US20030035048A1 - LED illumination system for endoscopic cameras - Google Patents

Abstract

An illumination system for an endoscopic camera has a plurality of light emitting diodes mounted to a substrate. The substrate is adapted for attachment at the distal end of the endoscope. Each LED is contained within a reflector cup which directs the angular dispersion of emitted light toward the object to be viewed.

Description

• This is a continuation-in-part of co-pending U.S. patent application Ser. No. 905,278 filed Jun. 26, 1992, for “Single Sensor Video Imaging System and Method Using Sequential Color Object Illumination”.[0001]
• Be it known that I, John I. Shipp, a citizen of the United States, residing at 104 Short Springs Road, Tullahoma, Tenn. 37388, have invented a new and useful ΘLED Illumination System for Endoscopic Cameras”.[0002]
BACKGROUND OF THE INVENTION
• The present invention relates generally to light sources used to illuminate body cavities during laparascopic surgery, and more particularly to a light assembly mounted in the distal end of an endoscope which emits white light, or red, blue, and green light within the body cavity during surgery.[0003]
• Because of varying sizes and geometries, the interiors of various body cavities have different requirements for adequately illuminating them during the use of laparascopic (or endoscopic) cameras. An insufflated abdominal cavity, for example, has a volume of several liters, with the distance from the peritoneum to the liver bed ranging from 5 to 12 centimeters, depending upon the size and obesity of the patient. The geometry of the cavity is such that an angular field of view of between 50 to 80 degrees is desired for observation and illumination. Typical laparascopic surgical procedures necessitate endoscope-to-object distances of 1.5 to 15 centimeters.[0004]
• Several illumination techniques are employed in the prior art. Where the endoscopic camera system uses white light illumination, a Xenon light source is typically focused onto one end of a flexible fiber optics cable. The other end of the cable is attached to a 90 degree coupling attached to an endoscope, the periphery of which comprises an annular fiber optics bundle terminating at the distal end of the endoscope. Light is emitted from the annular (donut shaped) fiber bundle into the body cavity where a portion of it is reflected and captured by the objective lens of the endoscope and relayed through the center of the scope to the CCD detector array. The white light thus must be separated, after the illumination step, into three primary components, usually red, green, and blue, before it can be processed into a color image by a non-sequential color CCD camera.[0005]
• Field sequential cameras, on the other hand, utilize light sources which usually are separated into three primary colors prior to illumination of the object. Prior art sequential cameras, such as that described in U.S. Pat. No. 4,631,582 for example, utilize rotating segmented color filters in the path of white light sources, or color filters in the path of sequentially illuminated white strobe lights.[0006]
• There are several problems associated with the prior art. Most light sources of the prior art are large, cumbersome, and inefficient. Thus, the efficiency of collection and transmission of light from a Xenon tube to the body cavity is poor, often as low as 0.1 per cent. It is also difficult to match the angular spread of the light from the fiber optics cable to that of the angular field of view of the objective lens. Either the spread is too large, causing light to fall in areas where it is unusable, or the spread is smaller than the angular field of view of the objective, thereby causing vignetting. Additionally, the light distribution from prior art illumination sources is often a problem. A dark spot generally is located in the center of the picture causing the image quality to be inferior, particularly at close object distances. Also, the fiber optics cable used in prior art illumination devices comes into contact with the sterile zone in the operating room and thus must be re-sterilized before each use. The sterilization process often causes catastrophic damage to, or degrades, the cable. The present invention solves these and other problems characteristic of prior art laparascopic illumination systems.[0007]
SUMMARY OF THE INVENTION
• An object of the present invention is to provide a system for illuminating body cavities during laparascopic surgery which is optically and energy efficient and which provides the desired angular dispersion of illuminating light.[0008]
