US20050206851A1 - Projection type image display device - Google Patents
Projection type image display device Download PDFInfo
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- US20050206851A1 US20050206851A1 US11/126,371 US12637105A US2005206851A1 US 20050206851 A1 US20050206851 A1 US 20050206851A1 US 12637105 A US12637105 A US 12637105A US 2005206851 A1 US2005206851 A1 US 2005206851A1
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- 230000002194 synthesizing effect Effects 0.000 claims abstract description 35
- 230000003287 optical effect Effects 0.000 claims abstract description 34
- 238000012545 processing Methods 0.000 claims description 34
- 239000012528 membrane Substances 0.000 abstract description 31
- 238000012937 correction Methods 0.000 description 50
- 239000004973 liquid crystal related substance Substances 0.000 description 37
- 238000000034 method Methods 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 238000003786 synthesis reaction Methods 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 2
- 239000000470 constituent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000005357 flat glass Substances 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3179—Video signal processing therefor
- H04N9/3182—Colour adjustment, e.g. white balance, shading or gamut
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/64—Circuits for processing colour signals
- H04N9/68—Circuits for processing colour signals for controlling the amplitude of colour signals, e.g. automatic chroma control circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/64—Circuits for processing colour signals
- H04N9/68—Circuits for processing colour signals for controlling the amplitude of colour signals, e.g. automatic chroma control circuits
- H04N9/69—Circuits for processing colour signals for controlling the amplitude of colour signals, e.g. automatic chroma control circuits for modifying the colour signals by gamma correction
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0233—Improving the luminance or brightness uniformity across the screen
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0242—Compensation of deficiencies in the appearance of colours
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0285—Improving the quality of display appearance using tables for spatial correction of display data
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor
- H04N5/7416—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
- H04N5/7441—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal the modulator being an array of liquid crystal cells
- H04N2005/745—Control circuits therefor
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/20—Circuitry for controlling amplitude response
- H04N5/202—Gamma control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
- H04N5/57—Control of contrast or brightness
Definitions
- the present invention relates to a projection type image display device, such as a liquid crystal projector, including a color synthesizing optical system that uses a dichroic membrane.
- a projection type image display device such as a liquid crystal projector, including a color synthesizing optical system.
- FIG. 8 white light emitted from a light source 201 is transformed into substantially parallel rays of light by a parabolic mirror 2 , a reflecting mirror (not shown), and a lens group (not shown).
- the substantially parallel rays of light are subjected to color separation by dichroic mirrors 203 and 204 , highly reflecting mirrors 205 , 206 and 207 , and a lens group (not shown), and are condensed to liquid crystal panels 208 , 209 and 210 disposed for each color.
- the each color light that has entered the liquid crystal panels 208 , 209 and 210 is then modulated by the liquid crystal panels 208 , 209 and 210 displaying an image, thereby generating spatially modulated light according to the display image.
- Each color modulated light is subjected to color synthesis by a color synthesizing dichroic prism 211 , and is enlarged and projected onto a screen 213 through a projection lens group 212 .
- a group of positive refractive lenses 214 , 215 and 216 are disposed between each liquid crystal panel 208 , 209 and 210 and the dichroic prism 211 in order to reduce the optical system in size. Therefore, each color modulated light in the form of substantially parallel light that has passed through each liquid crystal panel 208 , 209 and 210 is effected by the condensing (converging) action of the positive refractive lenses 214 , 215 and 216 , and is made non-parallel. This non-parallel light strikes the color synthesizing dichroic prism 211 .
- the incidence angle of the light upon the dichroic membrane has a difference between the right and the left of the image, and thereby a difference arises in the spectral/transmitted cutoff wavelength in the dichroic membrane.
- nonuniformity color unevenness or brightness irregularity
- a countermeasure has been made to form a so-called gradient membrane as the dichroic membrane in which thickness or a refractive index slantingly varies in a specific direction.
- the projection type image display device in a projection type image display device that includes a plurality of image display elements for performing modulation of light rays in accordance with an image signal, a color synthesizing optical element for synthesizing light rays different from each other in the wavelength range that have been modulated by these image display elements by use of a dichroic membrane, and a lens group that has positive refractive power as a whole and that is disposed between the image display elements and the color synthesizing optical element, and a projection optical system for projecting an image synthesized by the color synthesizing optical element
- the projection type image display device further includes a storage circuit for storing data to correct brightness irregularity (the nonuniformity of a brightness level) of a projected image and a brightness irregularity correcting circuit for correcting brightness irregularity of a projected image on the basis of the data stored in the storage circuit.
