JP2008225031A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector capable of preventing color unevenness of a projection image and reduction of a quantity of projection light. <P>SOLUTION: The projector includes: a variable transmission filter which is disposed in the middle of an optical path extending from a light source to at least any of a light modulating devices 61R, 61G, or 61B and which has a total transmission area where incident luminous flux is totally transmitted and a color filter area where luminous flux of a specific wavelength is cut; an image information analyzing means 13 that analyzes input image information; and a filter drive control means 14 that controls the drive of the variable transmission filter on the basis of an analysis result obtained by the image information analyzing means 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a light source, a color separation optical device that separates a light beam emitted from the light source into a plurality of color lights, and modulates each color light separated by the color separation optical system in accordance with input image information. The present invention relates to a projector including a plurality of light modulation devices that form an optical image.

Conventionally, the illumination light flux of a white light source is separated into RGB three-color light by a dichroic mirror, each color light is projected onto a light modulation device such as a liquid crystal panel, and the light-modulated light is synthesized by a dichroic prism and projected. A three-plate projector is known.
Here, it is difficult to completely collimate the light beam emitted from the light source in the optical path leading to the light modulation device, and the dichroic mirror has a feature that the spectral characteristic changes depending on the incident angle of light. Unevenness may occur. In particular, when a white image or a light color image is projected, such color unevenness tends to be conspicuous.

  As a countermeasure when color unevenness occurs in the projected image, a color filter is inserted in the optical path between the light source and the light modulation device, and the wavelength band of each color light separated into RGB is narrowed, thereby making a difference in incident angle. There has been proposed a method of reducing the influence of the spectral characteristics due to (see, for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 9-160017 JP-A-3-103842

  However, in the technique disclosed in the above-mentioned patent document, each color light of RGB is simply narrowed by a color filter, so that the light amount is cut and the illuminance of the projected image is reduced. For example, unevenness is not conspicuous and filtering is not required. For example, even in a dark image or an image with a high spatial frequency, the amount of light is cut, resulting in a problem that the amount of projected light is reduced.

  The objective of this invention is providing the projector which can prevent generation | occurrence | production of the color nonuniformity of a projection image, and can prevent a projection light quantity reducing.

The projector according to the present invention includes a light source, a color separation optical device that separates a light beam emitted from the light source into a plurality of color lights, and each color light separated by the color separation optical device in accordance with input image information. A projector including a plurality of light modulation devices that modulate and form an optical image,
A variable transmission filter that is disposed in the middle of an optical path from the light source to at least one of the light modulation devices, and has a total transmission region that totally transmits an incident light beam, and a color filter region that cuts a light beam of a specific wavelength;
Image information analysis means for analyzing the input image information;
Filter drive control means for controlling drive of the variable transmission filter based on the analysis result analyzed by the image information analysis means.

Here, the analysis of the image information by the image information analysis means may be performed by preliminarily supporting the brightness and the spatial frequency in frame units in the image information as metadata, and acquiring this by the image information analysis means. The image information stored in the frame buffer or the like may be directly analyzed.
According to the present invention, the input image information is analyzed by the image information analysis means, and the filter drive control means performs drive control of the variable transmission filter based on the analysis result. In the case of a clear image, it is possible to perform filtering by the color filter area, and in the case of an inconspicuous image, it is possible to perform control so that the total transmission is performed. It is possible to prevent unevenness from being noticeable and to reduce the amount of projected light.

In the present invention, the image information analysis means includes a brightness information acquisition unit that acquires brightness information of the input image information,
The filter drive control means includes a use filter determination unit that determines whether to use the total transmission region or the color filter region of the variable transmission filter based on the brightness information acquired by the brightness information acquisition unit. It is preferable to provide.

Here, the brightness information can be acquired by acquiring the gradation value of each pixel in the image information in units of frames, and the use of the filter is determined by making the acquired gradation value a histogram. This can be done by determining whether the image is bright or dark.
According to this invention, since the brightness information acquisition unit acquires the brightness information of the image information, the use filter determination unit, for example, in the case of a relatively dark image, color unevenness is not noticeable. It is possible to determine that filtering is not performed in a region, and filtering is performed in a color filter region in the case of a bright image with high brightness.

In the present invention, the image information analysis means includes a spatial frequency analysis unit that performs spatial frequency analysis of input image information,
The use filter determination unit
Furthermore, it is preferable to determine whether to use the total transmission region or the color filter region of the variable transmission filter based on the analysis result of the spatial frequency analysis unit.

Here, for the spatial frequency analysis, various methods used for image analysis can be employed, and for example, analysis using fast Fourier transform (FFT), discrete cosine transform (DCT), or the like can be employed. However, analysis using DCT is simple and preferable.
According to this invention, the spatial frequency analysis unit performs the spatial frequency analysis of the image information, and based on the analysis result, the use filter determination unit determines whether or not to perform filtering by the color filter region. In the case of an image with a low spatial frequency such as a snowy scene or a blue sky scene, filtering by the color filter area is performed, and in the case of an image having a high spatial frequency such as a tree scene, color unevenness is observed. Since it is not conspicuous, it can be determined that the filter by the color filter region is not performed.

