JPH09146039A - Projection display device - Google Patents

Abstract

(57) Abstract: The present invention reduces flare and improves the contrast of a projected image without reducing the brightness of the projected image. SOLUTION: In the plastic lens of the projection lens part,
A broadband antireflection film having a sufficiently low reflectance in the wavelength bands of blue, green and red is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a projection display device for projecting an image formed by a cathode ray tube or a liquid crystal panel on a screen using a projection lens.

[0002]

2. Description of the Related Art FIG. 11 (a) is a block diagram showing a basic structure of a display unit of a conventional projection display device using a cathode ray tube for forming an image, and FIG. 11 (b) is a block diagram of FIG. It is an expanded sectional view which shows the plastic lens provided in the display unit shown to (a). In FIG. 11A, the display unit 101 includes a cathode ray tube 102 that forms a desired image and a projection lens unit 103 that magnifies and projects the image on the screen 100. Cathode ray tube 102
On the inner surface of the face plate 104, a phosphor screen 105 coated with any one of blue, green and red phosphors is provided. Then, this cathode ray tube 102
In a projection display device using a screen, three display units 101 having different phosphor colors are used, and a screen 10
0 to form a color display image. That is, the images formed on the blue, green, and red phosphor screens 105 are enlarged and projected, and these blue, green, and red images are displayed on the screen 100.
The above is combined to form a color display image.

The projection lens unit 103 is composed of a lens barrel 106 made of a metal such as aluminum or a synthetic resin such as ABS resin, and a projection lens group 107 housed in the lens barrel 106. ing. In addition, the optical coupling unit 108 improves the contrast of an image formed on the screen 100 (hereinafter, abbreviated as “projection image”) in order to improve the contrast.
6 is provided at the end portion on the cathode ray tube 102 side. The optical coupling portion 108 is filled with a transparent liquid such as ethylene glycol, and the face plate 1
04 and the projection lens group 107 are optically coupled.
As a result, unnecessary reflected light to the fluorescent surface 105 that occurs on the surface of the face plate 104 is reduced, and the contrast of the projected image is improved.

The projection lens group 107 has a concave lens 107a that abuts the optical coupling portion 108, and a lens group 1 having a hybrid structure of a plurality of plastic lenses (not shown) and glass lenses (not shown).
It is composed of 07b. Aspherical concave lens 107
For a, a plastic lens such as polymethylmethacrylate (PMMA) having excellent workability is used.
An antireflection film that reduces the reflectance of incident light is provided on each of the lenses that form the concave lens 107a and the lens group 107b. That is, the glass lens in the lens group 107b is either a single-layer antireflection film, a specific wavelength antireflection film, or a broadband antireflection film, depending on the spectral distribution of the incident light on the glass lens. An antireflection film is formed. Further, in the plastic lens in the concave lens 107a and the lens group 107b, the plastic lens has lower heat resistance than the glass lens and has poor adhesion to the antireflection film, and the cathode ray tube 102.
In consideration of the fact that the antireflection effect in the emission spectrum of the image formed in 1 is sufficient, the wavelength band of the emission spectrum of the corresponding image is set for each plastic lens of each of the blue, green, and red projection lens units 103. A specific wavelength antireflection film or a single-layer antireflection film having the minimum reflectance at 1 is formed. For example, as shown in FIG. 11B, a low refractive index film 109a such as silicon dioxide and a high refractive index film 109b such as cerium dioxide are sequentially formed on the surface of the concave lens 107a of the plastic lens by a vapor deposition method or the like. The specific wavelength antireflection film 109 formed is formed.

Further, Japanese Patent Laid-Open No. 5-341269 discloses a conventional projection type display device using a liquid crystal panel (well-known, not shown). In such a conventional projection display device, a liquid crystal panel is used instead of the cathode ray tube 102 to form an image, thereby achieving downsizing and weight reduction of the projection display device. Then, the image of the liquid crystal panel is enlarged and projected on the screen 100 by using the projection lens unit. Although an active matrix type liquid crystal panel is used as the liquid crystal panel, it is not a general twisted nematic type, but it is possible to control the voltage applied to the pixel so that the liquid crystal becomes in a scattering state or a transparent state. A polymer-dispersed type that forms an image on a liquid crystal panel by utilizing it is used. In the invention of the publication, the high brightness of the projected image is achieved by using the polymer dispersion type liquid crystal panel. Further, in this conventional projection display device, the light scattered by the liquid crystal panel is reflected by the boundary surface between the glass and the air of the liquid crystal panel or the projection lens portion to generate unnecessary light. And this unwanted light
There is a case where the liquid crystal panel is incident again and scattered secondarily, and the contrast of the projected image is lowered. To reduce the contrast, for example, the above-mentioned Japanese Patent Laid-Open No. 5-341269.
As disclosed in the publication, in the optical coupling section 108, a silicone resin is used instead of a liquid such as ethylene glycol to optically couple the liquid crystal panel and the projection lens section to improve the contrast of the projected image. doing.