- the brightness irregularity correcting circuit merely needs to correct an input signal to the image display element in each pixel of the image display elements or in each pixel area (i.e., pixel group) thereof.
- the brightness irregularity correcting circuit merely needs to correct an input signal to the image display element in each pixel of the image display elements or in each pixel area (i.e., pixel group) thereof.
- FIG. 1 shows a structure of a liquid crystal projector, which is a first embodiment of the present invention.
- FIG. 2 shows a structure of a signal-processing circuit in the liquid crystal projector.
- FIG. 3 ( a ) and FIG. 3 ( b ) explain the operation of a color unevenness correction circuit in the signal-processing circuit.
- FIG. 4 shows a structure of a signal-processing circuit in a liquid crystal projector, which is a second embodiment of the present invention.
- FIG. 5 shows a structure of a signal-processing circuit in a liquid crystal projector, which is a third embodiment of the present invention.
- FIG. 6 explains the operation of a color unevenness correction circuit in the third embodiment.
- FIG. 7 explains an example of correction data creation in the first embodiment.
- FIG. 8 shows a structure of a conventional liquid crystal projector.
- FIG. 1 shows a structure of a liquid crystal projector (projection type image display device), which is an embodiment of the present invention.
- FIG. 1 white light emitted from a light source 1 is transformed into substantially parallel rays of light by a parabolic mirror 2 , a reflecting mirror (not shown), and a lens group (not shown).
- the substantially parallel light is subjected to color separation by dichroic mirrors 3 and 4 , highly reflecting mirrors 5 , 6 and 7 , and a lens group (not shown) so as to turn into each color of red, green and blue, and is condensed onto liquid crystal panels (image display elements) 8 , 9 and 10 disposed for each color.
- Light rays that have entered the liquid crystal panels 8 , 9 and 10 are then modulated by the liquid crystal panels 8 , 9 and 10 , respectively, that display images, thereby producing spatially modulated light in accordance with the displayed images.
- the modulated light of each color is subjected to color synthesis by a color synthesizing dichroic prism (color synthesizing optical element) 11 , and is enlarged and projected onto a screen 13 through a projection lens group 12 .
- Two dichroic membranes 11 a and 11 b that are each inclined with respect to an optical axis are disposed in the color synthesizing dichroic prism 11 without intersecting each other in the prism.
- the dichroic membrane 11 a synthesizes two kinds of color-modulated light among red modulated light, green modulated light, and blue modulated light that have mutually different wavelength ranges by its reflecting/transmitting action.
- the dichroic membrane 11 b synthesizes the two kinds of color-modulated light that have been synthesized by the dichroic membrane 11 a and the remaining color-modulated light by its reflecting/transmitting action.
- the modulated light that has thus undergone the color synthesis is emitted from an emitting surface of the prism 11 to the projection lens group 12 .
- positive refractive lens groups 14 , 15 and 16 are disposed between the liquid crystal panels 8 , 9 and 10 and the color synthesizing dichroic prism 11 , and thereby the optical system is reduced in size.
- each color-modulated light which is substantially parallel light and which has been emitted from the liquid crystal panels 8 , 9 and 10 , is transformed into non-parallel light by the condensing action (converging action) of the positive refractive lens groups 14 , 15 and 16 .
- This non-parallel light enters the dichroic films 11 a and 11 b of the color synthesizing dichroic prism 11 . Therefore, for the reason given in the description of the conventional technique, there is a fear that the nonuniformity of a brightness level (color unevenness) will occur in an image projected onto the screen 13 .
- this color unevenness can be corrected regardless of directions on the image, as described later.
- An image signal such as a video signal or VGA signal, that has been input to a decoder 17 from the outside is digitized by the decoder 17 , and is sent to a signal-processing circuit 18 .
- the signal-processing circuit 18 performs digital signal processing, such as resolution transformation or frame rate transformation, for the image signal, and performs LCD signal processing, such as gamma correction by which the VT characteristics of the liquid crystal panels 8 , 9 and 10 are corrected.
