JP2000241878A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type display device capable of still more improving the using efficiency of light emitted from a lamp, and also, capable of irradiating a projection screen with high luminance and high uniformity, as for the projection type display device using a parabolic reflector and a lamp as a light source. SOLUTION: A condensing lens 2 is arranged ahead of the parabolic reflector 1, and the light from a DC driving lamp 9 is slightly refracted in a converging direction. By this method, the degree of dispersion is reduced, the collimated light is corrected to weak convergent light, and the luminance distribution within an effective angle extent is controlled to become the maximum. Thus, the using efficiency of the light emitted from the DC driving lamp 9 is improved, and the higher screen illuminance is obtained by the lamp having the same output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a parabolic mirror and a DC lighting lamp as light sources, uniformly illuminates a display element via a fly-eye lens and a relay lens, and projects image information of the display element on a screen. To a projection display device.

[0002]

2. Description of the Related Art FIG. 5 is a schematic diagram for explaining an example of a conventional general projection type display device. The lamp 28 disposed near the focal point irradiates the fly-eye lens 22 with substantially parallel light by the reflection action of the parabolic reflector 21.
Each of the frames of the fly-eye lens 22 has a similar shape to the display element 25, and the image of the frame of the fly-eye lens 22 has a magnification β via a fly-eye lens 23 and a relay lens 24.
And are superimposed by the number of frames.

The light beam emitted from the lamp 28 is split into a plurality of light beams by the fly-eye lens 22 and converges at the position of the fly-eye lens 23 to form a plurality of light source images. Since the display element 25 is illuminated with a plurality of light source images, uniform illumination can be obtained. The uniformly illuminated image of the display element is magnified by a projection lens 26 and a screen 27.
Projected to

In a fly's eye optical system, when the angle of a ray incident on the fly's eye is nearly parallel to the optical axis, the ray can be used effectively and an effective angle range indicating the range in which the ray can be effectively used is defined. can do. Therefore,
If the angle exceeds a certain angle, that is, out of the effective angle range, the light beam becomes invalid. Light rays from a point light source at a parabolic focal point become light beams parallel to the optical axis, but light rays emitted from other than the focal point do not become light rays parallel to the optical axis. This is because the actual light source has a finite size.

[0005]

Incidentally, there are a DC drive system and an AC drive system for driving the lamp. Compared with the AC driving method, the DC driving method has a feature that the brightness distribution of the light source is smaller and the light source approaches the point light source and the screen becomes brighter. The direct-current drive system has a characteristic that the luminance distribution is biased toward one side of the electrode with respect to the center, as shown in FIG. Therefore, as described above, although it is closer to a point light source as compared with the AC drive method, there is a problem that a lot of light rays that are reflected by the parabolic reflector and are not parallel to the optical axis are emitted and light use efficiency is reduced. is there.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem. In a projection type display device using a light source composed of a parabolic reflector and a lamp, the efficiency of use of light emitted from a DC-driven lamp is further improved. An object of the present invention is to provide a projection display device capable of irradiating a projection screen with high luminance and high uniformity.

[0007]

In order to achieve the above object, a projection display device according to the present invention comprises a parabolic mirror and light emitted from a light source comprising a DC lighting lamp disposed at a focal point of the parabolic mirror. A plurality of light source images are obtained by entering a fly-eye lens, and the display element is uniformly illuminated by passing through a relay lens system, and an enlarged image of the image information of the display element is obtained on a screen by a projection lens. In the apparatus, a condenser lens having a positive refractive power is arranged in front of the parabolic mirror, and the brightness distribution characteristic of the lamp, which is biased toward the cathode on the side of the opening of the parabolic mirror, is defined by the fly-eye. Correction has been made so that the number of rays entering the effective angle range to the lens increases.

[0008]

According to the above construction, the utilization ratio of the light emitted from the lamp is improved, and the screen can be illuminated with higher luminance and higher uniformity as compared with the prior art.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, the luminance distribution of the DC drive method will be described. FIG. 1 is a diagram showing a luminance distribution of a DC-driven lamp. Between the cathode and the anode, there is a high brightness peaking at a position near the cathode side, and the brightness drops sharply on the cathode side. On the other hand, the anode side has a characteristic of gradually decreasing.

FIG. 2 shows an optical path when a DC-driven lamp is arranged at the focal position of a parabolic reflector. The lamp is mounted so that the peak value of the luminance distribution coincides with the focal position of the parabolic reflector. The light emitted from the focal point F is reflected by the parabolic reflector and becomes parallel light. Light rays on the anode side having a large luminance distribution are reflected by the parabolic reflector to become divergent lights, and the light rays in this portion cannot be used.

FIG. 3 is a schematic diagram showing an embodiment of a projection display device according to the present invention. 5, the fly-eye lenses 3, 4, the relay lens 5, the transmissive display element 6, the projection lens 7 and the screen 8 correspond to the fly-eye lenses 22, 23, the relay lens 24, the display element 25, the projection lens 26 and It has the same configuration as the screen 27.
A condenser lens 2 having a positive refractive power is provided in front of a parabolic reflector 1 having a DC drive lamp 9 disposed at a focal position. By arranging the convex condenser lens 2 in this manner, the light rays emitted from the parabolic reflector 1 are converged weakly as a whole, thereby increasing the light use efficiency.

FIG. 4 is a diagram showing conversion of luminance distribution into an effective angle range by a condenser lens. The range of the dotted line position is the effective angle range, and when a light beam enters the fly-eye lens 3 at an angle in this range, it irradiates the screen. Outside this range, the angle becomes more convergent or divergent, and does not contribute to the illuminance of the screen. FIG. 4A shows a conventional configuration in which a condenser lens is not inserted. The luminance sharply decreases on the converging side, but the luminance decreases gently on the diverging side, and the portion protruding from the dotted line is shown. The ratio is large.

In the present invention, the light emitted from the focal point and reflected by the parabolic reflector 1 becomes parallel light, but bends to the converging side by the condenser lens 2. A condenser lens having a refracting power such that a part of the light beam slightly exceeds the range of the dotted line on the converging side is used. On the other hand, light emitted from a position slightly shifted from the focal point of the light source is reflected in a direction diverging on the paraboloid, but is bent by the condenser lens 2 in a direction parallel to the optical axis. FIG. 4B shows the characteristics when a condenser lens is inserted, and the characteristics are corrected so that the convergence side and the divergence side become substantially symmetric about the peak. In this way, the degree of divergence of the light source is reduced, the parallel light is corrected to a weak convergent light, and the luminance distribution falling within the effective angle range is maximized. Thereby, the effective utilization rate of the light emitted from the DC driving lamp 9 can be improved.

Next, a comparative example will be described with respect to the difference in the light collection rate between the device of the present invention and the conventional device. The sum of the light rays emitted from the light source is A, and the sum of the light rays incident on a display element such as a liquid crystal is B, and the light collection rate C = B / A is defined. The present invention has the same configuration as each optical member of each conventional optical device except that a condenser lens is inserted behind the parabolic mirror. The parabolic mirror used had a = 50.8 in the formula of y = 1 / (4a) × x ² , that is, an aperture diameter of 50.8 mm. The focal length of the condenser lens is f = 300 mm. The arc length between the anode and the cathode of the light source is 2 mm, and the distance between the focal point of the parabolic mirror and the cathode is 0.2 mm. The luminance distribution is a DC lighting lamp biased to the cathode side, and the opening side of the parabolic mirror is the cathode. As a result of the measurement as described above, a light collection rate of 18.4% can be obtained with the conventional apparatus (only the parabolic mirror), and 27.6% can be obtained with the apparatus of the present invention (parabolic mirror + condenser lens). Was. As a result, the light collection rate of the device of the present invention was 27.6 / 18.4 =
1.5 times improvement in efficiency was realized.

In the above embodiment, an example of a transmissive display element has been described. However, it is needless to say that the present invention can be applied to a reflective display element.

[0016]

As described above, according to the present invention, a plurality of light source images are formed by making light emitted from a light source composed of a parabolic mirror and a lamp disposed at the focal point of the parabolic mirror incident on a fly-eye lens. In a projection type display device in which a display element is uniformly illuminated by passing through a relay lens system and an enlarged image of image information of the display element is obtained on a screen by a projection lens, a positive refraction is provided behind a parabolic mirror. A condenser lens for power is arranged to correct the luminance distribution characteristic having a bias on the cathode side from which the lamp emits, so that the number of rays falling within the effective angle range to the fly-eye lens is increased.
Therefore, the effective use rate of light is improved compared to the past,
With a DC-driven lamp of the same output, there is an effect that the screen can be further illuminated with high brightness and high uniformity without increasing the aperture.

[Brief description of the drawings]

FIG. 1 is a diagram showing a luminance distribution of a DC-driven lamp.

FIG. 2 is a diagram for explaining an optical path when a DC-driven lamp is arranged at a focal position of a parabolic reflector.

FIG. 3 is a schematic view showing an embodiment of a projection display device according to the present invention.

FIG. 4 is a diagram for explaining conversion of luminance distribution into an effective angle range by a condenser lens.

FIG. 5 is a schematic diagram for explaining an example of a conventional general projection display device.

[Explanation of symbols]

 1, 21 parabolic reflector 2 condenser lens 3, 4, 22, 23 fly eye lens 5, 24 relay lens 6, 25 transmissive display element 7, 26 projection lens 8, 27 screen 9, direct current Drive lamp

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/74 H04N 5/74 A (72) Inventor Hiroyuki Omichi 2-14-9 Tamagawadai, Setagaya-ku, Tokyo No.F-term in Kyocera Corporation Tokyo Yoga Office (reference) 2H052 BA02 BA03 BA09 BA14 2H088 EA13 HA21 HA24 HA25 HA28 MA04 MA06 2H091 FA26X FA26Z FA29Z FA41Z LA16 LA18 MA07 5C058 BA06 EA12 EA13 EA51 5G435 AA02 DD03 DD03 GG46

Claims (1)

[Claims] 1. A light source comprising a parabolic mirror and a DC lighting lamp disposed at the focal point of the parabolic mirror is incident on a fly-eye lens to obtain a plurality of light source images. In a projection display device that uniformly illuminates the display element by passing through, and obtains an enlarged image of image information of the display element on a screen by a projection lens,
A condenser lens having a positive refractive power is arranged in front of the parabolic mirror, and a luminance distribution characteristic having a bias toward the cathode side on the opening side of the parabolic mirror of the lamp is provided to the fly-eye lens. A projection display device, wherein correction is performed so that light rays falling within an effective angle range increase.