JPH02262185A - Projection type display device - Google Patents

Abstract

PURPOSE:To reduce the aperture of a projecting lense, to facilitate the aligning of the lenses with respect to a display panel and to improve display quality by forming first microlenses and second microlenses on both surfaces of a translucent plate member. CONSTITUTION:Irradiating light from a light source 2 is individually converged by each first lens element 3a formed on the surface, which faces the light source 2, of the translucent plate member 3 provided on the side of the surface, which faces the light source 2, of the display panel 4. Then, the light converged by the first lens elements 3a is converted into a parallel luminous flux by each second lens element 3b formed on the surface, which faces the display panel 4, of the translucent plate member 3, and for which the parallel luminous flux passes through a corresponding picture element 9a and directs the projecting lens 5. Since the translucent plate member 3 on which the lens elements 3a and 3b are formed is one, its aligning is easy and the number of boundaries on an optical path is accordingly decreased. Thus, without the need of enlarging the aperture of the projecting lens 5, assembly work is facilitated and a bright projecting picture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention projects light emitted from a light source and transmitted through a transmissive display panel having a plurality of picture elements arranged in a matrix onto a screen using a projection lens. The present invention relates to a projection type display device that performs enlarged projection.

Conventional technology A transmissive display panel does not itself emit light, but modulates the intensity of light from a separately provided light source by changing its light transmittance in response to a drive signal, allowing it to display images and characters. Examples include liquid crystal display panels, electrochromic displays, and PLZT.
Displays using translucent ceramics such as ((Pb, La) (Zr, Ti) O, porcelain) are well known.

In such a display panel, picture elements, which are the smallest display units, are arranged in a matrix, and images and characters are displayed by applying a driving voltage to each picture element individually.

There are simple matrix driving methods and tida matrix driving methods that apply driving voltages to each picture element of the display panel individually, but especially in the case of the active matrix driving method, each picture element A drive signal line for supplying drive voltage to the elements, a thin film transistor that controls the supply of drive voltage, and MIM (Metal-Insulat)
or-Metal) must be formed between the picture elements, which reduces the proportion of the picture element area in the screen (aperture ratio).

In this case, the light incident on the area of the display panel other than the pixel area, that is, the area to which no driving voltage is applied, is not modulated by the signal (driving voltage), so the light is transmitted in the area with no electric field. In a display panel in such an operation mode, light incident on areas other than picture element areas is transmitted through the display panel. Therefore, the black level displayed on the display screen is raised due to the pixel area controlled to be in a non-light-transmitting state, resulting in a problem that the contrast is reduced. Therefore, in order to prevent this contrast reduction, a light shielding mask is provided in areas other than the pixel area of the display panel.
A configuration is adopted in which light that does not contribute to display is absorbed or reflected by the light shielding mask.

However, as described above, when a light-shielding mask is provided in an area other than the pixel area of the display panel, a new problem arises in that the lower the aperture ratio of the display panel is, the darker the screen becomes even with the same light source.

In order to solve these problems, among the two transparent substrates that make up the display panel, the transparent substrate located on the light source side has a plurality of microlenses that correspond to each pixel individually on the surface facing the light source. arranged in a matrix,
A separate transparent plate is provided on the light source side of the display panel, and a plurality of microlenses corresponding to each pixel are arranged in a matrix on one side of the transparent plate to control the light emitted from the light source. A method has been developed in which each microlens focuses the light onto the corresponding pixel area of the display panel, thereby brightening the display screen (Japanese Patent Application Laid-Open No. 1986-1).
65621-165624).

Problems to be Solved by the Invention However, when the light condensing means using the microlens is applied to a projection type display device in which light transmitted through a display panel is enlarged and projected onto a screen using a projection lens,
As described below, the problem arises that the light transmitted through the display panel diverges, and the aperture of the projection lens must be increased accordingly.

In other words, after the light collected by the microlens passes through the pixel area of the display panel, it diverges at an angle determined by the ratio of the aperture of the microlens to the focal length.
The aperture of the projection lens must be increased depending on the angle. In particular, a color display projection in which display panels corresponding to each of the three primary colors are provided, images modulated for each color by the display panels are combined by a dichroic mirror, and enlarged and projected onto a screen by a common projection lens. In the case of a type display device, since the distance between the display panel and the projection lens becomes long, a projection lens with a larger diameter is required.

