JP3302267B2 - Optical modulation device and color image display device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical modulation device and a color image display device using the optical modulation device.

[0002]

2. Description of the Related Art Conventionally, in a single-plate color optical modulator using a liquid crystal optical modulation element, the area of a black matrix that shields the wiring of an optical modulation controlled part located around the liquid crystal optical modulation element occupies the liquid crystal optical modulation element. The ratio is high, and this is a factor that lowers the light use efficiency of the entire device.

In order to solve this problem, the light-collecting element group 2 as shown in FIG.
There is known a method of improving the light use efficiency of the optical modulation device 200 by disposing the illumination light from the white light source on each pixel of the optical modulation element 201 by disposing the illumination light from the white light source on the front surface of each of the 51G and 51B. Here, 3 in FIG. 14 is a transparent substrate, and 5 is a black matrix.

[0004]

In the above-mentioned conventional example, a color filter is used as a member for extracting color light corresponding to each optical modulation element from white light. However, since the color filter transmits only light of a certain wavelength component among white light incident on each pixel, light of other wavelength components is wasted, and the light use efficiency is extremely low.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional example, and has as its object to provide an optical modulation device having a small loss of light quantity and good image quality.

[0006]

In order to achieve the above object, an optical modulator according to the present invention comprises an optical modulator for modulating incident light for each pixel and outputting the same, and a light beam of a wide wavelength band having a predetermined wavelength. A color separation element that separates each band, and a light flux separated by the color separation element for each predetermined wavelength band is made incident on different pixels of the optical modulation element to modulate incident light. The color separation element is characterized in that the color separation elements alternately have a color separation area that separates incident light for each predetermined wavelength and a non-color separation area that transmits incident light as it is.

In the optical modulator of the present invention, it is preferable to have a lens array that collects a light beam in a wide wavelength band or a light beam that has passed through a color separation element and makes condensed light incident on each pixel of the optical modulation element. .

The optical modulator of the present invention preferably has a color separation area of a color separation element for every other lens constituting the lens array.

In the optical modulator of the present invention, binary optics, holograms, etc. are used for the color separation element.

[0010] Further, a form in which a color filter is arranged between the color separation element and the optical modulation element is also conceivable. At this time, a form in which a color filter is provided only on the optical path of the white light beam that has passed through the color non-separated area may be considered.

As the optical modulation element used in the optical modulation device of the present invention, a polymer dispersion type liquid crystal, a TN type liquid crystal, a guest host type liquid crystal, or the like is suitably used. In particular, when a polymer-dispersed liquid crystal is used for the optical modulation element, it is preferable to provide a light shielding wall between pixels.

The optical modulator of the present invention may be of either a reflection type or a transmission type, and details will be described in the embodiments of the invention.

By using the optical modulation device of the present invention for a color image display device, a high quality image can be displayed.

[0014]

FIG. 1 is a cross-sectional view (a cross section parallel to the optical axis of the device) of a part of an optical modulator that best illustrates the features of the present invention.

In FIG. 1, reference numeral 1 denotes an optical modulation element including an optical modulation control section (not shown) and an optical modulation control section. In the present embodiment, a polymer-dispersed liquid crystal is used for the optical modulation controlled part. Reference numeral 2 denotes a light-collecting element group for condensing incident light, 3 denotes a transparent substrate that sandwiches the optical modulation element 1, and 4 denotes a light-shielding film that shields light unnecessary for image display. Reference numeral 6 denotes a color separation element in which light condensed by the light condensing element group 2 is divided into a plurality of color lights and a region for emitting the light is provided two-to-one with respect to each light condensing element. Reference numeral 7 denotes a reflection plate provided between the optical modulation element 1 and the transparent substrate 3.

In the figure, R (red) and G of the optical modulation element group 1 are shown.
The symbols of (green) and B (blue) indicate the respective optical modulation elements 1
Represents the wavelength band of light incident and reflected by each pixel. White light is incident on and reflected from the pixel marked W (white).