As described above, in the conventional projection display device, the concave lens 107a of the projection lens unit 103 and the plastic lens of the lens group 107b are reflected by a specific wavelength which minimizes the reflectance of a specific emission spectrum in a certain wavelength band. By forming the anti-reflection film or the single-layer anti-reflection film, flare and ghosts generated on the screen 100 are reduced to form a projected image. The flare means that light that does not contribute to the formation of a projected image is reflected or scattered by the components of the optical system such as the cathode ray tube 102, the liquid crystal panel, and the projection lens unit 103 arranged on the optical path. It refers to unnecessary light that is superimposed on a desired projection image.

[0007]

The conventional projection display device as described above has a problem that flare cannot be sufficiently reduced. Specific causes of this flare include multiple reflections on the fluorescent surface of the cathode ray tube, the face plate or the refraction surface of each lens of the liquid crystal panel and the projection lens section, scratches on the refraction surface, scattering due to dust, etc. And reflection from the inner surface of the lens barrel. However, the place where a lot of unnecessary light that causes flare is generated is the fluorescent surface of the cathode ray tube or the refracting surface of each lens of the liquid crystal panel and the projection lens unit. In a conventional projection display device, a concave lens of a projection lens unit and a plastic lens of a lens group are provided with a specific wavelength antireflection film or a single-layer antireflection film that minimizes the reflectance of an emission spectrum in a specific wavelength band. The generation of unnecessary light that causes flare is reduced. However, the single-layer antireflection film has a low antireflection effect and cannot sufficiently reduce flare. Further, the specific wavelength antireflection film cannot sufficiently prevent the reflection of the incident light when the incident angle of the incident light becomes large, so that the incident light from the cathode ray tube or the liquid crystal panel which emits the light in various directions is prevented. In some cases, the antireflection could not be performed sufficiently. Therefore, there is a problem in that the concave lens, which is arranged closest to the cathode ray tube or the liquid crystal panel, cannot prevent the incident light from being reflected, thereby generating unnecessary light that causes flare. Further, in the antireflection film as described above, the optical film thickness is set to a predetermined value to prevent reflection of incident light in a specific wavelength band. However, there is a problem that the wavelength band of the incident light capable of preventing reflection also changes, the reflection of the incident light cannot be sufficiently prevented, and unnecessary light is generated. As described above, in the conventional projection display device, it was not possible to prevent the generation of unnecessary light, and it was not possible to sufficiently reduce flare. Further, as a result, the brightness of the dark portion of the projected image is increased, and the contrast is lowered.

Further, in the conventional projection type display device, there are known some methods of absorbing unnecessary light by the constituent members of the optical system. For example, in Japanese Patent Laid-Open No. 3-224384, dye is dispersed in the concave lens 107a for coloring, or pigment is mixed in the fluorescent surface 105 to absorb unnecessary reflected light at the boundary surface between the concave lens 107a and air. , Indicates that the contrast of the projected image is to be improved. Further, Japanese Patent Laid-Open No. 3-61904 discloses that a liquid used for the optical coupling unit 108 is added with a light absorbing substance to absorb unnecessary light to improve the contrast of a projected image. There is. However, these conventional improvements have a problem in that the light necessary for the projection image may be absorbed, and the brightness of the projection image is reduced, so that the projection image becomes dark as a whole.

The present invention has been made to solve the above problems, and it is possible to reduce flare without lowering the brightness of a projected image and to improve the contrast of the projected image. The purpose is to provide a device.

