Imaging device

An imaging device includes an imager 7 which images an X-ray image generated by X-ray irradiation; an X-ray detector 90 which detects X-ray irradiation and outputs a detected signal showing the result of the detection; an EP-ROM 93a storing an offset value of the X-ray detector 90; and a signal processor 61 which generates reference information for acquiring a start timing of imaging by the imager 7 from the detected signal based on the offset value stored in the EP-ROM 93a.

TECHNICAL FIELD

The present invention relates to an imaging device which images an X-ray image.

BACKGROUND ART

Patent Document 1 listed below discloses an X-ray imaging device (X-ray image forming apparatus) which images an X-ray image of teeth, etc., of an examinee by using an image sensor including a CCD (Charge Coupled Devices). This image sensor includes, in addition to the CCD for imaging an X-ray image, a monitoring photodiode (X-ray detector) for detecting an X-ray irradiation timing. Based on an output signal from the X-ray detector, a trigger signal showing the start or the end of X-ray imaging is generated. In detail, when the value of the output signal exceeds a predetermined threshold, a trigger signal showing the start of X-ray imaging is generated.Patent Document 1: Japanese Published Examined Patent Application No. 3335350

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

However, an offset value of the output signal from the X-ray detector is different among X-ray detectors, and even in the case where the X-ray intensity is the same, if the X-ray detector is different, the value of the output signal is also different. Therefore, there is a possibility that even when an X-ray is irradiated, the value of the output signal does not exceed a preset threshold and a trigger signal showing the start of X-ray imaging is not generated. Therefore, an object of the present invention is to provide an imaging device which can accurately generate a trigger showing the start of X-ray imaging according to the offset value of the X-ray detector.

Means for Solving the Problem

An imaging device of the present invention includes an imager which images an X-ray image generated by X-ray irradiation; an X-ray detector which detects the X-ray irradiation and outputs a detected signal showing a result of the detection; a storage which stores offset information of the X-ray detector; and a reference information generator which generates acquisition reference information for acquiring a start timing of imaging by the imager from the detected signal based on the offset information stored in the storage. Therefore, offset information of the X-ray detector is stored in advance in the storage, so that the operation for adjusting the acquisition reference information according to variation in the offset value of each X-ray detector becomes unnecessary.

Further, an imaging device of the present invention includes an imager which images an X-ray image generated by X-ray irradiation; an X-ray detector which detects the X-ray irradiation and outputs a detected signal showing a result of the detection; and a reference information generator which acquires offset information of the X-ray detector based on the detected signal and generates acquisition reference information for acquiring a start timing of imaging by the imager from the detected signal based on the offset information. Thus, acquisition reference information is generated based on a detected signal from the X-ray detector, and based on this acquisition reference information, an imaging start timing can be acquired from the detected signal, so that regardless of variation in the offset value of the X-ray detector included in the detected signal, the imaging start timing can be accurately acquired each time of X-ray irradiation. Further, the operation for adjusting the acquisition reference information according to variation in the offset value of each X-ray detector becomes unnecessary.

Further, preferably, the reference information generator generates the acquisition reference information based on the offset information and an intensity of the X-ray irradiation. Thus, acquisition reference information is generated based on the offset information and the X-ray irradiation intensity, so that the imaging start timing can be accurately acquired regardless of fluctuation in the X-ray irradiation intensity.

Effect of the Invention

The present invention can provide an imaging device which can accurately generate a trigger showing an X-ray imaging start according to an offset value of the X-ray detector.

DESCRIPTION OF THE REFERENCE NUMERALS

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are attached with the same reference numerals, and overlapping description may be omitted.

First Embodiment

First, a configuration of an X-ray imaging system10will be described with reference toFIG. 1(a). The X-ray imaging system10is a medical X-ray imaging system for X-ray imaging teeth, etc., of an examinee. This X-ray imaging system10includes an X-ray irradiation device1, an X-ray imaging device2, a PC (Personal Computer)3, and a display4. The X-ray irradiation device1irradiates teeth, etc., with an X-ray, and is configured as a fixed installation type. The X-ray irradiation device1performs steady X-ray irradiation (X-ray XR) corresponding to a voltage waveform of a complete DC voltage obtained by using a high-frequency inverter until an input of an X-ray irradiation ending instruction (or until an irradiation ending timer terminates). The X-ray irradiation device1can also perform periodic X-ray irradiation (X-ray XR) corresponding to a half-wave rectified waveform of an AC power supply voltage.