In FIG. 1, arbitrary light-collecting elements are denoted by A0 and A
A light condensing element adjacent to 0 is a pixel of the optical modulation element including the optical axes of A + 1, A-1, and A0 (the center line of the condensed light flux).
Pixels of the optical modulation element adjacent to 0, T0 are represented by T + 1, T−
1. The area of the color separation element including the optical axis of A0 (color separation area) is S0, and the area of the color separation element adjacent to S0 (non-color separation area) is S + 1 and S-1. After passing through the color separation area S0, the white light flux condensed at A0 is color-separated into three color lights in the RGB band, enters the pixels T0, T + 1, and T-1, and is reflected by the reflection plate 7. The luminous flux of each wavelength band undergoes optical modulation until it is emitted from the pixels T0, T + 1, T-1. The light in the G wavelength band reflected by the reflection plate 7 and modulated by the pixel T0 is collected by the condensing element A0.
And is emitted as substantially parallel light. Similarly, pixel T-1,
The light in the B and R wavelength bands modulated by T + 1 is converted into substantially parallel light by the light condensing elements A-1 and A + 1, and emitted.

The non-color separation areas S + 1 and S-1 are areas where incident light is directly transmitted. Therefore, pixel T + 2,
After white light is incident on T-2 and modulated, the light is emitted from the light-collecting element as substantially parallel light at A + 1 and A-1.

That is, as shown in FIG. 1, from a light-collecting element such as A0 corresponding to a color separation area such as S0,
The light in the G wavelength band is emitted, and S + 1 adjacent to the light is emitted.
From a light-collecting element such as A + 1 or A-1 corresponding to a non-color separation area that directly transmits incident light such as
The white light that has entered the light-collecting element itself and the light in the R and B wavelength bands that have entered the light-collecting elements on both sides and have been separated by the color separation region are output. A + 1 and A- that exist every other
White light emitted from a light-collecting element such as 1 functions as image information that gives luminance.

Although the refraction of light between different media is not shown in FIG. 1, it is necessary to consider this difference in refractive index when actually designing. This is the same in the drawings in which the subsequent light rays are drawn.

The principle of optical modulation by polymer-dispersed liquid crystal is generally known and will not be described.

Next, an example of a method of driving an image signal in a liquid crystal panel according to the present embodiment will be briefly described.

When the input image is a video signal, an image signal for one frame of the image to be displayed is temporarily stored in a memory, and then sampling is performed by sequentially changing the order so as to correspond to the pixel arrangement of the panel. In the case of an input image already stored in memory such as a data signal of a personal computer or the like, it can be handled by changing the sampling method.
However, in this embodiment, since the panel pixels of each color are different in each line, the image signal corresponding to the color light having a small number of pixels is obtained by averaging two pixels of the original image signal into one pixel. Processing must be performed before sampling.

Next, the color separation element 6 will be described with reference to an enlarged sectional view of FIG.

In the present embodiment, the color separation element 6 is formed by molding a phase-type diffraction grating called binary optics (hereinafter referred to as BO) in a resin every other area corresponding to each light condensing element. BO is a diffraction grating having a stepped shape as shown in FIG. 2, and in particular, the diffraction grating shown in the present embodiment is designed to specify the grating pitch of the diffraction grating and the amount of phase change to thereby determine the zero of each diffraction grating. Most of the energy is concentrated on the next and ± 1st order diffracted light, and the wavelength band with the highest energy of each of the 0th and ± 1st order diffracted light (hereinafter, the main wavelength band)
Are configured to correspond to any of RGB. In the present embodiment, the step width L is set within the lattice pitch P.
It has a three-stage shape of 1, L2 and L3. In addition, if the number of stages is three or more, it can be configured such that the same effect can be obtained even in four stages or five stages. The transmission type BO as shown in the present embodiment is disclosed in Applied Optics, Vol. 17, No. 15, No. 2273-2279 (1978.88.1).
As disclosed in Japanese Patent Application Laid-Open No. H10-260, an incident light beam incident on a BO is transmitted and diffracted and separated mainly into three directions. In this BO, for example, when the blazed wavelength is λ0 and the blazed wavelength is λ0, the required grating thickness Dt for the blazed wavelength λ0 is Dt = m · λ0 / (nλ0-1). Here, nλ0 is the refractive index of the medium. m, λ
0 is m = 2, λ0 = 530 nm, and the refractive index nλ0 =
When calculated as about 1.5, the lattice thickness is Dt = 212.
It is about 0 nm.

FIG. 3 is a schematic view of a reflection type color image display device using the optical modulation device 10. As shown in FIG.

In FIG. 3, reference numeral 10 denotes an optical modulator of the present invention;
1 is a white light source placed at the focal position of a parabolic mirror 12, 13 is a condenser lens, 14 is a projection lens, 15 is a projection lens aperture, 16 is a projection screen, 17 is a condenser lens, 1
Reference numeral 8 denotes a mirror provided on the white light source 11 side of the projection lens stop 15.