[0010]

The projection display device of the present invention is provided corresponding to at least one image forming means for forming an image in accordance with a video signal and at least one image forming means. In the projection display device, wherein each of the lens groups further has a plurality of plastic lenses, and projection means for projecting an image formed by the image forming means onto a screen is provided, the plastic lenses are blue and green respectively. And a broadband antireflection film for preventing reflected light in the red wavelength band. Further, with this structure, the broadband antireflection film prevents the reflection of light and sufficiently reduces flare.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 An example of the projection type display device, which is the best mode of the present invention, will be described below. First Embodiment FIG. 1 is a configuration diagram showing a projection display device that is a first embodiment of the present invention. As shown in FIG. 1, the projection display apparatus 1 includes red, green, and blue display units 1R, 1G, and 1B that magnify and project red, green, and blue images on a screen 100, respectively. The display units 1R, 1G, and 1B are cathode ray tubes 2R, 2G, and 2B that form red, green, and blue images, respectively, and cathode ray tubes 2R, 2G, and 2B according to a video signal from a drive circuit (not shown). It has projection lens units 3R, 3G and 3B for enlarging and projecting the formed red, green and blue images on the common screen 100. These red, green and blue images are combined on screen 100 to form the desired color display image. Further, the three display units 1R, 1G and 1B are substantially the same as each other except that the red, green and blue phosphors respectively used in the cathode ray tubes 2R, 2G and 2B are different.
The plurality of plastic lenses of each projection lens unit 3R, 3G, and 3B are provided with the broadband antireflection film 9 having the same configuration shown in FIG. 3 (details will be described later).

Next, the display unit will be described in detail with reference to FIG. FIG. 2 is a partially enlarged cross-sectional view showing the main part of the display unit shown in FIG. As described above, the three display units 1R, 1G and 1B are
2A and 2B, which are substantially the same as each other except for coloring by dispersion of the dye in the plastic lens 7a described later.
Now, for example, only the green display unit 1G that magnifies and projects a green image will be described in detail, and the description of the red and blue display units 1R and 1B will be omitted. In FIG. 2, a fluorescent screen 5 is provided on the inner surface of the face plate 4 of the cathode ray tube 2G. The phosphor screen 5 is coated with a green phosphor that emits light having a green emission spectrum when irradiated with an electron beam. The projection lens unit 3G is
A substantially cylindrical lens barrel 6 made of a metal such as aluminum or a synthetic resin such as ABS resin, and a plurality of plastic lenses and glass lenses respectively arranged at predetermined positions in the lens barrel 6. And a projection lens group 7 which is a hybrid structure of the above. Further, the optical coupling section 8 improves the contrast of an image formed on the screen 100 (hereinafter, abbreviated as “projection image”) in order to improve the contrast.
Of the cathode ray tube 2G. That is,
The optical coupling section 8 is a transparent container filled with a transparent liquid such as ethylene glycol having a refractive index substantially the same as the refractive index of the face plate 4 and the first plastic lens 7a described later. Thereby, the optical coupling section 8 optically couples the face plate 4 and the projection lens group 7,
Unnecessary reflected light to the fluorescent surface 5 that occurs on the surface of the face plate 4 is reduced, and the contrast of the projected image is improved.

The projection lens group 7 includes first, second, third and fourth plastic lenses 7a, 7b, 7 formed of an optical resin such as polymethylmethacrylate (PMMA).
It is composed of d and 7e and a glass lens 7c. One surface of the first plastic lens 7a contacts the optical coupling portion 8 and is disposed inside the lens barrel 6. And the second plastic lens 7b,
The glass lens 7c, the third plastic lens 7d, and the fourth plastic lens 7e are sequentially arranged on the optical path from the first plastic lens 7a at predetermined intervals in the lens barrel 6. Further, the first plastic lens 7a is a concave lens that diverges light when strong negative power for correcting the field curvature of the projected image, that is, parallel light is incident. The second plastic lens 7b focuses the light when the action of the field curvature of the first plastic lens 7a changes due to a temperature change, that is, positive power that suppresses the change, that is, when parallel light is incident. It is a lens that does. The glass lens 7c is a convex lens having the strongest positive power, which has almost all the power related to the formation of the entire projected image, and the third and fourth plastic lenses 7d and 7e have the power of correcting spherical aberration and coma. It is a weak lens. In the first plastic lens 7a used for the green and red display units 1G and 1R, the emission spectrum components unnecessary for the light of the colors assigned from the green and red cathode ray tubes 2G and 2R are removed. In order to improve the color purity of green and red respectively,
The green and red dyes are uniformly dispersed and colored.

