WO2005091047A2

WO2005091047A2 - Device for fast modulating a slowly operated light source

Info

Publication number: WO2005091047A2
Application number: PCT/IL2005/000291
Authority: WO
Inventors: Mordekhai Velger; Jephtah Lorch
Original assignee: Elop Electro-Optics Industries Ltd.; Flixel Ltd.
Priority date: 2004-03-22
Filing date: 2005-03-15
Publication date: 2005-09-29
Also published as: WO2005091047A3

Abstract

Device for producing high frequency modulated light, the device including at least one slowly operated light source being characterized by a maximal operation rate, and at least one micro shutter being located in an optical path to the slowly operated light source, the micro shutter being operative to modulate light passing there through, by alternately moving to an open state and a closed state, at a shutter modulation rate which is greater than the maximal operation rate, thereby producing the high frequency modulated light.

Description

DEVICE FOR FAST MODULATING A SLOWLY OPERATED LIGHT SOURCE

FIELD OF THE DISCLOSED TECHNIQUE The disclosed technique relates to optical systems in general, and to methods and systems for displaying an image, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE Optical systems which display an image by modulating light are known in the art. These systems produce the image by controlling the on and off states of each of a plurality of light sources arranged in a matrix. US Patent No. 6,320,559 B1 issued to Yasukawa et al., and entitled "Head-Mounted Image Display Device and Data Processing Apparatus Including the Same", is directed to a system for enabling an operator to select one of a plurality of virtual sub-screens by depressing a foot switch while looking upward, and view downward toward a work piece located on a desk. The system includes a head-mounted image displaying device, and a computer. The head-mounted image displaying device includes a spectacles-like frame, a device circuit, a connection cord, a liquid crystal panel, a back light, an enlarging lens, an angle sensor, an infrared ray LED, a photosensor and a foot switch. The spectacle-like frame include a lower part and an upper part. The device circuit is connected with the computer via the connection cord. The foot switch is connected with the computer. The liquid crystal panel is located between the back light and the enlarging lens in front of the eyes of the operator. The liquid crystal panel, the backlight and the enlarging lens are located at the upper part. The device circuit decodes the image information received from the computer and the liquid crystal panel displays an image of a virtual sub-screen. The backlight illuminates the image and the enlarging lens directs an enlarged image to the eyes of the operator, thereby enabling the operator to see a virtual sub-screen. The angle sensor detects the direction and angle of the head of the operator while it moves vertically and horizontally. The infrared ray LED and the photosensor detect the line of sight and the winking of the operator. The operator can see the virtual sub-screen by looking at the upper part and see the work piece by looking downward through the lower part. The angle sensor detects the movement of the head and the computer scrolls the virtual sub-screen according to the movement of the head, such that the operator can see a large number of virtual sub-screens by moving the head. The movement of the head corresponds to the movement of a mouse in a Windows screen and the foot switch corresponds to a switch on the mouse. The operator specifies a selected virtual sub-screen by pressing on the foot switch. US Patent No. 6,157,352 issued to Kollin et al., and entitled

"Virtual Retinal Display with Expanded Exit Pupil", is directed to a retinal display device. The retinal display device includes an image data interface, a light source, an optics sub-system, a scanning sub-system, an exit pupil expanding apparatus and an eyepiece. The light source includes a red light emitting diode (LED), a green LED, a blue LED a first modulator, a second modulator, a third modulator and a beam combining apparatus. The optics sub-system includes an objective lens and a cylindrical lens. The scanning sub-system includes a first resonant scanner and a second resonant scanner. The image data interface is connected to the first modulator, the second modulator, the third modulator, and to the scanning sub-system. The optics sub-system is located between the light source and the scanning sub-system. The exit pupil expanding apparatus is located between the scanning sub-system and the eyepiece. Image data interface produces a signal respective of an image, according to the output of a computer, and provides this signal to the light source and to the scanning sub-system. The first modulator, the second modulator and the third modulator modulate the light received from the red LED, the green LED and the blue LED, respectively, according to the signal received from the image data interface, and the beam combining apparatus produces a combined light beam by combining the three modulated light beams. The optics sub-system converges the combined light beam on the scanning sub-system, and the scanning sub-system scans the converged light beam vertically and horizontally, according to the signal received from the image data interface. The exit pupil expanding apparatus expands the scanned light beam and the eyepiece converges the expanded light beam on a retina of an eye of a user. International Publication No. WO 03/048836 A2 entitled "Display Devices" is directed to a pixel fabricated in a microelectromechanical system (MEMS) technology. The pixel includes a flipping panel, a closing electrode, an opening electrode, a pair of clutch electrodes, a stopping nub, a row locking electrode, a column locking electrode, a levitation electrode, and a pair of sockets. The flipping panel includes a pair of rounded axels which fit into the respective socket. Each socket includes a knife edge, a side motion constraint and an upper constraint. The closing electrode, the opening electrode, the pair of clutch electrodes, the row locking electrode and the column locking electrode, the knife edges, and the stopping nub are deposited on a first layer. The flipping panel, the rounded axels, and the side motion constraints are deposited on a second layer above the first layer. The levitation electrode and the upper constraints are deposited on a third layer above the second layer. In order to open the flipping panel, the clutch electrodes are simultaneously energized, thereby pulling the rounded axels down and ensuring electrical contact between the rounded axels and the respective knife edge. The opening electrode and the levitation electrode are likewise energized, thereby lifting the flipping panel off the substrate. At this point both the row locking electrode and the column locking electrode are grounded. The flipping panel rotates about the pair of rounded axels, until a tail of the flipping panel makes contact with the stopping nub. In order to close the flipping panel, the closing electrode is energized, thereby detaching the tail from the stopping nub. Thereafter, the levitation electrode is energized, thereby attracting the flipping panel. The flipping panel rolls on the rounded axels toward the substrate.

