Variable reflectivity notch filter and optical devices using same

• US 8,294,993 B2
• Filed: 07/26/2010
• Issued: 10/23/2012
• Est. Priority Date: 07/26/2010
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Niesten, Maarten
• Primary Examiner(s): Harrington, Alicia M
• Application Number:
  US12/843,424
• Publication Number:
  US 20120019923A1
• Time in Patent Office: 820 Days
• Field of Search: 359/627, 359/630, 359/631, 359/634, 359/636, 359/359, 359/583, 359/584, 359/589, 345 7- 9
• US Class Current: 359/630
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/104 for use with scanning systems scanning systems G02B26/10
• CPC Class Codes: G02B 27/142 Coating structures, e.g. thin films multilayers
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44
• CPC Class Codes: G02B 5/26 Reflecting filters G02B5/28 takes precedence
• CPC Class Codes: G02B 5/289 Rugate filters

Abstract

A variable reflectivity notch filter (100), suitable for use with a laser image projection source (1001) is provided. The variable reflectivity notch filter (100) defines a transmission curve (101) having a plurality of reflective peaks (102,103,104) each centered about a predetermined wavelength (105,106,107), which can correspond to output wavelengths from laser sources. Reflective peaks (204) corresponding to wavelengths that change with temperature are configured with wider widths (223) and lesser reflectivities (210) than are other reflective peaks (202,203). To provide enhanced color balance, lasers (821) corresponding to these reflective peaks (204) can be driven at higher output power. Variable reflectivity notch filters (100) are suitable for use in head-up displays as well as other applications.

Claims

1. An image projection system having a display that is at least partially transmissive and partially reflective, the image projection system comprising:

a laser projection source having a controller configured to direct laser light to form an image on a display surface; and

a reflective layer integrated with the display surface, wherein the reflective layer comprises a variable reflectivity notch filter defining a transmission curve comprising a plurality of reflective peaks centered about predetermined wavelengths of light, each reflective peak having an associated reflectivity, wherein a reflectivity of at least one peak is different from a reflectivity of at least another peak, wherein the laser projection source comprises a plurality of laser sources each configured to emit light centered at a predetermined wavelength, wherein the predetermined wavelength changes as a function of temperature across a predefined range from a minimum wavelength to a maximum wavelength, wherein the plurality of reflective peaks are configured to at least partially reflect the minimum wavelength and the maximum wavelength.

2. The image projection system of claim 1, wherein:

the predefined range spans at least between −

30 degrees centigrade to +85 degrees centigrade;

the plurality of laser sources comprise at least a red laser source; and

one maximum wavelength is at least 20 nanometers greater than a corresponding minimum wavelength.

3. The image projection system of claim 1, wherein the reflective peak configured to reflect red light has a reflectivity of between one and fifty percent, wherein another reflective peak configured to reflect one of blue light or green light has a reflectivity of between fifty and one hundred percent.

4. The image projection system of claim 3, wherein the reflective peak has a peak width twice the another reflective peak.

5. The image projection system of claim 3, wherein the plurality of laser sources comprise at least a red laser and at least another laser, wherein the at least the red laser is configured to emit more light than the at least another laser such that light from the red laser reflected from the reflective layer and light from the at least another laser reflected from the reflective layer have substantially similar luminous intensities.

6. The image projection system of claim 1, wherein the plurality of laser sources comprise at least a red laser and at least another laser, wherein the at least the red laser is driven with a higher current than the at least another laser so as to emit more light than the at least another laser.