JP4186905B2 - Color wheel and projection display device using the same - Google Patents

Description

  The present invention relates to a color wheel for performing color display in a time-division and color-sequential manner in a projection display apparatus that enlarges and projects a display of a spatial light modulation element, and a projection display apparatus using the color wheel. .

  Large screen displays in home theaters and presentations have recently attracted attention, and display images of spatial light modulation elements such as small liquid crystal panels, DMD (Digital Micromirror Device), and LCOS (Liquid Crystal On Silicon) are enlarged and projected by projection lenses. However, a projection display device that obtains a large-screen display image has been commercialized.

  DMD is an example of a spatial light modulator developed by Texas Instruments, Inc. in the United States, and is mainly used as a projection display device. The DMD is configured by arranging hundreds of thousands to one million or more of extremely small mirrors corresponding to one pixel on one chip. The on / off state is controlled by tilting the mirror and changing the emission angle of the light beam incident on the mirror.

  As a method of the projection display device, there are mainly a three-plate type using three spatial light modulation elements and a single-plate type using only one. In particular, as an example of a single-plate projection display device, a color sequential method is employed in which colors are periodically switched in a time-sharing manner, and each color appears to be additively mixed with the eyes. Specifically, each pixel of the spatial light modulator has red (R), green (G), and blue (B) values in time series, and during each frame period, each pixel of the frame. Are sequentially addressed by R, G, then B data. On the other hand, these same color filters are arranged in a disc shape, and a color wheel having at least three different color regions is synchronized with this data, whereby the data for each color is displayed by the spatial light modulator. . As described above, color display is possible by time division, and if the time division rate becomes faster than the standard display speed of 60 images per second, the eyes perceive the image as having an original color.

  In such a time-division color sequential projection display device, the color cycle of the color wheel (repeated three times in the order of RGB, such as RGBRGBRGB, in the order of the number of RGB appearing in one field or in order of color) , Hereinafter referred to as a color sequence), the color division speed, and the color purity of the filter have a great influence on the quality and brightness of the display image.

  Hereinafter, a projection display device using a conventional color wheel will be described as an example.

  Conventionally, a projection display device described in Patent Document 1 is known. FIG. 11 shows a schematic diagram thereof. In FIG. 11, 111 is a color wheel, 112 is a DMD, 113 is a lamp, 114 is a projection lens, 115 is a screen, 116 is a field lens, and 117 is a concave mirror.

  The operation of the conventional projection display device will be described. The lamp 113 is a discharge-type high-power lamp such as a xenon, metal halide lamp, or ultra-high pressure mercury lamp. The lamp 113 is disposed almost at the focal position of the concave mirror 117, and the white light emitted from the lamp 113 is reflected by the concave mirror 117 having an elliptical shape. It arrange | positions so that it may condense on a color filter. The color wheel 111 is configured such that color filters of R, G, and B colors are arranged in a disk shape, and rotates at a constant speed. At this time, the DMD 112 displays an image frame corresponding to the color of the light in synchronism with each color filter blocking white light emitted from the lamp and color-separating into R, G, and B in time division. In a single image frame, the color wheel 111 is rotated at a rate of 1 rotation per image frame or 3600 rotations per minute for a normal 1/60 second. In such a system, there are three color sub-frames between one frame frequency, each of which is R, G, B, and the light beams separated in this way become parallel light by the field lens 116. The DMD 112 is irradiated. For each color, the DMD 112 switches the display image at a very high speed, and each modulated color light beam is enlarged and projected onto the screen 115 using the projection lens 114. In the display projected on the screen, images of each color of R, G, and B are sequentially displayed within 1/60 seconds, so that it appears as an afterimage to the eyes and a full color image is recognized.

  Patent Document 2 discloses an example of a system developed for such a problem that gradation characteristics are limited depending on the response speed of DMD in such a projection display device. FIG. 12 is a schematic diagram of a color wheel described in Patent Document 2. In this color wheel, R, G, and B color filters are arranged at a predetermined ratio in the circumferential direction, and in particular, by providing low-brightness filter regions R + NDF, G + NDF, and B + NDF with low transmittance in each color filter region. This realizes high gradation display. Even when this color wheel is used, white light emitted from the lamp is color-separated into R, G, and B in a time-sharing manner to illuminate the DMD and perform color sequential display as in the projection display device shown in FIG. . Since the DMD is a binary display of turning on and off the mirror, the gradation is driven by pulse width modulation (hereinafter abbreviated as PWM). Since the time of the video signal 1 bit (LSB) depends on the response speed of the mirror, high gradation display is difficult. Therefore, a low gradation filter region NDF is provided in the color wheel to realize a high gradation by reducing the light intensity and optically creating LSB. Specifically, when the transmittance of the low-brightness filter region is ½ that of the normal filter region, the luminance displayed through the low-brightness filter region passes through the normal filter region even if the mirror on-time is the same. Therefore, the lower LSB display of the video signal becomes possible.

