Patent Description:
For example, in the field of biochemistry, there are known imaging apparatuses by each of which a sample that emits light as a result of a chemical reaction is imaged as a subject, a sample that is labeled with a fluorescent substance and that is irradiated with excitation light so as to emit light is imaged as a subject, or a sample that is dyed by a CBB (Coomassie Brilliant Blue) pigment or the like and that is irradiated with transmitted light so as to develop a color is imaged as a subject.

An imaging apparatus described in Patent Document <NUM> obtains a histogram of pixel values in an image of a subject taken by pre-imaging, sets, as a background portion, a maximum peak of peaks appearing in the histogram, and sets, as a detection target, a minimum peak of the peaks. The imaging apparatus refers to table data representing a correspondence relation among a pixel value, a cooling temperature, an exposure time, and an SN ratio, and determines a light exposure time in which a reference SN ratio or more can be obtained, based on an SN ratio which is a ratio between the pixel value of the detection target and the pixel value of the background portion, which have been set in the image taken by pre-imaging. Then, the imaging apparatus performs main imaging in the determined light exposure time.

An imaging apparatus described in Patent Document <NUM> uses a nondestructive readable device to repeat short-time light exposure until light emission of a subject fades to a level as low as readout noise of the device.

In the imaging apparatus described in Patent Document <NUM>, the minimum peak appearing in the histogram of the pixel values in the image taken by the pre-imaging is automatically set as the detection target. According to imaging conditions of the pre-imaging, a peak not appearing in the histogram of the image taken by the pre-imaging may be included in the subject. In this case, the peak not appearing in the histogram cannot be imaged with a desired S/N in the main imaging. In addition, in the imaging apparatus described in Patent Document <NUM>, the light exposure time is determined as a light exposure time in which the reference SN ratio or more can be obtained. However, the SN ratio in the subject whose light emission fades may not reach the reference SN ratio.

In the imaging apparatus described in Patent Document <NUM>, the light exposure is repeated until the light emission of the subject fades to the level as low as the readout noise of the device. Accordingly, there is a fear that a subject whose light emission fades comparatively slowly, particularly, a subject that emits fluorescence may be exposed to light for a long time, causing waste of time.

An object of the present invention is to image a subject whose light emission or color development distribution is unknown, with a high S/N and in a suitable light exposure time.

According to an aspect of the present invention, there is provided an imaging system as claimed in claim <NUM>.

According to a second aspect of the present invention, there is provided an imaging method as claimed in claim <NUM>.

According to a third aspect of the invention, there is provided a program as claimed in claim <NUM>.

Further aspects of the invention are defined by the dependent claims.

Incidentally, the aforementioned program can be recorded and provided on a computer-readable non-transitory recording medium. Such a "computer-readable recording medium" includes, for example, an optical medium such as a CD-ROM (Compact Disc-Rom), a magnetic recording medium such as a memory card, etc. In addition, such a program can be also provided by downloading through a network.

According to the present invention, a subject whose light emission or color development distribution is unknown can be imaged with a high S/N and in a suitable light exposure time.

<FIG> shows an example of an imaging system for explaining an embodiment of the present invention.

The imaging system <NUM> is an imaging system which images a subject according to the subject, i.e. images the subject with excitation light radiated thereon or images the subject without the excitation light radiated thereon, to thereby acquire a photographic image of the subject. The subject is a sample which emits light as a result of a chemical reaction (hereinafter referred to as chemiluminescent sample) or is a sample which is labeled with a fluorescent substance and irradiated with the excitation light to thereby emit light (hereinafter referred to as fluorescent sample). In addition, in an example that is not according to the claims, the subject may be a sample which is dyed by a CBB (Coomassie Brilliant Blue) pigment or the like and irradiated with transmitted light to thereby develop a color (hereinafter referred to as transparent colorimetric sample). The imaging system <NUM> includes an imaging apparatus <NUM> which is an imaging unit, and a control apparatus <NUM> which is a control unit enabling the imaging apparatus <NUM> to perform imaging.

<FIG> shows the configuration of the imaging apparatus <NUM>.

The imaging apparatus <NUM> includes a housing <NUM>, an imaging portion <NUM>, incident light sources <NUM>, and a transmitted light source <NUM>.

The housing <NUM> receives a subject PS. The housing <NUM> is a box substantially shaped like a rectangular parallelepiped. The housing <NUM> has a lid <NUM> (see <FIG>) which can be opened and closed. The lid <NUM> is opened/closed by a user. The subject PS is received inside the housing <NUM> through an opening closed by the lid <NUM>. In a state in which the lid <NUM> is closed, external light is shielded so that the inside of the housing <NUM> becomes a dark room. A subject placement portion <NUM> is provided inside the housing <NUM>. The subject PS is placed on the subject placement portion <NUM>.

The imaging portion <NUM> images the subject PS. The imaging portion <NUM> is set on an upper face 120a of the housing <NUM>. The imaging portion <NUM> is placed above the subject PS placed on the subject placement portion <NUM>, and placed face to face with the subject PS. The imaging portion <NUM> has a lens portion <NUM> movable in an up/down direction (Z-direction). By the vertical movement of the lens portion <NUM>, the focus during imaging can be put on the subject PS.

