Patent Description:
Endoscopy allows a physician to view organs and cavities internal to a patient using an insertable instrument. This is a valuable tool for making diagnoses without needing to guess or perform exploratory surgery. The insertable instruments, sometimes referred to as endoscopes or borescopes, have a portion, such as a tube, that is inserted into the patient and positioned to be close to an organ or cavity of interest.

Endoscopes first came into existence in the early <NUM>'s, and were used primarily for illuminating dark portions of the body (since optical imaging was in its infancy). In the late <NUM>'s, the first fiber optic endoscope capable of capturing an image was developed. A bundle of glass fibers was used to coherently transmit image light from the distal end of the endoscope to a camera. However, there were physical limits on the image quality this seminal imaging endoscope was able to capture: namely, the number of fibers limited the resolution of the image, and the fibers were prone to breaking.

Now endoscopes are capable of capturing high-resolution images, as endoscopes use various modern image processing techniques to provide the physician with as natural a view as possible. For example, the views provided by an endoscope may be capable of mimicking a natural feeling field and depth of view to emulate a physician seeing with her own eyes.

<CIT> relates to a light source device and a photographing observation system including the light source device.

The present invention provides a system for medical diagnosis as set out in claim <NUM>. Further aspects of the present invention are set out in the dependent claims.

Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Not all instances of an element are necessarily labeled so as not to clutter the drawings where appropriate. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described.

Embodiments of a system and method for a tunable color-temperature white light source are described herein. In the following description numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention, which is defined by the claims.

Endoscopes are devices physicians use to view inside of patients without the need to perform exploratory surgery. In general, endoscopes are imaging devices with insertion tubes that are inserted into a patient through (small) incisions. The imaging device provides views from a tip ("distal end") of the insertion tube and displays the view, for example, on a monitor for the physician. The imaging system may provide a stereoscopic view of an area of interest so that a more natural image is presented to the viewer. To generate the stereoscopic view, endoscopes may include multiple image sensors, where each image sensor provides an image of the area of interest from a slightly different perspective. The difference in perspective is intended to emulate the different perspective of human eyes. To further enhance endoscope imaging and aid physicians in diagnosis, the instant disclosure provides an elegant solution to produce substantially white light (or another operator-desired emission spectrum) at the distal end of the endoscope.

The color of an object depends on the spectrum of the illumination light source, as well as the object's own spectral reflectance. When imaging with an endoscope inside a cavity, the illumination source is located at the distal end. To make the colors look "natural" and recognizable to the surgeon, a white light source with a spectrum similar to daylight (e.g., a blackbody emission spectrum at <NUM> °K) is frequently preferred. However, to get the light to the tip of the endoscope, the light source needs to be well-coupled to a fiber optic cable so that the cable can efficiently carry the light to the tip. A broadband lamp or LED can be used as the light source, but coupling efficiency to the fiber may, in some situations, be limited. A laser can couple efficiently to a fiber optic cable; however, the monochromatic laser source will likely produce colors that look unnatural. This may impede the ability of the endoscope operator (e.g., surgeon) from making an accurate diagnosis or properly identify tissue. Additionally, in both the case of laser or broadband illumination, the source emission spectrum is fixed; what looks like "natural" coloring is subjective, so a tunable source is desirable.

As will be discussed in greater detail, a set of discrete lasers are coupled into an illumination fiber bundle, with the relative power of the lasers set by software. The user can set a temperature (T) in the software, and the relative power of the lasers is tuned by the software to illuminate the patient. Thus, the patient looks as if he/she was illuminated by blackbody radiation from an object with the temperature "T". Additionally, in some arrangements contemplated in this disclosure, the user can input any source spectrum characteristics, and the software will tune the lasers to match the desired spectrum.