The light emitted from the white light source 11 is applied to a parabolic mirror 12.
Is converted into substantially parallel light by the condenser lens 17, the mirror 18,
The light enters the optical modulation device 10 via the condenser lens 13. The light provided with the image information for each of the RGB color lights by the optical modulation device 10 displays an image on a projection screen 16 via a condenser lens 13 and a projection lens 14.

The image information of each color light of RGB depends on the degree of diffusion of the light beam by the optical modulator 10. When a stop having an aperture on the optical axis as shown in FIG. 3 is used, a light beam having a low degree of diffusion passes through the projection lens stop 15 and reaches the projection screen 16, while a light beam having a high degree of diffusion is projected on the projection lens stop. 15 does not reach the projection screen 16. That is, by changing the diffusivity of the light flux of each pixel of the optical modulation device 10, the amount of light reaching the projection screen 16 can be changed, and the gradation of an image can be displayed. Contrary to the configuration as shown in FIG. 3, even in the case of an aperture shape that blocks a light beam near the optical axis, similar gradation display of an image is possible.

With this configuration, it is possible to greatly improve the light use efficiency of the outgoing light with respect to the incident light. At the same time, by using the optical modulation device 10 of the present invention for a color image display device, a bright device can be provided without increasing the size of the device. Further, since the black matrix of the optical modulation device is not visible on the screen, it is possible to appreciate a high quality image even when approaching the screen. Further, since an incident light beam is condensed for one pixel, a pixel having a low aperture ratio can be employed, so that there are many advantages such as an increase in the production yield of the optical modulation element. .

In this embodiment, BO is used as the color separation element, but another color separation element such as a hologram may be used. Further, as shown in FIG. 4, the light condensing element may be a flat microlens 41. In the configuration shown in FIG. 4, the flat microlens 41 is formed integrally with the color separation element 6 and bonded to the transparent substrate 3. With this configuration, the device can be made compact. Further, a configuration in which the arrangement order of the light-collecting element and the color separation element is reversed is also conceivable.

In this embodiment, the number of pitches in one light-collecting element of the BO is set to two as shown in FIG. 2, but it is necessary to change it according to the specifications of the optical modulator. Also, 1
Slightly changing the grating thickness in the pitch for each step;
By designing the BO shape such that the grating width within the pitch is unequally spaced, the ± 1st-order analysis light inner band component can be reduced, so that ideal color separation can be further achieved. Also, the reflection plate 7
May be formed simultaneously with a metal layer forming the wiring portion of the optical modulation element 1.

Further, as shown in FIG. 5, a form in which a color correction color filter 51 is provided at a place where each color light is separated can be considered. In this configuration, when the spectral characteristics of each color light separated by the color separation element 6 are different from the spectral characteristics of the image signal, each color light is made incident on the color correction color filter 51 to obtain ideal color information. Image color reproduction becomes possible. In this case, the light is transmitted through the color filter 51 after being decomposed into each color light, so that the light use efficiency does not decrease so much.

Further, a filter such as T + 2 or T-2 corresponding to a pixel on which white light is incident may be a filter transmitting light in the G wavelength band. At this time, the pixel on which the white light is incident must be driven based on the G signal. Further, it is also conceivable that a filter corresponding to a pixel on which white light is incident is a filter for transmitting light in an arbitrary wavelength band, and a filter is not provided for a pixel on which each color light of RGB is incident.

When a color filter is provided in the optical path of white light, a small amount of light loss occurs, but the light use efficiency is much higher than that of a conventional apparatus in which color filters are provided for all pixels.

As shown in FIG. 6, a light shielding wall 61 is provided between pixels in order to prevent light diffused by the polymer dispersed liquid crystal from being incident on adjacent pixels and causing crosstalk. Is also conceivable. With this configuration, it is possible to provide a color image display device with higher image quality.

The color filter 5 shown in FIG.
1. It is needless to say that the light shielding wall 61 shown in FIG. 6 may be simultaneously provided.

In this embodiment, the polymer-dispersed liquid crystal is used as the optical modulation controlled part, but other optical modulation controlled parts such as a TN type liquid crystal and a guest host liquid crystal may be used.

FIGS. 7 to 11 are plan views of the optical modulation device of the present invention as viewed from the incident side, and show the relationship between the arrangement of the condensing element and the pixels of the optical modulation element.