- the signal-processing circuit 18 further performs corrections necessary to correct the color unevenness in a color unevenness correction processing circuit (brightness irregularity correcting circuit) 19 for the image signal to be input to the liquid crystal panels 8 , 9 and 10 that has undergone the aforementioned processings.
- a color unevenness correction processing circuit (brightness irregularity correcting circuit) 19 for the image signal to be input to the liquid crystal panels 8 , 9 and 10 that has undergone the aforementioned processings.
- the image signal is corrected to cancel the color unevenness brightness irregularity or nonuniformity of a brightness level) by these corrections, no color unevenness occurs in the image (projection image) formed by light rays that has been modulated by the liquid crystal panels 8 , 9 and 10 and that has been synthesized by the color-synthesizing prism 11 .
- FIG. 2 shows in detail the signal-processing circuit 18 that includes the color unevenness correction circuit 19 .
- Image signals (DRi, DGi, DBi) digitized by the decoder 17 are input to the color unevenness correction circuit 19 through the digital signal processing circuit 22 for a scan converter or resolution transformation and through the LCD signal processing circuit 23 .
- a frame memory 24 in which correction data used to correct the color unevenness in horizontal and vertical directions is stored is connected to the color unevenness correction circuit 19 .
- the frame memory 24 is made up of a ROM and other elements, in which the correction data is prestored.
- the color unevenness correction circuit 19 reads out correction data, which synchronizes with the image signals ARi, AGi and ABi input from the LCD signal processing circuit 23 , from the frame memory 24 by use of a timing signal from a timing generator 21 , and corrects the image signals ARi, AGi and ABi in real time.
- FIG. 7 shows an example of a method for creation of correction data.
- image signals each having a uniform brightness level, are sequentially input to the liquid crystal panels 8 , 9 and 10 , and are displayed as images.
- brightness data in the projected image on the screen of each color will be designated as Lr (x,y), Lg (x,y) and Lb (x,y), and a maximum brightness value in the brightness data of each color will be designated as Lr_max, Lg_max and Lb_max.
- the amount of correction data may be decreased so as to reduce the size of the frame memory 24 by setting the correction data shown by the equations (1), (2) and (3) for each arbitrary pixel area for simplification.
- FIG. 3 ( a ) shows an example of a correcting operation when a uniform white (gray) color is displayed. Since image signals input to the liquid crystal panel is a uniform white (gray) color, the image signals ARi, AGi and ABi prior to corrections have no positional level difference, and have a constant level in both horizontal and vertical directions.
- the correction data is created to cancel this color unevenness according to the method shown in FIG. 7 .
- the image signal has a uniform brightness level (e.g., 255 )
- a uniform brightness level e.g., 255
- such correction data so as to enlarge the gain is set as a projected image (modulated light) on the screen 13 in a pixel or in a pixel area in which brightness becomes lower than the maximum brightness Lr_max, Lg_max and Lb_max because of the color unevenness.
- FIG. 3 ( b ) shows an example of correction data stored in the frame memory 24 .
- the after-correction signal (ARo, AGo, ABo) of each color that has passed through the color unevenness correction circuit 19 is changed into a signal having an inclination or variation as shown in FIG. 3 ( a ).
- liquid crystal panels 8 , 9 and 10 driven by use of the after-correction signal have space transmittance characteristics by which color unevenness is canceled, an image having uniform brightness is displayed on the screen 13 .
- electric signals input to the liquid crystal panels 8 , 9 and 10 are corrected to eliminate the color unevenness of a projected image caused by an optical system, and, accordingly, the aforementioned color unevenness can be corrected by a simple, inexpensive structure, regardless of whether a horizontal or vertical direction in a projection screen.
- color unevenness correction processing can be applied to the output signal from the digital signal processing circuit 30 prior to the step of being input to the LCD signal processing circuit 23 .
- amplifiers 25 , 26 and 27 of FIG. 2 are realized by multipliers 32 , 33 and 34 .
- Color unevenness correction processing may be performed at any position between the input of the digital signal processing unit 22 and input of the LCD driving unit 20 according to methods other than the methods of FIG. 2 and FIG. 4 as long as a correction circuit capable of gain control is disposed at each spatial position of a pixel or a pixel area.
- FIG. 5 shows the structure of a liquid crystal projector (projection type image display device), which is another embodiment of the present invention.
- the same reference symbols as in the above embodiment are given to the same constituent elements as in the above embodiment.
