control of a modulation amount of the liquid crystal panel30Ye is to control an amount of the yellow component light passing through the liquid crystal panel30Ye. That is, the control of a modulation amount of the liquid crystal panel30Ye is a control of a superimposition amount of yellow component light which is superimposed on the red component light.

It is preferable that light emitting from the liquid crystal panel30Ye cause an image to be substantially formed on the liquid crystal panel30R. For example, between the liquid crystal panel30Ye and the liquid crystal panel30R, relay lenses (a lens86, a lens87, and a lens83) and the like are disposed on the light path of light emitting from the liquid crystal panel30Ye. Thus, it becomes possible for the light emitting from the liquid crystal panel30Ye to cause an image to be substantially formed on the liquid crystal panel30R. It should be noted here that the substantial formation of an image is a concept including image formation.

Resolution of the liquid crystal panel30Ye is different from those of the liquid crystal panels30R,30G, and30B. Specifically, to display a fine image on the screen200, the liquid crystal panels30R,30G, and30B have high resolution. Meanwhile, light emitting from the liquid crystal panel30Ye is mainly used as illumination light. Therefore, in order not to deteriorate use efficiency of light due to electrodes provided to the liquid crystal panel, it is preferable that the resolution of the liquid crystal panel30Ye is lower than those of the liquid crystal panels30R,30G, and30B. Since it is only necessary to adjust the amount of the yellow component light for each target region, it is sufficient even if the resolution of the liquid crystal panel30Ye is low.

Incidentally, what is meant by low resolution is a concept including a case where the liquid crystal panel30Ye does not have a resolution. Accordingly, the liquid crystal panel30Ye is not necessarily configured so that it is capable of controlling an amount of modulation for each of a plurality of regions, and may have a configuration in which an amount of modulation of only the entire surface is controlled.

Further, the resolution of the liquid crystal panel30Ye may be the same as those of the liquid crystal panels30R,30G, and30B.

The cross dichroic cube60is a color combining unit for combining light emitting from the liquid crystal panels30R,30G, and30B. That is, the cross dichroic cube60synthesizes the red component light and the yellow component light emitting from the liquid crystal panel30R, the green component light emitting from the liquid crystal panel30G and the blue component light emitting from the liquid crystal panel30B. The cross dichroic cube60emits synthesis light (image light) including the red component light, the green component light, the blue component light, and the yellow component light to the side of the projection lens unit110.

The projection lens unit110projects, on the screen200, the synthesis light (image light) synthesized by the cross dichroic cube60as described above.

Returning toFIG. 2, the lighting unit120includes a plurality of mirrors (mirrors21to27). The mirror21is a dichroic mirror which transmits the blue component light and reflects other light including the red component light, the green component light and the yellow component light. The mirror22is a mirror which reflects the blue component light toward the liquid crystal panel30B. The mirror23is a dichroic mirror which reflects the green component light toward the liquid crystal panel30G and which transmits other light including the red component light and the yellow component light. The mirror24is a dichroic mirror which reflects the red component light toward the liquid crystal panel30R and which transmits other light including the yellow component light. The mirror25is a mirror which reflects the yellow component light toward the liquid crystal panel30Ye. The mirror26is a mirror which reflects the yellow component light toward the liquid crystal panel30R. The mirror27is a dichroic mirror which transmits light (yellow component light) emitting from the liquid crystal panel30Ye and which reflects the red component light toward the liquid crystal panel30R.

Here, the mirrors21,23, and24constitute a color separator which separates light emitted from the light source10into red component light, green component light, blue component light, and yellow component light.

The lighting unit120includes a plurality of lenses (lenses41to43, and lenses81to87). The lens41is a condenser lens which substantially parallelizes the blue component light reflected by the mirror22so that the liquid crystal panel30B is illuminated with the blue component light. The lens42is a condenser lens which substantially parallelizes the green component light reflected by the mirror23so that the liquid crystal panel30G is illuminated with the green component light. The lens43is a condenser lens which substantially parallelizes the red component light that passes through the mirror23so that the liquid crystal panel30R is illuminated with the red component light. Similarly, the lens43is a condenser lens which substantially parallelizes the yellow component light that passes through the mirror23so that the liquid crystal panel30Ye is illuminated with the yellow component light.

The lenses81to83are relay lenses with which the red component light substantially parallelized by the lens43substantially forms an image on the liquid crystal panel30R. The lenses81,84, and85are relay lenses with which the yellow component light substantially parallelized by the lens43substantially forms an image on the liquid crystal panel30Ye. The lenses86,87, and83are relay lenses with which the yellow component light substantially forms an image on the liquid crystal panel30R while controlling expansion of the yellow component light emitted from the liquid crystal panel30Ye.

