JPH05165098A - Projection type display device and optical guide plate - Google Patents

Abstract

PURPOSE:To provide a projection type display device, in which the characteristics of the collimator part of a light source are improved and with which a large screen displaying with less unevenness in the brightness is achieved. CONSTITUTION:The diffusion light from a light source 1 is collimated by a collimator lens 2, and only parallel beams of light are admitted to pass through by a light guide plate 3, converged by a condenser lens 4, and cast onto a transmissive display body 5, and the light having penetrated is projected by a projection lens 6 onto a screen 7, wherein unevenness in the brightness due to eclipse is avoided by enhancing the parallelism by the light guide plate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device for enlarging and projecting a display image of a display device onto a large screen using an optical system, and a light guide plate such as an optical waveguide having a strong directivity.

[0002]

2. Description of the Related Art Conventionally, a projection type display device of this type has a structure as shown in FIG. 7 (Japanese Patent Laid-Open No. 62-159).
120 gazette). In FIG. 7A, the light diverged from the light source 51 is collimated by the collimator lens 52, illuminates the transmissive display body 53 such as a liquid crystal light valve, projects the light by the projection lens 54, and projects it on the screen 55. The image was being formed. In order to make the brightness on the screen 55 uniform, the luminous flux from the light source 51 for illuminating the transmissive display body 53 is distributed so as to have an equal illuminance on the transmissive display body 53, and moreover, the projection lens 54 is not vignetted. It is necessary to enter the entrance pupil of. On the other hand, since the light source 51 has a size, it is impossible to completely place the light source 51 at the focal point of the collimator lens 52, and the light flux emitted from the transmissive display body 53 is as shown by the solid line in the figure. , A to B regions show a distribution with a certain spread. Therefore, unless the area of the entrance pupil plane of the projection lens 54 is made larger than this distribution, the image on the screen 55 will have uneven brightness. Therefore, normally, as shown in FIG. 7B, a condenser lens 56 is inserted and installed between the collimator lens 52 and the transmissive display body 53 to collect light. As a result, the area where the light is condensed and spread is reduced, but it cannot be reduced below a value related to the size of the light source 51. Therefore, in order to eliminate the uneven brightness, there is a problem that the optical load such as increasing the aperture of the projection lens 54 or changing the light source 51 to a point light source is imposed.

Further, as will be described later, the present invention uses a light guide plate. Conventionally, this type of light guide utilizes the reflection of the end face of the light transmitting portion to propagate light to a distant place. It was FIG. 8 shows an example of the light guide 33 found in JP-A-60-203919 and JP-A-60-212430. In FIG. 8 (a), the light guide 33 includes a light-transmitting portion 31 made of a solid having a high transmittance such as acrylic and glass, and a metal such as aluminum, gold and silver or a white pigment such as titanium oxide around the light transmitting portion 31. The reflective film 32 has a high reflectance and covers the acrylic resin. FIG. 8B is also an example of the light guide 33, and a reflective film 35 made of a metal having a high reflectance such as aluminum is formed on the inner surface of a cylindrical solid 34 made of a resin molded product such as acrylic having a hollow inside. Is provided. The light guide 33 may have a structure in which a reflective film 35 having a high reflectance is provided on the outer surface of a solid having a high transmittance.

FIG. 9 shows the structure of an optical fiber as a light guide (edited by Ohmsha, S. Shimada, "Optical Communication Technology Reader").
other). The optical fiber 61 has a concentric double structure called a core 62 and a clad 63, and light mainly passes through the core 62 at the center of the optical fiber 61. The clad 63 surrounds it. The refractive index n ₀ of the core 62 is slightly larger than the refractive index n _C of the clad 63. Therefore, when the end face of the optical fiber 61 is irradiated with light, light having a propagation angle smaller than the critical angle θ _C propagates in the optical fiber 61 while repeating total reflection at the boundary between the core 62 and the clad 63. Here, the numerical aperture NA means the sine of the maximum light receiving angle that the optical fiber 61 can receive with respect to incident light from the outside. NA = n ₀ · sin θ _C = SQRT (n ₀ ² −n _C ² )

[0005]

As described above, since the conventional light guide 33 (optical fiber 61) propagates light by reflection, the received light follows its optical characteristics and is basically so strong. It does not show directivity and propagates light in all directions. Therefore, it is difficult to realize the light guide 33 having a strong directivity.

A first object of the present invention is to provide a means for improving the characteristics of the collimator portion of the light source and realizing a projection type display device capable of displaying a large screen with less uneven brightness at low cost.

A second object of the present invention is to provide light with a strong directivity,
Specifically, it is to realize a light guide plate for realizing parallel rays. Therefore, the configuration is such that light other than the parallel component from the scattered light or the quasi-parallel light is absorbed or the reflectance is reduced and attenuated.

[0008]

A projection type display device according to the present invention is a projection type display device comprising a light source, a collimator, a condenser lens, a light transmission type display member and a projection lens. A light guide that allows only parallel light to pass through the axis is inserted and arranged.

The light guide plate according to the present invention has a linear light transmitting portion, a light absorbing structure or a low reflectance structure portion or a light absorbing structure around the light transmitting portion in a direction perpendicular to the optical axis, and A light guide element is formed by providing a coating as a low reflectance structure portion, and a plurality of light guide elements are laminated so that the directions of the light guide elements are all parallel.

[0010]

In the projection type display device according to the present invention, the light passing through the collimator lens becomes only parallel light by the light guide plate and is condensed by the condenser lens, so that there is no uneven brightness due to vignetting. Further, since the light guide plate according to the present invention allows only the light parallel to the optical axis to pass through, the parallelism of the light entering the condenser lens is improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the projection type display device according to the present invention. In FIG. 1, reference numeral 1 is a light source such as a metal halide lamp. A collimator lens 2 collimates the divergent light from the light source 1. Reference numeral 3 is an optical guide plate that allows only parallel components of the output light from the collimator lens 2 to pass therethrough. Reference numeral 4 is a condenser lens for collecting parallel light. Reference numeral 5 is a transmissive display such as a liquid crystal light valve. Reference numeral 6 is a projection lens for enlarging the display of the transmissive display body 5. Reference numeral 7 is a screen for forming a projected image. In the projection display device of the present invention configured as described above, the light diverged from the light source 1 is converted into parallel light by the collimator lens 2 and further passed through the light guide plate 3 to improve the parallelism characteristic. It is input to the condenser lens 4 for condensing. The light flux condensed by the condenser lens 4 is modulated by the transmissive display body 5 such as a liquid crystal light valve on the way, is input to the projection lens 6, and is enlarged and projected on the screen 7. The light from the light source 1 is input to the condenser lens 4 with a high degree of parallelism, so that it is condensed in a region where the distribution of the light flux is small (a region of A to B meshes). Therefore, by setting the size of the entrance pupil of the projection lens 6 to be equal to or larger than this condensing area, uneven brightness due to vignetting can be avoided.

FIG. 2 shows another embodiment of the present invention, which is a light source 1
Is separated into three primary colors (red, green, and blue), each of which is modulated by the transmissive display 5 and then combined again to realize color display. In FIG. 2, reference numeral 1 is a light source such as a metal halide lamp. Reference numerals 4 ₁ to 4 ₃ are condenser lenses, which are installed corresponding to each of the _three primary colors. Reference numeral 3 is a light guide plate that allows only parallel light to pass through the optical axis. Reference numerals 5 _{1 to} 5 ₃ are transmissive display bodies for modulating light. 6 is a projection lens, and 7 is a screen for forming a projected image. 8 _{1-8 4} is a dichroic mirror for color separation or synthesis. 9
Is a total reflection mirror for changing the optical path. Reference numeral 10 is a filter for blocking passage of unnecessary light components such as infrared rays and ultraviolet rays. Reference numeral 11 is a reflecting mirror formed of a parametric mirror or the like for producing parallel light in the visible region from a point light source. A parallel light source unit 12 includes a light source 1, a reflecting mirror 11, an optical filter 10 and an optical guide plate 3.

An outline of the operation of the projection type display device configured as above will be described. Since the light source 1 is installed at the focal point of the reflecting mirror 11 composed of a parabolic object mirror, part of the light emitted from the light source 1 is divergent light, and part of the light is reflected by the reflecting mirror 11 to become parallel light, and infrared rays are emitted. The light in the unnecessary wavelength band is cut by the filter 10 that cuts ultraviolet rays and the like. Further, by passing through the light guide plate 3, only parallel rays having a high degree of parallelism with respect to the optical axis are output from the parallel light source unit 12. Parallel light source unit 12
The light emitted from the device is first color-separated, modulated by the transmissive display body 5, and then color-synthesized, and then enters the projection lens 6 to form an image on the screen 7 for display. Specifically, the light from the light source 1 passes through the total reflection mirror 9 ₁ by the dichroic mirror 8 ₁ that reflects blue light, and further passes through the condenser lens 4 ₁ for condensing to the transmissive display body 5 ₁ . The supplied blue light is subjected to predetermined light modulation, and a blue component image B is output. The light passing through the blue-reflecting dichroic mirror 8 ₁ is reflected only on the green by the dichroic mirror 8 ₂ which reflects green, and is supplied to the transmissive display body 5 ₂ through the condenser lens 4 ₂ for condensing. It receives light modulation and outputs a green component image G. The light that has passed through the dichroic mirror 8 ₂ that reflects the green color becomes red as a result, is supplied to the transmissive display body 5 ₃ through the condenser lens 4 ₃ for condensing, undergoes predetermined light modulation, and outputs the red component image R. To do. The dichroic mirror 8 ₃ has blue transmission and green reflection characteristics, and combines the blue component image B and the green component image G,
It is input to the projection lens 6 passes through the dichroic mirror 8 _4. The red component image is reflected by the total reflection mirror 9 ₂ , reflected by the red reflection dichroic mirror 8 ₄ and incident on the projection lens 6. As a result, the lights separated into the three primary colors are combined again by the dichroic mirror 8 ₄ to display a color image on the screen 7. The above is the outline of the operation of the projection display apparatus of the present invention. Since the light guide plate 3 is inserted to improve the parallelism,
The condenser lens 4 can sufficiently collect the light.