- dichroic membranes 50 A and 50 B that are provided in the color synthesizing dichroic prism 50 are each formed with a gradient membrane in which thickness or a refractive index slantingly varies in a specific direction.
- the optical system of FIG. 5 has the same structure as that of FIG. 2 , except for the color synthesizing dichroic prism 50 .
- the gradient membrane are used as dichroic membranes 50 A and 50 B, light that passes through any position of the liquid crystal panels 8 , 9 and 10 becomes equal in the incidence angle upon the dichroic membranes 50 A and 50 B in the horizontal direction that corresponds to the characteristic inclination direction of the gradient membrane, and therefore color unevenness can be prevented from occurring in the horizontal direction.
- FIG. 6 shows an example of a correcting operation when a uniform white (gray) color is displayed on the liquid crystal panels 8 , 9 and 10 .
- Color unevenness in the horizontal direction can be almost completely corrected by use of a properly formed gradient membrane.
- correction data to be stored in a frame memory or a line memory 51 is created to cancel the color unevenness in the vertical direction.
- FIG. 6 shows a case in which color unevenness correction processing is performed only in the vertical direction.
- the memory 51 can be formed with a line memory for a vertical line.
- liquid crystal panels 8 , 9 and 10 driven by use of after-correction signals have space transmittance characteristics by which color unevenness in the vertical direction is canceled, an image having uniform brightness is displayed on the screen 13 .
- the color unevenness of the projected image caused by the optical system is corrected by using the gradient membrane in the horizontal direction and by correcting the electric signals input to the liquid crystal panels 8 , 9 and 10 in the vertical direction. Therefore, the aforementioned color unevenness can be corrected by a simple, inexpensive structure.
- Color unevenness correction processing may be performed at any position between input of digital signal processing unit 22 and input of LCD driving unit 20 according to methods other than the method of FIG. 5 as long as a correction circuit capable of gain control is disposed at each spatial position of a pixel or a pixel area.
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Abstract
A projection type image display device includes a plurality of image display elements that perform modulation of light rays in accordance with an image signal, a color synthesizing optical element for synthesizing light rays having mutually different wavelength ranges that have been modulated by these image display elements by use of a dichroic membrane, lens groups having a positive refractive power as a whole that are disposed between the image display element and the color synthesizing optical element, and a projection optical system for projecting an image synthesized by the color synthesizing optical element. The projection type image display device further includes a storage circuit for storing data used to correct the brightness irregularity of a projected image, and a brightness irregularity correcting circuit for correcting brightness irregularity of a projected image on the basis of the data stored in the storage circuit.
Description
- 1. Field of the Invention
- The present invention relates to a projection type image display device, such as a liquid crystal projector, including a color synthesizing optical system that uses a dichroic membrane.
- 2. Description of the Related Art
- Conventionally, various devices have been proposed as a projection type image display device, such as a liquid crystal projector, including a color synthesizing optical system.
- A conventional projection type image display device will now be described with reference to
FIG. 8 . InFIG. 8 , white light emitted from a light source 201 is transformed into substantially parallel rays of light by aparabolic mirror 2, a reflecting mirror (not shown), and a lens group (not shown). - The substantially parallel rays of light are subjected to color separation by
dichroic mirrors mirrors liquid crystal panels liquid crystal panels liquid crystal panels - Each color modulated light is subjected to color synthesis by a color synthesizing
dichroic prism 211, and is enlarged and projected onto ascreen 213 through aprojection lens group 212. Meanwhile, a group of positiverefractive lenses liquid crystal panel dichroic prism 211 in order to reduce the optical system in size. Therefore, each color modulated light in the form of substantially parallel light that has passed through eachliquid crystal panel refractive lenses dichroic prism 211. - Therefore, disadvantageously, for the example, the incidence angle of the light upon the dichroic membrane has a difference between the right and the left of the image, and thereby a difference arises in the spectral/transmitted cutoff wavelength in the dichroic membrane. As a result, in each color light, nonuniformity (color unevenness or brightness irregularity) in the brightness level occurs in the right and the left of the screen.
- As a solution to the color unevenness, a countermeasure has been made to form a so-called gradient membrane as the dichroic membrane in which thickness or a refractive index slantingly varies in a specific direction.
