JP2001211392A - Method and device for optical signal acquisition and photographing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a method and a device for optical signal acquisition, which are not affected by an output for the dark current of a CCD, and a photographing device using this device for optical signal acquisition. SOLUTION: An optical signal is received by the CCD (1), and an electric signal stored in the CCD is read out multiple times at interval of a time t shorter than an input time Tb of the optical signal (2), and read signals are totally added after being corrected on the basis of the output for the dark current of the CCD (3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and an apparatus for acquiring an optical signal and an imaging apparatus, and more particularly to a charge coupled device (CCD: Charge Couple).
The present invention relates to a method and an apparatus for acquiring an optical signal using (d Device) and an imaging apparatus using a CCD.

[0002]

2. Description of the Related Art In an X-ray imaging apparatus, that is, an X-ray imaging apparatus, a transmission X-ray signal is obtained for an imaging target using an X-ray irradiation / detection apparatus, and the imaging target is acquired based on the transmission X-ray signal. Generate a projection image.

In generating a projection image, for example, an image intensifier (Image Intensifier) is used.
The two-dimensional distribution of the transmitted X-rays is converted into a two-dimensional distribution of light by a method such as fier), and the two-dimensional distribution of charges is received by a CCD to form a two-dimensional distribution of electric charges. .

[0004]

A CCD requires an accumulation time for accumulating electric charges. The accumulation time corresponds to the exposure time in silver halide photography, and is adjusted so that the amount of accumulated charges is appropriate. The adjustment of the accumulation time is performed by adjusting the X-ray irradiation time.

Since the output of the CCD at dark time is proportional to the accumulation time, as the accumulation time, that is, the X-ray irradiation time becomes longer, the output at dark time increases and the quality of the image deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a device for acquiring an optical signal which is not affected by the output of a CCD during dark light, and a photographing apparatus using such an optical signal acquiring device.

[0007]

Means for Solving the Problems (1) According to one aspect of the invention for solving the above-described problems, an optical signal is received by a charge-coupled device, and an electric signal stored in the charge-coupled device is stored. The signal is read out a plurality of times at a time interval shorter than the input time of the optical signal, and the electrical signals read out a plurality of times are respectively charged into the charge coupled
A method for obtaining an optical signal, comprising: correcting based on an output at the time of darkening of a device; and fully adding the corrected electric signal.

According to the invention from this viewpoint, the charge stored in the CCD is read out a plurality of times at a time interval shorter than the input time of the optical signal, and the readout signal of each time is corrected by the dark-time output and added up. This makes it possible to obtain a CCD output signal corresponding to a long accumulation time that does not include the output during dark time.

(2) According to another aspect of the present invention, there is provided a charge coupled device for receiving an optical signal.
A device, reading means for reading the electric signal accumulated by the charge-coupled device a plurality of times at a time interval shorter than the input time of the optical signal, and reading the electric signal read a plurality of times from the charge-coupled device. An optical signal acquisition device comprising: a correction unit that corrects based on an electric power output; and an addition unit that fully adds the corrected electric signal.

In the invention according to this aspect, the reading means includes:
The charge stored in the CCD is read out a plurality of times at a time interval shorter than the input time of the optical signal, the readout signal is corrected by the correction means with the output at the time of darkness, and the corrected signal is fully added by the addition means. This makes it possible to obtain a CCD output signal corresponding to a long accumulation time that does not include the output during dark time.

(3) According to another aspect of the present invention, there is provided a charge-coupled device for receiving a two-dimensionally distributed optical signal, and an electric charge stored in the charge-coupled device. Reading means for reading a signal a plurality of times at a time interval shorter than the input time of the optical signal; correcting means for correcting the electric signals read a plurality of times based on the dark-time output of the charge-coupled device; An image capturing apparatus comprising: an adding unit that performs full addition of corrected electrical signals for each pixel; and an image generating unit that generates an image based on the fully added electrical signals.

In the invention according to this aspect, the reading means includes:
The charge stored in the CCD is read out a plurality of times at a time interval shorter than the input time of the optical signal, and the readout signal of each time is corrected by the output at the dark time by the correction means, and the corrected signal is fully added for each pixel by the addition means. I do. This makes it possible to obtain a CCD output signal corresponding to a long accumulation time that does not include the output during dark time. Further, the image generating means can generate a high-quality image based on such a signal.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the X-ray imaging apparatus. This apparatus is an example of an embodiment of the photographing apparatus of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

As shown in FIG. 1, the present apparatus has an X-ray tube 2 and an image intensifier 4. The X-ray tube 2 and the image intensifier 4 are supported by support means (not shown), and face each other with a space therebetween. An imaging target 6 is mounted on a support plate 8 and carried into a space where the X-ray tube 2 and the image intensifier 4 face each other.

