Imaging device and imaging method

An imaging device includes an imaging unit which has an imaging element configured to nondestructively read an image signal and performs imaging of a subject using the imaging element, a reading control unit which performs nondestructive reading of the image signal from the imaging element during imaging of the subject, a temporary storage unit which stores the image signal nondestructively read by the reading control unit, an abnormality detection unit which detects the occurrence of an abnormal state during imaging of the subject, and a display control unit which reads and outputs the image signal stored in the storage unit in a case where the abnormal state is detected by the abnormality detection unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-074779, filed on Apr. 1, 2015. The above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging device and an imaging method which image light emitted from a subject with an imaging element.

2. Description of the Related Art

Hitherto, an imaging system which has a subject placed inside a housing, irradiates the subject with light using a light source provided in the housing to image the subject has been used in various fields.

In such an imaging system, an imaging method is primarily switched depending on the type of subject, and for example, an imaging system which images chemoluminescence, fluorescence, or reflected light from the subject or transmitted light transmitted through the subject with an imaging element to generate an image has been suggested.

SUMMARY OF THE INVENTION

In the imaging system described above, for example, in a case where a user erroneously open a door of the housing during imaging, since external light enters the housing, external light fogs an image being captured, and the image is invalidated. In a case where abnormality occurs in the imaging element which captures an image, the light source, or the like during imaging, appropriate imaging cannot be performed, and an image is invalidated.

JP2004-180317A and JP2002-27326A disclose an imaging device using an imaging element, and disclose that nondestructive reading from the imaging element is performed to acquire an image signal; however, there is not suggestion that the image signal is used in a case where abnormality occurs in the device described above.

The invention has been accomplished in consideration of the above-described problem, and an object of the invention is to provide an imaging device and an imaging method capable of allowing a user to confirm an image captured immediately before in a case where the user erroneously opens a door of a housing during imaging or in a case where abnormality occurs in an imaging element, a light source, or the like during imaging.

An imaging device of the invention comprises an imaging unit which has an imaging element configured to nondestructively read an image signal and performs imaging of a subject using the imaging element, a reading control unit which performs nondestructive reading of the image signal from the imaging element during imaging of the subject, a storage unit which stores the image signal nondestructively read by the reading control unit, an abnormality detection unit which detects the occurrence of an abnormal state during imaging of the subject, and an output unit which reads and outputs the image signal stored in the storage unit in a case where the abnormal state is detected by the abnormality detection unit.

In the imaging device of the invention, the reading control unit may consecutively perform nondestructive reading of the image signal multiple times.

In the imaging device of the invention, the reading control unit may perform nondestructive reading of the image signal at a given constant time interval set in advance.

The imaging device of the invention may further comprise a housing in which the subject is placed and which has an opening/closing door, and an open state detection unit which detects an open state of the opening/closing door, and the abnormality detection unit may detect the occurrence of the abnormal state in a case where the open state of the opening/closing door is detected by the open state detection unit.

The imaging device of the invention may further comprise an imaging element abnormality detection unit which detects abnormality of the imaging element, and the abnormality detection unit may detect the occurrence of the abnormal state in a case where abnormality of the imaging element is detected by the imaging element abnormality detection unit.

In the imaging device of the invention, the imaging element abnormality detection unit may detect the temperature of the imaging element and may detect abnormality of the imaging element in a case where the detected temperature is outside a range set in advance.

The imaging device of the invention may further comprise a light source unit which irradiates the subject with light, and a light source abnormality detection unit which detects abnormality of the light source unit, and the abnormality detection unit may detect the occurrence of the abnormal state in a case where abnormality of the light source unit is detected by the light source abnormality detection unit.

In the imaging device of the invention, the light source abnormality detection unit may detect abnormality of the light source unit in a case where disconnection or short-circuiting of the light source unit is detected.