- However, there is a problem in that, usually, color unevenness can be simply corrected only in one direction in the thus formed gradient membrane, so that color unevenness in each direction cannot be sufficiently corrected, and, in addition, a color synthesizing prism becomes expensive due to the formation of the gradient membrane.
- It is therefore an object of the present invention to provide a projection type image display device capable of correcting color unevenness that easily occurs when a lens group with positive refractive power is disposed between a color synthesizing optical element, such as a color synthesizing prism, and an image display element by a simple, inexpensive structure, irrespective of whether a horizontal or vertical direction in a projected image.
- In order to achieve the object, according to the present invention, in a projection type image display device that includes a plurality of image display elements for performing modulation of light rays in accordance with an image signal, a color synthesizing optical element for synthesizing light rays different from each other in the wavelength range that have been modulated by these image display elements by use of a dichroic membrane, and a lens group that has positive refractive power as a whole and that is disposed between the image display elements and the color synthesizing optical element, and a projection optical system for projecting an image synthesized by the color synthesizing optical element, the projection type image display device further includes a storage circuit for storing data to correct brightness irregularity (the nonuniformity of a brightness level) of a projected image and a brightness irregularity correcting circuit for correcting brightness irregularity of a projected image on the basis of the data stored in the storage circuit.
- Thereby, it is possible to correct the nonuniformity (color unevenness) in the brightness level that easily occurs when the lens group with positive refractive power is disposed between the color synthesizing optical element and the image display element by a simple, inexpensive structure, irrespective of whether a horizontal or vertical direction in the projected image, and is possible to project and display an image with high picture quality and with no color unevenness.
- Additionally, when a gradient membrane is used as a dichroic membrane in order to correct color unevenness in a specific direction, color unevenness in a direction that cannot be optically corrected by this gradient membrane can be electrically corrected with ease.
- More specifically, the brightness irregularity correcting circuit merely needs to correct an input signal to the image display element in each pixel of the image display elements or in each pixel area (i.e., pixel group) thereof. Other objects and structures of the present invention will become apparent from disclosure of the embodiments provided later.
-
FIG. 1 shows a structure of a liquid crystal projector, which is a first embodiment of the present invention. -
FIG. 2 shows a structure of a signal-processing circuit in the liquid crystal projector. -
FIG. 3 (a) andFIG. 3 (b) explain the operation of a color unevenness correction circuit in the signal-processing circuit. -
FIG. 4 shows a structure of a signal-processing circuit in a liquid crystal projector, which is a second embodiment of the present invention. -
FIG. 5 shows a structure of a signal-processing circuit in a liquid crystal projector, which is a third embodiment of the present invention. -
FIG. 6 explains the operation of a color unevenness correction circuit in the third embodiment. -
FIG. 7 explains an example of correction data creation in the first embodiment. -
FIG. 8 shows a structure of a conventional liquid crystal projector. -
FIG. 1 shows a structure of a liquid crystal projector (projection type image display device), which is an embodiment of the present invention. - First, an optical system in a
liquid crystal projector 100 will be described. InFIG. 1 , white light emitted from alight source 1 is transformed into substantially parallel rays of light by aparabolic mirror 2, a reflecting mirror (not shown), and a lens group (not shown). - The substantially parallel light is subjected to color separation by
dichroic mirrors 3 and 4, highly reflectingmirrors - Light rays that have entered the
liquid crystal panels liquid crystal panels - The modulated light of each color is subjected to color synthesis by a color synthesizing dichroic prism (color synthesizing optical element) 11, and is enlarged and projected onto a
screen 13 through aprojection lens group 12. - Two
dichroic membranes dichroic prism 11 without intersecting each other in the prism. - The
dichroic membrane 11 a synthesizes two kinds of color-modulated light among red modulated light, green modulated light, and blue modulated light that have mutually different wavelength ranges by its reflecting/transmitting action. Thedichroic membrane 11 b synthesizes the two kinds of color-modulated light that have been synthesized by thedichroic membrane 11 a and the remaining color-modulated light by its reflecting/transmitting action. The modulated light that has thus undergone the color synthesis is emitted from an emitting surface of theprism 11 to theprojection lens group 12. - In this embodiment, positive
refractive lens groups liquid crystal panels dichroic prism 11, and thereby the optical system is reduced in size. - Herein, each color-modulated light, which is substantially parallel light and which has been emitted from the
liquid crystal panels refractive lens groups dichroic films dichroic prism 11. Therefore, for the reason given in the description of the conventional technique, there is a fear that the nonuniformity of a brightness level (color unevenness) will occur in an image projected onto thescreen 13. However, according to this embodiment, this color unevenness can be corrected regardless of directions on the image, as described later. - Next, a description will be given of electric-signal processing in the liquid crystal projector according to this embodiment.