Therefore, in order to solve this problem, among the two transparent substrates that make up the display panel, one side of the transparent plate located on the projection lens side and another transparent plate placed on the projection lens side. Second microlenses that individually correspond to the picture elements are arranged in a matrix, and the light that is about to diverge after passing through the picture element area is converted back into a substantially parallel beam of light by the second microlenses. A method for preventing the aperture of the projection lens from increasing has also been developed (Japanese Patent Laid-Open No. 60-262131).

However, in this case, it is possible to form microlenses on each of the two transparent substrates of the display panel, or to form microlenses on one side of each transparent plate that is placed separately at the front and rear of the display panel. However, a new problem arises in that precise alignment between two transparent substrates or two transparent plates is required, which complicates the assembly work.

In addition, when transparent plates with microlenses formed on them are placed at the front and rear of the display panel, the number of interfaces along the optical path increases accordingly, resulting in an increase in reflection loss and stray light, which reduces display quality. .

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a projection display device that does not require a large aperture of a projection lens, is easy to assemble, and can provide a bright projected image.

Means for Solving the Problems The present invention uses a projection lens to enlarge and project light emitted from a light source and transmitted through a transmissive display panel having a plurality of picture elements arranged in a matrix onto a screen. In a projection type display device, a plurality of first lens elements, which are located on the surface side of the display panel facing the light source, are associated with individual picture elements of the display panel, and individually focus the irradiated light from the light source. are arranged in a matrix on the surface facing the display panel, and are respectively associated with these first lens elements and direct the light focused by the first lens elements to the projection lens through the picture elements corresponding to the display panel. This is a projection type display device characterized in that a light-transmitting plate member is provided in which a plurality of second lens elements that convert into parallel light beams are arranged in a matrix on a surface facing a display panel.

According to the present invention, the light irradiated from the light source by each first lens element formed on the surface facing the light source of the translucent plate member provided on the surface side facing the light source of the display panel. are individually focused, and each second lens element formed on the surface of the translucent plate member facing the display panel directs the focused light from the first lens element to the projection lens through the corresponding picture element. converted into luminous flux. Since there is only one transparent plate member on which the lens element is formed,
The alignment is easy, and the number of interfaces along the optical path is correspondingly reduced.

Embodiment FIG. 1 is a configuration diagram showing an optical system of a projection type display device which is an embodiment of the present invention.

In FIG. 1, a condenser lens 1 is a lens for condensing light emitted from a light source 2 into a light beam, and the light beam is transmitted to a transmissive liquid crystal display panel 4 via a light-transmitting plate member 3. It is incident. A projection lens 5 for enlarging and projecting the light transmitted through the liquid crystal display panel 4 onto a screen 6 is provided on the side facing the translucent plate member 3 across the liquid crystal display panel 4 . In addition, a condenser lens 1 is placed across the light source 2.
A reflecting mirror 7 is provided on the side facing the condenser lens 1 to reflect the light from the light source 2 that is irradiated onto the side opposite to the condenser lens 1 toward the condenser lens 1 side.

FIG. 2 is a partially enlarged sectional view showing a portion of FIG. 1 where the translucent plate member 3 and the liquid crystal display panel 4 are arranged.

In FIG. 2, the schematic configuration of the liquid crystal display panel 4 is 2.
A liquid crystal layer 9 is sandwiched between two transparent substrates 8a and 8b, and the liquid crystal layer 9 is divided into a plurality of picture element areas 9a arranged in a matrix and other non-picture element areas 9b. ing. Of these, the picture element region 9a can be switched between a state in which light can pass and a state in which it does not pass depending on whether or not a driving voltage is applied, while a light-shielding mask (not shown) is provided in the non-picture element region 9b. The incident light is not transmitted.

On the other hand, on the surface of the translucent plate member 3 facing the condenser lens 1, a plurality of first microlenses 3a having a convex lens effect are arranged in a matrix, corresponding to each pixel area 9a of the liquid crystal display panel 4. It is formed by Also,
On the surface of the translucent plate member 3 facing the liquid crystal display panel 4, a plurality of second microlenses 3b, which are individually associated with the first microlenses 3a and also have a convex lens effect, are arranged in a matrix. It is formed.