The lighting unit120includes a wave plate50which rotates a polarization direction of the yellow component light by 90°. Specifically, the wave plate50rotates the polarization direction of yellow component light which is aligned with that of red component light by 90 degrees, and emits the yellow component light toward the liquid crystal panel30Ye.

Here, when the polarization direction of the yellow component light emitted from the liquid crystal panel30Ye is different from that of the red component light entering the liquid crystal panel30R, the yellow component light is blocked by a polarizing plate disposed on the entering side of the liquid crystal panel30R.

Accordingly, the matter whether to apply a voltage to the liquid crystal panel30Ye is controlled in accordance with a relationship between an application state of the voltage and a rotation of polarization light. Described below are a liquid crystal panel of a first type and a liquid crystal panel of a second type, as examples. The liquid crystal panel of first type rotates a polarization direction in a state in which the voltage is not applied, and does not rotate the polarization direction in a state where the voltage is applied. The liquid crystal panel of second type does not rotate the polarization direction in a state where the voltage is not applied, and rotates the polarization direction in a state where the voltage is applied.

(1) Case Where the Liquid Crystal Panel30Ye is of First Type

(1-1) Case Where the Wave Plate50is not Disposed

When turning off the yellow component light, the voltage is not applied to the liquid crystal panel30Ye. Here, since the liquid crystal panel30Ye rotates the polarization direction of the yellow component light, the polarization direction of the yellow component light is different from that of the red component light. Thus, the yellow component light is blocked by the polarizing plate disposed on the light entering side of the liquid crystal panel30R.

When turning on the yellow component light, the voltage is applied to the liquid crystal panel30Ye. Here, since the liquid crystal panel30Ye does not rotate the polarization direction of the yellow component light, the polarization direction of the yellow component light is the same as that of the red component light.

(1-2) Case Where the Wave Plate50is Disposed

When turning off the yellow component light, the voltage is applied to the liquid crystal panel30Ye. Here, the wave plate50rotates the polarization direction of the yellow component light. Thereafter, since the liquid crystal panel30Ye does not rotate the polarization direction of the yellow component light, the polarization direction of the yellow component light is different from that of the red component light. Thus, the yellow component light is blocked by the polarizing plate disposed on the light entering side of the liquid crystal panel30R.

When turning on the yellow component light, the voltage is not applied to the liquid crystal panel30Ye. Here, the wave plate50rotates the polarization direction of the yellow component light. Thereafter, since the liquid crystal panel30Ye further rotates the polarization direction of the yellow component light, the polarization direction of the yellow component light is the same as that of the red component light.

(2) Case Where the Liquid Crystal Panel30Ye is of Second Type.

(2-1) Case Where the Wave Plate50is not Disposed.

When turning off the yellow component light, the voltage is applied to the liquid crystal panel30Ye. Here, since the liquid crystal panel30Ye rotates the polarization direction of the yellow component light, the polarization direction of the yellow component light is different from that of the red component light. Thus, the yellow component light is blocked by the polarizing plate disposed on the light entering side of the liquid crystal panel30R.

When turning on the yellow component light, the voltage is not applied to the liquid crystal panel30Ye. Here, since the liquid crystal panel30Ye does not rotate the polarization direction of the yellow component light, the polarization direction of the yellow component light is the same as that of the red component light.

(2-2) Case Where the Wave Plate50is Disposed.

When turning off the yellow component light, the voltage is not applied to the liquid crystal panel30Ye. Here, the wave plate50rotates the polarization direction of the yellow component light. Thereafter, since the liquid crystal panel30Ye does not rotate the polarization direction of the yellow component light, the polarization direction of the yellow component light is different from that of the red component light. Thus, the yellow component light is blocked by the polarizing plate disposed on the light entering side of the liquid crystal panel30R.

When turning on the yellow component light, the voltage is applied to the liquid crystal panel30Ye. Here, the wave plate50rotates the polarization direction of the yellow component light. Thereafter, since the liquid crystal panel30Ye further rotates the polarization direction of the yellow component light, the polarization direction of the yellow component light becomes the same as that of the red component light.

Here, Table 1 represents a relationship between an application state of the voltage and the rotation of the polarization direction as described above.

(Function of the Projection Image Display Apparatus)

A function of the projection image display apparatus of the first embodiment is described below with reference to the drawings.FIG. 4is a block diagram showing the function of the projection image display apparatus100(a controlling unit130) of the first embodiment.

As shown inFIG. 4, the controlling unit130includes an input signal receiver131, a Ye substitution component calculator132, a parameter identifying unit133, a Ye component adjuster134, and an output unit135.