The incident light sources <NUM> emit excitation light from diagonally above the subject PS toward the subject PS placed on the subject placement portion <NUM>. The transmitted light source <NUM> radiates transmitted light from below the subject PS toward the subject PS placed on the subject placement portion <NUM>. When the subject PS is a fluorescent sample, the excitation light is radiated from the incident light sources <NUM>. In addition, when the subject PS is a transparent colorimetric sample, the transmitted light is radiated from the transmitted light source <NUM>.

<FIG> shows the configuration of the imaging portion <NUM>.

The imaging portion <NUM> includes the lens portion <NUM>, an imaging device <NUM>, a signal processing portion <NUM>, a storage portion <NUM>, a communication portion <NUM>, and an imaging control portion <NUM> that generally controls operations of the lens portion <NUM>, the imaging device <NUM>, the signal processing portion <NUM>, the storage portion <NUM> and the communication portion <NUM>.

The communication portion <NUM> is connected to the control apparatus <NUM> through a wired or wireless network. An instruction transmitted from the control apparatus <NUM> to the imaging portion <NUM> is inputted to the imaging control portion <NUM> through the communication portion <NUM>. The imaging control portion <NUM> activates the respective portions such as the lens portion <NUM> based on the inputted instruction so as to perform imaging.

Although not shown, the lens portion <NUM> is, for example, configured to include a lens group made up of a plurality of optical lenses, a diaphragm adjusting mechanism, an automatic focus adjusting mechanism, etc. The lens group is provided movably in the Z-direction shown in <FIG>. The automatic focus adjusting mechanism moves the lens group in accordance with a distance between the subject PS and the imaging portion <NUM> so as to put the focus during imaging on the subject PS. The diaphragm adjusting mechanism changes an aperture diameter of a diaphragm so as to adjust a light quantity passing through the lens portion <NUM>. Light emitted from the subject PS forms an image on an imaging face of the imaging device <NUM> through the lens portion <NUM>. Incidentally, the lens portion <NUM> may include a zoom mechanism.

The imaging device <NUM> photoelectrically converts the subject image formed on the imaging face into signal charges. The imaging device <NUM> is, for example, an image sensor such as a charge coupled device (CCD) or a metal oxide semiconductor (MOS). The imaging device <NUM> converts the signal charges into an analog voltage signal through a not-shown charge-voltage conversion amplifier, and outputs the converted analog voltage signal.

The signal processing portion <NUM> applies various signal processings to the analog voltage signal outputted from the imaging device <NUM>. One of the signal processings is, for example, correlated double sampling processing. The correlated double sampling processing takes a difference between a feedthrough component level and an image signal component level included in an output signal for each pixel of the imaging device <NUM>, so as to reduce noise or the like included in the output signal for each pixel. The signal processing portion <NUM> converts an analog signal subjected to the signal processings such as the correlated double sampling processing into a digital signal, and outputs the converted digital signal.

The storage portion <NUM> stores the digital signal outputted from the signal processing portion <NUM> as photographic image data. The photographic image data stored in the storage portion <NUM> are transmitted from the communication portion <NUM> to the control apparatus <NUM>.

In the present example, the imaging portion <NUM> further includes a cooling device <NUM> for cooling the imaging device <NUM>. The cooling device <NUM> is a temperature-controllable device such as a Peltier device. The temperature of the cooling device <NUM> is controlled by the imaging control portion <NUM>. Dark current noise is a part of a noise component included in the output signal of the imaging device <NUM>. The dark current noise is generated due to electric charges accumulated in each pixel even in a state in which light is not incident on the imaging device <NUM>. In addition, readout noise is another part of the noise component included in the output signal of the imaging device <NUM>. The readout noise is generated due to thermal noise etc. of the charge-voltage conversion amplifier which converts the signal charges into the analog voltage signal. Both the dark current noise and the readout noise have temperature dependence. In the present example, the imaging device <NUM> is properly cooled by the cooling device <NUM> so that the dark current noise and the readout noise can be reduced.

<FIG> shows the configuration of the control apparatus <NUM>.

The control apparatus <NUM> includes an operating portion <NUM>, a display portion <NUM>, a storage portion <NUM>, a communication portion <NUM>, and a control portion <NUM> generally controlling operations of the operating portion <NUM>, the display portion <NUM>, the storage portion <NUM>, the communication portion <NUM> and the imaging apparatus <NUM>.

For example, the operating portion <NUM> accepts a user input for setting imaging conditions. For example, the display portion <NUM> displays an interface image used for the user input for setting the image conditions. In addition, the display portion <NUM> displays a subject image generated based on an image (hereinafter referred to as photographic image) taken by the imaging apparatus <NUM>. The operating portion <NUM> is, for example, constituted by a keyboard, a mouse, etc. The display portion <NUM> is, for example, constituted by a liquid crystal display (LCD) etc. An interface portion <NUM> is constituted by the operating portion <NUM> and the display portion <NUM>.

The storage portion <NUM> stores a control program and control data executed by the control portion <NUM>, and stores image data of the photographic image and image data of the subject image. The storage portion <NUM> is, for example, constituted by a storage medium such as a flash memory, a hard disk, an ROM (Read Only Memory) or an RAM (Random Access Memory).

The communication portion <NUM> is connected to the imaging portion <NUM>, the incident light sources <NUM>, and the transmitted light source <NUM> of the imaging apparatus <NUM> through the wired or wireless network. An instruction complying with the set imaging conditions is transmitted from the communication portion <NUM> to the imaging portion <NUM>, the incident light sources <NUM>, and the transmitted light source <NUM>. Further, the photographic image data transmitted from the imaging portion <NUM> are received by the communication portion <NUM>.