• Another object of the present invention is to eliminate the light-loss, size, and sterilization problems inherent in the use of fiber-optic cables and bundles.[0009]
• Yet another object of the present invention is to adapt an illumination system for use with a field sequential single sensor video camera or with a sequential chrominance-luminance YC camera system.[0010]
• In accordance with these and other objectives which will be apparent to those skilled in the art, the present invention comprises an efficient, compact, light source mounted in the distal end of an endoscope, usable with a field sequential single sensor video imaging system such as that described in co-pending U.S. patent application Ser. No. 905,278. A series of four red, fourteen green, and ten blue light emitting diodes (LED's) are mounted and arranged on a ceramic substrate in a circular pattern concentrically around the optical path of the endoscope. A reflector cup surrounds each LED to help control the angular distribution of the emitted light. The LED's are electrically wired to an illumination circuit which causes them to emit red, blue, and green light in synchronization with the field period of a CCD endoscopic camera. Because the LED's are mounted in the distal end of the endoscope, the typical prior art light loss through fiber optics cables and connections is avoided and the need for cable sterilization is eliminated. The LED arrangement uniformly illuminates objects within body cavities with the required angular dispersion. The efficiency of the light source allows for battery operation of the camera and lights making the system much more portable.[0011]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is an oblique view of a first embodiment of the present invention in which the illumination means is a distally mounted LED assembly.[0012]
• FIG. 2 is a schematic plan view of the LED assembly of FIG. 1, showing the approximate layout of the 28 LED's and power connection points on the substrate.[0013]
• FIG. 3 is an enlarged view of a red LED chip as used in the present invention, showing its wired connections to the substrate of the illumination means.[0014]
• FIG. 4 is an enlarged view of a green or blue LED chip as used in the present invention, showing its wired connections to the substrate of the illumination means.[0015]
• FIG. 5 is an electrical schematic diagram of the LED assembly.[0016]
• FIG. 6[0017]ais top view of the reflector cup used in conjunction with each of the LED's of the present invention.
• FIG. 6[0018]bis a side view of the reflector cup of FIG. 6a.
• FIG. 6[0019]cis a cutaway side view of the reflector cup of FIGS. 6aand6b.
• FIG. 7 is a side view of a single LED chip or die mounted within a reflector cup, further showing the angles of light emitted from and reflected therein.[0020]
• FIG. 8 is a cross-sectional side view of the distal end of the endoscope to which the present invention is mounted.[0021]
• FIG. 9 is an electrical schematic of a circuit used for white balancing of the three colors emitted by the illumination system of the present invention.[0022]
• FIGS. 10[0023]aandbare plan and cutaway side views of a second embodiment of the LED assembly of the present invention in which the reflector cups are formed integral to the substrate.
• FIGS. 11[0024]aandbare plan and cutaway side views of the illumination means of FIG. 10a,after the LED wiring pads have been etched and gold flashed.
• FIGS. 12[0025]aandbare plan and cutaway side views of the illumination means of FIG. 11a,after mounting of the LED dies to the reflector cups.
• FIGS. 13[0026]aandbare plan and cutaway side views of the illumination means of FIG. 12, after wiring bonding of the anodes or cathodes of the LED's to the wiring pads.
• FIG. 14 is a block diagram of a single sensor sequential video imaging system used in conjunction with the illumination system of the present invention.[0027]
• FIG. 15 is a side view of second embodiment of the illumination system in which an LED assembly is mounted in the camera head, with light transmitted to the distal end of the endoscope via optical fibers or plexiglass.[0028]
• FIG. 16 is a cutaway side view of a third embodiment of the illumination means in which an LED assembly is combined with a white light source at the distal end of the endoscope.[0029]
DESCRIPTION OF THE PREFERRED EMBODIMENT
• Looking first at FIG. 8, the illumination system of the present invention is shown, in which an illumination means[0030]10, here an LED assembly, is adapted for mounting at the distal end of a10 mm outsidediameter endoscope15, which is the typical size used in abdominal laparascopic procedures. As seen on FIG. 1, this first embodiment of illumination means10 incorporates inner and outer rings of28 individual LED chips or dies22 mounted toseparate reflector cups21 which are then mechanically bonded to a base plate, which in this embodiment is an annularceramic substrate20. Acylindrical aperture24 passes through the center ofsubstrate20.
• As shown of FIG. 8,[0031]aperture24 will have a diameter larger than the entrance pupil (not shown) of a conventional endoscopeobjective lens system52 and slightly less than stepped downsection54 oflens system52. Typically,lens system52 will have a 6 mm diameter and with an entrance pupil of approximately 3 mm diameter.Aperture24 allows light reflected from the object being viewed to pass throughassembly10 tolens system52 unhindered.
• The outside diameter of[0032]substrate20, typically 9 mm, is sized and configured to mate with the inside diameter of astainless steel sheath53 ofendoscope15 that houses illumination means10 andobjective lens system52. Aninner sleeve51, preferably made of copper, lines the inner surface ofsheath53 and at its distal end, turns inward to form a base portion56 to contact the proximal surface ofsubstrate20.Sleeve51 acts as a heat sink for illumination means10. To insure good thermal contact betweensubstrate20 andsleeve51, a light coating of zinc oxide is applied to the proximal surface ofsubstrate20. A translucentprotective window50 is mounted distally of illumination means10.
• The LED assembly illumination means[0033]10 as described herein has an efficiency of approximately 1.2 per cent (light power output divided by electrical power input). This requires the dissipation of about 3.5 watts of thermal energy from the tip ofendoscope15. The heat dissipation is primarily by radiation and convection fromstainless steel sheath53. Although stainless steel is a poor thermal conductor (as compared to copper), copper cannot be used as the external sheath owing to its lack of biocompatability with the body. This and the size of the thermal load requires thatsubstrate20 contact copper inner sleeve51 (see FIG. 8) to dissipate the thermal load along the full length ofendoscope15 with minimal gradient.Inner sleeve51, preferably having a wall thickness of approximately 1.5 mm, thermally contactsstainless steel sheath53 so that a very small temperature drop occurs from the outside surface ofsleeve51 to theouter surface sheath53, thus allowing maximum radiated and convective heat dissipation from the stainless steel. Using this technique, the average temperature rise ofendoscope15 is held to 20 degrees centigrade for a thermal load of 3.5 watts. By contrast, the average temperature rise for an all stainless steel construction (including sleeve51) exceeds 50 degrees centigrade and the distal tip temperature exceeds 90 degrees centigrade for an ambient temperature of 20 degrees centigrade.
• Looking now at FIGS.[0034]1-4, LED illumination means10 is fabricated by first depositing in a conventional manner the metal required for interconnecting land and lead bond pad patterns onto the 0.5 mm thick, highpurity alumina substrate20. Next, reflector cups21 are soldered tosubstrate20. The LED die22 are bonded in place toreflector cups21 with a conductive epoxy,cathode42 down forblue die32 and green die31 as shown on FIG. 4, and with anode41 down forred die30, as shown in FIG. 3. Forred die30,cathodes42 are then lead bonded to theirrespective pads44, usingwire bonds43, as are anodes41 in the case of blue andgreen die32,31.
• As seen on FIG. 2, six electrical connections must be made to illumination means[0035]10: First and second redLED power connectors33,37, first and second greenLED power connectors34,35, blueLED power connector36, andground connector38. These six leads pass through their respective substrate cutouts23 (FIG. 1) and then are soldered in place on the top or distal surface ofsubstrate20. Power is supplied to illumination means10 from a battery pack (not shown) in the proximal end ofendoscope15.
• In accordance with FIGS. 2 and 5, two each of two[0036]red die30 are wired in series while the tenblue die32 and fourteengreen die31 are wired in parallel. Owing to their higher efficiency,red LEDs30 have a much smaller forward voltage drop than do blue orgreen LEDs32,31 at the same current. This wiring arrangement more nearly matches the voltage required to drive the three LED strings shown in FIG. 5, thus minimizing voltage transients as the camera timing function switches sequentially among and between the three colors. In a preferred embodiment of the illumination system, the supply voltage (VR) forred die30 will be 3.9 V, with a total red LED current of 200 mA. The supply voltage for blue LED die32 (VB) will be 5.5 V, at 1.2 A total blue LED current. Green LED die31 will have a supply voltage (VG) of 3.3 V, at 1.2 A total current.
• In choosing the number of each color of the LEDs required to adequately light a particular body cavity, the character of the object must be considered as well as the amplitude and spatial resolution of the three primary colors. It is known that the spatial resolution of the color components from a body cavity contain red data with high frequency variation, green data with little substantial variation, and blue data with intermediate frequency variation. Further, images from body cavities have very little blue amplitude component as compared with red and green.[0037]
• The other factors that effect the number of die needed of each color are LED efficiency, CCD video detector quantum efficiency at each of the three wavelengths, and the needed signal-to-noise ratio. The circuit shown in FIG. 9 can be used in the system of the present invention to provide proper color balance. Using a[0038]switch64 synchronized with the field switching circuit of the camera system described above, the video data input (as reflected from the object field intoendoscope15 is alternated between red, green, and blue positions. The red primary color input is not adjusted. Blue andgreen video amplifiers60 and62 are used to compensate and adjust the blue and green video levels, using amplifiergain control inputs61 and63. With a blue channel gain of approximately 28 dB (over the red channel), and a green channel gain of approximately 6 dB, using 4 AlGaAr red LED's30, 14 GaP green LED's31, and 10 silicon carbide blue LED's32, driven in a one third duty cycle at 100 ma peak current results in a combined signal-to-noise ratio of approximately 35 dB at an object distance of 75 mm inside a typical abdominal cavity.
• Prior art light sources typically deliver to the abdominal cavity 200 microwatts of optical energy per cubic centimeter of volume occupied by the light source, or about 60 milliwatts of optical power per pound of weight of the source. The[0039]LED assemblies10 of FIG. 1 or FIGS. 13aandbcan deliver 200 milliwatts per cubic centimeter of volume or 5 watts per pound of weight. Since the single sensor sequential camera described above requires approximately 5 to 10 milliwatts of light output, the illumination system of the present invention can be made small and light in weight as compared to the prior art, thus allowing it to be highly portable and installed in the distal end of an endoscope.
• The power distribution of the light from[0040]endoscope15 should be as homogenous as possible to insure adequate lighting in all zones of the image and, in the case of sequential cameras, the three colors should be coincident to avoid chromatic effects. FIG. 7 shows a side view of a typical LED die22 positioned within areflector cup21. LED die22 is almost cubic in shape, with each dimension being approximately 250 microns. Actually, most die are slightly trapezoidal in shape, being somewhat larger at the base than at the top. The horizontal cross sections are usually square. Light is emitted from thetop edges3 and5 ofdie22, primarily in a small horizontal angular cone and from thetop surface4 in, more or less, a cosine distribution. The fraction of the light emitted from the edges as compared to the top surface depends on the technology used in constructingdie22. Typically, for ablue LED32 made of a silicon carbide die, the edge emission accounts for 80 per cent of the total light output. Thus, mounting each die22 in aseparate reflector cup21 can serve to control the angular emission of a significant portion of the light. FIG. 7 depicts a die22 mounted such that the edge emission is located in a 20 degree cone centered at the focus of ahemispherical reflecting cup21. It can be seen that the rays are redirected into a 36 degree cone about the vertical axis. The reflected light adds to the light emitted from thetop surface4 ofdie22. If LED die22 were used without reflectingcup21, none of the edge emitted light would reach the object field.
• Control of the depth of mounting of[0041]die22 withinreflector cup21 gives a considerable degree of control on the dispersion angle. Moving die22 lower or higher than the focal point ofreflector cup21 dramatically increases the angular dispersion. FIGS. 6a, b,andcillustrate a preferred geometry ofreflector cup21 which is molded of very high purity alumina to have a flat, centrally disposed die mountingsurface26 with a 0.6 mm diameter, located approximately 0.4 mm below the top ofcup21. Aconcave section25 surroundssurface26 and extends upwardly and outwardly a linear distance of approximately 0.68 mm, thereby defining an outer diameter ofcup21 of approximately 1.3 mm. The radius of curvature ofconcave section25 is approximately 0.56 mm. An integrally formedpost27 facilitates mechanical attachment of21 tosubstrate20.
• FIGS.[0042]10-13 illustrate an alternate embodiment of LED illumination means10 in which reflector cups21 are molded intoceramic substrate20. Electrical interconnections are made by first metal depositing the entire top or distal surface ofsubstrate20 and etching away the areas that are not electrically connected, leaving the wire bond pattern shown on FIG. 11a.LED die22 are then bonded to die mountingsurface26 of reflector cups21, as seen in FIGS. 12aandb.Lead bonding to the LED die is accomplished in the same manner as shown in FIGS. 3 and 4, resulting in illumination means10 shown in FIGS. 13aandb.
• The illumination system described above is ideally suited for use with applicant's “Single Sensor Video Imaging System and Method Using Sequential Color Object Illumination”, described in detail in co-pending U.S. patent application Ser. No. 905,278, the specification and drawings of which, as amended, are incorporated herein by reference. Referring to FIG. 14, there is shown by block diagram representation a field sequential video imaging system in combination with the illumination system of the present invention, as well as the basic method by which an object to be viewed is illuminated and color video image data is processed. The method begins by illuminating an object (not shown) with light from a first primary color light source,[0043]red LED30 for example, for a period of time typically equal to a standard television field period. Conventionally, this period is {fraction (1/60)} second.Red LED30 is activated for this field period by one of three outputs from the divide by threering counter14, which has been selected by the vertical drive signal of thesensor2 inendoscope15, preferably a conventional charge coupled device (CCD) assembly, such as the model CCB/M27 from Sony Corporation of America. However, any appropriate photo sensor array can be used. The light reflected from the object is focused ontosensor2 bylens system52, also of conventional design.
• At the end of the first field period, the vertical drive signal makes a transition and thereby selects the second output of the[0044]ring counter14, resulting in the deactivation ofred LED30 and the activation of a second primary light source,green LED31 for example, for one field period. During this second field period, analog data measuring the response ofsensor2 to light reflected fromred LED30 is captured by analog-to-digital (A/D)converter16 while integration of the second signal (from green LED31) is occurring insensor2. The output from A/D16 is provided both to a firstdigital delay unit17 and amatrix switch18. First delay17 delays the digitized signal for a time period equal to one field period.
• The output signals of[0045]ring counter14 are timed and synchronized such thatmatrix switch18 connects the output of A/D16 (reference DO) to first digital-to-analog converter (DAC)19.First DAC19 converts the first captured and digitized primary color signal corresponding to the first primary color, fromred LED30, back to analog form, to be used as the odd field video data of the first primary color signal, red for example.
• Following the second field period, the object is illuminated by a third primary color light source,[0046]blue LED32 for example, for a third period of time equal to a field period. This is accomplished by the vertical drive signal from thesensor2 making a transition, thereby deactivatinggreen LED31 and activatingblue LED32. During this third field period, the third primary color light reflected from the object is focused ontosensor2. Simultaneously with integration of the third primary color signal insensor2, the analog video signal corresponding to the level of reflected second primary color light is captured and digitized by A/D16. At the beginning of this third field period, the outputs of thering counter14 are in such a state as to connect the output from the A/D16 (D0) to a second DAC70, and the output from first delay17 (D1) tofirst DAC19. Thus, response of thesensor15 to the first primary color signal, fromred LED30, is again presented at the output offirst DAC19 for the even field period of the first primary color. The output of second DAC70 is the analog video signal corresponding to the second primary color fromgreen LED31.
• Following the third field period, the object is again illuminated with[0047]red LED30 for a fourth period of time equal to a standard field period. This is accomplished by the vertical drive signal ofsensor2 making a transition which causesgreen LED32 to be deactivated andred LED30 to again be activated. The third color analog signal is captured fromsensor2 and digitized by the A/D16 during this fourth field period, while the first color light signal is again being integrated.
• The second color captured and digitized signal is delayed by[0048]first delay17 and the first color digitized signal is further delayed by one field period by asecond delay unit72. At the beginning of the fourth field period, the outputs ofring counter14 are such that A/D16 output (DO) is connected to a third DAC71, the output of the first delay17 (D1) is connected to second DAC70, and the output of second delay72 (D2) is connected tofirst DAC19. Also during this fourth field period, the second color digital signal is reconverted to analog format by second DAC70 and becomes the odd field of the second color signal. Likewise the captured digitized third primary signal (not delayed) is reconverted to analog format by third DAC71 and becomes the odd field of the third color video signal.
• The process continues, in the manner previously described, with repeated successive second, third, and fourth illumination periods. It will be apparent to those skilled in the art that the first field or illumination period is operationally identical to the seventh illumination period, except that the first illumination period begins with[0049]sensor2 and related devices in a starting or “0-state” condition. It should be noted that if precise field period analog delay lines were available it would not be necessary to digitize the output ofsensor2 and then reconvert it to analog format. Rather, the sequential analog signals could be merely switched bymatrix switch18 to their respective color signal outputs.
• The output signals from DAC's[0050]19,70, and71, after processing in the manner described, now correspond to standard video signals capable of display by a conventional RGBcolor television monitor77, in conjunction with a standard television synchronization signal obtainable fromsensor2, through sync driver-amplifier80. Accordingly, in the preferred embodiment, the resulting video image will comprise conventional odd and even frames or fields of data comprising typically 262.5 horizontal lines each which are interlaced and displayed for one standard field period ({fraction (1/60)} second) each, producing a completed television video image of525 horizontal lines.
• As an alternative to using an RGB monitor, the digitized primary color signals and sync signal can be sent to the inputs of a standard NTSC format modulator/[0051]encoder unit28, for display on a standard NTSCformat television receiver29.
• To obtain conventional chrominance and luminance color video signals, red LED's[0052]30 can be activated simultaneously with green LED's31 during periods which are sequentially interspersed between periods of separate illumination by red LED's30 and blue LED's32. The reflected light from the object resulting therefrom is then used to obtain signal levels from which chrominance and luminance signals can be calculated and generated in manner well known to those skilled in the art.
• FIG. 15 illustrates a second embodiment of the illumination system of the present invention in which illumination means[0053]10 includes both an LED assembly or other light source mounted at the proximal or camera head end ofendoscope15 and a light transmission means, such as fiber optic cables11 which extend alongsheath53 to the distal end ofendoscope15.
• FIG. 16 shows another embodiment of the illumination system in which illumination means[0054]10 includes both an LED assembly11 and awhite light source12 which extends throughaperture24 of assembly11. Whitelight source12 could be a Xenon tube, for example, which can be pulsed to conform with sequential color illumination requirements. Thus, by placing a blue filter in front ofwhite light source12, blue light can be obtained and low efficiency blue LEDs could be eliminated from LED assembly11.
• Thus, although there have been described particular embodiments of the present invention of a new and useful LED Illumination System for Endoscopic Cameras, it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims. Further, although there have been described certain dimensions used in the preferred embodiment, it is not intended that such dimensions be construed as limitations upon the scope of this invention except as set forth in the following claims.[0055]

Claims (19)

What I claim is:

1. An illumination system for an endoscope comprising:

a. illumination means for directing light on an object to be viewed by said endoscope;

b. said illumination means adapted for mounting to the distal end of said endoscope.

2. The illumination system ofclaim 1, said illumination means comprising a plurality of LED chips mounted to a base plate.

3. The illumination system ofclaim 2 further comprising reflector means for directing the angular emission of light from said illumination means.

4. The illumination system ofclaim 3, said reflector means comprising substantially hemispherical reflector cups surrounding each of said LED chips.

5. The illumination system ofclaim 4, said reflector cups formed integral to said base plate.

6. The illumination system ofclaim 1, said illumination means comprising an LED assembly mounted at the proximal end of said endoscope and means for transmitting light emitted from said LED assembly to the distal end of said endoscope.

7. The illumination system ofclaim 2, said illumination system comprising at least two red LED's wired in series, and a substantially larger number of both blue LED's and green LED's wired in parallel, whereby electrical transients introduced into said system during color switching are minimized.

8. The illumination system ofclaim 2, said illumination means further comprising a white light source mounted on said base plate.

9. The illumination system of either of claims2 through8, said base plate comprising an annular ceramic substrate and an aperture centrally disposed within said substrate.

10. An endoscopic camera in combination with an illumination system comprising:

a. a sheath;

b. illumination means mounted at the distal end of said sheath;

c. a video detector; and

d. an objective lens system mounted within said sheath between said illumination means and said video detector.

11. The endoscopic camera and illumination system combination ofclaim 10 further comprising means to activate said illumination means in synchronization with said video detector whereby said illumination means illuminates a body cavity proximate said camera with sequences of colored light.

12. An endoscopic video camera system comprising:

a. an illumination system for sequentially illuminating an object, said illumination system including an illumination means having first, second, and third primary color light sources, said illumination means mounted at the distal end of a camera sheath;

b. means for separately and successively activating said first, second, and third primary color light sources for equal standard television field periods;

c. means for focusing a primary color light reflected from said object onto a sensor, said sensor providing a primary color level analog data responsive to the level of said primary color light focused onto said sensor;

d. means for capturing said primary color level analog data from said sensor;

e. A/D converter means for converting said captured primary color level analog data to digital format, thereby providing digitized captured primary color level data;

f. first delay means coupled to the output of said A/D converter means for delaying for a standard television field period said digitized captured primary color level data;

g. second delay means coupled to the output of said first delay means for further delaying for a standard television field period said digitized captured primary color level data;

h. first, second, and third digital-to-analog converter means for converting said digitized captured primary color level data from said A/D converter means, from said first delay means, and from said second delay means, thereby providing re-converted first, second, and third primary color level analog data, said re-converted first, second, and third primary color level analog data representing color television video signals corresponding to said first, second, and third primary colors; and

i. means for successively switching the outputs of said A/D converter means, said first delay means, and said second delay means to said first, second, and third digital-to-analog converter means.

13. The system ofclaim 12 further comprising monitor means operatively connected to the outputs of said first, second, and third digital-to-analog converter means.

14. The apparatus ofclaim 13 further comprising means for wireless transmission of said primary color level analog data from said sensor to a remote location.

15. A compact light source for illuminating an object while in a body cavity, said light source comprising first, second, and third color LED's fixed to a common substrate, said first, second, and third color LED's electrically connected to said substrate and to each other in a pattern whereby said first, second and third color LED's can be separately operated in a sequential manner.

16. The light source ofclaim 15, further comprising circuit means to operate said first and second color LED's simultaneously whereby chrominance and luminance color video signals can be generated from light reflected from the object being viewed.

17. An endoscopic video camera system comprising:

a. a video camera mounted at the proximal end of an endoscope; and

b. illumination means for emitting light from said system toward an object to be viewed within a body cavity, said illumination means mounted within the distal end of said endoscope.

18. The camera system ofclaim 17, said illumination means comprising a plurality of LED's mounted to a ceramic substrate in an annular pattern around an aperture formed in said substrate.

19. The camera system ofclaim 18 further comprising means for re-directing light emitted from the edges of each of said LED's toward the object to be viewed.

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