JP2001013878A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a display device in which a large screen having no irregular brightness can be obtained by converting rays again into almost parallel beams near the screen to illuminate the screen almost perpendicular to the screen. SOLUTION: The display device consists of back light units 11a to 11d which emit almost parallel beams, transmission type liquid crystal panels 12a to 12d which can display specified images, microlens arrays 13a to 13d, 14a to 14d to produce erect images, Fresnel concave lenses 15a to 15d to enlarge and project the images, Fresnel convex lenses 16a to 16d to convert the rays into almost parallel light again, and a lenticular sheet 17 as a screen. In this device, the images in the display part of the transmission liquid crystal panels 12a to 12d arranged on a panel are enlarged while the space between images are reduced, and then projected on the lenticular sheet 17 while converting again the light beams into almost parallel beams.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology of a display device using a liquid crystal panel, and more particularly to a projection type display device using a plurality of liquid crystal panels for displaying a display image on a large screen, such as an OA device or a television. And effective technology.

[0002]

2. Description of the Related Art For example, as a technique studied by the present inventor, a liquid crystal panel used in a projection type display device is as follows.
A structure as shown in FIG. 8 is conceivable. The transmission type liquid crystal panel 61 shown in FIG. 8 has an image display unit 62,
One or two sides around it (the upper and
A driver IC 63 for driving is installed on the side (side), and that portion is a non-display portion of an image. Also, on the side where the driving driver IC 63 is not installed (the two sides on the lower side and the right side in FIG. 3), there is a liquid crystal sealing material.
The end of the transmissive liquid crystal panel 61 is not the end of the image display section 62, and there is a non-display section.

Further, when a display device is used for OA and CAD applications, it is required to increase the size of the display device so that more information can be displayed than the entire paper. However, when the size of the liquid crystal panel is increased, the probability that the liquid crystal panel becomes defective due to the attachment of dust to one panel increases, and the yield decreases, so that the price rapidly increases.
Therefore, for example, as shown in FIG. 9, a plurality of transmissive liquid crystal panels 61 shown in FIG. 8 may be arranged (four transmissive liquid crystal panels 61a to 61d in FIG. 9) to enlarge the screen. As described above, since there is a non-display portion, a gap is formed between the display portions, which makes it difficult to see.

The most practical method for realizing a large screen is a method of enlarging and projecting a small liquid crystal display element with a projection lens, that is, a so-called general liquid crystal projector.
A long projection distance is required.

Further, as a method for enlarging the screen, there is, for example, a short-distance projection system as disclosed in Japanese Patent Application Laid-Open No. 5-188340. Hereinafter, this method will be described with reference to FIGS. FIG. 10 is a front view of a display device of the short-distance projection system, and FIG. 11 is a cross-sectional view of the display device taken along the line BB ′ (cross-sectional display is omitted).

As shown in FIG. 10, the display device has display portions 71a to 71d arranged without a gap when viewed from the front, and a housing 72 is provided around the display portions. As shown in FIG.
In the depth direction of the display device, the backlights 73 a to 73 a
d, transmissive liquid crystal panels 74a to 74d, imaging lens 75
a to 75d, magnifying lenses 76a to 76d, screen 7
7 are arranged.

In this configuration, the backlights 73a to 73a
The light beam from 73d is applied to the transmission liquid crystal panels 74a to 74d, and the images displayed on the transmission liquid crystal panels 74a to 74d are formed on the screen 77 by the imaging lenses 75a to 75d. At this time, the magnifying lens 76a
By enlarging the image with the screen 76d and projecting it on the screen 77, the gap between the transmissive liquid crystal panels 74a to 74d can be eliminated on the screen 77, and a continuous large screen can be obtained.

[0008]

The inventors of the present invention have studied the technique of the short-range projection system as described above, and as a result, the following has become clear. That is,
In the short-distance projection method, light rays are bent to enlarge an image. Therefore, the angle of light rays emitted from the screen varies depending on the position in the transmissive liquid crystal panel. It is possible that

That is, in the central part of the transmissive liquid crystal panel, the light beam goes almost straight, but in the peripheral part, it is bent outward and forms an angle, and then strikes the screen. Will have different angular distributions. Therefore, a bright portion differs depending on the position of the viewing position with respect to the screen, and is visually recognized as uneven brightness.

Therefore, an object of the present invention is to pay attention to an angle of a light beam with respect to a screen which causes uneven brightness,
The present invention provides a display device capable of obtaining a large screen without luminance unevenness by returning this light beam to substantially parallel light near the screen and applying the light beam substantially vertically to the screen.

[0011]

A display device according to the present invention comprises a transmissive liquid crystal panel and a backlight unit for irradiating the liquid crystal panel with substantially parallel light in which light rays within a predetermined angle form the majority of the angular distribution. A screen for projecting an image displayed on the liquid crystal panel by irradiation of the backlight unit, a first lens for erectly forming an image displayed on the liquid crystal panel on the screen, and the first lens A second lens for enlarging and projecting an image erectly formed on the screen and projecting an angled light beam enlarged by the second lens into substantially parallel light near the screen. And a third lens. Thus, the display area on the screen can be made larger than the display area of the liquid crystal panel, and the display can be made substantially parallel so that there is no luminance unevenness.

Further, by arranging a plurality of liquid crystal panels in a plane and making the gap between the display areas on the screen on which the image of the liquid crystal panel is projected smaller than the gap between the display areas of the liquid crystal panel, visually, It can be seen as a continuous surface.

In addition, by using two microlens arrays in combination as the first lens,
The working distance is shortened due to the fine lens, and the device can be thinned.

In addition to this, an aspheric Fresnel concave lens for eliminating pincushion aberration is used as the second lens, and an aspheric Fresnel convex lens corresponding to the aspheric Fresnel concave lens is used as the third lens. Thus, the pincushion aberration can be corrected.

Here, in the aspherical formula of the aspherical Fresnel convex lens and the aspherical formula of the aspherical Fresnel concave lens, the conical constant is made equal in the vicinity of −1, and the other coefficients are set to the values of the aspherical Fresnel convex lens. The value of the aspherical Fresnel concave lens can be changed by the magnification. Assuming that the conic constant is -1, the lens curved surface becomes a parabolic curved surface, and pincushion aberration is corrected for substantially parallel incident light.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, an example of a configuration of a display device according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a front view of the display device, and FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.

The display device according to the present embodiment is, for example, shown in FIG.
As shown in the figure, display sections 1a to 1d of four images are arranged on the front surface, and the periphery thereof is surrounded by the housing 2. As shown in FIG. 2, from the rear side in the depth direction, four backlight units 11a to 11d and four transmissive liquid crystal panels 12a to 12d are provided.
2d, two microlens arrays 13a to 13
13d, 14a to 14d, four Fresnel concave lenses 15
a to 15d, four Fresnel convex lenses 16a to 16d,
One lenticular sheet 17 is commonly arranged in order, and these are held by the housing 2.

The backlight units 11a to 11d are
This is a back-illumination unit having a function of irradiating substantially parallel light in which light rays within a predetermined angle form the majority of the angular distribution. Irradiated to １２12d.

The transmissive liquid crystal panels 12a to 12d are liquid crystal panels having a function of displaying a predetermined image using a liquid crystal whose transmission of light can be controlled by a voltage.
The transmission of the light beams by the irradiation from the backlight units 11a to 11d is controlled to control the transmission type liquid crystal panels 12a to 12d.
A predetermined image is displayed on 2d.

The micro lens arrays 13a to 13d, 1
Reference numerals 4a to 14d denote first lenses having a function of erecting images displayed on the transmissive liquid crystal panels 12a to 12d on a screen. For example, as shown in FIGS. Double-sided convex micro lenses 21 and 22
Are arranged in an array. In the two microlens arrays 13a to 13d and 14a to 14d, the respective microlenses 21 and 22 correspond to each other and the optical axes are aligned. Thereby, the two micro lens arrays 13a to 13a
13d, 14a to 14d, the transmission type liquid crystal panel 12
The images displayed on a to 12d are projected on the lenticular sheet 17 at an erect equal magnification. Further, since the image is formed by the fine micro lenses 21 and 22, the working distance can be shortened, and the image can be formed with a short projection distance.

The Fresnel concave lenses 15a to 15d are second lenses having a function of enlarging and projecting an image erected by the micro lens arrays 13a to 13d and 14a to 14d onto a screen, and are of a transmission type. The optical axes are aligned with the centers of the image display sections of the liquid crystal panels 12a to 12d, and the light rays are gradually bent outward from the center toward the outer circumference.
The image displayed on the 12d is a lenticular sheet 17.
The image is enlarged when projected on The enlargement ratio is set so that when an image is projected on the lenticular sheet 17, the size of the image is such that there is no gap between adjacent images. In general, the non-display portions of the transmissive liquid crystal panels 12a to 12d have a smaller area than the image display portion.
The magnification is double to 1.3 times.

The Fresnel convex lenses 16a to 16d are third lenses having a function of returning the angled rays enlarged by the Fresnel concave lenses 15a to 15d to substantially parallel light near the screen.
The light beam bent by .about.15d is returned to the original substantially parallel light near the lenticular sheet 17.

The lenticular sheet 17 has a function of projecting an image displayed on the transmissive liquid crystal panels 12a to 12d into an erect image, enlarging the image, and returning the image to substantially parallel light, and projecting the image returned to the substantially parallel light. The image formed on the lenticular sheet 17 is diffused when emitted from the lenticular sheet 17, and the viewing angle is widened.

In the display device configured as described above, the transmissive liquid crystal panels 12a to 12d have visual characteristics, and there is a problem that the contrast is inverted with respect to a light beam that passes obliquely beyond a predetermined angle. Further, the microlens arrays 13a to 13d and 14a to 14d have a take-in angle, and light rays exceeding the take-up angle do not form an image at a desired position and cause a decrease in contrast. This will be described with reference to FIG. 4 showing the take-in angles of the microlens arrays 13a and 14a.

As shown in FIG. 4, two microlens arrays 13a and 14a are arranged with their optical axes aligned.
As for the microlenses 21a within a predetermined take-in angle at positions within a predetermined angle with respect to the image 31 on the transmissive liquid crystal panel 12a, the light beams pass through the paired microlenses 22a as predetermined, and And is projected as an image 33 on the lenticular sheet 17. However, the microlenses 21b outside the predetermined take-in angle at positions exceeding the predetermined angle do not pass through the microlenses 22b forming a predetermined pair, resulting in an undesired locus 34.

For these reasons, in order to increase the contrast, it is necessary to reduce the number of rays emitted from the transmissive liquid crystal panels 12a to 12d exceeding a predetermined angle. A light beam that emits substantially parallel light, which is the majority of the angular distribution, is used. The predetermined angle is the transmission type liquid crystal panels 12a to 12d.
Visual characteristics, microlens arrays 13a to 13d, 1
Considering the limitation of the take-in angle coming from the manufacturing technology of 4a to 14d, the feasibility of the backlight units 11a to 11d, etc., ± 10 ° to straight light (0 ° perpendicular)
± 20 ° is considered reasonable.

Here, the backlight units 11a to 11a
As 1d, for example, one that emits substantially parallel light using the technology of Japanese Patent No. 2706574 is commercially available. For example, FIG.
An example of the angle distribution characteristic of the 1d ray is shown. FIG.
5 (b) shows the relationship of the light intensity with respect to the angle from the vertical line in the Y direction.
Most of the rays fall in the range of ± 20 ° which supports the validity of °.

By using these and dividing and displaying one image for each of the transmissive liquid crystal panels 12a to 12d, a large screen image can be obtained on the lenticular sheet 17. In the present embodiment, in the example of FIG.
Four (2) × 2 (columns) four transmissive liquid crystal panels 12a to
12d are arranged in a plane, which is m (row) × n
An arbitrary number of (rows) transmissive liquid crystal panels can also be realized by arranging them in a plane.

In the above, the Fresnel concave lenses 15a to 15a
When a spherical lens is used for 15d, pincushion aberration occurs, for example, as shown in FIG. 6, since the lenticular sheet 17 serving as a screen is flat. 6A and 6B show an example for explaining pincushion aberration. FIG. 6A shows an image display section of the transmission type liquid crystal panels 12a to 12d, and FIG. 6B shows an image of the lenticular sheet 17.

As shown in FIG. 6A, the transmission type liquid crystal panel 12
a rectangular image 41 displayed on the image display units a to 12d
However, as shown in FIG. 6B, when projected on the lenticular sheet 17, the image 42 becomes distorted. In order to correct this, the problem can be solved by using an aspheric lens in which the curved surfaces of the Fresnel concave lenses 15a to 15d are designed to correct pincushion aberration.

At this time, the Fresnel concave lenses 15a to 15d
Is made aspherical, accordingly, the Fresnel convex lens 1
Unless 6a to 16d are also aspherical, they cannot be converted into substantially parallel light near the lenticular sheet 17. Here, the aspherical formulas of the aspherical Fresnel convex lenses 16a to 16d and the aspherical formulas of the aspherical Fresnel concave lenses 15a to 15d are as follows.
The conical constants are made equal in the vicinity of −1, and the other coefficients may be obtained by changing the values of the Fresnel convex lenses 16a to 16d by the magnification factor with respect to the values of the Fresnel concave lenses 15a to 15d.

Here, the aspherical expression will be described with reference to FIG. 7 and Expression (1). FIG. 7 shows a cross-sectional view of the aspherical lens (cross-section not shown). For example, FIG. 7A shows an example of a Fresnel convex lens 16a, and FIG. 7B shows an example of a Fresnel concave lens 15a. The aspherical expression of the curved surface 51 of the Fresnel convex lens 16a and the curved surface 52 of the Fresnel concave lens 15a can be expressed as follows.

[0034]

(Equation 1)

Where Z is the height of the aspherical surface, Y is the radius of the aspherical surface, k is the conic constant, and c, c ₄ , c ₆ , and c ₈ are the constants.

In this aspherical equation, the conic constant k is -1.
Then, the curved surface becomes a parabolic surface. Fresnel convex lens 1
6a to 16d, and the light rays incident on the Fresnel concave lenses 15a to 15d are substantially parallel light, and are projected onto the lenticular sheet 17 by the parabolic lens with the pincushion aberration corrected. At 1.03 times to 1.3 times the magnification in the present embodiment, the conical constant k is −1 to 1 in consideration of other corrections.
-0.9 is the optimal range. Regarding the other constants of the aspherical formula, in the present embodiment, fourth-order or higher-order ones are small values that can be omitted, and thus the constants c ₄ , c ₆ , and c ₈ may be zero. For the constant c, the Fresnel concave lenses 15a to 15
-0.001 to -0.1 for d, Fresnel convex lenses 16a to 1
The optimum range is -0.0007 to -0.07 for 6d.

Therefore, according to the display device of the present embodiment, the backlight unit 1 for irradiating substantially parallel light is provided.
1a to 11d, transmissive liquid crystal panels 12a to 12d capable of displaying a predetermined image, microlens arrays 13a to 13d, 14a to 14d for erect imaging, Fresnel concave lenses 15a to 15d for enlarged projection, substantially parallel light The following effects can be obtained by comprising the Fresnel convex lenses 16a to 16d for returning to the original state and the lenticular sheet 17 serving as a screen.

(1) The display portion on the lenticular sheet 17 can be made larger than the display portions of the transmissive liquid crystal panels 12a to 12d, and the light can be made substantially parallel in the vicinity of the lenticular sheet 17. This makes it possible to obtain an image without uneven brightness.

(2) By making the gap between the display units on the lenticular sheet 17 smaller than the gap between the display units of the transmissive liquid crystal panels 12a to 12d, it is possible to make them appear visually continuous. it can. This makes it possible to obtain a continuous large screen without luminance unevenness.

(3). Microlens arrays 13a to 13
The working distance is shortened due to the use of the fine microlenses 21 and 22 by using two of d, 14a to 14d in combination. This makes it possible to reduce the thickness of the device.

(4). Aspherical Fresnel concave lenses 15a-1
By using 5d and Fresnel convex lenses 16a to 16d, pincushion aberration can be corrected.

The present invention is not limited to the above embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention. For example, the number of transmissive liquid crystal panels is not limited to four (2 (row) × 2 (column)), but 2 × 3 = 6, 3 × 3 = 9, or an arbitrary number of m × n. Can also be applied to a case in which are realized in a plane.

[0043]

As described above, according to the display device of the present invention, the images of the display portions of a plurality of transmissive liquid crystal panels arranged in a plane are enlarged, the gap is reduced, and the display device is provided near the screen. By projecting the light on a screen after converting the light into a substantially parallel light, a large screen without continuous luminance unevenness can be obtained. In addition, by using a micro lens array having a short working distance as described above and a small magnification of the concave lens, the projection distance can be shortened, a device having a small depth is created, and the display device is made thin. Can be realized.

[Brief description of the drawings]

FIG. 1 is a front view showing a display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1 in the display device according to the embodiment of the present invention;

FIG. 3 is a front view showing a microlens array in the display device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a take-in angle of a microlens array in the display device according to the embodiment of the present invention.

FIGS. 5A and 5B are explanatory diagrams showing an angle distribution characteristic of a light beam of a backlight unit in the display device according to the embodiment of the present invention.

FIGS. 6A and 6B are explanatory diagrams showing pincushion aberration in the display device according to the embodiment of the present invention.

FIGS. 7A and 7B are cross-sectional views showing an aspheric lens in the display device according to the embodiment of the present invention.

FIG. 8 is a front view showing a transmission type liquid crystal panel of a display device which is a premise of the present invention.

FIG. 9 is a front view showing a transmission type liquid crystal panel of another display device which is a premise of the present invention.

FIG. 10 is a front view showing still another display device on which the present invention is based.

FIG. 11 is a cross-sectional view taken along line BB ′ of FIG. 10 in still another display device on which the present invention is based;

[Explanation of symbols]

1a to 1d display unit, 2 housing, 11a to 11d backlight unit, 12a to 12d transmission liquid crystal panel, 13a to 13d, 14a to 14d micro lens array, 15a to 15d Fresnel concave lens, 16a to
16d: Fresnel convex lens, 17: Lenticular sheet, 21, 22: Micro lens, 21a, 22a: Micro lens within a predetermined take-in angle, 21b, 22b: Micro lens outside a predetermined take-in angle, 31: Image on transmission type liquid crystal panel , 32: the trajectory of the light beam as specified, 33: the image on the lenticular sheet, 34: the trajectory of the light beam not specified, 41, 42: the image, 51, 52: the curved surface.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13357 G03B 21/00 D G03B 21/00 G09F 9/40 301 G09F 9/40 301 G02F 1/1335 530 (72) Inventor Naohisa Koizumi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Digital Media System Division of Hitachi, Ltd. (72) Inventor Hitoshi Suzuki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Inside the Digital Media System Division of the Works (72) Inventor Toshiaki Fujie 810 Shimoimaizumi, Ebina City, Kanagawa Prefecture Inside the PC Division of Hitachi, Ltd. (72) Inventor Hironori Oikawa 810 Shimoimaizumi Shimoimaizumi, Kanagawa Prefecture Hitachi, Ltd. (72) Inventor Naoshi Iwata Ebina-shi, Kanagawa 810 Shimoimaizumi F-term in the PC Division of Hitachi, Ltd. (Reference) 2H087 KA07 RA04 RA12 RA13 RA26 RA47 UA01 2H091 FA27X FA28X FA29X FA41Z LA11 LA18 MA07 5C094 AA03 BA16 BA43 DA01 ED01 HA08 5G435 AA01 BB12 GG06 DD05 LL12

Claims (5)

[Claims] 1. A transmissive liquid crystal panel, a backlight unit for irradiating the liquid crystal panel with substantially parallel light in which light rays within a predetermined angle form a majority of the angular distribution, and irradiating the backlight unit with the liquid crystal. A screen for projecting an image displayed on the panel, and a first screen for erectly forming an image displayed on the liquid crystal panel on the screen.
A second lens for enlarging and projecting an image erectly formed by the first lens on the screen, and a light beam enlarged and angled by the second lens. A third lens near the screen for returning the light to substantially parallel light, wherein a display area on the screen is larger than a display area of the liquid crystal panel. 2. The display device according to claim 1, wherein a plurality of the liquid crystal panels are arranged in a plane, and a gap between display areas on the screen on which an image of the liquid crystal panel is projected is defined by the liquid crystal panel. Wherein the gap between the display areas is smaller than the gap. 3. The display device according to claim 1, wherein two microlens arrays are used in combination as said first lens. 4. The display device according to claim 1, wherein an aspheric Fresnel concave lens for eliminating pincushion aberration is used as the second lens, and the aspheric Fresnel concave lens is used as the third lens. A display device using a corresponding aspherical Fresnel convex lens. 5. The display device according to claim 4, wherein in the aspherical formula of the aspherical Fresnel convex lens and the aspherical formula of the aspherical Fresnel concave lens, a conical constant is made equal in the vicinity of −1, and Wherein the value of the aspherical Fresnel convex lens is changed by the magnification factor with respect to the value of the aspherical Fresnel concave lens.