US005969754A United States Patent [19] [11] Patent Number: Zeman [45] Date of Patent: [54] CONTRAST ENHANCING ILLUMINATOR 5,969,754 Oct. 19, 1999 In Focus Systems, LitePro 620, http://WWW. infocus.com/ products/projectors/lp620.html. [76] Inventor: Herbert D. Zeman, 1687 Peach Ave., Memphis, Tenn. 38112 Texas Instruments, Digital Micromirror Device, http://WW W.ti.com/dlp/docs/papers/state/state.htm. [21] Appl. No.: 08/762,599 [22] Filed: Dec. 9, 1996 Primary Examiner—Wendy Garber [51] Int. Cl.6 .......................... .. H04N 7/18; H04N 5/208; [52] US. Cl. .......................... .. 348/136; 348/61; 348/252; H04N 5/225 348/342; 348/370; 382/274 [58] Assistant Examiner—Ngoc-Yen Vu Attorney, Agent, or Firm—Luedeka, Neely & Graham, PC [57] ABSTRACT Field Of Search ................................... .. 348/207, 252, An apparatus Which enhances the visual contrast betWeen 348/625, 744, 62, 63, 79, 136, 584, 335, 340, 342, 343, 344, 164, 370; 382/266, 274; 359/634; H04N 7/18, 5/208, 5/222, bright and dark features of an object by projecting an image of the object onto the object. The features of the projected object image overlay the features of the object such that an observer of the enhanced object senses that the bright 5/225 [56] features are brighter and the dark features remain the same. References Cited A light source illuminates the object, a video imaging U.S. PATENT DOCUMENTS 3,017,515 3,849,910 means, such as a video camera, creates a video signal 1/1962 Welch ................................ .. 250/2081 11/1974 Greenly ........ . . . . .. 434/22 4,065,788 12/1977 Meier et a1. 4,502,075 2/1985 De Forest et a1. 348/625 348/79 4,591,918 5/1986 Hisano ........... .. 348/343 4,740,812 4/1988 Pryor 4,908,876 3/1990 DeForest et a1. 5,041,965 8/1991 .. ... ... ... ... .. Chen .................. .. . . . . .. 355/77 382/54 364/200 5,220,624 6/1993 Sakamoto et a1. 382/266 5,231,434 7/1993 Kennedy et a1. 353/122 5,239,373 8/1993 Tang et a1. 5,353,075 10/1994 Conner et a1. 5,359,550 10/1994 5,424,838 6/1995 Chen .......... .. .. 348/14 353/122 . 364/7081 Siu ........................................ .. 356/394 representative of the object image, and a video projector receives the video signal from the video camera and projects a visual image of the object. A?lter prevents video projector light from reaching the video imaging means, thereby elimi nating positive feedback. A preferred apparatus includes a beam separator Which causes the image projected from the video projector to illuminate the object from the same perspective that the video imaging means vieWs the object. Preferably, the light source is an infrared light source, the ?lter transmits infrared light but not visible light, and the beam separator re?ects visible light and transmits infrared light. Alternately, the invention visually enhances the edges of features of an object With an unsharp masking edge OTHER PUBLICATIONS Peli et al., Image Enhancement for the Visually Impaired, Investigative Ophthalmology & Wsual Science, vol. 32, No. 8, Jul. 1991, pp. 2337—2350. VIDEO PROJECTOR enhancement technique, thereby making the features of the object easier to distinguish. 23 Claims, 9 Drawing Sheets U.S. Patent Oct.19,1999 Sheet 1 of9 5,969,754 U.S. Patent Oct.19,1999 Sheet 2 of9 5,969,754 LJ‘_U PROJECT U.S. Patent Oct.19,1999 Sheet 3 of9 5,969,754 m N. IE1 ln-'i] E03 5 8 U.S. Patent Oct.19,1999 Sheet 4 0f 9 5,969,754 U.S. Patent Oct.19,1999 Sheet 5 of9 5,969,754 U.S. Patent Oct.19,1999 Sheet 6 of9 5,969,754 U.S. Patent Oct.19,1999 Sheet 8 of9 5,969,754 <m m F103 mo j m @ZEQOMW w 02%W OhmNOMS;EH53_\/ D9).9 7 OM53 <Dmo2<w “ILEm015 U.S. Patent Oct. 19, 1999 Sheet 9 0f 9 5,969,754 Fi_.5B 5,969,754 1 2 CONTRAST ENHANCING ILLUMINATOR transmits a portion of the light that reaches it. The beam separator is positioned betWeen the video imaging means and the object, and betWeen the video projector and the TECHNICAL FIELD object, such that the visual image projected by the video projector illuminates the object from the same perspective that the video imaging means vieWs the object, thus causing the features of the projected visual image to overlay the corresponding features of the object. In the preferred embodiment of the invention, the light The present invention relates to a method and apparatus for enhancing the visibility of an object to observers of the object. More particularly, it relates to a method and appa ratus for increasing the contrast betWeen bright and dark areas of an object by projecting an image of the object onto the object. 