In this case, the focal length of the first microlens 3a is f
l, the focal length of the second microlens 3b is f2, and the thickness of the transparent plate member 3 is t, then these values are f1+f2! =:t...(1) fl
>f2...It is set so that the relationship (2) holds true. However, each focal length is 11
．． ! 2 is the value in the medium between the two microlenses 3a and 3b.

Next, the operation of the projection type display device will be explained.

The light emitted from the light source 2 is converted by the condenser lens 1 into a light beam parallel to the optical axis connecting the light source 2 and the center of the screen 6. The light beams are individually focused in the vicinity of their respective focal points (located within the transparent plate member 4) by the respective first microlenses 3a of the transparent plate member 3, as shown in FIG. . These focusing points correspond to the focal points of the second microlenses 3b of the transparent plate member 3, so the focused light is converted into approximately parallel light rays by the corresponding second microlenses 3b. , enters the corresponding picture element region 9a of the liquid crystal display panel 4.

At this time, since the diameter of the light flux that enters the liquid crystal display panel 4 is smaller than the diameter of the first microlens 3a, some light that would normally enter the non-pixel area 9b of the liquid crystal display panel 4 also enters the liquid crystal display panel 4. The light is focused on the pixel area 9a by the action of the microlenses 3a and 3b of the light-transmitting plate member 3.

When the picture element region 9a is controlled to be in a light transmitting state, the light incident on the picture element region 9a is transmitted through the liquid crystal display panel 4.

Since this light is converted into a substantially parallel light beam by the second microlens 3b, it can be sufficiently captured by the projection lens 5 even if the aperture of the projection lens 5 is not very large. The light incident on the projection lens 5 is enlarged and projected onto the screen 6, whereby an image is projected on the screen 6.

FIG. 3 shows the second microlens 3 of the translucent plate member 3.
FIG. 7 is a partially enlarged sectional view showing an example in which a lens having a concave lens effect is formed as b. The first microlens 3a is a lens having the same convex lens effect as in the previous embodiment, and the other configurations are also the same as in the previous embodiment.

In this case, the focal length of the first microlens 3a is fl, the focal length of the second microlens 3b is I2,
When the thickness of the transparent plate member 3 is t, these values are: 41-12 ζt (3) f
l>, f2+...The relationship of (4) is set so as to hold. However, each focal length f1. I2 is a value in the medium between the two microlenses 3a and 3b, and since the focal length I2 is the value of the microlens 3b having a concave lens effect, it is a negative value.

In the case of this embodiment, the substantially parallel light rays irradiated from the condenser lens 1 to the transparent plate member 3 are individually controlled by the respective first microlenses 3a at their respective focal points (outside of the transparent plate member 3). (located close to the liquid crystal display panel 4). These convergence points correspond to the focal points of the second microlenses 3b (concave lens effect) of the translucent plate member 3, so the light heading for convergence is almost parallelized by the corresponding second microlenses 3b. It is converted into a light beam and the corresponding pixel area 9a of the liquid crystal display panel 4
incident on .

At this time as well, the diameter of the luminous flux incident on the liquid crystal display panel 4 is
Since the diameter is smaller than the diameter of the first microlens 3a, light that would normally be incident on the non-picture element area 9b of the liquid crystal display panel 4 is also focused on the picture element area 9a. As in the previous embodiment, the substantially parallel light beams that have passed through the picture element area 9a are directed toward the projection lens 5.

In addition, the formation of the microlenses 3a and 3b on both surfaces of the light-transmitting plate member 3 in each of the above embodiments can be performed by the method listed below.

(1) A method in which plastic or glass is used as the material for the translucent plate member 3, and the material is molded by machining or molding. In addition to being directly machined, the mold may be formed by using methods (2) to (5) described below as a master mold and transferring it by a method such as electroforming.

(2) When a certain type of photosensitive resin is used as the material for the transparent plate member 3 and the surface of the photosensitive resin is partially exposed, unreacted monomers move from the non-exposed area to the exposed area. , A method of forming a convex lens by utilizing the phenomenon of the exposed area rising (Society of Applied Physics Optics Conference Micro-Optics Research Group Bulletin Vol. 15 No. 2 P. 118 (1987),
Vol. 1.6 No. 2 P87 (1988)).

(3) A thermoplastic resin is used as the material for the translucent plate member 3, and its surface is patterned into the planar shape of a lens using well-known photography technology, and then heated to a temperature above its softening point to give it fluidity. , a method of obtaining a convex lens by causing edge blur (JP-A-60-38989, JP-A-60-165623, JP-A-6L-67003). In this case, if the thermoplastic resin is photosensitive, it can be patterned by exposing itself to light.