- An image signal, such as a video signal or VGA signal, that has been input to a
decoder 17 from the outside is digitized by thedecoder 17, and is sent to a signal-processing circuit 18. - The signal-
processing circuit 18 performs digital signal processing, such as resolution transformation or frame rate transformation, for the image signal, and performs LCD signal processing, such as gamma correction by which the VT characteristics of theliquid crystal panels - The signal-
processing circuit 18 further performs corrections necessary to correct the color unevenness in a color unevenness correction processing circuit (brightness irregularity correcting circuit) 19 for the image signal to be input to theliquid crystal panels - Since the image signal is corrected to cancel the color unevenness brightness irregularity or nonuniformity of a brightness level) by these corrections, no color unevenness occurs in the image (projection image) formed by light rays that has been modulated by the
liquid crystal panels prism 11. -
FIG. 2 shows in detail the signal-processing circuit 18 that includes the colorunevenness correction circuit 19. Image signals (DRi, DGi, DBi) digitized by thedecoder 17 are input to the colorunevenness correction circuit 19 through the digitalsignal processing circuit 22 for a scan converter or resolution transformation and through the LCDsignal processing circuit 23. - A
frame memory 24 in which correction data used to correct the color unevenness in horizontal and vertical directions is stored is connected to the colorunevenness correction circuit 19. Theframe memory 24 is made up of a ROM and other elements, in which the correction data is prestored. - The color
unevenness correction circuit 19 reads out correction data, which synchronizes with the image signals ARi, AGi and ABi input from the LCDsignal processing circuit 23, from theframe memory 24 by use of a timing signal from atiming generator 21, and corrects the image signals ARi, AGi and ABi in real time. -
FIG. 7 shows an example of a method for creation of correction data. First, with respect to each color, image signals, each having a uniform brightness level, are sequentially input to theliquid crystal panels - When projected onto the screen in this state, color unevenness occurs in the projected image on the screen in a horizontal or vertical direction. Herein, brightness data in the projected image on the screen of each color will be designated as Lr (x,y), Lg (x,y) and Lb (x,y), and a maximum brightness value in the brightness data of each color will be designated as Lr_max, Lg_max and Lb_max.
- The correction data mentioned here is a gain factor for performing a gain adjustment for each pixel of the
liquid crystal panels
Cr (x,y)=Lr_max/Lr (x,y) (1)
Cg (x,y)=Lg_max/Lg (x,y) (2)
Cb (x,y)=Lb_max/Lb (x,y) (3)
wherein (x,y) indicates coordinates at the spatial position of each pixel. - However, if there is no need to perform the procedure up to the gain adjustment for each pixel, the amount of correction data may be decreased so as to reduce the size of the
frame memory 24 by setting the correction data shown by the equations (1), (2) and (3) for each arbitrary pixel area for simplification. -
FIG. 3 (a) shows an example of a correcting operation when a uniform white (gray) color is displayed. Since image signals input to the liquid crystal panel is a uniform white (gray) color, the image signals ARi, AGi and ABi prior to corrections have no positional level difference, and have a constant level in both horizontal and vertical directions. - However, in order to prevent color unevenness from occurring in the projected image as described above, the correction data is created to cancel this color unevenness according to the method shown in
FIG. 7 . - In other words, although the image signal has a uniform brightness level (e.g., 255), such correction data so as to enlarge the gain is set as a projected image (modulated light) on the
screen 13 in a pixel or in a pixel area in which brightness becomes lower than the maximum brightness Lr_max, Lg_max and Lb_max because of the color unevenness. -
FIG. 3 (b) shows an example of correction data stored in theframe memory 24. Image signals (after-correction signals) obtained after completion of corrections are expressed as follows:
ARo (x,y)=Cr (x,y)×ARi (x,y) (4)
ABo (x,y)=Cb (x,y)×ABi (x,y) (5)
AGo (x,y)=Cg (x,y)×AGi (x,y) (6)
wherein Cr (x,y), Cb (x,y) and Cg (x,y) are red correction data, blue correction data and green correction data, respectively. - The after-correction signal (ARo, AGo, ABo) of each color that has passed through the color
unevenness correction circuit 19 is changed into a signal having an inclination or variation as shown inFIG. 3 (a). - Since the
