Integrated light sensor for an active matrix liquid crystal display panel

• US 5,831,693 A
• Filed: 02/22/1996
• Issued: 11/03/1998
• Est. Priority Date: 02/22/1996
• Status: Expired due to Term

• Current Assignee: Honeywell (Honeywell International Inc.)
• Original Assignee: Honeywell (Honeywell International Inc.)
• Inventors: McCartney, Richard Isaiah Jr., Sarma, Kalluri R.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGO, HUYEN LE
• Application Number:
  US08/606,910
• Time in Patent Office: 985 Days
• Field of Search: 359/55, 359/59, 359/60, 359/67, 359/68, 349/42, 349/70, 349/106, 349/108, 349/116
• US Class Current: 349/42
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G02F 1/1335 Structural association of cells with optical devices, e.g. polarisers or reflectors
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

The active matrix liquid crystal display panel comprises a matrix of predetermined color filters, arranged in a predetermined configuration within a viewing area, deposited on a first substrate, and a first plate of an activating element is deposited over the matrix of predetermined color filters. A plurality of second plates of the activating element is deposited on a second substrate opposite each color filter. When a predetermined second plate is activated, light is permitted to pass through the corresponding filter, the light exiting the first substrate having the color of the corresponding filter. A plurality of thin film transistors is deposited on the second substrate and forms the control elements, each control element corresponding to a corresponding second plate of the activating element, the control element selecting predetermined second plate in response to control signals. The display panel includes a liquid crystal material filled in a space between the first and second substrate. At least one photodiode is deposited on the second substrate outside the viewing area, the photodiode generating a voltage proportional to ambient lighting conditions around the exterior of the first substrate. The photodiode is fabricated utilizing the same steps utilized in fabricating the display panel.

Claims

1. An active matrix liquid crystal display panel comprising:

a) a matrix of predetermined color filters, arranged in a predetermined configuration within a viewing area, deposited on a first substrate;

b) a first plate of an activating means deposited over the matrix of predetermined color filters, the activating means being a clear conducting material;

c) a plurality of second plates of the activating means, deposited on a second substrate opposite each color filter, such that when a predetermined second plate is activated, light is permitted to pass through the corresponding filter, the light exiting the first substrate having the color of the corresponding filter;

d) a plurality of control means, each control means corresponding to each of the second plates of the activating means, for selecting a predetermined second plate in response to control signals;

e) a liquid crystal material filled in a space between the first and second substrate;

f) at least one photodiode deposited on the second substrate outside the viewing area, the photodiode sensing ambient lighting conditions around the exterior of the first substrate;

g) a backlight positioned exterior to the second substrate; and

h) a control circuit, connected to the photodiode and the backlight, generating a voltage proportional to ambient lighting and controlling the intensity of the light outputted from the backlight based on the ambient lighting sensed by the photodiode.

2. An active matrix liquid crystal display panel according to claim 1, wherein the control means are thin film transistors deposited on said second substrate.

3. An active matrix liquid crystal display panel according to claim 2 wherein the predetermined color filters include:

a) a red filter;

b) a green filter;

c) a blue filter all arranged in a predetermined geometric pattern.

4. An active matrix liquid crystal display panel according to claim 3 wherein the first and second substrate is a glass substrate.

5. An active matrix liquid crystal display panel according to claim 1, further comprising at least one reverse photodiode deposited on the second substrate outside the viewing area, the reverse photodiode generating a voltage proportional to the intensity of the light outputted from the backlight.

6. An active matrix liquid crystal display panel according to claim 5, wherein the voltage outputted from the reverse photodiode is used to control the output of the light from the backlight, the output of the light from the backlight being determined as a function of the ambient light determined from the photodiode.

7. An active matrix liquid crystal fabrication method comprising fabricating a first glass substrate with a color filter array and the common first plate of an activating means, and fabricating the second glass substrate with the thin film transistor array with the plurality of second plates of the activating means opposite to the respective color filter array elements on the first glass substrate, and fabrication of the second glass substrate further comprising fabrication of at least one photodiode out side the display viewing area for the purpose of sensing the display ambient light level to control the backlight intensity and the display brightness.

8. An active matrix liquid crystal display fabrication method according to claim 7, where in the thin film transistors and the photodiodes are fabricated using the photosensitive amorphous silicon semiconductor.

9. An active matrix liquid crystal display fabrication method according to claim 8, where in the fabrication processes for fabricating the amorphous silicon thin film transistors encompass the fabrication processes for fabricating the amorphous silicon photodiodes.

10. An active matrix liquid crystal display fabrication method according the claim 7, where in at least two photodiodes are fabricated outside the display viewing area, at least one photodiode sensing the display ambient light intensity through the first glass substrate, and at least one photodiode sensing the display backlight intensity through the second glass substrate.