WO1994000956A1

WO1994000956A1 - Optical switching system for three-dimensional sequential video television glasses

Info

Publication number: WO1994000956A1
Application number: PCT/FR1993/000616
Authority: WO
Inventors: Gabriel Drouard
Original assignee: Deguerville, Jeannine; Deguerville, Jacques
Priority date: 1992-06-22
Filing date: 1993-06-21
Publication date: 1994-01-06
Also published as: FR2692745A1; FR2692745B1

Abstract

An electromechanically-switched glasses system for flicker-free sequential video television at a field frequency of 50-120 Hz. The system is based not on mask/unmask switching (which is too slow when synchronous with the field frequency) but on the number of light pulses received by the eye in the time interval of one frame, however long that may be, at a frequency no higher than 10 ms. The system comprises a Fresnel, microprism or optical fibre mask which lets the light beam through without a picture and without cancelling out the three-dimensional effect, either with continuous pulses during the unmasked time interval, or with sequential pulses lasting no longer than 10 ms during the masked time interval, regardless of the mechanical mask/unmask switching frequency which at all times remains synchronous with the field frequency. Visual perception is equivalent to the 100/120 Hz during the time interval, of whatever length, of one frame switching at 50-92 Hz.

Description

OPTICAL SWITCHING SYSTEM

FOR STEREOSCOPIC VISION GLASSES

IN SEQUENTIAL VIDEO

For the relief vision, on a monitor or a television, of stereoscopic video images which are composed of a frame of the right channel and a frame of the left channel, and seen successively - what is called the Sequential video - glasses formulas that use PLZT ceramics and especially with liquid crystals, have the drawback of considerably reducing the light density by 70 to 90%: when they do not modify the chromatism.

In patent PCTAVO-A-9.004-312 of October 12, 1989 - FR / 8904353, incorporating patent FR of 12/10/88 n ° FR / 88/3432 we recommended, to correct this defect, to use glasses alternating switching right eye / left eye by electronic rotation of a shutter comprising an opening on image and an occultation of image by black mask; switching from the frequency of 50 HZ (1,500 rpm and 25 frames / sec), up to 120 Hz // by acting on the voltage to increase the speed of the shutter // (3,600 rpm and 60 images /).

The gain in light density is 50% to 60% compared to other systems. This system does not entirely remove the flicker due to switching unless it reaches a certain speed. This remark is valid, whatever the optoelectronic, electromechanical shutter model, etc.

Experience shows that the speed required to avoid this flicker is greater than that required by the transition / frame from 50 HZ to 80/92 HZ (1,500 to 2,760 rpm). At these frequencies, the shutter does not allow, unless modified, a qualitative and long-term vision.

Current art advocates solutions whose very statement indicates that they decrease but do not eliminate the flicker. For liquid crystal glasses, the SHARP CORP patent. SHINICHI-TACHIKI - March 31, 1989. J.P. recommends a light pulse during the erasure / league time at the start and end of frames, ie a duration of 1 mis, 5; insufficient time to suppress flickering. For glasses with electromechanical switching, the MATSUSHITA DENKI SANGKO KK patent of 2/12/81 JP A. 56-156 079 proposes an obturation of the image by a gray material which, by attenuating the sudden contrast between darkness and light decreases flickering but does not suppress it.

The first objective of the innovation is the complete elimination of flickering due to electromechanical switching for a clear vision of the image, from the most used frequency - 50/60 Hz - to frequencies of 100 -120 Hz. Hence the second objective: the modification of the occultation system by adapting it to the data of ocular physiology. These data are:

1 - For a stable and quality vision, without flickering, the need for a light stimulus every 10 times at least - known principle and applied in televisions with frame memory cards.

In the case of glasses, the shutter must mark, during the darkening time,

3,000 pulses per eye per minute, twice the speed of the passage / frame at

50 Hz. 2 - The reaction of the eye to light stimulation whatever are contained: single beam or image; that he can record it and define it according to his perception.

In the case of glasses with electromechanical switching, the modification sought takes account of these two data to obtain the 1st by the use of the 2nd.

Advantage of optical switching over optoelectronic switching. First characteristic of the innovation system:

The switching of the shutter being always composed of an opening and a closing, ie, of a vision and a non-vision of image, the closing with occultation of image is replaced by continuous stimuli or successive which make adequate the relation between the defined ocular requirements (stimuli per 10 mis) and the constraints of time of passage / frame according to the frequencies. The eye receives stimuli or successive on 10 set (or less) or continuous of 10 set (at least) during the passage time, whatever it is, of an image or two frames.

During the muting time, the light pulse received can be continuous (Fig 1) or separated into two equal pulses (Fig. 2) by a complete extinction zone.

Another feature of innovation is that this system makes the passage / frame and switching independent of each other on the one hand and the number of stimuli received by the eye in the same switching time on the other hand.

In this system, the opening-closing switching remains synchronous with the frequency of the passage / frame, by automatic synchronization on the frequency / frame transmitted by infrared transceiver to the regulation circuit; but the number of light pulses is always equivalent to 100 Hz / 120 Hz, regardless of the frequency of the passage / frames.

The vision of the image becomes clear at a frequency of passage / frame lower than the theoretical frequency defined to suppress flickering.

Another feature of the system, in innovation, the device for occulting the image in the shutter is made of a translucent optical material, inserted in the occultation phase over 180 °, either a Fresnel or microprisms with steps and angles which can be different either from optical fibers or any other material which lets pass almost all of the light pulse, without image vision; therefore, without canceling the stereoscopic effect.

Depending on the material used and the optical characteristics selected, the image remains in the field of vision or is translated totally or partially outside the field of vision. In the first case, a slight frosting obscures the image by letting the stimuli pass to the eye.

In the second case, no frosting; the passage is almost integral of the light beam and the pulses.

In both cases, the pulses are either continuous or successive. Another characteristic of the innovation system, the image of the screen being of too weak a radiation to create a beam with strong light pulse, the beam comes from a source located above or next to the screen. It emits a concentrated ray outside the image field, in the optical field of the shutter which transforms the rays emitted into a beam with high density of light and strong pulses during the time, whatever it is, of the occultation. To illustrate with an example, Figure 1 gives the general configuration of the right and left shutters.

1 - Mechanical configuration: the two shutters are in phase opposition with a single aperture on image (10 and a single occultation (11) by 360 ° rotation either a complete image or two frames. The switching speed is synchronized by photodiode ( 13) (linked to all digital software which receives the switching signals from an infrared transmitter - receiver; the transmitter placed on the monitor or television and the receiver on the telescope) with the frame passage every 180 ° and 20 mis (12). The occultation covers the erasure time / leagues at the start and end of opening, at the top of change / frame, ie 7 ° at the start and 7 ° at the end of frame (15), ie total of 1 bet 5.

The occultation therefore extends over 194 ° for an opening of 166 °. This mechanical configuration can be changed from 100 to 120Hz to keep the rotation speed at an average level. The shutter includes, on 360 ° a double opening and a double optical occultation. Each complete rotation represents two images or 4 frames for a speed equivalent to that of 50 Hz (Fig. 3).

All data found in the cited patents.

Add that the rotation is ensured by a single stepping motor in the center.

2 - Optical configuration

The opening creates continuous pulses on 166 ° with image vision on 18mls 5. The occultation, in the example, is in Fresnel (14) whose optics covers 180 °, returns the image outside the field of vision and lets the light beam pass by creating as many continuous pulses on 18 mis.

This light beam can be divided into two equal parts by an intermediate zone of total extinction (Fig. 2) to create two successive series of pulses during the closing time.

Claims

1 - Mechanical and optical switching device for vision glasses in relief of stereoscopic video images composed of a frame of the right channel and a frame of the left channel, successive, with suppression of flicker due to mechanical switching and with the maximum light density, characterized in that it comprises an optical shutter with opening-closing switching based, not on a disappearance and a successive vision of images but on a series of strong light pulses without density reduction, corresponding the number of light stimuli necessary for a retinal perception equivalent to a frequency of 100 Hz during the duration, whatever it is, of a complete switching of image or two fields, either in continuous pulses, or in successive pulses of a duration equal to or less than 10 milliseconds, all independent of the frequency of the mechanical switching synchronous with the frame frequency; this can be lower than the defined theoretical switching frequency to suppress flickering.

2 - Device according to claim 1, characterized in that the first strong light pulse providing the vision of the continuous image lasts the time of the opening and that the second pulse corresponding to the duration of the occultation of the image is a light beam from a translucent optical disk produced in Fresnel, or in microprisms or any other suitable optical system, directing towards the eye, without image vision and without interruption of the stereoscopic effect, almost all of this light pulse either in a single pulse (fig. 1) continuously, or in a double pulse, equal to or less than 10 set each, separated by a brief complete extinction (fig. 2).

Device according to Claim 1, characterized in that it is applicable to all the scanning frequencies from 50/60 Hz to 100/120 Hz, by automatic synchronization of the mechanical switches on the frequency / frame transmitted by infrared transceiver to the circuit. regulation, the number of light pulses received always being equivalent to 100/120 Hz.

- Device according to claims 1 and 2 characterized in that a light source, located above or next to the monitor screen or the television, emits a concentrated ray, outside the image field but in the field of the optical shutter transforming the emission of these rays into dense light beams and strong pulses, over time, whatever it is, of the occultation.

5 - Device according to claim 1 CHARACTERIZED in that, for a frequency / frame from 100 to 120 Hz, are doubled, for a complete rotation of 360 °, the opening and closing of the switch while maintaining the speed of rotation at the speed of 50/60 Hz (fig. 3).