Each lens of the projection lens group 7 is provided with an antireflection film for reducing the reflectance of incident light in order to reduce flare and ghost generated on the screen 100. That is, in the glass lens 7c, according to the spectral distribution of the incident light on the glass lens 7c, etc.
An antireflection film such as a single-layer antireflection film, a specific wavelength antireflection film, or a broadband antireflection film is formed on the surface. Since these antireflection films are formed of substantially the same material and the same method as the broadband antireflection film 9 described below and differ only in thickness, description thereof will be omitted. Also, the first, second, third and fourth plastic lenses 7
On a, 7b, 7d and 7e, a broadband antireflection film 9 having a sufficiently low reflectance in all wavelength bands of blue, green and red emission spectra is formed on the surface. For example, the broadband antireflection film 9 provided on the first plastic lens 7a will be described with reference to FIG. 3, which is an enlarged cross-sectional view of the first plastic lens 7a. As shown in FIG. 3, the broadband antireflection film 9 has three low refractive index films 9a, 9c and 9e which are dielectric films made of, for example, silicon dioxide and a high refractive index film which is a metal film made of zirconium dioxide. It has a five-layer structure in which an index film 9b and a high refractive index film 9d, which is a metal film formed of titanium dioxide, are alternately laminated. That is, the broadband antireflection film 9 is formed of the low refractive index film 9a and the high refractive index film 9a on the first plastic lens 7a by a vapor deposition method or the like.
b, the low-refractive index film 9c, the high-refractive index film 9d, and the low-refractive index film 9e, the low-refractive index films 9a, 9c and 9e and the high-refractive index films 9b and 9d are alternately laminated. ing. Table 1 shows specific materials and film thickness of the broadband antireflection film 9. The broadband antireflection film 9 has
The plastic lens 7a is provided on the surface (air side) opposite to the cathode ray tube 2G, and the other second, third and fourth plastic lenses 7b, 7d and 7e are:
It is formed on both surfaces of the lens.

[0015]

[Table 1]

Incidentally, these plastic lenses 7a, 7
Since b, 7d, and 7e have lower heat resistance than the glass lens 7c, the adhesion of the antireflection film is weak and peeling or cracking of the broadband antireflection film 9 may occur at high temperature.
In such a case, a method of forming a protective film by vapor-depositing a metal film such as aluminum or chromium, then applying a cross-linking hardening resin by spin coating or dipping, and hardening by ultraviolet irradiation, or a silicon-based resin Adhesion at high temperature can be enhanced by a method in which a cross-linking cured resin is used as a primer between the plastic substrate and the broadband antireflection film.

Here, the calculation result of the spectral reflectance characteristic of the broadband antireflection film 9 used in the present invention is shown by a solid line 10 in FIG. Further, for comparison with the conventional one, the calculation result of the spectral reflectance characteristic of the conventional specific wavelength antireflection film 109 for blue, green and red shown in FIG. It is shown by a chain line 11B, a chain double-dashed line 11G and a broken line 11R, respectively. As shown in FIG. 4, the broadband antireflection coating 9 used in the present invention has a slightly higher minimum reflectance of incident light than the conventional antireflection coating 109 having a specific wavelength, but it has wavelengths of blue, green and red. The average reflectance of incident light in the band (wavelength λ between 420 nm and 650 nm) is as low as 0.7% or less. In the present invention, the blue wavelength band is 420 nm to 500 nm.
The wavelength range between 500 nm and 5 is the green wavelength band.
The wavelength is between 70 nm. The red wavelength band is 5
The wavelength is between 80 nm and 650 nm. Further, the broadband antireflection film 9 and the specific wavelength antireflection film 109 are
When the incident angle of light increases, the spectral reflectance characteristic shifts to the short wavelength side. The specific wavelength antireflection film 109 is originally a peak wavelength (460 nm, 54 nm) of the emission spectra of blue, green and red.
5 nm and 610 nm) are designed and formed to have the minimum reflectance. However, due to the above-mentioned phenomenon of shifting to the short wavelength side, the reflectance at the peak wavelength increases significantly when the incident angle of light increases. In the present invention, the broadband antireflection film 9
However, since the spectral reflectance characteristics are flat in the blue, green, and red wavelength bands, the reflectance hardly decreases even when the incident angle becomes large and the spectral reflectance characteristics shift to the short wavelength side. Moreover, reflection can be prevented.