(4) Using photosensitive resin as the material of the transparent plate member 3,
Proximity exposure (exposure without a photomask in close contact with the surface) is performed on the surface, and the amount of photoreaction products is distributed according to the blurring of the edges of the pattern, thereby obtaining a convex lens shape. Showa 6l-153602)
.

(5) Using photosensitive resin as the material of the transparent plate member 3,
A method of irradiating the surface with light having an intensity distribution to form a pattern of refractive index distribution according to the intensity of the light, thereby imparting a lens effect (Japanese Patent Laid-Open No. 6O-72927).

(6) A glass plate is used as the material of the translucent plate member 3, this glass plate is immersed in molten salt, and different types of alkali ions are passed between the glass plate and the molten salt through a mask provided on the glass plate. A method to obtain a glass plate with a refractive index distribution corresponding to a mask pattern by exchanging ions such as
tronics Letters Vol. 17 No.
, 13 P2S5 (1981)).

In addition, when forming microlenses 3a and 3b with different focal lengths on both sides of the translucent plate member 3 as shown in each example using the method (6) described above, the following procedure is used. That's fine.

First, metal thin films are formed on both sides of the transparent plate member 3 that forms the microlenses 3a and 3b. Next, one metal thin film is patterned to form a metal mask for forming microlenses 3a and 3b with long focal lengths, and ion exchange is further performed to start lens formation. The ion exchange is not continued until the desired microlens 3a is completed, but is interrupted midway.

Next, the other metal thin film is patterned to form a metal mask for forming the microlens 3b with a short focal length, and then ion exchange is restarted. In this way, the first microlenses 3a and the second microlenses 3b are simultaneously formed on both sides of the transparent plate member 3. In other words,
The ion exchange for forming the microlens 3a with a long focal length is started first, and the ion exchange and the ion exchange for forming the microlens 3b with a short focal length are completed at the same time.

When the microlenses 3a and 3b are formed by this method, the obtained microlens 3a.

Since there are no irregularities in the external shape of the panel 3b, the translucent plate member 3 can be attached to the liquid crystal display panel 4 without an air layer using an adhesive such as Canadian balsam or photo-softening resin, and the translucent plate member 3 can be attached to the liquid crystal display panel 4 without an air gap. The reflection loss of light on the surface of the sexual plate member 3 can be reduced to an almost negligible level.

Effects of the Invention As described above, according to the projection display device of the present invention, the light emitted from the light source onto the light source side surface of the translucent plate member is focused individually in association with each picture element of the display panel. While forming the first lens element, a second lens element converts the light focused by the first lens element on the display panel side surface of the translucent plate member into a parallel light flux and makes it incident on the corresponding picture element. As a result, light is concentrated on each pixel of the display panel to obtain a bright projected image, and the aperture of the projection lens can be kept small because the light transmitted through the display panel does not diverge. In addition, since light can be focused onto the picture elements of the display panel using only one translucent plate member, alignment with the display panel is easier, and the number of interfaces in the optical path is also reduced. Effects such as improved display quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an optical system of a projection type display device which is an embodiment of the present invention, FIG. 2 is a sectional view showing a part of the optical system in an enlarged manner, and FIG. FIG. 2 is an enlarged cross-sectional view of a part of the optical system of the projection display device according to the embodiment. 2... Light source, 3... Translucent plate member, 3a... First
microlens, 3b... second microlens,
4...Liquid crystal display panel, 5...Projection lens, 6...
・Screen, 9a...Picture element area

Claims (1)

[Claims] A projection type display device in which light emitted from a light source and transmitted through a transmission type display panel having a plurality of picture elements arranged in a matrix is enlarged and projected onto a screen using a projection lens. In the display panel, a plurality of first lens elements are located on the surface side of the display panel facing the light source, and are associated with individual picture elements of the display panel and individually focus the irradiated light from the light source. They are arranged in a matrix, and the light that is associated with each of these first lens elements and is focused by the first lens elements is converted into a parallel beam of light that goes to the projection lens through the picture elements corresponding to the display panel. 1. A projection type display device comprising a translucent plate member having a plurality of second lens elements for conversion arranged in a matrix on a surface facing a display panel.