Surgery – Endoscope – With camera or solid state imager
Reexamination Certificate
2002-04-26
2004-09-28
Leubecker, John P. (Department: 3739)
Surgery
Endoscope
With camera or solid state imager
C600S160000, C600S476000, C348S068000
Reexamination Certificate
active
06796938
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a image obtaining method and apparatus for an endoscope apparatus, and in particular to an image obtaining method and apparatus for an endoscope apparatus wherein a low-intensity fluorescent light image and a high-intensity standard image are received by use of the same photoelectrical converting element.
2. Description of the Related Art
Endoscope apparatuses for observing living tissues within a body cavity are widely known, and there are in wide use today electronic endoscope apparatuses wherein an illuminating light such as a white light or the like for observing living tissue is projected into a subject body cavity and an image of the living tissue illuminated thereby is obtained by use of a CCD element or the like, and this image is observed on a television screen. Further, the living tissue within the body cavity is not only illuminated by an illuminating light such as a white light or the like and observed: endoscope apparatuses that obtain a visible image formed based on a standardized fluorescent light intensity, which represents the ratio between the intensity of the fluorescent light near the wavelength range of 480 nm and the intensity of the fluorescent light in the wavelength range spanning from 430-730 nm emitted from the living tissue within the body cavity upon the irradiation thereof by an excitation light of a wavelength near 410 nm; or a visible image based on a fluorescent light yield ratio, which represents the ratio between the intensity of the fluorescent light emitted from the living tissue within the body cavity upon the irradiation thereof by the aforementioned excitation light and the intensity of the near infrared light reflected from the aforementioned living tissue upon the irradiation thereof by a near infrared light, which is a reference light, for use in diagnosing the tissue state of a target tissue have also been proposed. Note that the excitation light is readily absorbed by the living tissue, and because it is difficult to use the excitation light intensity received by the target tissue for measurement, near infrared light or a red light or the like, which is not readily absorbed by the living tissue, is employed as a reference light, and the excitation light intensity received by the living tissue is measured.
Because there is a large difference between the light intensity of a standard image formed of the high-intensity illuminating light that has been reflected from a living tissue that has been irradiated thereby and a fluorescent image formed of the low-intensity fluorescent light emitted from a living tissue upon the irradiation thereof by an excitation light, if, for example, these two images were to be time divided and obtained by the same image obtaining element, a dynamic range on the order of 90 dB (approximately 65000 gradations) would be required. However, the dynamic range of a currently available typical photoelectrical converting element is 60 dB (approximately 1000 gradations); therefore, an operation wherein, for example, a standard image only is passed through a light reducing filter and the light passing therethrough is received; and the standard image and the fluorescent image are both within a dynamic range below 60 dB and the light thereof is received; wherein the standard image and the fluorescent image received thereby are each photoelectrically converted and obtained as an analog signal, respectively, is performed. Then, these analog signals are converted to digital values after being amplified by a roughly fixed predetermined gain, and these digital values are used to form a visible image of the aforementioned living tissue and said visible image is observed, or the fluorescent light yield, the standardized fluorescent light intensity or the like is obtained and a visible image representing the tissue state of the aforementioned living tissue is formed and a diagnosis is carried out.
On the other hand, research and development of photoelectrical converting elements having a dynamic range of 90 db is also progressing, and if a photoelectric converting element having a dynamic range enlarged to this extent is employed, the standard image and the fluorescent image can be received by the same photoelectric converting element within the dynamic range thereof without the standard image having to first be passed through a light reducing filter or the like, and the light intensity of the standard image received by the photoelectric converting element becomes higher. In this manner, the ratio of photon noise generated in proportion to the square root of the received light intensity can be largely reduced, and because the S/N ratio of the standard image can be improved, it is desirable that a photoelectric converting element having an enlarged dynamic range such as this be utilized in an endoscope apparatus.
However, the analog signal obtained by a photoelectric converting element having a wide dynamic range such as this has a wide dynamic range, and the circuitry for processing said wide dynamic range analog signal, such as an A/D converting circuit, a computational circuit or the like, must also have the same wide dynamic range (such as 90 dB or 16 bits), and there is a problem in that it is difficult to construct such circuitry. That is to say, a circuit having a wide dynamic range such as this and the elements configuring said circuit are not common; they are extremely expensive; particularly in the case of disposing a photoelectric converting element having a wide dynamic range (e.g., 90 dB) in the distal end of an endoscope apparatus, in which signals are transmitted through a narrow tube, there is the fear of a problem due to noise becoming mixed in with the signal during transmission.
SUMMARY OF THE INVENTION
The present invention has been developed in consideration of the circumstances described above, and it is a primary objective of the present invention to provide an image obtaining method and apparatus for an endoscope apparatus, which are capable of converting a photoelectrically converted and outputted analog signal to a digital value having a narrower dynamic range, while suppressing the reduction of the gradations of said analog signal, whereby the mixing of noise with said digital value can be suppressed, and the cost of the apparatus can be reduced.
The image obtaining method of the endoscope apparatus according to the present invention comprises the steps of: irradiating a living tissue with an illuminating light and an excitation light, each of which is emitted at a mutually different timing; receiving, by use of the same photoelectric converting element, a fluorescent image formed of the fluorescent light emitted from the living tissue upon the irradiation thereof by the excitation light and a standard image formed of the reflected light reflected from the living tissue upon the irradiation thereof by the illuminating light; photoelectrically converting the standard image and the fluorescent image received thereby, to obtain each as respective analog signals; converting these analog signals to respective digital values; and outputting these digital values as an image signal; wherein, the analog signal representing the fluorescent image is converted to digital values after being amplified by a larger gain than the gain utilized in amplifying the analog signal representing the standard image.
The image obtaining apparatus of the endoscope apparatus according to the present invention comprises: an illuminating means for irradiating a living tissue with an illuminating light and an excitation light, each of which is emitted at a mutually different timing; a light receiving means for receiving a fluorescent image formed of the fluorescent light emitted from the living tissue upon the irradiation thereof by the excitation light, and a standard image formed of the reflected light reflected from the living tissue upon the irradiation thereof by the illuminating light, and photoelectrically converting the standa
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