SUMMARY OF THE DISCLOSED TECHNIQUE It is an object of the disclosed technique to provide a novel method and device for producing high frequency modulated light. In accordance with the disclosed technique, there is thus provided a device for producing high frequency modulated light. The device includes at least one slowly operated light source being characterized by a maximal operation rate, and at least one micro-shutter being located in an optical path to the slowly operated light source. The micro-shutter is operative to modulate light passing there through, by alternately moving to an open state and a closed state, at a shutter modulation rate which is greater than thejmaximal operation rate, thereby producing the high frequency modulated light. In accordance with another aspect of the disclosed technique, there is thus provided a device for producing a selected color of each of a plurality of multi-color pixels by using a plurality of slowly operated light sources associated with a respective one of the multi-color pixels. Each of the slowly operated light sources emits light in a respective range of wavelengths of a color palette, and each of the slowly operated light sources is characterized by a maximal operation rate. The device includes a plurality of micro-shutters associated with the respective multi-color pixel. Each of the micro-shutters is located in an optical path to a respective one of the slowly operated light sources, and each of the micro-shutters is operative to modulate light passing there through, by alternately moving to a respective open state and a respective closed state, at a shutter modulation rate which is greater than the maximal operation rate. An opening period of the respective open state relative to a closing period of the respective closed state is selected to produce the selected color. In accordance with a further aspect of the disclosed technique, there is thus provided a method for producing a fast modulated image sequence. The method includes the procedure of modulating light of each of a plurality of slowly operated light sources, by controlling the opening and closure of each of a plurality of fast modulating micro-shutters. Each of the fast modulating micro-shutters is associated with a respective one of the slowly operated light sources. The openings and closures are controlled according to information received respective of an image from an image source. The openings and closures are controlled at a shutter modulation rate of a respective one of the fast modulating micro-shutters, greater than a maximal operation rate of the respective slowly operated light source, thereby producing the fast modulated image sequence.