Next, calculation results of reflectance characteristics of the broadband antireflection film 9 according to the present invention and the conventional specific wavelength antireflection film 109 when the incident angle of light is changed are shown in FIGS. It is shown in (a) and (b) of FIG. Incidentally, in the calculation results shown in FIGS. 5 and 6A and 6B, light having a wavelength λ of 550 nm is incident on the broadband antireflection film 9 and the conventional specific wavelength antireflection film 109. This is the case. Further, the calculation result of FIG. 5 is for the case where the optical thicknesses of the broadband antireflection film 9 and the specific wavelength antireflection film 109 are 1.0 according to the designed values, respectively. The calculation results of FIGS. 6A and 6B show that the optical film thickness is increased by -6% and + 6% from the design value due to the change of the refractive index of the substance and the control of the film thickness during film formation. This is when the film is formed. As shown in FIG. 5, in the vicinity of the incident angle of 0 degree, the reflectance of the specific wavelength antireflection coating 109 shown by the chain line 13 is lower than the reflectance of the broadband antireflection coating 9 shown by the solid line 12. In the range from the angle of incidence of 15 degrees or more to the angle of total reflection, the broadband antireflection film 9 is lower than that of the specific wavelength antireflection film 109. In addition, FIG.
And as is clear from FIG. 6B, the alternate long and short dash line 13a
In the specific wavelength antireflection film 109 shown by 13b and 13b, when the optical film thickness changes, the reflectance characteristic with respect to the incident angle changes greatly and the reflectance increases. On the other hand, the solid line 12a
The reflectance of the broadband antireflection film 9 shown by 12 and 12b hardly changes even if the optical film thickness changes.

Next, the solid line 14 in FIG. 7 shows the actual measurement results of the spectral transmittance characteristics of the lens having the broadband antireflection film 9 formed thereon. In addition, the above-mentioned blue, green, and red specific wavelength antireflection coatings 1
The measured results of the spectral transmittance characteristics of the lens in which 09 is formed are shown by the alternate long and short dash line 15B, the alternate long and two short dashes line 15G and the broken line 15R in FIG. According to the calculation result of the spectral reflectance shown in FIG. 4, the minimum reflectance is lower in the conventional lens having the specific wavelength antireflection coating 109 formed, but the actual measurement value obtained by forming the film on the actual lens shows that of the present invention. The lens having the broadband antireflection film 9 has a small reflectance of 1% or less in each of the blue, green, and red wavelength bands, which is lower than that of the conventional specific wavelength antireflection film 109. When forming the specific wavelength antireflection film 109, the specific wavelength antireflection film 109 having different spectral transmittance characteristics corresponding to the emission spectra of blue, green and red in the three projection lens units 103 of FIG. Need to be formed. On the other hand, when forming the broadband antireflection film 9, it suffices to provide the same broadband antireflection film 9 for all the three projection lens units 3R, 3G, and 3B in FIG. As a result, the productivity of the projection lens unit 3 can be improved, and the manufacturing cost of the projection display device 1 can be reduced.

As described above, in the projection display apparatus 1 of the first embodiment, each plastic lens 7 of the projection lens unit 3 is used.
By forming a broadband antireflection film 9 on a, 7b, 7d and 7e, which has a characteristic that the reflectance is sufficiently low even if the incident angle becomes large, unnecessary reflection of light is prevented and flare is sufficiently prevented. Has been reduced to. As a result, the contrast of the projected image can be significantly improved. In the above embodiment, the case where the broadband antireflection film 9 is formed on all the plastic lenses 7a, 7b, 7d and 7e has been described. Apart from such an embodiment, the broadband antireflection film 9 may be formed only on the first plastic lens 7a to reduce the occurrence of flare. Because the cathode ray tube 2R,
The light from 2G and 2B is emitted in various directions, and the F number of the projection lens units 3R, 3G, and 3B is about 1.
Since each of them is as small as 0, the incident angle of light incident on each lens surface of the projection lens group 7 becomes large. Especially,
The first plastic lens 7a has a small radius of curvature,
In addition, since it is arranged closest to the cathode ray tube, the incident angle of the light incident on the lens surface is different from that of the other plastic lens 7.
Larger than b, 7d and 7e. Therefore, even if the broadband antireflection film 9 is formed only on the first plastic lens 7a, the broadband antireflection film 9 provided on the lens can sufficiently prevent unnecessary reflection of light. Is.

Embodiment 2 A projection display apparatus which is Embodiment 2 of the present invention will be described below. The difference from Example 1 is that the high refractive index films 9b and 9d are formed of cerium dioxide from zirconium dioxide and titanium dioxide shown in Table 1. The other structure is the same as that of the first embodiment, and the description thereof is omitted. The broadband antireflection film 9 according to the second embodiment.
Table 2 shows the specific material and the film thickness thereof.

[0022]

[Table 2]

As a result of measuring the contrast of the projection type display device 1 having the broadband antireflection film 9 shown in Table 2, the contrast is about as compared with that of the conventional projection type display device having the specific wavelength antireflection film 109. It was possible to improve by 35%. The contrast measurement method is EIAJ C
It carried out using the white background contrast shown by P-4101 "projection type television receiver test method."