<FIG> is a block diagram of endoscope system <NUM>, in accordance with an embodiment of the disclosure. Endoscope system <NUM> includes: endoscope body <NUM>; fiber optic cable <NUM>; control logic <NUM>; light controller <NUM>; light source <NUM>; and computer system <NUM> (including data input/output <NUM>, and power input <NUM>). In endoscope system <NUM>, light source <NUM> includes a plurality of light emitters and is optically coupled to a first end of fiber optic cable <NUM>. Each light emitter in light source <NUM> emits a distinct bandwidth of light-depicted as the five photons with five different energies exiting the distal (second) end of fiber optic cable <NUM>. Control logic <NUM> is electrically coupled to the plurality of light emitters to control an emission intensity of each light emitter in the plurality of light emitters. As will be discussed in <FIG>, the light output from a second end of fiber optic cable <NUM> mimics a blackbody emission spectrum to the human eye.

In the depicted embodiment, control logic <NUM> is coupled to receive user input (from computer system <NUM>) and, in response to the user input, independently change the emission intensity of each light emitter in the plurality of light emitters. However, in a different embodiment, user instructions may be directly input into the endoscope (not an attached computer system <NUM>). Although the illustrated embodiment shows endoscope body <NUM> hardwired to computer system <NUM>, in other embodiments endoscope body <NUM> may have its own onboard computer system <NUM> and interface.

Although not depicted to avoid obscuring certain aspects, endoscope system <NUM> may have a lens system for transmitting images from an objective lens to the endoscope user (this may include a relay lens system or a bundle of fiber optics). Endoscope system <NUM> may also have one or more mechanical actuators to guide insertion of fiber optic cable <NUM>, and maneuver fiber optic cable <NUM> through the body. Control logic <NUM> (e.g., a microcontroller) is disposed in the system and electrically coupled to the plurality of light emitters. The controller includes logic that when executed by the controller causes the controller to perform a myriad of operations. For example, in addition to controlling light output, control logic <NUM> may be able to control any of the aforementioned pieces of device architecture (e.g., lens system, image sensors, mechanical actuators, etc.). Control logic <NUM> may be able to precisely control the distances between lenses to focus an image captured by the endoscope, or manipulate the body of fiber optic cable <NUM> with the one or more mechanical actuators.

<FIG> shows an example endoscope emission spectrum <NUM> and a corresponding user-observed blackbody emission spectrum <NUM>, in accordance with an embodiment of the disclosure. In the depicted embodiment, endoscope emission spectrum <NUM> and user-observed blackbody emission spectrum <NUM> have been superimposed on the same graph; this is for comparison purposes only. Both spectra are not drawn to scale.

As illustrated, endoscope emission spectrum <NUM> includes five discrete emission peaks. To achieve the five peaks, five lasers are directed into a fiber. By tuning the relative power of the lasers, a scene with color that approximates user-observed blackbody emission spectrum <NUM> can be rendered. The depicted embodiment may contain, for example, five lasers, with center wavelengths of <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. All lasers may have a bandwidth of <NUM>. These five laser emission peaks may resemble user-observed blackbody emission spectrum <NUM> (which is similar to a <NUM>,<NUM> °K blackbody emission spectrum).

<FIG> illustrates an endoscopic light emitter <NUM>, in accordance with an embodiment of the disclosure. As shown, endoscopic light emitter <NUM> includes: fiber optic cable <NUM>, light source <NUM> (including the plurality of light emitters <NUM>), and control logic <NUM>. Plurality of light emitters <NUM> includes five lasers: laser <NUM>, laser <NUM>, laser <NUM>, laser <NUM>, and laser <NUM>. Each of the plurality of light emitters <NUM> is optically coupled to fiber optic cable <NUM>, and individually electrically coupled to control logic <NUM>. Plurality of light emitters <NUM> each emit a discrete wavelength of light. Laser <NUM> emits the shortest wavelength of light, laser <NUM> emits the second shortest wavelength of light, laser <NUM> emits a longer wavelength of light than laser <NUM>, laser <NUM> emits the second longest wavelength of light, and laser <NUM> emits the longest wavelength of light. The emission intensity or duty cycle (ratio of on-time to off-time) may be varied to output different emission spectra. For example, the relative intensity (or on time) of laser <NUM> may be greater when emulating higher temperature (blue-shifted) blackbody emission spectra. Conversely, the relative intensity (or on time) of laser <NUM> may be greater when emulating lower temperature (red-shifted) blackbody emission spectra.

Although the embodiment depicted in <FIG> shows five lasers, in other embodiments plurality of light emitters <NUM> may have any number of light sources including lasers and/or light emitting diodes. Further, the lasers depicted in <FIG> emit relatively monochromatic light (e.g., light with a bandwidth of less than <NUM>). However, in arrangements contemplated in this disclosure that do not form part of the invention, the bandwidth of plurality of light emitters <NUM> may be larger (on the order of <NUM> or more). In some embodiments, fiber optic cable <NUM> may include cladding to promote total internal reflection (e.g., the cladding may include a reflective metal, or a material with a lower index of refraction than the bulk of fiber optic cable <NUM>) or contain multiple fibers. An image sensor may be coupled to the distal end of the fiber optic cable <NUM>, or an image sensor may be contained in the body of the endoscope, and the fiber optic cable <NUM> may be used to relay image light back to the image sensor.

<FIG> illustrate black body emission spectra (left) and corresponding endoscopic emission spectra (right) ranging from <NUM>,<NUM> to <NUM>,<NUM> °K, in accordance with several embodiments of the disclosure. Each spectrum depicted is merely one example of many possible emission spectra. All of the endoscopic emission spectra depicted here include five separate light sources (e.g., laser diodes, light emitting diodes, gas lasers, etc.). In all of these embodiments, a user may input a temperature of blackbody emission, and the endoscope will output an endoscopic emission spectrum that resembles the blackbody emission spectrum (to the human eye). In other words, the endoscope's discrete emission peaks can be tuned to trick the human eye into seeing a blackbody emission spectrum or other continuous spectrum, such as a phosphor spectrum.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. The relatively low-temperature blackbody spectrum is red-shifted. Accordingly, only three low-energy endoscopic emission peaks are used to approximate blackbody emission spectrum <NUM>. The intensity of these peaks increase monotonically in order of decreasing wavelength.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. Similarly to <FIG>, the relatively low-temperature blackbody spectrum is red-shifted. Thus, only four low-energy endoscopic emission peaks are used to approximate blackbody emission spectrum <NUM>. The intensity of these peaks increase monotonically in order of decreasing wavelength.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. At <NUM>,<NUM> °K blackbody emission spectrum <NUM> starts to blue-shift but is still red-dominant. Accordingly, the lowest energy peak still has the largest intensity, the second lowest energy peak has the second largest intensity, and the middle peak has a lower intensity than the second lowest energy peak. The second highest energy peak has the lowest intensity, and the highest energy peak has the fourth largest intensity.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. Here, despite the blackbody emission spectrum <NUM> blue-shifting relative to the <NUM>,<NUM> °K spectrum, only four of the five lasers are used to form the corresponding endoscopic emission spectrum <NUM>. As shown, the four lowest energy lasers are used to emit the spectrum, and the intensity of each emission peak increases monotonically in order of decreasing wavelength.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. Blackbody emission spectrum <NUM> continues to blue-shift, but is still red dominant. Accordingly, endoscopic emission spectrum <NUM> includes all five laser emission peaks. The highest energy peak has the second lowest intensity, the second highest energy peak has the lowest intensity, the middle energy peak has the third largest intensity, the second lowest energy peak has the second largest intensity, and the lowest energy peak has the largest intensity.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. At <NUM> °K, blackbody emission spectrum <NUM> shows a dramatic blue-shift. To match this shift, the highest energy (lowest wavelength) endoscopic emission peak intensity is at least two times larger than the other peaks. However, the second highest energy peak intensity has a lower intensity than all other peaks. The three lowest energy peak intensities are roughly the same size, but the middle peak (second to lowest energy) is slightly smaller than the other two peaks.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. At <NUM>,<NUM> °K blackbody emission spectrum <NUM> resembles the solar spectrum. It is prominently blue-shifted. The highest energy peak intensity is the largest, the second highest energy peak has the smallest peak intensity, the middle energy peak intensity is larger than the second highest energy peak intensity, and the second lowest energy peak has roughly the same peak intensity as the second highest energy peak intensity. Lastly, the lowest energy peak has roughly the same peak intensity as the middle energy peak.

<FIG> shows an <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. At <NUM>,<NUM> °K, the blackbody emission spectrum <NUM> is greatly blue-shifted. Endoscopic emission spectrum <NUM> is also blue-shifted, with the highest energy peak having the greatest intensity, the second highest energy peak having a lower intensity then the highest energy peak, the third highest energy peak having roughly the same intensity as the second highest energy peak, the second lowest energy peak having the lowest intensity, and the lowest energy peak having the second lowest intensity.

<FIG> shows a <NUM>,<NUM> °K blackbody emission spectrum <NUM>, and the corresponding endoscopic emission spectrum <NUM>. Blackbody emission spectrum <NUM> is the most blue-shifted spectrum depicted. Thus, endoscopic emission spectrum <NUM> is also highly blue-shifted. The highest energy peak is approximately twice as large as every other peak. The next two highest energy peaks are approximately half the size of the highest energy peak, and the two lowest energy peaks are approximately the same size and have a lower intensity than the previous two peaks.

One skilled in the art will observe several trends associated with the above blackbody emission spectra, and their corresponding endoscopic emission spectra: (<NUM>) when the temperature of the blackbody emission spectrum is less than <NUM>,<NUM> °K the plurality of light emitters emit a monotonically increasing spectrum of light (where the light emitter in the plurality of light emitters with the shortest wavelength emission spectrum has the smallest amplitude, and the light emitter in the plurality of light emitters with the longest wavelength emission spectrum has a largest amplitude); (<NUM>) when the temperature of the blackbody emission spectrum is less than <NUM>,<NUM> °K, the light emitter in the plurality of light emitters with the longest wavelength emission spectrum has the largest amplitude; and (<NUM>) when the temperature of the blackbody emission spectrum is greater than <NUM>,<NUM> °K, the light emitter in the plurality of light emitters with the shortest wavelength emission spectrum has the largest amplitude.

<FIG> illustrates a user creating an endoscope emission spectrum, in accordance with an embodiment of the disclosure. As shown, the light emission mode is selected by the user via inputting parameters of a custom continuous emission spectrum into a tablet (or other electronic device). In the depicted embodiment, the user draws the emission spectrum on the screen of a tablet with his/her finger. The tablet wirelessly communicates to endoscope <NUM>, and endoscope <NUM> adjusts its emission spectra to match the spectra drawn on the tablet. One skilled in the art will appreciate that while the illustrated embodiment involves a person drawing the desired spectra on a tablet, any number of other methods for defining a continuous emission spectra may be used. For example, emission parameters may simply be entered into a table, or the relative peak intensity may be increased/decreased with toggles. Alternatively, a picture may be taken of a scene under a certain kind of illumination, and the tablet may analyze the spectra and adjust the output of endoscope <NUM> accordingly. Further, any computer system (not just a tablet) may be used to communicate with endoscope <NUM> either wirelessly, by wire, or other electronic communication method.

Also shown in <FIG> is a color checker (a series of squares with idealized colors) which, in some embodiments, may be a "Macbeth" color checker. The color checker includes colors that are meant to represent a range of colors seen in photographs. In one arrangement contemplated by the present disclosure, selecting a light emission mode may include determining the colors in a color checker under a desired illumination, and generating endoscopic spectral output to match the desired illumination mode. The color checker can be imaged under a reference illuminant (such as a blackbody at <NUM> °K), and then imaged again under a custom light source. The colors under the custom light source can be compared with the colors under the reference source to see how close the output of the custom source is to the reference. By doing this, endoscope <NUM> can simulate the desired custom illumination mode. In one arrangement, imaging the color checker may be accomplished with a camera in the tablet (or any other camera device such as a cell phone camera, computer camera, or the like). Alternatively, rather than using a color checker to set the desired spectral output, the endoscope operator could also set the emitted spectrum to enhance the color of a particular organ. This may make diagnosis and treatment easier. For example, a tumor may look different from healthy tissue under different types of light; the endoscope user could adjust the spectra to emit predominantly this diagnostic wavelength of light.

To perform the calculations discussed above, and determine the color of an object (or square in the color checker) the tablet or other computer must calculate the color of an object in XYZ space. The illuminance spectrum ("I(A)") first has to be multiplied by the color-specific reflectivity spectrum ("R(λ), G(λ), B(λ)") of the object. This spectrum is multiplied by the appropriate curve (x(λ) for the X value of the color, y(λ) for the Y value of the color, and z(λ) for the Z value of the color), and then integrated (see equations <NUM>, <NUM>, and <NUM>). <MAT> <MAT> <MAT>.

In the representation of color, there are two primary concepts: "colorfulness" (i.e., the amount of color) and "luminosity" (i.e., the brightness of the color). It takes two terms to represent the colorfulness and one term to represent the luminosity. "Colorfulness" may be determined by calculating u' and v' using X, Y, and Z (see equations <NUM> and <NUM>). <MAT>
<MAT>.

When comparing the color to a reference illuminant, we can calculate Δ(u'v') (see equation <NUM>).

Ideally Δ(u'v') ≤ <NUM>. In this range, the human eye has difficulty perceiving the difference between the colors. In other words, the optimization seeks to minimize the sum (or some other linear combination) of the difference between the color of a tile (or other color reference) under broadband normal illumination (e.g., blackbody illumination at <NUM> °K) and the color of that same tile under illumination from the set of lasers described here.

<FIG> illustrates method <NUM> of endoscopic illumination, in accordance with an embodiment of the disclosure. The order in which some or all of process blocks <NUM> - <NUM> appear in method <NUM> should not be deemed limiting. Rather, one of ordinary skill in the art having the benefit of the present disclosure will understand that some of method <NUM> may be executed in a variety of orders not illustrated, or even in parallel.

Block <NUM> shows selecting a light emission mode from a plurality of light emission modes. In one embodiment, the light emission mode is any one of the endoscopic emission spectrums corresponding to a blackbody emission spectrum depicted in <FIG>. In other embodiments, the user may select, trace, or input a custom emission spectrum (see e.g., <FIG>).

Block <NUM> illustrates emitting light from a plurality of light emitters in response to the light emission mode selected. In one embodiment, each light emitter in the plurality of light emitters emits a distinct bandwidth of the light. The bandwidth of light emitted by each light emitter in the plurality of light emitters is less than <NUM>. In other embodiments, the bandwidth may be appreciably smaller, such as <NUM> or less.

Block <NUM> depicts transporting the light through a fiber optic cable; a first end of the fiber optic cable is optically coupled to the plurality of light emitters. In some embodiments, using lasers as the light source provides for extremely efficient light coupling to the fiber optic cable (relative to other white light sources).

Block <NUM> shows out-coupling the light from a second end of the fiber optic cable, and the light output from the second end of the fiber optic cable mimics a continuous emission spectrum to the human eye. In one embodiment, the light output from the second end of the fiber optic cable mimics a blackbody emission spectrum by having a Δ(u'v') ≤ <NUM> from the blackbody emission spectrum, in a CIELUV color space.

The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention, which is defined by the appended claims, to the precise forms disclosed.

Claim 1:
A system (<NUM>) for medical diagnosis, comprising:
a fiber optic cable (<NUM>);
a plurality of light emitters (<NUM>), wherein the plurality of light emitters (<NUM>) are the only light emitters in the system that are optically coupled to a first end of the fiber optic cable; and
a controller (<NUM>) disposed in the system and electrically coupled to the plurality of light emitters, wherein the controller includes logic (<NUM>) that when executed by the controller causes the controller to perform operations including:
receiving instructions including an illumination mode of a plurality of illumination modes, wherein each illumination mode of the plurality of illumination modes mimics a blackbody emission spectrum to a human eye and corresponds to a different respective specific temperature of between <NUM>,<NUM> °K and <NUM>,<NUM> °K, inclusive; and
adjusting an intensity of the light emitted from each light emitter in the plurality of light emitters to match the illumination mode,
wherein each illumination mode includes a set of predefined intensities of the light for the plurality of light emitters to emit, and the set of predefined intensities mimics the corresponding blackbody emission spectrum;
characterised in that each light emitter in the plurality of light emitters (<NUM>) emits a distinct bandwidth of light of less than <NUM>, and in that each of the distinct bandwidths corresponds to a different photon energy.