However, since the brightness of the system decreases when the low-luminance filter area is increased, the low-luminance filter area G1 ′ is provided only for G with the highest visibility as practically as in the color wheel shown in FIG. Furthermore, if the number of sequential colors, which is the number of RGB appearances in one field, is small, an unnecessary coloring phenomenon called color separation occurs in the display, and therefore, generally, the center angle of one color wheel has a central angle as shown in FIG. Two RGB filters are arranged in pairs so as to be equal for each color. In this way, it is possible to realize a color sequential number of times that is twice the number of rotations of the color wheel. Actually, RGB is switched 6 times in one field by rotating at 10800 rpm (hereinafter, such a color sequence is referred to as 6x). At this time, since the low luminance filter G ′ appears three times in one field, only G can represent the lower bits.
JP-A-8-21977 JP-A-9-149350

  In a projection display device using a color wheel as shown in FIG. 13, for example, when an AC lighting type ultra-high pressure mercury lamp is used as a light source, it is necessary to perform pulse driving at a certain lighting frequency. The lamp generates a transient phenomenon called overshoot when the driving pulse polarity is reversed, and emits a light output having an abnormal intensity for a very short time. Therefore, by synchronizing the timing at which overshoot occurs with the color switching timing of the color wheel, the display linearity is not impaired by overshoot within the display period. This is because, when switching color filters, a driving method is employed in which the display element is forcibly turned off in order to prevent color mixture of the two colors. However, when the lamp lighting frequency is, for example, 180 Hz, in the 6x color sequence, it is necessary to switch the lamp lighting frequency for each RGB 1x, and an overshoot occurs each time. Accordingly, the lighting frequency of the lamp must be switched at any two rotationally symmetric positions, but no suitable position can be found with a color wheel as shown in FIG. For example, if the boundary between the R filter and the B filter is the first lamp lighting frequency switching position, the next frequency switching position is approximately the center of the low luminance filter, and the uniformity of display is lost due to the influence of overshoot.

  Therefore, if the low-brightness filter G2 ′ is provided so as to be symmetric with the low-brightness filter G1 ′ as shown in FIG. 14, it becomes rotationally symmetric at any color filter switching position, and the problem of display uniformity due to lamp overshoot is solved. However, there is a problem that the brightness is lowered because the low luminance filter region is enlarged.

  The present invention has been made in view of the above problems, and a projection display device that realizes a display that achieves both high gradation and high luminance even when restricted by the lighting frequency of the lamp and the vertical synchronization frequency, and for use in the same. The purpose is to provide a color wheel.

In order to achieve this object, the color wheel of the present invention
In a color wheel in which a plurality of color filters that transmit light in a specific wavelength region are arranged in the circumferential direction,
A region in which at least one color filter having a different transmittance is included with respect to a pair of main color filters and a color filter having a different transmittance is added to the first main color filter region and a second main color filter. It is arranged so that the boundary line with the color filter region of the color is approximately 180 °, and the color filters having different transmittances are lower in transmittance than any of the primary color filters .

  As described above, according to the color wheel of the present invention and the projection display device using the color wheel, two sets of RGB regions which are main colors are provided in one color wheel, so that the color wheel can be rotated at high speed. Even without this, it is possible to suppress the color separation phenomenon unnecessary for display. Furthermore, high gradation display is possible by providing a low luminance filter region. However, when the number of color divisions of one color filter is increased in this way, an off period occurs due to color switching, and light utilization efficiency is reduced. The color wheel of the present invention can achieve both high gradation display and high brightness.

  In particular, in a projection display device, it is possible to achieve both high gradation display and high brightness by using the color wheel of the present invention when switching the frequency of an AC-lit lamp or switching the input signal for each frame.