The control portion <NUM> operates in accordance with the control program stored in the storage portion <NUM> so as to generally control the operations of the operating portion <NUM>, the display portion <NUM>, the storage portion <NUM>, the communication portion <NUM> and the imaging apparatus <NUM>. In addition, the control portion <NUM> operates in accordance with the control program so as to also function as an image generating portion <NUM> for generating the subject image based on the photographic image, and also function as a region setting portion <NUM>, an SN ratio calculating portion <NUM>, a total light exposure time calculating portion <NUM>, and a saturation light exposure time calculating portion <NUM>. The functions of the respective processing portions of the image generating portion <NUM>, the region setting portion <NUM>, the SN ratio calculating portion <NUM>, the total light exposure time calculating portion <NUM> and the saturation light exposure time calculating portion <NUM> will be described later.

The hardware structure of the control portion <NUM> performing various processings as the image generating portion <NUM>, the region setting portion <NUM>, the SN ratio calculating portion <NUM>, the total light exposure time calculating portion <NUM> and the saturation light exposure time calculating portion <NUM> includes a CPU (Central Processing Unit) which is a general purpose processor, a programmable logic device (PLD) which is a processor capable of changing its circuit configuration after production such as an FPGA (Field Programmable Gate Array), a dedicated electric circuit which is a processor having a circuit configuration specially designed for executing specific processing such as an ASIC (Application Specific Integrated Circuit), etc..

Each of the processing portions of the image generating portion <NUM>, the region setting portion <NUM>, the SN ratio calculating portion <NUM>, the total light exposure time calculating portion <NUM> and the saturation light exposure time calculating portion <NUM> may be constituted by one processor of the aforementioned various processors, or may be constituted by a combination of two or more processors the same or different in type (e.g. a combination of the FPGAs or a combination of the CPU and the FPGA). In addition, the processing portions may be constituted by one processor.

<FIG> shows the outline of the imaging process executed by the control apparatus <NUM>.

The control apparatus <NUM> enables the imaging apparatus <NUM> to perform pre-imaging one or more times and main imaging one or more times following the pre-imaging. Here, the main imaging means imaging performed for obtaining a subject image for analysis, and the pre-imaging means imaging performed for obtaining information for setting imaging conditions of the main imaging such as an exposure time.

The control apparatus <NUM> sets imaging conditions of pre-imaging (step S1), enables the imaging apparatus <NUM> to perform the pre-imaging based on the set imaging conditions (step S2), and generates a subject image based on a photographic image or images taken by the pre-imaging to display the generated subject image on the display portion <NUM> (step S3).

Next, the control apparatus <NUM> sets a region-of-interest and a non-region-of-interest of the generated subject image (step S4), calculates an SN ratio (Signal-Noise ratio) which is a ratio of a signal component of a pixel value to a noise component of the pixel value based on the set region-of-interest and the set non-region-of-interest (step S5), and calculates a total light exposure time of the main imaging in which a preset reference SN ratio can be obtained, based on the SN ratio calculated for the one or more taken images (step S6).

The control apparatus <NUM> enables the imaging apparatus <NUM> to perform the main imaging based on the calculated total light exposure time (step S7), and generates a subject image based on a photographic image or images taken by the pre-imaging (step S8).

The steps of the aforementioned imaging process, and the functions carried out by the processing portions (the image generating portion <NUM>, the region setting portion <NUM>, the SN ratio calculating portion <NUM>, the total light exposure time calculating portion <NUM>, and the saturation light exposure time calculating portion <NUM>) of the control portion <NUM> in the steps will be described below.

The imaging conditions of the pre-imaging are set based on a user input. Preferably, a subject kind is set based on the user input, and detailed imaging conditions are automatically set by the control portion <NUM> in accordance with the set subject kind. For example, assume that a chemiluminescent sample, a fluorescent sample, and a transparent colorimetric sample are available as the subject kind. In this case, the subject kind is set as the chemiluminescent sample, the fluorescent sample or the transparent colorimetric sample based on the user input. Detailed imaging conditions for each subject kind are stored in advance in the storage portion <NUM>. The control portion <NUM> reads out the imaging conditions corresponding to the set subject kind from the storage portion <NUM>, and sets the read-out imaging conditions as the imaging conditions of the pre-imaging.

The imaging conditions for each subject kind are whether to radiate excitation light or not, whether to radiate transmitted light or not, a light exposure time, etc. A light exposure time suited for a subject exhibiting light emission or color development with standard intensity is used as the light exposure time. Incidentally, from the viewpoint of shortening the time required for the pre-imaging, binning may be applied to the imaging device <NUM>. The binning is to add up signal charges from a plurality of pixels in the imaging device <NUM> to thereby generate a pixel value of one pixel in a photographic image. Due to the Binning, sensitivity of the imaging device <NUM> can be enhanced so that the light exposure time can be shortened. In addition, the pre-imaging may be performed multiple times on a subject whose color development or light emission intensity is unknown while the light exposure time is made different from one pre-imaging to another.

<FIG> shows an example of the subject image generated by the pre-imaging.