In the present invention, the color separation optical device includes at least one dichroic mirror,
It is preferable that the variable transmission filter is disposed in front of the optical path of the dichroic mirror, and the color filter region of the variable transmission filter is a filter that cuts a wavelength near the half-value wavelength of the dichroic mirror.
According to the present invention, since the color filter region cuts the wavelength near the half-value wavelength of the dichroic mirror, even if the incident angle of the incident light beam changes and the spectral characteristics of the dichroic mirror change, the wavelength near the half-value wavelength Is cut, color separation can be performed reliably, and color unevenness can be reliably prevented.

In the present invention, the variable transmission filter is configured as a rotary filter in which a total transmission region and a color filter region are partitioned in a rotatable disc-shaped body,
In the color filter region of the variable transmission filter, it is preferable that at least one of the transmission wavelength and the transmittance changes continuously or stepwise in the circumferential direction.
According to the present invention, since the transmission wavelength and the transmittance are changed continuously or stepwise when changing from the use of the total transmission region to the color filter region, the color filter is changed from the total transmission region to the observer without a sense of incongruity. Transition to a region can be made.

In the present invention, color conversion information storage means for storing color conversion information corresponding to the transmission characteristics of the color filter region of the variable transmission filter,
Operation status acquisition means for acquiring the operation status of the variable transmission filter during projection;
Based on the obtained operating state of the variable transmission filter, the use area determination means for determining whether the color filter area of the variable transmission filter is used or the total transmission area is used;
Color conversion processing means for performing color conversion processing of input image information with reference to color conversion information stored in the color conversion information storage means when it is determined that a color filter area is used; It is preferable to provide.

  According to this invention, the operation status acquisition unit acquires the operation status of the variable transmission filter, the use area determination unit determines whether the total transmission area or the color filter area of the variable transmission filter is used, and the color Since the conversion processing means refers to the color conversion information stored in the color conversion information storage means and performs color conversion processing of the input image information, the input gradation value of the light cut by the color filter area is determined. By interpolating, it is possible to display an image with a small decrease in the amount of projected light.

In the present invention, it is preferable that a light amount adjustment control unit that adjusts a light amount of a light beam emitted from the light source based on a determination result of the use region determination unit is provided.
According to the present invention, since it is possible to adjust and control the light amount of the light source in addition to the input gradation value by the color conversion processing means, it is emitted from the light source when using the color filter region of the variable transmission filter. When the entire transmission area of the variable transmission filter is used, the light quantity of the light emitted from the light source is decreased, so that a uniform surface can be obtained regardless of the usage state of the variable transmission filter. A projected image of illuminance can be projected.

In the present invention, it is preferable to include filter operation control means for performing operation control of the variable transmission filter.
According to the present invention, the observer can determine whether the projection image is observed using the total transmission region of the variable transmission filter or the projection image is observed using the color filter region of the variable transmission filter. Since it can be selected according to preference, the projector can be easily used by an observer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
[1] Overall Configuration FIG. 1 shows an optical system of a projector 1 according to an embodiment of the present invention. The projector 1 modulates a light beam emitted from a light source device in accordance with image information to produce a color image (optical). Image), and this color image is enlarged and projected onto the screen Sc.
The projector 1 includes a light source device 2, a uniform illumination optical device 3, a color separation optical device 4, a relay optical device 5, an optical device 6, a color synthesis optical device 7, a projection optical device 8, and a variable transmission filter 9. Is done.
The light source device 2 includes a light source lamp 21 and a parabolic reflector 22 each formed of a discharge arc tube, and a radial light beam emitted from the light source lamp 21 is reflected and collimated by the parabolic reflector 22 and emitted to the uniform illumination optical device 3. Is done.

The uniform illumination optical device 3 is an optical system that divides the light beam emitted from the light source device 2 into a plurality of partial light beams and illuminates an image forming region of a liquid crystal panel, which will be described later, substantially uniformly. The first lens array 31, a second lens array 32, a polarization conversion element 33, and a superimposing lens 34.
The first lens array 31 has a configuration in which first small lenses having a substantially rectangular outline when viewed from the incident optical axis direction are arranged in a matrix in a plane substantially orthogonal to the incident optical axis. . Each first small lens splits the light beam emitted from the light source device 2 into a plurality of partial light beams.
The second lens array 32 has substantially the same configuration as the first lens array 31, and has a configuration in which the second small lenses are arranged in a matrix. The second lens array 32 has a function of forming, together with the superimposing lens 34, a light source image of each first small lens of the first lens array 31 on a liquid crystal panel described later.