The input signal receiver131acquires a red input signal Rin, a green input signal Gin, and a blue input signal Bin. The input signal receiver131inputs the red input signal Rin, the green input signal Gin, and the blue input signal Bininto the parameter identifying unit133. The input signal receiver131inputs the red input signal Rinand the green input signal Gininto the Ye substitution component calculator132.

Before inputting it into the input signal receiver131, a reverse gamma correction is made to each of the red input signal Rin, the green input signal Gin, and the blue input signal Bin.

The Ye substitution component calculator132calculates a Ye substitution signal W corresponding to a component (Ye substitution component) of yellow component light which is substitutable for red component light and green component light.

Here, yellow component light having an amount of light which is the same as those of the red component light and the green component light is substitutable for the red component light and the green component light. Therefore, Ye substitution signal W having the same signal intensities as those of the red input signal Rinand the green input signal Ginis substitutable for the red input signal Rinand the green input signal Gin.

Accordingly, the Ye substitution component calculator132calculates a Ye substitution signal W using the following formula (1) based on the red input signal Rinand the green input signal Gin.

Incidentally, min (Rin, Gin) represents an input signal having a lower signal intensity between the red input signal Rinand the green input signal Gin.

The Ye substitution component calculator132inputs the red input signal Rin, the green input signal Gin, and the Ye substitution signal W into the Ye component adjuster134.

The parameter identifying unit133calculates saturation and luminance of an image (red R, green G, blue B, and yellow Ye) which is reproduced from the red input signal Rin, the green input signal Gin, and the blue input signal Bin. Subsequently, referring toFIGS. 5A to 5C, the parameter identifying unit133identifies parameters (a color reproduction parameter α, a luminance parameter β1, a luminance parameter β2), and inputs the identified parameters into the Ye component adjuster134.

More specifically, as shown inFIG. 5A, the color reproduction parameter a remains constant until the saturation of an image (yellow Ye in particular) reaches Th1. Meanwhile, the color reproduction parameter α is set so that after the saturation of the image exceeds Th1, the color reproduction parameter α increases along with an increase in saturation of the image. That is, the color reproduction parameter α is set so that when a distance between the saturation of an image and a white point is larger than a certain distance, an amount of the yellow component light increases as the saturation of the image moves away from the white point. Thus, yellow Ye in a range which could not be reproduced by the red component light, the green component light, and the blue component light is reproduced by the yellow component light, and the color reproducibility of the image is improved.

It should be noted that the white point is a point at which respective component lights are combined when reproducing white color.

As shown inFIG. 5B, the luminance parameter β1is set so that until the saturation of an image (blue B in particular) reaches Th2, the luminance parameter β1decreases along with increasing in saturation of the image. Meanwhile, the luminance parameter β1remains constant when the saturation of the image exceeds Th2. That is, the luminance parameter β1is set so that when a distance between the saturation of an image and a white point being is set to be within a certain distance, an amount of the yellow component light decreases as the saturation of the image moves away from the white point.

Based on the red input signal Rin, the green input signal Gin, and the Ye substitution signal W, the Ye component adjuster134calculates a red adjustment signal R′, a green adjustment signal G′, and a yellow adjustment signal Ye′.

In this embodiment, when calculating the red adjustment signal R′, the green adjustment signal G′, and the yellow adjustment signal Ye′, the Ye component adjuster134uses the color reproduction parameter α and the luminance parameter β1. Specifically, the Ye component adjuster134calculates the red adjustment signal R′, the green adjustment signal G′, and the yellow adjustment signal Ye′ using Formula (2) to Formula (4) shown below.

Thus, based on the red input signal Rinand the green input signal Gin, the Ye component adjuster134calculates a superimposition amount of the yellow component light (Ye substitution signal W). Based on the superimposition amount of the yellow component light (Ye substitution signal W), the Ye component adjuster134controls reduction amounts of the red input signal Rinand the green input signal Gin.

The output unit135outputs a red output signal Rout, a green output signal Gout, a blue output signal Bout, and a yellow output signal Yeoutto the respective liquid crystal panels30. More specifically, the output unit135outputs the red adjustment signal R′ to the liquid crystal panel30R as the red output signal Rout. Similarly, the output unit135outputs the green adjustment signal G′ and the yellow adjustment signal Ye′ to the liquid crystal panel30G and the liquid crystal panel30Ye as the green output signal Goutand the yellow output signal Yeout. Meanwhile, the output unit135outputs the blue input signal Bindirectly to the liquid crystal panel30B as the blue output signal Bout.

Before being inputted into the respective liquid crystal panels30, a gamma correction is made to each of the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeout.

(Operation of the Projection Image Display Apparatus)

Operation of the projection image display apparatus of the first embodiment is described below with reference to the drawings.FIG. 6is a flowchart showing operation of the projection image display apparatus100thereof.

