Image display device
Contents
1. 0038 FIG 6 is a configuration diagram illustrating the outer appearance of an image display system 600 employing a projector 101 which is an image display device according to the present invention 0039 FIG 7 is a functional block diagram illustrating the internal configuration of the projector 101 and 0040 FIG 8 isa diagram illustrating how to control in the projector 101 the number of black period subframes depend ing on the type of content and operating environment DESCRIPTION OF THE PREFERRED EMBODIMENTS 0041 Hereinafter embodiments of the present invention will be described with reference to the accompanying draw ings First Embodiment 0042 An image display device according to a first embodiment of the present invention will be described with reference to FIG 1 0043 FIG 1 is a configuration diagram illustrating the outer appearance of a projector 100 which is an image dis play device according to the present invention In FIG 1 US 2011 0234647 A1 when a user of the projector 100 presses a POWER button 150 power is fed to the projector 100 The projector 100 then processes video signals inputted thereto and outputs enlarged projection images through a projection lens 190 by using a LED light source module not shown included in the projec tor 100 0044 The projector 100 includes as input interfaces an RGB input 160 and a video input 170 which are respectively connected to an external vid2. the conventional projectors have insufficient luminance and in most cases due to the influence of such factors as the room lighting or the screen have been prohibitive of representing for example a pre pared chart with the colors visually recognizable as on the computer screen Thus to solve this problem in recent years image display devices that are equipped with solid state light sources such as light emitting diodes LEDs and laser diodes LDs in place of the conventional ultra high pressure mer cury lamps have been proposed 0006 In order to display color images a conventional image display device is equipped with solid state light sources which emit light having wavelengths of three primary colors red hereinafter referred to as R green hereinafter referred to as G and blue hereinafter referred to as B and a modulator that is used in common for each of the solid state light sources The conventional image display device adopts a field sequential system which renders color images by high speed flickering of the light from the solid state light sources and by controlling the modulator which modulates in accordance with the flickering time the light corresponding to the respective colors e g see Japanese Laid Open Patent Publication No 2008 20600 0007 The conventional field sequential system has an R display period a G display period and a B Display period which occur in order In the R display perio
3. 62 using the input synchro nization signal as the reference 0084 Next based on an output synchronization signal generated by the timing generator 62 image data ofone frame is read from the frame memory 61 The display device con US 2011 0234647 A1 troller 90 generates based on the read image data of one frame subframes each further divided into subfields thereby to control the DMD 91 0085 The light source drive controller 63 controls lighting of R LEDs 81 G LEDs 82 and B LEDs 83 in the LED light source module based on n times synchronization signals which corresponds to n subframes generated by the timing generator 62 0086 In the projector 101 according to this embodiment in which subframe period the black period is to be provided is substantially the same in the first embodiment of the present invention illustrated in FIG 3 to FIG 5 In this embodiment the number of subframes of black period can be also con trolled depending on the type of content and operating envi ronment The number of subframes of the black period may be set by a user s selection of a display mode That is the user operates the remote control 60 or the operation buttons 140 to select the display mode Alternatively projectors may have their individual display modes which are set in advance depending on the types of the projector 0087 FIG 8 is a diagram illustrating how to control the number of subframes ofthe black period in the projec
4. E i i A D RESIZING FRAME DISPLAY i LING 4 RA DEVICE CONVERTER oi 0 pul d i i i 3 b LED 1 SOURCE eee S MODULE L 3 S 5 i BAIN i i 1 matge TIGHT SOURCE I DRIVE CONTROLLER 1 es 83 71 ERNAL INTERFACE p H P US 2011 0234647 A1 Sep 29 2011 Sheet 1 of 8 Patent Application Publication 091 ANANI 8 OLL if dM b OPL NOling 006 28008 4 pa KOLING 4 3 X b OEL 1904 8 k aor K OGL SN31 110083 QOL 0 E US 2011 0234647 A1 Sep 29 2011 Sheet 2 of 8 Patent Application Publication 2 a 230 AN V lo RS EE 90 AAJLNI 823111001000018 NIVE e P 5 ELDER deme w w die AIAN Ayd Z f M H 9 ES 1 11011 09 86 rt 98008 LHOTE eer ond i TU 3 deu enis mam 300008 an 1109819 SNIZIS34 96 8 96 3019335 ifidNT 1001 ZNR 4300930 80 109 9 7 P 0 y URE gz 1011109035 H 1 H i 1 vg NN NM AdGdA BOY 1109815 181
5. Hz is inputted As illustrated in FIG 3 one cycle 4o sec includes eight subframes and each subframe includes R LED subfield G LED subfield and B LED sub field 0062 In each subfield to smooth the luminance 8 bit patterns 256 patterns are divided by eight into 32 levels each having five luminance levels 0063 Turning off all the R LED G LED and B LED is performed in units of subframes As shown in FIG 3 all the R LEDs G LEDs and B LEDs is turned off in the eighth subframe which is the last subframe whereby a black period is realized in the subframe 0064 Next an operation of the projector 100 which is an image display device according to the present invention will be described 0065 A PAL signal inputted through the VIDEO terminal 11 is separated by the Y C separation circuit 23 into a Y signal and a C signal and the separated Y signal and C signal are subjected to color decoding by the color decoder 22 and decoded into a Y signal a Pb signal and a Pr signal The Y signal the Pb signal and the Pr signal are converted to an R signal a G signal and a B signal and then are subjected to A D conversion by the A D converter 30 0066 The resizing circuit 40 resizes the digital signal which is subjected to the A D conversion by the A D converter 30 to 1024x768 pixels so as to correspond to the resolution of the DMD 91 and then writes the resized digital signal into the frame memory 61 The digital signal writ
6. Qi Patent Application Publication Le w st N gt 4 9 es fij 2 S j SUID N Ox NOLLYZINONHONAS A 7 NOIIVZINONHONAS A S 5 37700100 0 ETT 2 35 wg BNIZINONHONAS e 2 i f iON H NOLLVZINGHHONAS H e e r un N e i 7019 amp 13110 910 5 NANOS 0301 I E 39 B Da S E 2 E Old Q E e US 2011 0234647 A1 Sep 29 2011 Sheet 8 of 8 Patent Application Publication 3l Py 2 H 13 31 16111 08 440 15711 No 3078 2010 x HNE THON OLNVNAG 3000 0301A CNN eX US 2011 0234647 A1 IMAGE DISPLAY DEVICE CROSS REFERENCE TO RELATED APPLICATION 0001 The disclosure of Japanese Patent Application No 2010 071995 filed on Mar 26 2010 is incorporated herein by reference BACKGROUND OF THE INVENTION 0002 1 Field of the Invention 0003 The present invention relates to image display devices that display color images and more particularly relates to color image displaying image display devices that control after images in motion pictures 0004 2 Description of the Background Art 0005 Conventionally images are displayed on screens by using projectors which employ ultra high pressure mercury lamps However such conventional projectors have a rela tively short life span and have been prohibitive of realizing instant switch on In addition
7. of inserting a black signal synchronized to a vertical synchronization signal as well as a technique of turning off the light that illuminates the display device have been disclosed However according to the conventional tech niques the black periods are distributed and the black period time span is short and thus it has not been possible to reduce the motion blur sufficiently SUMMARY OF THE INVENTION 0011 Therefore an object of the present invention is to make available an image display device that can reduce motion blur arising from a hold type display device in which after images remain on the retina of a person s eyes when observing moving objects and that enables the resolution of moving images to be improved 0012 To attain the above objects the present invention has the following features A first aspect of the present invention is an image display device for projecting and displaying an image ona screen the device comprising a plurality of solid state light sources a modulator configured to modulate light from the plurality of solid state light sources and an image display device configured to generate from a frame of image data a plurality of subframes that are each further divided into subfields and to display the plurality of subframes The modulator turns off light output from all the solid state light sources for the duration of at least one or more subframes among the plurality of subframes 0013 With t
8. 7 In a further aspect the number of the subframes displayed in black is preferably changed in accordance with the type of content and operating environment of the image display device 0028 For example even if the number of subframes is fixed there is a case where the duration of a subframe varies depending on the frequency of the vertical synchronizing signal However with the above described configuration the number of subframes during which the light output from all the solid state light sources is turned off is set optimally 0029 Further in accordance with the movement speed of an object in a moving image in accordance with the signal type to be inputted or in accordance with the type of content to be displayed for example the number of subframes during Sep 29 2011 which the light output from all the solid state light sources is turned off can be optimally set 0030 As described above with the image display device of the present invention a frame period includes a period during which the light output from all the solid state light sources is turned off or during which a black signal is inserted as a video signal to realize a black display Thus it is possible to reduce motion blur arising from a hold type display device in which after images remain on the retina of a per son s eyes when viewing moving objects In addition it is possible to improve the resolution of moving images 0031 The image display device
9. 8 ek WNINNSL 0381 5 US 2011 0234647 A1 Sep 29 2011 Sheet 3 of 8 Patent Application Publication 238 057 1 TWNOTS ON EZ 5 110180 H PENES ES 1 30 7 SHVAN HIH913 19814 US 2011 0234647 A1 Sep 29 2011 Sheet 4 of 8 Patent Application Publication 07 18 8 4 1 i i z i 7 z i i i j 3 E 1 i H 1 1 f f 1 1 3 eee H i i 3005 HL H 913 28 IECH 5 49 1 iex US 2011 0234647 A1 Sep 29 2011 Sheet 5 of 8 Patent Application Publication G0DEM 00124 lega g yis xdg 3131 0 1 WIS SNLZINOHUONAS 8 Kadans ee Da 0 EE E et US 2011 0234647 A1 09 081100 310 7 9 00 TVNOS dd Sep 29 2011 Sheet 6 of 8 lt y em e ble o Ert UD pee t EM 20 011 75 oe e e 2215 Sa w w Kos v 4 E 008 3 5 16310 1 9
10. US 20110234647A1 a2 Patent Application Publication o Pub No US 2011 0234647 A1 as United States Kimoto et al 43 Pub Date Sep 29 2011 54 IMAGE DISPLAY DEVICE 75 Inventors Takayuki Kimoto Osaka JP Takaaki Gyoten Hyogo JP Yoshimasa Fushimi Osaka JP 73 Assignee PANASONIC CORPORATION Osaka JP 21 Appl No 13 037 382 22 Filed Mar 1 2011 30 Foreign Application Priority Data Mar 26 2010 OD 2010 071995 VIDEO TERMINAL 7 ELECTOR 21 5 i X COLOR Gr Publication Classification 51 Int Cl G09G 5 10 2006 01 345 690 a 1 93 ABSTRACT 57 An image display device includes a plurality solid state light sources a modulator configured to modulate light from a plurality of solid state light sources and an image display device configured to generate from a frame of image data a plurality of subframes each further divided into subfields and to display the plurality of subframes The modulator turns off light output from all the solid state light sources for the dura tion of one or more of the plurality of subframes whereby it is possible to reduce motion blur arising from a hold type display device in which after images remain on the retina of a person s eyes when viewing moving objects DECODER S VIDEO TERMINAL 12 o ad ei 7 91 1 I
11. according to the present invention can advantageously reduce motion blur of moving images displayed on an extensive color gamut display which employs LED sources and is suitable for high definition high resolution display such as a high definition television 0032 These and other objects features aspects and advantages of the present invention will become more appar ent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings BRIEF DESCRIPTION OF THE DRAWINGS 0033 FIG 1 is a configuration diagram illustrating the outer appearance of a projector 100 which is an image dis play device according to the present invention 0034 FIG 2 is a functional block diagram illustrating the internal configuration of the projector 100 0035 FIG 3 is a timing chart illustrating an operation of an LED module 210 in the case where a PAL Phase Alter nating Line signal whose vertical synchronizing signal has a frequency of 50 Hz is inputted 0036 FIG 4 is a timing chart illustrating an operation of the LED module 210 in the case where an NTSC National Television System Committee signal whose vertical syn chronizing signal has a frequency of 60 Hz is inputted 0037 FIG 5 is a timing chart illustrating an operation of the LED module 210 in the case where first and second subframes which are two consecutive subframes of first to eighth subframes are set as black periods
12. at ing the subframe of the black period is not limited thereto For example the subframe of the black period may be generated by controlling the display device controller 90 thereby to output a black signal as a video signal and this technique exerts the same effect as the above described technique 0095 The projectors according to the first and second embodiments of the present invention employ the DMD However the projector may be realized by an LCD projector 0096 The processing of the present invention may be real ized by software That is the present invention is not limited to an image display device and is applicable to a display method 0097 While the invention has been described in detail the foregoing description is in all aspects illustrative and not restrictive It will be understood that numerous other modifi cations and variations can be devised without departing from the scope of the invention What is claimed is 1 An image display device for projecting and displaying an image on a screen the device comprising a plurality of solid state light sources a modulator configured to modulate light from the plurality of solid state light sources and an image display device configured to generate from a frame of image data a plurality of subframes each fur ther divided into subfields and to display the plurality of subframes wherein the modulator is configured to turn off light output from all the solid s
13. d only R LEDs which emit light having R wavelengths are lit whereas the remaining light sources are turned off and the modulator modulates only the R light Accordingly an R image is dis played In the same manner to display a G image and a B image G LEDs which emit light having G wavelengths and B LEDs which emits light having B wavelengths are lit The modulator then modulates the G light and the B light respec tively 0008 Another conventional image display device adopts a digital micromirror device DMD registered trademark of Texas Instruments Incorporated as a modulator e g see US Pat No 5 969 710 and U S Pat No 6 778 155 This device employs a technique of bit splitting in which during each of the R display period the G display period and the B display period the DMD uniformly distributes within each period the time during which it reflects light from each light source so as to reduce nonuniformity in light reflection time thereby smoothing the luminance Sep 29 2011 0009 However unlike impulse type display devices such as cathode ray tubes conventional hold type display devices such as DMD employing image display devices and liquid crystal displays cause a problem of generating image blur motion blur depending on the movement speeds of objects in moving images 0010 In order to reduce motion blur that arises in accor dance with the moving speed of an object in a moving image a technique
14. e of the eighth sub frame as shown in FIG 3 and thereby it is possible to reduce image blur motion blur caused by after images remaining on the retina ofa person s eyes when viewing moving objects 0071 According to the projector 100 i e the image dis play device of the present invention the luminance is smoothed by using the bit splitting technique which avoids generation of moving image pseudo contours And in addi tion a period allocated to each bit of luminance does not depend on the size of the bit but the luminance is uniformly distributed in the respective subframe periods and thus smooth luminance distribution is realized As a result even if a black period is provided in the subframe it is possible to minimize gradation insufficiency and thus the motion blur reduction effect by the black period insertion can be exerted 0072 As shown in FIG 3 this embodiment describes the case where the PAL signal is inputted whose vertical syn chronizing signal has the frequency of 50 Hz However the present invention is not limited to this but for example a NTSC signal whose vertical synchronizing signal has a fre quency of 60 Hz may be applied 0073 FIG 4 is a timing chart illustrating an operation of the LED module 210 in the case where the NTSC signal whose vertical synchronizing signal has the frequency of 60 Hz is inputted As shown in FIG 4 one cycle o sec includes eight subframes and each subframe period is sh
15. eo signal output device not shown such as a personal computer The projector 100 includes a USB port 130 If a mouse 200 is connected to the projector 100 via the USB port 130 the mouse accepts the user s operation and functions as a pointer moving on a screen on which the setting status of the projector 100 and enlarged projection images are displayed Operation of the operation buttons 140 by the user also realizes the same function 0045 Next with reference to FIG 2 the internal configu ration of the projector 100 will be described FIG 2 is a functional block diagram illustrating the internal configura tion of the projector 100 0046 A VIDEO terminal 11 receives inputs of composite video signals which are defined based on the National Tele vision System Committee NTSC system and the Phase Alternating Line PAL system 0047 An S VIDEO terminal 12 receives inputs of S VIDEO signals 0048 AnRGB YPbPr terminal 13 receives inputs of RGB signals or YPbPr signals 0049 An input selector 21 is used for selecting either composite video signals inputted through the VIDEO termi nal 11 or the S VIDEO signals inputted through the S VIDEO terminal 12 0050 A Y C separation circuit 23 is a circuit which sepa rates a composite video signal inputted through a color decoder 22 into a Y signal and a C signal 0051 The color decoder 22 performs color decoding of Y signal and C signal which have been subjected to Y C separat
16. evice that is controls the power supply not shown fan not shown temperature not shown input switching and the like for example The main microcomputer 70 also sets the number of subframes that are to be displayed in black based on the data from an external interface 71 The main micro computer 70 controls a light source drive controller 63 based on the set number of subframes that are to be displayed in black 0059 In addition the main microcomputer 70 forwards to the light source drive controller 63 the level of current of the LEDs to be driven and sets the desired value in the LED light source module 210 The LED light source module 210 includes R LEDs G LEDs and B LEDs 0060 A display device controller 90 controls driving of the DMD 91 so that the respective pixels corresponding to the R LED G LED and B LED are driven in desired subframes and subfields More specifically the display device controller 90 uses the bit splitting technique which uniformly distrib utes in the respective periods of the R display period G display period and B display period the timeto reflect by the DMD each light ray from the corresponding light source so as to reduce nonuniformity of the light reflection time thereby smoothing the luminance 0061 FIG 3 is a timing chart illustrating an operation of the LED module 210 in the case where a Phase Alternating Line PAL signal whose vertical synchronizing signal has a frequency of 50
17. f And it is possible to further reduce motion blur arising from the hold type display device US 2011 0234647 A1 0018 In a further aspect the number of the subframes during which the light output from all the solid state light sources is turned offis preferably changed in accordance with the type of content and operating environment of the image display device 0019 For example even if the number of subframes is fixed there is a case where the duration of a subframe varies depending on the frequency of the vertical synchronizing signal However with the above described configuration the number of subframes during which the light output from all the solid state light sources is turned off is set optimally 0020 Further in accordance with the movement speed of an object in a moving image in accordance with the signal type to be inputted or in accordance with the type of content to be displayed for example the number of subframes during which the light output from all the solid state light sources is turned off can be optimally set 0021 Ina second aspect the present invention is an image display device for projecting and displaying an image on a screen the device comprising a plurality of light sources a modulator configured to modulate light from the plurality of light sources and an image display device configured to generate from a frame of image data a plurality of subframes each further divided into subfields and t
18. his configuration a frame includes a period during which the light output from all of the solid state light sources is turned off Accordingly it is possible to reduce motion blur arising from a hold type display device in which after images remain on the retina of a person s eyes when observing moving objects In addition since a frame includes a period during which the light output from all the solid state light sources is turned off power consumption can be reduced 0014 Ina further aspect the subframes during which the light output from all the solid state light sources is turned off preferably includes among the plurality of subframes the initial or final subframe within a single frame period 0015 With this configuration the center of the time axis of a video display in a single frame period can be advanced retarded and thus it is possible to adjust the amount of delay with respect to lip sync in a single frame 0016 Ina further aspect the one or more of the plurality of subframes during which the light output from all the solid state light sources is turned off are preferably two or more consecutive subframes of the plurality of subframes 0017 With this configuration it is possible to avoid after images remaining on the retina of a person s eyes when observing moving objects as compared to a case of distribut ing the black periods during which the light output from all the solid state light sources is turned of
19. ing the outer appearance of an image display system 600 employing a projector 101 which is an image display device of the present invention In FIG 6 a personal computer 61 is con nected to an RGB terminal corresponding to the RGB input 160 ofthe projector 100 illustrated in FIG 1 ofthe projector 101 and an image on the personal computer 61 is projected ona screen 110 by the projector 101 In this case functions of the projector 101 may be controlled by the user s operation of a remote control 60 0081 The basic configuration ofthe projector 101 accord ing to this embodiment is substantially the same as that ofthe projector 100 according to the first embodiment ofthe present invention illustrated in FIGS 1 and 2 Thus no description will be given of the same components in the configuration and those components which are different from those in the projector 100 will be described 0082 FIG 7 is a functional block diagram illustrating the internal configuration of the projector 101 FIG 7 illustrates the relation between an input video signal and an input syn chronization signal and also illustrates in detail a part of the internal configuration which is different from that of the projector 100 illustrated in FIG 2 0083 Theinput video signal which is resized by the resiz ing circuit to have the same resolution as the DMD is written into the frame memory 61 based on a timing signal which is generated by the timing generator
20. ing to claim 5 wherein the one or more of the plurality of subframes displayed in black includes among the plurality of subframes the initial or final subframe within a single frame period Sep 29 2011 7 The image display device according to claim 6 wherein the one or more of the plurality of subframes displayed in black are two consecutive subframes of the plurality of the subframes 8 The image display device according to claim 6 wherein the number of the subframes displayed in black is changed in accordance with the type of content and operating environ ment of the image display device
21. ion by theY C separation circuit 23 or Y C signal into a YPbPr signal The YPbPr signal is converted to the RGB signal by a matrix circuit not shown 0052 The matrix circuit 24 is designed to perform matrix processing when the YPbPr signal inputted through the RGB YPbPr terminal 13 is converted to the RGB signal 0053 An input selector 25 is used for selecting a signal representing either the RGB signal inputted through the RGB YPbPr terminal 13 or the RGB signal generated by the matrix circuit 24 0054 An input selector 26 is used for selecting either the YPbPr signal generated by the color decoder 22 or the RGB signal inputted by the input selector 25 The signal to be inputted to the input selector 26 is an analog video signal and the analog video signal selected by the input selector 26 is inputted to an analog digital A D converter 30 0055 The A D converter 30 performs A D conversion of the analog video signal selected by the input selector 26 to an 8 bit digital signal 0056 A resizing circuit 40 resizes the digital signal which has been subjected to the A D conversion by the A D con verter 30 so as to be displayed on the screen in accordance with the number of pixels in a DMD 91 0057 The frame memory 61 converts the vertical fre quency ofthe inputted signal to 50 Hz or 60 Hz and includes data used for field sequential driving of the DMD 91 Sep 29 2011 0058 A main microcomputer 70 controls the whole d
22. o display the plurality of subframes The image display device is configured to dis play one or more of the plurality of subframes in black 0022 With this configuration even if the light output from all the solid state light sources is not turned off a black signal is inserted as a video signal thereby to realize a black display Thus it is possible to reduce motion blur arising from a hold type display device in which after images remain on the retina of a person s eyes when viewing moving objects 0023 Ina further aspect theoneor more ofthe plurality of subframes displayed in black preferably includes among the plurality of subframes the initial or final subframe within a single frame period 0024 With this configuration the center of the time axis ofa video display in a frame period can be adjusted and thus it is possible to adjust the amount of delay relative to lip sync in the frame 0025 Ina further aspect the one or more of the plurality of subframes displayed in black are preferably two consecutive subframes of the plurality of the subframes 0026 With this configuration it is possible to avoid after images remaining on the retina of a person s eyes when view ing moving objects as compared to a case of distributing the black periods during which the light output from all the solid state light sources is turned off And it is possible to further reduce motion blur arising from the hold type display device 002
23. of subframes level ofthe black period are to be inserted then the user can easily reduce motion blur in accordance with the types of content and operating environment Accordingly an optimal setting can be realized to maintain the projector luminance 0091 That is an optimal setting can be realized for vari ous content in accordance with the type of content and the operating environment for example a game content which includes objects moving at high speed and thus requires a longer black period or a content including few moving images which requires improved brightness and thus requires a shorter or no black period 0092 To the RGB YPbPr terminal 13 an RGB signal ora YPbPr signal is inputted Generally the YPbPr signal repre sents a moving image and the RGB signal represents a still Sep 29 2011 image Thus it can be set such that if the YPbPr signal is inputted the number of subframes of the black period is increased 0093 Still there may be a case where an RGB signal which represents a moving image is inputted In this case it can be set such that even ifthe RGB signal is inputted the user can manually increase the number of subframes of the black period thereby to reduce motion blur 0094 The projectors according to the first and second embodiments of the present invention turn off the LEDs and generate the subframe of the black period thereby realizing reduction in motion blur However the technique of gener
24. orter than that illustrated in FIG 3 Accordingly in the consecutive two subframe periods i e in the seventh and eighth sub frames all the R LEDs G LEDs and B LEDs are turned off to provide a black period and thereby motion blur is reduced 0074 Further in FIG 3 and FIG 4 among the first to eighth subframes the last frame ofthe eighth subframe or the consecutive last two subframes of the seventh and eighth subframes are set as the black period However setting ofthe black period is not limited to these 0075 For example in the case where images change on a frame by frame basis at respective frame boundaries the first frame or the first consecutive two subframes i e the first and second subframes among the first to eighth sub frames may be set as the black period FIG 5 is a timing chart illustrating an operation of the LED module 210 in the case where the first two consecutive subframes among the first to eighth subframes i e the first and second subframes are set as the black period As shown in FIG 5 after a synchroniza tion signal is inputted in the two consecutive subframe peri ods of the first and second subframes all the R LEDs G LEDs and B LEDs are turned off to provide the black period Accordingly motion blur can be reduced in the same Sep 29 2011 manner as the case where all the R LEDs G LEDs and B LEDs are turned off in the consecutive two subframe peri ods of the seventh and eighth