  Further, in the projection display device of the present invention, high luminance can be realized by adjoining a low-luminance color filter and a normal color filter of the same wavelength band, and turning on without taking off period when switching colors.

  Embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited thereby.

(Embodiment 1)
A schematic diagram of a color wheel according to the first embodiment of the present invention is shown in FIG. The color wheel 1 has a configuration in which R, G, and B color filters are coated as an optical thin film on a single glass substrate. Each of the RGB color filters has a substantially fan shape, and R1, R2, G1, G2, B1, and B2 are arranged in the circumferential direction, and a low luminance filter G3 is arranged between the color filter R1 and the color filter G1, and is divided into seven regions. Has been. Further, the boundary between the color filter R1 and the color filter B2 and the boundary between the color filter B1 and the color filter R2 are configured to be in a straight line. That is, the color filters are angularly distributed so that the sum of the central angles of the fan-shaped color filters R1, G3, G1, and B1 is 180 °. In these color filters R1, R2, G1, G2, B1, and B2, the transmitted white light is modulated into R, G, and B light, respectively, and a constant value of 10800 rpm is obtained by a motor or the like so that RGB is switched six times in one field. It is displayed sequentially by rotating at speed.

  Further, FIG. 2 shows a projection display device using the color wheel of FIG. In FIG. 2, 21 is a color wheel, R1, R2, G1, G2, G3, B1, and B2 are color filters, 22 is a field lens, 23 is an integrator, 24 is a lamp including a concave mirror, 25 is a relay lens system, and 26 is a reflection lens. A mirror, 27 is a DMD element, 28 is a projection lens, and 29 is a screen. The DMD element 27 is one of the spatial light modulation elements. One micromirror corresponds to one pixel, and this is arranged in a matrix, and the mirror tilt changes at high speed according to the video signal, and the display is switched. Is possible. In order to display a video rate moving image, it is necessary to be able to display 60 frames of video in one field. For example, the DMD element may be a liquid crystal panel capable of high-speed response. For this purpose, the response speed of the liquid crystal is at least 1/60 = 16.7 msec or less, and preferably, in order to display RGB three colors during this period, the response speed is required to be 5.6 msec or less. Examples of such a fast response liquid crystal include a ferroelectric liquid crystal, an antiferroelectric liquid crystal, and an OCB (Optically Compensated Bend) liquid crystal.

  The operation of the projection display device of the present invention will be described. The lamp 24 is a discharge type high-power lamp such as a metal halide lamp or an ultra-high pressure mercury lamp. The lamp 24 is disposed almost at the focal position of the concave mirror, and the white light emitted from the lamp 24 is placed on the color filter of the color wheel 21 by the elliptical concave mirror. It arrange | positions so that it may condense to. The color wheel 21 is configured such that R, G, and B color filters are arranged in a disk shape, and the white light emitted from the lamp 24 is separated into light having a predetermined wavelength by passing through the respective color filters. . Color rays in a specific wavelength band are made uniform by the integrator 23 and illuminate the DMD element 27 through the relay lens system 25. The DMD element 27 displays an image frame corresponding to the color in synchronization with the irradiated color beam. The color wheel 21 is rotated by a motor (not shown) at 3 revolutions per image frame or 10800 revolutions per minute (rpm) for a single image frame, usually 1/60 second. In such a system, there are six color sub-frames between one frame frequency, each of which is red, green and blue, and the DMD element 27 switches the display image very quickly for each color. The modulated light beams are enlarged and projected onto the screen 29 using the projection lens 28. In the display projected on the screen, images of each color of R, G, and B are sequentially displayed within 1/60 seconds, so that these appear as afterimages to the eyes and a full-color image is recognized.

  Since the DMD element 27 is a digital modulation element that performs display by switching on / off of a mirror, a gray scale display uses a drive system called PWM. In other words, the gradation is displayed with the accumulated time during which the mirror is on, and generally the time determined for each bit represented by a power of 2 is turned on. The color display method of DMD will be described in detail by taking red display as an example. In the projection display apparatus of the present invention, the red subframe appears six times in one frame frequency period. However, since other colors such as green and blue also appear in time series, in this case, they appear intermittently six times instead of continuously. Since the PWM 8-bit gradation display of DMD is performed in the entire six subframe periods, the MSB and large bits are divided and displayed in a plurality of subframes. The LSB is determined depending on the response speed of the mirror, and since it cannot be divided below this, display is performed in one of six subframes. The same applies to the blue display.