As shown inFIG. 6, in Step10, the projection image display apparatus100receives the red input signal Rin, the green input signal Gin, and the blue input signal Bin.

In Step20, the projection image display apparatus100calculates the Ye substitution signal W based on the red input signal Rinand the green input signal Gin. More specifically, the projection image display apparatus100calculates the Ye substitution signal W using Formula (1) shown below.

Incidentally, min (Rin, Gin) represents an input signal having a lower signal intensity among the red input signal Rinand the green input signal Gin.

In Step40, based on the Ye substitution signal W, the projection image display apparatus100calculates the red adjustment signal R′, the green adjustment signal G′, and the yellow adjustment signal Ye′. Specifically, the projection image display apparatus100calculates the respective adjustment signals using Formula (2) to Formula (4) shown below.

In Step50, the projection image display apparatus100outputs the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeout. More specifically, the projection image display apparatus100outputs the red adjustment signal R′ to the liquid crystal panel30R as the red output signal Rout. Similarly, the projection image display device100outputs the green adjustment signal G′ and the yellow adjustment signal Ye′ to the liquid crystal panel30G and the liquid crystal panel30Ye as the green output signal Goutand the yellow output signal Yeout. Meanwhile, the projection image display apparatus100outputs the blue input signal Bindirectly to the liquid crystal panel30B as the blue output signal Bout.

In the first embodiment, colors (red and green) corresponding to the specific image signals (the red image signal and the green image signal) each have a hue adjacent to a hue corresponding to the fourth color component light (yellow component light). The controlling unit130controls a superimposition amount (Ye substitution signal W) of the yellow component light based on the red image signal and the green image signal. The controlling unit130controls reduction amounts of the red image signal and the green image signal based on the superimposition amount (Ye substitution signal W) of the yellow component light.

Therefore, while intending to improve the luminance of an image by using the yellow component light, deterioration of color reproducibility of the image caused by the use of yellow component light can be controlled.

The controlling unit130generates the yellow output signal Yeoutusing the luminance parameter β1determined so that the amount of the yellow component light decreases along with increase in saturation of an image. Therefore, when the saturation of an image (blue B in particular) is high, the luminance of an image in the vicinity of the white point can be improved, while deterioration of color purity caused by the use of yellow component light is controlled.

A second embodiment is described below with reference to drawings. Differences between the first embodiment described below and the second embodiment are mainly described below.

Specifically, in the above described first embodiment, the projection image display apparatus100outputs the blue input signal Bindirectly to the liquid crystal panel30B as the blue output signal Bout. In contrast, in the second embodiment, the visibilities of red component light, green component light, blue component light, and yellow component light are taken into consideration, and the projection image display apparatus100adjusts the red output signal Rout, a green output signal Gout, a blue output signal Bout, and a yellow output signal Yeout.

(Functions of the Projection Image Display Apparatus)

Functions of the projection image display device100of the second embodiment are described below by referring to drawings.FIG. 7is a block diagram showing the functions of the projection image display apparatus100(a controlling unit130) of the second embodiment. Incidentally, it should be noted that inFIG. 7, parts which are the same as those shown inFIG. 4are given the same reference numerals.

As shown inFIG. 7, the controlling unit130includes a common component extraction unit136and a visibility adjuster137in addition to the configuration shown inFIG. 4.

The common component extraction unit136extracts a common signal intensity component W2common to the red input signal Rin, the green input signal Gin, and the blue input signal Bin. Specifically, the common component extraction unit136calculates the common signal intensity component W2using Formula (5) shown below.

Incidentally, min (Rin, Gin, Bin) represents an input signal having low signal intensity among the red input signal Rin, the green input signal Gin, and the blue input signal Bin. In the second embodiment, it should be noted that the signal intensity of the blue input signal Binis lower than those of the red input signal Rinand the green input signal Gin.

Subsequently, the common component extraction unit136calculates a red intermediate signal R1and a green intermediate signal G1by excluding the common signal intensity component W2from the red input signal Rinand the green input signal Gin. More specifically, the common component extraction unit136calculates the red intermediate signal R1and the green intermediate signal G1using Formula (6) to Formula (8) shown below.

In the second embodiment, B is equal to 0 since the signal intensity of the blue input signal Binis lower than those of the red input signal Rinand the green input signal Gin.