FIG. 3 shows an embodiment of the light guide plate used in the present invention. FIG. 3 (a) shows an outline of the appearance of the light guide plate, and FIG. 3 (b) shows the light guide forming the light guide plate. The element is shown. 3 (c) and 3 (d) are front sectional views showing detailed examples of the light guide element and P _{1 of} FIG. 3 (c).
FIG. 6 is a vertical sectional view taken along line P ₂ . In FIG. 3A, 2
Reference numeral 3 is a light guide element that transmits light. Reference numeral 24 is an optical guide plate constituted by bundling the optical guide elements 23 in parallel with the optical axis, and the thickness thereof is indicated by L. Figure 3
(B) is an external appearance of the light guide element 23, and 21 is a light transmitting portion, which is a region for transmitting light, and is formed of a resin such as glass or acrylic that transmits light, or there is no physical It is configured in a hollow state. Reference numeral 22 denotes an absorber layer for absorbing light, a horizontal sectional view of which is shown in FIG. 3 (c) and a vertical sectional view thereof is shown in FIG. 3 (d). Next, the characteristics of the light guide plate 24 having such a configuration will be described.

In FIG. 3D, the light P entering in parallel to the optical axis (X-Y) of the light transmitting portion 21 of the light guide element 23.
Goes straight without being affected by the absorber layer 22 around the light guide element 23. Of the light Q having an angle with respect to the optical axis, the light entering from point A (incident angle θ ₁ with the optical axis) is
First, it enters the light transmitting portion 21 at point B, is refracted by the refractive index of the light transmitting portion 21 (refraction angle is θ ₂ ), and proceeds from B to C. Point C is a contact point between the light transmitting portion 21 and the absorber layer 22, and the incident angle θ ₃
The light entering the absorber layer 22 at is absorbed in the process of proceeding in the direction of C → D at the refraction angle θ ₄ according to the refractive index of the absorber layer 22,
Attenuates and virtually disappears. Further, although the reflectance is set to be small at the point C, in principle, the reflectance is largely attenuated according to the reflectance, and the C-E proceeds at the reflection angle θ ₅ . At point E, similarly to point C, the light incident at the incident angle θ ₆ travels through E → F and the absorber layer 22 at the refraction angle θ ₇ and is absorbed and disappeared. Go to E → G at ₈ . Such reflection and refraction are performed by the length L of the light guide element 23.
By repeating the above, the light having an angle with respect to the optical axis is finally attenuated and substantially disappears. That is,
Only light parallel to the optical axis can pass through the light guide element 23. The parallelism can be improved by increasing L / D _A when the diameter of the light transmitting portion 21 is D _A. Figure 3 (a)
Since a large number of such light guide elements 23 are bundled in the optical axis direction, even if quasi-parallel light or light in various directions enters the IN side, only parallel light is output to the output side.

FIG. 4 shows another embodiment of the light guide plate of the present invention. FIG. 4 (a) is a front sectional view and FIG. 4 (b) is P ₁
A vertical cross-sectional view taken along line -P ₂ shows the structure of a light guide element 23 that constitutes a light guide plate. 4 (a), (b)
Reference numeral 26 denotes an interface between the light transmitting portion 21 and the absorber layer 22, which is a sanded surface, and is formed by applying black paint such as black ink with a matte low reflectance. It is characteristically preferable that the refractive index of the paint is larger than that of the light transmitting portion 21. With such a configuration, light other than the parallel components is absorbed and only parallel rays are output. The absorber layer 22 can be formed by mixing fine particles that absorb specific light of blue to red into glass. Further, as shown in FIG. 4, both the light absorption structure by the absorber layer 22 and the low reflectance structure in which the matte black paint is applied to the interface 26 are provided, but it is clear that either one may be used. Is.