FIG. 7 shows an optical modulator according to the present invention.
Light incident on pixels including the central axis of the color separation area of the color separation element 6 (letters with underbars in FIG. 7) is G color. The light-collecting element 2 has a shape in which the refractive power of the lens in the direction parallel to the two sides of the pixel is different from each other, and the light beam incident on the light-collecting element A0 is condensed on the color separation element S0. In the case of FIG. 7, the separation efficiency of the color separation element (when a diffraction grating is used for the color separation element, the diffraction efficiency) is set to be the highest for the G color, so that the RG is output when the light is emitted from the optical modulation device.
The balance of the B light amount becomes uniform, and it is possible to provide a device that can easily adjust the white balance. Here, the pixel shape of the optical modulation element is a square, but may be a rectangle.

FIG. 8 shows an optical modulator according to the present invention.
The incident light (the alphabetic character with an underbar in FIG. 8) incident on the pixel including the central axis of each color separation area of the light-collecting element example arranged in an arbitrary one-dimensional direction (horizontal direction in the figure) is made identical. Is the B color, the light incident on the pixel including the central axis of each color separation region of the light-collecting element row adjacent to the light-collecting element row is the R color and the G color, respectively. Even if the pixels of the light condensing element and the optical modulation element are arranged in this manner, the same effect as the arrangement of FIG. 7 can be obtained.

In FIGS. 7 and 8, the two-dimensional arrangement of the pixels of the optical modulation element is arranged in a lattice, but the same effect can be obtained even in a staggered arrangement as shown in FIG.

FIG. 10 shows that all the light incident on the pixels including the central axis of each color separation area is G color, as in the case of FIG. Indicates that the adjacent color separation area in the vertical direction is also G color.
By arranging the pixels of the light condensing element and the optical modulation element in this manner, the BO is formed in a continuous shape in a certain one-dimensional direction, so that the BO can be easily formed and the cost can be reduced. Further, as shown in FIG. 11, the light-collecting element can be a lenticular lens. In this case, the black matrix structure in the direction that does not have the power of the lenticular lens cannot be removed and remains, but by changing the configuration of the black matrix while keeping the aperture ratio constant,
Almost the same effects as in the example shown in FIG. 10 can be obtained.

FIG. 12 is a diagram showing a transmission type optical modulation device 20. Components having the same reference numerals as those of the reflection-type optical modulation device 10 have the same functions, and thus description thereof will be omitted.

The difference from the reflection type optical modulator 10 is that
The point is that the light-collecting element group 2 is provided as a pair on the incident side and the output side. Therefore, the light-collecting element group 2 on the emission side functions as a collimating element.

Next, the image forming operation of the optical modulation device 20 will be described. As in the case of FIG. 1, arbitrary light-collecting elements are denoted by A0, light-collecting elements A + 1, A-1, and A0 adjacent to A0.
The pixel of the optical modulator including the optical axis (center line of the condensed light beam) is T0, the pixel of the optical modulator adjacent to T0 is T + 1,
One area (color separation area) of the incident side color separation element including the optical axes of T-1 and A0 is S0, and the area of the color separation element (non-color separation area) adjacent to S0 is S + 1, S-1, A0. The light-collecting elements on the emission side including the optical axis are denoted by C0, and the light-collecting elements adjacent to C0 are denoted by C + 1 and C-1. After passing through the color separation area S0, the white light flux condensed at A0 is color-separated into three color lights in the RGB band, enters the pixels T0, T + 1, and T-1, and undergoes optical modulation. The light in the G wavelength band modulated by the pixel T0 is converted into substantially parallel light by the light-collecting element C0 and emitted.

The white light incident from the light condensing elements A + 1 and A-1 is transmitted to the non-color separation areas S + 1 and S-1 of the color separation element.
Pass through to the pixels T + 2 and T-2 of the optical modulation element to be modulated, and collected together with the B and R color lights separated in the color separation areas adjacent to the non-color separation areas S + 1 and S-1. The light is converted into substantially parallel light by the optical elements C + 1 and C-1, and emitted from the optical modulation device 20.

Next, a schematic diagram of a transmission type color image display device using the optical modulation device 20 is shown in FIG.

The light emitted from the white light source 11 is
The light is converted into substantially parallel light by 2 and enters the optical modulation device 20.
The light to which the image information for each of the RGB color lights is given by the optical modulation device 20 is a condenser lens 13 and a projection lens 1.
An image is displayed on the projection screen 16 via the display 4.