The X-ray imaging device2is for imaging an X-ray image of teeth, etc., and includes an optical image acquiring part5and a controller6. The optical image acquiring part5includes an imager7and a connecting part8, and the imager7is connected to the connecting part8via a signal cable L1. The imager7includes a CCD72described later, and images an X-ray image of teeth, etc., by using this CCD72. The imager7has dimensions and a shape capable of being easily inserted into the oral cavity of an examinee. Here,FIG. 1(b) shows an example of a state where the imager7is inserted into the oral cavity of an examinee. The imager7is inserted to the inside of the front teeth on the upper jaw of the examinee, and from this imager7, the signal cable L1extends to the outside of the oral cavity. The controller6is connected to the PC3via the signal cable L2. The controller6controls the optical image acquiring part5(specifically, imager7) and transmits image data to the PC3in response to various control instructions transmitted from the PC3to the optical image acquiring part5. The signal cable L2is a USB (Universal Serial Bus) cable or the like. In addition to transmission and receiving of signals, the USB cable can supply power to the X-ray imaging device2.

The PC3performs various settings (for example, setting of resolution, etc.) and X-ray imaging instruction for the X-ray imaging device2, various analyses (for example, extraction, enlargement, etc., of a specific region of an image) by loading image data showing an X-ray image from the X-ray imaging device2, and further, stores data showing the image data and the analysis results in a memory, via the signal cable L2. Further, the PC3displays the X-ray image based on the image data loaded from the X-ray imaging device2and displays the analysis results, etc., of the image data on the display4. Here, the display4includes a display part such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display).

Next, a configuration of the X-ray imaging device2will be described with reference toFIG. 2. The imager7includes a scintillator71, a CCD72, and a CCD controller73. The signal cable L1includes a detected signal line L11, a control signal line L12, and an image information line L13. A scintillator71emits visible light VL with a light amount corresponding to an energy amount of an X-ray XR when this X-ray XR is made incident thereon. When the CCD72is irradiated with the visible light VL from the scintillator71, the CCD photoelectrically converts this visible light VL to generate a charge corresponding to the light amount of the visible light VL (charge showing an image, hereinafter, referred to as image information), and accumulates this charge in a readable manner (hereinafter, also referred to as imaging). The CCD controller73is connected to the CCD72, the control signal line L12, and the image information line L13. When the CCD controller73receives a control signal for the CCD72from the controller6via the control signal line L12, it controls the driving of the CCD72according to this control signal. Here, the control signal for the CCD72means an X-ray image imaging instruction and a reading instruction, etc., for reading image information showing an X-ray image. In the description hereinafter, “signal” means an analog signal. The CCD controller73reads image information from the CCD72based on the control performed by the controller6, and outputs the read image information to the controller6via the image information line L13.

The connecting part8is connected to the signal cable L1, and has a function for removably connecting the optical image acquiring part5to the controller6. A control signal for the imager7is transmitted to the imager7from the controller6via the connecting part8and the control signal line L12. Image information read from the CCD72is transmitted to the controller6via the image information line L13and the connecting part8. The connecting part8includes a connector81. The connector81is, for example, a 36-pin MDR connector, etc.

The optical image acquiring part5further includes a trigger generating unit9. The trigger generating unit9generates a trigger signal showing an X-ray image imaging starting instruction or imaging ending instruction, and outputs this trigger signal to the controller6. The trigger generating unit9includes an X-ray detector90having a PD91(PD: Photo Diode) and an amplifier92, a detected signal line L11, and a trigger generator93which is connected to the X-ray detector90via the detected signal line L11. The trigger generator93includes an EP-ROM93a(storage) and a comparator93b. The X-ray detector90is provided in the imager7. The PD91is a monitoring photodiode for monitoring an X-ray XR irradiated by the imager7, and is provided in the CCD72. The amplifier92is provided in the CCD controller73. The PD91is connected to the amplifier92, and the amplifier92is connected to the detected signal line L11. The detected signal line L11is included in the signal cable L1. The trigger generator93is provided in the connecting part8.

The controller6includes a signal processor61(reference information generating part), a trigger processor62, an I/O controller63, an A/D converter64, a CCD driver65, and a D/A converter66. The controller6has a connection terminal (not shown) to which the connector81of the optical image acquiring part5is removably attached, and transmits and receives various signals to and from the optical image acquiring part5via this connecting terminal. The controller6is connected to a signal cable L2, and transmits and receives various data to and from the PC3via the signal cable L2. In the following description, “data” means digital data. The signal processor61is connected to the trigger processor62, the I/O controller63, the A/D converter64, and the CCD driver65. Then, the signal processor61is connected to the EP-ROM93avia the connector81. The signal processor61controls the components such as the optical image acquiring part5and the trigger processor62, etc., according to trigger data described later (data showing an X-ray image imaging start timing or imaging end timing) described later input from the trigger processor62, and command data from the PC3input via the I/O controller63. Alternatively, the signal processor61acquires image data from the CCD controller73via the A/D converter64, and transmits this acquired image data to the PC3via the I/O controller63. The signal processor61acquires data showing an offset value (offset information) of an output signal (signal S2described later) output from the X-ray detector90from the EP-ROM93a, and based on the acquired data, generates reference data (acquisition reference information) to be used for trigger signal generation from the trigger generator93. The signal processor61outputs the reference data to the D/A converter66via the I/O controller63. Thereafter, the reference data is converted into an analog signal (reference signal S3) by the D/A converter66, and this reference signal S3is output to the comparator93b. The signal processor61may generate the reference signal S3based on the offset value of the output signal (signal S2) from the X-ray detector90and the irradiation intensity of the X-ray XR detected by the X-ray detector90. The functions of the signal processor61may be realized by hardware or software.

The trigger processor62is connected to the signal processor61. The trigger processor62is connected to the comparator93bvia the connector81. The trigger processor62generates trigger data showing an X-ray image imaging start timing and trigger data showing an imaging end timing according to a pulse (the pulse P2shown inFIG. 4(a) or the pulse P4shown inFIG. 4(b)) of the trigger signal S4input from the comparator93bvia the connector81, and outputs these trigger data to the signal processor61. The I/O controller63is connected to the signal processor61and the signal cable L2. The I/O controller63has an interface for transmitting and receiving data to and from the PC3via the signal cable L2based on a data transmission method of USB or the IEEE1394, etc. Without limiting to wired data transmission, the I/O controller63may include an interface compliant with the wireless data transmission method of a wireless LAN (Local Area Network) or Bluetooth, etc.

The A/D converter64is connected to the signal processor61. The A/D converter64is connected to the CCD controller73via the connector81and the image signal line L13. The A/D converter64converts image information acquired from the CCD controller73via the image signal line L13and the connector81into image data, and outputs this image data to the signal processor61. The CCD driver65generates a control signal (signal pulse) according to various control data for the imager7input from the signal processor61, and outputs this control signal to the imager7. The D/A converter66is connected to the I/O controller63. The D/A converter66is connected to the comparator93bvia the connector81. The D/A converter66converts reference data input from the signal processor61via the I/O controller63into a reference signal S3of an analog signal, and outputs this reference signal S3to the comparator93bvia the connector81.