Embodiment 3 A projection type display device of the present invention for forming an image by a liquid crystal panel will be described with reference to FIG. FIG. 8 is a block diagram showing the optical arrangement of a projection display apparatus that is Embodiment 3 of the present invention. In FIG. 8, the projection display device 16 includes a light source 1
7, a light condensing unit 18 that condenses emitted light from the light source 17, a color separating unit 21 that separates white light from the light condensing unit 18 into blue, green, and red color components, and color light from the color separating unit 21. Three identical liquid crystal panels 2 that are illuminated and form an image according to the video signal
5R, 25G and 25B, three liquid crystal panels 25R, 2
Color combining section 26 for combining color lights emitted from 5G and 25B, and liquid crystal panels 25R, 25G and 25B
It has a projection lens unit 30 for enlarging and projecting the image formed in (3) on the screen. Further, on the light source 17 side of the liquid crystal panels 25R, 25G and 25B, a field lens 31R,
31G and 31B are arranged, respectively. further,
The liquid crystal panels 25R, 25G and 25B have optical coupling parts 32R, 3R and 3R formed of silicon resin.
The plastic lenses 30R, 30G, and 30B of the projection lens unit 30 are optically coupled via 2G and 32B, respectively. These plastic lenses 30
On the other hand, the liquid crystal panel 25 is provided for R, 30G and 30B.
The broadband antireflection film 9 shown in Example 1 is formed on the surface opposite to R, 25G and 25B. Also, these plastic lenses 30R, 30G and 3
By using a plano-concave lens that is concave on the projection lens unit 30 side of 0B, the light reflected by the concave surface is reflected by the liquid crystal panel 25.
The incident light is prevented from entering the R, 25G, and 25B image forming areas as much as possible.

The emitted light from the light source 17 composed of a metal halide lamp, a xenon lamp or the like is condensed by a condensing unit 18 composed of a concave mirror 19 and a condenser lens 20, and converted into substantially parallel light. Then, the light collecting unit 18
Substantially parallel white light from is incident on the color separation unit 21. The color separation unit 21 includes a first dichroic mirror 22 that reflects red light, a second dichroic mirror 23 that reflects green light, and a mirror 24. The first and second dichroic mirrors 22 , 23 separates the white light into lights of red, green and blue colors. The red, green, and blue light is emitted from the field lens 31.
The light passes through R, 31G, and 31B and enters the polymer-dispersed liquid crystal panels 25R, 25G, and 25B, respectively. In these liquid crystal panels 25R, 25G, and 25B, by controlling the voltage applied to the pixels according to the video signal,
The liquid crystal becomes a scattering state or a transparent state, and red,
Form green and blue images.

Here, using FIG. 9 (a) and FIG. 9 (b), which schematically show the operation principle of the liquid crystal panel, a schematic structure and operation principle diagram of the liquid crystal panel 25R for red, for example, will be described below. explain. 9A is an explanatory diagram showing a state of the liquid crystal panel 25R when no voltage is applied, and FIG. 9B shows a state of the liquid crystal panel 25R when a voltage is applied. It is an explanatory view shown. As shown in (a) of FIG. 9, the active matrix polymer dispersion type liquid crystal panel 25R has two glass substrates 33, 34 between the two glass substrates 33, 34.
A polymer material 36 in which liquid crystal droplets 37 are dispersed is enclosed. In addition, electrodes 35 and 35 ′ connected to a power source 39 are provided between the polymer material 36 and the glass substrates 33 and 34. When no voltage is applied to the liquid crystal panel 25R, the liquid crystal molecules 38 in the droplets 37 are randomly oriented, so the average refractive index of the liquid crystal droplets 37 and the refractive index of the polymer material 36 are small. Is different from. Therefore, the incident red color light 40 is scattered, and the liquid crystal panel 25R is in a scattered state. When a voltage is applied to the liquid crystal panel 25R, as shown in FIG. 9B, the liquid crystal molecules 38 are aligned in the direction of the electric field, and the refractive index of the liquid crystal molecules 38 in the direction of incident light and the polymer material. The refractive index of 36 is almost the same. Therefore, the incident red color light 40 is transmitted without being scattered, and the liquid crystal panel 25R becomes transparent. As described above, in the active matrix polymer dispersion type liquid crystal panel 25R, the liquid crystal changes between the scattering state and the transparent state by switching, and a desired image is formed on the liquid crystal panel 25R.