  Unlike the other red and blue colors, the green display has a low luminance filter G3, so that 10-bit gradation display is possible. In the projection display apparatus of the present invention, the normal green sub-frame formed by the light beam transmitted through the color filters G1 and G2 in one frame frequency period is formed six times and the low-brightness green sub frame formed by the light beam transmitted through the low-luminance filter G3. The frame appears 3 times. Of these, the normal green sub-frame performs 8-bit gradation display in the same manner as the red display described above, and therefore the description thereof is omitted here. Since the low luminance filter G3 has a transmittance of 1/4 of the normal filters G1 and G2, when the DMD displays with LSB, the light beam that has passed through the low luminance filter can be displayed with high resolution of 2 bits. Low-brightness green subframe appears three times in one frame, but DMD displays LSB in each frame, one of which becomes 1 bit (LSB) as it is, and the remaining 2 times become 2 bits in total. . In the normal green subframe, the DMD displays 3 bits when performing LSB display, and the MSB uses 10 bits as it is. In this way, 10-bit gradation display is possible.

  A motor is used to rotate the color wheel 21 as in the present invention at a high speed. As the motor, a ball bearing type DC brushless motor is generally used. However, when a higher rotational speed is required, a fluid bearing motor such as oil or air may be used. Each of the color wheels 21 has a structure in which color filters having predetermined optical characteristics of RGB are cut into a fan shape having a pre-distributed center angle, and are fixed to a circular hub with an adhesive or the like in a predetermined color order. The center of the circular hub is fixed to the rotor portion of the motor and rotated. On the other hand, the other color wheel is composed of a doughnut-shaped glass substrate by a selective vapor deposition method, so it is light and has little risk of splashing. Also good. Of course, the color wheel 21 joined to the rotor portion also rotates together.

  At this time, the color of the color band formed by the color wheel 21 and the image displayed by the DMD element 27 must be synchronized. It is assumed that the signal interface can accept various types of input signals, for example here a standard video signal with horizontal and vertical sync components. As will be described below, the vertical synchronization signal is used as a reference signal for adjusting the speed of the color wheel 21. The input signal may be graphics data such as a PC, and the reference signal may come from another signal source.

  However, in the present invention, the number of times of color switching between one frame, the order of appearance of colors, and the angle distribution of color filters are not particularly limited, and the same applies to the following embodiments.

(Embodiment 2)
A projection display device of the present invention is shown in FIG. In FIG. 3, 31 is the color wheel described in the first embodiment, R1, R2, G1, G2, G3, B1, B2 are color filters, 32 is a field lens, 33 is an integrator, 34 is a lamp including a concave mirror, 35 Is a relay lens system, 36 is a reflecting mirror, 37 is a DMD element, 38 is a projection lens, and 39 is a screen. Light incident on the DMD element 37 is sent through the rotating color wheel 31. The data for each color is sequenced, and the display of the data is synchronized so that the portion of the color wheel 31 that is passing the light being sent to the DMD element 37 corresponds to the displayed data. I'm damned. In the example of this description, each pixel is represented by an RGB data value, which means that each pixel has a red value, a green value, and a blue value. As the values for each color of all the pixels in the frame are being displayed, the color wheel 31 rotates so that the light passes through the corresponding red, blue, or green filter. The combination of these three values yields the desired color for each pixel.

  The operation of the projection display device of the present invention will be described. Since the basic operation is the same as that described in the first embodiment of the present invention, it will be omitted and only different parts will be described. The white light beam emitted from the lamp 34 is condensed on the color filter of the color wheel 31 by the concave mirror, but since the light emitter of the lamp has a finite size, the light source image formed on the color filter also has a finite size. Therefore, when the light source image crosses the boundary between different color filters, there is a period (hereinafter referred to as “spoke time”) in which light passes through the two color filters at the same time, and the two colors are mixed during this period. Since a high-quality display cannot be obtained with a single color, the DMD element 37 is forcibly turned off.

  The color wheel 31 is rotationally driven by a motor 40, and the phase and rotational speed of the motor 40 are controlled by a color wheel control circuit 42. The color wheel control circuit 42 receives the color wheel phase signal 48 from the color wheel 31, and controls the color wheel 31 with the motor control signal 49 in phase comparison with the color wheel control signal 47 received from the driver circuit 43 of the DMD element 37. On the other hand, the DMD element 37 for displaying an image receives an input signal 44 through a signal interface, and converts it into a signal format corresponding to the time-division driving of the DMD element 37 through a driver circuit 43. Further, this data is stored in the display memory, and data 45 is output to the DMD element 37 at a predetermined timing.

  At this time, the lamp 34 emits light by AC lighting driving by a signal from the lamp power supply 41. The lamp 34 is driven by the lamp driving signal 50 by the lamp phase signal 46 sent from the driver circuit 43 to the lamp power supply 41. FIG. 4 shows a timing chart of the lamp driving current waveform, the output light intensity, and the color sequence of the color wheel. As shown in FIG. 4, when a drive current waveform is applied to the lamp at a constant period of 180 Hz, a transient phenomenon occurs due to the switching of the polarity of the pulse, and the light output intensity temporarily increases. Although this phenomenon is called lamp overshoot, the light beam generated by the overshoot has a different intensity from the light beam in the steady state, and the linearity is lost when used for display. Therefore, the display is turned off by synchronizing the overshoot occurrence timing with the spoke time of the color wheel, so that the influence of overshoot can be minimized. Specifically, at the boundary between the color filter R1 and the color filter B2 of the rotating color wheel 31 and the boundary between the color filter B1 and the color filter R2, the timing at which the light beam crosses and the timing for switching the AC lighting frequency of the lamp 34 are synchronized. . In this way, overshoot generated in the lamp 34 can be brought to the spoke time between the color filter R1 and the color filter B2 and the spoke time period between the color filter B1 and the color filter R2, and the DMD element 37 is turned off. Since this is a display, a highly uniform display can be realized without being affected by overshoot.

(Embodiment 3)
A schematic diagram of a color wheel according to a third embodiment of the present invention is shown in FIG. In FIG. 5, each of the RGB color filters is substantially fan-shaped, and R1, R2, G1, G2, B1, B2 are arranged in the circumferential direction, and a low-intensity filter G3 is arranged between the color filter R1 and the color filter G1. It is divided into areas. Further, the boundary between the color filter R1 and the color filter B2 and the boundary between the color filter B1 and the color filter R2 are configured to be in a straight line. That is, the color filters are angularly distributed so that the sum of the central angles of the fan-shaped color filters R1, G3, G1, and B1 is 180 °. As a detailed angle distribution, the center angle of the color filters R1 and R2 is 65 °, the color filters B1 and B2 are 60 °, the color filter G1 is 40 °, the G2 is 55 °, and the G3 is 15 °. The optimum angle is determined by the spectral transmittance characteristics of the entire optical system including the optical system, and the present invention does not depend on this angle.

  The sequence can be started from either the boundary between the color filter R1 and the color filter B2 or the boundary between the color filter B1 and the color filter R2 by equally dividing the filter area of the same color as in the color wheel of the present invention. This is possible by driving substantially the same DMD element. Further, by adopting the color filter configuration as in the present invention, since the same DMD drive sequence can be obtained in each sub-frame of the same color, it is possible to reduce the moving image pseudo contour.

(Embodiment 4)
FIG. 6 shows a schematic diagram of a projection display apparatus according to the fourth embodiment of the present invention. In FIG. 6, 61 is the color wheel shown in FIG. 5, R1, R2, G1, G2, G3, B1, and B2 are color filters, 62 is a field lens, 63 is an integrator, 64 is a lamp including a concave mirror, and 65 is a relay lens. System 66 is a reflecting mirror, 67 is a DMD element, 68 is a projection lens, and 69 is a screen.

  The operation of the projection display device of the present invention will be described. Since the basic operation is the same as that described in the first embodiment of the present invention, it will be omitted and only different parts will be described. When the vertical synchronizing signal frequency of the input signal 74 is 60 Hz, the projection display device of the present invention is composed of six subframes for each color in the same frame frequency period as in the first embodiment, and the DMD element 67 is correspondingly provided. Display. On the other hand, when the vertical synchronizing signal frequency of the input signal 74 is 50 Hz, it is necessary to change the number of rotations of the color wheel 61 from 10800 rpm to 9000 rpm when trying to configure the subframes of six colors in one frame frequency period as described above. is there. In areas where NTSC signals and PAL signals are mixed, it is necessary to change the rotation speed of the color wheel 61 each time, and there is a delay of several seconds until the rotation speed becomes constant. There was a disturbing issue.

  In the present invention, in view of such problems, the color wheel control signal 77 from the driver circuit 73 controls the rotation speed of the color wheel 61 at a constant 9000 rpm regardless of whether the vertical synchronization frequency of the input signal 74 is 60 Hz or 50 Hz. At the same time, when the vertical synchronizing signal frequency of the input signal 74 is 50 Hz, the drive signal 75 of the DMD element 67 is changed from the driver circuit 73 so as to be composed of six subframes for each color in one frame frequency period, and the vertical of the input signal 74 is changed. When the synchronization signal frequency is 60 Hz, improvement can be achieved by changing the drive signal 75 of the DMD element 67 so that it is composed of five subframes for each color in one frame frequency period.

  The color wheel 61 is rotationally driven by a motor 70, and the phase and rotation speed of the motor 70 are controlled by a color wheel control circuit 72. The color wheel control circuit 72 receives the color wheel phase signal 78 from the color wheel 61, and controls the color wheel 61 with the motor control signal 79 in phase comparison with the color wheel control signal 77 received from the driver circuit 73 of the DMD element 67. When the vertical synchronizing signal frequency is 50 Hz, even subframes are used. Therefore, when there are two pairs of color filters in the color wheel 61 as in the present invention, frame synchronization can be obtained at the same position as described above. . On the other hand, since the sub-frame is an odd number at 60 Hz, if the frame synchronization is taken when the light source image comes to the boundary position between the color filter R1 and the color filter B2 of the color wheel 61 as shown in FIG. Must be taken at a position 180 ° opposite the position. In the color wheel of the present invention, it can be taken at the boundary position between the color filter B1 and the color filter R2.

  When displaying in odd-numbered subfields, the color wheel 61 of the present invention differs in the number of times the low luminance filter G3 appears in odd-numbered fields and even-numbered fields. Specifically, when the RGB color sequence appears five times in one frame, the low luminance filter region G3 appears three times in the odd frame, but the low luminance filter region G3 appears only twice in the even frame. FIG. 7 schematically shows the ON time of the DMD element in the low luminance filter G3. The horizontal axis is a time axis, and 1x to 5x indicate the number of appearances of a color sequence having RGB as a basic unit. As shown in FIG. 7, the DMD element 67 is driven by changing the PWM sequence between the odd field and the even field. In the odd field, the green subframe of the low luminance filter appears three times. In each subframe, the DMD element 67 turns on the mirror at LSB (unit time t). One of them is bit 0, but the other two display bit 1 together. On the other hand, the low-intensity green subframe appears twice in the even field, but in one subframe, the DMD element 67 turns on the mirror at LSB and displays bit 0, but in the other subframe, doubles the LSB. The mirror is turned on at the time of and the bit 1 is displayed.

(Embodiment 5)
A projection display apparatus according to the fifth embodiment of the present invention will be described. The schematic diagram is the same as the projection display device shown in FIG.

  The operation of the projection display device of the present invention will be described. Since the basic operation is the same as that described in the first embodiment of the present invention, it will be omitted and only different parts will be described. FIG. 8 schematically shows a driving pattern of the DMD element when the color wheel color is switched in the projection display apparatus of the present invention. The color wheel of the present invention has a low luminance color filter G3, and an area is formed adjacent to the normal color filter G1 of the same color. A spoke time is provided when the light source image crosses the boundary between filters of different colors, and the DMD element 27 is forcibly turned off to prevent color mixing. However, the projection display apparatus of the present invention uses a low-luminance color filter. G3 and the same color filter G1 are arranged so as to be adjacent to each other, and the mirror is turned on as an effective display period of the DMD element without providing a spoke time therebetween. However, since the low-luminance color filter G3 is ¼ of the transmittance of the color filter G1, the spoke time period is the transmittance during that time, so it is necessary to adjust the bit width, that is, the mirror ON time. In the low luminance color filter G3, bit 0 which is LSB is displayed, in the transition period during which the low luminance color filter G3 switches to the color filter G1, bit 3 is displayed, and after complete switching to the color filter G1, bit 4 is displayed. The purpose of the present invention is to effectively use the spoke time, which is a transition period for switching from filter to filter, and it does not matter what weighting bits are arranged.

(Embodiment 6)
A schematic diagram of a color wheel according to a sixth embodiment of the present invention is shown in FIG. In FIG. 9, each of the RGB color filters has a substantially sector shape, and R1, R2, G1, G2, B1, and B2 are arranged in the circumferential direction, and a white segment W1 is arranged between the color filter R1 and the color filter G1. It is divided into Further, the boundary between the color filter R1 and the color filter B2 and the boundary between the color filter B1 and the color filter R2 are configured to be in a straight line. That is, the color filters are angularly distributed so that the sum of the central angles of the sector color filters R1, W1, G1, and B1 is 180 °. As a detailed angle distribution, the center angle of the color filters R1 and R2 is 65 °, the color filters B1 and B2 are 60 °, the color filter G1 is 40 °, G2 is 55 °, and the white segment W1 is 15 °. The optimum angle is determined by the spectral transmittance characteristics of the entire optical system including the lamp, and the present invention does not depend on this angle.

  The white segment W1 is made of a glass substrate having a high transmittance, but has an antireflection coating on the light transmission surface. Alternatively, a selective reflection coat that reflects light in an unnecessary wavelength band may be used. The white segment is used for the purpose of increasing the brightness of the white area of the display.

  The sequence can be started from either the boundary between the color filter R1 and the color filter B2 or the boundary between the color filter B1 and the color filter R2 by equally dividing the filter area of the same color as in the color wheel of the present invention. This is possible by driving substantially the same DMD element. Further, by adopting the color filter configuration as in the present invention, since the same DMD drive sequence can be obtained in each sub-frame of the same color, it is possible to reduce the moving image pseudo contour.

(Embodiment 7)
A schematic diagram of a color wheel according to a seventh embodiment of the present invention is shown in FIG. In FIG. 10, each of the RGB color filters is substantially fan-shaped and has R1, R2, G1, G2, B1, and B2 in the circumferential direction, and a low luminance color filter G3 between the color filter R1 and the color filter G1, and a color filter R2. The low-luminance color filter R3 is disposed between the color filter G2 and the color filter G2, and is divided into eight regions. Further, the boundary between the color filter R1 and the color filter B2 and the boundary between the color filter B3 and the color filter R2 are configured to be in a straight line. That is, the color filters are angularly distributed so that the sum of the central angles of the sector color filters R1, W1, G1, and B1 is 180 °.

  In the present invention, a projection display using a projection lens is described as an example of a color sequential display device. However, a direct-view color sequential display device using an eyepiece instead of the projection lens may be used.

  The color wheel and the projection display apparatus using the color wheel according to the present invention are useful as a projector or a projection television that achieves both high luminance and high gradation performance.

Schematic explaining 1st Embodiment in the color wheel of this invention Schematic explaining the first embodiment of the projection display device of the present invention Schematic explaining 2nd Embodiment in the projection type display apparatus of this invention. Schematic showing timing chart of lamp drive voltage waveform, output light intensity and color wheel color sequence Schematic explaining 3rd Embodiment in the color wheel of this invention. Schematic explaining the fourth embodiment of the projection display device of the present invention Schematic explaining the DMD drive sequence in the projection display apparatus of the present invention Schematic diagram for explaining the driving pattern of the DMD element at the time of color wheel color switching in the projection display device of the present invention. Schematic explaining 6th Embodiment in the color wheel of this invention. Schematic explaining 7th Embodiment in the color wheel of this invention Schematic explaining a conventional projection display device Schematic explaining the conventional color wheel Another schematic diagram illustrating a conventional color wheel Another schematic diagram illustrating a conventional color wheel

Explanation of symbols

1,21 Color wheel R1, R2, R3, G1, G2, G3, B1, B2 Color filter 23 Integrator 24 Lamp 25 Relay lens system 26 Reflector 27 DMD element 28 Projection lens 29 Screen

Claims (1)

In a color wheel in which a plurality of color filters that transmit light in a specific wavelength region are arranged in the circumferential direction,
A region in which at least one color filter having a different transmittance is included with respect to a pair of main color filters and a color filter having a different transmittance is added to the first main color filter region and a second main color filter. A color wheel that is arranged so that a boundary line with a color filter region of a color is approximately 180 °, and the color filters having different transmittances are lower in transmittance than any of the primary color filters. .

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