FIG. 5 shows still another embodiment of the light guide plate 24 of the present invention. FIG. 5 (a) is a perspective view showing a part of the light guide plate 24, and FIG. 5 (b) is a light guide plate 24. It is a perspective view which shows the structure of the light guide element 23 which comprises. A feature is that a honeycomb structure having a regular hexagonal shape and a hollow cross-sectional shape which is convenient for dense mounting is used, and the function is the same as that of the embodiment of FIG. Moreover, the cavity wall is shown in FIG.
It is also conceivable to sand sand and apply a non-reflective paint.

FIG. 6 shows still another embodiment of the light guide plate 24 of the present invention. FIG. 6 (a) is a perspective view showing a part of the light guide plate 24, and FIG. 6 (b) is a light guide plate 24. The structure of the light guide element 23 that constitutes the above is shown. The light transmitting portion 21 is characterized by using a light transmitting solid such as glass or acrylic, and the function is the same as in the case of the embodiment of FIG. In this configuration, a configuration in which an optical fiber is used for the light transmitting portion 21 is conceivable, and L / D _A between the diameter D _A and the length L of the light transmitting portion 21 of the light guide element 23 can be easily increased. It is easy to obtain high quality parallel light.

[0019]

In the projection type display device according to the present invention, the light guide plate for passing only parallel light with respect to the optical axis between the collimator lens and the condenser lens is inserted and arranged, so that the parallelism of the light source is improved. Therefore, the condenser lens can sufficiently collect light. As a result, it is possible to reduce the diameter of the projection lens for realizing an image with less unevenness in brightness, and it is possible to reduce the size and cost of the projection lens. Furthermore, the simplification of the light source optical system, the extension of the lamp life, and the like can achieve downsizing and high reliability of the device.

The light guide plate according to the present invention has a linear light transmitting portion, and a light absorbing structure or a low reflectance structure or a light absorbing structure and a low reflection around the light transmitting portion in the vertical direction. Since a light guide element is configured by providing a coating as a rate structure portion, and a plurality of light guide elements are laminated so that all the directions of the light guide elements are parallel to each other, it is only necessary to insert the light guide element vertically to the output side of the parallel light source. Since a high-quality parallel light beam can be obtained, there is an advantage that the optical system can be provided in a simple, small size and at low cost.

The scope of application includes measuring instruments such as spectrometers,
A general-purpose collimator optical component, various projectors that require a parallel light source, and the like are considered. Further, the light guide plate of the present invention functions only by being inserted into the light source, and is considered to be applied in various areas as a general-purpose element, and the influence of the present invention as a component that can easily obtain high-quality parallel light. The effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a projection display device according to the present invention.

FIG. 2 is a diagram showing the configuration of another embodiment of the projection display device according to the present invention.

FIG. 3 is an explanatory diagram of an embodiment of a light guide plate according to the present invention.

FIG. 4 is an explanatory view of another embodiment of the light guide plate according to the present invention.

FIG. 5 is an explanatory view of still another embodiment of the light guide plate according to the present invention.

FIG. 6 is an explanatory view of still another embodiment of the light guide plate according to the present invention.

FIG. 7 is a diagram illustrating the principle of a projection display device in the related art.

FIG. 8 is an explanatory view showing a conventional light guide.

FIG. 9 is an explanatory diagram showing a conventional light guide.

[Explanation of symbols]

 1 Light Source 2 Collimator Lens 3 Light Guide Plate 4 Condenser Lens 5 Transmission Type Display 6 Projection Lens 7 Screen 8 Dichroic Mirror 9 Total Reflection Mirror 10 Filter 11 Reflector 12 Parallel Light Source Unit 21 Light Transmission Part 22 Absorber Layer 23 Light Guide Element 24 Light guide plate 26 Interface between light transmitting part and absorber layer (sanded surface)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigenobu Sakai 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A light source, a collimator lens for collimating the light from the light source, a condenser lens for condensing the light from the collimator lens, a transmissive display member for receiving the light from the condenser lens, and the transmission. In a projection display device comprising a projection lens for projecting light that has passed through a shape display body onto a screen, an optical guide plate that allows only parallel light to pass through the optical axis is inserted and arranged between the collimator lens and the condenser lens. A projection display device characterized by the above. 2. A linear light-transmitting portion, and a light-absorbing structure portion or a low-reflectance structure portion or a light-absorbing structure and a low-reflectance structure portion around the light-transmitting portion in a direction perpendicular to the optical axis. A light guide plate, characterized in that a light guide element is formed by providing a coating, and a plurality of the light guide elements are laminated so that all directions of the light guide elements are parallel.