Returning to FIG. 8, liquid crystal panels 25R and 25G.
And the light of each color of red, green, and blue transmitted through 25B is a color composed of a third dichroic mirror 27 that reflects green light, a fourth dichroic mirror 28 that reflects blue light, and a mirror 29. It is incident on the combining unit 26. In the color synthesizing section 26, the lights of the respective colors of red, green and blue are synthesized into predetermined color colors by the third and fourth dichroic mirrors 27 and 28 and enter the projection lens section 30. Then, the projection lens unit 30 causes the screen 100
Projected enlarged.

As described above, the liquid crystal panels 25R, 25
The broadband antireflection film 9 is formed on the plastic lenses 30R, 30G, and 30B on the projection lens unit 30 side of G and 25B.
As described above, the flare can be sufficiently reduced and the contrast of the projected image can be significantly improved, as in the first embodiment. The liquid crystal panel 25
As the lens of the projection lens unit 30 arranged in close contact with R, 25G and 25B, the plastic lens 30R,
The reason why 30G and 30B are used is that a plastic lens is easy to form an aspherical shape for effective aberration correction and is lightweight. Further, since the projection images of the three liquid crystal panels 25R, 25G, and 25B are superposed on each other, it is necessary to mechanically finely move the images on the liquid crystal panels 25R, 25G, and 25B. It is desirable that the lens placed in close contact with 25R, 25G and 25B is a lightweight plastic lens.

Further, the liquid crystal panels 25R, 25G and 25
The light scattered by B is reflected by the liquid crystal panels 25R, 25G and 25.
The interface between the glass substrate of B and the air and the liquid crystal panels 25R, 2
Unnecessary reflected light is generated by the refracting surfaces of the plastic lenses 30R, 30G, and 30B arranged close to 5G and 25B. Then, the unnecessary reflected light is again returned to the liquid crystal panel 25.
It is incident on R, 25G and 25B to generate secondary scattered light, which tends to reduce the contrast of the projected image. In such a case, the plastic lens 30 has a large incident angle.
Light enters the respective lens surfaces of R, 30G and 30B,
Since the broadband antireflection film 9 is formed on the plastic lenses 30R, 30G, and 30B, unnecessary reflected light of the incident light can be sufficiently reduced and the contrast can be improved. Incidentally, the plastic lenses 30R, 30
When G and 30B are optically coupled to the liquid crystal panels 25R, 25G and 25B, respectively, the optical axes of the plastic lenses 30R, 30G and 30B and the liquid crystal panel 25R,
It is necessary to accurately align the centers of the image forming areas of 25G and 25B. However, when it is difficult to perform accurate alignment, a plastic plate formed in a flat shape with an optical resin such as polymethylmethacrylate may be used instead of the plastic lens having a concave surface on one side. In this case, by making the plastic plate thicker than the central thickness of the plano-concave lens, the reflected light is prevented from returning to the image forming area of the liquid crystal panel as much as possible.

Embodiment 4 A projection type display apparatus which is Embodiment 4 of the present invention will be described with reference to FIG. FIG. 10 is a configuration diagram showing an optical arrangement of a projection display apparatus that is Embodiment 4 of the present invention. In FIG. 10, the projection display device 41 includes a light source 17, a condensing unit 18 that condenses light emitted from the light source 17, and a liquid crystal panel that illuminates white light from the condensing unit 18 and forms an image in accordance with a video signal. 43 and a projection lens unit 44 for enlarging and projecting the image formed by the liquid crystal panel 43 on the screen. Also,
On the light source 17 side of the liquid crystal panel 43, the field lens 4
2 are arranged respectively. Furthermore, the liquid crystal panel 43
A plastic lens 44a of the projection lens unit 44 is optically coupled to the lens via an optical coupling unit 45 formed of silicon resin. The plastic lens 44a is provided with the broadband antireflection film 9 shown in the first embodiment on the surface opposite to the liquid crystal panel 43. Further, a plano-concave lens that is concave on the projection lens portion 44 side is used for these plastic lenses 44a so that light reflected by the concave surface is prevented from entering the image forming area of the liquid crystal panel 43 as much as possible.

The emitted light from the light source 17 composed of a metal halide lamp, a xenon lamp or the like is condensed by a condensing unit 18 composed of a concave mirror 19 and a condenser lens 20, and converted into substantially parallel light. Then, the light collecting unit 18
The substantially parallel white light from the above enters the polymer dispersion type liquid crystal panel 43 via the field lens 42. In this liquid crystal panel 43, by controlling the voltage applied to the pixels according to the video signal, the liquid crystal becomes in a scattering state or a transparent state, and an image is formed on the panel. LCD panel 43
The light transmitted through enters the plastic lens 44a of the projection lens unit 44. Then, it is enlarged and projected on the screen 100 by the projection lens unit 44.