The polarization conversion element 33 is disposed between the second lens array 32 and the superimposing lens 34, and converts light from the second lens array 32 into substantially one type of polarized light.
Specifically, each partial light converted into approximately one type of polarized light by the polarization conversion element 33 is finally substantially superimposed on a liquid crystal panel (to be described later) by the superimposing lens 34. In the projector 1 using a liquid crystal panel of a type that modulates polarized light, only one type of polarized light can be used, and therefore approximately half of the light from the light source device 2 that emits randomly polarized light cannot be used. For this reason, by using the polarization conversion element 33, the light emitted from the light source device 2 is converted into approximately one type of polarized light, and the use efficiency of light in a liquid crystal panel described later is enhanced.

The color separation optical device 4 includes two dichroic mirrors 41 and 42 and a reflection mirror 43, and a plurality of partial light beams emitted from the uniform illumination optical device 3 by the dichroic mirrors 41 and 42 are converted into red (R), It has a function of separating into three color lights of green (G) and blue (B).
The relay optical device 5 includes an incident side lens 51, a relay lens 53, and reflection mirrors 52 and 54, and the red light separated by the color separation optical device 4 is transferred to the red light liquid crystal panel and the liquid crystal shutter of the optical device 6. Has a guiding function.

At this time, the dichroic mirror 41 of the color separation optical device 4 reflects the blue light component of the light beam emitted from the uniform illumination optical device 3 and transmits the red light component and the green light component. The blue light reflected by the dichroic mirror 41 is reflected by the reflection mirror 43, passes through the field lens 44, and reaches a later-described liquid crystal panel for blue light of the optical device 6.
The field lens 44 converts each partial light beam emitted from the second lens array 32 into a light beam parallel to the central axis (principal light beam). The same applies to the field lens 44 provided on the light beam incident side of the other liquid crystal panel for green light and red light.

Of the red light and green light transmitted through the dichroic mirror 41, the green light is reflected by the dichroic mirror 42, passes through the field lens 44, and reaches a later-described green light liquid crystal panel of the optical device 6.
On the other hand, the red light passes through the dichroic mirror 42, passes through the relay optical device 5, passes through the field lens 44, and reaches a later-described red light liquid crystal panel of the optical device 6.
Note that the relay optical device 5 is used for red light because the optical path length of the red light is longer than the optical path lengths of the other color lights, thereby preventing a reduction in light use efficiency due to light divergence or the like. It is to do. That is, this is to transmit the partial light beam incident on the incident side lens 51 to the field lens 44 as it is.

The optical device 6 is a portion that modulates light according to each color light RGB separated by the color separation optical device 4 to form an optical image, and includes liquid crystal panels 61R, 61G, and 61B as light modulation devices. Composed.
The liquid crystal panels 61R, 61G, and 61B include an image forming area in which a plurality of pixels are arranged in a matrix, and perform gradation display according to image information input in each pixel.
Each of the liquid crystal panels 61R, 61G, and 61B includes a configuration in which liquid crystal is sealed between a pair of transparent substrates, and the liquid crystal is driven by a TFT (Thin Film Transistor) formed on one substrate. Although not shown, an incident side polarizing plate and an exit side polarizing plate are provided on the light emitting side, and the orientation of the liquid crystal is controlled by using the TFT as a switching element, and the light emitted from the emitting side polarizing plate is controlled. The gradation is displayed according to the image information by adjusting the amount.

The color synthesizing optical device 7 synthesizes each color light modulated for each color light emitted from the emission side polarizing plate of the liquid crystal panels 61R, 61G, 61B to form a color image. The color synthesizing optical device 7 has a substantially square shape in plan view in which four right-angle prisms are bonded together, and two dielectric multilayer films are formed on the interface where the right-angle prisms are bonded together. These dielectric multilayer films transmit the color light emitted from the liquid crystal panel 61G and reflect the color lights emitted from the liquid crystal panels 61R and 61B.
The projection optical device 8 is configured as a combined lens in which a plurality of lenses are housed in a cylindrical lens barrel, and a color image formed by the color synthesis optical device 7 is enlarged on the screen Sc by the projection optical device 8. Projected.

[2] Configuration of Variable Transmission Filter 9 The variable transmission filter 9 is disposed between the polarization conversion element 33 and the superimposing lens 34 that constitute the uniform illumination optical device 3, and includes a color filter plate 91 and filter driving means 92 such as a stepping motor. It is configured with. In the present embodiment, in addition to the variable transmission filter 9, light having a wavelength in the vicinity of the half-value wavelength of the green light G separated by the dichroic mirror 42 is disposed upstream of the optical path of the liquid crystal panel 61 G that modulates the green light G. A color filter 62 is provided for cutting the.

As shown in FIG. 2, the color filter plate 91 is formed of a disk-like body, and the rotation axis of the filter driving means 92 is connected to the disk center O.
The color filter plate 91 is divided into a total transmission region 911 and a color filter region 912 by substantially half of the disc, and is a circular plate larger than the illumination light path of the projector 1. When the color filter plate 91 is rotated by the filter driving unit 92, either the total transmission region 911 or the color filter region 912 is disposed in the optical path. In the initial state, the total transmission region 911 is disposed in the optical path.
As shown in FIG. 3A, the total transmission region 911 is a portion that transmits light in all wavelength regions, and the color filter region 912 has a certain wavelength region as shown in FIG. 3B. This is the part that cuts the light. The area cut by the color filter area 912 is set according to the spectral characteristics of the dichroic mirrors 41 and 42 described above.

The cut portion on the low wavelength side in FIG. 3B cuts light having a wavelength in the vicinity of the half-value wavelength of the dichroic mirror 41 that separates the blue light B, and specifically, has a wavelength in the vicinity of 500 nm. Cut the light. On the other hand, the cut portion on the high wavelength side in FIG. 3B cuts light having a wavelength near the half-value wavelength of the dichroic mirror 42 that separates the green light G and the red light R. Specifically, Cuts light with a wavelength around 580 nm.
By setting the wavelength to be cut in the color filter region 912 in this way, the light passing through the color filter region 912 has a difference in spectral characteristics depending on the incident angle to the dichroic mirrors 41 and 42. That is, even if the wavelength of the light to be dispersed changes depending on the incident angle, the light having such a wavelength is cut in the color filter region 912 in the first place, so that color unevenness does not occur on the projected image.

[3] Structure of Image Processing System As shown in FIG. 4, the structure of the image processing system of the projector 1 having the above-described structure is the image information input means 11, the image processing means 12, the image information analysis means 13, and the filter drive control. Means 14, filter operation control means 15, I / F signal input means 16, light amount adjustment control means 17, operation status acquisition means 18, and use area determination means 19 are configured.
The image information input unit 11 receives image information output from an image output unit such as an external PC. The image information input to the image information input unit 11 is output to the image processing unit 12. Input image information includes RGB data from a PC or the like, and digital image data such as MPEG or JPEG.

The image processing means 12 is a part that performs image processing according to the projector 1 on the input image information such as RGB data to form a projection image that secures appropriate color reproducibility. The input image information is The frame buffer 121 is stored in units of frames, and image processing is performed in units of frames.
Examples of the image processing performed by the image processing unit 12 include γ correction processing, color space conversion correction processing, VT-γ correction processing, ghost correction processing, and color unevenness correction processing. These correction processes are performed with reference to the parameter storage means 122 storing the LUT (Look Up Table) set in accordance with each correction process item. As will be described in detail later, the image processing unit 12 also functions as a color conversion processing unit that performs correction according to the operation state of the variable transmission filter 9 by the filter driving unit (stepping motor) 92.

The image information analysis unit 13 is a part that analyzes the image information input to the image processing unit 12, and includes a brightness information acquisition unit 131 and a spatial frequency analysis unit 132.
The brightness information acquisition unit 131 is a part that acquires brightness information in units of frames for input image information. Specifically, the brightness information (intensity) of each pixel of an image of one frame is subjected to histogram analysis. The brightness information is acquired.
For example, as shown in the histogram of FIG. 5A, since there are many high gradation pixels, it can be recognized as a bright image. On the other hand, as shown in the histogram of FIG. 5B, since there are many low gradation pixels, it can be recognized as a dark image. Note that the brightness information acquisition unit 131 acquires the brightness information of the entire screen, although it may be distributed discretely as shown in FIG.

The spatial frequency analysis unit 132 is a part that performs spatial frequency analysis of image information in units of frames. In this embodiment, spatial frequency analysis is performed by DCT.
For example, when performing spatial frequency analysis of two types of image data A1 and A2 as shown in FIG. 6A and FIG. 6B, in order to see a large tendency of spatial frequency, Smoothing processing is performed on the image data A1 and A2.
Next, each of the image data A1 and A2 is analyzed for each block image of 8 pixels × 8 pixels, and this is repeated for the entire image, and the average value of the DCT coefficients (8 × 8) of each block is calculated.

Then, as shown in the upper part of FIGS. 7A and 7B, the representative value of the DCT coefficient of each block is obtained, and when these are further normalized, the DCT coefficient as in the lower part is obtained.
In FIGS. 7A and 7B, the upper left of the normalized DCT coefficient represents a low frequency component, and becomes a high frequency component in the right direction and the downward direction.
Therefore, the spatial frequency analysis unit 132 acquires the lowermost four DCT coefficients and grasps how much high-frequency component the image data contains. For example, in the case of FIG. 7A, the lower right four matrix-like DCT coefficients are 1, and it is determined that the image data A1 is image data with a high spatial frequency. In the case of FIG. Since all the four matrix-like DCT coefficients are 0, it is determined that the image data A2 is image data with a low spatial frequency.

The filter drive control unit 14 is a part that performs drive control of the variable transmission filter 9 described above, and includes a use filter determination unit 141 and a filter drive control unit 142.
Based on the brightness information acquired by the brightness information acquisition unit 131 by the image information analysis unit 13 and the frequency analysis result analyzed by the spatial frequency analysis unit 132, the used filter determination unit 141 is based on the variable transmission filter 9. This is a part for determining which one of the total transmission area 911 and the color filter area 912 is used. Specifically, the use filter determination unit 141 determines which filter is to be used with reference to threshold values relating to brightness information and spatial frequency information stored in the parameter storage unit 122.