Next, with reference toFIG. 3andFIG. 4, a configuration of the trigger generating unit9will be described. The PD91detects an X-ray XR irradiated by the X-ray irradiation device1. The PD91outputs an electric signal (hereinafter, referred to as S1) corresponding to the energy amount of the detected X-ray XR. Here, when steady X-ray irradiation corresponding to a voltage waveform of a complete DC voltage is performed by the X-ray irradiation device1, as shown inFIG. 4(a), the signal S1includes a pulse P1with a pulse width corresponding to the entire X-ray irradiation period T1(approximately, several tens of msec to several seconds). This pulse P1is a pulse generated by steady X-ray irradiation corresponding to a voltage waveform of a complete DC voltage. When periodic X-ray irradiation corresponding to a half-wave rectified waveform of an AC power supply voltage is performed by the X-ray irradiation device1, as shown inFIG. 4(b), the signal S1includes a plurality of periodic pulses P3in the entire X-ray irradiation period T1. The pulses P3are generated by periodic X-ray irradiation corresponding to the half-wave rectified waveform of an AC power supply voltage. The amplifier92includes an I-V conversion amplifier92aand a gain amplifier92b. The I-V conversion amplifier92ais connected to the PD91, and converts the signal S1input from the PD91into a voltage value. The gain amplifier92bis connected to the I-V conversion amplifier92a, and outputs a signal S2(detected signal) which is obtained by amplifying the signal S1converted into a voltage value by the I-V conversion amplifier92ato a signal level which can be processed by the connecting part8on the subsequent stage. The gain amplifier92bis connected to the detected signal line L11, and outputs the signal S2to the trigger generator93via the detected signal line L11.

The EP-ROM93ais connected to the connector81. The EP-ROM93ais connected to the signal processor61via the connector81, and outputs data showing the offset value of the output signal (signal S2) from the X-ray detector90to the signal processor61via the connector81based on control by the signal processor61. The EP-ROM93astores data such as the model number, the serial number, the manufacturing date, shipment history, etc., of the optical image acquiring part5(or the trigger generating unit9or the X-ray detector90), and data showing the offset value of the output signal (signal S2) from the X-ray detector90and a plurality of values (values for providing an allowance of the detection sensitivity) near the offset value. The offset value stored in the EP-ROM93ais an offset value actually measured in advance by using the trigger generating unit9. A plurality of offset values corresponding to the use environment (for example, temperature) of the optical image acquiring part5may be stored in the EP-ROM93a. In this case, the memory3aof the PC3stores various data showing a correction value for the offset value and the resolution for image reading for each model number and serial number of the optical image acquiring part5(or the trigger generating unit9or X-ray detector90) and each use environment (for example, temperature) of the optical image acquiring part5, and the PC3performs various controls of trigger data generation and image reading, etc., by the controller6based on the above-described various data stored in the memory3a.

The comparator93bis connected to the detected signal line L11and the connector81. The comparator93bis connected to the trigger processor62and the D/A converter66via the connector81. The comparator93bcompares the signal S2input via the detected signal line L11and the reference signal S3input via the connector81from the D/A converter66. Then as shown inFIG. 4(a) andFIG. 4(b), the comparator93boutputs the pulse P2of the trigger signal S4when the value of the signal S2exceeds the value of the reference signal S3. When steady X-ray irradiation corresponding to a voltage waveform of a complete DC voltage is performed by the X-ray irradiation device1, as shown inFIG. 4(a), the trigger signal S4includes the pulse P2with a pulse width substantially corresponding to the entire X-ray irradiation period T1(pulse width of pulse P1). When periodic X-ray irradiation corresponding to a half-wave rectified waveform of an AC power supply voltage is performed by the X-ray irradiation device1, as shown inFIG. 4(b), the trigger signal S4includes a plurality of pulses P4corresponding to the pulses P3.

Next, operations of the X-ray imaging device2will be described with reference toFIG. 5. When the trigger signal S4is input from the trigger generating unit9, the trigger processor62outputs trigger data showing an X-ray image imaging start timing and trigger data showing an imaging end timing to the signal processor61according to this trigger signal S4. In this case, when the trigger processor62detects a rise timing of the pulse P2(or pulse P4), in synchronization with this timing, outputs trigger data showing an imaging start timing to the signal processor61. Then, in synchronization with a timing at which a predetermined period T11(period preset corresponding to the entire X-ray irradiation period T1) has elapsed from the rise timing of the pulse P2(or pulse P4), the trigger processor62outputs trigger data showing an imaging end timing to the signal processor61(first imaging mode). The first imaging mode can be applied to both the case where steady X-ray irradiation corresponding to the voltage waveform of a complete DC voltage is performed by the X-ray irradiation device1and the case where periodic X-ray irradiation corresponding to the half-wave rectified waveform of an AC power supply voltage is performed by the X-ray irradiation device1.FIG. 5(a) is a timing chart of the first imaging mode applied for the signal S4including the pulses P4. When steady X-ray irradiation corresponding to a voltage waveform of a complete DC voltage is performed by the X-ray irradiation device1, instead of the first imaging mode, as shown inFIG. 5(b), the trigger processor62can output trigger data showing an imaging end timing in synchronization with a fall timing of the pulse P2(second imaging mode).