In the imaging device of the invention, the abnormality detection unit may detect abnormal states in steps, and the imaging device may further comprise a notification unit which gives notification of the abnormal state in a case where an abnormal state of a first step is detected, and a control unit which stops the imaging in a case where an abnormal state of a second step having a higher degree of abnormality than the first step is detected. The abnormal state of the first step refers to an abnormal state which does not have a significant effect on an image, and is, for example, a state in which the temperature of the imaging element exceeds a threshold by 0.5° C. The abnormal state of the second step is a state in which abnormality appears in an image visibly, and refers to a case where the temperature of the imaging element exceeds the threshold by 10° C., a case where the light source is disconnected (turned off), or a case where the door is opened during imaging.

The imaging device of the invention may further comprise a continuous storage unit which has a nonvolatile memory, and a selection reception unit which receives selection of whether or not to store the nondestructively read image signal read from the storage unit in the continuous storage unit, and the nondestructively read image signal may be stored in the continuous storage unit in a case where the selection reception unit selects to store the nondestructively read image signal, and the nondestructively read image signal may not be stored in the continuous storage unit in a case where the selection reception unit selects not to store the nondestructively read image signal.

As the imaging element, a complementary metal-oxide semiconductor (CMOS) image sensor may be used.

An imaging method of the invention which performs imaging of a subject using an imaging element configured to nondestructively read an image signal comprises performing nondestructive reading of the image signal from the imaging element during imaging of the subject, storing the nondestructively read image signal, and reading and outputting the stored image signal in a case where the occurrence of an abnormal state during imaging of the subject is detected.

According to the imaging device and the imaging method of the invention, when performing imaging of the subject using the imaging element capable of nondestructively reading the image signal, nondestructive reading of the image signal from the imaging element is performed during imaging of the subject, and the nondestructive read image signal is stored. In a case where the abnormal state occurs during imaging of the subject, the stored image signal is read and output; therefore, as described above, even in a case where the user erroneously opens the door of the housing during imaging or a case where abnormality occurs in the imaging element which captures an image, the light source, or the like during imaging, it is possible to allow the user to confirm an image captured immediately before.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an imaging system1using a first embodiment of an imaging device and method of the invention will be described in detail referring to the drawings. The imaging system1of this embodiment has a feature in processing in a case where an abnormal state occurs during imaging, and first, the overall configuration of the imaging system1will be described.

FIG. 1is a schematic perspective view showing the imaging system1of this embodiment,FIG. 2is a schematic sectional view showing the internal configuration of an imaging device of this embodiment, andFIG. 3is a schematic block diagram showing the imaging system1of this embodiment.

As shown inFIGS. 1 and 2, the imaging system1of this embodiment includes an imaging device body10and an imaging control device100.

The imaging device body10includes a housing12which has an opening/closing door14, a stage16on which a subject S is placed, an imaging unit20, a lens unit22, an epi-illumination light source unit24, a transmission light source unit26, and a subject observation monitor50. In this embodiment, the epi-illumination light source unit24or the transmission light source unit26corresponds to a light source unit of the invention.

The housing12has a hollow portion18formed in a substantially rectangular parallelepiped, and is provided with the stage16on which the subject S is placed. The opening/closing door14shown inFIG. 1is openably attached to the housing12, and the user opens the opening/closing door14, places the subject S on the stage16, and then closes the opening/closing door14, thereby housing the subject S in the housing12. The housing12is constituted of a black box in which external light does not enter the hollow portion18. The stage16is formed of a material which transmits light from the transmission light source unit26.

In a surface of the opening/closing door14on the hollow portion18side, when the opening/closing door14is closed, a fitting portion13awhich is fitted into a hole13bformed on the housing body side. An open/closed state detection unit13(seeFIG. 3) which detects whether or not the fitting portion13ais fitted is provided in the hole13b. As described above, the open/closed state detection unit13detects the open/closed state of the opening/closing door14by detecting whether or not the fitting portion13ais fitted into the hole13b. As the open/closed state detection unit13, a micro switch, an optical sensor, or the like is available. The open/closed state detection unit13of this embodiment corresponds to an open state detection unit of the invention.

The imaging unit20is fixed to the upper surface of the housing12, includes, for example, an imaging element21, such as a complementary metal-oxide semiconductor (CMOS) image sensor, and detects light reflected from the subject S, light emitted from the subject S, or light transmitted through the subject S to generate an image signal. The image signal generated in the imaging unit20is subjected to, for example, amplification processing and then output to the imaging control device100.

