Flat type image display apparatus

• US 6,268,843 B1
• Filed: 08/06/1993
• Issued: 07/31/2001
• Est. Priority Date: 08/10/1989
• Status: Expired due to Fees

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Arakawa, Satoshi
• Primary Examiner(s): Mengistu, Amare
• Application Number:
  US08/103,174
• Time in Patent Office: 2,916 Days
• Field of Search: 340/716, 340/717, 340/767, 340/784, 340/793, 358/241, 345/36, 345/38, 345/48, 345/50, 345/55, 345/63, 345/81, 345/102, 345/147, 348/801, 359/48, 359/84, 395/200
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/30 using electroluminescent panels
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

An image display apparatus including an active display device, which is divided into picture elements, and a passive display device, which is divided into picture elements and which is superposed upon the active display device. The image display apparatus has-a high luminance resolution and a high definition.

Claims

1. A flat type display apparatus comprising:

a substrate;

an active display device, on said substrate, having a plurality of picture elements arranged in a two dimensional matrix form, wherein each of the plurality of picture elements of said active display device emits a back light having a light intensity with a plurality of levels of gradation;

a transmission type passive display device, superposed on said active display device, having a plurality of picture elements arranged in a two dimensional matrix form, wherein each of the plurality of picture elements of said transmission type passive display device has a light transmittance; and

a control circuit receiving an image signal and based on a first portion of the image signal independently controlling the light transmittance of each of the picture elements of said transmission type passive display device so as to cause each of the picture elements to assume one of a plurality of gradation levels and based on a second portion of the image signal independently controlling the light intensity of each of the picture elements of said active display device so as to take on one of a plurality of intensities thereby increasing the dynamic range of gradation levels of the passive display device,

wherein said passive display device is divided into picture elements of a finer resolution than said active display device.

2. An apparatus as defined in claim 1 wherein said passive display device is selected from the group consisting of a liquid crystal display device and an electrochromic display device.

3. An apparatus as defined in claim 1 wherein said active display device is selected from the group consisting of an electroluminescence panel, a plasma display panel, and a light emitting diode panel.

4. An apparatus as defined in claim 1 wherein said active display device is controlled so as to improve luminance resolution of said apparatus.

5. An apparatus as defined in claim 1 wherein said active display device comprises an electroluminescence panel, and said transmission type passive display device comprises a liquid crystal panel.

6. An apparatus as defined in claim 1 wherein the number of picture elements of said active display device and the number of picture elements of said transmission type passive display device are equal.

7. An apparatus as defined in claim 1 wherein in response to said control circuit receiving the image signal said control circuit produces, based on the first portion of the image signal, a first control signal for controlling the light transmittance of each of the picture elements of said transmission type passive display device superposed on one of the picture elements of said active display device, and produces, based on the second portion of the image signal, a second control signal for controlling the light intensity of said one of the picture elements of said active display device.

8. An apparatus as defined in claim 1, wherein the control circuit independently controls the light intensity of a picture element of said active display device based on a representative value of the second portion of the image signals corresponding to picture elements of said passive display device superposed on the picture element of said active display device.

9. An apparatus as defined in claim 8, wherein the representative value is a median value of the second portion of the image signals corresponding to picture elements of said passive display device superposed on the picture element of said active display device.

10. An apparatus as defined in claim 8, wherein the representative value is a mean value of the second portion of the image signals corresponding to picture elements of said passive display device superposed on the picture element of said active display device.