The filter drive control unit 142 outputs a control signal to the filter drive unit 92 based on the determination result of the use filter determination unit 141, thereby causing the total transmission region 911 and the color filter region 912 of the variable transmission filter 9 to be used. Switching control to either of the above is performed.
The filter operation control unit 15 controls the operation of the filter drive control unit 142 based on an operation signal input to the I / F signal input unit 16 by operating an operation panel (not shown) or a remote controller by an observer of the projector 1. It is a part to do. The operation control signal from the filter operation control means 15 sets a filter to be used in preference to the determination result of the use filter determination unit 141.

The light amount adjustment control unit 17 is a part that outputs a control signal to the light source driving unit 20 that drives the light source device 2 based on the analysis result of the image information analysis unit 13, and is acquired by the brightness information acquisition unit 131. If the brightness information is a bright image and the analysis result by the spatial frequency analysis unit 132 is determined to be an image having a low spatial frequency, the variable transmission filter 9 is switched to the color filter region 912 so that the color unevenness is not noticeable. Therefore, the light quantity of the light source device 2 is maintained at the highest luminance.
On the other hand, when it is determined that the image has a high spatial frequency, the image is originally an image in which the color unevenness is not conspicuous. Therefore, the variable transmission filter 9 may be switched to the total transmission region 911. In this case, the color filter region 912 Therefore, adjustment control for decreasing the light amount of the light source device 2 is performed, and control for projecting an image having the same light amount as that when the color filter region 912 is used is performed.

The operation status acquisition means 18 is a part for acquiring the current operation status of the variable transmission filter 9, specifically, a control signal output from the filter drive control unit 142 of the filter drive control means 14, specifically, The number of pulse steps to the filter driving unit 92 such as a stepping motor is monitored, and the acquired control signal is output to the use area determining unit 19.
Based on the control signal to the filter driving unit 92 acquired by the operation status acquisition unit 18, the use region determination unit 19 determines whether the current variable transmission filter 9 is used in the total transmission region 911 or the color filter region 912. This is a part for determining whether it is used, and the determination result is output to the image processing means 12.

  When the image processing unit 12 determines that the color filter region 912 is used from the operating state of the variable transmission filter 9 determined by the use region determining unit 19, the image processing unit 12 stores the parameter storage unit 122 in the parameter storage unit 122. A drive control signal is generated by referring to the LUT when the filter is stored, and is output to the driver ICs 161R, 161G, 161B to execute drive control of the liquid crystal panels 61R, 61G, 61B.

[4] Action and Effect of Projector 1 Next, the action of the projector 1 having the above-described structure will be described based on the flowchart shown in FIG.
First, when image information is input to the image information input means 11 (procedure S1), the input image information is stored in the frame buffer 121 in units of frames (procedure S2).
For the image in units of frames stored in the frame buffer 121, the brightness information acquisition unit 131 of the image information analysis unit 13 acquires the brightness information of the image (procedure S3), and the histogram analysis is performed (procedure S4). .

Based on the result of the histogram analysis, the used filter determination unit 141 of the filter drive control unit 14 determines whether the brightness of the image in units of frames is equal to or greater than a predetermined threshold (step S5), and the brightness of the image is predetermined. If it is determined that it is less than the threshold value, the image processing means 12 performs image processing in the normal projection state in the state of the total transmission region 911 without performing drive control of the variable transmission filter 9 (step S6), and the liquid crystal panel A drive image of 61R, 61G, and 61B is controlled to form a projection image, and steps S1 to S6 are repeated for the next frame image.
Image information.

On the other hand, when it is determined that the brightness of the image in units of frames is equal to or greater than the predetermined threshold, the spatial frequency analysis unit 132 performs a smoothing process on the image information by resolution conversion or the like to determine a large tendency of the spatial frequency. Is prepared (step S7). In order to more easily analyze the spatial frequency, the image may be subjected to monochrome processing as necessary, and the spatial frequency may be analyzed in a binary manner (step S8).
As described above, the spatial frequency analysis unit 132 performs spatial frequency analysis using DCT analysis, generates data by arranging DCT coefficients in a matrix, and among the generated matrix DCT coefficients, the lower right high frequency With reference to the DCT coefficient of the component, it is determined whether or not the image has a high spatial frequency (step S10).
If it is determined that the image has a high spatial frequency, the variable transmission filter 9 remains in the total transmission region 911. Therefore, the light amount adjustment control unit 17 performs adjustment control to reduce the light amount (step S11). In the same manner as described above, normal image processing by the image processing means 12 is performed to form a projection image (step S6).