The lens unit22is attached to the imaging unit20. The lens unit22includes, for example, a plurality of lenses, and the lenses are provided so as to be movable in a direction of an arrow Z to focus on the subject S. The lens unit22includes, for example, optical elements, such as a diaphragm and an excitation light cut filter, and adjusts the amount or the wavelength of light to be detected.

The epi-illumination light source unit24and the transmission light source unit26respectively have, for example, an excitation light source for fluorescent imaging and a white light source, and the light sources are switched under the control of the imaging control device100as necessary. For example, in a case of performing imaging for detecting fluorescence emitted from the subject S fluorescence-labeled, the subject S is irradiated with excitation light from the epi-illumination light source unit24or the transmission light source unit26, in a case of performing imaging for detecting reflected light from the subject S, the subject S is irradiated with white light from the epi-illumination light source unit24, and in a case of performing imaging for detecting transmitted light transmitted through the subject S, the subject S is irradiated with white light from the transmission light source unit26.

The subject observation monitor50displays a status on the stage16imaged by a small camera (not shown) provided in the upper portion of the housing12. With this, it is possible to confirm the position of the subject S placed on the stage16or the height of the stage16, and to adjust the position of the subject S or the height of the stage16such that the subject S is placed suitably for imaging.

The imaging control device100is constituted of, for example, a computer, and includes a control device body102, an input unit104, and a display unit106. The imaging control device100controls the operations of the imaging unit20, the epi-illumination light source unit24, and the transmission light source unit26of the imaging device body10, and the imaging device body10images the subject S under the control of the imaging control device100. In this embodiment, the imaging unit20and the open/closed state detection unit13in the imaging device body10, a reading control unit111and a display control unit112in the imaging control device100, and an abnormality detection unit113constitute an imaging device of the invention. In this embodiment, the display control unit112corresponds to an output unit and a notification unit of the invention.

As shown inFIG. 3, the control device body102includes an image processing unit108, a control unit110, an abnormality detection unit113, a temporary storage unit114, and a continuous storage unit115. In this embodiment, the temporary storage unit114corresponds to a storage unit of the invention.

The control unit110includes, for example, a central processing unit (CPU), a read only memory (ROM), and the like. The control unit110integrally controls the operations of the respective units in the imaging device body10and the imaging control device100.

The control unit110includes the reading control unit111and the display control unit112. The reading control unit111reads and controls the image signal from the imaging element21in the imaging unit20.

The reading control unit111of the embodiment reads an image signal of an observation image from the imaging element21when an exposure time set in advance has elapsed, and performs nondestructive reading of the image signal at a given constant time interval for the exposure time (during imaging of the observation image). Nondestructive reading refers to a method which, when reading the image signal from the imaging element21, reads the image signal while maintaining the storage state without emptying electric charge stored in each photoelectric conversion element constituting the imaging element21. That is, since reset processing is not performed when reading the image signal, it is possible to read the image signal any number of times in the middle of storing electric charge. The reading control unit can consecutively perform nondestructive reading of the image signal multiple times, and for example, performs nondestructive reading about two times to 12 times. The reading control unit can perform nondestructive reading of the image signal at a given constant time interval set in advance, and for example, performs reading at an interval of, for example, 0.1 seconds to 60 minutes.

However, the invention is not limited to the above.

The continuous storage unit115stores the image signal of the observation image. As the continuous storage unit115, for example, a nonvolatile memory, such as a flash memory, is available. The continuous storage unit115can store the image signal acquired by nondestructive reading in response to a request from the user.

The temporary storage unit114stores the image signal acquired by nondestructive reading. As the temporary storage unit114, for example, a volatile memory, such as a synchronous dynamic random access memory (SDRAM), is available. In the embodiment, the temporary storage unit114corresponds to a storage unit of the invention.

The image processing unit108receives the image signals read from the continuous storage unit115and the temporary storage unit114as input and subjects the read image signals to necessary signal processing. The signal processing includes, for example, dark current correction processing, sharpness processing, and the like. The dark current correction processing is processing for subtracting a dark image signal stored in advance from an image signal acquired by imaging.

The display control unit112displays the observation image on the display unit106based on the image signal subjected to the signal processing in the image processing unit108. The display control unit112reads the nondestructively read image signal stored in the temporary storage unit114in a case where the abnormality detection unit113detects the occurrence of an abnormal state during imaging, and displays a confirmation image on the display unit106based on the image signal subjected to the signal processing in the image processing unit108.

In a case where the abnormality detection unit113detects the occurrence of the abnormal state during imaging, the display control unit112displays a warning, such as a message informing the user of the effect on the display unit106. Instead of a message, an index, such as a mark, may be displayed. In this embodiment, although a message or the like is displayed to give the user a warning, the invention is not limited thereto, a lamp may be turned on or sound may be made to give notification to the user.

The abnormality detection unit113detects the occurrence of the abnormal state during imaging of the subject S. Specifically, in a case where the open/closed state detection unit13detects that the opening/closing door14is opened during imaging of the observation image, the abnormality detection unit113of this embodiment receives the detection signal and detects the occurrence of the abnormal state during imaging. In a case where the abnormality detection unit113detects the occurrence of the abnormal state during imaging, as described above, the display control unit112reads the nondestructively read image signal most recently stored in the temporary storage unit114, the image signal is subjected to the signal processing in the image processing unit108, and then, a confirmation image is displayed on the display unit106based on the image signal subjected to the signal processing.

The display unit106comprises, for example, a display device, such as a cathode ray tube (CRT) display or a liquid crystal display, and as described above, displays the observation image and the confirmation image, or displays the warning message. The display unit106displays a setting screen for performing various settings in or giving instructions to the respective units of the imaging device body10.

The input unit104comprises a mouse, a keyboard, and the like. The input unit104receives various setting inputs of the respective units in the imaging device body10. The input unit104receives selection of whether or not to store the nondestructively read image signal read from the temporary storage unit114in the continuous storage unit115. The input unit104of this embodiment corresponds to a selection reception unit of the invention.

The imaging system1of this embodiment has the above configuration, thereby performing imaging by four imaging methods according to the type of subject S or the purpose of imaging. The four imaging methods include an imaging method (hereinafter, referred to as a first imaging method) which detects chemoluminescence emitted from the subject S, an imaging method (hereinafter, referred to as a second imaging method) which detects fluorescence emitted from the subject S, an imaging method (hereinafter, referred to as a third imaging method) which detects reflected light reflected from the subject S, and an imaging method (hereinafter, referred to as a fourth imaging method) which detects transmitted light transmitted through the subject S.

In the first imaging method, a phenomenon (chemoluminescence or chemiluminescence) in which, when a subject molecule excited by a chemical reaction is returned to a ground state, energy is discharged as light is used. With this, for example, it is possible to perform genetic analysis, inspection and research of biological tissues relating to diseases and aging, deterioration evaluation of organic compounds and polymer compounds, and the like. For example, an imaging target substance in a subject is labeled by a labeling substance which generates chemoluminescence when coming into contact with a chemoluminescence substrate, and thereafter, the chemoluminescence substrate is brought into contact with the labeling substance, whereby chemoluminescence can be generated. In the first imaging method, light irradiation from the epi-illumination light source unit24and the transmission light source unit26is not performed.

In the second imaging method, excitation light is irradiated from the epi-illumination light source unit24or the transmission light source unit26, and fluorescence from a fluorescence substance labeling an imaging target substance in a subject is detected. As the subject S of the second imaging method, for example, a gel support containing a deoxyribonucleic acid (DNA) fragment fluorescence-labeled and separated by electrophoresis is considered. If this imaging system1is used, the distribution of the DNA fragment in the gel support can be imaged and evaluated.

In the third imaging method, for example, white light is irradiated as illumination light from the epi-illumination light source unit24, and reflected light of illumination light from the subject S is detected. With this, it is possible to obtain a digital image by photoelectrically reading a reflective original, such as a photograph. In the fourth imaging method, white light is irradiated as illumination light from the transmission light source unit26, and transmitted light of illumination light transmitted through the subject S is detected. With this, it is possible to obtain a digital image by photoelectrically reading a transmissive original, such as a film.

