Display device comprising fluorescent enhanced reflective holographic illumination

• US 5,594,560 A
• Filed: 03/07/1994
• Issued: 01/14/1997
• Est. Priority Date: 03/07/1994
• Status: Expired due to Term

• Current Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Jelley, Kevin W., Valliath, George T., Chen, Alan G.
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): CHANG, AUDREY Y
• Application Number:
  US08/206,360
• Time in Patent Office: 1,044 Days
• Field of Search: 359/15, 359/19, 359/13, 359/69, 359/70, 359/50, 385/12
• US Class Current: 359/15
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133617 Illumination with ultraviolet light; Luminescent elements or materials associated to the cell

Abstract

A display device (10) includes a display panel, such as a liquid crystal panel (12), in combination with a reflective holographic optical element (14) that redirects ambient light for illuminating the display. The light redirected by the holographic element is limited to a predetermined spectral band. Fluorescent film (16) is included for absorbing light outside the spectral band of the holographic element and re-emitting light within the spectral band to increase the light redirected by the holographic element and thus increase the apparent brightness of the display.

Claims

1. A display device illuminatable by diffuse ambient light and comprising

a display panel having a front side for viewing a display and a back side opposite the front side, said display panel comprising a transparent region,

a reflective holographic optical element effective for redirecting light having a wavelength within a predetermined spectral band in a reflection pattern and optically coupled to the display panel for receiving light transmitted through the panel and for directing light in the reflection pattern toward the back side of the display panel, whereupon light redirected toward a transparent region of the display panel is transmitted through the display panel to form a bright area for the display, and

a fluorescence element containing a fluorescent compound that absorbs light having a wavelength outside the predetermined spectral band and emits fluorescent light having a wavelength within the predetermined spectral band and optically coupled to the display panel and the reflective holographic optical element to receive light transmitted through the display panel and to emit fluorescent light toward the reflective holographic optical element, whereupon fluorescent light received by the reflective holographic optical element is redirected within the reflection pattern to enhance brightness of the bright area for the display.

2. The display device in accordance with claim 1 wherein the fluorescence element is a polymeric film containing the fluorescent compound and is interposed between the back side of the display panel and the reflective holographic optical element.

3. A liquid crystal display device illuminatable by diffuse ambient lighting and adapted for forming a display that includes a bright area, said liquid crystal display device comprising

a liquid crystal panel having a front side for viewing a display and a back side opposite the front side, said display panel comprising a region that is switchable between a transparent state for transmitting polarized light and an opaque state,

a reflective holographic optical element having a front face facing the back side of the liquid crystal panel for receiving polarized light transmitted through the liquid crystal panel and for redirecting light having a wavelength within a predetermined spectral band in a reflection pattern to illuminate said back side, whereupon light redirected toward a transparent region of the liquid crystal panel is transmitted through the liquid crystal panel to form a bright area for the display, and

a fluorescent film interposed between the liquid crystal panel and the reflective holographic optical element and effective to absorb light transmitted through the liquid crystal panel and having a wavelength outside the predetermined spectral band and to emit fluorescent light having a wavelength within the predetermined spectral band, whereupon fluorescent light emitted by the fluorescent film is received by the reflective holographic element and is redirected in the reflection pattern toward the liquid crystal panel to enhance brightness of the bright area.

4. A liquid crystal display device in accordance with claim 3 wherein the fluorescent film is composed of a fluorescent compound dispersed in a transparent polymeric matrix.

5. A liquid crystal display device in accordance with claim 3 wherein the fluorescent film is attached to the back side of the liquid crystal panel and to the reflective holographic optical element to form an integral component.