Based on the common signal intensity component W2, the visibility adjuster137calculates a red intermediate signal R3, a green intermediate signal G3, a blue intermediate signal B3, and a yellow intermediate signal Ye3by taking into account the visibilities of red component light, green component light, blue component light, and yellow component light. Here, the visibility adjuster137calculates the red intermediate signal R3, the green intermediate signal G3, the blue intermediate signal B3, and the yellow intermediate signal Ye3using ratios (e.g., red ratio rR=187/255, green ratio rG=255/255, blue ratio rB=128/255, and yellow ratio rYe=255/255) for which the visibilities of the red component light, the green component light, the blue component light, and the yellow component light are considered. Specifically, the visibility adjuster137calculates the red intermediate signal R3, the green intermediate signal G3, the blue intermediate signal B3, and the yellow intermediate signal Ye3using Formula (9) to Formula (12) shown below.

The above-described Ye substitution component calculator132calculates the Ye substitution signal W corresponding to a component (Ye substitution component) of the yellow component light which is substitutable for the red component light and the green component light. More specifically, based on the red intermediate signal R1and the green intermediate signal G1, the Ye substitution component calculator132calculates the Ye substitution signal W using Formula (13) shown below.

Incidentally, min (R1, G1) represents an input signal having a lower signal intensity between the red intermediate signal R1and the green intermediate signal G1.

Based on the red intermediate signal R1, the green intermediate signal G1, and the Ye substitution signal W, the above-described Ye component adjuster134calculates a red adjustment signal R2, a green adjustment signal G2, and a yellow adjustment signal Ye2. Here, in the calculation of the red adjustment signal R2, the green adjustment signal G2, and the yellow adjustment signal Ye2, the Ye component adjuster134uses the color reproduction parameter α and the luminance parameter β1. More specifically, the Ye component adjuster134calculates the red adjustment signal R2, the green adjustment signal G2, and the yellow adjustment signal Ye2using Formula (14) to Formula (16) shown below.

The output unit135outputs the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeoutto the respective liquid crystal panels30. Specifically, the output unit135outputs a signal which is the sum of the red adjustment signal R2and the red intermediate signal R3, to the liquid crystal panel30R as the red output signal Rout. Similarly, the output unit135outputs a signal which is the sum of the green adjustment signal G2and the green intermediate signal G3, to the liquid crystal panel30G as the green output signal Gout, and also outputs a signal which is the sum of the yellow adjustment signal Ye2and the yellow intermediate signal Ye3, to the liquid crystal panel30Ye as the yellow output signal Yeout. Meanwhile, the output unit135outputs the blue intermediate signal B3directly to the liquid crystal panel30B as the blue output signal Bout.

(Operation of the Projection Image Display Apparatus)

Operation of the projection image display apparatus of the second embodiment is described below with reference to a drawing.FIG. 8is a flowchart showing operation of the projection image display apparatus100of the second embodiment.

As shown inFIG. 8, in Step10A, the projection image display apparatus100receives the red input signal Rin, the green input signal Gin, and the blue input signal Bin.

In Step12A, the projection image display apparatus100extracts the common signal intensity component W2common to the red input signal Rin, the green input signal Gin, and the blue input signal Bin. Specifically, the projection image display apparatus100calculates the common signal intensity component W2using Formula (5) shown below.

Incidentally, min (Rin, Gin, Bin) represents an input signal having low signal intensity among the red input signal Rin, the green input signal Gin, and the blue input signal Bin.

In Step14A, based on the common signal intensity component W2, the projection image display apparatus100calculates a red intermediate signal R3, a green intermediate signal G3, a blue intermediate signal B3, and a yellow intermediate signal Ye3by taking into account the visibilities of the red component light, the green component light, the blue component light, and the yellow component light. Specifically, the projection image display apparatus100calculates the red intermediate signal R3, the green intermediate signal G3, the blue intermediate signal B3, and the yellow intermediate signal Ye3using Formula (9) to Formula (12) shown below.

Incidentally, the red ratio rR, the green ratio rG, the blue ratio rB, and the yellow ratio rYeare ratios for which the visibilities of the red component light, the green component light, the blue component light, and the yellow component light are considered.

In Step20A, the projection image display apparatus100calculates the red intermediate signal R1and the green intermediate signal G1using Formula (6) to Formula (8) shown below.

Subsequently, based on the red intermediate signal R1and the green intermediate signal G1, the projection image display apparatus100calculates the Ye substitution signal W using Formula (13) shown below.

Incidentally, min (R1, G1) represents an input signal having a lower signal intensity between the red intermediate signal R1and the green intermediate signal G1.

In Step30A, the projection image display apparatus100identifies the color reproduction parameter α and the luminance parameter β1based on the saturation of an image and the luminance thereof. Specifically, the projection image display apparatus100identifies the luminance parameter β1with reference toFIGS. 5described above.

In Step40A, based on the red intermediate signal R1, the green intermediate signal G1, and the Ye substitution signal W, the projection image display apparatus100calculates a red adjustment signal R2, a green adjustment signal G2, and a yellow adjustment signal Ye2. More specifically, the projection image display apparatus100calculates the red adjustment signal R2, the green adjustment signal G2, and the yellow adjustment signal Ye2using Formula (14) to Formula (16) shown below.

In Step50A, the projection image display apparatus100outputs the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeout. Specifically, the projection image display apparatus100outputs a signal which is the sum of the red adjustment signal R2and the red intermediate signal R3, to the liquid crystal panel30R as the red output signal Rout. Similarly, the projection image display apparatus100outputs a signal which is the sum of the green adjustment signal G2and the green intermediate signal G3, to the liquid crystal panel30G as the green output signal Gout, and also outputs a signal which is the sum of the yellow adjustment signal Ye2and the yellow intermediate signal Ye3, to the liquid crystal panel30Ye as the yellow output signal Yeout. Meanwhile, the projection image display apparatus100outputs the blue intermediate signal B3directly to the liquid crystal panel30B as the blue output signal Bout.

(Calculation Examples of Output Signals)

Referring toFIGS. 9 to 14, calculation examples of output signals of the second embodiment are described below. Specifically, description is given to the case where the red output signal Rout, the green output signal Gout, the blue output signal Boutand the yellow output signal Yeoutare calculated, when the red input signal Rin=“200”; the green input signal Gin=“170”; and the blue input signal Bin=“100,” as shown inFIG. 9.

As shown inFIG. 10, the projection image display apparatus100calculates the common signal intensity component W2using Formula (5) shown below.

As shown inFIG. 11, the projection image display apparatus100calculates the red intermediate signal R1and the green intermediate signal G1using Formula 6) to Formula 8) shown below.

As shown inFIG. 12, the projection image display apparatus100calculates the red intermediate signal R3, the green intermediate signal G3, the blue intermediate signal B3, and the yellow intermediate signal Ye3using Formula (9) to Formula (12) shown below.

Incidentally, it should be noted thatFIG. 12exemplifies the case where the red ratio rR=187/255, the green ratio rG=255/255, the blue ratio rB=128/255, and the yellow ratio rYe=255/255.

As shown inFIG. 13, based on the red intermediate signal R1and the green intermediate signal G1, the projection image display apparatus100calculates the Ye substitution signal W using Formula (13) shown below.

Subsequently, the projection image display apparatus100calculates the red adjustment signal R2, the green adjustment signal G2, and the yellow adjustment signal Ye2using Formula (14) to Formula (16) shown below.

Incidentally, it should be noted thatFIG. 13exemplifies the case where “1” is identified as the color reproduction parameter α and “0” is identified as the luminance parameter β1.

As shown inFIG. 14, the projection image display apparatus100outputs a signal which is the sum of the red adjustment signal R2and the red intermediate signal R3, to the liquid crystal panel30R as the red output signal Rout. Similarly, the projection image display apparatus100outputs a signal which is the sum of the green adjustment signal G2and the green intermediate signal G3, to the liquid crystal panel30G as the green output signal Gout, and also outputs a signal which is the sum of the yellow adjustment signal Ye2and the yellow intermediate signal Ye3, to the liquid crystal panel30Ye as the yellow output signal Yeout. Meanwhile, the projection image display apparatus100outputs the blue intermediate signal R3directly to the liquid crystal panel30B as the blue output signal Bout.

In accordance with the projection image display apparatus100of the second embodiment, the controlling unit130extracts the common signal intensity component W2common to the red input signal Rin, the green input signal Gin, and the blue input signal Bin. Thereafter, the controlling unit130calculates the red intermediate signal R3, the green intermediate signal G3, the blue intermediate signal B3, and the yellow intermediate signal Ye3by multiplying the common signal intensity component W2by each of the ratios for which the visibilities have been considered.

Further, the controlling unit130calculates the red adjustment signal R2, the green adjustment signal G2, and the yellow adjustment signal Ye2, based on the red intermediate signal R1and the green intermediate signal G1which is obtained by excluding the common signal intensity component W2from the red input signal Rinand the green input signal Gin.

Further, the red output signal Routis a signal which is the sum of the red adjustment signal R2and the red intermediate signal R3, the green output signal Goutis a signal which is the sum of the green adjustment signal G2and the green intermediate signal G3, and the yellow output signal Yeoutis a signal which is the sum of the yellow adjustment signal Ye2and the yellow intermediate signal Ye3.

Accordingly, by excluding the common signal intensity component W2from the red input signal Rinand the green input signal Gin, the deterioration of color reproducibility of an image caused by the use of the yellow component light can be controlled.

A third embodiment is described below with reference to drawings. Differences between the first embodiment and the third embodiment are mainly described below.

More specifically, in the above-described first embodiment, a superimposition amount of the yellow component light (Ye substitution signal W) is determined from an input signal having a lower intensity between the red input signal Rinand the green input signal Gin.

In contrast, in the third embodiment, a superimposition amount of yellow component light (Ye substitution signal W) is determined from a mean value of luminance of respective pixels included in a target region and a mean value of saturation thereof.

(Function of the Projection Image Display Apparatus)

A function of a projection image display apparatus100of the third embodiment is described below with reference to the drawings.FIG. 15is a view for explaining the functions of the projection image display apparatus100(controlling unit130) of the third embodiment.

The projection image display apparatus100(controlling unit130) calculates the superimposition amount of the yellow component light (Ye substitution signal W) for each target region determined according to the resolution of the liquid crystal panel30Ye.

As shown inFIG. 15, the controlling unit130creates a histogram of pixels included in the target region corresponding to the luminance of the each of the pixels. Subsequently, the controlling unit130calculates a luminance average value (L(ave)) of the pixels included in the target region.

The controlling unit130calculates the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeoutusing Formula (21) to Formula (24).

However, when the luminance average value (L(ave)) exceeds min (Rin, Gin), min (Rin, Gin) may be used instead of the luminance average value (L(ave)).

Incidentally, it should be noted that the yellow output signal Yeoutis the same as the Ye substitution signal W in the third embodiment.

[Variation 1 of the Third Embodiment]

A variation 1 of the third embodiment is described below with reference to the drawing. Specifically, in the variation 1 of the third embodiment, a saturation average value (C(ave)) is used instead of the luminance average value (L(ave)).

(Function of the Projection Image Display Apparatus)

A function of the projection image display apparatus of the variation 1 of the third embodiment is described below with reference to the drawing.FIG. 16is a view for explaining the function of the projection image display apparatus100(controlling unit130) of the variation 1 of the third embodiment.

As shown inFIG. 16, the controlling unit130creates a histogram, of the pixels included in a target region corresponding to the saturation of each of the pixels. Subsequently, the controlling unit130calculates the saturation average value (C(ave)) of the pixels included in the target region.

The controlling unit130calculates the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeoutusing Formula (25) to Formula (28).

However, when the saturation average value (C(ave)) exceeds min (Rin, Gin), min (Rin, Gin) may be used instead of the saturation average value (C(ave)).

[Variation 2 of the Third Embodiment]

A variation 2 of the third embodiment is described below with reference to the drawing. Specifically, in the variation 2 of the third embodiment, luminance average values (L1(ave), L2(ave)) calculated for each hue is used instead of the luminance average value (L(ave)).

(Function of the Projection Image Display Apparatus)

A function of the projection image display apparatus of the variation 2 of the third embodiment is described below with reference to the drawings.FIGS. 17A and 17Bare views for explaining the function of the projection image display apparatus100(controlling unit130) of the variation 2 of the third embodiment.

As shown inFIGS. 17A and 17B, the controlling unit130creates a histogram of the pixels included in a target region corresponding to the luminance of each of the pixels, for the each of hues (θ1, θ2). Subsequently, the controlling unit130calculates luminance average value (L1(ave), L2(ave)) for each of the hues (θ1, θ2) of the pixels included in the target region.

Here, the hue (θ1) represents a hue (e.g., red) which is largely effected by the yellow component light when the color is reproduced in the target region. The hue (θ2) represents a hue (e.g., cyan) which is less effected by yellow component when the color is reproduced in the target region.

The controlling unit130calculates the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeoutusing Formula (29) to Formula (32).

However, when “p×L1(ave)+q×L2(ave)” exceeds min (Rin, Gin) min (Rin, Gin) may be used instead of “p×L1(ave)+q×L2(ave).” Further, the coefficients p and q may be set so that “p×L1(ave)+q×L2(ave)” does not exceed min (R1, G1).

Incidentally, the coefficients p and q are adjustment coefficients set for each of the hues and have a relationship of “p<q.” Thus, checked is an increase of a superimposition amount of the yellow component light calculated based on the hue (θ1) which largely influences the color reproducibility of the target region.

[Variation 3 of the Third Embodiment]

A variation 3 of the third embodiment is described below with reference to the drawings. Specifically, in the variation 3 of the third embodiment, the saturation average value (C(ave)) is used in addition to the luminance average (L(ave)).

(Function of the Projection Image Display Apparatus)

A function of the projection image display apparatus of the variation 3 of the third embodiment is described below with reference to the drawings. FIGS.18A and18B are views for explaining the function of the projection image display apparatus100(controlling unit130) of the variation 3 of the third embodiment.

As shown inFIGS. 18A and 18B, the controlling unit130creates histograms of the pixels included in a target region corresponding to the luminance and saturation of each of the pixels, respectively. Subsequently, the controlling unit130calculates the luminance average (L(ave)) and the saturation average value (C(ave)) of the pixels included in the target region.

The controlling unit130calculates the red output signal Rout, the green output signal Gout, the blue output signal Bout, and the yellow output signal Yeoutusing Formula (33) to Formula (36).

However, when “r×L(ave)+s×C(ave)” exceeds min (Rin, Gin), min (Rin, Gin) may be used instead of “r×L(ave)+s×C(ave).” Further, the coefficients r and s may be set so that “r×L(ave)+s×C(ave)” does not exceed min (Rin, Gin).

In addition, different values are set for the coefficients r and s when greater importance is placed on luminance and when greater importance is placed on color reproducibility. Specifically, when greater importance is placed on luminance, the coefficients r and s have the relationship of “r>s.” Meanwhile, in the case where greater importance is placed on color reproducibility, the coefficients r and s have the relationship of “r<s.”

The present invention has been described according to the above-mentioned embodiments. But it should be understood that the description and the drawings constituting a part of this disclosure dose not limit the present invention. It is apparent to the skilled person that various alternatives, modifications, and the practices can be achieved based on this disclosure.

For example, the projection image display apparatus100may use cyan component light Cy as the fourth component light. In this case, a cyan output signal Cyoutis generated based on a green input signal Ginand a blue input signal Binwhich include colors (green G and blue B) having hues adjacent to a hue corresponding to the cyan component light Cy, among a red input signal Rin, the green input signal Gin, and the blue input signal Bin.

Similarly, the projection image display apparatus100may use magenta component light M as the fourth component light. In this case, a magenta output signal Moutis generated based on a red input signal Rinand a blue input signal Binwhich include colors (red R and blue B) having hues adjacent to a hue corresponding to the magenta component light M, among the red input signal Rin, a green input signal Gin, and the blue input signal Bin.

In the above-described embodiments, the yellow output signal Yeoutis generated using the color reproduction parameter α and the luminance parameter β1, but it is not limited to using these parameters. Specifically, the yellow output signal Yeoutmay be generated using only the color reproduction parameter α or using only the luminance parameter β1. Alternatively, the yellow output signal Yeoutmay be generated using the luminance parameter β2. Alternatively, the yellow output signal Yeoutmay be generated using the luminance parameter β1and the luminance parameter β2. In addition, the color reproduction parameter α, the luminance parameter β1, and the luminance parameter β2may be properly combined to generate the yellow output signal Yeout.

In the above-described embodiments, the controlling unit130is provided in the projection image display apparatus100, but it is not limited to this. Specifically, the controlling unit130may be independently provided.

In the above-described embodiments, the image display apparatus has been exemplified in the projection image display apparatus100, but it is not limited to this. The image display apparatus may be any apparatus which is capable of displaying images.

In the third embodiment described above, the superimposition amount of the yellow component light (yellow output signal Yeout) is calculated by using the luminance average value (L(ave)) and the saturation average value (C(ave)), but it is not limited to this. Specifically, the superimposition amount of yellow component light (yellow output signal Yeout) may be calculated by using representative values of luminance and saturation such as a minimum value (L(min)) of luminance, a maximum value (L(max)) of luminance, a minimum value (C(min)) of saturation, and a maximum value (C(max)) of saturation.

In the above-described embodiments, the relationship that is represented by “Ye=R+G” is assumed to hold, but it is not limited to this. Even when relationships such as “Ye=R+2G” and “Ye=2R+G” hold, it is possible to calculate a superimposition amount of yellow component light (yellow output signal Yeout) by adjusting the respective formulas described above.

In the above-described embodiments, the yellow component light emitting from the liquid crystal panel30Ye is superimposed on the red component light, but it is not limited to this. Yellow component light emitting from the liquid crystal panel30Ye may be superimposed on component light of different color (green component light or blue component light).

In the above-described embodiments, the yellow component light is separated from the light emitted from the light source10, but it is not limited to this. Specifically, the projection image display apparatus100may be provided with a solid light source (a laser diode (LD) or a light emitting diode (LED)) which emits yellow component light.

In the above-described embodiments, the superimposition amount of the yellow component light is controlled by the modulation amount of the liquid crystal panel30Ye, but it is not limited to this. Specifically, the superimposition amount of yellow component light may be controlled by an iris mechanism which is provided on a light path of the yellow component light.

In the above-described embodiments, the light imager has been exemplified in the liquid crystal panel, but it is not limited to this. Specifically, the light modulator may be a Liquid Crystal on Silicon (LCOS) or a Digital Micromirror Device (DMD).