Surgery – Endoscope – Having imaging and illumination means
Reexamination Certificate
2002-05-29
2004-10-05
Leubecker, John P. (Department: 3739)
Surgery
Endoscope
Having imaging and illumination means
C600S109000, C600S178000, C600S181000, C600S476000
Reexamination Certificate
active
06800057
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an image obtaining apparatus for irradiating a target subject with an illuminating light and obtaining an optical image based on the re-radiated light re-radiated from said target subject upon the irradiation thereof by said illuminating light, and in particular to an image obtaining apparatus employing a charge multiplying type solid state image obtaining element to obtain images.
2. Description of the Related Art
There are known image obtaining apparatuses, which utilize a solid state image obtaining element such as a CCD or the like for converting an optical image to an electric signal, for obtaining an optical image of a target subject. In recent years, as described, for example, in Japanese Unexamined Patent Publication No. 7(1996)-176721, charge multiplying type solid state image obtaining elements for multiplying an obtained signal charge by a multiplication rate based on a multiplication rate control signal have been developed; wherein, by providing this charge multiplying type solid state image obtaining element, the image obtaining sensitivity of the image obtaining apparatus can be improved and controlled. That is to say, even if the light quantity of an optical image is insufficient to be obtained as an image utilizing a conventional image obtaining apparatus, if said optical image is obtained by use of this charge multiplying type solid state image obtaining element, said optical image can be displayed as a visible image; moreover, the image obtaining sensitivity can be controlled so as to match the image obtaining conditions. A charge multiplying type solid state image obtaining element provided with a charge multiplying means such as that described above is called a CMD (Charge Multiplying Detector) −CCD; wherein, conduction electrons and atoms are made to collide within a high-intensity electric field region, and the charge multiplication effect produced by this ionization serves to multiply the signal charge, whereby the image obtaining sensitivity can be improved.
According to a charge multiplying type solid state image obtaining element, because the charge multiplying means is a means for multiplying the signal charges which is situated in a series of signal processing means in the signal processing sequence as the means before a charge detecting circuit for converting the signal charges into sequential signal voltages and obtaining said voltages as an output signal, the charge multiplying means does not multiply the readout noise produced by the charge detecting circuit, the S/N ratio can be improved thereby. Accordingly, by using a charge multiplying type solid state image obtaining element, it becomes possible to improve the S/N ratio of the output signals of an imaging device that performs image obtainment under conditions in which there is insufficient light for an optical image. Further, because the signal charge multiplication rate can be changed by the multiplication rate control signal, it becomes possible to control the image obtaining sensitivity of an image obtaining apparatus provided with a charge multiplying type solid state image obtaining element.
Further, endoscope apparatuses employing a solid state image obtaining element are in wide use. By displaying the images obtained by a CCD on a monitor or the like, these endoscope apparatuses feature the advantage of being able to allow observation of the image by a plurality of people simultaneously. In addition, by subjecting an obtained image to various image processes before displaying said image, characteristics of the image can be enhanced and the image displayed on a monitor, making a great contribution to the advancement of medicine.
According to these endoscope apparatuses, making use of the fact that the intensity of the fluorescent light emitted from a normal tissue differs from the intensity of the fluorescent light emitted from a diseased tissue when a target subject (i.e., a living tissue) is irradiated by an excitation light having a predetermined wavelength, by detecting the fluorescent light emitted from a target subject upon irradiation thereof by an excitation light having a predetermined wavelength, the location and range of penetration of a diseased tissue is displayed as a fluorescence image, and the tissue state of a diseased portion is determined. However, because there is unevenness on the surface of a target subject, the distance between the light emitting system for emitting the excitation light and the target subject is not uniform; therefore, the intensity of the excitation light irradiating the target subject is generally not of a uniform intensity. Further, although the intensity of the fluorescent-light emitted from the target subject is substantially proportional to the intensity of the excitation light, the intensity of the aforementioned excitation light becomes weaker in inverse proportion to the square of the distance between the excitation light and the target subject. Therefore, there are cases in which the fluorescent light emitted from a diseased tissue located at a position closer to the excitation light source than a normal tissue is of a higher intensity than the fluorescent light emitted from aforementioned normal tissue. Under such conditions, if an observer of an image obtained by the use of the above-described apparatus makes a determination as to the tissue state of the target subject based solely on the data relating to the intensity of the fluorescent light received from the target subject upon the irradiation thereof with an excitation light, there will be cases in which a false determination of the tissue state of the target subject will be made.
In order to mitigate the negative effects of the problems described above, there has been described an image display apparatus in Japanese Unexamined Patent Publication No. 9(1997)-308604, wherein: two types of fluorescence images, e.g., a narrow band fluorescence image having a wavelength near 480 nm, in which the difference in the intensity of the fluorescent light emitted from a normal tissue and the intensity of the fluorescent light emitted from a diseased tissue is large, and a wide band fluorescence image formed of light having wavelengths within the visible spectra of 430-730 nm, for example, are obtained; the ratio of the intensity of the narrow band fluorescence image and the wide band fluorescence image is obtained; and a pseudo color image is displayed based on this ratio. By obtaining the ratio described above, because the factor of the dependency of the intensity of the fluorescent light on the distance between the excitation light source and the fluorescent light receiving portion, and the target subject is cancelled, it is possible to form an image in which only the difference in the spectral form of the fluorescent light is reflected.
On the other hand, the miniaturization of the diameter of the endoscope has seen progress in recent years, and whereas in the past endoscopes were limited to being employed to examine the intestinal tract, currently, endoscopes are employed to examine the respiratory tract, the otorhinolaryngological cavity and passages, and the joints. However, because the number of light guiding fibers for transmitting the illuminating light becomes limited in accordance with the miniaturization of the endoscope, there are cases for which it is not possible to emit sufficient illuminating light; therefore, there is a demand for the development of an image obtaining apparatus capable of obtaining images at a desired image obtaining sensitivity. Further, fluorescence image observation of the fluorescence image obtained of the fluorescent light emitted from a target subject upon the irradiation thereof by an excitation light is also performed. Because the fluorescent light emitted from a target subject upon the irradiation thereof by an excitation light is extremely faint, there are cases in which the obtainment thereof as an image is impossible with current apparatuses;
Nakajima Yukihiko
Tsujita Kazuhiro
Fuji Photo Film Co. , Ltd.
Leubecker John P.
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