liquid crystal panels screen 13. - As described above, according to this embodiment, electric signals input to the
liquid crystal panels - In the above embodiment (
FIG. 2 ), a description was given of a case in which color-unevenness-correction processing is applied to the output signal from the LCDsignal processing circuit 23 by means of the colorunevenness correction circuit 19. Instead of this, as shown inFIG. 4 , color unevenness correction processing can be applied to the output signal from the digitalsignal processing circuit 30 prior to the step of being input to the LCDsignal processing circuit 23. - In this case,
amplifiers FIG. 2 are realized bymultipliers - Further, in this case, since color unevenness correction processing is performed at the stage preceding the LCD
signal processing circuit 23 by which the VT characteristics of theliquid crystal panels
Cr (x,y)=Tvt — r [Lr_max/Lr (x,y)] (7)
Cg (x,y)=Tvt — g [Lg_max/Lg (x,y)] (8)
Cb (x,y)=Tvt — b [Lb_max/Lb (x,y)] (9)
wherein Tvt_r [L], Tvt_g [L] and Tvt_b [L] are voltage-transmittance characteristic transformation functions of theliquid crystal panels - Color unevenness correction processing may be performed at any position between the input of the digital
signal processing unit 22 and input of theLCD driving unit 20 according to methods other than the methods ofFIG. 2 andFIG. 4 as long as a correction circuit capable of gain control is disposed at each spatial position of a pixel or a pixel area. -
FIG. 5 shows the structure of a liquid crystal projector (projection type image display device), which is another embodiment of the present invention. In this embodiment, the same reference symbols as in the above embodiment are given to the same constituent elements as in the above embodiment. - In this embodiment,
dichroic membranes dichroic prism 50 are each formed with a gradient membrane in which thickness or a refractive index slantingly varies in a specific direction. The optical system ofFIG. 5 has the same structure as that ofFIG. 2 , except for the color synthesizingdichroic prism 50. - Since the gradient membrane are used as
dichroic membranes liquid crystal panels dichroic membranes - However, as in the above embodiment, an electric color unevenness correction is needed in the vertical direction.
- When gradient membranes used for the
dichroic membranes -
FIG. 6 shows an example of a correcting operation when a uniform white (gray) color is displayed on theliquid crystal panels line memory 51 is created to cancel the color unevenness in the vertical direction. - Only one-dimensional data in the vertical direction can be roughly used as correction data. However, if precisely corrected, two-dimensional data may be used as in the above embodiment.
-
FIG. 6 shows a case in which color unevenness correction processing is performed only in the vertical direction. In this case, thememory 51 can be formed with a line memory for a vertical line. - Image signals (after-correction signals) obtained after completion of corrections are expressed as follows:
ARo (y)=Cr (y)×ARi (y) (10)
ABo (y)=Cb (y)×ABi (y) (11)
AGo (y)=Cg (y)×AGi (y) (12)
wherein Cr (y), Cb (y) and Cg (y) are red correction data, blue correction data and green correction data, respectively, stored in theline memory 50. - Since the
liquid crystal panels screen 13. - As described above, according to this embodiment, the color unevenness of the projected image caused by the optical system is corrected by using the gradient membrane in the horizontal direction and by correcting the electric signals input to the
liquid crystal panels - Color unevenness correction processing may be performed at any position between input of digital
signal processing unit 22 and input ofLCD driving unit 20 according to methods other than the method ofFIG. 5 as long as a correction circuit capable of gain control is disposed at each spatial position of a pixel or a pixel area. - In each of the aforementioned embodiments, a description was given of a case in which the
prism 11 having the dichroic membrane is used as the color synthesizing optical element. However, without being limited to this prism, the present invention can be applied to a case in which other color synthesizing optical elements, such as an element in which a dichroic membrane is provided on a plate glass, are used. - Further, in each of the aforementioned embodiments, a description was given of a case in which the liquid crystal panel (LCD) is used as the image display element. However, the present invention can also be applied to a case in which image display elements other than the liquid crystal panel are used.