  On the other hand, when it is determined that the spatial frequency is lower than the predetermined threshold and the image is a flat and light image, the use filter determination unit 141 instructs the filter drive control unit 142 to use the color filter region 912 of the variable transmission filter 9. The filter drive control unit 142 drives and controls the filter drive unit 92 based on the determination result of the use filter determination unit 141, and the state of the variable transmission filter 9 in the total transmission region 911 is changed to the color filter region 912. (Step S12).

The operation status acquisition unit 18 monitors the control signal output from the filter drive control unit 142, acquires the number of pulse steps (step S13), and the use area determination unit 19 determines the current pulse number from the obtained number of pulse steps. It is determined whether the variable transmission filter 9 uses the total transmission area 911 or the color filter area 912, and outputs to the image processing means 12 that the color filter area 912 is used (step S14).
When the use area determination unit 19 recognizes that the color filter area 912 of the variable transmission filter 9 is used, the image processing unit 12 refers to the LUT when the filtering stored in the parameter storage unit 122 is performed. Then, together with other correction processing items, the input image information is subjected to image processing in units of frames (step S15), and the processing of the next frame image is repeated.

According to such a projector 1, when the image of the input image information is not so bright or when it is determined that the image has a high spatial frequency, the image is projected using the total transmission region 911 of the variable transmission filter 9. By doing so, color unevenness due to the dichroic mirrors 41 and 42 is less likely to be visually recognized by an observer in an image that is not bright and an image with a high spatial frequency.
On the other hand, in the case of a bright image and an image having a low spatial frequency, the color unevenness caused by the dichroic mirrors 41 and 42 is easily noticeable. Therefore, the color unevenness is made inconspicuous by using the color filter region 912 of the variable transmission filter 9. In addition, by maintaining the light amount of the light source device 2 at the maximum luminance, the degree to which the light amount of the projected image is reduced by the color filter region 912 can be minimized.
In addition, when the total transmission region 911 is used in a bright and high spatial frequency image, the light amount adjustment control means 17 actively reduces the light amount, thereby projecting when the color filter region 912 is used. Since the change between the light amount of the image and the light amount of the projected image when the total transmission region 911 is used can be reduced, the observer does not feel uncomfortable by switching the variable transmission filter 9.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the following description, the same parts as those already described are denoted by the same reference numerals and the description thereof is omitted.
In the first embodiment described above, the variable transmission filter 9 is disposed between the polarization conversion element 33 and the superimposing lens 34 that constitute the illumination optical device 3, and the wavelength of about 500 nm and about 580 nm at the same time with one variable transmission filter 9. Was configured to cut the light.
On the other hand, in the projector 1A according to the present embodiment, as shown in FIG. 9, the variable transmission filter 9B is arranged at the downstream stage of the optical path after separation of the blue light B of the dichroic mirror 41, and the variable transmission filter 9R is dichroic. The difference is that the mirror 42 is arranged in the latter stage of the optical path after separation of the red light R.

In the first embodiment described above, the cut amount of light of each wavelength in the color filter region 912 is set to only one level.
On the other hand, the present embodiment is different in that the color filter regions 912, 931, 941, 932, and 942 are set to other levels in stages along the circumferential direction of the color filter plates 93 and 94. .
The variable transmission filter 9B includes a color filter region that cuts a wavelength near the half-value wavelength of the blue light B separated by the dichroic mirror 41, and a color filter plate 93 having a total transmission region. By rotating 93, the total transmission region and the color filter region are arranged in the optical path.

As shown in FIG. 10, the color filter plate 93 includes a total transmission region 911 and color filter regions 912, 931, and 932 having different transmittances. For example, in the color filter region 912, the color filter region 912 of FIG. As shown in the left filter 1B, all light in the vicinity of the half-value wavelength of the dichroic mirror 41 that separates the blue light B is absorbed.
In the color filter region 931, as shown in the blue light B, as shown in the filter 2B on the left side of FIG. 11C, the light near the half-value wavelength of the dichroic mirror 41 is absorbed by about 50%. In the color filter region 932, as shown by the filter 3B in FIG. 11D, the light near the half-value wavelength of the dichroic mirror 41 is absorbed by about 30%.

  The variable transmission filter 9R basically has the same configuration as the variable transmission filter 9B described above, and color filter regions 912, 941, and 942 are set stepwise in the circumferential direction of the color filter plate 94. In the color filter region 912, as shown in the filter 1R on the right side of FIG. 11B, all light near the half-value wavelength of the red light R is absorbed. In the color filter region 941, FIG. As shown in the filter 2R of C), the light near the half-value wavelength of the dichroic mirror is absorbed by about 50%, and the color filter region 942 absorbs about 30% as shown by the filter 3R in FIG. 11D. It has become.