Next, the action of the imaging system1of this embodiment will be described referring to the flowchart shown inFIG. 4.

First, after the subject S is placed on the stage16of the imaging device body10, an imaging start instruction is input by the user using the input unit104, and imaging by the imaging unit20is started. Specifically, exposure of the imaging element21of the imaging unit20is started (S10).

After imaging is started, an image signal is read from the imaging element21at a given constant time interval (for example, an interval of one second) by nondestructive reading (S12), and the image signal is sequentially stored in the temporary storage unit114(S14).

In a case where the opening/closing door14is erroneously opened by the user during imaging of the subject S (S16, YES), the open/closed state detection unit13detects this state, the abnormality detection unit113receives the detection signal, and the abnormality detection unit113detects the occurrence of an abnormal state during imaging (S18).

In a case where the abnormality detection unit113detects the occurrence of the abnormal state during imaging, the display control unit112displays a warning message on the display unit106(S20), and the control unit110stops imaging (S22).

Next, the display control unit112reads the nondestructively read image signal most recently stored in the temporary storage unit114(S24).

The nondestructively read image signal read from the temporary storage unit114is input to the image processing unit108and is subjected to signal processing in the image processing unit108, and then, the display control unit112displays a confirmation image on the display unit106based on the image signal subjected to the signal processing (S26).

A selection screen of whether or not to store the nondestructively read image signal in the continuous storage unit115is displayed on the display unit106, and in a case where the user selects to store the image signal in the continuous storage unit115using the input unit104(S28, YES), the nondestructively read image signal is stored in the continuous storage unit115(S30). In a case where the user selects not to store the image signal in the continuous storage unit115(S28, NO), the nondestructively read image signal is not stored in the continuous storage unit115, and the processing ends. In this way, the user selects whether or not to store the nondestructively read image signal in the continuous storage unit115, whereby only a necessary image signal can be stored in the continuous storage unit115.

In a case where the door is not opened during imaging and an imaging exposure time set in advance has elapsed (S32, YES), the reading control unit111reads the image signal from the imaging element21by destructive reading, and the image signal is stored in the continuous storage unit115(S34). Destructive reading refers to a reading method which, when reading the image signal from the photoelectric conversion element of the imaging element21, performs reset processing for emptying electric charge stored in the photoelectric conversion element.

The display control unit112reads the destructively read image signal stored in the continuous storage unit115, the image signal is subjected to signal processing in the image processing unit108, and then, the display control unit112displays an observation image on the display unit106based on the image signal subjected to the signal processing (S36).

According to the imaging system1of the first embodiment described above, nondestructive reading of the image signal from the imaging element21is performed during imaging of the subject S, and the nondestructively read image signal is stored. In a case where the occurrence of an abnormal state during imaging of the subject S is detected, the stored image signal is read and output; thus, even in a case where the user erroneously opens the door of the housing12during imaging, it is possible to allow the user to confirm the image captured immediately before.

Next, an imaging system2using a second embodiment of an imaging device and method of the invention will be described. In the imaging system1of the first embodiment, although the abnormality detection unit113detects the occurrence of the abnormal state during imaging in a case where the opening/closing door14is erroneously opened during imaging, the imaging system2of the second embodiment detects the occurrence of the abnormal state during imaging in a case where abnormality of the imaging element21is detected. Specifically, the imaging system2of the second embodiment detects temperature abnormality of the imaging element21. This is because, if the temperature of the imaging element21changes, a dark current level changes and has magnitude different from the dark image signal for use when performing the dark current correction processing described above, and appropriate dark current correction processing cannot be performed. In the imaging system2of the second embodiment, other configurations are the same as those in the imaging system1of the first embodiment.

FIG. 5is a block diagram showing the schematic configuration of the imaging system2of the second embodiment. As shown inFIG. 5, an imaging device body10of the imaging system2of the second embodiment is provided with an imaging element abnormality detection unit27which detects abnormality of the imaging element21. Specifically, the imaging element abnormality detection unit27of this embodiment comprises a temperature sensor which detects the temperature of the imaging element21, and detects abnormality of the imaging element21in a case where the temperature detected by the temperature sensor is outside a range set in advance. The imaging element abnormality detection unit27may directly detect the temperature of the imaging element21, or may detect the temperature of outside air near the imaging element21to indirectly the temperature of the imaging element21.

Next, the action of the imaging system2of this embodiment will be described referring to the flowchart shown inFIG. 6.

First, after the subject S is placed on the stage16of the imaging device body10, an imaging start instruction is input by the user using the input unit104, and imaging by the imaging unit20is started (S40).

After imaging is started, an image signal is read from the imaging element21at a given constant time interval by nondestructive reading (S42), and the image signal is sequentially stored in the temporary storage unit114(S44).

In a case where the temperature of the imaging element21is outside a first threshold range during imaging of the subject S (S46, YES), the imaging element abnormality detection unit27detects this state, the abnormality detection unit113receives the detection signal, and the abnormality detection unit113detects the occurrence of the abnormal state during imaging (S48). The first threshold range is set to, for example, −25° C.±0.5° C.

As described above, in a case where the temperature of the imaging element21is outside the first threshold range, first, the display control unit112displays a warning message on the display unit106(S50).

Subsequently, imaging is continued, and in a case where the temperature of the imaging element21continues to change and is outside a second threshold range (S52, YES), the display control unit112further displays a warning message on the display unit106(S54), and the control unit110stops imaging (S56). The second threshold range is set to, for example, −25° C.±1° C.

Next, the display control unit112reads the nondestructively read image signal most recently stored in the temporary storage unit114(S58).

The nondestructively read image signal read from the temporary storage unit114is input to the image processing unit108and is subjected to signal processing in the image processing unit108, and then, the display control unit112displays a confirmation image on the display unit106based on the image signal subjected to the signal processing (S60).

A selection screen of whether or not to store the nondestructively read image signal in the continuous storage unit115is displayed on the display unit106, and in a case where the user selects to store the image signal in the continuous storage unit115(S62, YES), the nondestructively read image signal is stored in the continuous storage unit115(S64). In a case where the user selects not to store the image signal in the continuous storage unit115(S62, NO), the nondestructively read image signal is not stored in the continuous storage unit115, and the processing ends.

In a case where the temperature of the imaging element21is not outside the first threshold range during imaging (S46, NO) and in a case where the temperature of the imaging element21is outside the first threshold range during imaging and is not outside the second threshold range (S52, NO), when an imaging exposure time set in advance has elapsed (S66, YES), the reading control unit111reads the image signal from the imaging element21by destructive reading, and the image signal is stored in the continuous storage unit115(S68).

The display control unit112reads the destructively read image signal stored in the continuous storage unit115, the image signal is subjected to signal processing in the image processing unit108, and then, the display control unit112displays an observation image on the display unit106based on the image signal subjected to the signal processing (S70).

According to the imaging system2of the second embodiment described above, even in a case where abnormality occurs in the imaging element21during imaging, it is possible to subject an image captured immediately before to appropriate dark current correction processing, and to allow the user to confirm the image.

Next, an imaging system3using a third embodiment of an imaging device and method of the invention will be described. In the imaging system2of the second embodiment, although the abnormality detection unit113detects the occurrence of the abnormal state during imaging in a case where abnormality of the imaging element21is detected, the imaging system3of the third embodiment detects the occurrence of the abnormal state during imaging in a case where abnormality of the light source is detected. In the imaging system3of the third embodiment, other configurations are the same as those in the imaging system1of the first embodiment.

FIG. 7is a block diagram showing the schematic configuration of the imaging system3of the third embodiment. As shown inFIG. 7, an imaging device body10of the imaging system3of the third embodiment is provided with a light source abnormality detection unit28which detects abnormality of the epi-illumination light source unit24and the transmission light source unit26. Specifically, the light source abnormality detection unit28of this embodiment detects disconnection or short-circuiting in the epi-illumination light source unit24and the transmission light source unit26. In regards to disconnection and short-circuiting in the epi-illumination light source unit24and the transmission light source unit26, for example, a disconnection and short-circuiting detection function of an IC which drives and controls the light sources may be used, or a voltage or the like applied to the epi-illumination light source unit24and the transmission light source unit26may be monitored.