25. subframes to provide the black period 0076 In FIG 4 the center of the luminance central lumi nance ofan image ofa frame is located in the third and fourth subframes whereas in FIG 5 the central luminance is located in the fifth and sixth subframes Thus by setting the black period either in the seventh and eighth subframes or in the first and second subframes among the first to eighth subframes it is possible to adjust image delay relative to sound 0077 In the case where the vertical synchronizing signal has the frequency of 60 Hz all the R LEDs G LEDs and B LEDs are turned off in two or three subframes to provide the black period whereby motion blur is reduced and in addition deterioration in the projector luminance can be made indistinct Specifically 10 to 3096 of all the subframes can be set as the black period 0078 Here the more the number of subframes ofthe black period is increased the more the motion blur is reduced and thereby the moving image resolution can be improved How ever the increased number of subframes of the black period deteriorates the projector luminance In that case the number of subframes of the black period is controlled depending on the type of content and operating environment Second Embodiment 0079 A picture display system according to a second embodiment of the present invention will be described with reference to FIG 6 0080 FIG 6 is a configuration diagram illustrat
26. tate light sources for the duration of at least one or more subframes among the plurality of sub frames 2 The image display device according to claim 1 wherein the subframes during which the light output from all the solid state light sources is all turned off includes among the plurality of subframes the initial or final subframe within a single frame period 3 The image display device according to claim 2 wherein the one or more ofthe plurality of subframes during which the light output from all the solid state light sources is turned off are two or more consecutive subframes of the plurality of subframes 4 The image display device according to claim 1 wherein the number of the subframes during which the light output fromallthe solid state light sources is turned offis changed in accordance with the type of content and operating environ ment of the image display device 5 An image display device for projecting and displaying an image on a screen the device comprising a plurality of light sources a modulator configured to modulate light from the plurality of light sources and US 2011 0234647 A1 an image display device configured to generate from a frame of image data a plurality of subframes each fur ther divided into subfields and to display the plurality of subframes wherein the image display device is configured to display one or more of the plurality of subframes in black 6 The image display device accord
27. ten into the frame memory 61 is outputted from the frame memory 61 in asso ciation with a synchronization signal 0067 The display device controller 90 generates subfields and subframes so that lighting times of the R LED G LED and B LED in the LED light source module 210 satisfy the timing chart illustrated in FIG 3 and transfers the data to the DMD 91 In addition the display device controller 90 con trols ON OFF ofthe DMD 91 thereby to realize the gradation expression US 2011 0234647 A1 0068 Here in the case of the PAL signal its vertical synchronizing signal has a frequency of 50 Hz and one sub frame period thereof is longer than that of NTSC signal whose vertical synchronizing signal has a frequency of 60 Hz As shown in FIG 3 in the eighth subframe period all the R LEDs G LEDs and B LEDs are turned off to provide a black period and thereby motion blur is reduced 0069 The more the number of subframes of the black period increases the more the motion blur is reduced and thereby the moving image resolution can be improved How ever the increased number of subframes of the black period deteriorates the projector luminance In that case the number of subframes of the black period is controlled depending on the type of content and operating environment 0070 As described above according to the projector 100 i e the image display device of the present invention the black period is provided in the last fram
28. tor 101 depending on the type of content and operating environment As shown in FIG 8 in the projector 101 video modes are prepared in advance which include for example a cinema mode which suppresses brightness of highlighted portions in movie contents a dynamic mode which emphasizes bright ness and the like Insertion of a black period in the dynamic mode which emphasizes brightness deteriorates the bright ness Thus in such a video mode insertion ofthe black period is controlled not to be performed 0088 As described above depending on the video modes the light source drive controller 63 controls the R LEDs 81 G LEDs 82 and B LEDs 83 not to be turned off in subframes or controls the number of subframes during the period of which all the LEDs are turned off and thereby the light source drive controller 63 controls the number of subframes of the black period 0089 Alternatively an ON OFF control of black period insertion may be performed on a onscreen menu 250 by the user s manual operation using the remote control 60 or the operation buttons 140 Alternatively it may be set such that the user may be allowed to select the number of subframes level of the black period to insert the black period 0090 As described above if operation of the remote con trol 60 or the operation buttons 140 allows the user to select a video mode to determine whether the black period is to be inserted and to determine how many number
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