When steady X-ray irradiation corresponding to a voltage waveform of a complete DC voltage is performed by the X-ray irradiation device1, the trigger processor62is set to either imaging mode of the first imaging mode or the second imaging mode based on command data transmitted via the signal processor61from the PC3. On the other hand, when periodic X-ray irradiation corresponding to a half-wave rectified waveform of an AC power supply voltage is performed by the X-ray irradiation device1, the trigger processor62is set to the first imaging mode. The X-ray imaging device2may be configured so that the imaging end timing in the first imaging mode is detected not by the trigger processor62but by the signal processor61. The CCD driver65outputs a pulse P5(control signal S5) with a pulse width corresponding to the imaging period (period T11or the entire X-ray irradiation period T1) since trigger data showing an imaging start timing is input into the signal processor61until trigger data showing an imaging end timing is input into the signal processor61to the imager7based on control by the signal processor61. The imager7starts imaging (accumulation of image information) in synchronization with a rise timing of the pulse P5, and ends imaging in synchronization with a fall timing of the pulse P5. Thereafter, the signal processor61reads image information accumulated in the imaging period by the imager7(period T2). In this case, the CCD controller73of the imager7alternately reads a horizontal component (horizontal direction) and a vertical component (vertical direction) of image information according to a resolution designated in advance via the PC3, etc., based on control by the signal processor61. Image information thus read from the CCD72by the CCD controller73is successively converted into image data by the A/D converter64, and the image data is loaded into the signal processor61. Then, after the period T2, the signal processor61transfers the image data loaded from the imager7via the A/D converter64to the PC3via the I/O controller63in order (period T3).

As described above, the offset value of the X-ray detector90is stored in the EP-ROM93a, so that the offset value is read from the EP-ROM93a, and based on this offset value, the reference signal S3to be used for trigger signal generation is generated. Thus, the offset value is stored in advance in the EP-ROM93a, so that each time of trigger generation, there is no need to adjust the reference signal S3to be used for trigger signal generation according to variation in the offset value of each X-ray detector90. In addition, data such as the model number and the serial number of the optical image acquiring part5(or the trigger generating unit9or the X-ray detector90) are stored in the EP-ROM93a, so that these data are prevented from being falsified or lost. Further, according to the model number and the serial number of the optical image acquiring part5(or the trigger generating unit9or the X-ray detector90) stored in the EP-ROM93aand the use environment (for example, temperature), etc., of the optical image acquiring part5, etc., correction, etc., of the offset value can be performed easily by software via the PC3. Therefore, regardless of fluctuations in the use environment of the optical image acquiring part5, trigger signal generation (acquisition of the imaging start timing) can be reliably performed. Therefore, the convenience is improved and erroneous operation and erroneous detection are suppressed. A plurality of correction values for the offset value can be used, so that the trigger detection sensitivity can be flexibly adjusted. There is no need to use a trimmer resistance which is normally used in the trigger generator93to cope with the variation in the offset value of the X-ray detector90, so that the device configuration of the trigger generator93becomes simple, and the cost is reduced. Further, when the reference signal S3is generated based on the offset value and the irradiation intensity of the X-ray XR detected by the X-ray detector90, the imaging start timing and the imaging end timing can be reliably acquired regardless of fluctuation in the irradiation intensity of the X-ray XR.