Such image analysis and filter drive control in the projector 1A according to the present embodiment needs to be performed independently for each of the variable transmission filters 9R and 9B, but the variable transmission filter 9R based on brightness information and spatial frequency analysis. , 9B drive determination control is basically the same as in the first embodiment.
In the present embodiment, as in the case of the first embodiment, it is possible to perform the light amount adjustment control of the light source device 2 by the light amount adjustment control means, but in this case, the variable transmission filter 9R. It is preferable to adjust the light amount appropriately according to the transmittance in each of the color filter regions 912, 931, 941, 932, and 942 of the color filter plates 93 and 94 that constitute 9B.
According to the present embodiment, in addition to the effects of the above-described embodiments, the variable transmission filters 9R and 9B and the color filter that cuts the wavelength near the half-value wavelength of the green light G for each color light separated by the color separation optical device 4. Since 62 is provided, the projector 1A can be made less susceptible to the spectral characteristics of the dichroic mirrors 41 and 42.
Further, by appropriately adjusting the amount of light according to the transmittance of the color filter regions 912, 931, 941, 932, 942 of the color filter plate 93, it is possible to prevent the observer from feeling uncomfortable.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
In the projector 1A according to the second embodiment described above, the variable transmission filter 9R is disposed on the optical path of the red light R after being separated by the dichroic mirror 42.
On the other hand, the projector 1C according to the third embodiment is different in that a variable transmission filter 90R is disposed in the upstream of the optical path of the dichroic mirror 42 as shown in FIG. For this reason, the color filter for the green light G is not provided in the present embodiment before the liquid crystal panel 61G provided in the first and second embodiments.

In the color filter plates 93 and 94 of the variable transmission filters 9R and 9B according to the second embodiment described above, the color filter regions 912 and 931 are arranged in the circumferential direction so that the light transmittance of the color filter regions changes stepwise. , 941, 932, 942 are arranged.
On the other hand, the color filter plates 95 and 96 constituting the variable transmission filters 90R and 90B according to the present embodiment are arranged so that the dichroic mirrors 41 and 42 from the total transmission region 911 as shown in FIG. The difference is that intermediate filter regions 951 and 961 are provided between the color filter regions 912 that completely cut light having a wavelength near the half-value wavelength.

The intermediate filter regions 951 and 961 are configured such that the transmittance of light to be cut along the circumferential direction of the color filter plates 95 and 96 continuously changes. Specifically, the intermediate filter regions 951 and 961 are continuous from the transmittance 100% of the total transmission region 911 in FIG. 14A to the transmittance 0% of the color filter region 912 in FIG. 14C. Therefore, the transmittance is changed. That is, the intermediate filter regions 951 and 961 are configured such that the transmittance continuously decreases in the direction of the arrow in FIG.
In FIG. 13A, the total transmission region 911 and the color filter region 912 are arranged opposite to each other on the color filter plates 95 and 96, but not limited to this, as shown in FIG. 13B. The total transmission region 911 and the color filter region 912 may be disposed adjacent to each other, and the intermediate filter regions 951 and 961 may be disposed therebetween.
In this case, since it is possible to secure a large area for the intermediate filter areas 951 and 961, the rate of change in transmittance in the circumferential direction can be reduced.

  According to the present embodiment, in addition to the operations and effects of the above-described embodiment, the transmittance continuously changes in the intermediate filter regions 951 and 961, in other words, light having a wavelength near the half-value wavelength of the dichroic mirrors 41 and 42. Since the cut rate at the time of cutting the color changes continuously, the transition from the total transmission region 911 to the color filter region 912 can be performed seamlessly, so that the observer can recognize the state of the change. The sex becomes lower. In particular, in the case of FIG. 13B, the transition can be made using the long intermediate filter regions 951 and 961, so that it is more difficult for the observer to recognize.

[Modification of Embodiment]
It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the first embodiment described above, the variable transmission filter 9 is formed by forming the total transmission region 911 and the color filter region 912 on the disc-shaped color filter plate 91 and rotating them by the filter driving means 92 such as a stepping motor. However, the present invention is not limited to this. That is, the switching may be performed by linearly sliding a filter in which the total transmission region and the color filter region are arranged in parallel in a direction orthogonal to the illumination optical axis of the projector using a solenoid or the like.

In the first embodiment, the spatial frequency analysis is performed using DCT. However, the present invention is not limited to this, and the spatial frequency analysis may be performed by other methods such as FFT.
In the first embodiment, when the image information is input, the image stored in the frame buffer 121 is sequentially analyzed by the image information analyzing unit 13. However, the present invention is not limited to this, and an image such as MPEG or JPEG is used. Image information may be analyzed using metadata attached to the information.
In addition, the specific structure, shape, and the like in the implementation of the present invention may be other structures as long as the object of the present invention can be achieved.