10 source is an infrared light source, such as an array of infrared light emitting diodes, or a White light source housed in a BACKGROUND container that only alloWs infrared light to escape. The ?lter As a result of the normal aging process, and as a result of is of a type, and the beam separator is of a type Which re?ects diseases such as AIDS, diabetes, and multiple sclerosis, a patient experiences degeneration in the central portion of the 15 retina of the eye, the macula retinae. This condition causes the patient dif?culty in distinguishing anything other than visible light and transmits infrared light. This embodiment prevents visible light from the video projector from reaching the video imaging means While alloWing infrared light, re?ected from the object, to reach the video imaging means. The video imaging means of the preferred embodiment is a charge coupled device (CCD) video camera, and the video very high contrast objects, such as large black letters on a White background. A normal scene of daily life, such as various foods on a plate, becomes almost impossible to projector is a liquid crystal display (LCD) video projector. In interpret due to the patient’s inability to distinguish the light an alternate embodiment a digital mirror display (DMD) and dark areas of the scene. may be used as the video projector. In an alternative embodiment of the invention, the vis The contrast of a scene could be enhanced for the patient by means of a pair of glasses equipped With a video display ibility of the object is further enhanced by increasing the fed With a video signal from a video camera mounted on the 25 de?nition of the edges of the object using an unsharp patient’s head. The contrast of the video display could be adjusted to enhance the contrast of the scene vieWed by the masking edge enhancement technique. The video imaging means of this embodiment is comprised of a ?rst video video camera. Unfortunately, such an apparatus Would camera Which measures source light re?ected from the require the patient to carry added Weight on his head and get object in the form of a focused image and generates a video used to a completely neW Way of vieWing the World. Hence, it is desirable to enhance the contrast of a scene While alloWing the patient to vieW the scene With his oWn output signal representative of the focused image, and a second video camera Which measures source light re?ected eyes. Such contrast enhancement may be accomplished by selective illumination of the scene. Areas of the scene With high re?ectivity are illuminated more strongly, While areas of loWer re?ectivity are illuminated less strongly. In this manner, bright areas become brighter While dim areas 35 from the object in the form of a defocused image and generates a video output signal representative of the defo cused image. A difference ampli?er produces at its output a video signal representing the difference betWeen the video signals from the tWo video cameras. In a second alternative embodiment of the invention, the video signals from the tWo video cameras are converted into remain dim, resulting in contrast enhancement. To achieve color enhancement, each of the three primary colors may be contrast enhanced independently. It is also desirable to enhance the edges of features in the prised of a ?rst logarithmic ampli?er Which converts the scene to distinguish the transition from one feature of a video signal at the output of the ?rst video camera into a ?rst logarithmic video signals prior to subtracting them. The video imaging means of this embodiment is further com logarithmic video signal, a second logarithmic ampli?er scene to the neXt. SUMMARY 45 Which converts the video signal at the output of the second video camera into a second logarithmic video signal, and a difference ampli?er Which produces at its output a logarith mic video signal representing the difference betWeen the ?rst and second logarithmic video signals at its input. An inverse logarithmic ampli?er produces at its output the inverse logarithm of the logarithmic difference video signal at its The present invention is directed to an illumination appa ratus that satis?es the need for a means of enhancing the contrast of an object While alloWing an observer to vieW the object directly With his oWn eyes. The illumination appara tus alters the visual contrast betWeen bright and dark areas of an object by projecting a visual image of the object onto the object. The apparatus consists of a light source Which input. image and creates a video output signal representative of the image, and a video projector Which receives the video signal from the video imaging means and projects a visual image Which is representative of the image measured by the video digital frame capture means Which converts the analog video signals at the output of the ?rst and second video cameras into a digital format Which may be processed by a digital processor. A digital processor performs a digital subtraction of the tWo digital video signals to form a digital difference signal, and a digital-to-analog frame output means converts the digital difference signal into an analog video output In a third alternative embodiment of the invention, the illuminates the object, a video imaging means Which mea subtraction of the tWo video signals is performed in a digital sures source light re?ected from the object in the form of an 55 format. This embodiment further comprises an analog-to imaging means. The apparatus also includes a ?lter Which prevents video projector light from reaching the video imaging means While alloWing source light, re?ected from the object, to reach the video imaging means. In this manner, the ?lter eliminates positive feedback Which Would degrade the desired visual effect. An alternative embodiment of the invention further con sists of a beam separator Which re?ects a portion and signal. 65 The method of the present invention alters the visual contrast betWeen bright and dark areas of an object by projecting a visual image of the object onto the object, Where the visual contrast is sensed by a direct observer of the 5,969,754 3 4 object. The method includes the steps of illuminating the object by means of a light source, measuring the light object 4 as vieWed by an observer 6. A light source 8 re?ected from the object in the form of an image and the object in the direction of the observer 6 and in the direction of the apparatus. Because of irregularities in the surface of the object 4, and differences in the re?ective illuminates the object resulting in the re?ection of light from creating a video output signal representative of the image, and projecting a visual image, Which is representative of the video signal at the output of the light measuring means, onto the object. The visual image is projected in such a manner that the visual image illuminates the object from the same perspective that the light measuring means vieWs the object. In this manner, the features of the projected visual image overlay the corresponding features of the object. properties over different areas of the object 4, some areas of the object 4 re?ect light more brightly than others. The contrast in light intensity betWeen bright and dark areas can 10 The method of the invention also includes the step of ?ltering the light Which enters the light measuring means such that light from the projecting means is not measured by the light measuring means, While light from the illuminating means, Which is re?ected from the object, is measured by the light measuring means. This step eliminates positive feed back Which Would degrade the desired visual effect. be intensi?ed by projecting an image of the object 4 back onto the object 4, such that the features of the projected image overlay the corresponding features of the object 4. In this manner, the bright areas become brighter While the dark areas remain dark, thus enhancing contrast. Conversely, the contrast in intensity betWeen the bright 15 steps of measuring the light re?ected from the object in the and dark areas of the object 4, as sensed by the observer 6, may be decreased by projecting an inverse image of the object 4 back onto the object 4. The bright and dark areas are inverted in the inverse image such that When the inverse image is projected onto the object 4, the dark areas of the object 4 are made brighter and the bright areas of the object form of a focused image and creating a ?rst video output 4 remain the same. In an alternative method of the invention incorporating edge enhancement, the light measuring step includes the signal representative of the focused image, measuring the With continued reference to FIG. 1, light from the light light re?ected from the object in the form of a defocused image and creating a second video output signal represen tative of the defocused image, and subtracting the ?rst video source 8 re?ects from the object 4, and passes into the video 25 signal from the second video signal to form a difference video output signal. BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiments of the invention Will noW be the video projector 12. The video projector 12 projects an image onto the object 4, the image corresponding to the video signal at the input of the projector 12. The image Which is projected by the video projector 12 onto the object described in further detail. Other features, aspects, and advantages of the present invention Will become better understood With regard to the folloWing description, 4 is basically the same image as that received by the video camera 10, or it is the inverse of the image as discussed appended claims, and accompanying draWings Where: FIG. 1 is a functional block diagram of an embodiment of the invention; camera 10. The video camera lens 30 forms the re?ected light into a visual image Which the video camera 10 converts into an electrical video signal. This electrical signal is fed from the video output of the video camera 10 to the input of 35 FIG. 2a is a functional block diagram of an alternative previously. With continued reference to FIG. 1, a distance measuring device 42 measures the distance betWeen the illumination embodiment of the invention Which incorporates high-speed apparatus and the object 4, and produces an electrical signal shutters shoWn during a ?rst half-cycle of the shutter Which is representative of the measured distance. This sequence; FIG. 2b is a functional block diagram of an alternative electrical signal is fed to the video camera 10 Which makes the necessary adjustments, based on the measured distance embodiment of the invention Which incorporates high-speed to the object, to bring the image of the object 4 into focus. Similarly, the electrical signal from the distance measuring shutters shoWn during a second half-cycle of the shutter device is fed to the video projector 12 Which makes the sequence; FIG. 2c is a functional block diagram of a preferred 45 necessary adjustments, based on the measured distance to the object, to bring the projected image of the object 4 into embodiment of the invention incorporating a cold mirror focus. The distance measuring device 42 determines the distance betWeen the illumination apparatus and the object 4 by measuring the time required for a pulse, such as an ultrasonic pulse, emitted from the distance measuring device 42 to travel to and re?ect from the object 4, and travel back to the distance measuring device 42. beam separator; FIG. 2a' is a functional block diagram of a preferred embodiment of the invention incorporating a hot mirror beam separator; FIG. 3 is a functional block diagram of an alternative embodiment of the invention incorporating contrast In an alternative embodiment of the invention as shoWn in enhancement and analog edge enhancement; FIG. 4 is a functional block diagram of an alternative embodiment of the invention incorporating contrast 55 the video camera 10. As above, the video camera lens 30 enhancement and digital edge enhancement; forms the re?ected light into a visual image Which the video FIG. 5a is a functional block diagram of an alternative camera 10 converts into an electrical video signal. This embodiment of the invention incorporating analog edge enhancement only; and electrical signal is fed from the video output of the video camera 10 to the input of the video projector 12. In this FIG. 5b is a functional block diagram of an alternative embodiment of the invention incorporating digital edge enhancement only. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS ShoWn in FIG. 1 is an illumination apparatus 2 Which alters the contrast betWeen bright and dark features of an FIG. 2a, light from the light source 8 re?ects from the object 4 and passes through the beam separator 16 prior to entering 65 embodiment, the video projector 12 projects an image onto the beam separator 16, the image corresponding to the video signal at the input of the projector 12. As shoWn in FIG. 2b, the beam separator 16 re?ects the projected image back onto the object 4. The beam separator 16 is precisely positioned relative to the video camera 10 and the video projector 12 so that the 5,969,754 5 6 image re?ected from the beam separator 16 and onto the object 4 follows a path to the object 4 Which coincides With visible light from the video projector 12 that passes through the beam separator 16. The boX also prevents any infrared light from reaching the video camera 10 directly from the light source 8. As shoWn in FIG. 2c, the light-absorbing boX 18 has three apertures, one Which passes light from the video projector 12 to the beam separator 16, one Which passes light the path followed by the light re?ected from the object 4 to the video camera 10. In other Words, the video camera vieWs the object, and the object, from the same perspective. In this manner, the bright and dark features of the projected image precisely overlay the corresponding bright and dark features from the beam separator 16 to the video camera 10, and one of the object image as detected by the video camera 10. The light from the video projector Which re?ects from the Which passes light betWeen the object 4 and the beam separator 16. The beam separator 16 of the embodiment shoWn in FIG. 2a' is an Edmund Scienti?c Company Model 43,453 hot mirror Which transmits visible light but re?ects infrared light. In this embodiment, the infrared light re?ected from the object is re?ected from the hot mirror beam separator 16 object 4 must be prevented from being detected by the video 10 camera 10. OtherWise, this re?ected light Would pass into the video camera 10, transfer to the video projector 12 in the form of a video signal, project back onto the object 4, and be re?ected back to the video camera 10, thus forming a positive feedback loop. If not prevented, such positive 15 feedback Would lead to the creation of an unstable or binary and into the video camera 10. The video camera 10 of the embodiments depicted in image. FIGS. 2c and 2a' is a Cohu Model 631520010000 mono One method of making the video camera 10 insensitive to chrome charge coupled device (CCD)) video camera. The light from the video projector 12, and thus eliminating positive feedback, is to place high-speed shutters in front of video camera lens 30 is a Tokina AT-X AF 17 mm f3.5 20 the video camera 10 and the video projector 12. During a ?rst half-cycle of shutter operation as shoWn in FIG. 2a, the ?rst shutter 48a in front of the video camera 10 is open, and the second shutter 48b in front of the video projector 12 is closed, thus blocking the video projector light While the 25 Nikon-mount lens. The ?lter 14, mounted on the front of the video camera lens, is an Edmund Scienti?c Company Model 32,766 infrared transmitting ?lter With a 695-mm cutoff Wavelength Which only alloWs infrared light to enter the video camera 10. To provide the necessary angular adjustment, the video camera 10, lens 30, and ?lter 14 are video camera 10 measures only the source light re?ected mounted on an adjustment stage, such as a Bogen Model from the object 4. During a second half-cycle, as shoWn in 3275, Which provides for elevation, aZimuth, and roll angu lar positioning. The three-angle adjustment stage is mounted FIG. 2b, a ?rst shutter 48a in front of the video camera 10 is closed, and a second shutter 48b in front of the video on a tripod, such as a Bogen Model 3020. The video camera lens 30 of this embodiment corrects a projector 12 is open, thus alloWing the video projector light to illuminate the object 4, but precluding video projector light from reaching the video camera 10. Alternatively, a preferred embodiment of the invention prevents positive feedback by employing a ?lter 14 in front of the video camera lens 30 as shoWn in FIGS. 2c and 2d. distortion of the projected image introduced by the Epson Model ELP-3000 video projector 12. This model projector is designed to project an image on an overhead screen Whose 35 This ?lter 14 rejects light from the video projector 12 While passing light from the light source 8 Which is re?ected from the object 4. For the ?lter 14 to perform this function, the source light re?ected from the object 4 must in some Way differ from the light projected by the video projector 12. to correct for the “keystone” distortion effect Which occurs With oblique angles of projection. In keystone distortion, the magni?cation of the image varies With vertical position on 40 FIGS. 2c and 2d, the light source 8 is an infrared light 45 keystone distortion is corrected by vertically offsetting the (Edmund Scienti?c Company Model 52,580) Which consists eXample is a White light, such as a GE 45-Watt ?ood lamp, contained Within a housing that is light-tight eXcept for an aperture covered by an infrared-transmitting ?lter, such as an Edmund Scienti?c Company Model 60,033. The video projector 12 of this embodiment is an Epson Model ELP 50 55 and into the video camera 10. The beam separator 16 is mounted in a light-absorbing boX 18 Which absorbs any mount With a means for vertical position adjustment, such as the Nikon PB-6 BelloWs lens mount system With an addi enhances the edges of an object 4 using an unsharp masking technique. With this technique, a blurred version of the object image is produced and is subtracted from the original object image to produce an edge-enhanced image. The light source 8, video projector 12, ?lter 14, and light in the visible range. In an alternate embodiment a display Which incorporates a digital micromirror device (DMD), such as that produced by Texas Instruments, Inc., mirror Which transmits infrared light but re?ects visible light. In this embodiment, the infrared light re?ected from the object passes through the cold mirror beam separator 16 video camera lens 30 With respect to the optical aXis of the camera. This vertical offset is accomplished using a lens tional vertical ?ne motion control stage. A ?rst alternative embodiment of the invention visually 3000 liquid crystal display (LCD) projector Which emits may be used as the video projector. The beam separator 16 of the embodiment shoWn in FIG. 2c is an Edmund Scienti?c Company Model 42,414 cold height, such that the projection aXis of the video projector 12 forms an angle of nearly 90 degrees With the surface of the object 4. In this situation, the offset lens of the video projector 12 Would cause the image projected onto the object 4 to have an “inverted keystone” distortion. The inverted eXample of such a light source is an Electrophysics Corpo ration Model IRL600 Infrared Microbeam Safelight of an array of infrared light emitting diodes (LEDs). Another a screen, With a larger magni?cation at the top of the screen than at the bottom. HoWever, in typical operation of the invention, the projector 12 and the object 4 are at the same The preferred method of achieving this difference is to separate the tWo light signals in Wavelength. As shoWn in source, emitting light With a Wavelength longer than 695 nanometers Which is longer than visible Wavelengths. One surface is at an oblique angle to the projection aXis. This model projector incorporates a lens Which is offset vertically 60 light-tight boX 18 of this alternative embodiment are iden tical to, or functionally equivalent With, the corresponding components of the previously described embodiment. HoWever, as shoWn in FIG. 3, this embodiment incorporates 65 tWo video cameras 10a and 10b, such as Cohu Model 631520010000 monochrome CCD video cameras, each vieWing the object 4 from the same perspective by means of a beam splitter 28, such as an OptoSigma 055-0165 infrared 5,969,754 7 8 beam splitter prism. The beam splitter 28 provides one half of the light re?ected from the object 4 to each of the video angle prism or mirror, provides a reversal of the object video output device 36, may be fed to the input of a video display device 50, such as a television monitor, or to the input of a video recording device 52, such as a video cassette recorder. With this embodiment, the observer 6 vieWs the image detected by the ?rst camera 10a to match the re?ected edge-enhanced image of the scene by vieWing either the live (and, therefore, reversed) object image detected by the or recorded image by means of the video display device 50. Prior to using the invention shoWn in FIG. 3 for contrast cameras 10a and 10b. Are?ecting surface 44, such as a right second camera 10b. One of the cameras is sharply focused While the other is defocused to provide a blurred version of the object image. A Zoom lens 46, such as a Vivitar 17—28 mm f 4.0—4.5 lens, alloWs adjustment of the siZe of the object image detected by the ?rst camera 10a so that the focused and defocused object images are the same siZe. The frame capture of the tWo cameras is synchroniZed by or edge enhancement, the image of the object 4 captured by the video camera 10 (or video cameras 10a and 10b) and 10 object 4. This is accomplished by adjusting the three angular adjustments on the geared tripod head, the vertical offset adjustment of the video camera lens 30, and the Zoom control of the video projector lens. means of a locking circuit, such as the GENLOCK circuit Which is integral to the Cohu Model 631520010000 video camera. To enable the frame synchroniZation, the GEN projected by the video projector 12 must be aligned With the 15 In operation, the invention is used in a darkened room such that the only visible light illuminating the object 4 is LOCK ports of the tWo video cameras 10a and 10b are connected by means of a video cable 40. The video camera lenses 30a and 30b of this embodiment are also mounted using lens mounts With means for vertical from the video projector 12. The observer 6 vieWs the object 4 from nearly the same perspective as that of the video camera 10 so that the region of the object 4 being illumi nated by the video projector 12 is Within the observer’s ?eld of vieW. The observer 6 adjusts the brightness and contrast controls of the video projector 12 to achieve the optimum enhancement of the object 4. position adjustment to correct for the keystone distortion introduced by the Epson video projector. The electrical signals at the outputs of the focused and defocused video cameras 10a and 10b are ampli?ed and As mentioned previously, such a device could be used to offset by means of variable gain and offset ampli?ers 20 and 22. The signals at the output of the ampli?ers 20 and 22 are subtracted by means of a difference ampli?er 24, and the difference signal is fed to the input of another variable gain and offset ampli?er 26. Since the horiZontal and vertical synchroniZation signals are lost in the subtraction of the enhance the contrast of objects vieWed by patients suffering from degeneration of the macula retinae. The apparatus could also ?nd application in surgery Where it Would be used as an illumination device to make it easier for a surgeon to 30 the horiZontal and vertical synchroniZation signals from one of the video cameras. The composite video signal at the output of the summing circuit 38 is fed to the input of the performances, and discotheques. It is contemplated, and Will be apparent to those skilled in 35 the art from the foregoing speci?cation, draWings, and eXamples that modi?cations and/or changes may be made in the embodiments of the invention. Accordingly, it is expressly intended that the foregoing is illustrative of pre ferred embodiments only, not limiting thereto, and that the true spirit and scope of the present invention be determined by reference to the appended claims. What is claimed is: 1. An illumination apparatus Which alters the visual video projector 12. As With the previously described embodiment, the video projector 12 projects the visible-light object image onto the beam separator 16 Which re?ects the object image onto the object 4. In this manner, the edge enhanced image features overlay the object features. contrast betWeen bright and dark areas of an object as sensed In a second alternative embodiment of the invention, a logarithmic subtraction of the video signals from the tWo are also contemplated in the entertainment area, such as the creation of interesting lighting effects at concerts, theatrical video camera signals, these signals must be added back to the difference signal to form a composite video signal. This is accomplished by summing circuit 38 Where the difference video signal at the output of the ampli?er 26 is summed With distinguish similar types of tissue. Numerous applications 45 by a direct observer of the object, the apparatus comprising: video cameras is performed. With continued reference to FIG. 3, the ampli?ers 20 and 22 of this embodiment are a light source Which illuminates the object With source logarithmic ampli?ers, and the ampli?er 26 is an inverse a video imaging means Which measures source light light having a ?rst property; logarithmic ampli?er. re?ected from the object, the re?ected light measured Athird alternative embodiment of the invention performs in the form of an image, said video imaging means the subtraction of the tWo video camera signals in a digital creating a video output signal representative of the image; format. As shoWn in FIG. 4, the analog video signals at the outputs of the video cameras 10a and 10b are converted into digital format by an analog-to-digital frame capture device 32, such as a Miro DC-20 Video Capture board. Acomputer 55 object, forming a visual image Which is representative of the visual image received by said video imaging means, such that the visual image projected by said 34 incorporating a high-speed processor, such as a Pentium processor operating at 133 MHZ, and suf?cient memory, such as 32 megabytes of RAM, calculates the difference of the focused and defocused video signals at about 2—5 frames per second. It is contemplated that higher frame rates may be attained by means of a faster processor. The digital differ ence signal is fed to a digital-to-analog (D/A) video output device 36, such as a Miro 20-TD Live Video Display board, Which converts the digital difference signal into an analog 60 video signal that is compatible With the video projector 12. 65 With reference to FIGS. 5a and 5b, the video signal at the output of the summing circuit 38, or at the output of the D/A a video projector Which receives the video output signal from said video imaging means and projects video projector light having a second property onto the video projector illuminates the object from the same perspective that said video imaging means vieWs the object, Whereby the features of the projected visual image overlay the corresponding features of the object; and a ?lter Which distinguishes betWeen the ?rst and second properties and prevents the video projector light from reaching said video imaging means While alloWing the source light, re?ected from the object, to reach said 5,969,754 10 video imaging means, thus eliminating positive feed of a focused image, said camera creating a ?rst video output signal representative of the focused image; back Which Would degrade the desired visual effect. 2. The illumination apparatus of claim 1 further compris ing a beam separator Which re?ects a portion and transmits a portion of the light that reaches it, said beam separator being positioned betWeen said video imaging means and the object, and betWeen said video projector and the object. 3. The illumination apparatus of claim 2 Wherein said ?lter is of a type Which transmits infrared light but not visible light, and said beam separator is of a type Which a second video camera Which measures source light re?ected from the object, the re?ected light measured in the form of a defocused image, said camera creating a second video output signal representative of the defocused image; an analog-to-digital frame capture means Which converts the analog video signals at the output of said ?rst and 10 re?ects visible light and transmits infrared light. be processed by a digital processor; the digital processor Which performs a digital subtraction of the tWo digital video signals to form a digital difference signal; and 4. The illumination apparatus of claim 2 Wherein said ?lter is of a type Which transmits infrared light but not visible light, and said beam separator is of a type Which transmits visible light and re?ects infrared light. 15 5. The illumination apparatus of claim 1 Wherein said signal. projector. 11. The illumination apparatus of claim 1 further com prising a distance measuring device Which measures the 6. The illumination apparatus of claim 1 Wherein said video projector is a digital mirror display (DMD) video projector. 7. The illumination apparatus of claim 1 Wherein said video imaging means is a charge coupled device (CCD) video camera. 25 a ?rst video camera Which measures source light re?ected from the object, the re?ected light measured in the form of a focused image, said camera creating a ?rst video output signal representative of the focused image; distance betWeen the illumination apparatus and the object and produces an electrical signal representative of this distance, said video imaging means and said video projector being operable to receive the electrical signal from said distance measuring device and focus the object image cor responding to the distance represented by the electrical signal from said distance measuring device. 12. The illumination apparatus of claim 1 Wherein the light emanating from said light source is infrared light. 13. The illumination apparatus of claim 12 Wherein said light source is comprised of a White light source housed in a container that only alloWs infrared light to escape. 14. The illumination apparatus of claim 12 Wherein said a second video camera Which measures source light re?ected from the object, the re?ected light measured in the form of a defocused image, said camera creating a second video output signal representative of the defocused image; and a digital-to-analog frame output means Which converts the digital difference signal into an analog video output video projector is a liquid crystal display (LCD) video 8. The illumination apparatus of claim 1 Wherein said video imaging means includes: second video cameras into a digital format Which may light source is comprised of an array of infrared light 35 a difference ampli?er Which produces at its output a video emitting diodes. 15. The illumination apparatus of claim 1 Wherein said ?lter comprises: signal representing the difference betWeen the ?rst and second video output signals present at its input. a ?rst shutter means Which opens and closes cyclically, said ?rst shutter means being open during a ?rst 9. The illumination apparatus of claim 1 Wherein said video imaging means includes: ?rst shutter means alloWing source light re?ected from a ?rst video camera Which measures source light re?ected the object to reach the video imaging means only half-cycle and closed during a second half-cycle, said from the object, the re?ected light measured in the form during the ?rst half-cycle; of a focused image, said camera creating a video output signal representative of the focused image; a second video camera Which measures source light 45 re?ected from the object, the re?ected light measured in the form of a defocused image, said camera creating a video output signal representative of the defocused image; logarithmic video signal; second logarithmic video signal; half-cycle and open during a second half-cycle, said second shutter means alloWing light projected from the video projector to reach the object only during the second half-cycle; and a synchroniZing means Which causes the ?rst shutter means to open only after the second shutter means is a ?rst logarithmic ampli?er Which converts the video signal at the output of said ?rst video camera into a ?rst a second logarithmic ampli?er Which converts the video signal at the output of said second video camera into a a second shutter means Which opens and closes cyclically, said second shutter means being closed during a ?rst 55 completely closed, and causes the second shutter means to open only after the ?rst shutter means is completely closed. 16. The illumination apparatus of claim 15 Wherein said ?rst and second shutter means operate at no less than 120 cycles per second. a difference ampli?er Which produces at its output a logarithmic video signal representing the difference 17. A method of altering the visual contrast betWeen betWeen the ?rst and second logarithmic video signals at its input; and an inverse logarithmic ampli?er Which produces at its output a video signal Which is the inverse logarithm of the logarithmic difference video signal at its input. bright and dark areas of an object as sensed by a direct 10. The illumination apparatus of claim 1 Wherein said video imaging means includes: a ?rst video camera Which measures source light re?ected from the object, the re?ected light measured in the form observer of the object, the method comprising the steps of: illuminating the object by means of a light source having a ?rst property; measuring the light re?ected from the object in the form 65 of an image and creating a video output signal repre sentative of the image; projecting a visual image With light having a second property, Which is representative of the video output 5,969,754 11 12 signal at the output of the light measuring means, onto measuring the light re?ected from the object in the form the object in such a manner that the projected visual of a defocused image and creating a second linear video output, signal representative of the defocused image; image illuminates the object from the same perspective that the light measuring means vieWs the object, thus causing the features of the projected visual image to overlay the corresponding features of the object; and ?ltering the light Which enters the light measuring means such that light having the second property from the converting the ?rst linear video signal, Which represents the focused image, into a ?rst logarithmic video signal; converting the second linear video signal, Which repre sents the defocused image, into a second logarithmic video signal; subtracting the ?rst logarithmic video signal from the projecting means is not measured by the light measur ing means, While light having the ?rst property from the illuminating means, Which is re?ected from the object, is measured by the light measuring means, thus elimi nating positive feedback Which Would degrade the 10 logarithmic video signal; and converting the difference logarithmic video signal into a linear video output signal representative of the object image. desired visual effect. 23. A method of altering the visual contrast betWeen 18. The method of claim 17 Wherein the light measuring bright and dark areas of an object as sensed by a direct means is a CCD video camera. observer of the object, the method comprising the steps of: illuminating the object by means of an infrared light 19. The method of claim 17 Wherein the projecting means is an LCD video projector. 20. The method of claim 17 Wherein the projecting means is a DMD video projector. source; measuring the infrared light re?ected from the object in the form of an image and creating a video output signal 21. The method of claim 17 Wherein said light measuring step further comprises the steps of: measuring the light re?ected from the object in the form representative of the image; of a focused image and creating a ?rst linear video output signal representative of the focused image; 25 measuring the light re?ected from the object in the form of a defocused image and creating a second linear video output signal representative of the defocused image; and subtracting the ?rst linear video signal from the second linear video signal to form a difference linear video output signal. 22. The method of claim 17 Wherein said light measuring step further comprises the steps of: measuring the light re?ected from the object in the form second logarithmic video signal to form a difference projecting a visual image With visible light, Which is representative of the video output signal at the output of the light measuring means, onto the object in such a manner that the projected visual image illuminates the object from the same perspective that the light mea suring means vieWs the object, thus causing the fea tures of the projected visual image to overlay the corresponding features of the object; and ?ltering the light Which enters the light measuring means such that the visible light from the projecting means is not measured by the light measuring means, While infrared light from the light source, Which is re?ected from the object, is measured by the light measuring 35 means, thus eliminating positive feedback Which Would degrade the desired visual effect. of a focused image and creating a ?rst linear video output signal representative of the focused image; * * * * *
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