Second Embodiment

An X-ray imaging system10of a second embodiment includes an X-ray imaging device2ashown inFIG. 6instead of the X-ray imaging device2of the first embodiment. First, a configuration of the X-ray imaging device2ais described. The X-ray imaging device2aincludes a controller6aand a trigger generating unit9ainstead of the controller6and the trigger generating unit9of the X-ray imaging device2. The controller6afurther includes an A/D converter68in addition to the configuration of the controller6. The A/D converter68is connected to the amplifier92via the connector81, a trigger generator931, and the signal cable L1. The A/D converter68is connected to the signal processor61. The A/D converter68converts a signal S2input from the amplifier92into digital data, and outputs digital data showing this signal S2to the signal processor61. The signal processor61acquires an offset value of the X-ray detector90included in this signal S2based on digital data showing the signal S2input from the A/D converter68, and generates reference data showing a reference value for trigger data generation based on this acquired offset value (or this offset value and an irradiation intensity of the X-ray XR). Then, the signal processor61outputs this generated reference data to the D/A converter66via the I/O controller63. The reference data is converted into an analog signal (an analog signal showing a reference value for trigger data generation, corresponding to the reference signal S3of the first embodiment) by the D/A converter66, and output to the trigger processor62. The trigger processor62is connected to the amplifier92via the connector81, the trigger generator931, and the signal cable L1. The trigger processor62is connected to the signal processor61and the D/A converter66. The trigger processor62of the second embodiment performs the same processing as that of the comparator93bbased on the signal S2input from the amplifier92and the analog signal (analog signal showing a reference value for trigger data generation) input from the D/A converter66. The A/D converter68converts the signal S2input from the amplifier92into digital data, and outputs this digital data to the signal processor61.

The trigger generating unit9aincludes a trigger generator931instead of the trigger generator93of the trigger generating unit9as shown inFIG. 7. The trigger generator931includes EP-ROM93a, however, it does not include the comparator93b. The signal S2input from the amplifier92is directly output to the trigger processor62and the A/D converter68via the signal cable L1, the trigger generator931, and the connector81. The EP-ROM93ais connected to the signal processor61of the controller6avia the connector81. The EP-ROM93astores data such as the model number, the serial number, the manufacturing date, and the shipment history of the optical image acquiring part (or the trigger generating unit9aor the X-ray detector90). In this case, the memory3aof the PC3stores reference data showing a reference value for trigger data generation and data showing a resolution for image reading for each data showing the model number and the serial number of the optical image acquiring part5(or the trigger generating unit9aand the X-ray detector90). The PC3performs various controls for trigger data generation and image reading, etc., by the X-ray imaging device2based on the various data stored in the memory3a.

Next, operations of the X-ray imaging device2aof the second embodiment will be described. When the signal S2is input from the trigger generating unit9a, the trigger processor62generates trigger data showing an X-ray image imaging start timing and trigger data showing an imaging end timing based on the signal S2and an analog signal (analog signal showing a reference value for trigger data generation) input from the D/A converter66, and outputs these trigger data to the signal processor61. The subsequent operations of the X-ray imaging device2aare described by replacing the signal S4, the pulse P2, and the pulse P4in the description of the operations of the X-ray imaging device2of the first embodiment andFIG. 5by the signal S2, the pulse P1, and the pulse P3, respectively.

As described above, the X-ray imaging device2aof the second embodiment generates reference data showing a reference value for trigger data generation based on the signal S2from the X-ray detector90. Therefore, preferable reference data for trigger data generation can be generated each time of X-ray imaging. Therefore, the imaging start timing and the imaging end timing can be reliably acquired. The trigger generator93does not use the comparator93b, so that the device configuration of the trigger generator931becomes simple, and the cost is reduced. Further, data such as the model number and the serial number of the optical image acquiring part5(or the trigger generating unit9aor the X-ray detector90) are written on the EP-ROM93a, so that these data are prevented from being falsified or lost. The reference data for trigger data generation is generated according to the irradiation intensity of the X-ray XR irradiated by the X-ray irradiation device1, so that the imaging start timing and the imaging end timing can be reliably acquired regardless of fluctuation in the irradiation intensity of the X-ray XR.

Further, the present invention is not limited to the first and second embodiments, and can be variously modified. For example, in place of the trigger generator93and the EP-ROM93aof the trigger generator931, a writable/readable flash memory can be used. In this case, by using the PC3, data in the memory can be easily written, rewritten, and deleted. Therefore, data such as the model number and the serial number, the offset value (and the correction value thereof), and the use environment (for example, the temperature) of the optical image acquiring part5(or the trigger generating unit9, the trigger generating unit9a, and the X-ray detector90) can be easily updated.