An endoscope apparatus includes an excitation-light radiation unit; a fluorescence-image acquisition unit; a fluorescence-spectrum storage unit; a density computation unit, an image combining portion; and an image display portion; wherein when coefficients at wavelengths of fluorescent components obtained from the fluorescence spectra in the storage unit, and when intensities of fluorescence images at the wavelengths acquired by the acquisition unit, the density computation unit calculates the densities of the fluorescent components from an equation, and when the densities are calculated, in accordance with a change in the value of an exposure condition item during acquisition of the fluorescence image at a wavelength, the density computation unit changes the coefficients at the wavelength using the ratio of the value after the change to the value of the exposure condition items under the reference exposure conditions has been made.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluorescence-endoscope apparatus that acquires a plurality of types of images of fluorescence generated by biological tissue containing a plurality of types of fluorescent components, whose maximum-fluorescence wavelengths are different and whose fluorescence wavelengths overlap in at least parts of the wavelength ranges, and that separately displays the plurality of types of fluorescent components present in the biological tissue using the acquired fluorescence images.

2. Description of Related Art

In molecular imaging diagnosis using fluorescence-endoscope apparatuses, it is effective to perform fluorescence-extraction processing using a so-called UNMIXING technique that removes autofluorescence noise originating from biological subjects (tissue, residues, and so forth), to extract fluorescence coming from fluorescent probes. In order to improve the image quality S/N of the fluorescence image with low light intensity in the fluorescence-extraction processing using the UNMIXING technique, it is effective to allow the exposure time to be changed arbitrarily via a spectral image-acquisition unit provided with an etalon-type tunable light-dispersing element and a sensitive camera, for example.

Conventional fluorescence-endoscope apparatuses using the UNMIXING technique include, for example, the endoscope apparatus described in the following Publication of Japanese Patent No. 2008-43396.

In fluorescence-endoscope apparatuses that capture spectral images of a plurality of types of fluorescence, the longer the exposure time used, the lower the frame rate becomes.

The brightness of each fluorescent component (human tissue, residue, or fluorescence agent) present in the biological tissue of an observation target is not uniform.

Thus, for example, when a darker fluorescent component is present in the biological tissue, it is necessary to increase the exposure time so that the brightness of the fluorescence image of the darker fluorescent component is suitable for observation. However, if the exposure time for the fluorescence images of other fluorescent components present in the biological tissue is increased in a similar manner in accordance with the change made in the exposure time for the fluorescence image of the darker fluorescent component, the frame rate is greatly reduced. When the other fluorescent components present in the biological tissue are excessively bright and if the exposure time is increased further, the brightnesses of the fluorescence images of the excessively-brighter fluorescent components are saturated.

For example, when an excessively bright fluorescent component is present in the biological tissue, it is necessary to reduce the exposure time such that the brightness of the image of the excessively bright fluorescent component is suitable for observation. However, if the exposure time for the fluorescence images of the other fluorescent components present in the biological tissue is reduced in a similar manner in accordance with the change made in the exposure time for the fluorescence image of the excessively bright fluorescent component and if, for example, the other fluorescent components are darker, the fluorescence images of the darker fluorescent components become too dark to be detected.

Therefore, in fluorescence-extraction processing using the UNMIXING technique in the endoscope apparatus described in Publication of Japanese Patent No. 2008-43396, constant UNMIXING coefficients (component ratios of the fluorescent components) are used regardless of the exposure conditions, such as the exposure time etc. Thus, when the fluorescence image is detected by adjusting the exposure conditions, such as the exposure time etc., so that a suitable brightness is achieved for each fluorescence wavelength, the UNMIXING coefficients become unsuitable, and it is sometimes difficult to separate the fluorescent components suitably.

The fluorescence-endoscope apparatus using the conventional UNMIXING technique will be described with reference to an example where a sample containing three types of fluorescent components having different fluorescence wavelengths is subjected to spectroscopy.

FIGS. 15A and 15Bare diagrams for explaining three types of fluorescent components1to3present in a sample, whereFIG. 15Ais a diagram conceptually showing the distribution of the fluorescent components1to3in the sample, andFIG. 15Bis a diagram showing fluorescence spectra of the fluorescent components1to3.FIGS. 16A to 16Care explanatory diagrams conceptually showing the distributions and brightnesses of spectral images acquired by an image acquisition apparatus through a tunable light-dispersing element, such as an etalon etc., in a fluorescence-endoscope apparatus, whereFIG. 16Ais a diagram showing a spectral image of the fluorescent component1at the maximum-fluorescence wavelength λ1,FIG. 16Bis a diagram showing a spectral image of the fluorescent component2at the maximum-fluorescence wavelength λ2, andFIG. 16Cis a diagram showing a spectral image of the fluorescent component3at the maximum-fluorescence wavelength λ3. Iall(λ1), Iall(λ2), and Iall(λ3) are signal intensities that are detected at an arbitrary common pixel Pi in each of the spectral images shown inFIGS. 16A to 16C.FIGS. 17A to 17Care diagrams showing example exposure timings for spectral images of the individual fluorescent components1to3at the maximum-fluorescence wavelengths λ1to λ3, whereFIG. 17Ais a diagram showing transmission-switching timings of the maximum-fluorescence wavelengths λ1to λ3of the three types of fluorescent components1to3by a tunable light-dispersing element,FIG. 17Bis a diagram showing image-acquisition timings of the fluorescence wavelengths λ1to λ3that are acquired by an image acquisition apparatus, andFIG. 17Cis a diagram showing an example of a matrix equation for calculating densities D1to D3of the fluorescent components1to3using the conventional UNMIXING technique in a spectral image in which fluorescence signals generated by the fluorescent components1to3coexist. InFIGS. 17A to 17C, tλ1to tλ3are exposure times at which the individual fluorescence wavelengths λ1to λ3are spectrally separated through a tunable light-dispersing element etc., and M1to M3are memories that store the data of the respective fluorescence wavelengths λ1to λ3, which have been spectrally separated through the tunable light-dispersing element etc., acquired by individual image acquisition apparatuses.

Image acquisition using the image acquisition apparatus is performed on a sample, serving as a target, in which, as shown inFIG. 15B, the fluorescent component1having the maximum-fluorescence wavelength at the wavelength λ1, the fluorescent component2having the maximum-fluorescence wavelength at the wavelength λ2, and the fluorescent component3having the maximum-fluorescence wavelength at the wavelength λ3are individually distributed in the locations shown in FIG.15A, by transmitting the fluorescence wavelengths λ1to λ3generated by the individual fluorescent components1to3through the tunable light-dispersing element in a time-division manner.

At this time, as shown inFIGS. 16A to 16C, although the intensities of the fluorescence signals from the individual fluorescent components1to3are different, the spectral images at the individual fluorescence wavelengths are images that contain the fluorescence signals generated by the three types of fluorescent components in a mixed manner. In other words, in these spectral images, fluorescence signals emitted from the fluorescent components1to3are not separated.

Here, it is assumed that fluorescence-extraction processing using the conventional UNMIXING technique described in Publication of Japanese Patent No. 2008-43396 is performed on a spectral image containing the fluorescence signals from the fluorescent components1to3in a mixed manner.

In the fluorescence-extraction processing using the conventional UNMIXING technique, the UNMIXING coefficients (the component ratios of the fluorescent components) of the fluorescence spectra of the three types of fluorescent components1to3present in the sample at the individual normalized densities are stored in advance in a predetermined storage medium.

Then, the UNMIXING coefficients (the component ratios of the fluorescent components) of the fluorescence spectra of the fluorescent components1to3at the individual normarized densities stored in the predetermined storage medium and the intensities Iall(λ1) to Iall(λ3) in the fluorescence images at the individual fluorescence wavelengths λ1to λ3that are detected are used to calculate the densities D1to D3of the fluorescent components1to3based on the matrix equation shown inFIG. 17C.

In this way, in the fluorescence-endoscope apparatus using the conventional UNMIXING technique, it is possible to obtain distribution images of the individual fluorescent components by performing UNMIXING on the spectral images using the spectra of the individual fluorescent components.

FIGS. 18A to 18Gare diagrams showing image processing after the UNMIXING processing, whereFIG. 18Ais a distribution image of the fluorescent component1after the UNMIXING processing,FIG. 18Bis a diagram showing a state in which a predetermined color is assigned to a distributed region of the fluorescent component1in the distribution image inFIG. 18A,FIG. 18Cis a distribution image of the fluorescent component2after the UNMIXING processing,FIG. 18Dis a diagram showing a state in which a predetermined color is assigned to a distributed region of the fluorescent component2in the distribution image inFIG. 18C,FIG. 18Eis a distribution image of the fluorescent component3after the UNMIXING processing,FIG. 18Fis a diagram showing a state in which a predetermined color is assigned to a distributed region of the fluorescent component3in the distribution image inFIG. 18E, andFIG. 18Gis a diagram showing a state in which the distribution images shown inFIGS. 18B,18D, and18F are combined into one image.

In accordance with the brightnesses of the individual fluorescent components; their tendency to accumulate in a biological subject, serving as a sample; their transportability to a lesion, serving as a sample; metabolic properties in a biological subject (such as time); time (assessment time) and timing before performing measurement after introducing a fluorophor into the biological subject; and so forth, the fluorescence intensities (brightnesses) at the maximum-fluorescence wavelength are different for every fluorescent component in the sample.

For example, even with the fluorescent components1to3having the fluorescence spectral properties shown inFIG. 19A, as shown inFIG. 19B, the fluorescence intensity of the fluorescent component2at the maximum-fluorescence wavelength λ2may be different.

In such a case, it is difficult to detect a darker fluorescent component if changing the exposure conditions, including the exposure time etc., such as increasing the exposure time for the fluorescence image of the fluorescent component2inFIGS. 19A and 19B, is not performed properly. Because the intensity detected from the darker fluorescent component2at the fluorescence wavelength λ2is weak, the detected signal tends to be affected by noise, and it is difficult to obtain the correct density even when the UNMIXING processing is performed.

However, for example, if the exposure time is evenly increased for the fluorescence images of all fluorescent components at the maximum-fluorescence wavelength in accordance with a suitable adjustment of the exposure time for the fluorescent component that is dark at the maximum-fluorescence wavelength, the frame rate is considerably reduced.

For the fluorescent component that is dark at the maximum-fluorescence wavelength, if only the exposure time for the fluorescence image at the maximum-fluorescence wavelength is increased, then the detection level of the fluorescence wavelengths of the other fluorescent components contained in the image varies, and a divergence from the UNMIXING coefficients (the component ratios of the fluorescent components) occurs, making separation of the fluorescent components difficult.

For example, in contrast to the situation shown inFIGS. 19A and 19B, in the case where the fluorescent component2is excessively bright at the maximum-fluorescence wavelength, the brightness of the image of the fluorescent component2is saturated if changing the exposure conditions, including the exposure time etc., such as reducing the exposure time for the fluorescence image of the fluorescent component2, is not performed properly.

However, for example, if the exposure time is evenly decreased for the fluorescence images of all fluorescent components at the maximum-fluorescence wavelength in accordance with a suitable adjustment of the exposure time for the fluorescent component that is bright at the maximum-fluorescence wavelength, then the fluorescence images of the other fluorescent components at the maximum-fluorescence wavelength become darker, making it difficult to detect the darker fluorescent components, or the detected signal tends to be affected by noise, making it difficult to obtain the correct densities even if the UNMIXING processing is performed.

If only the exposure time for the fluorescence image at the maximum-fluorescence wavelength of the fluorescent component that is excessively-bright at the maximum-fluorescence wavelength is reduced, then the detection level of the fluorescence wavelengths of the other fluorescent components present in the image varies, and a divergence from the UNMIXING coefficients (the component ratios of the fluorescent components) occurs, making separation of the fluorescent components difficult.

As shown inFIG. 22B, when only the exposure time for the fluorescence image at the fluorescence wavelength λ2shown inFIG. 21Bis increased, not only the fluorescent component2, but also the other components, such as the fluorescent component1and the fluorescent component3, are detected at high brightness.

In such a case, even if the UNMIXING processing is performed on the acquired spectral images, the component ratios of the actual fluorescent components become different from the UNMIXING coefficients that have been stored in a memory etc. in advance. Therefore, even if the densities D1to D3of the fluorescent components1to3are obtained using the matrix equation shown inFIG. 17C, to which matrix equation (13) above has been applied, as shown inFIGS. 23B to 23D, it is difficult to acquire distribution images that are separated into the individual fluorescent components.

A fluorescence-endoscope apparatus of one aspect of the present invention is a fluorescence-endoscope apparatus that radiates excitation light onto biological tissue containing a plurality of types of fluorescent components, whose maximum-fluorescence wavelengths are different and whose fluorescence wavelengths overlap in at least parts of the wavelength ranges, that acquires a plurality of types of images of fluorescence generated by the biological tissue, and that displays, in a separated manner, the plurality of types of fluorescent components present in the biological tissue using the acquired fluorescence images, comprising: a light source portion that emits at least one type of excitation light that excites the plurality of types of fluorescent components; a fluorescence image capturing unit that acquires the images of fluorescence generated by the biological tissue for every n types [where, m≦n] of wavelengths λ1to wavelength λn; a fluorescence-spectrum storage unit that records fluorescence spectra of m types [where, 2≦m] of individual fluorescent component1to fluorescent component m present in the biological tissue at normalized densities under reference exposure conditions; a fluorescent-component-density computation unit that obtains densities of the individual fluorescent components present in the biological tissue for all pixels in the fluorescence images by performing computation using the fluorescence spectra at the individual normalized densities of the fluorescent component1to fluorescent component m under the reference exposure conditions that are stored in the fluorescence-spectrum storage unit and the fluorescence images for every wavelength λ1to wavelength λn acquired by the fluorescence image capturing unit; a fluorescence-image combining portion that forms distribution images of the individual fluorescent components on the basis of the density of the individual fluorescent components obtained by the fluorescent-component-density computation unit, assigns predetermined colors corresponding to the individual fluorescent components to the formed distribution images of the individual fluorescent components, and combines the distribution images to which the predetermined colors are assigned into one image; and an image display portion that displays the image that has been combined by the fluorescence-image combining portion, wherein, when a1(λ1) to a1(λn) to am(λ1) to am(λn) are defined as coefficients at the wavelength λ1to wavelength λn of the fluorescent component1to fluorescent component m at the individual normalized densities under the reference exposure conditions, which are obtained from the fluorescence spectra, stored in the fluorescence-spectrum storage unit, of the fluorescent component1to fluorescent component m at the individual normalized densities under the reference exposure conditions, Iall(λ1) to Iall(λn) are defined as intensities of the fluorescence images at the wavelength λ1to wavelength λn acquired by the fluorescence image capturing unit, and D1to Dm are defined as the densities of the fluorescent component1to fluorescent component m, the fluorescent-component-density computation unit calculates, for all pixels, the density D1of the fluorescent component1to the density Dm of the fluorescent component m in each pixel in the fluorescence images using Equation (1) below, and wherein the fluorescent-component-density computation unit: checks if the reference exposure conditions of an exposure condition item have been changed; and if a value of a predetermined exposure condition item has been changed when the fluorescence image at least one wavelength λx among the wavelength λ1to wavelength λn is acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), changes the coefficients a1(λx) to am(λx) at the wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions using the ratio of the value of the changed predetermined exposure condition item to the value of the predetermined exposure condition item under the reference exposure conditions when the fluorescence image at the wavelength λx is acquired by the fluorescence image capturing unit:

In the above-mentioned fluorescence-endoscope apparatus, if the exposure time has been changed when the fluorescence image at the predetermined wavelength λx among the wavelength λ1to wavelength λn is acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λx) to am(λx) at the predetermined wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratio of the changed exposure time to the exposure time under the reference exposure conditions when the fluorescence image at the predetermined wavelength λx is acquired by the fluorescence image capturing unit.

In the above-mentioned fluorescence-endoscope apparatus, if the exposure times have been changed while keeping the frame rate constant when the fluorescence images at the individual wavelengths of the wavelength λ1to wavelength λn are acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λ1) to am(λ1) to a1(λn) to am(λn) at individual wavelengths among the wavelength λ1to wavelength λn of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratio of the changed exposure time to the exposure time under the reference exposure conditions when the fluorescence images at the individual wavelengths of the wavelength λ1to wavelength λn are acquired by the fluorescence image capturing unit.

In the above-mentioned fluorescence-endoscope apparatus, if the intensity of the excitation light that excites the predetermined wavelength λx has been changed when the fluorescence image at the predetermined wavelength λx among the wavelength λ1to wavelength λn is acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λx) to am(λx) at the wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratio of the changed intensity of the excitation light that excites the predetermined wavelength λx to the intensity of the excitation light that excites the predetermined wavelength λx under the reference exposure conditions when the fluorescence image at the predetermined wavelength λx is acquired by the fluorescence image capturing unit.

In the above-mentioned fluorescence-endoscope apparatus, if the intensities of the excitation light beams that excite the individual wavelengths have been changed when the fluorescence images at the individual wavelengths of the wavelength λ1to wavelength λn are acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λ1) to am(λ1) to a1(λn) to am(λn) at individual wavelengths among the wavelengths λ1to λn of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratios of the changed intensities of the excitation light beams that excite the individual wavelengths to the intensities of the excitation light beams that excite the individual wavelengths under the reference exposure conditions when the fluorescence images at the individual wavelengths of the wavelength λ1to wavelength λn are acquired by the fluorescence image capturing unit.

In the above-mentioned fluorescence-endoscope apparatus, if the excitation time of the excitation light that excites the predetermined wavelength λx has been changed when the fluorescence image at predetermined wavelength λx among the wavelength λ1to wavelength λn is acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λx) to am(λx) at the wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratio of the changed excitation time of the excitation light that excites the predetermined wavelength λx to the excitation time of the excitation light that excites the predetermined wavelength λx under the reference exposure conditions when the fluorescence image at the predetermined wavelength λx is acquired by the fluorescence image capturing unit.

In the above-mentioned fluorescence-endoscope apparatus, if the intensity and the excitation time of the excitation light that excites the predetermined wavelength λx have been changed when the fluorescence image at predetermined wavelength λx among the wavelength λ1to wavelength λn is acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λx) to am(λx) at the wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratios of the changed intensity and the changed excitation time of the excitation light that excites the predetermined wavelength λx to the intensity and the excitation time of the excitation light that excites the predetermined wavelength λx under the reference exposure conditions when the fluorescence image at the predetermined wavelength λx is acquired by the fluorescence image capturing unit.

In the above-mentioned fluorescence-endoscope apparatus, if a detection intensity has been changed when the fluorescence image at the predetermined wavelength λx among the wavelength λ1to wavelength λn is acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λx) to am(λx) at the predetermined wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratio of the changed detection intensity to the detection intensity under the reference exposure conditions when the fluorescence image at the predetermined wavelength λx is acquired by the fluorescence image capturing unit.

In the above-mentioned fluorescence-endoscope apparatus, if a gain has been changed when the fluorescence image at the predetermined wavelength λx among the wavelength λ1to wavelength λn is acquired by the fluorescence image capturing unit, in accordance with the change, when the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), the fluorescent-component-density computation unit may multiply the coefficients a1(λx) to am(λx) at the predetermined wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratio of the changed gain to the gain under the reference exposure conditions when the fluorescence image at the predetermined wavelength λx is acquired by the fluorescence image capturing unit.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a block diagram showing, in outline, a configuration that is common to fluorescence-endoscope apparatuses of individual examples of the present invention.FIG. 2is an explanatory diagram showing the configuration of an image acquisition portion in the fluorescence-endoscope apparatus shown inFIG. 1.

The fluorescence-endoscope apparatus inFIG. 1includes a light source unit11, an endoscope-tip inserted portion12, a control unit13, a display unit14, and an exposure-conditions setting unit15.

The light source unit11includes an excitation-light light source11aand a light-source control circuit11b.

The excitation-light light source11aincludes a light source (not shown) and a plurality of types of excitation filters (not shown) for respectively exciting a plurality of types of fluorescent components or a single excitation filter (not shown) for simultaneously exciting a plurality of types of fluorescent components, and the excitation-light light source11ais configured to emit light having a predetermined excitation wavelength range.

The light-source control circuit11bis configured so as to be able to perform, on the basis of values of the excitation time and excitation intensity that are set by the exposure-conditions setting unit15, selective switching control of the intensities and the emission time of the excitation light that corresponds to a plurality of types of fluorescent components from the excitation-light light source11aand that is emitted from the light source unit11by, for example, rotating a turret that is provided with the excitation filters and transparent glass plates on the circumference thereof or through, for example, a tunable light-dispersing element, such as an etalon etc.

The endoscope-tip inserted portion12includes an illumination optical system12aand an image acquisition portion12b.

The illumination optical system12aradiates the light from the light source unit11through a light guide12conto biological tissue9.

The excitation-light light source11a, the light guide12c, and the illumination optical system12ain the light source unit11cooperatively function as a light source portion that radiates, onto an observed site on the biological subject9, at least one type of excitation light that excites a plurality of types of fluorescent components having different fluorescence-wavelength characteristics.

As shown inFIG. 2, the image acquisition portion12bincludes an objective optical system12b1, an image-forming optical system12b2, an excitation-light cut filter12b3, a tunable light-dispersing element12b4, and an image acquisition device12b5.

The excitation-light cut filter12b3has the optical property that it cuts light in a predetermined excitation wavelength range and transmits light in other wavelength ranges.

The tunable light-dispersing element12b4is formed of an etalon etc. The etalon is provided with a pair of optical substrates12b41and12b42, electrostatic capacitance sensors12b43and12b44that measure the inter-surface distance between the surfaces of the pair of optical substrates12b41and12b42facing each other, and, as an actuator for moving one substrate12b41, a piezoelectric device12b45which is driven under the control of a tunable-light-dispersing-element control unit circuit13a, which will be described later. With such a configuration, under the control performed by the tunable-light-dispersing-element control circuit13a, which will be described later, the tunable light-dispersing element12b4selects fluorescence in a plurality of predetermined wavelength ranges from the light incident thereon from an observed site on the biological subject9and allows it to pass through in a time-division manner.

The image acquisition device12b5is, for example, constructed of a monochrome CCD formed of a single-chip image sensor and photoelectrically converts the light that has been selected and transmitted by a light-dispersing optical element12b4. The photoelectrically converted image is stored in frame memories13c1to13c3that are provided in the control unit13, which will be described later.

The image acquisition portion12bfunctions as a fluorescence image capturing unit that acquires images of fluorescence that are generated by the biological tissue for each of n types [where, m≦n] of wavelength λ1to wavelength λn.

The control unit13includes the tunable-light-dispersing-element control circuit13a, an image-acquisition-device control circuit13b, a frame memory13c, and an image processing circuit13d.

The tunable-light-dispersing-element control circuit13acontrols driving of the tunable light-dispersing element12b4on the basis of values of the exposure time set by the exposure-conditions setting unit15.

The frame memory13cincludes the frame memories13c1,13c2, and13c3for spectral images.

The frame memories13c1,13c2, and13c3for the spectral images individually store images of the light in the fluorescence-detecting wavelength range that has been selected by and transmitted through the tunable light-dispersing element12b4and photoelectrically converted via the image acquisition device12b5.

The image-acquisition-device control circuit13bcontrols driving of the image acquisition device12b5on the basis of values of the exposure time that are set by the exposure-conditions setting unit15, the value of the signal gain of the detection wavelength acquired by the image acquisition device, and so forth.

The image processing circuit13dincludes an UNMIXING coefficient storage unit13d1, a fluorescent-component-density computation unit13d2, and a fluorescence-image combining portion13d3.

The UNMIXING coefficient storage unit13d1stores fluorescence spectra of m types [where, 2≦m] of fluorescent component1to fluorescent component m present in the biological tissue9at their individual normalized densities under the reference exposure conditions and functions as a fluorescence-spectrum storage unit.

The fluorescent-component-density computation unit13d2obtains densities of the individual fluorescent components present in the biological tissue9for all pixels in the fluorescence images by performing computation using the fluorescence spectra of the individual fluorescent components1to fluorescent component m at the normalized densities under the reference exposure conditions that are stored in the UNMIXING coefficient storage unit13d1and the fluorescence images for every wavelength λ1to wavelength λn that are acquired by the image acquisition portion12b.

During the computation, the fluorescent-component-density computation unit13d2checks if the reference exposure conditions in the exposure condition items set by the exposure-conditions setting unit15have been changed; and if there has been a change in values of the predetermined exposure condition items during acquisition of the fluorescence image at least one wavelength λx among the wavelength λ1to wavelength λn by the image acquisition portion12b, in accordance with this change, upon calculating a density D1of the fluorescent component1to a density Dm of the fluorescent component m using Equation (1), which will be described below, changes the coefficients a1(λx) to am(λx) at the wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions using a ratio of the values of the predetermined exposure condition items that have been changed to the values of the predetermined exposure condition items under the reference exposure conditions when the fluorescence image at the wavelength λx is acquired by the image acquisition portion12b.

The exposure condition items in the present invention refer to various items that can be set by an operator in the fluorescence-endoscope apparatus, such as, for example, the exposure time, the excitation intensity, the excitation time, the signal gain at the detection wavelength acquired by the image acquisition device, the detection intensity, adjusted by an ND filter, at the detection wavelength, and so forth.

The exposure-conditions setting unit15is configured such that the values of these exposure condition items can be set and entered. Among the exposure conditions that have been set and entered, the exposure-conditions setting unit15transmits the values of the excitation time and the excitation intensity to the light-source control circuit11bin the light source unit11. The exposure-conditions setting unit15transmits the values of the exposure time that have been set and entered to the tunable-light-dispersing-element control circuit13aand the image-acquisition-device control circuit13bin the control unit13. The exposure-conditions setting unit15transmits the values of the set and entered signal gain at the detection wavelength acquired by the image acquisition device to the image-acquisition-device control circuit13bin the control unit13. The exposure-conditions setting unit15transmits the values of these exposure condition items that have been set and entered to the fluorescent-component-density computation unit13d2of the image processing circuit13din the control unit13.

The exposure-conditions setting unit15can be a device through which values can be input via a display similar to that of a personal computer etc. or can be a switch through which an operator can directly change the settings in the light source unit11, the image-acquisition unit12, and so forth.

The fluorescence-image combining portion13d3creates the distribution images of the individual fluorescent components on the basis of the densities of the individual fluorescent components obtained by the fluorescent-component-density computation unit13d2; assigns predetermined colors, such as, for example, R, G, B, and so forth corresponding to the individual fluorescent components, to the created distribution images of the individual fluorescent components; and combines the distribution images to which the predetermined colors have been assigned into one image. At this time, the individual image signals are converted into output signals of different colors such that the portions in which the individual fluorescent components are distributed, such as, for example, a normal tissue portion, a lesion tissue portion, and so forth, can easily be identified.

The display unit14functions as an image display portion and displays the image that has been combined through the fluorescence-image combining portion13d3.

The image acquisition device12b5can be formed of a color CCD that is provided with, for example, a mosaic filter (not shown) and a single-chip image sensor (not shown).

The single-chip image sensor can be configured such that the pixels each correspond to respective filters that form a mosaic filter and that transmit the light in the individual wavelength ranges, and such that the light of the image separated by the mosaic filter is acquired separately at different pixels.

In this case, the frame memories13c1,13c2, and13c3for the spectral images can be configured such that the individual memories correspond to the individual filters that form the mosaic filter and that transmit the light in the individual wavelength ranges, and such that individual image signals that have been separated through the mosaic filter and acquired at the corresponding individual pixels are stored separately therein.

A procedure for separating the fluorescent components using an UNMIXING technique in the fluorescent-component-density computation unit13d2will be explained below.

A method for computing the densities D of the individual fluorescent components in the UNMIXING will be described first.

As described above, a signal intensity Iall(λn) of the measurement target at the wavelength λn is defined as the sum of the signal intensities of the individual fluorescent components at the wavelength λn and can be expressed as in Equation (11) below:
Iall(λn)=I1(λn)+I2(λn) . . . +Im(λn)  (11)
where I1is the signal intensity obtained from the fluorescent component1at the wavelength λn,12is the signal intensity obtained from the fluorescent component2at the wavelength λn, and Im is the signal intensity obtained from the fluorescent component m at the wavelength λn.

The signal intensity obtained from the fluorescent component is proportional to the density of the fluorescent component. Therefore, when m types of fluorescent components are present in the measurement target, the signal intensities obtained from the individual fluorescent components at the wavelength λn can be expressed as in Equations (12a) to (12c) below:
I1(λn)=a1(λn)*D1  (12a)
where D1is the density of the fluorescent component1, and a1(λn) is the coefficient at the wavelength λn of the fluorescent component1at the normalized density under the reference exposure conditions;
I2(λn)=a2(λn)*D2  (12b)
where D2is the density of the fluorescent component2, and a2(λn) is the coefficient at the wavelength λn of the fluorescent component2at the normalized density under the reference exposure conditions; and
Im(λn)=am(λn)*Dm(12c)
where Dm is the density of the fluorescent component m, and am(λn) is the coefficient at the wavelength λn of the fluorescent component m at the normalized density under the reference exposure conditions.

In accordance with these Equations (12a) to (12c), when m types of fluorescent components are assumed to be present in the measurement target, the signal intensities of the measurement target at n types of wavelength λ1to wavelength λn can be expressed by, for example, matrix equation (13) below:

Here, the left-hand side in the matrix equation (13):

(Iall⁡(λ⁢⁢1)Iall⁡(λ⁢⁢2)⋮Iall⁡(λ⁢⁢n))[Expression⁢⁢7]
represents the spectra of the measurement target.

The right-hand side in the matrix equation (13):

Here, regarding the exposure conditions during acquisition of the individual fluorescence images at the fluorescence wavelength λ1to fluorescence wavelength λn by the image acquisition portion12b, if there is no change in the values of all exposure condition items compared with the values of the exposure condition items under the reference exposure conditions, the fluorescent-component-density computation unit13d2obtains the densities D1, D2, . . . , and Dm of the individual fluorescent components by solving matrix equation (1) below:

In the above matrix equation, if the number of types of spectral images and the number of types of fluorescent components are the same (in other words, n=m), because the number of equations and the number of different values of the densities of the fluorescent components become the same, it is possible to solve the matrix equation uniquely. If the number of types of spectral images is greater than the number of types of fluorescent components (in other words, n>m), even though the number of equations becomes greater than the number of different values of the densities of the fluorescent components, it is possible to solve the matrix equation by using a least squares method in this case. In contrast, if the number of types of spectral images is less than the number of types of fluorescent components (in other words, n<m), because the number of equations is less than the number of different values of the densities of the fluorescent components, it is not possible to solve the matrix equation.

Therefore, in the UNMIXING procedure, it is assumed that the number of types of spectral images is greater than or equal to the number of types of fluorescent components (in other words, n≧m).

On the other hand, regarding the exposure conditions during acquisition of the individual fluorescence images at the fluorescence wavelengths λ1to fluorescence wavelength λn by the image acquisition portion12b, if there is a change in the values of any exposure condition items constituting the exposure conditions for the fluorescence images at least one wavelength λx compared with the values of the exposure condition items under the reference exposure conditions, upon calculating a density D1of the fluorescent component1to a density Dm of the fluorescent component m using Equation (1), the fluorescent-component-density computation unit13d2changes the coefficients a1(λx) to am(λx) at the wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions using the ratio of the values of predetermined exposure condition items that have been changed to the values of the predetermined exposure condition items under the reference exposure conditions when the fluorescence image at the wavelength λx is acquired by the image acquisition portion12b.

For example, if there is a change in the exposure time for the fluorescence image at the fluorescence wavelength λ2compared with the exposure time under the reference exposure conditions, when α2is defined as the ratio of the changed exposure time, the UNMINXING coefficient in Equation (1) above is corrected as in Equation (1′) below:

Next, by solving Equation (1′) above that has corrected the UNMIXING coefficients, the densities D1, D2, . . . , and Dm of the individual fluorescent components are obtained.

Next, effects and advantages afforded by the thus-configured fluorescence-endoscope apparatus of the present invention will be described.

Here, for example, it is assumed that, as shown inFIGS. 21A to 21C, the individual spectral images are acquired at the fluorescence wavelengths λ1to λ3when the maximum-fluorescence wavelength λ2emitted from the fluorescent component2among the three types of fluorescent components1to3is considerably dark. In this case, if an adjustment for increasing the exposure time for the fluorescence image of the fluorescent component2is not made, even if the UNMIXING technique described in Publication of Japanese Patent No. 2008-43396 is applied to the spectral images shown inFIGS. 21A to 21C, as shown inFIG. 3B, the distribution image of the fluorescent component2becomes dark, making it impossible to observe.

Next, if the exposure time of the fluorescence image at the fluorescence wavelength λ2is made longer than the exposure time under the reference exposure conditions, the spectral images shown inFIGS. 22A to 22Care acquired. In this case, if the UNMIXING technique described in Publication of Japanese Patent No. 2008-43396 is applied, as shown inFIG. 4B,

it is possible to extract the bright fluorescence component of the fluorescent component2from the distribution image of the fluorescence component2; however, it is not possible to separate the fluorescent components of the other fluorescent components1and3.

In contrast, according to the present invention, when the spectral images shown inFIGS. 22A to 22Care acquired by increasing the exposure time of the fluorescence image at the fluorescence wavelength λ2from the exposure time under the reference exposure conditions, the fluorescent-component-density computation unit13d2adjusts, in accordance with the change in the exposure time, the UNMIXING coefficients that are obtained upon application of the UNMIXING technique by using the ratio of the changed exposure time to the reference exposure time. Therefore, the densities of the fluorescent components calculated through the matrix equation (1) are obtained on the basis of the values obtained by suitably correcting the UNMIXING coefficients. As a result, as shown inFIGS. 5A to 5C, the acquired spectral images are bright images in which the fluorescence components among the individual fluorescent components1to3are separated.

This will be described using matrices in the UNMIXING technique.

<Intensities of Spectral Images Derived Using UNMIXING Coefficients>

For example, when Iall(λ1), Iall(λ2), and Iall(λ3) are defined as the intensities of the spectral images of the fluorescent components1to3, they are represented by following equations using the UNMIXING coefficients:(1) spectral image at the fluorescence wavelength λ1
Iall(λ1)=D1×a1(λ1)+D2×a2(λ1)+D3×a3(λ1);(2) spectral image at the fluorescence wavelength λ2
Iall(λ2)−D1×a1(λ2)+D2×a2(λ2)+D3×a3(λ2);(3) spectral image at the fluorescence wavelength λ3
Iall(λ3)=D1×a1(λ3)+D2×a2(λ3)+D3×a3(λ3).
<Distribution Images Derived from Above-Mentioned Spectral Images>

According to the above-mentioned equations, the distribution images of the fluorescent components1to3can be expressed by the following equations:(1) distribution image of the fluorescent component1
[Iall(λ1)+Iall(λ2)+Iall(λ3)]−[D2×a2(λ1)+D3×a3(λ1)+D2×a2(λ2)+D3×a3(λ2)+D2×a2(λ3)+D3×a3(λ3)]=D1×a1(λ1)+D1×a1(λ2)+D1×a1(λ3);(2) distribution image of the fluorescent component2
[Iall(λ1)+Iall(λ2)+Iall(λ3)]−[D1×a1(λ1)+D3×a3(λ1)+D1×a1(λ2)+D3×a3(λ2)+D1×a1(λ3)+D3×a3(λ3)]=D2×a2(λ1)+D2×a2(λ2)+D2×a2(λ3);(3) distribution image of the fluorescent component3
[Iall(λ1)+Iall(λ2)+Iall(λ3)]−[D1×a1(λ1)+D2×a2(λ1)+D1×a1(λ2)+D2×a2(λ2)+D1×a1(λ3)+D2×a2(λ3)]=D3×a3(λ1)+D3×a3(λ2)+D3×a3(λ3).

A problem related to the calculation of the density of the fluorescent component2using the conventional UNMIXING technique performed when the exposure conditions for the fluorescence image at the maximum-fluorescence wavelength λ2of the fluorescent component2is changed from the exposure conditions under the reference exposure conditions will be described below.

For example, the exposure conditions for the fluorescence image at the fluorescence wavelength λ2are assumed to be doubled (for example, the exposure time is doubled) because the maximum-fluorescence wavelength λ2of the fluorescent component2is dark. If the UNMIXING coefficients are assumed to be unchanged at this time, the spectral images at the maximum-fluorescence wavelengths λ1to λ3of the fluorescent components1to3are individually expressed as in the following equations using the UNMIXING coefficients. At this time, the densities D1′, D2′, and D3′ of the individual fluorescent components have different values from the densities D1, D2, and D3under the reference exposure conditions due to the change in the exposure conditions.

(1) spectral image at the fluorescence wavelength λ1
Iall(λ1)=D1′×a1(λ1)+D2′×a2(λ1)+D3′×a3(λ1);(2) spectral image at the fluorescence wavelength λ2
2×Iall(λ2)=D1′×a1(λ2)+D2′×a2(λ2)+D3′×a3(λ2);(3) spectral image at the fluorescence wavelength λ3
Iall(λ3)=D1′×a1(λ3)+D2′×a2(λ3)+D3′×a3(λ3).

However, in practice, the spectral image at the fluorescence wavelength λ2when the exposure conditions for the fluorescence wavelength λ2are doubled (for example, the exposure time is doubled) is expressed as:
2×Iall(λ2)=2×[D1′×a1(λ2)+D2′×a2(λ2)+D3′×a3(λ2)].
Therefore:(1) the distribution image of the fluorescent component1is expressed as:
[Iall(λ1)+2×Iall(λ2)+Iall(λ3)]−[D2′×a2(λ1)+D3′×a3(λ1)+D2′×a2(λ2)+D3′×a3(λ2)+D2′×a2(λ3)+D3′×a3(λ3)]=D1′×a1(λ1)+D1′×a1(λ2)+D1′×a1(λ3)+D1′×a1(λ2)+D2′×a2(λ2)+D3′×a3(λ2),
and so, as shown inFIG. 4A, it is not possible to separate the fluorescence component D2′×a2(λ2) of the fluorescent component2and the fluorescence component D3′×a3(λ2) of the fluorescent component3;(2) the distribution image of the fluorescent component2is expressed as:
[Iall(λ1)+2×Iall(λ2)+Iall(λ3)]−[D1′×a1(λ1)+D3′×a3(λ1)+D1′×a1(λ2)+D3′×a3(λ2)+D1′×a1(λ3)+D3′×a3(λ3)]=D2′×a2(λ1)+D2′×a2(λ2)+D2′×a2(λ3)+D2′×a2(λ2)+D1′×a1(λ2)+D3′×a3(λ2),
and so, as shown inFIG. 4B, it is not possible to separate the fluorescence component D1′×a1(λ2) of the fluorescent component1and the fluorescence component D3′×a3(λ2) of the fluorescent component3; and(3) the distribution image of the fluorescent component3is expressed as:
[Iall(λ1)+2×Iall(λ2)+Iall(λ3)]−[D1′×a1(λ1)+D2′×a2(λ1)+D1′×a1(λ2)+D2′×a2(λ2)+D1′×a1(λ3)+D2′×a2(λ3)]=D3′×a3(λ1)+D3′×a3(λ2)+D3′×a3(λ3)+D3′×a3(λ2)+D1′×a1(λ2)+D2′×a2(λ2),
and so, as shown inFIG. 4C, it is not possible to separate the fluorescence component D1′×a1(λ2) of the fluorescent component1and the fluorescence component D2′×a2(λ2) of the fluorescent component2.

For example, the exposure conditions for the fluorescence image at the fluorescence wavelength λ2are assumed to be halved (for example, the exposure time is halved) because the maximum-fluorescence wavelength λ2of the fluorescent component2is excessively bright. If the UNMIXING coefficients are assumed to be unchanged at this time, the spectral images at the maximum-fluorescence wavelengths λ1to λ3of the fluorescent components1to3are expressed as follows using the UNMIXING coefficients. At this time, the densities D1″, D2″, and D3″ of the individual fluorescent components have different values from the densities D1, D2, and D3under the reference exposure conditions due to the change in the exposure conditions.

(1) spectral image at the fluorescence wavelength λ1:
Iall(λ1)=D1″×a1(λ1)+D2″×a2(λ1)+D3″×a3(λ1)(2) spectral image at the fluorescence wavelength λ2:
½×Iall(λ2)=D1″×a1(λ2)+D2″×a2(λ2)+D3″×a3(λ2)(3) spectral image at the fluorescence wavelength λ3:
Iall(λ3)=D1″×a1(λ3)+D2″×a2(λ3)+D3″×a3(λ3)

However, in practice, the spectral image at the fluorescence wavelength λ2when the exposure conditions for the fluorescence wavelength λ2are halved (for example, the exposure time is halved) is expressed as:
½×Iall(λ2)=½×[D1″×a1(λ2)+D2″×a2(λ2)+D3″×a3(λ2)].
Therefore:(1) The distribution image of the fluorescent component1is expressed as
[Iall(λ1)+½×Iall(λ2)+Iall(λ3)]−[D2″×a2(λ1)+D3″×a3(λ1)+D2″×a2(λ2)+D3″×a3(λ2)+D2″×a2(λ3)+D3″×a3(λ3)]=D1″×a1(λ1)+D1″×a1(λ2)+D1″×a1(λ3)−½×[D1″×a1(λ2)+D2″×a2(λ2)+D3″×a3(λ2)],
and so, the fluorescence component of the fluorescent component1becomes darker than necessary by −½×D1″×a1(λ2).(2) The distribution image of the fluorescent component2is expressed as
[Iall(λ1)+½×Iall(λ2)+Iall(λ3)]−[D1″×a1(λ1)+D3″×a3(λ1)+D1″×a1(λ2)+D3″×a3(λ2)+D1″×a1(λ3)+D3″×a3(λ3)]=D2″×a2(λ1)+D2″×a2(λ2)+D2″×a2(λ3)−½×[D2″×a2(λ2)+D1″×a1(λ2)+D3″×a3(λ2)],
and so, the fluorescence component of the fluorescent component2becomes darker than necessary by −½×D2″×a2(λ2). As a result, as shown inFIG. 3B, it is not possible to acquire the distribution image of the fluorescent component2.(3) The distribution image of the fluorescent component3is expressed as
[Iall(λ1)+½×Iall(λ2)+Iall(λ3)]−[D2″×a2(λ1)+D3″×a3(λ1)+D2″×a2(λ2)+D3″×a3(λ2)+D2″×a2(λ3)+D3″×a3(λ3)]=D3″×a3(λ1)+D3″×a3(λ2)+D3″×a3(λ3)−½×[D3″×a3(λ2)+D1″×a1(λ2)+D2″×a2(λ2)],
and so, the fluorescence component of the fluorescent component3becomes darker than necessary by −½×D3″×a3(λ2).

In contrast, in the present invention, as described above, the fluorescent-component-density computation unit13d2adjusts, in accordance with the change in the exposure time, the UNMIXING coefficients that are obtained upon application of the UNMIXING technique by using the ratio of the changed exposure time to the reference exposure time. Therefore, the densities of the fluorescent components that are to be calculated through the matrix equation (1) are obtained on the basis of the values obtained by suitably correcting the UNMIXING coefficients.

Specifically, for example, the exposure conditions for the fluorescence image at the fluorescence wavelength λ2are assumed to be doubled (for example, the exposure time is doubled) because the maximum-fluorescence wavelength λ2of the fluorescent component2is dark. If the UNMIXING coefficients are assumed to be changed at this time, the spectral images at the maximum-fluorescence wavelengths λ1to λ3of the fluorescent components1to3are expressed as follows using the UNMIXING coefficients.

(1) spectral image at the fluorescence wavelength λ1
Iall(λ1)=D1×a1(λ1)+D2×a2(λ1)+D3×a3(λ1);(2) spectral image at the fluorescence wavelength λ2
2×Iall(λ2)=D1×a1(λ2)×2+D2×a2(λ2)×2+D3×a3(λ2)×2;(3) spectral image at the fluorescence wavelength λ3
Iall(λ3)=D1×a1(λ3)+D2×a2(λ3)+D3×a3(λ3).
Therefore:(1) The distribution image of the fluorescent component1is expressed as
[Iall(λ1)+2×Iall(λ2)+Iall(λ3)]−[D2×a2(λ1)+D3×a3(λ1)+D2×a2(λ2)×2+D3×a3(2)×2+D2×a2(λ3)+D3×a3(λ3)]=D1×a1(λ1)+D1×a1(λ2)×2+D1×a1(λ3),
and so, as shown inFIG. 5A, an image that is separated from the fluorescence components of the fluorescent components2and3is acquired.(2) The distribution image of the fluorescent component2is expressed as
[Iall(λ1)+2×Iall(λ2)+Iall(λ3)]−[D1×a1(λ1)+D3×a3(λ1)+D1×a1(λ2)×2+D3×a3(λ2)×2+D1×a1(λ3)+D3×a3(λ3)]=D2×a2(λ1)+D2×a2(λ2)×2+D2×a2(λ3),
and so, as shown inFIG. 5B, an image that is separated from the fluorescence components of the fluorescent components1and3is acquired.(3) The distribution image of the fluorescent component3is expressed as
[Iall(λ1)+2×Iall(λ2)+Iall(λ3)]−[D1×a1(λ1)+D2×a2(λ1)+D1×a1(λ2)×2+D2×a2(λ2)×2+D1×a1(λ3)+D2×a2(λ3)]=D3×a3(λ1)+D3×a3(λ2)×2+D3×a3(λ3),
and so, as shown inFIG. 5C, an image that is separated from the fluorescence components of the fluorescent components2and3is acquired.

Under the situation where the exposure conditions have been changed, the calculation of the densities of the fluorescent components according to the conventional UNMIXING technique and the calculation of the densities of the fluorescent components according to the present invention will be described below using further specific values.

For the sake of convenience of description, the case where two types of fluorescent components1and2are used will be described.

FIGS. 6A and 6Bare diagrams showing fluorescence spectra of the individual fluorescent components1and2under the reference exposure conditions and fluorescence spectra of a measurement target in which the fluorescent components1and2are present in a mixed manner, whereFIG. 6Ais a diagram showing individual spectra when the fluorescence intensities of the individual fluorescent components1and2are substantially the same,FIG. 63is a diagram showing individual spectra when the fluorescence intensities of the individual fluorescent components1and2are considerably different, andFIG. 6Cis a diagram showing the fluorescence spectral properties of the individual fluorescent components1and2at the individual normalized densities.

Calculation of the densities of the fluorescent components will be described, using individual fluorescent components1and2, which are conventional fluorescence spectral properties at a individual normalized densities, as shown inFIG. 6C.

When Iall(λ1) and Iall(λ2) are defined as the intensities of the spectral images of the fluorescent components1and2, the spectral images can be expressed as in Equation (21) below using the UNMIXING coefficients:

According to Equation (21), the densities D1and D2of the individual fluorescent components1and2can be expressed as in Equation (22) below:

According to Equation (22), the densities D1and D2of the fluorescent components1and2are obtained by solving Equations (23) and (24) below:

First, as shown inFIG. 6A, in the case where the density distribution of the fluorescent components1and2individually has the fluorescence intensities of substantially the same brightness and where the exposure conditions have been changed, the calculation of the densities of the fluorescent components according to the conventional UNMIXING technique and the calculation of the densities of the fluorescent components according to the present invention will be described.

In this case, as shown inFIG. 6(C), the fluorescence intensity at a fluorescence wavelength λ1of the fluorescent component1is assumed to be 1, and the fluorescence intensity at a fluorescence wavelength λ2of the fluorescent component1is assumed to be 0.5. The fluorescence intensity at a fluorescence wavelength λ1of the fluorescent component2is assumed to be 0.5, and the fluorescence intensity at a fluorescence wavelength λ2of the fluorescent component2is assumed to be 1.

As shown inFIG. 6A, the intensities of the spectral images at the wavelengths λ1and λ2are assumed to be unity, respectively.

By applying this to Equation (21) above, the spectral images at this time can be expressed as in Equation (21a) below:

By applying this to Equations (23) and (24) above, the densities D1and D2of the fluorescent components1and2are expressed as:

The distribution image of the fluorescent component1at this time is expressed as:

[Iall⁡(λ⁢⁢1)+Iall⁡(λ⁢⁢2)]-[D⁢⁢2×a⁢⁢2⁢(λ⁢⁢1)+D⁢⁢2×a⁢⁢2⁢(λ⁢⁢2)]=D⁢⁢1×a⁢⁢1⁢(λ⁢⁢1)+D⁢⁢1×a⁢⁢1⁢(λ⁢⁢2)=0.67×a⁢⁢1⁢(λ⁢⁢1)+0.67×a⁢⁢1⁢(λ⁢⁢2),
and so, an image in which only the fluorescence component of the fluorescent component1is present and the fluorescence component of the fluorescent component2is not present is acquired.

The distribution image of the fluorescent component2is expressed as:
[Iall(λ1)+Iall(λ2)]−[D1×a1(λ1)+D1×a1(λ2)]=D2×a2(λ1)+D2×a2(λ2)=0.67×a2(λ1)+0.67×a2(λ2),
and so, an image in which only the fluorescence component of the fluorescent component2is present and the fluorescence component of the fluorescent component1is not present is acquired.

Here, the calculated values for the densities of the fluorescent components1and2according to the conventional UNMIXING technique and the calculated values for the densities of the fluorescent components1and2according to the present invention will be shown for the case where the exposure time of the fluorescence wavelength λ2is made 10-times greater to make the fluorescence intensity Iall(λ2) 10-times greater.

With the method of calculating the densities of the fluorescent components1and2according to the conventional UNMIXING technique, by applying this to Equation (21) above, the spectral images can be expressed as in Equation (21b) below:

By applying this to Equations (23) and (24) above, the densities D1′ and D2′ of the fluorescent components1and2are expressed as:

D⁢⁢1′=11-0.25⁢(1-5)≈-5.33⁢⁢D⁢⁢2′=11-0.25⁢(-0.5+10)≈12.67,[Expression⁢⁢17]
and so, values different from the densities D1and D2that are obtained from Equation (21a) above are obtained.

The distribution image of the fluorescent component1at this time is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D2′×a2(λ1)+D2′×a2(λ2)]=D1′×a1(λ1)+D2′×a2(λ1)+10[D1′×a1(λ2)+D2′×a2(λ2)]−[D2′×a2(λ1)+D2′×a2(λ2)]=D1′×a1(λ1)+10D1′×a1(λ2)+9D2′×a2(λ2),
and so, it is not possible to separate the fluorescence component9D2′×a2(λ2) of the fluorescent component2.

Here, the fluorescence component of the fluorescent component1in the distribution image of the fluorescent component1is expressed as:
D1′×a1(λ1)+10D1′×a1(λ2)≈−5.33×a1(λ1)+10×(−5.33)×a2(λ2).

The fluorescence component of the fluorescent component2in the distribution image of the fluorescent component1is expressed as:
9D2′×a2(λ2)≈9×12.67×a2(λ2).

The distribution image of the fluorescent component2is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D1′×a1(λ1)+D1′×a1(λ2)]=D1′×a1(λ1)+D2′×a2(λ1)+10[D1′×a1(λ2)+D2′×a2(λ2)]−[D1′×a1(λ1)+D1′×a1(λ2)]=D2′×a2(λ1)+9D1′×a2(λ2)+10D2′×a2(λ2),
and so, it is not possible to separate the fluorescence component9D1′×a2(λ2) of the fluorescent component1.

Here, the fluorescence component of the fluorescent component1in the distribution image of the fluorescent component1is expressed as:
9D1′×a2(λ2)≈9×(−5.33)×a2(λ2).

The fluorescence component of the fluorescent component2in the distribution image of the fluorescent component1is expressed as:
D2′×a2(λ1)+10D2′×a2(λ2)≈12.67×a2(λ1)+10×12.67×a2(λ2).

In contrast, in the present invention, as described above, the fluorescent-component-density computation unit13d2adjusts, in accordance with the change in the exposure time, the UNMIXING coefficients that are obtained upon application of the UNMIXING technique by using the ratio of the changed exposure time to the reference exposure time. Therefore, the densities of the fluorescent components that are to be calculated through the matrix equation (1) are obtained on the basis of the values obtained by suitably correcting the UNMIXING coefficients.

In other words, in the method of calculating the densities of the fluorescent components1and2according to the UNMIXING technique of the present invention, by applying this to Equation (21) above, the spectral image can be expressed as in Equation (21c) below:

By applying this to Equations (23) and (24) above, the densities D1and D2of the fluorescent components1and2are expressed as:

D⁢⁢1=110-2.5⁢(10-5)≈0.67⁢⁢D⁢⁢2=110-2.5⁢(-5+10)≈0.67,[Expression⁢⁢19]
and the values become the same as those of the densities D1and D2obtained from Equation (21a) above.

The distribution image of the fluorescent component1at this time is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D2×a2(λ1)+10×D2×a2(λ2)]=D1×a1(λ1)+D2×a2(λ1)+10[D1×a1(λ2)+D2×a2(λ2)]−[D2×a2(λ1)+10×D2×a2(λ2)]=D1×a1(λ1)+10×D1×a1(λ2),
and so, an image that is separated from the fluorescence component of the fluorescent component2is acquired.

Here, the distribution image of the fluorescent component1contains only the fluorescence component of the fluorescent component1and is expressed as:
D1×a1(λ1)+10×D1×a1(λ2)≈0.67×a1(λ1)+10×0.67×a1(λ2).

The distribution image of the fluorescent component2is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D1×a1(λ1)+10×D1×a1(λ2)]=D1×a1(λ1)+D2×a2(λ1)+10[D1×a1(λ2)+D2×a2(λ2)]−[D1×a1(λ1)+10×D1×a1(λ2)]=D2×a2(λ1)+10×D2×a2(λ2),
and so, an image that is separated from the fluorescence component of the fluorescent component1is acquired.

At this time, the distribution image of the fluorescent component2contains only the fluorescence component of the fluorescent component2and is expressed as:
D2×a2(λ1)+10×D2×a2(λ2)≈12.67×a2(λ1)+10×12.67×a2(λ2).

Next, as shown inFIG. 6B, the case where the fluorescence intensities of the individual fluorescent components1and2have a density distribution to be considerably different brightness will be described.

In this case, as shown inFIG. 6(C), the fluorescence intensity at a fluorescence wavelength λ1of the fluorescent component1is assumed to be 1, and the fluorescence intensity at a fluorescence wavelength λ2of the fluorescent component1is assumed to be 0.5. The fluorescence intensity at a fluorescence wavelength λ1of the fluorescent component2is assumed to be 0.5, and the fluorescence intensity at a fluorescence wavelength λ2of the fluorescent component2is assumed to be 1.

As shown inFIG. 6B, the intensities of the spectral images at the wavelengths λ1are assumed to be 1, and the intensities of the spectral images at the wavelengths λ2are assumed to be 0.55.

By applying this to Equation (21) above, the spectral images at this time can be expressed as in Equation (21a′) below:

By applying this to Equations (23) and (24) above, the densities D1and D2of the fluorescent components1and2are expressed as:

The distribution image of the fluorescent component1at this time is expressed as:
[Iall(λ1)+Iall(λ2)]−[D2×a2(λ1)+D2×a2(λ2)]=D1×a1(λ1)+D1×a1(λ2),
and so, an image in which the fluorescence component of the fluorescent component2is not present is acquired.

Here, the distribution image of the fluorescent component1contains only the fluorescence component of the fluorescent component1and is expressed as:
D1×a1(λ1)+D1×a1(λ2)≈0.97×a1(λ1)+0.97×a2(λ2).

The distribution image of the fluorescent component2is expressed as:
[Iall(λ1)+Iall(λ2)]−[D1×a1(λ1)+D1×a1(λ2)]=D2×a2(λ1)+D2×a2(λ2),
and so, an image in which the fluorescence component of the fluorescent component1is not present is acquired.

Here, the distribution image of the fluorescent component2contains only the fluorescence component of the fluorescent component2and is expressed as:
D2×a2(λ1)+D2×a2(λ2)≈0.07×a2(λ1)+0.07×a2(λ2).

Here, the calculated values for the densities of the fluorescent components1and2according to the conventional UNMIXING technique and the calculated values for the densities of the fluorescent components1and2according to the present invention are shown for the case where the exposure time of the fluorescence wavelength λ2is made 10-times greater to make the fluorescence intensity Iall(λ2) 10-times greater.

With the method of calculating the densities of the fluorescent components1and2according to the conventional UNMIXING technique, by applying this to Equation (21) above, the spectral images can be expressed as in Equation (21b′) below:

By applying this to Equations (23) and (24) above, the densities D1′ and D2′ of the fluorescent components1and2are expressed as:

D⁢⁢1′=11-0.25⁢(1-2.75)≈-2.33⁢⁢D⁢⁢2′=11-0.25⁢(-0.5+5.5)≈6.67,[Expression⁢⁢23]
and so, values different from those of the densities D1and D2obtained from Equation (21a′) above are obtained.

The distribution image of the fluorescent component1at this time is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D2′×a2(λ1)+D2′×a2(λ2)]=D1′×a1(λ1)+D2′×a2(λ1)+10[D1′×a1(λ2)+D2′×a2(λ2)]−[D2′×a2(λ1)+D2′×a2(λ2)]=D1′×a1(λ1)+10D1′×a1(λ2)+9D2′×a2(λ2),
and so, it is not possible to separate the fluorescence component9D2′×a2(λ2) of the fluorescent component2.

Here, the fluorescence component of the fluorescent component1in the distribution image of the fluorescent component1is expressed as:
D1′×a1(λ1)+10D1′×a1(λ2)≈−2.33×a1(λ1)+10×(−2.33)×a1(λ2).

The fluorescence component of the fluorescent component2in the distribution image of the fluorescent component1is expressed as:
9D2′×a2(λ2)≈9×6.67×a2(λ2).

The distribution image of the fluorescent component2is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D1′×a1(λ1)+D1′×a1(λ2)]=D1′×a1(λ1)+D2′×a2(λ1)+10[D1′×a1(λ2)+D2′×a2(λ2)]−[D1′×a1(λ1)+D1′×a1(λ2)]=D2′×a2(λ1)+9D1′×a1(λ2)+10D2′×a2(λ2),
and so, it is not possible to separate the fluorescence component9D1′×a1(λ2) of the fluorescent component1.

Here, the fluorescence component of the fluorescent component1in the distribution image of the fluorescent component2is expressed as:
9D1′×a1(λ2)≈9×(−2.33)×a1(λ2).

The fluorescence component of the fluorescent component2in the distribution image of the fluorescent component2is expressed as:
D2′×a2(λ1)+10D2′×a2(λ2)≈6.67×a2(λ1)+10×6.67×a1(λ2).

In contrast, in the method of calculating the densities of the fluorescent components1and2according to the UNMIXING technique of the present invention, by applying this to Equation (21) above, the spectral image can be expressed as in Equation (21c′) below:

By applying this to Equations (23) and (24) above, the densities D1and D2of the fluorescent components1and2are expressed as:

D⁢⁢1=110-2.5⁢(10-2.75)≈0.97⁢⁢D⁢⁢2=110-2.5⁢(-5+5.5)≈0.07,[Expression⁢⁢25]
and the values become the same as those of the densities D1and D2obtained from Equation (21a′) above.

The distribution image of the fluorescent component1at this time is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D2×a2(λ1)+10×D2×a2(λ2)]=D1×a1(λ1)+D2×a2(λ1)+10[D1×a1(λ2)+D2×a2(λ2)]−[D2×a2(λ1)+10×D2×a2(λ2)]=D1×a1(λ1)+10×D1×a1(λ2),
and so, an image that is separated from the fluorescence component of the fluorescent component2is acquired.

Here, the distribution image of the fluorescent component1contains only the fluorescence component of the fluorescent component1and is expressed as:
D1×a1(λ1)+10×D1×a1(λ2)≈0.97×a1(λ1)+10×0.97×a1(λ2).

The distribution image of the fluorescent component2is expressed as:
[Iall(λ1)+10×Iall(λ2)]−[D1×a1(λ1)+10×D1×a1(λ2)]=D1×a1(λ1)+D2×a2(λ1)+10[D1×a1(λ2)+D2×a2(λ2)]−[D1×a1(λ1)+10×D1×a1(λ2)]=D2×a2(λ1)+10×D2×a2(λ2),
and so, an image that is separated from the fluorescence component of the fluorescent component1is acquired.

The distribution image of the fluorescent component2at this time is expressed as:
D2×a2(λ1)+10×D2×a2(λ2)≈0.07×a2(λ1)+10×0.07×a2(λ2).

Therefore, according to the fluorescence-endoscope apparatus of the present invention, it is possible to provide a fluorescence-endoscope apparatus that is capable of, even if the exposure conditions are changed, displaying the individual fluorescent components in a separated manner regardless of the change in the exposure conditions while keeping the frame rate unchanged as much as possible, such that the brightnesses of the individual fluorescent components become brightnesses suitable for observing the fluorescence image.

FIGS. 7A to 7Eare explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 1 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 7Ais a diagram showing, in time-series, the light in each of the wavelength ranges selected by and transmitted through the tunable light-dispersing element12b4under the reference exposure conditions,FIG. 7Bis a diagram showing, in time-series, the light in each of the wavelength ranges that has been, at substantially the same time as inFIG. 7A, photoelectrically converted through the image acquisition device12b5and stored in each of the frame memories13c1,13c2, and13c3,FIG. 7Cis a diagram showing, in time-series, the light in each of the wavelength ranges selected by and transmitted through the tunable light-dispersing element12b4under the exposure conditions in Example 1,FIG. 7Dis a diagram showing, in time-series, the light in each of the wavelength ranges that has been, at substantially the same time as inFIG. 7C, photoelectrically converted through the image acquisition device12b5and stored in each of the frame memories13c1,13c2, and13c3, andFIG. 7Eis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 7CandFIG. 7D.

The basic configuration of the fluorescence-endoscope apparatus of Example 1 is as described above usingFIGS. 1 and 2.

With the fluorescence-endoscope apparatus of Example 1, as shown inFIG. 7C, the exposure conditions are changed through the exposure-conditions setting unit15such that, by increasing transmitting time tλ2′ of the fluorescence wavelength λ2from the fluorescent component2that has been transmitted through the tunable light-dispersing element12b4in comparison with transmitting time tλ2under the reference exposure conditions shown inFIG. 7Aso that the time to be stored by the frame memory13c2is increased by the same amount, as shown inFIG. 7D.

When the density D1of the fluorescent component1to the density Dm of the fluorescent component m are calculated using Equation (1), in accordance with the change in the exposure time that is made upon acquisition of the fluorescence image at the predetermined wavelength λx among the wavelength λ1to wavelength λn by the image acquisition portion12b, the fluorescent-component-density computation unit13d2multiplies the coefficients a1(λx) to am(λx) at the predetermined wavelength λx of the fluorescent component1to fluorescent component m at the normalized density under the reference exposure conditions by the ratio (tλ2′/tλ2) of the changed exposure time tλ2′ to the exposure time tλ2under the reference exposure conditions when the fluorescence image at the predetermined wavelength λx is acquired by the image acquisition portion12b.

The spectral image under the exposure conditions in Example 1 can be expressed as in Equation (1a′) below, when expressed by a matrix equation using the UNMIXING coefficients:

According to this Equation (1a′), the fluorescent-component-density computation unit13d2calculates the densities D1to D3of the fluorescent components1to3.

According to the fluorescence-endoscope apparatus of Example 1, even if the exposure time for the spectral image at the specific detection wavelength is changed, because deterioration of the frame rate is minimized as much as possible, it is possible to detect, at high brightness, a plurality of fluorophores in a state where the individual detection wavelengths are separated.

FIGS. 8A to 8Care explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 2 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 8Ais a diagram showing, in time-series, the light in each of the wavelength ranges selected by and transmitted through the tunable light-dispersing element12b4under the reference exposure conditions,FIG. 8Bis a diagram showing, in time-series, the light in each of the wavelength ranges selected by and transmitted through the tunable light-dispersing element12b4under the exposure conditions in Example 2, andFIG. 8Cis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 8B.

With the fluorescence-endoscope apparatus of Example 2, as shown inFIG. 8B, the exposure conditions are changed through the exposure-conditions setting unit15, while keeping the frame rate constant, such that the ratio of the exposure times tλ1″, tλ2″, and tλ3″ at the individual detection wavelengths λ1to λ3differs from the ratio of the exposure times tλ1, tλ2, and tλ3at the individual detection wavelengths λ1to λ3under the reference exposure conditions shown inFIG. 8A.

When the density D1of the fluorescent component1to the density D3of the fluorescent component3are calculated using Equation (1), in accordance with the change in the exposure time that is made upon acquisition of the fluorescence image at the individual wavelengths of the wavelength λ1to wavelength λ3by the image acquisition portion12bwhile keeping the frame rate constant, the fluorescent-component-density computation unit13d2individually multiplies the coefficients a1(λ1) to a3(λ1) to a1(λ3) to a3(λ3) at the individual wavelengths of the wavelength λ1to wavelength λ3of the fluorescent component1to fluorescent component3at the normalized density under the reference exposure conditions by the ratios (tλ1″/tλ1, tλ2″/tλ2, and tλ3″/tλ3) of the changed exposure times tλ1″, tλ2″, and tλ3″ to the exposure times tλ1, tλ2, and tλ3under the reference exposure conditions when the fluorescence images at the individual wavelengths of the wavelength λ1to wavelength λ3are acquired by the image acquisition portion12b.

The spectral images under the exposure conditions in Example 2 can be expressed as in Equation (1b′) below when expressed by the matrix equation using the UNMIXING coefficients:

According to this Equation (1b′), the fluorescent-component-density computation unit13d2calculates the densities D1to D3of the fluorescent components1to3.

As described above, the frame rate is constant in Example 2. Accordingly, Equation (1b′) above is expressed as:

According to the fluorescence-endoscope apparatus of Example 2, even if the exposure times for the spectral images at the individual detection wavelengths are changed in such a manner that deterioration of the frame rate is avoided, it is possible to detect, at high brightness, a plurality of fluorophores in a state where the individual detection wavelengths are separated and the brightnesses are balanced.

Other configurations, effects, and advantages are substantially the same as those of the fluorescence-endoscope apparatus of Example 1.

FIGS. 9A to 9Care explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 3 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 9Ais a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the reference exposure conditions,FIG. 9Bis a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the exposure conditions in Example 3, andFIG. 9Cis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 9B.

With the fluorescence-endoscope apparatus of Example 3, as shown inFIG. 9B, by increasing the intensity IEX2′ of the excitation light that excites the fluorescence wavelength λ2of the fluorescent component2compared with the intensity IEX2under the reference exposure conditions shown inFIG. 9A, the exposure conditions are changed through the exposure-conditions setting unit15such that the intensity stored in the frame memory13c2becomes stronger by the same amount.

When the density D1of the fluorescent component1to the density D3of the fluorescent component3are calculated using Equation (1), in accordance with the change in the intensity of the excitation light that excites the fluorescence wavelength λ2that is made upon acquisition of the fluorescence image at the fluorescence wavelength λ2by the image acquisition portion12b, the fluorescent-component-density computation unit13d2multiplies the coefficients a1(λ2) to a3(λ2) at the wavelength λ2of the fluorescent component1to fluorescent component3at the normalized density under the reference exposure conditions by the ratio (IEX2′/IEX2) of the changed intensity IEX2′ of the excitation light that excites the fluorescence wavelength λ2to the intensity IEX2of the excitation light that excites the fluorescence wavelength λ2under the reference exposure conditions when the fluorescence image at the fluorescence wavelength λ2is acquired by the image acquisition portion12b.

The spectral images under the exposure conditions in Example 3 can be expressed as in Equation (1c′) below when expressed by the matrix equation using the UNMIXING coefficients:

According to this Equation (1c′), the fluorescent-component-density computation unit13d2calculates the densities D1to D3of the fluorescent components1to3.

According to the fluorescence-endoscope apparatus of Example 3, even if the excitation intensity for the spectral image at the specific detection wavelength is changed in such a manner that deterioration of the frame rate is avoided, it is possible to detect, at high brightness, a plurality of fluorophores in a state where the individual detection wavelengths are separated.

FIGS. 10A to 10Care explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 4 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 10Ais a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light that excites the fluorescence wavelengths of the individual fluorescent components under the reference exposure conditions,FIG. 10Bis a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the exposure conditions in Example 4, andFIG. 10Cis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 10B.

With the fluorescence-endoscope apparatus of Example 4, as shown inFIG. 10B, by changing the intensities IEX1″ to IEX3″ of the individual excitation light beams that individually excite the fluorescence wavelength λ1of the fluorescent component1to fluorescence wavelength λ3of the fluorescent component3relative to the intensities IEX1to IEX3under the reference exposure conditions shown inFIG. 10A, the exposure conditions are changed through the exposure-conditions setting unit15such that the intensities stored in the frame memories13c1to13c3are changed by the same amount.

When the density D1of the fluorescent component1to the density D3of the fluorescent component3are calculated using Equation (1), in accordance with the change in the intensities of the excitation light beams that excite the individual wavelengths that is made upon acquisition of the fluorescence images at the individual wavelengths of the wavelength λ1to wavelength λ3by the image acquisition portion12b, the fluorescent-component-density computation unit13d2individually multiplies the coefficients a1(λ1) to a3(λ1) to a1(λ3) to a3(λ3) at the individual wavelengths of the wavelength λ1to wavelength λ3of the fluorescent component1to fluorescent component3at the normalized density under the reference exposure conditions by the ratios (IEX1″, IEX1, IEX2″, IEX2, and IEX3″/IEX3) of the changed intensities IEX1″, IEX2″ and IEX3″ of the excitation light that excites the individual wavelengths to the intensities IEX1, IEX2, and IEX3of the excitation light that excites the individual wavelengths under the reference exposure conditions when the fluorescence images at the individual wavelengths of the wavelength λ1to wavelength λ3are acquired by the image acquisition portion12b.

The spectral images under the exposure conditions in Example 4 can be expressed as in Equation (1d′) below when expressed by the matrix equation using the UNMIXING coefficients:

According to this Equation (1d′), the fluorescent-component-density computation unit13d2calculates the densities D1to D3of the fluorescent components1to3.

According to the fluorescence-endoscope apparatus of Example 4, even if the excitation intensity for the spectral image at the individual detection wavelengths is changed in such a manner that deterioration of the frame rate is avoided, it is possible to detect, at high brightness, a plurality of fluorophores in a brightness state where the individual detection wavelengths are separated and the brightnesses are balanced.

FIGS. 11A to 11Care explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 5 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 11Ais a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the reference exposure conditions,FIG. 11Bis a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excite the fluorescence wavelengths of the individual fluorescent components in Example 5, andFIG. 11Cis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 11B.

With the fluorescence-endoscope apparatus of Example 5, as shown inFIG. 11B, by reducing the excitation time tEx2′ of the excitation light that excites the fluorescence wavelength λ2of the fluorescent component2compared with the excitation time tEx2under the reference exposure conditions shown inFIG. 11A, the exposure conditions are changed through the exposure-conditions setting unit15such that the intensity stored in the frame memory13c2becomes weaker by the same amount.

When the density D1of the fluorescent component1to the density D3of the fluorescent component3are calculated using Equation (1), in accordance with the change in the intensity of the excitation light that excites the fluorescence wavelength λ2that is made upon acquisition of the fluorescence image at the fluorescence wavelength λ2 by the image acquisition portion12b, the fluorescent-component-density computation unit13d2multiplies the coefficients a1(λ2) to a3(λ2) at the wavelength λ2 of the fluorescent component 1 to fluorescent component 3 at the normalized density under the reference exposure conditions by the ratio (tEX2′/tEX2) of the changed excitation time tEX2′ of the excitation light that excites the fluorescence wavelength λ2 to the excitation time tEX2of excitation light that excites the fluorescence wavelength λ2 under the reference exposure conditions when the fluorescence image at the fluorescence wavelength λ2 is acquired by the image acquisition portion12b.

The spectral images under the exposure conditions in Example 5 can be expressed as in Equation (1e′) below when expressed by the matrix equation using the UNMIXING coefficients:

According to this Equation (1e′), the fluorescent-component-density computation unit13d2calculates the densities D1 to D3 of the fluorescent components 1 to 3.

According to the fluorescence-endoscope apparatus of Example 5, even if the excitation time for the spectral image at the specific detection wavelength is changed in such a manner that deterioration of the frame rate is avoided, it is possible to detect, at high brightness, a plurality of fluorophores in a state where the individual detection wavelengths are separated and the brightnesses are balanced.

FIGS. 12A to 12Care explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 6 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 12Ais a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the reference exposure conditions,FIG. 12Bis a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the exposure conditions in Example 6, andFIG. 12Cis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 12B.

With the fluorescence-endoscope apparatus of Example 6, as shown inFIG. 12B, by changing the excitation intensity IEx2′ and the excitation time tEx2′ of the excitation light that excites the fluorescence wavelength λ2 of the fluorescent component 2 relative to the excitation intensity IEx2and the excitation time tEx2under the reference exposure conditions shown inFIG. 12A, the exposure conditions are changed through the exposure-conditions setting unit15such that the intensity stored in the frame memory13c2is changed by the same amount.

When the density D1 of the fluorescent component 1 to the density D3 of the fluorescent component 3 are calculated using Equation (1), in accordance with the change in the intensity and the excitation time of the excitation light that excites the predetermined wavelength λ2 that is made upon acquisition of the fluorescence image at the predetermined wavelength λ2 among the wavelength λ1 to wavelength λ3 by the image acquisition portion12b, the fluorescent-component-density computation unit13d2multiplies the coefficients a1(λ2) to a3(λ2) at the wavelength λ2 of the fluorescent component 1 to fluorescent component 3 at the normalized density under the reference exposure conditions by the ratio ((IEX2′/IEX2)×(tEX2′/tEX2)) of the changed intensity IEX2′ and the changed excitation time tEX2′ of the excitation light that excites the predetermined wavelength λ2 to the intensity IEX2and the excitation time tEX2of the excitation light that excites the predetermined wavelength λ2 under the reference exposure conditions when the fluorescence image at the predetermined wavelength λ2 is acquired by the image acquisition portion12b.

The spectral images under the exposure conditions in Example 6 can be expressed as in Equation (1f′) below when expressed by the matrix equation using the UNMIXING coefficients:

According to this Equation (1f′), the fluorescent-component-density computation unit13d2calculates the densities D1 to D3 of the fluorescent components 1 to 3.

According to the fluorescence-endoscope apparatus of Example 6, even if the excitation intensity and the excitation time for the spectral image at the specific detection wavelength are changed in such a manner that deterioration of the frame rate is avoided, it is possible to detect, at high brightness, a plurality of fluorophores in a state where the individual detection wavelengths are separated and the brightnesses are balanced.

FIGS. 13A to 13Care explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 7 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 13Ais a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the reference exposure conditions,FIG. 13Bis a diagram showing, in time-series, the intensity and the irradiation timing of each excitation light beam that excites the fluorescence wavelengths of the individual fluorescent components under the exposure conditions in Example 7, andFIG. 13Cis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 13B.

With the fluorescence-endoscope apparatus of Example 7, by changing the intensity of the fluorescence wavelength λ2 of the fluorescent component 2 using an ND filter, the exposure conditions are changed through the exposure-conditions setting unit15such that, as shown inFIG. 13B, the detection intensity I2′ stored in the frame memory13c2becomes weaker by the same amount.

When the density D1 of the fluorescent component 1 to the density D3 of the fluorescent component 3 are calculated using Equation (1), in accordance with the change in the detection intensity that is made upon acquisition of the fluorescence image at the predetermined wavelength λ2 among the wavelength λ1 to wavelength λ3 by the image acquisition portion12b, the fluorescent-component-density computation unit13d2multiplies the coefficients a1(λ2) to a3(λ2) at the predetermined wavelength λ2 of the fluorescent component 1 to fluorescent component 3 at the normalized density under the reference exposure conditions by the ratio (I2′/I2) of the changed detection intensity I2′ to the detection intensity I2under the reference exposure conditions when the fluorescence image at the predetermined wavelength λ2 is acquired by the image acquisition portion12b.

The spectral images under the exposure conditions in Example 7 can be expressed as in Equation (1g′) below when expressed by the matrix equation using the UNMIXING coefficients.

According to this Equation (1g′), the fluorescent-component-density computation unit13d2calculates the densities D1 to D3 of the fluorescent components 1 to 3.

According to the fluorescence-endoscope apparatus of Example 7, even if the detection intensity for the spectral image at the specific detection wavelength is changed in such a manner that deterioration of the frame rate is avoided, it is possible to detect, at high brightness, a plurality of fluorophores in a state where the individual detection wavelengths are separated and the brightnesses are balanced.

FIGS. 14A to 14Care explanatory diagrams showing the exposure conditions in the fluorescence-endoscope apparatus of Example 8 and computation performed by the fluorescent-component-density computation unit13d2, whereFIG. 14Ais a diagram showing, in time-series, the gain and the detection timing of the fluorescence images at the fluorescence wavelengths of the individual fluorescent components under the reference exposure conditions,FIG. 14Bis a diagram showing, in time-series, the gain and the detection timing of the fluorescence images at the fluorescence wavelengths of the individual fluorescent components under the exposure conditions in Example 8, andFIG. 14Cis a diagram showing a matrix equation that is used in the UNMIXING processing performed by the fluorescent-component-density computation unit13d2under the exposure conditions shown inFIG. 14B.

With the fluorescence-endoscope apparatus of Example 8, as shown inFIG. 14B, by changing the gain G2′ at the fluorescence wavelength λ2 of the fluorescent component 2, the exposure conditions are changed through the exposure-conditions setting unit15such that the intensity stored in the frame memory13c2becomes stronger by the same amount.

When the density D1 of the fluorescent component 1 to the density D3 of the fluorescent component 3 are calculated using Equation (1), in accordance with the change in the gain that is made upon acquisition of the fluorescence image at the predetermined wavelength λ2 among the wavelength λ1 to wavelength λ3 by the image acquisition portion12b, the fluorescent-component-density computation unit13d2multiplies the coefficients a1(λ2) to a3(λ2) at the predetermined wavelength λ2 of the fluorescent component 1 to fluorescent component 3 at the normalized density under the reference exposure conditions by the ratio (G2′/G2) of the changed gain G2′ to the gain G2under the reference exposure conditions when the fluorescence image at the predetermined wavelength λ2 is acquired by the image acquisition portion12b.

The spectral images under the exposure conditions in Example 8 can be expressed as in Equation (1h′) below when expressed by the matrix equation using the UNMIXING coefficients:

According to this Equation (1h′), the fluorescent-component-density computation unit13d2calculates the densities D1 to D3 of the fluorescent components 1 to 3.

According to the fluorescence-endoscope apparatus of Example 8, even if the gain for the spectral image at the specific detection wavelength is changed in such a manner that deterioration of the frame rate is avoided, it is possible to detect, at high brightness, a plurality of fluorophores in a state where the individual detection wavelengths are separated and the brightnesses are balanced.

Although Examples of the present invention have been described above, the fluorescence-endoscope apparatus of the present invention is not limited to these Examples: for example, regarding the change in the combined exposure conditions of the exposure condition items in the individual examples, the fluorescent-component-density computation unit13d2may multiply the ratio of the values of the combination of the exposure condition items under the reference exposure conditions to the values of the combination of the changed exposure condition items by the UNMIXING coefficients of the fluorescent component 1 to fluorescent component 3 at the normalized density under the reference exposure conditions. Furthermore, in accordance with the change in any of the exposure condition items, the fluorescent-component-density computation unit13d2may multiply the ratio of the values after the change of the changed exposure condition items to the values of the exposure condition items under the reference exposure conditions by the UNMIXING coefficients under the reference exposure conditions. It is possible to apply the fluorescence-endoscope apparatus of the present invention to the detection of fluorescent components in various combinations, including a plurality of human tissues alone, a plurality of fluorescence agents alone, or residues.

INDUSTRIAL APPLICABILITY

The fluorescence-endoscope apparatus of the present invention is effective in the fields of detecting the fluorescence spectra produced from biological tissue in order to observe the biological tissue.