BRIEF DESCRIPTION OF THE DRAWINGS The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: Figure 1 is a schematic illustration of a system for producing an image, constructed and operative in accordance with an embodiment of the disclosed technique; Figure 2A is a schematic illustration of a system for producing an image, constructed and operative in accordance with another embodiment of the disclosed technique; Figure 2B is a schematic illustration of an arrangement of one of the slowly operated light sources of the system of Figure 2A, and a respective micro-shutter array of the system; Figure 3A is a schematic illustration of a micro-shutter in a closed position, constructed and operative in accordance with a further embodiment of the disclosed technique; Figure 3B is a schematic illustration of the micro-shutter of Figure 3A, in an open position; Figure 4 is a schematic illustration of a spectacle incorporated with the system of Figure 1 , constructed and operative in accordance with another embodiment of the disclosed technique; and Figure 5 is a schematic illustration of a method for operating the system of Figure 1 , operative in accordance with a further embodiment of the disclosed technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS The disclosed technique overcomes the disadvantages of the prior art by controlling the opening and closure of a micro-shutter located in front of a slowly operated light source, at a rate which is greater than the maximum operation rate of the light source. According to another aspect of the disclosed technique, each pixel of a chromatic image includes a plurality of slowly operated light sources, each emitting light in one range of wavelengths of a color palette (e.g., red, green and blue), and a dedicated micro-shutter for modulating the respective light source. The color of each pixel is controlled by controlling the opening and closure of the respective micro-shutter. The openings and closures are controlled according to information respective of an image, thereby enabling to form the image. The light at the exit of the shutters are collected and directed to a projector, and the projector projects the image toward a retina of an eye of a user. The term "light" herein below refers to visible and invisible light (e.g., thermal radiation). The terms "slowly operated light source" and "fast modulating micro-shutter" are employed herein below, to stress the fact that the opening and closure rate of each micro-shutter is greater than the maximal operation rate of the respective light source (i.e., each micro-shutter can close and open at a rate which is more rapid than the maximal rate in which the respective light source is operative to switch on and off or change the intensity thereof). The light source is operated slowly compared to the modulation rate of the micro-shutter, either due to the construction of the light source, or because it is desired to operate the light source slowly. For example, it is physically impossible to switch an incandescent light source on and off at a rate comparable to the opening and closure rate of the micro-shutter. On the other hand although it may be physically possible to turn the light source on and off at such rates, it might not be advantageous to do so due to various reasons. For example, in case of a laser, although it is possible to energize and de-energize the laser at a rapid rate, it is not desirable to do so, because the energizing and the de-energizing cycle of the laser consumes more power than continuously keeping the laser energized. Other than that, continuously energizing and de-energizing the laser reduces the life time of the laser, and deteriorates the light intensity and spectrum. The term "micro-shutter" herein below, refers to a microelectromechanical system (MEMS) device which can be controlled to alternately block the transmission of light emitted by the slowly operated light source, or allow the transmission of light. Reference is now made to Figure 1 , which is a schematic illustration of a system for producing an image, generally referenced 100, constructed and operative in accordance with an embodiment of the disclosed technique. System 100 includes a plurality of slowly operated light sources RED-,,-,, GREEN-,,-,, BLUEi,-,, RED_1ι2, GREEN_1ι2, BLUEι,₂, RED_NιM, GREEN_N,M, and BLUE_N,M, a plurality of micro-shutters (i.e., fast modulating micro-shutters) SHUTTERR_,-,,-,,

SHUTTER_B,ι,ι, SHUTTER_R,i,_2> SHUTTER_G,_{I I2}, SHUTTER_B,i,₂, SHUTTERR,N,_M, SHUTTER_G,N_, , and SHUTTER_B,_N,M, an image source 102, a controller 104, collection optics 106 and a projector 108. Slowly operated light sources REDι_,ι, GREEN_{1 1 ;} BLUEi,-,, RED-,,₂, GREEN_1ι2, BLUE_{1 ι2}, RED_N,_M, GREEN_N,_M, and BLUE_N,_M are arranged in a two-dimensional array (i.e., a slowly operated light source array). Slowly operated light sources RED-,_,1, GREEN-,,₁, and BLUEι,ι are associated with a pixel 110 of an image (not shown). Slowly operated light sources RED-,_,2, GREEN_1ι2, and BLUE_1>2 are associated with a pixel 112 of the image. Slowly operated light sources RED_N,_M, GREEN_N, , and BLUE_N, are associated with a pixel 114 of the image. SHUTTER_R,_!,_!, SHUTTERQ,-,,-,. and SHUTTER_B,ι,ι are associated with a shutting module 116. SHUTTER_R,I,₂, SHUTTER_G,_I,₂, and SHUTTER_B,ι,₂ are associated with a shutting module 118. SHUTTER_R,_N,_M, SHUTTER_G,_N,M, and SHUTTER_{B,N M} are associated with a shutting module 120. SHUTTERR.₁,1 , SHUTTERG.1_,!, and SHUTTER_B,ι,ι are located in front of slowly operated light sources REDι_,ι, GREENι,ι, and BLUEι_,ι, respectively. SHUTTER_R,_1ι2, SHUTTER_G,1ι2, and SHUTTER_B,ι,₂ are located in front of slowly operated light sources RED_1ι2, GREEN _ι2, and BLUE_{1 2}, respectively. SHUTTER_R,N, , SHUTTER_G,N,M, and SHUTTER_B,N|M are located in front of slowly operated light sources REDN_,M, GREEN_N,_M, and BLUE_{N M}, respectively. SHUTTER_R,ι,ι, SHUTTERG.1,₁, SHUTTER_B,ι,ι, SHUTTER_R,_1|2,

