Display apparatus

Abstract: A display apparatus displaying color image on a large screen. The display apparatus incorporating a large number of luminous picture elements (2) disposed in matrix formation. Four of those luminous picture elements (2) adjoining each other in the line and row directions are constructed into a group. Based on this formation, the display apparatus comprises the following; a display unit which provides the distance between those adjoining luminous picture elements (2) in each group to be shorter than the distance between those adjoining luminous picture elements (2) belonging to adjoining groups; and a magnifying unit (5) which further magnifies light beam emitted from each of those luminous picture elements (2) in the direction of adjoining luminous picture elements belonging to adjoining groups than in the direction of those luminous picture elements (2) in the group to which it belongs.

Description: The present invention relates to a display apparatus which displays a color image on a large screen by using a large number of luminous picture elements disposed in correspondence with a plurality of luminous colors. Description of Related Art Fig. 1 designates a perspective view of a conventional display apparatus disclosed in the Japanese Patent Application Laid-Open No. 64-2086 of 1989 for example. The reference numeral 11 shown in Fig. 1 designates a display unit, in which a plurality of luminous picture elements 21 including a red picture element 2R, a green picture element 2G, and a blue picture element 2B, are respectively disposed in parallel with each other in matrix formation. A number of spacers 31 are provided between the adjoining luminous picture elements 21. In addition, a magnifying unit 41 is disposed in front of the display unit 11. The magnifying unit 41 includes a plurality of convex lenses 51 in matrix formation, each of which corresponds to each of luminous picture elements 21. Next, the functional operation of this conventional display apparatus is described below. Each of these luminous picture elements 21 is driven by a driving system (not shown) to emit its own color beam. As a whole, these luminous picture elements 21 are disposed at equal intervals. Assume that the interval (in other words, width of the spacer 31) is expressed in terms of P22. Speaking of a large-screen display apparatus, this display apparatus may be composed of a plurality of display units 11 shown in Fig. 1 in alignment with each other. In order to precisely dispose these luminous picture elements 21 at equal intervals, it is essential for this display apparatus to provide the spacer width P22 which is more than double the edge-directional distance P23 between the most peripheral luminous the blue picture element 21 and the wall edge of the display unit 11. While operating a large-screen display apparatus, luminosity of each luminous picture element 21 is controlled in order that the luminosity can always remain proportional to the amplitude of television signals. Although these luminous picture elements 21 are discretely aligned at the predetermined intervals, viewers can properly recognize the continuously running television image when they watch the display unit 11 across an adequate distance. Now, in order to secure high resolution of the image on a large-screen display, it is essential for the display apparatus to increase the number of the luminous picture elements 21 per unit area. In other words, it is essential for the system to contract the distance P21 between the center positions of the adjoining luminous picture elements 21. Nevertheless, as mentioned earlier, the display unit 11 must provide the spacer width P22 which is more than double the edge-directional distance P23, and yet, since the edge-directional distance P23 is substantially the wall thickness of the display unit 11, there is a definite limit to thin the edge-directional distance P23 furthermore. As a result, in order to increase the number of the luminous picture elements 21 per unit area, the dimension of these luminous picture elements 21 must be contracted. In other words, the finer the resolution of the image on display, the lesser the area ratio available for illumination. When this condition is present, it merely results in the emphasized discontinuity of the discretely aligned luminous picture elements 21. In consequence, image quality degrades itself to cause viewers to feel rough quality of the image on the TV screen. To prevent this adverse effect, there is an idea of providing the magnifying unit 41 in front of the display unit 11 like the one shown in Figs. 1 and 2. For example, a plurality of convex lenses 51 are provided in front of the corresponding luminous picture elements 21 by way of setting the center positions of those luminous picture elements 21 in perfect accord with the center positions of these convex lenses 51 in order to apparently expand the luminous area ratio so that image quality can eventually be improved. When implementing this method, as shown in Fig. 3, when looking at those luminous picture elements 21 through the magnifying unit 41, the distance P21 between the centers of the adjoining luminous picture elements 21 is equal to the distance P41 between the centers of the adjoining convex lenses 51. Nevertheless, the apparent interval P42 between the luminous picture elements 21 is shorter than the original interval P22 between the luminous picture elements 21. Fig. 4 designates another structure of the conventional display unit 11 in which the luminous picture elements 2 substantially composed of an independent red picture element R, or an independent green picture element G, or an independent blue picture element B, are aligned with each other. Even when using this structure, based on the reason cited above, it is also essential for the display unit 11 to provide the spacer width P22 which is more than double the edge-directional distance P23. In consequence, the finer the resolution of image on display, the narrower the area of each luminous picture element 2 as shown in Fig. 5, thus resulting in the lowered luminosity. There is the structure of a display unit 1 designed for preventing luminosity from lowering itself as shown in Fig. 6, which contracts the distance P1 between two adjoining luminous picture elements in a group including four luminous picture elements to be shorter than the distance P2 between adjoining groups. This system is disclosed in the Japanese Utility Model Application Laid-Open No. 63-174377 of 1988. This system provides a spacer width P22 which is more than double the edge-directional distance P23, and yet, contracts the distance between adjoining luminous picture elements 2 of each group nit to be shorter than the distance between a luminous picture element 2 belonging to a group and a luminous picture element 2 belonging to another adjoining group in order that the area of these luminous picture elements 2 can be expanded from the area of the luminous picture elements 2 shown in Fig. 5. In this way, when constructing one group of four luminous picture elements 2 and expanding the area of luminous picture elements 2, the luminous picture elements 2 are necessarily disposed by applying uneven pitch containing deviation in the column and row directions every two luminous picture elements. As a result, this structure usefully promotes luminosity, but instead, it lowers image quality, and thus, there is a definite limit in the possibility of expanding the area of each luminous picture element 2 even when composing a display apparatus based on this art. Concretely, when the distance P1 between the luminous picture elements 2 and the distance P2 between those groups mentioned above are expressed by a relationship P1/P2 = 1, all the luminous picture elements 2 are properly disposed with an equal pitch as shown in Figs. 4 and 5. The relationship between P1 and P2 shown in Fig. 6 approximately corresponds to P1/P2 = 0.7. On the other hand, the relationship between P1 and P2 shown in Fig. 7 approximately corresponds to P1/P2 < 0.6. The test result proves that there is a definite limit in the image quality when there is a relationship P1/P2 = 0.65. Taking these factors into account, the system of aligning the luminous picture elements 2 shown in Fig. 6 is dominantly useful in the promotion of luminosity rather than such an adverse effect in the degradation of image quality. Nevertheless, although the system shown in Fig. 7 for the alignment of luminous picture elements 2 more effectively promotes luminosity, it is by no means suited for practical application. Any of the conventional display apparatuses incorporates any of those structures cited above. Nevertheless, since the conventional display apparatus respectively expands apparent luminous areas by applying the magnifying unit 41 by way of disposing all the luminous picture elements 21 based on the equal pitch, the actual luminous areas are not substantially expanded at all. As a result, luminosity cannot fully be promoted. In consequence, the conventional display apparatus cannot be effectively made available in bright environments like a rail-road station or an airport where a large number of passengers assemble. On the other hand, if the conventional display apparatus is compulsorily provided with intensified luminosity, excessive power like extremely high energy will be given to those luminous picture elements 21, thus quickly dissipating the service life of the display unit 11. On the other hand, the conventional display apparatus disposing the luminous picture elements 2 based on uneven pitch is obliged to expand the areas of those luminous picture elements 2 for the sake of enhancing luminosity. This in turn means that the wider the areas of those luminous picture elements 2, the poorer the image quality in consequence. Because of this reason, the conventional display apparatus cannot practically expand the area ratio beyond a certain limit. This in turn involves critical problem. An object of the invention is to provide a novel display apparatus that can securely provide highly intensified luminosity by substantially expanding areas of the luminous picture elements. Another object of the invention is to provide a novel display apparatus that can securely provide extremely smooth color image by effectively preventing a degradation of the image quality. A still further object of the invention is to provide a novel display apparatus that can securely protect durable service life of the display unit. The invention provides a novel display apparatus available for displaying a stable color image on a large screen. The display apparatus embodied by the invention incorporates a large number of luminous picture elements which are disposed in matrix formation. Of those many luminous picture elements, each four elements adjoining each other in the column and row directions are constructed into a group. The display apparatus embodied by the invention characteristically comprises the following: a display unit in which the distance between the adjoining luminous picture elements in each group is substantially shorter than the distance between the adjoining luminous picture elements belonging to adjoining groups; and a magnifying unit which is disposed in front of the display unit, wherein the magnifying unit magnifies light beam emitted from each luminous picture element farther in the direction of the adjoining luminous picture elements belonging to adjoining groups than in the direction of the luminous picture elements adjoining each other in a group to which it belongs. The magnifying unit provided for the display apparatus embodied by the invention apparently approximates the ratio (P1/P2) between the distance P1 between each luminous picture element and the distance P2 between each group to the value 1. In consequence, even though the display apparatus actually has an insignificant value of the ratio P1/P2, image quality can remain stable without incurring degradation at all. The above and further objects and features of the invention will more fully be apparent from the following detailed description and the accompanying drawings. Fig. 1 is a perspective view of a conventional display apparatus; Fig. 2 is a sectional view of the conventional display apparatus shown in Fig. 1; Fig. 3 is explanatory of the magnifying effect of the magnifying unit shown in Fig. 1; Figs. 4 and 5 respectively designate the arrangement of independent luminous picture elements; Figs. 6 and 7 respectively designate the arrangement of luminous picture elements when constructing four luminous picture elements into a group; Fig. 8(a) is a sectional view of the display apparatus according to an embodiment of the invention; Fig. 8(b) is the magnified condition of the luminous picture elements when using the magnifying unit shown in Fig. 8(a); and Fig. 9 is a sectional view of the display apparatus according to another embodiment of the invention. Referring now more particularly to the accompanying drawings, the display apparatus according to an embodiment of the invention is described below. First, refer to Fig. 8(a) which designates the sectional view of the display apparatus embodied by the invention. The reference numeral 1 designates a display unit, 2 designates a large number of luminous picture elements consisting of red, green or blue independent picture elements, and 4 designates a magnifying unit in which a large number of convex lenses 5 are aligned in correspondence with respective luminous picture elements 2. Fig. 8(b) designates the magnified condition of light beams emitted from the luminous picture elements 2 when viewers look at the front of the magnifying unit 4. Next, functional operation of the display apparatus embodied by the invention is described below. A number of luminous picture elements 2 are disposed in the display unit 1 according to the arrangement shown in Fig. 1 for example. Fig. 7 shows the arrangement in which each four luminous picture elements 2 conjunctionally make up a group, and, the red picture element R, the green picture elements G, and the blue picture element B, are disposed according to the predetermined composition ratio 1:2:1. Furthermore, less than 0.6 is provided for the ratio P1/P2 between the inter-element distance P1 between the luminous picture elements adjoining each other in each group and the inter-group distance P2 between the adjoining luminous picture elements belonging to adjoining groups. As mentioned earlier, when introducing the above arrangement based on less than 0.6 of the ratio P1/P2, image quality significantly lowers. To prevent this, the display apparatus embodied by the invention is provided with a number of convex lenses 5 in front of corresponding luminous picture elements 2, and, as shown in Fig. 8(a), the center "r" of each convex lens 5 deviates from the center "p" of each corresponding luminous picture element 2 by an amount ΔP in the direction of the center of each group. Because of this arrangement, light beams emitted from each luminous picture element 2 are magnified farther in the direction of the adjoining groups. By properly establishing the value ΔP or the magnification of each convex lens 5, it is possible for the display apparatus of the invention to apparently materialize the ratio P1/P2 = 1. Since the display apparatus of the invention achieves the above arrangement, as shown in Fig. 8(b), when looking at the magnifying unit 4 from the front, viewers can witness a number of magnified luminous picture elements 2a containing a ratio P1/P2 which is closer to the value 1 than the actual ratio value present in the display unit 1. In consequence, the display apparatus embodied by the invention can securely prevent the image quality from adversely being affected by uneven pitch, and yet, effectively promotes image resolution availing of properly magnified areas of the aligned luminous picture elements. Furthermore, the display apparatus embodied by the invention apparently materializes substantial magnification of luminous area more than that is normally generated by any conventional display apparatus. The above description has solely referred to an embodiment in which the display unit 1 contains 1:2:1 of the composition ratio of the R.G.B. components in a group of four luminous picture elements 2. Nevertheless, the embodiment of the invention may also use a composition ratio based on any value other than the one specified above. Furthermore, the display unit 1 embodied by the invention may not only use the three primary colors, but may also use monochromatic composition as well. The above description has also solely referred to the use of convex lenses 5. Nevertheless, as shown in Fig. 9, another embodiment of the invention allows light beams emitted from those luminous picture elements 2 to be magnified furthermore in the direction of the adjoining groups by introducing a number of photoconductors 5a like optical fibers in place of the convex lenses 5. This system securely provides quite satisfactory magnifying effect exactly identical to that which is achieved by the preceding embodiment. As is clear from the above description, the display apparatus embodied by the invention disposes a large number of luminous picture elements in the display unit by way of contracting the distance between the luminous picture elements to be shorter than the distance between groups, and yet, provides the magnifying unit such like convex lenses in order that the distance between adjoining luminous picture elements can apparently approximate the distance between adjoining groups. By virtue of these unique arrangements, the display apparatus embodied by the invention can securely promote luminosity by effectively applying magnified luminous areas, and yet, the display apparatus stably provides fine and smooth images without causing image quality to degrade, while effectively promoting the service life to a great extent.

Claims: A display apparatus comprising: a display unit incorporating a plurality of luminous picture elements (2) disposed in groups in matrix formation, wherein the distance (P₁) between adjacent picture elements in each group is shorter than the distance (P₂) between adjacent picture elements belonging to adjoining groups, said groups being composed of a number of picture elements; and a magnifying unit (4) which magnifies light beam emitted from each of said luminous picture elements (2) farther in the direction of those adjoining luminous picture elements belonging to adjoining groups than in the direction of those adjoining luminous picture elements in the group to which said luminous picture element belongs, characterised in that said picture elements (2) of a respective group are arranged in row and column directions, and said magnifying unit (4) comprises a plurality of magnifying elements (5) which are respectively disposed in confrontation with said picture elements, wherein each of said plurality of magnifying elements (5) magnifies a light beam emitted from each of said plurality of picture elements (2) farther in the direction of those adjoining picture elements belonging to adjoining groups than in the direction of those adjoining picture elements (2) in the group to which said picture element (2) belongs. A display apparatus according to claim 1, wherein said picture elements (2), when seen from the front, are aligned at apparently equal intervals. A display apparatus according to claim 1 or 2, wherein said plurality of magnifying elements are a plurality of convex lenses (5). A display apparatus according to claim 3, wherein the center of each convex lens (5) deviates in the direction of the center of the group to which the corresponding picture element belongs, from the center of the corresponding picture element. A display apparatus according to claim 1 or 2, wherein said plurality of magnifying elements are a plurality of optical fibers (5a). A display apparatus according to anyone of the preceding claims, wherein four picture elements (2) adjoining each other in the row and column directions conjunctionally make up a group. A display apparatus according to claim 6, wherein said group is composed of a red picture element, two green picture elements, and a blue picture element.

Inventors: FUTATSUISHI SHUNICHI C O MITSU, HARA ZENICHIRO C O MITSUBISHI, TERAZAKI NOBUO C O MITSUBISHI, FUTATSUISHI, SHUNICHI, C/O MITSUBISHI DENKI K. K., HARA ZENICHIRO, C/O MITSUBISHI DENKI K. K., TERAZAKI, NOBUO, C/O MITSUBISHI DENKI K. K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1991
Main classification: G09F9
IPC codes: G02F1, H04N9, H01J29, G09F9