The light scattered by the liquid crystal panel 43 is emitted in various directions. This scattered light becomes unnecessary reflected light on the refracting surface of the plastic lens 44a arranged close to the liquid crystal panel 43, and enters the liquid crystal panel 43 again to generate secondary scattered light, which lowers the contrast. And
However, since the broadband antireflection film 9 having a low reflectance is formed on the plastic lens 44a even when the incident angle becomes large, the plastic lens 44a is formed.
Unnecessary reflected light incident on the lens surface at various angles can be sufficiently reduced, and the contrast can be improved. By using green, blue, and red color filters on the liquid crystal panel 43, a projection display device that projects a color display image is configured.

As described above, in the projection type display device of the present invention, the wide band antireflection film is formed on the plastic lens of the projection lens portion to reduce the flare without lowering the brightness of the projected image and to project the image. The contrast of the image is improved. It goes without saying that the cathode ray tube or the liquid crystal panel, the light source, the projection lens section, and the transmissive screen can be incorporated into the cabinet to form a rear projection type projection display device.

[0034]

According to the present invention, by forming the broadband antireflection film on the plastic lens of the projection lens unit, unnecessary light is not required on the fluorescent screen of the cathode ray tube or the liquid crystal panel, and the refracting surface of each lens of the projection lens unit. The reflected light is reduced, and the flare can be sufficiently reduced without lowering the brightness of the projected image. Therefore, the contrast of the image on the projection display device can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a projection display apparatus that is Embodiment 1 of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a main part of the display unit shown in FIG.

FIG. 3 is an enlarged sectional view of a first plastic lens 7a according to the present invention.

FIG. 4 is a graph showing calculation results of spectral reflectance characteristics.

FIG. 5 is a graph showing calculation results of reflectance characteristics with respect to changes in the incident angle of light.

FIG. 6 is a graph showing a calculation result of reflectance characteristics with respect to a change of an incident angle of light and an optical film thickness, and (a) shows a case where the optical film thickness is −6% thicker than a designed value. And
(B) is the case where the optical film thickness is + 6% thicker than the designed value.

FIG. 7 is a graph showing an actual measurement result of spectral transmittance characteristics.

FIG. 8 is a configuration diagram showing an optical arrangement of a projection display apparatus that is Embodiment 3 of the present invention.

FIG. 9 is a schematic configuration of a polymer dispersion type liquid crystal panel and its operation principle diagram.

FIG. 10 is a configuration diagram showing an optical arrangement of a projection display apparatus that is Embodiment 4 of the present invention.

FIG. 11 is a configuration diagram showing a basic configuration of a display unit of a conventional projection display device.

[Explanation of symbols]

2G, 2R, 2B Cathode ray tube 3G, 3R, 3B, 30, 44 Projection lens unit 7 Projection lens group 7a, 7b, 7d, 7e, 30R, 30G, 30B, 4
4a Plastic lens 9 Broadband antireflection film 9a, 9c, 9e Low refractive index film 9b, 9d High refractive index film 25R, 25G, 25B, 43 Liquid crystal panel

Claims (5)

[Claims] 1. At least one image forming means for forming an image in accordance with a video signal, and a lens group provided corresponding to at least one image forming means, each lens group further comprising a plurality of plastic lenses. A projection display device having projection means for projecting an image formed by the image forming means onto a screen, wherein a broadband reflection for preventing reflected light in each of the blue, green and red wavelength bands in each of the plastic lenses is provided. A projection-type display device having a protective film formed thereon. 2. Of the plurality of plastic lenses,
2. The projection display device according to claim 1, wherein the broadband antireflection film is formed only on the plastic lens disposed closest to the image forming unit. 3. The broadband antireflection film has a five-layer structure in which three low refractive index films and two high refractive index films are alternately laminated on the surface of the plastic lens. 1. The projection display device according to 1. 4. The method according to claim 3, wherein the three low refractive index films are formed of silicon dioxide, one of the two high refractive index films is formed of titanium dioxide, and the other is formed of zirconium dioxide. Projection display device. 5. The projection display device according to claim 3, wherein the three low refractive index films are formed of silicon dioxide, and the two high refractive index films are formed of cerium dioxide.