1 is a schematic diagram showing the structure of an optical system of a projector according to a first embodiment of the invention. The front schematic diagram showing the structure of the variable transmission filter in the said embodiment. The graph showing the state of the transmittance | permeability in the total transmission area | region of the variable transmission filter in the said embodiment, and a color filter area | region. The block diagram showing the image processing system of the projector in the said embodiment. The graph for demonstrating acquisition of the brightness information by the image information analysis means in the said embodiment. The figure showing the image for demonstrating the spatial frequency analysis by the image information analysis means in the said embodiment. The schematic diagram showing the spatial frequency analysis result in the said embodiment. The flowchart for demonstrating the effect | action in the said embodiment. The schematic diagram showing the structure of the optical system of the projector which concerns on 2nd Embodiment of this invention. The front schematic diagram showing the structure of the variable transmission filter in the said embodiment. The graph showing the state of the transmittance | permeability in the total transmission area | region of the variable transmission filter in the said embodiment, and a color filter area | region. The schematic diagram showing the structure of the optical system of the projector which concerns on 3rd Embodiment of this invention. The front schematic diagram showing the structure of the variable transmission filter in the said embodiment. Total transmission region and color filter region of variable transmission filter in the embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A, 1C ... Projector, 2 ... Light source device, 3 ... Uniform illumination optical device, 4 ... Color separation optical device, 5 ... Relay optical device, 6 ... Optical device, 7 ... Color composition optical device, 8 ... Projection optical device , 9, 9B, 9R, 90B, 90R ... variable transmission filter, 11 ... image information input means, 12 ... image processing means, 13 ... image information analysis means, 14 ... filter drive control means, 15 ... filter operation control means, 16 DESCRIPTION OF SYMBOLS ... I / F signal input means, 17 ... Light quantity adjustment control means, 18 ... Operation condition acquisition means, 19 ... Use area determination means, 20 ... Light source drive means, 21 ... Light source lamp, 22 ... Parabolic reflector, 31 ... First lens Array 32. Second lens array 33 Polarization conversion element 34 Superimposing lens 41 Dichroic mirror 42 Dichroic mirror 43 Reflecting mirror 44 Fee , 51 ... incident side lens, 52 ... reflection mirror, 53 ... relay lens, 61R, 61G, 61B ... liquid crystal panel, 62 ... color filter, 91, 93, 94, 95, 96 ... color filter plate, 92 ... filter drive Means 121, frame buffer 122, parameter storage means 131, brightness information acquisition unit 132, spatial frequency analysis unit 141, used filter determination unit 142, filter drive control unit 161R, 161G, 161B, driver IC , 911: Total transmission region, 912, 931, 932, 941, 942 ... Color filter region, 951 ... Intermediate filter region, A1 ... Image data, A2 ... Image data, B ... Blue light, G ... Green light, R ... Red Light, O ... disc center, Sc ... screen

Claims (8)

A light source, a color separation optical device that separates a light beam emitted from the light source into a plurality of color lights, and each color light separated by the color separation optical device is modulated in accordance with input image information to form an optical image. A projector having a plurality of light modulation devices to be formed;
A variable transmission filter that is disposed in the middle of an optical path from the light source to at least one of the light modulation devices, and has a total transmission region that totally transmits an incident light beam, and a color filter region that cuts a light beam of a specific wavelength;
Image information analysis means for analyzing the input image information;
A projector comprising: filter drive control means for performing drive control of the variable transmission filter based on the analysis result analyzed by the image information analysis means. The projector according to claim 1, wherein
The image information analyzing means includes
A brightness information acquisition unit that acquires brightness information of input image information is provided,
The filter drive control means includes
And a use filter determination unit that determines whether to use a total transmission region or a color filter region of the variable transmission filter based on the brightness information acquired by the brightness information acquisition unit. Projector. The projector according to claim 2,
The image information analyzing means includes
It has a spatial frequency analysis unit that performs spatial frequency analysis of input image information,
The use filter determination unit
Furthermore, it is determined whether to use the total transmission region or the color filter region of the variable transmission filter based on the analysis result of the spatial frequency analysis unit. The projector according to any one of claims 1 to 3,
The color separation optical device includes at least one dichroic mirror,
The variable transmission filter is disposed in a stage preceding the optical path of the dichroic mirror, and the color filter region of the variable transmission filter is a filter that cuts a wavelength in the vicinity of a half-value wavelength of the dichroic mirror. The projector according to any one of claims 1 to 4,
The variable transmission filter is configured as a rotary filter in which a total transmission region and a color filter region are partitioned in a rotatable disk-shaped body,
In the color filter region of the variable transmission filter, at least one of a transmission wavelength and a transmittance changes continuously or stepwise in the circumferential direction. The projector according to any one of claims 1 to 5,
Color conversion information storage means for storing color conversion information corresponding to the transmission characteristics of the color filter region of the variable transmission filter;
Operation status acquisition means for acquiring the operation status of the variable transmission filter during projection;
Based on the obtained operating state of the variable transmission filter, the use area determination means for determining whether the color filter area of the variable transmission filter is used or the total transmission area is used;
Color conversion processing means for performing color conversion processing of input image information with reference to color conversion information stored in the color conversion information storage means when it is determined that a color filter area is used; A projector characterized by comprising. The projector according to claim 6, wherein
A projector comprising: a light amount adjustment control unit that adjusts a light amount of a light beam emitted from the light source based on a determination result of the use area determination unit. The projector according to any one of claims 1 to 7,
A projector comprising filter operation control means for controlling operation of the variable transmission filter.