In the example shown in <FIG>, light emission patterns of chemiluminescent samples or fluorescent samples obtained by a western blotting method are formed into an image. The western blotting method is a technique for separating the samples according to their molecular weights by electrophoresis, making a labeled antibody specifically binding to a detection target react to each sample, and detecting fluorescence or chemiluminescence used for the labeling, thereby detecting the detection target. In <FIG>, the light emission patterns of lanes <NUM> to <NUM> show the light emission patterns of the samples different from one lane to another. The detection targets included in the samples of the lanes can be detected and quantitatively determined based on the light emission patterns of the lanes and intensities of the light emissions.

The image generating portion <NUM> generates a subject image based on the photographic image or images taken by the pre-imaging. When the pre-imaging is performed only once, the photographic image taken by the one time of the pre-imaging is set as the subject image. When the pre-imaging is performed multiple times while the light exposure time is made different from one imaging to another, for example, a photograph image whose dynamic range is widest among the photographic images taken by the multiple times of the pre-imaging can be set as the subject image, and the dynamic range can be obtained from a histogram of pixel values in the photographic image. In addition, the photographic images may be added up or averaged by arithmetic or weighted averaging as the subject image. The subject image generated by the pre-imaging is displayed on the display portion <NUM>.

A region-of-interest ROI and a non-region-of-interest NROI of the subject image generated by the pre-imaging are set by the region setting portion <NUM>. The region-of-interest ROI is, for example, set based on a user input. The subject image obtained by the pre-imaging is displayed on the display portion <NUM>, and the user input for designating any region in the subject image as the region-of-interest ROI is made on the operating portion <NUM>. In addition, the region-of-interest ROI may be automatically set by the region setting portion <NUM>. For example, a region corresponding to a pixel value of another peak than a peak whose pixel value is smallest among peaks appearing in a histogram of pixel values in the subject image can be extracted, and the region-of-interest ROI can be automatically set as the extracted region. In a case where there are other peaks like the aforementioned other peak, for example, a peak whose pixel value is smallest among the other peaks may be selected.

The non-region-of-interest NROI may be set based on a user input, similarly to the region-of-interest ROI, or may be automatically set by the region setting portion <NUM>. For example, a region corresponding to the pixel value of the peak whose pixel value is smallest among the peaks appearing in the histogram of the pixel values in the subject image can be extracted, and the non-region-of-interest NROI can be automatically set as the extracted region.

In the subject image shown in <FIG>, a band B indicating presence of a detection target appears at a predetermined position in each of the lane <NUM>, the lane <NUM> and the lane <NUM>. However, such a band does not appear in the lane <NUM>. In this case, a possibility that the amount of the detection target included in the sample of the lane <NUM> is very small, and light emission of the sample of the lane <NUM> is feeble in comparison with the light exposure time of the pre-imaging may be considered. When the light emission of the sample is feeble in comparison with the light exposure time of the pre-imaging, the band which is present may be buried in noise so that the band cannot appear in the image.

In order to image the predetermined position of the lane <NUM> with a high SN ratio in main imaging, the region-of-interest ROI is set at the predetermined position of the lane L2 in the subject image shown in <FIG>. In addition, the non-region-of-interest NROI is set at a region between the lane <NUM> and the lane <NUM>, i.e. a region where the band is unlikely to be present.

The SN ratio of the region-of-interest ROI changes according to the light exposure time. The SN ratio changing according to the light exposure time is calculated by the SN ratio calculating portion <NUM>. Here, the SN ratio calculating portion <NUM> calculates the SN ratio in consideration of a chronological characteristic of light emission or color development of the subject. When the SN ratio changing according to the light exposure time is SN(t), a signal component of the pixel value in which the chronological characteristic of the light emission or the color development of the subject has been taken into consideration is S(t), and a noise component of the pixel value is N(t), the SN(t) can be expressed by the following expression. Incidentally, the chronological characteristic of the light emission or the color development of the subject is a characteristic representing the relation between the passage of time and the intensity of the light emission or the color development.

<FIG> shows a chronological characteristic of light emission intensity of chemiluminescence. <FIG> shows a chronological characteristic of light emission intensity of fluorescence.

As shown in <FIG>, the light emission intensity of the chemiluminescence may often attenuate exponentially in accordance with the following expression. This is because the light emission intensity of the chemiluminescence decreases as concentration of a reactant in an excited state decreases in accordance with the progress of a chemical reaction. <MAT> in which yα is a positive coefficient depending on concentration of a chemiluminescent substance, and k is a positive coefficient depending on a fading characteristic of light emission of the chemiluminescent substance.

As shown in <FIG>, the light emission intensity of the fluorescence is ideally kept constant in accordance with the following expression as long as excitation light is supplied. This is because the fluorescence is emitted without causing destruction of a fluorescent substance. <MAT> in which yβ is a positive coefficient depending on concentration of the fluorescent substance.

Incidentally, the light emission intensity of the fluorescence may attenuate according to the kind of the fluorescent substance. An attenuation rate of the light emission intensity of the fluorescence with respect to the passage of time is smaller than an attenuation rate of the light emission intensity of the chemiluminescence. Accordingly, the attenuating light emission intensity of the fluorescence can be approximated by the following linear function. <MAT> in which yγ is a positive coefficient depending on the concentration of the fluorescent substance, and a is a positive coefficient depending on a fading characteristic of light emission of the fluorescent substance.

Although now shown, color development intensity of a sample dyed by a CBB pigment or the like is constant, similarly to the light emission intensity of the fluorescence, or can be approximated by a linear function.

The coefficient k in the expression (<NUM>) can be obtained in advance for each chemiluminescent substance, and the coefficient a in the expression (<NUM>) can be also obtained in advance for each fluorescent substance and for each dyeing substance, and is stored in the storage portion <NUM>. Assume that the subject kind set in the step S1 is classified by used reagents (the chemiluminescent substance, the fluorescent substance and the dyeing substance). In this case, the SN ratio calculating portion <NUM> determines an attenuation function corresponding to the subject kind among the expressions (<NUM>) to (<NUM>) based on the set subject kind. Therefore, the SN ratio calculating portion <NUM> determines the coefficient k when the attenuation function is the expression (<NUM>), or determines the coefficient a when the attenuation function is the expression (<NUM>).

Based on pixel values in the region-of-interest ROI and/or the non-region-of-interest NROI in the subject image based on the pre-imaging, the SN ratio calculating portion <NUM> obtains the coefficient yα when the attenuation function is the expression (<NUM>), obtains the coefficient yβ when the attenuation function is the function (<NUM>), or obtains the coefficient yγ when the attenuation function is the expression (<NUM>). Thus, the SN ratio calculating portion <NUM> derives the attenuation function y. A signal component of the pixel value in the subject image based on the pre-imaging can be, for example, set as a difference between an average of the pixel values in the region-of-interest ROI and an average of the pixel values in the non-region-of-interest NROI, as a difference between a median of the pixel values in the region-of-interest ROI and a median of the pixel values in the non-region-of-interest NROI, or as the average or the median of the pixel values in the region-of-interest ROI. Time integration of the derived attenuation function y corresponds to the signal component S(t) of the pixel value.

On the other hand, the noise component N(t) of the pixel value can be, for example, expressed by the following expression. <MAT> in which Nd is dark current noise of the imaging device <NUM>, Nr is readout noise of the imaging device <NUM>, and Nf is fixed pattern noise caused by a variation of sensitivity among the pixels of the imaging device <NUM>. These noises Nd, Nr and Nf are obtained in advance and stored in the storage portion <NUM>. In addition, the Ns is shot noise occurring due to a statistic change of photons incident on the imaging device <NUM>. When an amount of signal charges generated in the imaging device <NUM> due to the incidence of the photons is S[e-], the Ns can be expressed by the following expression in accordance with Poisson statistics.

The Ns is obtained based on the pixel values in the region-of-interest ROI and/or the non-region-of-interest NROI in the subject image based on the pre-imaging. For example, the Ns can be set as a standard deviation of the pixel values in the non-region-of-interest NROI or a standard deviation of the pixel values in the region-of-interest ROI.

A total light exposure time of the main imaging is calculated by the total light exposure time calculating portion <NUM>. The total light exposure time calculating portion <NUM> calculates the total light exposure time in which a preset reference SN ratio can be obtained, based on the SN(t) calculated by the SN ratio calculating portion <NUM>. In addition, when the light emission fades, the S(t) attenuates but the N(t) increases so that the SN(t) approaches the peak. When the SN(t) has the peak in this manner, and a maximum SN ratio which is the peak value of the SN(t) is smaller than the reference SN ratio, the total light exposure time calculating portion <NUM> calculates the total light exposure time in which the maximum SN ratio can be obtained.

The reference SN ratio can be, for example, set as a standard SN ratio required of a subject image for analysis, and is stored in the storage portion <NUM>. In addition, the reference SN ratio can be also set by the product of the SN ratio in the subject image used for setting the region-of-interest ROI and the non-region-of-interest NROI and an SN ratio improvement coefficient. For example, when the SN ratio in the subject image used for setting the region-of-interest ROI and the non-region-of-interest NROI is <NUM>, and the improvement coefficient is <NUM>, the reference SN ratio becomes <NUM> (<NUM>×<NUM>). The reference SN ratio improvement coefficient which provides the reference SN ratio is stored in the storage portion <NUM>.

<FIG> and <FIG> show an example of the SN ratio of the region-of-interest ROI changing according to the light exposure time.

<FIG> is a graph in which the SN(t) calculated by the SN ratio calculating portion <NUM> is shown with time as the abscissa and the SN ratio as the ordinate. The total light exposure time is obtained as a time T<NUM> in which a reference SN ratio SN<NUM> is provided in accordance with a characteristic line of the SN(t).

<FIG> shows a case where the SN(t) has a peak, and a maximum SN ratio SN<NUM> which is the peak value of the SN(t) is smaller than the reference SN ratio SN<NUM>. In this case, the total light exposure time is obtained as a time T<NUM> in which the maximum SN ratio SN<NUM> is provided, in accordance with a characteristic line of the SN(t).

On the other hand, when the maximum SN ratio SN<NUM> is not smaller than the reference SN ratio SN<NUM>, the total light exposure time may be obtained as the time T<NUM> in which the reference SN ratio SN<NUM> is provided or may be obtained as the time T<NUM> in which the maximum SN ratio SN<NUM> is provided. Preferably, a configuration is made so that one of the maximum SN ratio SN<NUM> and the reference SN ratio SN<NUM> to be used can be set based on a user input.

In addition, preferably, the total light exposure time calculated by the total light exposure time calculating portion <NUM> is displayed on the display portion <NUM>. Thus, the user can know the total light exposure time required for the main imaging so that user-friendliness of the imaging system <NUM> is enhanced.

In addition, preferably, the reference SN ratio can be set based on a user input. When the reference SN ratio is reset based on the user input, the total light exposure time calculating portion <NUM> recalculates the total light exposure time in which the reset reference SN ratio can be obtained. Thus, the user can set a desired reference SN ratio while taking the balance between the SN ratio and the total light exposure time. Consequently, the user-friendliness of the imaging system <NUM> is enhanced. In the resetting of the reference SN ratio based on the user input, the reference SN ratio may be designated directly or may be designated indirectly through the reference SN ratio improvement coefficient.

In addition, preferably, the SN(t) calculated by the SN ratio calculating portion <NUM> is displayed on the display portion <NUM>. The display form of the SN(t) is not limited particularly, but can be, for example, displayed as the graph shown in <FIG>. By the display of the SN(t), the user can easily grasp the relation between the SN ratio and the total light exposure time. Thus, the user can easily set a desired reference SN ratio while taking the balance between the SN ratio and the total light exposure time. Consequently, the user-friendliness of the imaging system <NUM> is further enhanced.

The control portion <NUM> enables the imaging apparatus <NUM> to perform the main imaging based on the total light exposure time calculated by the total light exposure time calculating portion <NUM>. Here, assume that the main imaging is performed only once. In this case, the imaging device <NUM> is exposed to light continuously in the total light exposure time. A photographic image taken by the one time of the main imaging is set as the subject image.

In the subject image obtained by the main imaging in the aforementioned manner, the region-of-interest ROI of the subject image is set based on a user input. The total light exposure time of the main imaging is set so that the SN ratio of the region-of-interest ROI can correspond to the reference SN ratio in the subject image based on the main imaging. Accordingly, for example, even a feeble band not appearing in the photographic image based on the pre-imaging can be captured at the reference SN ratio in the subject image based on the main imaging. Thus, a subject whose light emission or color development distribution is unknown can be imaged with a high S/N and in a proper light exposure time.

Incidentally, when the reference SN ratio is reset based on a user input, the total light exposure time of the main imaging is indirectly adjusted through the reference SN ratio. On the other hand, when the total light exposure time of the main imaging can be set based on a user input, the total light exposure time may be adjusted directly. When the total light exposure time can be set based on the user input, preferably, the control portion <NUM> enables the imaging apparatus <NUM> to perform the main imaging based on a shorter total light exposure time of the total light exposure time calculated by the total light exposure time calculated by the total light exposure time calculating portion <NUM> and the total light exposure time set based on the user input. Thus, when the calculated total light exposure time is comparatively short, the reference SN ratio can be obtained in a shortest time. When the set total light exposure time is comparatively short, the best SN ratio can be obtained within the total light exposure time allowed by the user. Thus, the user-friendliness of the imaging system <NUM> is further enhanced.

In addition, an upper limit of the total light exposure time of the main imaging may be set in advance. When the total light exposure time calculated by the total light exposure time calculating portion <NUM> or the total light exposure time set based on the user input exceeds the upper limit of the total light exposure time which has been set in advance, the imaging is preferable interrupted as soon as the light exposure time in the main imaging reaches the upper limit of the total light exposure time. The upper limit of the total light exposure time may differ from one subject kind to another. For example, in consideration of the fact that the light emission intensity of the fluorescence lasts longer than the light emission intensity of the chemiluminescence, the upper limit of the total light exposure time corresponding to a subject emitting the fluorescence may be set to be shorter than the upper limit of the total light exposure time corresponding to a subject emitting the chemiluminescence.

In addition, from the viewpoint of enhancing the user-friendliness of the imaging system <NUM>, the control portion <NUM> may interrupt the imaging when a user input for interrupting the imaging is accepted by the operating portion <NUM>.

The case in which the main imaging is performed only once has been described so far. However, the main imaging may be performed multiple times.

<FIG> shows a flow chart of an imaging process for the main imaging in the case where the main imaging is performed multiple times.

Assume that the main imaging is performed n times. In this case, the control portion <NUM> divides the total light exposure time into n segments (step S11). The number n of the segments is, for example, set based on a user input. The total light exposure time is, for example, divided into fixed light exposure times. The control portion <NUM> enables the imaging apparatus <NUM> to perform the main imaging n times (step S12) so that the imaging device <NUM> is exposed to light intermittently multiple times in accordance with the segments of the total light exposure time.

Here, the image generating portion <NUM> adds up n photographic images Pi taken by the n times of the main imaging, so as to generate a subject image I based on the main imaging and updates the subject image I whenever the main imaging is performed (step S13). A subject image Ik at a stage where the k-th main imaging has been performed is an image in which photographic images Pl to Pk have been added up as expressed by the following expression.

A pixel value in the region-of-interest ROI of the subject image In generated by adding up the n photographic images Pi is the simple sum of the Pi. On the other hand, in the subject image In, noise expressed by the expression (<NUM>) is an average of the sum of squares. Accordingly, the SN ratio of the region-of-interest ROI of the subject image In increases.

In addition, the photographic image Pi taken during the main imaging is added to the subject image Ii-<NUM> whenever the main imaging is performed. Accordingly, the SN ratio of the region-of-interest ROI increases gradually. Thus, the user can check whether the setting of the region-of-interest ROI is suitable or not without waiting for completion of the n times of the main imaging. Thus, the user-friendliness of the imaging system <NUM> is further enhanced.

Incidentally, in the case where the upper limit of the total light exposure time of the main imaging has been set in advance, imaging is preferably interrupted as soon as the total sum of the light exposure times added every time when imaging is performed reaches the upper limit of the total light exposure time which has been set in advance. In addition, an upper limit of a light exposure time per imaging may be set in advance, and imaging may be interrupted as soon as the light exposure time in any of the multiple times of the main imaging exceeds the upper limit of the light exposure time which has been set in advance. The upper limit of the light exposure time may differ from one subject kind to another, similarly to the upper limit of the total light exposure time. For example, the upper limit of the light exposure time corresponding to a subject emitting fluorescence can be set to be shorter than the upper limit of the light exposure time corresponding to a subject emitting chemiluminescence.

<FIG> are subject images taken by the main imaging on the same samples as those in the example shown in <FIG>. <FIG> is the subject image Ik at the stage where the k-th main imaging has been performed. <FIG> is a subject image Ik+<NUM> at a stage where the (k+<NUM>)th main imaging has been performed. <FIG> is a subject image Ik+<NUM> at a stage where the (k+<NUM>)th main imaging has been performed.

As the SN ratio of the region-of-interest ROI increases gradually, the band of the lane L2 that did not appear in the subject image Ik shown in <FIG> is gradually revealed in the image whenever the main imaging is performed. As a result, the band of the land L2 in the subject image Ik+<NUM> shown in <FIG> appears in the image to a visually recognizable level. Thus, the user can check whether the setting of the region-of-interest ROI is suitable or not without waiting for completion of the n times of the main imaging.

Here, in the example shown in <FIG>, the region-of-interest ROI which has been set is slightly displaced from the band B of the lane L2. In such a case, the imaging may be interrupted. However, it is desirable that the region-of-interest ROI is reset to agree with the band B of the lane L2 appearing in the subject image Ik+<NUM>.

Refer to <FIG> again. Whenever the subject image is updated, the control portion <NUM> displays the updated subject image on the display portion <NUM> (step S14). When a user input for designating any region in the subject image I displayed on the display portion <NUM> as the region-of-interest ROI is made on the operating portion <NUM> (Yes in step S15), the region setting portion <NUM> returns to the aforementioned step S4 (see <FIG>) to reset the region-of-interest ROI and the non-region-of-interest NROI.

The SN ratio calculating portion <NUM> recalculates the SN(t) based on the reset region-of-interest ROI and the reset non-region-of-interest NROI (the step S5). The total light exposure time calculating portion <NUM> recalculates the total light exposure time in which the reference SN ratio can be obtained, based on the recalculated SN(t) (the step S6). The control portion <NUM> enables the imaging apparatus <NUM> to perform the main imaging based on the recalculated total light exposure time (the step S7).

Thus, the region-of-interest ROI is allowed to be reset even during the main imaging. Accordingly, efficiency of the imaging process can be improved in comparison with a case where the imaging process is started over from the pre-imaging.

Here, there is a case where the SN ratio of the region-of-interest ROI in the updated subject image decreases due to attenuation of the light emission intensity or the color development intensity of the subject. Preferably, whether the change rate of the SN ratio is lower than a predetermined value or not is determined by the control portion <NUM> based on the change in the SN ratio. Therefore, the imaging is interrupted when the change rate of the SN ratio is lower than the predetermined value. When the imaging is interrupted due to the fact that the change rate of the SN ratio is lower than the predetermined value, preferably, of the subject images which have been generated till the interruption of the imaging, a subject image having a maximum SN ratio is displayed on the display portion <NUM> and stored. When, for example, the SN ratio of the region-of-interest ROI in the subject image Ik at the stage where the k-th main imaging has been performed is SNk, and n is an integer not smaller than <NUM>, the change rate of the SN ratio can be expressed by an inclination of a straight line which is obtained by linear approximation on SNk-n, SNk-(n+<NUM>),. When the change rate of the SN ratio is expressed by the inclination of the straight line obtained by the linear approximation on the SN ratios of the subject images, the predetermined value applied to the change rate of the SN rate is, for example, <NUM>. Of the subject images SNk-n, SNk-(n+<NUM>),. , SNk, the subject image which provides the maximum SN ratio is displayed on the display portion <NUM> and stored.

Incidentally, while the main imaging is performed, the total light exposure time calculated by the total light exposure time calculating portion <NUM> is preferably also displayed on the display portion <NUM>. In addition, the reference SN ratio can be preferably set based on a user input. When the reference SN ratio is reset based on the user input, the total light exposure time calculating portion <NUM> recalculates the total light exposure time in which the reset reference SN ratio can be obtained. In addition, the SN(t) calculated by the SN ratio calculating portion <NUM> is preferably displayed on the display portion <NUM>.

<FIG> shows another flow chart of the imaging process for the main imaging in the case where the main imaging is performed multiple times.

In the example shown in <FIG>, the image generating portion <NUM> obtains an arithmetic average of n photographic images Pi taken by n times of the main imaging so as to generate a subject image I based on the main imaging, and updates the subject image I whenever the main imaging is performed. A subject image Ik at a stage where the k-th main imaging has been performed is an image in which the photographic images Pl to Pk, have been arithmetically averaged as expressed by the following expression (step S23).

When the n photographic images Pi are arithmetically averaged, noise is also averaged among the n photographic images Pi. The noise is added at random to each of the pixels of the photographic images and further compressed due to the averaging, therefore leading to advantage to improvement of the SN ratio in the subject image I based on the main imaging.

When the n photographic images Pi are arithmetically averaged to generate the subject image I based on the main imaging, a shortest saturation light exposure time TS is preferably calculated by the saturation light exposure time calculating portion <NUM>. When the total light exposure time is divided into segments, the control portion <NUM> sets a number n of the segments and divides the total light exposure time into the n segments to make the light exposure time of any divided segment shorter than the saturation light exposure time TS. Incidentally, the shortest saturation light exposure time TS is a shortest time when a pixel whose pixel value has reached a saturation region appears in a photographic image taken by the main imaging. The shortest saturation light exposure time TS can be calculated based on one or more photographic images which have been taken by the pre-imaging and the main imaging. The saturation region is a region including an upper limit the pixel value can take and vicinities of the upper limit. In other words, the saturation region is a region where a proportional relation between photons incident on the pixel of the imaging device <NUM> and signal charges generated in the pixel is lost.

For example, in the examples shown in <FIG>, pixel values of pixels corresponding to the bands B of the lane L1, the lane L3 and the lane L4 increase whenever a photographic image is added. The pixel values of the pixels corresponding to the bands B of the lane L1 and the lane L3 in the subject image Ik shown in <FIG> have reached the saturation region. In this case, in each of the samples of the lane L1 and the lane L3, a detection target can be detected but cannot be quantitatively determined. On the other hand, the light exposure time in each of the n times of the main imaging is shorter than the saturation light exposure time TS. Accordingly, any pixel which has reached the saturation region does not appear in the n photographic images Pi and also does not appear in the subject image I which is generated by arithmetically averaging the n photographic images Pi. That is, the pixel values of the pixels corresponding to the bands B of the lane L1 and the lane L3 do not reach the saturation region, so that the detection targets can be detected and quantitatively determined in all the samples of the lanes L1 to L4 including the lane L2.

In addition, the light exposure time in each of the n times of the main imaging is preferably set to be longer as the main imaging is later.

<FIG> and <FIG> show a chronological characteristic of light emission in which intensity of the light emission attenuates with the passage of time, and a pixel value S(t) in the region-of-interest ROI in which the chronological characteristic of the light emission has been taken into consideration. <FIG> shows the pixel value obtained for each photographic image when the total light exposure time of the main imaging is divided into segments in which light exposure time is fixed. <FIG> shows the pixel value obtained for each photographic image when the total light exposure time of the main imaging is divided into segments in which light exposure time is set to be longer as the main imaging is later.

When the total light exposure time of the main imaging is divided into the segments in which the light exposure time is fixed as shown in <FIG>, a pixel value ΔSi obtained for each photographic image is smaller as the photographic image is taken by the later main imaging. In this case, noise is dominant in the photographic image taken by the later main imaging. There is a concern that the SN ratio may be lowered because the photographic image where the noise is dominant is included in the photographic images which will be added up and averaged.

On the other hand, the total light exposure time of the main imaging is divided into the segments in which the light exposure time is set to be longer as the main imaging is later, as shown in <FIG>. Accordingly, a pixel value ΔSi obtained for each photographic image is, for example, fixed so that the influence of noise can be averaged among the photographic images, therefore leading to advantage to improvement of the SN ratio. On this occasion, when the light exposure time of i-th imaging is ti and a weight in each imaging is <NUM>/ti, a subject image I based on the main imaging may be generated by weighted averaging the photographic images. That is, a subject image Ik at a stage where the k-th main imaging has been performed is an image in which the photographic images Pl to Pk have been weighted averaged as expressed by the following expression.

The present invention can be used for analysis of a subject emitting light or developing a color.

Claim 1:
An imaging system (<NUM>) comprising:
an imaging unit (<NUM>) configured to image a subject including light emission patterns of chemiluminescent samples or fluorescent samples that attenuate with time; and
a control unit (<NUM>) configured to enable the imaging unit (<NUM>) to perform pre-imaging one or more times, and main imaging one or more times following the pre-imaging;
wherein the control unit (<NUM>) has
an image generating portion (<NUM>) configured to generate a subject image for the pre-imaging based on one or more taken images in the pre-imaging and generates a subject image for the main imaging based on one or more taken images in the main imaging,
an interface portion (<NUM>) configured to display the subject image for the pre-imaging,
a region setting portion (<NUM>) configured to set a region-of-interest on a region of the subject image for the pre-imaging including light emission patterns of chemiluminescent samples or fluorescent samples and a non-region-of-interest of the subject image for the pre-imaging on a region of the subject image where light emission patterns of chemiluminescent samples or fluorescent samples are unlikely to be present,
the imaging system (<NUM>) characterized in that the control unit (<NUM>) further has:
a SN ratio calculating portion (<NUM>) configured to calculate a signal-to-noise ratio, SN ratio (SN(t)), of the region-of-interest that changes according to a light exposure time (t), which is a ratio of a signal component of a pixel value to a noise component of the pixel value, based on pixel values within the set region-of-interest and pixel values within the set non-region-of-interest, and
a total light exposure time calculating portion (<NUM>) configured to calculate a total light exposure time in which a maximum SN ratio (SN<NUM>) corresponding to a peak of the calculated SN ratio (SN(t)) or a preset reference SN ratio (SN<NUM>) can be obtained, wherein the preset reference SN ratio is set as the product of a SN ratio calculated in the subject image for pre-imaging based on pixel values within the set region-of-interest and pixel values within the set non-region-of-interest and a reference SN ratio improvement coefficient that is set in advance; and
wherein the control unit (<NUM>) is configured to enable the imaging unit (<NUM>) to perform the main imaging based on the total light exposure time.