Next, the action of the imaging system3of this embodiment will be described referring to the flowchart shown inFIG. 8.

First, after the subject S is placed on the stage16of the imaging device body10, an imaging start instruction is input by the user using the input unit104, and imaging by the imaging unit20is started (S80).

After imaging is started, an image signal is read from the imaging element21at a given constant time interval by nondestructive reading (S82), and the image signal is sequentially stored in the temporary storage unit114(S84).

In a case where disconnection or short-circuiting of the epi-illumination light source unit24or the transmission light source unit26occurs during imaging of the subject S (S86, YES), the light source abnormality detection unit28detects this state, the abnormality detection unit113receives the detection signal, and the abnormality detection unit113detects the occurrence of the abnormal state during imaging (S88).

In a case where the abnormality detection unit113detects the occurrence of the abnormal state during imaging, the display control unit112displays a warning message on the display unit106(S90), and the control unit110stops imaging (S92).

Next, the display control unit112reads the nondestructively read image signal most recently stored in the temporary storage unit114(S94).

The nondestructively read image signal read from the temporary storage unit114is input to the image processing unit108and is subjected to signal processing in the image processing unit108, and then, the display control unit112displays a confirmation image on the display unit106based on the image signal subjected to the signal processing (S96).

A selection screen of whether or not to store the nondestructively read image signal in the continuous storage unit115is displayed on the display unit106, and in a case where the user selects to store the image signal in the continuous storage unit115(S98, YES), the nondestructively read image signal is stored in the continuous storage unit115(S100). In a case where the user selects not to store the image signal in the continuous storage unit115(S98, NO), the nondestructively read image signal is not stored in the continuous storage unit115, and the processing ends.

In a case where disconnection or short-circuiting of the epi-illumination light source unit24or the transmission light source unit26does not occur and an imaging exposure time set in advance has elapsed (S102, YES), the reading control unit111reads the image signal from the imaging element21by destructive reading, and the image signal is stored in the continuous storage unit115(S104). Destructive reading refers to a reading method which, when reading the image signal from the photoelectric conversion element of the imaging element21, performs reset processing for emptying electric charge stored in the photoelectric conversion element.

The display control unit112reads the destructively read image signal stored in the continuous storage unit115, the image signal is subjected to signal processing in the image processing unit108, and then, the display control unit112displays an observation image on the display unit106based on the image signal subjected to the signal processing (S106).

According to the imaging system3of the third embodiment described above, even in a case where abnormality occurs in the light source during imaging, it is possible to allow the user to confirm an image captured immediately before.

Although the imaging system1of the first embodiment described above detects that the opening/closing door14is opened during imaging, the imaging system2of the second embodiment detects the occurrence of abnormality in the imaging element21, and the imaging system3of the third embodiment detects the occurrence of abnormality in the light source, all of these abnormalities may be detected. In this case, the abnormality detection unit113may detect abnormal states in steps and may be operated according to the degree of abnormality.

Specifically, in a case where an abnormal state is detected during imaging and this abnormality is abnormality of the temperature of the imaging element21, and as in the second embodiment described above, in a case where the temperature of the imaging element21is outside the first threshold range (for example, −25° C.±0.5° C.) and is within the second threshold range (for example, −25° C.±1° C.), since the degree of abnormality is not so high, display of a warning message by the display control unit112is performed without stopping imaging. In a case where the temperature of the imaging element21is outside the second threshold range (for example, −25° C.±1° C.), since the degree of abnormality is high, the display control unit112displays a warning message and the control unit110stops imaging.

In a case the abnormal state is detected during imaging and this abnormality is disconnection or short-circuiting of the epi-illumination light source unit24or the transmission light source unit26and a case where this abnormality is the detection of the open state of the opening/closing door14, as in the first and third embodiments, the display control unit112displays a warning message and the control unit110stops imaging. In this way, the abnormal states are detected in steps, whereby it is possible to prevent imaging from being wastefully stopped.