- As described above, according to all of aforementioned embodiments, it is possible to correct the nonuniformity (color unevenness) of a brightness level that easily occurs when a lens group with positive refractive power is disposed between a color synthesizing optical element and an image display element by a simple, inexpensive structure irrespective of whether a horizontal or vertical direction in the projected image, and is possible to project and display an image with high picture quality and with no color unevenness.
- Additionally, when a gradient membrane is used as a dichroic membrane in order to correct color unevenness in a specific direction, color unevenness in a direction that cannot be optically corrected by this gradient membrane can be electrically corrected with ease.
Claims (6)
1-5. (canceled)
6. A projection type image display device comprising:
a plurality of image display elements, each of which modulates light rays in accordance with an image signal;
a color synthesizing optical element comprising a dichroic film including a gradient film in which its thickness varies in a predetermined direction, the color synthesizing optical element synthesizing the light rays modulated by the plurality of image display elements;
a projection optical system projecting the light rays synthesized by the color synthesizing optical element onto a projection surface; and
a signal processing circuit which corrects the image signal by one of each pixel and each pixel area such that brightness irregularity in the predetermined direction of an image projected by the projection optical system is reduced or cancelled,
wherein the signal processing circuit corrects the image signal such that the brightness irregularity, which cannot be corrected by the gradient film, is reduced or cancelled.
7. The projection type image display device according to claim 6 , wherein the signal processing circuit corrects the image signal such that the brightness irregularity in the predetermined direction which cannot be corrected by the gradient film is cancelled.
8. The projection type image display device according to claim 6 , further comprising a positive refractive lens disposed between the image display elements and the color synthesizing optical element,
wherein an incident angle onto the dichroic film of the light rays condensed by the positive refractive lens varies in the predetermined direction.
9. The projection type image display device according to claim 6 , wherein the dichroic film reflects a first color light and transmits a second light, the first color light being one of red color light, a green color light and a blue color light with different wavelength regions, and the second color light being one of the other two lights that are not reflected.
10. A projection type image display device comprising:
a plurality of image display elements, each of which modulates light rays in accordance with an image signal;
a color synthesizing optical element comprising a dichroic film including a gradient film in which its refractive index varies in a predetermined direction, the color synthesizing optical element synthesizing the light rays modulated by the plurality of image display elements;
a projection optical system projecting the light rays synthesized by the color synthesizing optical element onto a projection surface; and
a signal processing circuit which corrects the image signal by one of each pixel and each pixel area such that brightness irregularity in the predetermined direction of an image projected by the projection optical system is reduced or cancelled, wherein the signal processing circuit corrects the image signal such that the brightness irregularity, which cannot be corrected by the gradient film, is reduced or cancelled.
Priority Applications (1)
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US11/126,371 US20050206851A1 (en) | 2001-01-26 | 2005-05-11 | Projection type image display device |
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JP2001-19078 | 2001-01-26 | ||
JP2001019078A JP2002223454A (en) | 2001-01-26 | 2001-01-26 | Projection type image display device |
US10/052,465 US6975337B2 (en) | 2001-01-26 | 2002-01-23 | Projection type image display device |
US11/126,371 US20050206851A1 (en) | 2001-01-26 | 2005-05-11 | Projection type image display device |
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US10/052,465 Continuation US6975337B2 (en) | 2001-01-26 | 2002-01-23 | Projection type image display device |
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US10/052,465 Expired - Fee Related US6975337B2 (en) | 2001-01-26 | 2002-01-23 | Projection type image display device |
US11/126,371 Abandoned US20050206851A1 (en) | 2001-01-26 | 2005-05-11 | Projection type image display device |
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US20120154659A1 (en) * | 2010-12-15 | 2012-06-21 | Hon Hai Precision Industry Co., Ltd. | Projector and method for adjusting projected image |
US20150208052A1 (en) * | 2014-01-20 | 2015-07-23 | Kabushiki Kaisha Toshiba | Image processor, image processing method, and image projector |
US11011102B2 (en) | 2017-09-21 | 2021-05-18 | Canon Kabushiki Kaisha | Display apparatus and control method therefor |
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Also Published As
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US20040012616A1 (en) | 2004-01-22 |
US6975337B2 (en) | 2005-12-13 |
JP2002223454A (en) | 2002-08-09 |
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