SHUTTERG.1,₂, SHUTTERB,I,2, SHUTTER_R|N,_M, SHUTTER_G,_N,M, and SHUTTER_B,N_, , can be arranged in a matrix (i.e., a micro-shutter matrix), similar to two-dimensional array of slowly operated light sources RED-,_,1, GREEN-,,-,, BLUEι,ι, REDι,₂, GREENι,₂, BLUEι,₂, RED_N,_M, GREEN_N,_M, and BLUE_N|M for example, on an integrated circuit - IC (i.e., MEMS). Micro-shutter matrix and the two-dimensional array of slowly operated light sources REDi_,-,, GREENi.i, BLUEi,-,, REDι,₂, GREEN_1ι2, BLUE_1ι2, RED_N,_M, GREEN_N, , and BLUE_N,_M can be located on the same IC. Image source 102 can be a charge-coupled device (CCD) camera, near infrared image intensifier tube (i.e., either a still image camera or a video camera), mid-to-far infrared image camera (i.e., thermal forward-looking infrared - thermal FLIR camera), computer, visible light video camera, and the like. Collection optics 106 is an optical assembly which includes a plurality of optical elements, such as lens, reflector, beam splitter, prism, analyzer, and the like. Collection optics 106 collects light beams at an inlet thereof (not shown), and produces an image at an outlet thereof (not shown), according to input light beams. Projector 108 can be in form of a reflective surface array incorporated with a MEMS (i.e., an array of reflective surfaces arranged on an IC), reflective surface, liquid-crystal-on-silicon (LCOS), and the like. Alternatively, projector 108 is a transmissive device, such as liquid crystal display (LCD), and the like. Controller 104 is coupled with image source 102 and with SHUTTERR,^, SHUTTERQ,!,! , SHUTTERB ,! , SHUTTER_RI1,₂, SHUTTER_G,ι,2, SHUTTER_B,_{1 >2>} SHUTTER_R,_N,_M, SHUTTERQ,_N,_M) and SHUTTER_B,N,M- Collection optics 106 is located between SHUTTERR,^ , SHUTTERQ,!,! , SHUTTER_B,I,I , SHUTTER_R,_{1 I2}, SHUTTER_G,I_I2, SHUTTER_B,!,2, SHUTTERR,_N,_M, SHUTTER_G,N,M, and SHUTTER_B,N,M, on one side, and projector 108 on the other. Projector 108 is located in front of an eye 122 of a user (not shown). Slowly operated light sources RED^, RED_{1 ι2}, and RED_N, , emit light substantially in the red region of the visible spectrum. Slowly operated light sources GREEN_{! !}, GREEN_!,_!, and GREEN_N,_M, emit light substantially in the green region of the visible spectrum. Slowly operated light sources BLUE _,!, BLUE_!,2j and BLUE_N,_M, emit light substantially in the blue region of the visible spectrum. In the example set forth in Figure 1 , each group of slowly operated light sources associated with the respective pixel, emits light according to the red-green-blue (i.e., RGB) palette. For each of these groups, the micro-shutters associated therewith, allow to produce almost any color by combining different relative portions of red, green and blue. The number of slowly operated light sources associated with each pixel, is equal to the number of colors in the specific color palette employed for the disclosed technique. Each of SHUTTERR,!,! , SHUTTERQ,!,! , SHUTTER_B,ι,ι, SHUTTER_R,ι,2, SHUTTERQ,I,2, SHUTTER_B,ι,₂, SHUTTER_R,_N,_M, SHUTTER_G,N,M, and SHUTTER_B,N, , can be either in a closed position (or closed state), thus blocking light from the corresponding slowly operated light source, or in an open position (or open state), thereby allowing light emitted by the respective slowly operated light source, to exit. Controller 104 controls the opening and closure of each of SHUTTER_Rιι,_!, SHUTTERQ,!,! , SHUTTER_B,ι_,ι, SHUTTER_R,i,₂, SHUTTER_G,I,₂,

SHUTTER_Bl1,2, SHUTTER_RΛM, SHUTTERQ,_N>M, and SHUTTER_B,N,M, independently, according to a signal received from image source 102. The shutter modulation rate of each micro-shutter is considerably greater than the maximal operation rate of the respective slowly operated light source. The shutter modulation rate can be for example, 100 kHz or greater. Thus, system 100 can be employed with an array of relatively simple and inexpensive light sources which are energized continuously and need not be turned on and off nor the intensity thereof changed, in order to produce a fast modulated image sequence. Alternatively, the disclosed technique enables producing motion pictures using radiation sources which have an extremely slow modulation rate, such as thermal radiation (e.g., having a maximal modulation rate of 0.5 Hz). A light beam 124 represents a collection of light beams (not shown) which exit SHUTTER_R,^, SHUTTER_Gfι,ι, and SHUTTER_B|1,i and enter collection optics 106. A light beam 126 represents a collection of light beams (not shown) which exit SHUTTER_R,ι_ι2, SHUTTER_G,_!,₂, and SHUTTER_B,_!,₂ and enter collection optics 106. A light beam 128 represents a collection of light beams (not shown) which exit SHUTTERR,_N,M, SHUTTERQ_{, N,M}, and SHUTTER_B, N_,M and enter collection optics 106. Collection optics 106 collects light beams 124, 126 and 128, and produces an image (substantially identical with the image defined by image source 102), represented by a light beam 130. Projector 108 projects light beam 130 as a light beam 132, toward a cornea 134 of eye 122 and cornea 134 directs light beam 132 as a light beam 136 on a retina 138 of eye 122. In this manner, eye 122 observes the image defined by image source 102. Controller 104 controls the relative opening periods of each micro-shutter in a group of micro-shutters associated with a certain pixel, in order to produce a certain color at that pixel. For example, if SHUTTERR_{,! ,2} corresponding to slowly operated light source RED_1ι2 and SHUTTER_B,!,₂ corresponding to slowly operated light source BLUE_1ι2, are both open for 5msec, and SHUTTERQ,!_{, 2} corresponding to slowly operated light source GREEN_{1 2} is closed during that 5msec, then the light associated with pixel 112 in the image projected on retina 138, is substantially magenta in color. Controller 104 controls the opening period of a group of micro-shutters corresponding to a certain pixel, relative to the opening period of another group of micro-shutters corresponding to another pixel, in order to vary the brightness level of one pixel in the projected image, relative to the other pixel. For example, if SHUTTER_R,!,2 and SHUTTER_B,!,2 are open for 5 msec out of 10 msec frame time, SHUTTERR_,!,_! and SHUTTER_B>!,! are open for 10 msec (i.e., the full frame time), and SHUTTERQ,_{! , 1} and SHUTTER_G,!,2 are closed for 5 msec and 10 msec, respectively, then the average light output per frame associated with both pixel 112 and pixel 110 in the image projected on retina 138, is substantially magenta in color, however pixel 110 is twice as bright as pixel 112. It is noted that when images are intended to be observed by the human eye, short times (e.g., less than 20 msec) have to used, in synchrony with the image frame time period, to avoid flickers. Each of slowly operated light sources RED_!,!, GREEN_!,!, BLUE_!,!, RED_1ι2> GREENi_,2, BLUEι_,2, RED_N,_M, GREEN_N,M, and BLUE_N,_M is a light source whose modulation rate (i.e., on-off frequency) is substantially slow, and not sufficiently rapid to produce a meaningful image for the user all by itself (i.e., without incorporating any shutting mechanism). Each of slowly operated light sources RED^, GREEN_!,!, BLUE!,!, REDι,₂, GREEN_1ι2, BLUE_1ι2, RED_N,_M, GREEN_N,_M, and BLUE_N,_M can be a laser, light emitting diode (LED), organic light emitting diode, fluorescent light element, incandescent light element, liquid crystal display, and the like. Alternatively, all the slowly operated light sources emit light in the same spectrum (e.g., visible light), and a color filter is placed in front of each slowly operated light source, in order to produce a light beam in a certain spectrum (e.g., red, green, or blue color filter), thereby producing a color image. Further alternatively, all the slowly operated light sources emit light in the same spectrum, wherein no filter is incorporated there with, thereby producing a binary image. It is noted that each of the slowly operated light sources can emit invisible light, such as far infrared, mid infrared, near infrared, thermal radiation, ultraviolet (UV) radiation, and the like. Near infrared is defined for a range of 0.7-1 microns. The thermal regime is defined for a range of 3-5 microns (i.e., mid infrared) and 8-12 microns (i.e., far infrared). Further alternatively, the slowly operated light sources can emit visible light at substantially the same range of wavelengths, in which case the system produces a bitmap (i.e., black and white image). It is noted that the projector can project the image obtained from the collection optics, on an object instead of on the retina of an eye. Such an arrangement can be employed for example, for a strobe light device, optical test equipment, dimensional measurement apparatus, and the like. It is further noted that each slowly operated light source can be associated with only one pixel of the image, while as before, a respective micro-shutter is associated with each slowly operated light source. In this case, each region of the image is represented by a group of pixels, where each pixel is illuminated in a different color. It is noted that collection optics 106 and projector 108 can be eliminated from system 100, in which case shutting modules 116, 118 and 120 are part of a micro-shutter matrix which forms a display visible to the user. In case the slowly operated light sources emit invisible radiation, a detector (e.g., thermal camera, infrared camera, UV camera) can be employed to detect the invisible modulated radiation pattern and to produce a visible image to the user, such as a temperature gradient image, infrared image, and the like. Reference is now made to Figures 2A and 2B. Figure 2A is a schematic illustration of a system for producing an image, generally referenced 140, constructed and operative in accordance with another embodiment of the disclosed technique. Figure 2B is a schematic illustration of an arrangement of one of the slowly operated light sources of the system of Figure 2A, and a respective micro-shutter array of the system. With reference to Figure 2A, system 140 includes an image source 142, a controller 144, a plurality of slowly operated light sources 146, 148 and 150, a shutter module 152, collection optics 154 and a projector 156. Shutter module 152 includes shutter arrays 158, 160 and 162. With reference to Figure 2B, each of the shutter arrays (e.g., shutter array 158) includes a plurality of micro-shutters 164_!, 164₂, 164₃, and 164_N. Each of slowly operated light sources (e.g., slowly operated light source 146) is an elongated light source, and micro-shutters 164_{1 ;} 164₂, 164₃₎ and 164_N are located in front of slowly operated light source 146. Each of micro-shutters 164_!, 164₂, 164₃, and 164_N is associated with a different pixel of an image (not shown). Controller 144 is coupled with image source 142 and with shutter module 152. Slowly operated light sources 146, 148 and 150 are associated with shutter arrays 158, 160 and 162, respectively. Controller 144 controls the opening and closure of the micro-shutters of each of shutter arrays 158, 160 and 162 (e.g., micro-shutters 164_1; 164 , 164₃, and 164_N of shutter array 158) according to a signal received from image source 142, for shutter arrays 158, 160 and 162 to produce a light beam 166. Collection optics 154 collects light beam 166 to produce an image substantially similar to the one defined by image source 142. Projector 156 projects the image collected by collection optics 154 onto a retina (not shown) of an eye (not shown) of a user (not shown). Reference is now made to Figures 3A and 3B. Figure 3A is a schematic illustration of a micro-shutter in a closed position, generally referenced 170, constructed and operative in accordance with a further embodiment of the disclosed technique. Figure 3B is a schematic illustration of the micro-shutter of Figure 3A, in an open position. Micro-shutter 170 is a MEMS element which is etched on a substrate (not shown) of an IC in an IC technology. Micro-shutter 170 includes a flipping panel 172, a pair of bearings 174 and 176, a pair of hinges (not shown), a closing electrode (not shown) and an opening electrode (not shown). Each hinge is coupled with flipping panel 172 and allowed to freely articulate within the respective bearing 174 or 176. Each of the closing electrode and the opening electrode, is located under flipping panel 172, at opposite sides of the hinges. A slowly operated light source 178 is located below the substrate. The closing electrode and the opening electrode are coupled with a controller (not shown). With reference to Figure 3A, the closing electrode is activated according to a signal received from the controller, thereby keeping flipping panel 172 in a closed position. A light beam 180 emitted by slowly operated light source 178 is blocked. With reference to Figure 3B, the controller sends a signal to the opening electrode to flip flipping panel 172 to an open position, thereby allowing light beam 180 to exit the substrate. The operation of micro-shutter 170 is described in detail in International Publication No. WO 03/048836 A2, which is herewith incorporated by reference. The alternate opening and closures of flipping panel 172 at a shutter modulation rate greater than the maximum self modulation rate of slowly operated light source 178, produces a high frequency modulated light. Reference is now made to Figure 4, which is a schematic illustration of a spectacle incorporated with the system of Figure 1 , generally referenced 190, constructed and operative in accordance with another embodiment of the disclosed technique. Spectacle 190 includes a frame 192, a pair of ear supports 194 and 196, and a pair of compartments 198 and 200. Frame 192 includes a pair of viewing lenses 202 and 204 and a pair of projectors 206 and 208. Each of the viewing lenses 202 and 204 is substantially transparent. Each of projectors 206 and 208 is similar to projector 108 (Figure 1) as described herein above, and is incorporated with the respective viewing lenses 202 and 204. Each of projectors 206 and 208 is made of a semi-transparent material. Ear supports 194 and 196 are coupled with frame 192. Compartments 198 and 200 are coupled with ear supports 194 and 196, respectively. Each of compartments 198 and 200 includes a slowly operated light source array (not shown) as described herein above in connection with Figure 1 , and a corresponding shutter matrix (not shown) as described herein above in connection with Figure 1. Each of compartments 198 and 200 further includes a controller (not shown), an image source (not shown), and a collection optics (not shown), similar to controller 104, image source 102 and collection optics 106, as described herein above in connection with Figure 1. Each of compartments 198 and 200 can further include a power supply. Each collection optics collects the light beams (not shown) which exit the respective shutter matrix, and produces another light beam (not shown) respective of an image (not shown) defined by the respective image source. Each of the projectors 206 and 208 projects a corresponding image respective of the light beam received from the corresponding collection optics, toward a retina (not shown) of a respective eye (not shown) of a user (not shown). It is noted that each of projectors 206 and 208 can be partially reflective (i.e., transmit part of incoming light and reflect part of incoming light). Thus, the user can view each of the images projected by projectors 206 and 208 against a background scene (not shown). Alternatively, each of viewing lenses 202 and 204 can be made of a partially reflective material, in which case projectors 206 and 208 can be eliminated. It is further noted that the arrangement of Figure 4 can be incorporated with apparatus other than spectacles, such as head-mounted display, helmet visor, welding visor, periscope, telescope, microscope, binoculars, and the like. Reference is now made to Figure 5, which is a schematic illustration of a method for operating the system of Figure 1 , operative in accordance with a further embodiment of the disclosed technique. In procedure 230, a separate fast modulating micro-shutter located in front of a respective slowly operated light source is assigned to each one of a plurality of slowly operated light sources. With reference to Figure 1 , SHUTTER_R,ι_,ι, SHUTTER_Gι1,ι, SHUTTER^, SHUTTER_R,1|2, SHUTTER_G,ι,₂, SHUTTER_B,_I,₂, SHUTTER_R,_N,_M, SHUTTERQ,_N,_M, and SHUTTER_B,N,M_> is associated with slowly operated light sources RED_1;!, GREEN_!,!, BLUEi_,!, REDι_,2, GREENι_,2, BLUEι,₂, RED_N,_M, GREEN_N,_M, and BLUE_{N M}, respectively. In procedure 232, information respective of an image is received from an image source. With reference to Figure 1 , controller 104 receives a signal respective of an image from image source 102. In procedure 234, the light of each slowly operated light source is modulated, by controlling the opening and closure of the fast modulating micro-shutter associated therewith, according to the received information, at a shutter modulation rate of the fast modulating micro-shutter, greater than a maximal operation rate of the respective slowly operated light source, thereby producing a fast modulated image sequence. With reference to Figure 1 , controller 104 controls the opening and closure of SHUTTERR,_{! ,!}, SHUTTERQ_,!_,!, SHUTTER^, SHUTTER_R,ι,₂, SHUTTER_G,ι,₂, SHUTTER_B,ι_l2j SHUTTER_R,_N,_M, SHUTTERQ,_NIM, and SHUTTER_B,NιM, according to a signal received from image source 102. In this manner,

SHUTTER_R,ι,₂, SHUTTER_G,ι,₂, SHUTTER_B.₁,₂, SHUTTER_R,_N,_M, SHUTTER_G,_N,_M) and SHUTTERB.N.M modulate the light emitted by slowly operated light sources REDι_,ι, GREENI_,!, BLUEI_,! , RED_1|2, GREENI,₂, BLUE_{I ,2}, RED_N,_MJ GREEN_N| , and BLUE_N,M, respectively, thereby producing the image which is defined by image source 102. It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.

Claims

1. Device for producing high frequency modulated light, the device comprising: at least one slowly operated light source being characterized by a maximal operation rate; and at least one micro-shutter being located in an optical path to said at least one slowly operated light source, said at least one micro-shutter being operative to modulate light passing there through, by alternately moving to an open state and a closed state, at a shutter modulation rate which is greater than said maximal operation rate, thereby producing said high frequency modulated light.

2. The device according to claim 1 , wherein said at least one slowly operated light source comprises a plurality of slowly operated light sources arranged in a slowly operated light source array, wherein said at least one micro-shutter comprises a plurality of micro-shutters arranged in a micro-shutter matrix, each separate micro-shutter of said micro-shutter matrix being located in said optical path to a respective one of said slowly operated light sources, wherein said device further comprises a controller coupled with said micro-shutter matrix, said controller controlling the opening and closure of each of said separate micro-shutter, according to information respective of an image received from an image source, to rapidly modulate the light emitted by said respective slowly operated light source, thereby producing a fast modulated image sequence.

3. The device according to claim 2, further comprising a collection optics located in front of said micro-shutter matrix, said collection optics collecting the lights modulated by said micro-shutter matrix, and said collection optics projecting said fast modulated image sequence on a retina of an eye of a user.

4. The device according to claim 3, further comprising a projector located between said collection optics and said eye, said projector receiving said fast modulated image sequence from said collection optics, and said projector projecting said fast modulated image sequence on said retina.

5. The device according to claim 4, wherein said projector is a reflective device.

6. The device according to claim 5, wherein said reflective device is a liquid-crystal-on-silicon device.

7. The device according to claim 5, wherein said reflective device is selected from the list consisting of: reflective surface array incorporated with a microelectromechanical system; and reflective surface.

8. The device according to claim 4, wherein said projector is a transmissive device.

9. The device according to claim 8, wherein said transmissive device is a liquid crystal display.

10. The device according to claim 2, further comprising said image source, said image source being coupled with said controller.

1 1. The device according to claim 2, wherein said image source is selected from the list consisting of: charge-coupled device camera; near infrared image intensifier tube; mid-to-far infrared image camera; computer; and visible light video camera.

12. The device according to claim 2, wherein said respective slowly operated light sources is associated with said separate micro-shutter.

13. The device according to claim 2, wherein each of said slowly operated light sources is associated with a group of micro-shutters of said micro-shutter matrix.

14. The device according to claim 2, wherein said fast modulated image sequence is selected from the list consisting of: color; and binary.

15. The device according to claim 2, wherein each of said slowly operated light sources is associated with a different pixel of said fast modulated image sequence.

16. The device according to claim 2, wherein said controller varies the brightness of said fast modulated image sequence, by controlling an opening period of each of said micro-shutters compared with a closing period of said micro-shutters.

17. The device according to claim 2, further comprising an optical assembly for viewing an informative image against a scene image of a scene.

18. The device according to claim 17, wherein said optical assembly is selected from the list consisting of: head-mounted display; spectacles; helmet visor; welding visor; periscope; telescope; microscope; and binoculars;

19. The device according to claim 1 , wherein said at least one slowly operated light source radiates in the range selected from the list consisting of: substantially visible red color light; substantially visible green color light; substantially visible blue color light; visible light; near infrared; mid infrared; far infrared; thermal radiation; and ultraviolet radiation.

20. The device according to claim 1 , wherein said at least one slowly operated light source is selected from the list consisting of: laser; light emitting diode; organic light emitting diode; fluorescent light element; incandescent light element; and liquid crystal display.

21. The device according to claim 1 , wherein said shutter modulation rate is at least 100 kHz.

5 22. Device for producing a selected color of each of a plurality of multi-color pixels by using a plurality of slowly operated light sources associated with a respective one of said multi-color pixels, each of said slowly operated light sources emitting light in a respective rangeo of wavelengths of a color palette, each of said slowly operated light sources being characterized by a maximal operation rate, said device comprising: a plurality of micro-shutters associated with said respective multi-color pixel, each of said micro-shutters being located in an5 optical path to a respective one of said slowly operated light sources, each of said micro-shutters being operative to modulate light passing there through, by alternately moving to a respective open state and a respective closed state, at a shutter modulation rate which is greater than said maximal operation rate, an opening period of saido respective open state relative to a closing period of said respective closed state being selected to produce said selected color.

23. The device according to claim 22, further comprising a controller coupled with said micro-shutters, said controller controlling said5 opening period and said closing period.

24. The device according to claim 23, wherein said multi-color pixels are arranged in a pixel array, wherein said multi-color pixels are associated with a fasto modulated image sequence, and wherein said controller varies the brightness of said fast modulated image sequence, by controlling opening periods of a group of said micro-shutters associated with a multi-color pixel of said pixel array, relative to other opening periods of another group of said micro-shutters associated with another multi-color pixel of said pixel array.

25. The device according to claim 23, further comprising an image source coupled with said controller, wherein said controller operates according to information respective of an image, received from said image source.

26. The device according to claim 22, wherein said multi-color pixels are arranged in a pixel array, the device further comprising a collection optics located in front of said pixel array, said collection optics collecting the lights modulated by said micro-shutters, wherein said multi-color pixels are associated with a fast modulated image sequence, and wherein said collection optics projects said fast modulated image sequence on a retina of an eye of a user.

27. The device according to claim 26, further comprising a projector located between said collection optics and said eye, said projector receiving said fast modulated image sequence from said collection optics, and said projector projecting said fast modulated image sequence on said retina.

28. The device according to claim 22, wherein said color palette is red-green-blue.

29. Method for producing a fast modulated image sequence, the method comprising the procedure of modulating light of each of a plurality of slowly operated light sources, by controlling the opening and closure of each of a plurality of fast modulating micro-shutters associated with a respective one of said slowly operated light sources, according to information received respective of an image from an image source, at a shutter modulation rate of a respective one of said fast modulating micro-shutters, greater than a maximal operation rate of said respective slowly operated light source, thereby producing said fast modulated image sequence.

30. The method according to claim 29, further comprising a procedure of producing said fast modulated image sequence by collecting said modulated light.

31. The method according to claim 29, further comprising a procedure of reflecting said fast modulated image sequence toward a retina of an eye of a user.

32. The method according to claim 29, further comprising a procedure of transmitting said fast modulated image sequence to a retina of an eye of a user.

33. The method according to claim 29, further comprising a preliminary procedure of receiving said information from said image source.

34. The method according to claim 33, further comprising a preliminary procedure of associating each of said fast modulating micro-shutters with said respective slowly operated light source.

35. The method according to claim 33, further comprising a preliminary procedure of associating a group of said fast modulating micro-shutters with said respective slowly operated light source.

36. The method according to claim 29, further comprising a procedure of transmitting a light beam respective of a scene to a retina of an eye of a user.

37. The device according to any of the claims 1-28 substantially as described herein above or as illustrated in any of the drawings.

38. The method according to any of the claims 29-36 substantially as described herein above or as illustrated in any of the drawings.