Transmissive and reflective liquid crystal display

• US 4,315,258 A
• Filed: 02/15/1980
• Issued: 02/09/1982
• Est. Priority Date: 02/15/1980
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: McKnight, William H., Stotts, Larry B., Monahan, Michael A.
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US06/121,948
• Time in Patent Office: 725 Days
• Field of Search: 340/784, 340/765, 350/337, 350/338, 350/334, 350/330, 350/331
• US Class Current: 345/87
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 2203/09 transflective

Abstract

A visual display has an increased readout capability due to its operation the transflective mode. A source of ambient light and light for radiation through the display from the backside together assure the increased readout capability. Heretofore, ambient light would degrade or washout a display making it nearly impossible for monitoring personnel to decipher alphanumeric or pictoral displays due to the decreased contrast. A pair of linear polarizers sandwich a twisted nematic liquid crystal and have their polarization axes either parallel or mutually orthogonally disposed so that the crystal will present bright or dark areas in response to applied potentials. Because a partially transmitting mirror is interposed between the sandwiched liquid crystal and the radiating light source, the ambient light augments the radiated light to enhance the visual display.

Claims

1. An apparatus having the capability for providing a visual display in the transflective mode comprising:

means for providing a source of ambient light;

means for radiating light through a predetermined volume;

a nematic liquid crystal interposed between the ambient light providing means and the light radiating means in the predetermined volume for selectively rotating the polarization axis of transmitted and reflected light therethrough in select areas thereof in response to applied potentials to create relatively bright areas to a viewer located in the ambient light area when an applied potential is impressed thereacross;

first means disposed between the ambient light providing means and the nematic liquid crystal for polarizing the ambient light into a single linearly polarized component;

second means disposed between the light radiating means and the nematic liquid crystal for polarizing the radiated light into a single component, the first polarizing means and the second polarizing means being a pair of linear polarizers disposed in a parallel orientation; and

a "one way" mirror, partially transmissive and interposed between the second polarizing means and the light radiating means for partially transmitting portions of the radiated light and specularly reflecting portions of the ambient light, the twisted nematic liquid crystal creating relatively bright areas to a viewer located in the ambient light area when an applied potential is impressed thereacross whereby the contrast of the visual display is enhanced and washout is reduced.

2. An apparatus having the capability for providing a visual display in the transflective mode comprising:

means for providing a source of ambient light;

means for radiating light through a predetermined volume;

a nematic liquid crystal interposed between the ambient light providing means and the light radiating means in the predetermined volume for selectively rotating the polarization axis of transmitted and reflected light therethrough in select areas thereof in response to applied potentials to create relatively bright areas to a viewer located in the ambient light area when an applied potential is impressed thereacross;

first means disposed between the ambient light providing means and the nematic liquid crystal for polarizing the radiated light into a single component;

second means disposed between the light radiating means and the nematic liquid crystal for polarizing the radiated light into a single component, the first polarizing means and the second polarizing means being a pair of linear polarizers disposed in a mutually orthogonal orientation; and

a "one way" mirror, partially transmissive and interposed between the second polarizing means and the light radiating means for partially transmitting portions of the radiated light and specularly reflecting portions of the ambient light, the twisted nematic liquid crystal creates relatively dark areas to a viewer located in the ambient light area when an applied potential is impressed thereacross whereby the contrast of the visual display is enhanced and washout is reduced.