# US 2017/0289531 A1 · More reliable monochromatic stereoscopic image projector

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- Number: US 2017/0289531 A1
- Document ID: US20170289531A1
- Status: Published application
- Kind: A1
- Application number: 15/475,061
- Filed: 2017-03-30
- Published: 2017-10-05
- Earliest claimed: 2016-04-01
- Assignees: Thales
- Applicants: Thales
- Inventors: Philippe CONI; Aude GUEGUEN; Matthieu GROSSETETE
- Web page: https://patentgrep.com/patent/US20170289531A1

## CPC

- H04N 13/363: using image projection screens (volumetric display H04N13/388)
- B64D 43/00: Arrangements or adaptations of instruments
- G02B 27/0101: {characterised by optical features (G02B27/0172 takes precedence)}
- G02B 30/23: using wavelength separation, e.g. using anaglyph techniques
- G02B 30/24: involving temporal multiplexing, e.g. using sequentially activated left and right shutters
- H04N 13/279: the virtual viewpoint locations being selected by the viewers or determined by tracking
- H04N 13/324: Colour aspects
- H04N 13/334: using spectral multiplexing
- H04N 13/341: using temporal multiplexing
- H04N 13/344: with head-mounted left-right displays
- H04N 13/365: using digital micromirror devices [DMD]
- G02B 2027/0114: {comprising dichroic elements}
- G02B 2027/0118: {comprising devices for improving the contrast of the display / brillance control visibility}
- G02B 2027/0134: {of stereoscopic type}
- H04N 2213/001: Constructional or mechanical details
- H04N 2213/008: Aspects relating to glasses for viewing stereoscopic images
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

The general field of the invention is that of monochromatic stereoscopic image projectors including two light sources that illuminate two imagers, the radiation of the two light sources having a spectral distribution centred on a central wavelength, the first imager and the second imager being connected to a generator of stereoscopic image pairs. The image projector includes a dichroic separating filter that transmits the portion of the spectrum below the central wavelength and that reflects the portion of the spectrum above this central wavelength. The first light source and the second light source are arranged symmetrically on either side of the dichroic separating filter. The image projector operates cyclically, each cycle including two alternations. Each alternation consists in changing the emission source and in switching to the two displays the left and right images emitted by the generator of image pairs.

## Claims

### Claim 1

Monochromatic stereoscopic image projector including a first light source, a second light source, a first imager and a second imager, the radiation of the two light sources having the same spectral distribution centred on a central wavelength, the first imager and the second imager being connected to a generator of stereoscopic image pairs, each pair comprising what is called a “left” image and what is called a “right” image;
wherein:
the image projector includes a dichroic separating filter that transmits the portion of the spectrum emitted by the light sources below the central wavelength and that reflects the portion of the spectrum emitted by the light sources above the central wavelength, or vice versa;
the first light source and the second light source are arranged symmetrically on either side of the dichroic separating filter and are arranged so as to illuminate the first and the second imager;
the image projector operates cyclically, each cycle including two alternations,
in the first alternation, the image generator emits a first pair of stereoscopic images including a first left image and a first right image, the first left image being displayed by the first display and the first right image being displayed by the second display, the first light source is activated and the second light source is turned off,
in the second alternation, the image generator emits a second pair of stereoscopic images including a second left image and a second right image, the second left image being displayed by the second display and the second right image being displayed by the first display, the first light source is turned off and the second light source is activated.

### Claim 2 (depends on 1)

Monochromatic stereoscopic image projector according to claim 1, wherein the first light source and the second light source are light-emitting diodes, the central wavelength being located at about 530 nanometres.

### Claim 3 (depends on 1)

Monochromatic stereoscopic image projector according to claim 1, wherein the frequency of the cycle is comprised between 100 Hz and 400 Hz.

### Claim 4 (depends on 1)

Monochromatic stereoscopic image projector according to claim 1, wherein the first display and the second display are DMD micromirror displays.

### Claim 5

Displaying system including means for generating stereoscopic images of a preset object, a device for displaying said stereoscopic images including a stereoscopic image projector and a semi-transparent screen and a pair of stereoscopic glasses, the means for generating stereoscopic images, the displaying device, the semi-transparent screen and the pair of stereoscopic glasses being arranged so that the stereoscopic image of the preset object appears, through the stereoscopic glasses, at a preset distance from the semi-transparent screen, wherein
the stereoscopic image projector comprises a monochromatic stereoscopic image projector including a first light source, a second light source, a first imager and a second imager, the radiation of the two light sources having the same spectral distribution centred on a central wavelength, the first imager and the second imager being connected to a generator of stereoscopic image pairs, each pair comprising what is called a “left” image and what is called a “right” image;
wherein:
the image projector includes a dichroic separating filter that transmits the portion of the spectrum emitted by the light sources below the central wavelength and that reflects the portion of the spectrum emitted by the light sources above the central wavelength, or vice versa;
the first light source and the second light source are arranged symmetrically on either side of the dichroic separating filter and are arranged so as to illuminate the first and the second imager;
the image projector operates cyclically, each cycle including two alternations,
in the first alternation, the image generator emits a first pair of stereoscopic images including a first left image and a first right image, the first left image being displayed by the first display and the first right image being displayed by the second display, the first light source is activated and the second light source is turned off,
in the second alternation, the image generator emits a second pair of stereoscopic images including a second left image and a second right image, the second left image being displayed by the second display and the second right image being displayed by the first display, the first light source is turned off and the second light source is activated,
the pair of glasses includes a first filter placed in front of the right eye and a second filter placed in front of the left eye, the first filter transmitting all of the spectrum except for the portion of the spectrum emitted by the light sources below the central wave wavelength and the second filter transmitting all of the spectrum except for the portion of the spectrum emitted by the light sources above the central wave wavelength.

### Claim 6 (depends on 5)

Displaying system according to claim 5, wherein the system includes means for detecting the relative position of the pair of glasses with respect to the position of the semi-transparent screen and means for computing the stereoscopic images so that the position of the stereoscopic image of the object is fixed in a preset coordinate system and is independent of the position of the stereoscopic glasses.

### Claim 7 (depends on 5)

Displaying system according to claim 5, wherein the preset distance is comprised between a few centimetres and optical infinity.

### Claim 8 (depends on 5)

Displaying system according to claim 5, wherein the displaying system is an aircraft cockpit system.