As described above, the optical modulation device of the present invention can be implemented also in a transmission type, and the same effect as that of a reflection type optical modulation device can be obtained. Also, in the transmission type optical modulation device, various embodiments as illustrated and described with the reflection type device are conceivable.

[0051]

As described above, according to the present invention,
An optical modulation device with high light use efficiency can be realized. If the optical modulation device of the present invention is used for a color image display device, a device with good image quality can be realized without increasing the size of the device.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a reflection type optical modulation device of the present invention.

FIG. 2 is an enlarged sectional view of a color separation element.

FIG. 3 is a schematic diagram of a color image display device using the reflection type optical modulation device of the present invention.

FIG. 4 is an enlarged cross-sectional view of the optical modulation device of the present invention when a light-collecting element is a plane microlens.

FIG. 5 is a sectional view of a main part of a reflection type optical modulation device of the present invention.

FIG. 6 is a sectional view of a main part of a reflection type optical modulation device of the present invention.

FIG. 7 is a diagram showing the relationship between the arrangement of the pixels of the light condensing element and the optical modulation element.

FIG. 8 is a diagram showing the relationship between the arrangement of the pixels of the light condensing element and the optical modulation element.

FIG. 9 is a diagram showing the relationship between the arrangement of the pixels of the light condensing element and the optical modulation element.

FIG. 10 is a diagram showing the relationship between the arrangement of pixels of a light-collecting element and an optical modulation element.

FIG. 11 is a diagram showing the relationship between the arrangement of the pixels of the light condensing element and the optical modulation element.

FIG. 12 is a sectional view of a main part of a transmission type optical modulation device of the present invention.

FIG. 13 is a schematic view of a color image display device using the transmission type optical modulation device of the present invention.

FIG. 14 is a sectional view of a main part of a conventional optical modulation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical modulation element 2 Condensing element 3 Transparent substrate 4 Shielding film 6 Color separation element 7 Reflector 10 Optical modulation device 11 White light source 12 Parabolic mirror 13 Condenser lens 14 Projection lens 15 Projection lens stop 16 Projection screen 17 Condensing lens 18 Mirror 51 color filter 61 shading wall

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1335 G02B 5/18 G02B 5/32 G03B 33/12

Claims (16)

(57) [Claims] An optical modulator for modulating incident light for each pixel and emitting the same; and a color separation element for separating a light beam in a wide wavelength band for each predetermined wavelength band. In the optical modulation device in which the light flux decomposed for each wavelength band is made incident on different pixels of the optical modulation element and the pixel modulates the incident light, the color separation element decomposes the incident light for each predetermined wavelength. An optical modulation device having alternately color separation regions and non-color separation regions that directly transmit incident light. 2. The optical modulation device according to claim 1, further comprising a lens array that condenses the light beam in the wide wavelength band and makes convergent light incident on each pixel of the optical modulation element. 3. The optical modulation device according to claim 1, further comprising a lens array that condenses a light beam that has passed through the color separation element and makes convergent light incident on each pixel of the optical modulation element. 4. The optical modulation device according to claim 2, wherein said lens array is a flat microlens. 5. The optical modulation device according to claim 2, wherein the color separation element has a color separation area for every other lens constituting the lens array. 6. The optical modulation device according to claim 1, wherein the color separation element is binary optics. 7. The optical modulation device according to claim 1, wherein the color separation element is a hologram. 8. The optical modulation device according to claim 1, wherein a color filter is provided between the color separation element and the optical modulation element. 9. The optical modulation device according to claim 8, wherein the color filter is provided only on an optical path of a light beam that has passed through a non-color separation area of the color separation element. 10. The optical modulation device according to claim 1, wherein the optical modulation element is a polymer-dispersed liquid crystal. 11. The optical modulation device according to claim 10, wherein a light shielding wall is provided between pixels of the optical modulation element. 12. The optical modulation device according to claim 1, wherein the optical modulation element is a TN type liquid crystal. 13. The optical modulation device according to claim 1, wherein the optical modulation element is a guest-host type liquid crystal. 14. The optical modulation device according to claim 1, wherein the optical modulation device is a reflection type optical modulation device. 15. The optical modulator according to claim 1, wherein the optical modulator is a transmission type optical modulator. 16. A color image display device for displaying an image using the optical modulation device according to claim 1. Description: