JP2003262919A - Projection optical system and projection type image display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve focus performance and contrast performance by suppressing a decrease in the lightness of display video and to improve the quality of the display video. <P>SOLUTION: For, for example, a concave lens element 6a of a projection lens 7a of a projection tube 1a for red, is provided with a light transmitting means which has relation TRS≤TRL/3, where TRS is the transmissivity of the wavelength of subpeak energy in a short-wavelength range to the wavelength of the peak energy of a spectrum distribution of red video light from the projection tube 1a and TRL is the light transmissivity of the wavelength of the subpeak energy in a long-wavelength range, and for example, a concave lens element 6b of a projection lens 7b of a projection tube 1b for green, is provide with a light transmitting means which has relation TGL≤TGS/2, where TGS is the light transmissivity of the wavelength of the subpeak energy in a short- wavelength range to the wavelength of the peak energy of green video light from the projection tube 1b and TGS is the light transmissivity of the wavelength of the subpeak energy in a short-wavelength range. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection television receiver, a projection display device and the like, and more particularly,
Without compromising the brightness of such a device, increasing the color purity,
In addition, the present invention relates to a projection optical system for improving focus performance and contrast and a projection type image display device using the projection optical system.

[0002]

2. Description of the Related Art With the diversification of image sources, rear projection display devices have become widespread in the market as large-screen projection optical devices because of their lightness, low cost, and compactness.

This rear projection display device has a projection tube for generating red, green and blue image light as image generation sources (hereinafter referred to as red, green and blue image light projection tubes) inside a cabinet and each of these projection tubes. Each projection lens is provided independently, and the original image projected on the fluorescent screen of each projection tube is enlarged and projected on the screen by the projection lens and combined to display a full-color image. Has become.

In such a rear projection display device,
For example, as disclosed in Japanese Patent Application Laid-Open No. 3-224384, a colored lens element is adopted in order to impart wavelength selectivity (filter effect) to a projection lens used for a green image light projection tube. There is something. By reducing the spurious components close to the red and blue wavelengths contained in the emission spectrum of the phosphor on the green phosphor screen with this colored lens element, and expanding the color reproduction range of the enlarged image on the screen, The focus performance is improved by reducing the chromatic aberration. Further, by coloring the concave lens element near the fluorescent screen of the projection tube, unnecessary light components reflected by the exit surface and returning to the fluorescent screen can be absorbed and reduced twice, thus improving the contrast performance. There is.

Furthermore, in recent years, in addition to the projection lens used for the green image light projection tube as described above, the projection lens used for the red image light projection tube is also provided with wavelength selectivity (filter effect). For this reason, some use colored lens elements. This colored lens element reduces the spurious component near the green wavelength contained in the emission spectrum of the phosphor on the red phosphor screen,
The color reproduction range of the enlarged image on the screen is expanded. Further, similar to the green image light projection tube, the contrast performance is also improved by coloring the concave lens element close to the fluorescent screen of the red image light projection tube.

[0006]

On the other hand, the brightness of a normal display device is represented by the brightness of white that is enlarged and projected on the screen. When displaying white on an actual display device, if the chromaticity of the red, green, and blue image lights is constant, the red and blue image lights are based on the green light that is most dominant in brightness. Are added at a predetermined luminance ratio.
In order to generate the required brightness on the phosphor screen of each color projection tube, it is necessary to set each cathode current to a predetermined value from the cathode current vs. brightness characteristics of each projection tube.

At this time, as described above, in order to impart wavelength selectivity (filter effect) to the projection lens used in the green image light projection tube and the projection lens used in the red image light projection tube, coloring is performed. The adoption of the lens element improves the color purity, but on the other hand, some of the main components of the green image light and red image light are absorbed and attenuated by the colored lens element, resulting in a decrease in brightness. There is a problem of doing.

Further, since the transmissive screen is constructed by combining a plurality of transmissive members, a part of external light such as illumination light enters the screen and is reflected by the surface of the transmissive member inside. There is also a case where the returned external light is superimposed on the image light transmitted through the screen, which causes a reduction in the contrast performance of the image displayed.

Conventionally, a lenticular sheet is used as one of the transmissive members used in such a transmissive screen, and a light absorbing layer is provided between each of the vertically elongated lenticular lenses provided on the emission surface thereof. By absorbing the outside light with, the amount of the outside light entering the lenticular sheet is reduced, but even with this, the outside light enters from the vertical lenticular lens portion of the lenticular sheet, and it is the screen. Some of the light is reflected internally and returns, which is one of the causes of the deterioration of the contrast performance.

An object of the present invention is to solve such a problem, to suppress a decrease in brightness of a display image, improve focus performance and contrast performance, and improve the quality of the display image. Another object of the present invention is to provide a projection optical system and a projection type image display device using the projection optical system.

Another object of the present invention is to provide a projection optical system capable of suppressing a decrease in brightness of a displayed image and reducing an influence of reflection of external light, and a projection type optical system using the projection optical system. An object is to provide an image display device.

[0012]

In order to achieve the above object, the present invention provides a lens element of a projection lens corresponding to a green image light projection tube, and a projection lens provided for each red image light projection tube. The lens element and the light transmitting means having a predetermined light transmission characteristic are respectively provided to reduce unnecessary spurious components in the image light generated from the green image light projection tube and the red image light projection tube, and mainly Increase the transmittance of components. Further, in particular, by applying the light transmitting means to a concave lens element close to the fluorescent screen of the projection tube, unnecessary light components reflected by the emitting surface and returning to the fluorescent screen are absorbed and reduced twice, and the contrast performance is improved. Is also improving.

In order to achieve the above-mentioned other objects, the present invention provides a transmission screen with a wavelength of peak energy of a spectral distribution in image light obtained by each projection tube for red, blue and green image light. λ _Rmax , λ _Bmax , λ _Gmax
Light transmission means for attenuating the energy to a predetermined value or less is provided in wavelength regions other than the above.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. For convenience of explanation, a lens element of a projection lens corresponding to the projection tube for green image light of the present invention and a red image light are used. The light transmitting means having a predetermined light transmitting characteristic provided on the lens element of the projection lens corresponding to the use projection tube will be described in comparison with the prior art.

FIG. 1 is a sectional view showing the structure of a projection tube and a projection lens used in an embodiment of a projection optical system according to the present invention, in which 1 is a projection tube, 2 is a fluorescent screen, 3 is a face panel, Reference numeral 5 is a bracket, 6 is a concave lens element, 7 is a projection lens, and 101 to 105 are lens elements.

In FIG. 1, a bracket 5 is attached to the face panel 3 of the projection tube 1, and a concave lens element 6 is provided on the bracket 5. The refrigerant 4 is enclosed in a closed space formed by the face panel 3, the bracket 5 and the concave lens element 6.

On the front surface side of the concave lens element 6, a plurality of lens elements (here, five) are arranged from the concave lens element 6 side to the lens elements 105, 10.
4, 10, 10, 102 and 101 are arranged coaxially in this order, and the concave lens element 6 and the lens elements 105 to 101 form a projection lens 7 of the projection tube 1. Then, one of the lens elements forming the projection lens 7 (hereinafter, referred to as a concave lens element 6) is provided with a predetermined light transmission characteristic (filter characteristic) described later to obtain an intended effect described later. I am allowed to do so.

FIG. 2 is a sectional view of an embodiment of the projection optical system according to the present invention using the projection tube and the projection lens shown in FIG. 1, which is developed in a horizontal plane. 1a, 1b, 1c are red, respectively.
Projection tubes 2a, 2b, and 2c for green and blue image lights are fluorescent tubes (red, green, and blue fluorescent screens) of the projection tubes 1a, 1b, and 1c, and 3a, 3b, and 3c are projection tubes 1a and 1b, respectively. , 1c
Face panels 4a, 4b, 4c are projection tubes 1 respectively
Refrigerants a, 1b, 1c, 5a, 5b, 5c are brackets of the projection tubes 1a, 1b, 1c, 6a, 6b, 6c are concave lens elements of the projection tubes 1a, 1b, 1c, 7
Reference numerals a, 7b and 7c are projection lenses of the projection tubes 1a, 1b and 1c, respectively, and 8 is a screen.

In the figure, the projection tube 1a for red image light, the projection lens 7a and the like form a projection optical system for red image light. The projection tube 1a for red image light has its fluorescent screen 2
a red image is projected on a and the red image is projected by the projection lens 7a.
Is enlarged and projected on the transmissive screen 8. Further, the green image light projection tube 1b, the projection lens 7b, and the like form a green image light projection optical system. The projection tube 1b for green image light projects a green image on its fluorescent screen 2b,
The green image is enlarged by the projection lens 7b and projected on the screen 8. Further, a blue image light projection tube 1c, a projection lens 7c, and the like form a blue image light projection optical system. The projection tube 1c for blue image light has its fluorescent screen 2c.
A blue image is displayed on the screen, and the blue image is enlarged by the projection lens 7c and projected on the screen 8. These red, green,
The blue magnified and projected images are combined to display a full-color image on the screen 8. The overall configuration of each projection optical system for these red image, green image, and blue image has the configuration shown in FIG.

Of these red, green, and blue image light projection optical systems, the optical axis of the green image light projection optical system having the highest relative luminous efficiency is set to be perpendicular to the screen 8, and the red, blue The optical axis of the projection optical system of the image light is tilted in the opposite directions with respect to the screen 8 by a predetermined angle α.

FIG. 3 shows a state in which the entire projection optical system shown in FIG. 2 is housed in a cabinet of a projection type television receiver (hereinafter referred to as a projection type television set) which is one form of the projection type display device. Is a vertical sectional view showing
Reference numeral 9 is a mirror, and 10 is a cabinet, and parts corresponding to those in FIGS.

Here, for convenience of explanation, the portion consisting of the projection tube and the projection lens is simply referred to as a projection optical system, and the projection optical system according to the present invention includes the mirror 9 and the screen 8 as well. This is included and will be referred to as the entire projection optical system.

In the figure, a mirror 9 for folding the optical path is arranged between the screen 8 and the projection lens 7, and the optical path from the projection tube 1 through the projection lens 7 is folded back by the mirror 9 to reach the screen 8. Thus, the entire projection optical system is housed in the cabinet 10 to realize a compact set.

Next, before giving a concrete description of this embodiment, the luminosity characteristics will be described as a supplement.

FIG. 4 shows CIE 193 when the field of view is 2 °.
The value of tristimulus value yλ in the XYZ color system of No. 1 and C.I.E. 1964 when the observation field of view is 10 degrees as the XYZ color system applied to the color when the observation field of view exceeds 4 degrees.
Tristimulus values (y in the X10Y10Z10 auxiliary color system of
10) The value of λ is shown in the figure. This is an excerpt from Fig. 5.2 on page 398 of "Optical Technology Handbook Supplement," Asakura Shoten, where the horizontal axis is the wavelength (nm) and the vertical axis is Represent the values of the tristimulus values yλ and (y10) λ (the relative luminosity of the optic nerve present in the human retina).

For example, a diagonal dimension of 50 inches (1270 m
When observing a projection type TV set with an aspect ratio of 3: 4 of m) at a clear vision distance of 2 m, a range of 70 mm in diameter is observed on the screen in a field of view of 2 °.
This corresponds to observing a range having a diameter of 350 mm.

As is apparent from FIG. 4, in the wavelength region of 530 nm or less, the luminosity factor of the 10 ° field of view observing a wider range is higher than the luminosity factor of the 2 ° field of view. Is shown. In addition, it has the highest relative luminous efficiency.
Based on 46.3 nm light, up to 460 nm (about 90n
The relative luminosity in the long wavelength (red) region up to 640 nm (in the range of about 90 nm) shows a larger value than the relative luminosity in the short wavelength (blue) side of m range). .

FIG. 5 shows the tristimulus values x.lamda., Y.lamda., And z.lamda. In the XYZ color system of C.I.E. Similarly, X of CIE IE 1964 when the observation field of view is 10 °
Tristimulus values (y1 in the 10Y10Z10 auxiliary color system)
The value of 0) λ is shown in FIG.

Next, the emission spectrum distribution of the currently used red, green and blue phosphors will be described. FIG. 7 is a diagram showing an emission spectrum distribution of a phosphor used in a red image light projection tube, in which the vertical axis represents relative luminance (%) and the horizontal axis represents wavelength λ.
(Nm) respectively.

In the figure, the emission spectrum is 612.
580 to 6 which is the wavelength region on the short wavelength (green) side with respect to the component of the main wavelength λ _Rmax showing the peak energy in the vicinity of nm.
It includes a spurious component (wavelength λ _RSmax = 585 nm of sub-peak) near ₀₀ nm and a spurious component (wavelength λ _RLmax = 635 nm of sub-peak) near 630 nm which is the wavelength region on the long wavelength (red) side.

FIG. 8 is a diagram showing an emission spectrum distribution of a phosphor used in a green image light projection tube, in which the vertical axis represents relative luminance (%) and the horizontal axis represents wavelength λ (nm). I am taking it.

In the figure, the emission spectrum is 545
Spurious components (sub-peak wavelength λ _GSmax = 495 nm) existing in the short wavelength (blue) side wavelength region and long wavelength (red) side wavelength region with respect to the main wavelength λ _Gmax component showing peak energy near nm. Spurious components present in (the wavelength of the sub-peak is 590 nm and λ _GLmax of 630 n
m) and are included.

FIG. 9 is a diagram showing an emission spectrum distribution of a phosphor used in a blue image light projection tube, in which the vertical axis represents relative luminance (%) and the horizontal axis represents wavelength λ (nm). I am taking it.

In the figure, the emission spectrum distribution has a characteristic showing a mountain-shaped broad swell with a peak at a main wavelength of 460 nm. Main wavelength 4 with the highest relative brightness
Focusing on the wavelength range of ± 30 nm with respect to light of 60 nm, the relative luminance in the region on the short wavelength side is higher than the relative luminance in the region on the long wavelength side. Further, in the region exceeding 490 nm, the relative luminance gradually decreases, and the relative luminous efficiency becomes almost 0% at 565 nm.

Next, the light transmitting means in the prior art and the light transmitting means in this embodiment provided in the concave lens element 6 (FIG. 1) of the projection lens used in each of the projection tubes for red, green and blue image light respectively. The transmittance characteristics will be described.

FIG. 10 is a diagram showing the transmittance characteristics of the light transmitting means in the prior art provided in the concave lens element 6c (FIG. 2) in the projection lens 7c provided in the blue image light projection tube 1c. The horizontal axis shows the wavelength (nm), and the vertical axis shows the transmittance (%). Further, FIG. 11 is a diagram showing the transmittance characteristics of the light transmitting means in this embodiment provided in the same concave lens element 6c.

FIG. 12 is a diagram showing the transmittance characteristic of the light transmitting means in the prior art provided in the concave lens element 6a (FIG. 2) in the projection lens 7a provided in the red image light projection tube 1a. , FIG. 13 shows a similar concave lens element 6
It is a figure which shows the transmittance characteristic of the light transmission means in this embodiment provided in a.

Further, FIG. 14 shows a projection tube 1b for green image light.
Concave lens element 6b in the projection lens 7b provided in
FIG. 15 is a diagram showing the transmittance characteristic of the light transmitting means in the prior art provided in FIG. 2 and FIG. 15 shows the same concave element 6;
It is a figure which shows the transmittance characteristic of the light transmission means in this embodiment provided in b.

One of the main performance items of the projection television set
The brightness, which is one of the two, is represented by the display brightness when white is displayed on the screen. In order to obtain a predetermined white color by mixing the image lights of the three colors of red, green, and blue described above and to improve the display brightness, there is a method of changing the chromaticity of each color to change the distribution ratio of the cathode current. There is a method of increasing the brightness by increasing the cathode current flowing through each projection tube.

When the image light of each color having the characteristics shown in FIGS. 7, 8 and 9 is measured by a color luminance meter (BM-5 made by Topcon), the colors on the chromaticity diagram of CIE 1331 are measured. Degree (x, y)
Then, the blue image light is (0.126, 0.045), the red image light is (0.652, 0.342), and the green image light is (0.3
22, 0.578). These image lights are enlarged and projected on the screen 8 (FIG. 2), and white (color temperature 930
The luminance ratio of the three colors of red, green, and blue required to display 0K + 0MPCD and chromaticity points (0.285, 0.294) is 0.176: 1.0: 0.164. .

FIG. 16 is a characteristic diagram showing the relationship between the cathode current and the tube surface brightness in the projection tubes 1a, 1b and 1c (FIG. 2) for the current red, green and blue image lights.

In the figure, the respective projection tubes 1a, 1b,
The luminance when the same current is applied to the cathode of 1c is about 6 when the luminance of the red image light is based on the luminance of the green image light.
Although it is 0%, the brightness of the blue image light is extremely small at 5% to 20%, and particularly in the high current region (which occurs when a small number is displayed on a part of the black screen), The brightness is insufficient.

Therefore, the required relative luminance of 0.176 of the red image light with respect to the green image light for displaying white has a sufficient margin, but that of the blue image light with respect to the green image light is sufficient. The required relative brightness of 0.164 cannot be realized when the cathode current is 0.2 mA or more. For this reason, conventionally, a countermeasure has been taken in which the electron beam incident on the phosphor on the phosphor screen of the blue image light projection tube is thickened to compensate for the lack of brightness at the expense of focus performance.

On the other hand, in this embodiment, in order to make up for the lack of brightness of the blue image light having the emission spectrum distribution shown in FIG. By increasing the transmittance on the short wavelength side and increasing the color purity, it is possible to suppress the ratio of luminance distribution to a low level, thereby reducing the defocus amount.

Specifically, as shown in FIG. 11, 38
The lens element of the projection lens 7c (FIG. 2) is manufactured from a material having a transmittance of about 40% for light with a wavelength of 0 nm.
As a lens material that can realize this, PMMA (acrylic) resin manufactured by Kuraray Co., Ltd. (trade name: Acrypet HR
-1000L (clear) is available.

On the other hand, PMMA (acrylic) resin (trade name: Delpet 80NR (clear)) manufactured by Asahi Kasei Corporation is used as the lens material of the projection lens of the conventional projection tube for blue image light. is there. This transmittance characteristic is
As shown in FIG. 10, the transmittance for light having a wavelength of 380 nm is about 25%, and desired characteristics cannot be obtained. Next, as a lens material of the concave lens element 6a (FIG. 2) in the projection lens 7a used in the projection tube 1a for red image light, conventionally, for example, a coloring manufactured by Asahi Kasei Co., Ltd., which has the transmittance characteristic shown in FIG. PMMA (acrylic) resin pellets (trade name: Delpet 80NR (color number: LM
90410)). The desired characteristics were obtained by molding a lens element using this pellet.

However, in order to enhance the color purity of the red image light shown in FIG. 7 with this conventional technique, the spurious component existing on the short wavelength side with respect to the main wavelength λ _Rmax (= 615 nm) of the peak energy is used. Although the transmittance TRS with light of wavelength lambda _Rsmax of a sub-peak energy (= 585 nm) is to be set to be lower, is intact, the wavelength _λRmax the peak energy is the main component simultaneously
The transmittance of (= 615 nm) also decreases. Therefore, the chromaticity of red image light is slightly improved, but on the other hand,
It has been found that the brightness decreases and the brightness of white obtained when three colors of red, green, and blue are mixed is also decreased.

Therefore, the applicant of the present invention has found that the wavelength λ of the peak energy of red image light is based on the conventional lens material.
Wavelength λ of subpeak energy that is a spurious component existing on the short wavelength side with respect to _Rmax (= 615 nm)
_{If the} ratio of the light transmittance TRS at _RSmax (= 585 nm) and the light transmittance TRL at the wavelength _λRLmax of the sub-peak energy in the long wavelength side region is less than or equal to%, and what condition is satisfied, red, It was verified by an experiment whether further improvement in color purity can be discriminated without substantially reducing the brightness of white obtained by mixing three colors of green and blue.

As a result, the decrease in light transmittance with respect to the wavelength λ _Rmax (= 615 nm) of the peak energy of red image light is 10% or less of the light transmittance of the reference lens material, and TRS ≦. A lens element formed of a lens material having a transmittance characteristic satisfying the condition of TRL / 3 is used for the projection lens 7a, and a projection lens 7b provided on a green image light projection tube 1b (FIG. 2) described later is used. Due to the relation with the light transmitting means provided in the lens element, the luminance of white obtained when the three colors of red, green and blue are mixed is hardly reduced, and the effect of further improving the chromaticity can be obtained visually. It turned out to be.

As a lens material capable of realizing the light transmitting means provided in the lens element of the projection lens 7a corresponding to the above-mentioned red image light projection tube 1a, for example, FIG.
Colored PM manufactured by Kuraray Co., Ltd. having the transmittance characteristics shown in
There is an MA (acrylic) resin pellet (trade name: Acrypet HR-11160L), and desired characteristics were obtained by molding a lens element using this pellet. Also, in particular, this material is made up of a concave lens element 6
By using it for a (FIG. 2), it was possible to obtain the projection lens 7a having excellent contrast performance.

On the other hand, as a lens material for realizing the light transmitting means according to the prior art provided in the lens element of the projection lens 7b (FIG. 2) provided in the green image light projection tube 1b, for example, as shown in FIG. Co., Ltd. which has rate characteristics
Colored PMMA (acrylic) resin pellets manufactured by Asahi Kasei (trade name: Delpet 80R (color number: LM9070
1)), and desired characteristics were obtained by molding the concave lens element 6b using this pellet.

In order to enhance the color purity of the green image light, the peak energy wavelength λ _Gmax (=
Light _having a wavelength λ _GLmax (= 630 nm) of the sub-peak energy existing further on the longer wavelength side than the wavelength λ _Rmax of the peak energy of the red phosphor among the spurious components present on the longer wavelength side with respect to (545 nm). It is necessary to lower the light transmittance TGL with respect to. However, in the light transmitting means in the prior art, when this is done, the transmittance of light of the peak energy wavelength λ _Gmax (= 545 nm) is also lowered at the same time, so that the chromaticity of the green image light is slightly improved, On the other hand, it has been found that the brightness decreases and the brightness of white obtained when the three colors of red, green and blue are mixed is also decreased.

Therefore, the applicant of the present invention, based on the lens material according to the prior art, _uses the light _having the wavelength λ _GSmax of the sub-peak energy in the wavelength region shorter than the wavelength λ _Gmax (= 545 nm) of the peak energy of the green image light. Transmittance TGS
And the wavelength λ _Gmax (= 5 of peak energy of green image light)
Light having a wavelength λ _GLmax of sub-peak energy which is a spurious component existing in a wavelength range longer than 45 nm) and which is present in a wavelength range longer than the main wavelength λ _Rmax of the peak energy of the spectrum of the red image light. If the transmittance TGL ratio is less than or equal to% and what condition is satisfied, the brightness of white obtained when three colors of red, green, and blue are mixed is hardly reduced, and the chromaticity is further improved. It was verified by an experiment whether the improvement effect can be discriminated.

As a result, the decrease in light transmittance with respect to the wavelength λ _Gmax (= 545 nm) of the peak energy of the green image light is 10% or less of the light transmittance of the reference lens material, and TGL ≦ A light transmitting means satisfying the condition of TGS / 2 is provided with the projection lens 7b (FIG. 2).
Is provided in the lens element of the red image light projection tube 1a described above, in association with the light transmitting means provided in the lens element of the projection lens 7a, the red, green,
It was confirmed that further improvement of the chromaticity was obtained by visual observation without substantially lowering the brightness of white obtained when the three colors of blue were mixed.

Further, as a result of the examination conducted by the applicant,
As the green image light, blue green on the slightly shorter wavelength side is more preferable than selecting only a wavelength near the e-line (wavelength = 545 nm) which is originally deep green in the emission spectrum shown in FIG. It turned out that

Therefore, in this embodiment, the peak of the light transmittance of the light transmission means provided in the lens element of the projection lens 7b provided in the green image light projection tube 1b is determined by the wavelength λ of the peak energy of the green image light. _Gmax (= 545n
It was set on the shorter wavelength side than m).

As described above, as a lens material that can realize the light transmitting means provided in the lens element of the projection lens 7b provided in the green image light projection tube 1b, for example, the transmittance characteristics shown in FIG. ) Coloring P made by Kuraray
There is an MMA (acrylic) resin pellet (trade name: Acrypet HR-14132L), and desired characteristics can be obtained by molding a lens element using this pellet. Further, by using this material, in particular, for the concave lens element 6b (FIG. 2), the projection lens 7b having excellent contrast performance can be obtained.

By the respective pellets described above, FIG.
The concave lens element 6 shown in (1) was actually molded, and the focusing performance, color reproduction range, and white brightness were compared, and the results will be described below. First, the effect of this embodiment will be described based on the focusing performance of the projection lens 7 having the six-group configuration shown in FIG.

FIG. 17 shows a specific example of lens data that can be taken by the projection lens 7. The spherical system (FIG. 17 (a)) mainly dealing with the lens area near the optical axis and its outer peripheral portion are shown. The data is shown separately for the aspherical system (FIG. 17B). Here, the first, second, third, fourth and fifth lenses in the figure are the lens elements 101, 102, 103, 104 and 105 in FIG. 1, respectively, and the sixth lens is the concave lens element 6. The lens surfaces of these lens elements correspond to those in FIG.

First, the screen 8 has an infinite radius of curvature (that is, a plane), and the distance from the screen 8 to the first lens 101 along the optical axis is 1042.6 mm.
It is shown that the refractive index of the medium in the meantime is 1.0. Further, the radius of curvature of the S1 surface of the first lens 101 is 11
2.98 mm (center of curvature is on the phosphor screen side), first lens 10
The distance between the lens surfaces S1 and S2 of No. 1 along the optical axis is 8.87.
4 mm, and the refractive index of the medium between them is 1.49334
Is shown. In the same way, finally, the fluorescent screen 2 of the face panel 3 of the projection tube (cathode ray tube) 1 is finally shown.

Lens surfaces S1 and S2 of the first lens 101
Lens surfaces S3 and S4 of the second lens 102, lens surfaces S7 and S8 of the fourth lens 104, and the fifth lens 105.
Lens surfaces S9, S10 and the lens surface S of the sixth lens 6
As for No. 11, the aspherical coefficient is shown in FIG.

Here, the aspherical surface coefficients are coefficients when the lens surface shape is expressed by the equation shown in FIG. 17 (b). This expression represents the height (function of r) of the lens surface when the optical axis direction of the lens is taken as the Z axis, r is the radial distance from the optical axis of the lens, and RD is the radius of curvature. There is. Therefore, the coefficients CC, AE, AF, AG, A of this equation
If H is given, the height, that is, the shape of the lens is determined according to the above equation.

FIG. 18 is a view showing the focusing performance for the green image light (spectral distribution is shown in FIG. 8) of the projection lens 7 having the six-group structure in FIG. 1 described above, and the horizontal axis is the corner of the screen screen. The relative image height when 100% is set, and the vertical axis is 300 TV as a value indicating the focus performance.
The MTFs of the books (mean values of sagittal and meridional MTFs) are shown respectively. The larger the MTF value, the higher the focusing performance.

In the figure, the broken line shows the focusing performance of the projection lens by the green image light having the spectral distribution shown in FIG. Further, the alternate long and short dash line A shows the focusing performance when the concave lens element 6 shown in FIG. 1 has the transmittance characteristic shown in FIG. 14 as the light transmitting means in the conventional technique. Further, the solid line shows the focusing performance when the concave lens element 6 shown in FIG. 1 has the transmittance characteristic shown in FIG. 15 as the light transmitting means in this embodiment.

When the light transmitting means in this embodiment is used, the MTF is improved by about 1% (absolute value) on the average of all screens of the screen as compared with the case where the light transmitting means in the prior art is used. The reason is that the wavelength λ _GLmax (= of the sub-peak energy existing in the long wavelength side region of the green image light shown in FIG.
This is because the light transmittance of the light transmitting means for 630 nm) is halved compared to that of the prior art, so that the chromatic aberration generated in the enlarged image on the screen can be reduced.

Next, the effect of improving the color purity will be described. FIG. 19 is a chromaticity diagram for explaining the effect of expanding the color reproduction range, in which the vertical axis represents the y value and the horizontal axis represents the X value. As described above, the chromaticity points (x, y) of the image light of the projection tube having the characteristics shown in FIGS. 7, 8 and 9 are blue image light (0.126, 0.045) and red as described above. The image light is (0.6
52, 0.342) and the green image light is (0.322, 0.5).
78), and the larger the range surrounded by these three points, the larger the color reproduction range.

In FIG. 19, the alternate long and short dash line A indicates, as a light transmitting means in the prior art, the concave lens element 6 provided in the green image light projection tube having the transmittance characteristic shown in FIG. 12 shows the effect of expanding the color reproduction range when the concave lens element 6 provided in the projection tube for use has the transmittance characteristics shown in FIG. As a result, the chromaticity point of the green image light moves to (0.302, 0.639) and the chromaticity point of the red image light moves to (0.664, 0.335), respectively, and the concave lens element 6 is not colored. Compared with the case, the color reproduction range is expanded by 22% (area ratio).

Further, the solid line indicates, as the light transmitting means in this embodiment, the concave lens element 6 provided in the green image light projection tube has the transmittance characteristic shown in FIG. 15 and the red image light projection tube. The concave lens element 6 provided in FIG.
7 shows the effect of expanding the color reproduction range when the transmittance characteristics shown in FIG. As a result, the chromaticity point of the green image light moves to (0.281, 0.648) and the chromaticity point of the red image light moves to (0.667, 0.331), respectively, and the concave lens element 6 is not colored. 33% color reproduction range compared to the case
(Area ratio) has been expanded, and a significant improvement effect of + 50% is obtained compared to the conventional technology.

Further, a 5.33 inch raster is displayed on the fluorescent screen of the projection tube, and three colors of red, green and blue are mixed on the screen to obtain 60 inch white (color temperature 9300K + 0MPC).
The brightness obtained when an enlarged image of D and the chromaticity point (0.285, 0.294) is displayed, and the value of the cathode current passed through each projection tube are as follows.

First, as the light transmitting means in the prior art, the concave lens element 6 provided in the green image light projection tube is used as shown in FIG.
When the concave lens element 6 provided in the projection tube for red image light is provided with the transmittance characteristics shown in FIG. 4 and the transmittance characteristics shown in FIG.
9.5 (nt (= cad / m ² )), 112 (n in monochrome)
t), 35.5 (nt) for monochromatic red, 12 (n) for monochromatic blue
t). The cathode currents flowing through the projection tubes for green, red, and blue image lights are 0.42 (mA) and 0.31 respectively.
(MA), 0.40 (mA), and the sum total is 1.13 (m
It was A).

On the other hand, as the light transmitting means in this embodiment, the concave lens element 6 provided on the green image light projection tube is used.
15 has the transmittance characteristic shown in FIG. 15 and the concave lens element 6 provided in the red image light projection tube has the transmittance characteristic shown in FIG. .3 (nt), monochromatic green is 110.3 (nt), monochromatic red is 36.5 (nt), and monochromatic blue is 11.5 (nt).

At this time, the cathode current flowing through the green image light projection tube was 0.455 (mA), which was 8% higher than that of the prior art. The reason is that, in the emission spectrum of the green phosphor, the light transmittance for the wavelength λ _GLmax (= 630 nm) of the sub-peak energy in the long-wavelength side region is halved compared to that of the prior art, so an extra cathode current is passed. This compensates for the lack of brightness. Further, the cathode current flowing through the red image light projection tube is 0.335 (mA), which is 8% higher than that of the prior art. The reason for this is that the wavelength λ of the sub-peak energy in the wavelength region shorter than the main wavelength λ _Rmax (= 615 nm) of the emission spectrum of the red phosphor.
_The light transmittance for _RSmax (= 585 nm) is halved compared to that of the prior art, and the dominant wavelength λ _Rmax (= 615n).
The light transmittance of m) is reduced by about 2% in absolute value. Therefore, the shortage of brightness is compensated for by supplying an extra cathode current of the red image light projection tube. Further, since the cathode current flowing through the blue image light projection tube improves the color purity of the red image light and the green image light, it is possible to reduce the current distribution of the blue image light projection tube accordingly. 0.
It may be 35 (mA), which is 13% lower than that of the prior art. From the above, the total cathode current of the projection tubes for green, red, and blue image light is 1.14 (mA).
Is.

As described above, in this embodiment, the focus performance can be improved and the color reproduction range can be greatly expanded without increasing the sum of the cathode currents and without impairing the brightness, as compared with the prior art.

As another embodiment of the present invention for increasing the color reproduction range and improving the focus performance by improving the color purity of image light, a screen 8 shown in FIGS. 2 and 3 is provided with a light transmitting means. Is.

FIG. 20 is a perspective view showing another embodiment of the projection optical system according to the present invention, which relates to the screen 8 shown in FIGS. 2 and 3, 11 is an incident surface, and 12 is a Fresnel lens sheet. , 13 is a Fresnel lens, 14 is a vertically long lenticular lens, 15 is a lenticular sheet, 16 is a vertically long lenticular lens, 17 is a light diffusing material, 18 is a front sheet, and 19 is a light absorbing layer.

In this figure, the transmissive screen 8 is shown.
Fresnel lens sheet 11 and lenticular sheet 1
5 and the front seat 18 form a three-sheet structure. The Fresnel lens sheet 11 allows the enlarged image light incident from the incident surface 11 from the projection lens 6 shown in FIGS. 1 and 2 to be substantially parallel to the image light by the Fresnel lens 13 formed on the emission surface side. Convert to. The lenticular sheet 15 is made of a light diffusing material 17 and has an incident surface 14
Vertically long lenticular lenses 14 and 16 are formed corresponding to the light emitting surface 16 and the light emitting surface 16, respectively, and a light absorption layer 19 is vertically formed between the vertically long lenticular lenses 16 on the light emitting surface side. The substantially parallel image light emitted from the Fresnel lens sheet 11 is condensed by each of the vertically long lenticular lenses 14 on the incident surface side of the lenticular sheet 15 and emitted from the vertically long lenticular lens 16 on the light emitting surface side, whereby the horizontal direction of the screen is obtained. Light diffusing material 17 that is diffused into the interior of the lenticular sheet 15
Is diffused in the vertical direction of the screen.

In this embodiment, the front sheet 18 is further provided on the front surface (viewer side) of the lenticular sheet 15 to reduce the external light which deteriorates the contrast.

With the lenticular sheet 15, the
The image light diffused in the vertical direction is emitted to the outside through the front sheet 18, so that the image can be viewed from the outside. The front sheet 18 has a transmittance characteristic as shown in FIGS. 21 and 22. Have. That is, the light transmittance in the wavelength region shorter than the main wavelength λ _Bmax of the peak energy in the emission spectrum distribution of the blue image light is larger than the light transmittance T _Bmax of the peak energy in the main wavelength λ _Bmax , and the red image The dominant wavelength λ of the peak energy in the light emission spectrum distribution
Than _Rmax light transmittance in a wavelength region longer it is set to be smaller than the light transmittance T _Rmax at main wavelength lambda _Rmax of the peak energy. Further, a wavelength region between the _dominant wavelength λ _Bmax of the blue image light and the _dominant wavelength λ _Bmax of the green image light, the _dominant wavelength λ _Gmax of the green image light and the _dominant wavelength λ of the red image light.
The light transmittance in the wavelength region between _Rmax and _Rmax is kept low, and the light transmittances at the main wavelengths λ _Bmax , λ _Rmax , and λ _Gmax of the respective image lights are made substantially equal.

A part of outside light such as indoor illumination light passes through the front sheet 18, and a part of the outside light is absorbed by the light absorption layer 19 provided on the emission surface side of the lenticular sheet 15. Part of the light is reflected by the vertically long lenticular lens 16 provided on the exit surface side of the lenticular sheet 15, the vertically long lenticular lens 14 on the entrance surface side, and the like, and returns to the outside through the front sheet 18. Overlaps with the image light emitted from the front seat 18, which is one of the causes of the deterioration of the contrast performance. In this embodiment, the front seat 18 is
As shown in FIG. 21 or 22, the dominant wavelength λ of the image light is
_The transmittance is reduced in the wavelength region between _Bmax , λ _Rmax , and λ _Gmax , and the component in the wavelength region where external light is applied becomes 2
The external light reflected by the lenticular sheet 15 or the like and returning through the front sheet 18 is sufficiently reduced, and the contrast performance is significantly reduced as compared with the conventional screen. It will be suppressed.

As described above, in this embodiment, the front seat 1 having the transmittance characteristics shown in FIG. 21 or 22.
By providing No. 8, the influence of external light can be suppressed, and the fixed price of the contrast performance can be greatly reduced. Moreover, the transmittance characteristics provided on the front sheet 18 hinder the transmission of image light. It does not affect the color tone of the image displayed on the projection display device.

FIG. 23 is a perspective view showing still another embodiment of the projection optical system according to the present invention, which also relates to the screen 8 shown in FIGS. 2 and 3, and the portion corresponding to FIG. The same reference numerals are given and duplicate description is omitted.

In this drawing, in this embodiment, the screen 8 has a two-layer structure composed of a Fresnel lens sheet 11 and a lenticular sheet 15. The Fresnel lens sheet 11 and the lenticular sheet 15 are shown in FIG.
Although it has the same function as the Fresnel lens sheet 11 and the lenticular sheet 15 in, the lenticular sheet 15 is further provided with the transmittance characteristics shown in FIGS. 21 and 22.

According to this structure, a part of the external light is absorbed by the light absorption layer 19, but the other part is exposed from the vertically elongated lenticular lens 16 to the lenticular sheet 1.
5 penetrates and passes through this, and the longitudinal lenticular lens 14 or the Flemmer lens sheet 12 on the incident surface side.
Is reflected by the surface of the Fresnel lens 13 and passes through the lenticular sheet 15 again, and is emitted from the exposed portion of the vertically long lenticular lens 16 on the emission surface side, which overlaps the image light emitted from the lenticular sheet 15. However, in this embodiment, the ambient light is attenuated by the lenticular sheet 15 twice, so that the degradation of the contrast performance due to the ambient light can be significantly reduced. become. Moreover, the transmittance characteristic provided on the lenticular sheet 15 does not affect the transmission of image light, and therefore does not affect the color tone of the image displayed on the projection display device.

[0084]

As described above, according to the present invention,
The focus performance and the contrast performance can be improved and the quality of the displayed image can be improved without lowering the brightness of the displayed image.

[Brief description of drawings]

FIG. 1 is a sectional view showing an arrangement of a projection tube and a projection lens in a projection optical system according to the present invention.

FIG. 2 is a sectional view showing a configuration of a first embodiment of a projection optical system according to the present invention.

FIG. 3 is a sectional view showing a main part of an embodiment of a projection type image display device according to the present invention.

FIG. 4 is a diagram showing relative luminous efficiency characteristics in a visual field of 2 ° and a visual field of 10 °.

FIG. 5 is a diagram showing spectral tristimulus values in a visual field of 2 °.

FIG. 6 is a diagram showing spectral tristimulus values in a visual field of 10 °.

FIG. 7 is a diagram showing an emission spectrum distribution of a red phosphor used in a red image light projection tube.

FIG. 8 is a diagram showing an emission spectrum distribution of a green phosphor used in a green image light projection tube.

FIG. 9 is a diagram showing an emission spectrum distribution of a blue phosphor used in a blue image light projection tube.

FIG. 10 is a diagram showing a transmittance characteristic of a conventional light transmitting means used for a projection lens of a blue video light projection tube.

FIG. 11 is a diagram showing the transmittance characteristics of the light transmitting means used in the projection lens of the blue image light projection tube in the first embodiment of the present invention.

FIG. 12 is a diagram showing a transmittance characteristic of a conventional light transmitting means used for a projection lens of a red image light projection tube.

FIG. 13 is a diagram showing the transmittance characteristic of the light transmitting means used in the projection lens of the red image light projection tube in the first embodiment of the present invention.

FIG. 14 is a diagram showing a transmittance characteristic of a conventional light transmitting means used for a projection lens of a green image light projection tube.

FIG. 15 is a diagram showing the transmittance characteristics of the light transmitting means used in the projection lens of the green image light projection tube in the first embodiment of the present invention.

FIG. 16 is a characteristic diagram showing the relationship between the cathode current and the tube surface luminance of each of the red and green blue image light projection tubes.

17 is a diagram showing lens data in the projection lens shown in FIG.

FIG. 18 is a diagram showing a comparison of the focusing performance of the projection lens in the case where the light transmitting means is not provided, in the case where the conventional light transmitting means is used, and in the case of the first embodiment of the present invention.

FIG. 19 is a diagram showing a color improvement effect of the first embodiment of the present invention in comparison with a case where no light transmission means is provided and a case where a conventional light transmission means is used.

FIG. 20 is a perspective view showing a main part of a second embodiment of the projection optical system according to the present invention.

FIG. 21 is a diagram showing a specific example of the transmittance characteristics of the light selective transmission unit on the front sheet in FIG. 20.

22 is a diagram showing another specific example of the transmittance characteristics of the light selective transmission unit in the front sheet in FIG.

FIG. 23 is a perspective view showing a main part of a third embodiment of the projection optical system according to the present invention.

[Explanation of symbols]

1 Projection tube 1a Projection tube for red image light 1b Green image light projection tube 1c Blue image light projection tube 2 fluorescent screen 2a Red phosphor screen 2b Green phosphor screen 2c Blue phosphor screen 3 face panels 3a, 3b, 3c Face panel 4 Refrigerant 4a, 4b, 4c Refrigerant 5,5a, 5b, 5c bracket 6,6a, 6b, 6c concave lens element 7,7a, 7b, 7c Projection lens 8 screen 9 Folding mirror 10 cabinets 11 incident surface 12 Fresnel lens sheet 13 Fresnel lens 14,16 Vertical lenticular lens 15 Lenticular sheet 17 Light diffusing material 18 front seat 19 Light absorbing layer

Continued front page    (72) Inventor Kazunari Nakagawa             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Visual Information Media Division             Within (72) Inventor Tomoharu Nagiri             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Visual Information Media Division             Within (72) Inventor Naoyuki Ogura             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Visual Information Media Division             Within (72) Inventor Chihiro Nagakawa             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Hitachi, Ltd. Visual Information Media Division             Within F-term (reference) 2H087 KA06 KA07 PA06 PA17 PB06                       QA02 QA12 QA22 QA25 QA37                       QA41 QA46 RA05 RA12 RA13                 2K103 AA06 AA16 AA17 AA18 AA25                       AB01 AB04 BB01

Claims (5)

[Claims] 1. A plurality of image generation sources corresponding to image lights of three primary colors of red, blue, and green, a projection lens provided for each image generation source, and an image displayed on the image generation source is enlarged. In a projection optical system including a screen for projection, the spectral distribution of green image light generated from the green image generation source has a plurality of sub-peak energy wavelengths in addition to the main wavelength λ _Gmax of peak energy. The projection lens provided in the red image generation source, the wavelength λ of the peak energy in the spectral distribution of the red image light.
_Rmax is provided with light transmitting means for attenuating the energy in the short wavelength side region as compared with the energy in the long wavelength side region, and the projection lens provided in the green image generation source,
For the wavelength λ _Gmax of the peak energy of green image light,
Wavelength of sub-peak energy in short wavelength region λ _GSmax
At the wavelength λ _GLmax of the sub-peak energy in the long wavelength side region of the green image light existing in the longer wavelength side region than the main wavelength λ _Rmax of the peak energy of the spectrum of the red image light. A projection optical system provided with a light transmitting means having a light transmittance TGL and a relationship of TGL ≦ TGS / 2. 2. The projection optical system according to claim 1, wherein the projection lens provided in the red image generation source has a short wavelength with respect to the wavelength λ _Rmax of the peak energy of the spectral distribution of the red image light. a light transmittance TRS wavelength lambda _RSmax sub peak energy in the side areas, the wavelength lambda _RLmax sub peak energy in the long wavelength side region light transmittance T
A projection optical system characterized in that a light transmission means having a relationship of TRS ≦ TRL / 3 with RL is provided. 3. The projection optical system according to claim 1, wherein the image generation source is a projection tube, and the lens is arranged at a position closest to the fluorescent screen of the projection tube in the projection lens. A projection optical system characterized in that the element is provided with the light transmitting means. 4. The projection optical system according to claim 1, wherein the screen has a peak energy wavelength of a spectral distribution in image light from each of a plurality of image sources corresponding to red, blue and green. A projection optical system characterized by comprising a light beam transmitting means for attenuating energy in wavelength regions other than λ _Rmax , λ _Bmax and λ _Gmax . 5. A projection type image display device comprising the projection optical system according to claim 1. Description: