JP2001137175A - Fluorescence image acquisition method and equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a self-fluorescence image with an excellent S/N ratio generated from measuring object located at a remote site in biological tissue using fluorescence image acquisition method and equipment. SOLUTION: In the case that of self-fluorescence Kj generated from biological tissues 1 by irradiation of excitation light Le is taken by an image sensor 25 and the taken Kj is read out as an image, read-out frequency of the image sensor 25, area per pixel, total number of pixels, pixel binning number, read-out port number, exposure time, quantum efficiency, electronic multiplication factor and device temperature are set to meet the following formula to obtain images. RN+DN<0.22×P×H×G, herein RN: number of charge generated by exposure noise (determined by read-out frequency and area per pixel), DN: number of charge generated by dark noise (determined by read-out frequency, area per pixel, total number of pixels, pixel binning number, read-out port number, exposure time, quantum efficiency, electronic multiplication factor and device temperature), P: irradiation output (mW) of excitation light, H: quantum efficiency of imaging element and G: electronic multiplication factor of image sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for acquiring a fluorescence image as an image of auto-fluorescence generated from a living tissue irradiated with excitation light.

[0002]

2. Description of the Related Art Conventionally, auto-fluorescence generated from an endogenous dye in a living tissue by irradiation with excitation light has been imaged as an image.
A device for analyzing a change in tissue properties associated with various diseases by analyzing the captured autofluorescence image has been studied.

[0003] Autofluorescence generated from a living tissue is weak, and a high-sensitivity image pickup device is used to detect the weak autofluorescence as an image. For example, signal charges of a plurality of pixels are stored in a CCD chip. A reading method using a high-sensitivity CCD capable of performing pixel binning for reading out by integrating is used, or autofluorescence is imaged using an electron multiplying type image pickup device such as an ICCD.

[0004]

In the case where a living tissue such as a body cavity having a complicated shape is irradiated with excitation light and a fluorescent image generated by autofluorescence generated from the living tissue is obtained using, for example, an endoscope or the like. There is a request to capture, at S / N = 1 or more, autofluorescence emitted from a cancer tissue located at a position (distant point) 50 mm away from the tip of a measurement probe of an endoscope apparatus.

[0005] However, even if the method of performing pixel binning is used, when signal charges generated in a plurality of pixels receiving autofluorescence are integrated in the CCD chip, the signal charges accumulated in the pixels to be pixel-binned are accumulated. The charge generated by dark noise included in the signal charge is also integrated at the same time.

Accordingly, since the auto-fluorescence generated from the cancer tissue is extremely weak, the number of charges generated by dark noise may be larger than the number of charges generated by receiving the auto-fluorescence in each pixel. In such a case, even if signal charges accumulated in a plurality of pixels are pixel-binned and integrated, the signal level of auto-fluorescence generated from cancer tissue becomes smaller than the signal level of dark noise, and S / N Is lower than 1 without improvement. Even if an electron multiplying type image pickup device is used, if the setting of the image pickup device is insufficient, unnecessary dark noise and readout noise are generated, and the auto-fluorescence emitted from the cancer tissue located at the above position is reduced to S. In some cases, imaging cannot be performed with / N = 1 or more.

Further, there is a demand for capturing an image of auto-fluorescence emitted from a normal tissue located at a position (near point) 5 mm away from the tip of the measurement probe of the endoscope device so that the light receiving capacity of the imaging device is not saturated. There is also.

However, the dynamic range of an electron multiplying type image pickup device such as an ICCD is less than two digits, and if the setting of the image pickup device is insufficient, the light receiving capacity of the image pickup device is saturated, and the pixel binning is difficult. In this method, even if the number of pixels to be subjected to pixel binning is reduced for pixels in an area where the amount of received light is large and the number of pixels according to the amount of received light is set as an object of pixel binning and imaging is performed, the setting of the image sensor is also changed. If it is insufficient, a problem occurs that the light receiving capacity of the imaging device is saturated.

The first invention has been made in view of the above circumstances, and it is an object of the present invention to acquire an image of autofluorescence generated from a measurement target site of a living tissue at a distant point with good S / N. It is an object of the present invention to provide a method and an apparatus for acquiring a fluorescent image, which can obtain an image of auto-fluorescence generated from a measurement target site of a living tissue existing at a near point by a receiving device of an imaging device. An object of the present invention is to provide a method and an apparatus for acquiring a fluorescent image which can be acquired without saturating the capacity.

[0010]

According to a first aspect of the present invention, there is provided a fluorescence image acquiring method, wherein an autofluorescence generated from a living tissue irradiated with excitation light is imaged by an imaging device, and the imaged autofluorescence is read as an image. In the fluorescent image acquisition method, the readout frequency, the area of one pixel, the total number of pixels, the number of pixel binning, the number of readout ports, the exposure time, the quantum efficiency, the electron multiplication factor, and the device temperature of the image sensor satisfy the following conditional expressions. And acquiring the image.

RN + DN <0.22 × P × H × G In a second method of acquiring a fluorescence image of the present invention, an image pickup element picks up an autofluorescence generated from a living tissue irradiated with excitation light, In a fluorescence image acquiring method for reading fluorescence as an image, a reading frequency of the imaging device, an area of one pixel, a total number of pixels, a number of pixel binning, a number of reading ports, an exposure time, a quantum efficiency, an electron multiplication factor, an element temperature, a floating diffusion And the capacity of the full well is set so as to satisfy the following conditional expression to acquire the image.

(RN + DN) × 1000 × G <Fd (RN + DN) × 1000 × G <Fw The first fluorescent image acquisition apparatus of the present invention irradiates a living tissue with excitation light to generate a self-generated light from the living tissue. In a fluorescence image acquiring apparatus including an image pickup device for picking up fluorescent light and reading means for reading out the picked-up auto-fluorescence as an image, the readout frequency of the image pickup device, the area of one pixel, the total number of pixels, the number of pixel binning, the readout The number of ports, exposure time, quantum efficiency, electron multiplication factor, and element temperature are set so as to satisfy the following conditional expression.

RN + DN <0.22 × P × H × G The second aspect of the present invention provides a fluorescence image acquiring apparatus which irradiates a living tissue with excitation light to image autofluorescence generated from the living tissue. A reading means for reading the captured autofluorescence as an image, wherein the reading frequency of the image sensor, the area of one pixel, the total number of pixels, the number of pixel binning, the number of reading ports, the exposure time, the quantum The efficiency, the electron multiplication factor, the element temperature, the capacity of the floating diffusion and the capacity of the full well are set so as to satisfy the following conditional expression.

(RN + DN) × 1000 × G <Fd (RN + DN) × 1000 × G <Fw The read frequency of the image sensor can be set so as to satisfy the condition of RN = DN.

The image pickup device is a CCD type image pickup device or MO
An S-type imaging device can be used.

In the above, RN is the number of charges generated by the read noise (the read frequency and
DN: Number of charges generated by dark noise (read frequency)
Number, area of one pixel, total number of pixels, number of pixel binning,
Determined by the number of output ports, exposure time and device temperature
Value) P: Irradiation output of excitation light (mW) H: Quantum efficiency of the image sensor G: Electron multiplication factor of the image sensor Fd: Corresponding to the capacity of floating diffusion
Fw: the number of charges corresponding to the capacity of the full well RN = 0.17S^0.777× f^1/2 DN = (tread + texp) × S × n × e^{d (T)} tread = (N / n) / (f × 10⁶× M) + ((n−
1) × (N / n)) / (f × 10⁷× M) d (T) = 4.1913 × 10^-6× (273 + T)³
-3.8015 x 10 ^-3× (273 + T)²+1.2
197 × (273 + T) -136 S: area of one pixel (μm²F: readout frequency (megapixel / sec) N: total number of pixels n: number of pixels to be subjected to pixel binning M: number of readout ports texp: exposure time (sec) T: temperature of image sensor (° C.)

The "image" is a normal one-frame one-frame image.
In addition to images acquired continuously every 30 seconds, even if the movement of the imaged image cannot be observed as a smooth movement, it is acquired so that the measurement target site can be observed continuously. For example, an image including an image captured at 1/10 second per frame.

The "number of charges corresponding to the capacitance" is a value obtained by converting the capacitance Fd of the floating diffusion and the capacitance Fw of the full well into the number of charges in order to make the unit of the above equation equal to the number of charges. is there.

The present invention is a combination of the first and second inventions, that is, the above three formulas, RN
+ DN <0.22 × P × H × G and (RN + DN) × 1
000 × G <Fd and (RN + DN) × 1000 × G <
Fw, the readout frequency of the image sensor, the area of one pixel, the total number of pixels, the number of pixel binning, the number of readout ports, the exposure time, the quantum efficiency, the electron multiplication factor, the device temperature, the capacity of the floating diffusion and It also includes a method and an apparatus for acquiring an image by setting the volume of a full well.

[0020]

According to the first method and apparatus for acquiring a fluorescence image of the present invention, when acquiring the autofluorescence imaged by the image sensor as an image, the image sensor is subjected to the conditional expression: R
Since the setting is made so as to satisfy N + DN <0.22 × P × H × G, compared to the number of electric charges generated in the image pickup device due to the reception of the auto-fluorescence generated from the measurement target site, the image pickup device uses dark noise and readout noise. By suppressing the number of electric charges generated at a low level, a fluorescent image can be obtained with good S / N.

According to the fluorescence image acquiring method and apparatus of the second aspect of the present invention, when acquiring the autofluorescence imaged by the image sensor as an image, the image sensor is subjected to the conditional expression (R
(N + DN) × 1000 × G <Fd and (RN + DN)
× 1000 × G <Fw
The capacity of the floating diffusion and the capacity of the full well of the imaging device are sufficiently large compared to the number of charges generated in the imaging device due to dark noise and readout noise. As a result, the fluorescence image is adjusted so that the light receiving capacity of the imaging device is not saturated. Can be obtained.

When the read frequency f of the image sensor is RN = D
If the setting is made so as to satisfy the condition of N, the sum of the number of charges generated by dark noise and the number of charges generated by read noise can be minimized.

If the image pickup device is a CCD type image pickup device or a MOS type image pickup device, the space for mounting the image pickup device can be reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment in which a fluorescent image acquiring apparatus that performs the fluorescent image acquiring method of the present invention is applied to a fluorescent endoscope apparatus.

The fluorescence endoscope 800 has a wavelength of 410 nm.
A light source unit 100 that emits the excitation light Le, and the excitation light emitted from the light source unit 100 is applied to the living tissue 1 through the optical fiber 21 to generate the self-generated light from the living tissue 1 that has been irradiated with the excitation light Le. Fluorescence Kj is applied to the image sensor 25
An endoscope unit 200 that captures an image and outputs it as an image signal via a cable 26, an image signal reading unit 300 that reads an image signal from the endoscope unit 200, converts the image signal into a video signal, and outputs the video signal, and outputs the image signal from the image signal reading unit 300. The display device 400 is configured to receive the video signal thus input and display it as an image.

The endoscope unit 200 includes the light source unit 1
00 and the image signal reading unit 300, an operating unit 202, an irradiation lens 22 for irradiating the living tissue 1 with the excitation light Le, and an image of the living tissue 1 due to autofluorescence generated from the living tissue 1 (hereinafter an autofluorescent image) Zj) is formed on the imaging element 25 via the prism 24 on the imaging element 25 and the like.
The optical fiber 21 and the cable 26 are laid from the operation unit 202 to the measurement probe unit 201. Note that an excitation light cut filter that blocks light having a wavelength of 410 nm is integrally provided on the light receiving surface of the image sensor.

Next, the fluorescence endoscope apparatus 8 having the above configuration
The operation of 00 will be described. The excitation light Le emitted from the light source unit 100 enters the end face 21a of the optical fiber 21, propagates through the optical fiber 21, and is emitted from the other end face 21b. The excitation light Le emitted from the end face 21b is emitted by the irradiation lens 22 as excitation light having an output of 100 mw spread at an angle of about 120 °. The auto-fluorescent image Zj generated from the living tissue 1 by the irradiation of the excitation light Le passes through the imaging lens 23 to the prism 2
4 and is reflected at substantially right angles to form an image on the image sensor 25. At this time, the excitation light Le is blocked by the excitation light cut filter integrated with the light receiving surface of the image sensor, and only the autofluorescence is received by the image sensor. Image sensor 2
The auto-fluorescent image Zj formed on the image 5 is picked up by the image pickup device 25 and converted into an electric image signal.
The image signal is read by the image signal reading unit 300 via the interface, is converted into a video signal by the image signal reading unit 300, is output, and is displayed on the display 400.

Next, the auto-fluorescence generated within the measurement range from the near point to the far point due to the irradiation of the excitation light is reduced to a sufficient S / N.
Now, a method of setting conditions for enabling the light receiving capacity of the imaging device to be obtained without saturation will be described.

That is, the intensity of the auto-fluorescence of the cancer tissue generated in the measurement target area at the distant point by the irradiation of the excitation light is expressed by S / N =
A method for setting an image sensor using the following equation (1) to obtain at least one auto-fluorescence generated at a near point can be obtained without saturating the light receiving capacity of the image capturing apparatus. A setting method of the imaging device using the following equations (2) and (3) will be described.

RN + DN <0.22 × P × H × G Equation (1) (RN + DN) × 1000 × G <Fd Equation (2) (RN + DN) × 1000 × G <Fw Equation (3) RN: Number of charges generated by read noise DN: Number of charges generated by dark noise (due to dark current
P: Irradiation output of excitation light (mW) H: Quantum efficiency of the imaging device G: Electron multiplication factor of the imaging device Fd: Corresponding to the capacity of floating diffusion
Fw: the number of charges corresponding to the capacity of the full well where RN = 0.17S^0.777× f^1/2 DN = (tread + texp) × S × n × e^{d (T)} tread = (N / n) / (f × 10⁶× M) + ((n−
1) × (N / n)) / (f × 10⁷× M) d (T) = 4.1913 × 10^-6× (273 + T)³
-3.8015 x 10 ^-3× (273 + T)²+1.2
197 × (273 + T) -136 S: area of one pixel (μm²F: readout frequency (megapixel / sec) N: total number of pixels n: number of pixels to be binned M: number of readout ports texp: exposure time (sec) T: temperature of image sensor (° C.) First, equation (1) Will be described. For fluorescent endoscope
The first image acquisition condition requested is a measurement probe unit.
Cancer tissue at a position 50 mm away from the tip of 201
Is irradiated with 410 nm excitation light Le
Image auto-fluorescence emitted from tissue at S / N = 1 or higher
Specifically, as shown in FIG.
Light L having an irradiation output of 100 mw from the emission point Q of the laser 22
When e is emitted at a spread angle of 120 degrees, the emission point
Developed from cancer tissue located at position B 50 mm away from Q
Autofluorescence Kj to be acquired as an image with S / N = 1 or more
Is Rukoto.

The power density of the excitation light irradiated to the position B by the above setting is 0.004 (mW / mm ² ) as shown by the point b1 in the log-log graph of FIG. When the auto-fluorescence Kj generated from the cancer tissue by the irradiation of the light is imaged on the pixels of the image pickup device 25 by the image forming lens 23 and is imaged with an exposure time of 1/30 second, for example, the quantum efficiency and When the electronic image magnification is 1 and the area of one pixel is 10 μm ² , the number of charges stored in the pixel is approximately 22, and the 22 charges are S / S
To read with N = 1 or more, it is necessary to make the number of noise charges read from the same pixel less than 22.

In order to further generalize the above setting, when the quantum efficiency and the electron image magnification of the imaging device are 1 at an irradiation power of 100 mw of the excitation light, the area of one pixel or the number of pixel binning handled as one pixel is reduced. Even if it changes, S / N = 1
As described above, it is assumed that the minimum number of charges read out from one pixel (corresponding to one pixel) is fixedly 22 and the same one pixel (corresponding to one pixel)
Is set so that the sum of the charges due to the dark noise and the readout noise generated from is less than 22.

When the irradiation output P of the excitation light, the quantum efficiency H of the image sensor, and the electron multiplication factor G are used as variables based on the above settings, one pixel (1) to be read out at S / N = 1 or more is used. 22 × (P / 100) × H × G = 0.22 × P ×
H × G (pieces), which is the right side of equation (1).

Specifically, the irradiation output is 100 mW, and C
An image is captured by front exposure using a CD image sensor, and the quantum efficiency and the electronic image magnification of the image sensor are each H = 0.4.
And G = 1, the 1
The minimum set number of charges stored in a pixel (corresponding to one pixel) is
0.22 × 100 × 0.4 × 1 = 8.8. Hereinafter, the minimum set number 8.8 of the electric charge accumulated in one pixel (corresponding to one pixel) read at the S / N = 1 or more will be rounded to 10 for simplification.

Next, the left side of equation (1) will be described.
When an autofluorescence image is captured by front exposure using a CCD image sensor as described above, the sum of the number of charges of dark noise generated from one pixel (corresponding to one pixel) and the number of charges of readout noise is calculated. It is necessary to suppress it to less than 10. There are various combinations of settings that satisfy this condition, and the settings can be made in the following manner.

For example, when front exposure is performed using a CCD image pickup device, T = 20 (° C.) and N = 250,000.
(Pieces), n = 16 (pieces), f = 1 (megapixel / se
c), M = 1 (port) and texp is 1/10, 1 /
30, 1/100, and 1/300 (second) are set in stages, and the value of the area S of one pixel and the dark noise of one pixel when the area of one pixel is changed from S = 1 to 100 (μm ² ). The relationship between the sum of the number of charges and the sum of the number of charges of the readout noise (DN + RN) (hereinafter referred to as the total number of noise charges DRN) is shown in FIG. 4 in which the X axis is the area S of one pixel and the Y axis is the total number of noise charges DRN. The graph has such a configuration that the range of the setting in which the total number of noise charges DRN generated from one pixel (corresponding to one pixel) can be suppressed to less than 10 is a range of Y <10 indicated by Area1. More specifically, for example, t shown at point u1
A set value where DRN = 6 (exp) at exp = 1/300 (second) and S = 5 (μm ² ), or texp = 1/100 (second) and S = 6.5 (μm) indicated at point u2
² ) In DRN = 9 (number), or texp = 1/30 (second) and S = 2 indicated at point u3
It is shown as a set value or the like at which DRN = 4 (μm ² ).

As another example, when front exposure is also performed using a CCD image pickup device, T = 20
(° C.), N = 250,000 (pieces), n = 16 (pieces),
M = 1, 2, 4, and 8 (ports), S = 10 (μ
m ² ), t exp is set to 1/100 (second), and the value of the read frequency f and the total number of noise charges DRN when the read frequency is changed from f = 0.1 to 100 (megapixels / sec) The relationship with the value is a graph as shown in FIG. 5 in which the X-axis is the read frequency f and the Y-axis is the total number of noise charges DRN, and the total number of noise charges generated for one pixel is suppressed to less than 10. The range of possible settings is a range of Y <10 indicated by Area2. More specifically, for example, the point v1
The setting value that becomes DRN = 6 (number) at M = 8 (port) and f = 5 (megapixel / sec) shown in FIG.
Or M = 2 (port) and f = 1 shown at point v2
(Megapixels / sec) at DRN = 9, or at DR = 1 at M = 1 (port) and f = 10 (Megapixels / sec) shown at point v3
7 and so on.

Further, as another example, similarly, when front exposure is performed using a CCD image pickup device, T = 0, 1
0, 20 (° C.), N = 250,000 (pieces), n = 16
(Number), M = 1 (port), texp is set to 1/30 (second), and the area S of one pixel is S = 10 to 100 (μ).
m ² ) in steps of 10 (μm ² ), and the readout frequency f is changed from f = 0.1 to 20 (megapixels / sec).
c, the relationship between these values and the total number of noise charges DRN is shown in FIG. 6, FIG. 7, and FIG. It becomes a three-dimensional graph in which the Z axis is set as the total number of noise charges DRN,
The setting range in which the total number of noise charges DRN generated for one pixel can be suppressed to less than 10 is Area 3 in FIG.
a, a range indicated by a solid line below the plane of Z = 10 shown in Area 3b of FIG. 7 and Area 3c of FIG. FIG. 6 shows T = 0 (° C.), FIG. 7 shows T = 10 (° C.), and FIG.
Is a graph when T = 20 (° C.) is set.

As shown in Area 3a of FIG. 6, T = 0
In the case of (° C.), the range of settings that can suppress the total number of noise charges DRN generated for one pixel to less than 10 is wide, and various combinations of values can be selected. = 10 (° C.), the Are of FIG.
As shown by a3b, the range becomes narrower, and when the temperature of the image sensor becomes T = 20 (° C.), the range of setting that can suppress the total noise charge number DRN to less than 10 as shown by Area3c in FIG. Narrows.

As described above, various combinations can be selected for the setting that satisfies the condition of the above equation (1) for suppressing the total number of noise charges DRN generated for one pixel to less than ten.

Incidentally, in a fluorescence endoscope apparatus of a system in which autofluorescence is imaged by forming an image directly on the image sensor without relaying the image fiber, the size of the image sensor is Focus × tan θ = D / 2 · ··· Restriction given by equation (4).

Here, Focus: focal length of the imaging lens θ: 50 to 60 (deg) D: length of diagonal line of the image sensor That is, if D is determined, the total number of pixels Since the relationship between N and the area S of one pixel is also limited, a range that satisfies the expression (4) is further selected from the ranges shown in the above example, and each set value of the image sensor is obtained.

When an image is taken by back exposure using a CCD image pickup device, the quantum efficiency becomes H = 0.9, which is about twice the quantum efficiency of front exposure, so that the total noise charge number DRN is about 20%. What is necessary is just to set each value so that it may become less than.

Next, equations (2) and (3) were used to enable the intensity of the autofluorescence generated at the near point to be detected as an image without saturating the light receiving capacity of the imaging device. The setting method of the image sensor will be described.

The second image acquisition condition required for the fluorescence endoscope is that a normal tissue existing at a position 5 mm away from the tip of the measurement probe is irradiated with excitation light Le having a wavelength of 410 nm from the normal tissue. This is to image the emitted autofluorescence without saturating the light receiving capacity of the pixel of the image sensor. Specifically, as shown in FIG. 2, the excitation light Le having an output of 100 mw from the emission point Q of the irradiation lens 22 is generated. When emitted at a spread angle of 120 degrees, autofluorescence K generated from normal tissue located at a position A 5 mm away from the emission point Q
j is to acquire an image so as not to saturate the light receiving capacity of the imaging device.

As shown in FIG. 3, the power density of the excitation light applied to the position A by the above setting (point a1 in FIG. 3)
Is the power density of the pump light at position B (point b in FIG. 3).
It is 0.4 (mW / mm ² ), which is 100 times as large as 1), and the autofluorescence Kj generated from the normal tissue of the living body when irradiated with the excitation light having this power density is used to image the cancer tissue at the position B described above. As in the case described above, the imaging device 25 is
When an image is formed on an image with an exposure time of 1/30 ^second , the number of charges (signal charges) accumulated in a pixel having an area of 10 μm ² of one pixel of an image sensor having a quantum efficiency of 1 and an electronic image magnification of 1 is , About 22,000, which is 1,000 times the number of signal charges generated in one pixel when the cancer tissue at the position B is imaged (normal tissue is cancerous by irradiation with excitation light having the same power density). It generates autofluorescence about 10 times as strong as the tissue, and the power density of the irradiated excitation light is 100 times, which is 1,000 times.

That is, when the electron multiplication factor G is 1, the noise generation amount of 1,00
The light receiving capacity of the imaging device exceeding 0 times is required, and the dynamic range of the imaging device exceeds 1: 1,000.

When the fluorescence endoscope apparatus is actually used, the above-mentioned cancer tissue at the far point is acquired as an image with S / N = 1 or more, and the normal tissue at the near point is contained within the light receiving capacity of the imaging device. Since it is necessary to secure a dynamic range, the setting of the imaging device is performed so as to satisfy the condition of the expression (1) and the expressions (2) and (3). However, the number of charges Fd corresponding to the capacitance of the floating diffusion is related to the readout frequency f, and the number of charges Fw corresponding to the capacity of the full well is a value related to the area S of one pixel. These values cannot be determined independently. Therefore,
Specific means for setting the imaging device so as to satisfy the conditions of Expressions (2) and (3) in addition to Expression (1) include:
The setting range of the image sensor that satisfies the first image acquisition condition, that is, the expression (1), is obtained by using the graphs shown in FIGS. 4 to 8 and the like. The first image acquisition condition and the second image acquisition condition are selected by selecting a set value of the image sensor that satisfies the condition of (1), that is, a set value capable of securing a dynamic range exceeding 1: 1,000. Can be obtained. That is, it is possible to obtain the set value of the image sensor that satisfies the equations (1), (2) and (3).

Further, the set value T of the temperature of the image sensor is further fixed in the set range of the image sensor obtained as described above, and the read frequency f is set so as to satisfy the condition of RN = DN.
Is selected, the first image acquisition condition and the second image acquisition condition are satisfied under the condition of the set value T of the temperature of the imaging element, and the value of the total number of noise charges DRN is minimized. it can.

Further, if the image pickup device is a CCD type image pickup device or a MOS type image pickup device, the mounting space for the image pickup device can be reduced, and the CCD type image pickup device can be used for both front exposure and rear exposure. Can be used.

In the above embodiment, the above equation (1)
Although the image capturing apparatus is set so as to satisfy the conditions (2) and (3) and the image is obtained, the present invention is not limited to such an embodiment, and only the above equation (1) is used. The image acquisition may be performed by setting the imaging device so as to satisfy the following. Alternatively, the image acquisition may be performed by setting the imaging device so as to satisfy Expressions (2) and (3) above. Is also good. In the former case, by doing so, the effect is obtained that at least the cancer tissue at the distant point can be acquired as an image with S / N = 1 or more, and in the latter case, at least 1: 1,000 dynamic dynamics can be obtained. The effect of securing the range is obtained.

As described above, according to the present invention, an image of autofluorescence generated from a measurement target site located at a far point can be acquired with good S / N, and an image of autofluorescence can be acquired from a measurement target site located at a near point. An image of the generated autofluorescence can be acquired without saturating the light receiving capacity of the imaging device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fluorescence endoscope apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an irradiation range of excitation light.

FIG. 3 is a diagram illustrating a relationship between a distance to a subject and a power density of excitation light.

FIG. 4 is a diagram showing the relationship between the total number of noise charges DRN and the area S of one pixel;

FIG. 5 is a diagram showing a relationship between a total number of noise charges DRN and a read frequency f.

FIG. 6 is a diagram showing a relationship among a total number of noise charges DRN, a read frequency f, and an area S of one pixel.

FIG. 7 is a diagram showing the relationship between the total number of noise charges DRN, the read frequency f, and the area S of one pixel.

FIG. 8 is a diagram showing the relationship between the total number of noise charges DRN, the read frequency f, and the area S of one pixel.

DESCRIPTION OF SYMBOLS 1 Living tissue 21 Optical fiber 22 Irradiation lens 23 Imaging lens 24 Prism 25 Image sensor 26 Cable 100 Light source unit 200 Endoscope unit 201 Measurement probe unit 202 Operation unit 300 Image signal reading unit 400 Display 800 Fluorescence Endoscope device Le Excitation light Kj Autofluorescence

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H04N 7/18 H04N 7/18 MF term (Reference) 2G043 AA03 BA16 CA03 EA01 GA08 GB21 HA01 HA05 JA05 KA05 LA03 MA04 NA01 NA06 2H040 GA02 GA11 4C061 AA00 BB00 CC06 DD00 FF40 JJ17 LL02 NN01 PP02 PP12 QQ04 QQ09 RR02 RR14 RR22 SS18 5C024 AX00 CX03 GY01 5C054 AA01 CA00 CC02 CC07 CG08 CH01 EA05 FC05 HA05 FC05 HA05

Claims (7)

[Claims] 1. A fluorescence image acquiring method in which an auto-fluorescence generated from a living tissue irradiated with excitation light is imaged by an imaging device, and the auto-fluorescence thus imaged is read as an image. Area, total number of pixels,
A fluorescent image acquiring method, wherein an image is acquired by setting the number of pixel binning, the number of readout ports, the exposure time, the quantum efficiency, the electron multiplication factor, and the element temperature so as to satisfy the following conditional expression. RN + DN <0.22 × P × H × G where RN: number of charges generated by readout noise DN: number of charges generated by dark noise P: irradiation power of excitation light (mW) H: quantum efficiency of image sensor G: Electron multiplication factor of image sensor 2. A fluorescence image acquiring method in which autofluorescence generated from a living tissue irradiated with excitation light is imaged by an imaging device and the captured autofluorescence is read as an image. Area, total number of pixels,
An image is obtained by setting the number of pixel binning, the number of readout ports, the exposure time, the quantum efficiency, the electron multiplication factor, the element temperature, the capacity of the floating diffusion and the capacity of the full well so as to satisfy the following conditional expression. Fluorescent image acquisition method. (RN + DN) × 1000 × G <Fd (RN + DN) × 1000 × G <Fw where RN: Number of charges generated by read noise DN: Number of charges generated by dark noise Fd: Number of charges corresponding to the capacity of floating diffusion Fw : Number of charges corresponding to the capacity of the full well 3. A fluorescence image acquiring apparatus comprising: an image sensor for imaging autofluorescence generated from a living tissue by irradiating the living tissue with excitation light; and a reading unit for reading the autofluorescence imaged as an image. Readout frequency of the image sensor, area of one pixel, total number of pixels,
A fluorescent image acquisition apparatus, wherein the number of pixel binning, the number of readout ports, the exposure time, the quantum efficiency, the electron multiplication factor, and the element temperature are set so as to satisfy the following conditional expressions. RN + DN <0.22 × P × H × G where RN: number of charges generated by readout noise DN: number of charges generated by dark noise P: irradiation power of excitation light (mW) H: quantum efficiency of image sensor G: Electron multiplication factor of image sensor 4. A fluorescence image acquisition apparatus comprising: an imaging element for capturing autofluorescence generated from living tissue by irradiating the living tissue with excitation light; and reading means for reading the captured autofluorescence as an image. Readout frequency of the image sensor, area of one pixel, total number of pixels,
A fluorescent image acquisition characterized in that the number of pixel binning, the number of readout ports, the exposure time, the quantum efficiency, the electron multiplication factor, the element temperature, the capacity of the floating diffusion and the capacity of the full well are set so as to satisfy the following conditional expressions. apparatus. (RN + DN) × 1000 × G <Fd (RN + DN) × 1000 × G <Fw, where RN: number of charges generated by read noise DN: number of charges generated by dark noise G: electron multiplication factor of imaging element Fd: floating diffusion Fw: the number of charges corresponding to the capacity of the full well 5. The reading frequency of the image sensor is RN.
5. The fluorescence image acquiring apparatus according to claim 3, wherein the setting is made so as to satisfy the condition: = DN. 6. The fluorescence image acquiring apparatus according to claim 3, wherein said image pickup device is a CCD type image pickup device. 7. The fluorescence image acquiring apparatus according to claim 3, wherein said image sensor is a MOS type image sensor.