Glare preventive rear view mirror

• US 4,693,558 A
• Filed: 03/20/1985
• Issued: 09/15/1987
• Est. Priority Date: 03/28/1984
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Inventors: Nakaho, Junichi, Kato, Shigeru, Shibahara, Makoto
• Primary Examiner(s): Evans, Arthur G.
• Application Number:
  US06/713,684
• Time in Patent Office: 909 Days
• Field of Search: 350/331 R, 350/332, 350/334, 350/642, 350/600, 250/215, 250/213 R
• US Class Current: 349/195
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors

Abstract

A rear view mirror assembly comprising a liquid crystal cell of guest-host type which consists of a layer of dichroic dyestuff added nematic liquid crystal and a pair of transparent plates sandwiching the liquid crystal therebetween. A transparent electrode is formed on the inside surface of each plate by means of conductive coating. A quarter wave phase difference filter is mounted on the backside of one of the plates. A flat mirror is mounted on the backside of the quarter wave phase difference filter. A photo-sensitive means receives light passing through the liquid crystal cell and an optical polarization filter in turn and produces a photo-detector signal. A control circuit controls voltage applied to the electrodes of liquid crystal cell so that the magnitude of photo-detector signal may become equal to the predetermined level. The predetermined level is changeable in accordance with the magnitude of detector signal produced by another photo-sensitive means for detecting circumjacent light.

Claims

1. A glare preventive rear view mirror comprising:

a liquid crystal cell of the guest-host type including a pair of parallel transparent plates each having a transparent electrode on the inwardly desposed surface thereof and a mixture of nematic liquid crystal and dichroic dyestuff encapsulated between said transparent plates;

a mirror assembly including a quarter wave phase difference filter and a flat mirror each disposed on the side of said liquid crystal cell opposite a light receiving side thereof;

an optical polarization filter mounted on a side of said liquid crystal cell;

a photo-sensitive means for receiving light passing through at least said liquid crystal cell and said optical polarization filter, said photo-sensitive means being adapted to produce a photo-receptor signal in accordance with a quantity of received light; and

a control circuit means for controlling voltage applied to the electrodes of said liquid crystal cell so as to adjust the quantity of light passing through said liquid crystal cell and so that the magnitude of the photo-receptor signal can correspond with a predetermined level.

2. A glare preventing rear view mirror as in claim 1, wherein said photo-sensitive means includes means for producing a photo-detector signal in accordance with sensed ambient light and wherein said control circuit means includes means for changing said predetermined level in accordance with the magnitude of said photo-detector signal.