Optical viewing instruments having fiber optic components are used in a broad variety of applications, especially in technical and medical environments where it is desirable to view areas or objects that are internal to physical structures or environments that are difficult to access visually. An example of such an application is an endoscope.
A typical endoscope comprises a cylindrical stainless steel case enclosing a bundle of optical fibers extending between a distal end (tip end) and proximal end of the endoscope for transmitting light through the endoscope. A fiber optic cable delivers light from a light source into the case through an aperture situated near the proximal end of the endoscope. The optical fibers transmit the light through to the distal end, where the light exits the endoscope and illuminates the area near the distal end. The endoscope in turn transmits an image of that area through a rod and lens system to an eyepiece lens at the proximal end. A video camera coupled to the eyepiece converts the image into electronic signals and transmits the signals to a video monitor, where the image is displayed.
Endoscopes are used most often in "minimally invasive surgery", in which an endoscope is inserted into a patient, allowing a surgeon to illuminate and view the interior of the patient with minimal penetration. The use of endoscopic surgery is growing, in large part because it is generally safer and less expensive than conventional surgery, and patients tend to require less time in a hospital after endoscopic surgery. Conservative industry experts estimate that about 4 million minimally invasive procedures were performed in 1996. As endoscopic surgery becomes more common, there is an increasing need to accurately evaluate the performance characteristics of endoscopes.
To obtain a true measure of the performance of an endoscope or similar optical instrument, both the lens and the optical fibers should be evaluated. For example, some optical fibers may be damaged and only partially transmit light. In addition, the lens may distort images or blur the sharpness of image colors. These and other shortcomings in the optical performance of endoscopes may be the result of imperfections in the manufacturing process and/or may develop as the endoscope is used over time.
Since endoscopes, or similar optical instruments have various different performance characteristics, several tests should be performed in order to evaluate these characteristics. Endoscopes are most often used in hospitals and other clinical environments, rather than in facilities having specialized endoscope testing capabilities, and therefore the tests performed on endoscopes should not be overly complicated, but rather should be capable of performance by the average clinical worker. Similarly, it would be preferable to perform and analyze the results of the tests completely within the clinical environment, without the need for input from experts in such fields as fiber optics or lens systems. Accordingly, an apparatus for evaluating the performance characteristics of endoscopes ideally would be simple to operate, and would automatically provide an evaluation of the performance characteristics of endoscopes without manual calculation or expert knowledge or analysis.
In addition, an apparatus for evaluating the performance characteristics of endoscopes or similar optical instruments ideally would be able to allow a user to practice performing the endoscope tests, and would provide corrective instructions when the user fails to perform a test correctly.
It would also be desirable for an automated apparatus to account for a variety of different factors when evaluating the results of an endoscope or optical instrument test. A set of test results may not be determinative of, for example, endoscope performance without having information on the endoscope that was tested, such as the endoscope diameter, length and tip angle. For example, the same test results may indicate that an endoscope is acceptable if the endoscope tested has a diameter of 10 millimeters, but that the endoscope is unacceptable if the endoscope tested has a diameter of 4 millimeters. Accordingly, such instrument-specific information would need to be assessed in order to accurately evaluate endoscope performance characteristics.
An apparatus for evaluating the performance characteristics of optical instruments would also be able to validate claims made by instrument vendors about the capabilities of their products. Accordingly, such an apparatus would be advantageous for the purchasers and users of such instruments. In addition, such an apparatus would be of great use in evaluating disposable instruments, such as endoscopes, which currently have an average life of about 20 to 30 uses. An apparatus for evaluating the performance characteristic of endoscopes or similar optical instruments would be able to determine when a disposable instrument is so degraded that it should be discarded.
Furthermore, an endoscope, for example, may be adequate for one surgical procedure but inadequate for another which requires more precision, such as when a patient is bleeding. Currently, an endoscope which is suspected of having any deficiency must be removed from service and sent for repair, which can be both costly and time consuming. An apparatus for evaluating the performance characteristics of endoscopes would preferably be able to identify endoscopes which are appropriate for one type of procedure although inadequate for another.
Such an apparatus would also be most advantageous in a program of preventative maintenance. Instruments such as endoscopes cost thousands of dollars, and typically require repairs at least about twice per year which can cost several thousand dollars per repair. There is a need for a tool for evaluating the performance characteristics of optical instruments, thereby verifying if repairs have been effective.
An apparatus for evaluating optical instrument performance ideally would also be able to store the results of past tests and evaluations, thereby allowing the system to evaluate changes in instrument performance after repair operations and over the lifetime of the instrument. In addition, such information on changes in instrument performance would be useful in predicting changes in the performance of other instruments before their performance degrades. This would help predict future instrument needs.
The present inventors are not aware of any commercially available tools for use in a clinical environment which quantitatively assess the performance characteristics of endoscopes or similar optical instruments, nor are they aware of any such tools that automatically generate graphical and alphanumerical indicia of the optical performance characteristics of such instruments.
Accordingly, it is an object of the present invention to provide such a method and apparatus for evaluating the optical performance characteristics of optical instruments having fiber optic components.