The X-ray tube 2 is directed toward an object 6 to be imaged, for example, a cone-shaped X-ray beam (beam) 10.
Is irradiated. Thereby, the imaging target 6 by the transmission X-ray
Is projected on the input surface of the image intensifier 4. The image intensifier 4 produces a fluorescent image representing an X-ray projection image on an output surface. Fluorescent image of output surface is C
An image is taken by a CD camera (camera) 12. The CCD camera 12 incorporates a charge-coupled device (CCD), not shown, and uses it as an image receiving means. The charge-coupled device is an example of the embodiment of the charge-coupled device according to the present invention.

The light amount on the output surface is determined by an optical sensor.
It is detected at 14. As the optical sensor 14, for example, a photomultiplier is used.
Are used.

The X-ray tube 2 is supplied with electric power from a high-voltage generator 20. The high-voltage generating unit 20 is controlled by the imaging control unit 22 and turns on / off X-ray irradiation with a predetermined tube voltage and tube current. The imaging control unit 22 includes:
Photographing is performed based on a light amount detection signal input from the optical sensor 14 and an operation signal input from the operation unit 24. The function of the imaging control unit 22 is realized by, for example, a computer.

The CCD camera 12 has a CCD reading section 26
Supplies a CCD read signal. CCD readout unit 26
Is an example of an embodiment of a reading unit according to the present invention. The captured image is stored in the CCD as electric charges corresponding to the luminance of the pixels, and the electric charges are read out for each pixel by a CCD readout signal.

The CCD reading section 26 is provided with control information from the photographing control section 22, and the CCD is read based on the control information. The function of the CCD reading unit 26 is realized by, for example, a computer or the like. Readout of the CCD will be described later.

The read image is input to the image processing section 28. The image processing unit 28 performs a predetermined process on the input image. The image processing unit 28 is supplied with control information from the CCD reading unit 26, and performs image processing based on the control information.
The function of the image processing unit 28 is realized by, for example, a computer. The image processing will be described later.

The image processed by the image processing section 28 is stored in a memory (not shown). The image is also displayed on the display unit 30. As a result, the X-ray projection image is displayed as a visible image.

The operation of the present apparatus will be described. FIG. 2 shows a flow chart of the operation of the present apparatus. The operation of this apparatus is performed under the control of the imaging control unit 22. As shown in the figure, first, at step (step) 502, a fluoroscopy of the imaging target is performed, and the operator observes the fluoroscopic image of the imaging region displayed on the display unit 30. The X-ray irradiation conditions at the time of fluoroscopy are determined in advance according to the imaging region, and are appropriately adjusted according to the state of the fluoroscopic image.

At step 504, the imaging conditions are predicted based on the X-ray irradiation conditions at the time of fluoroscopy. The predicted shooting conditions include a tube voltage, a tube current, and a predicted shooting time for shooting. Next, in step 506, it is determined whether or not the predicted shooting time T is longer than a predetermined reference value a. Reference value a
Is selected as the shooting time during which the dark output of the CCD falls within the allowable range.

If the predicted shooting time T is not longer than the reference value a, the normal mode is set in step 508, and if the predicted shooting time T is longer than the reference value a, the digital addition mode (step 510) is set in step 510. mode)
Set.

In the case of the normal mode, normal X-ray photography is performed in step 512. The imaging control unit 22 determines the tube voltage and the tube current at the time of imaging based on the X-ray irradiation conditions at the time of fluoroscopy, and irradiates the high-voltage generation unit 20 with the X-ray by using an imaging signal as shown in FIG. Command. X-rays are emitted according to the imaging signal, and a projection image of the imaging target 6 appears as a fluorescent image on the output surface of the image intensifier 4. This fluorescent image is captured by the CCD camera 12.

When the input signal from the optical sensor 14 reaches a predetermined level (level), that is, when an appropriate exposure state is reached, the imaging control unit 22 stops sending the imaging signal and stops X-ray irradiation. Thereby, as shown in (1) of FIG. 3, X-ray imaging in which the imaging time is Ta is performed,
The corresponding charge accumulates on the CCD.

The accumulated charges are read out by the CCD reading section 26 at the timing shown in FIG. The dark-time output accumulated before photographing is reset by the first read signal, and the image accumulation signal is read by the second read signal.

The image processing section 28 collects the readout signals at the timing shown in FIG. 3C and forms an image based on the collected signals. The formed images are stored in a memory (not shown).
y).

In the case of the digital addition mode, in step 512, X-ray photography in the digital addition mode is performed. In this case, as shown in (1) of FIG. 4, the photographing time by the proper exposure is Tb (> Ta).

The CCD reading section 26 repeatedly reads the CCD at time intervals t, as shown in FIG. The accumulation of dark output is reset by the first readout signal, and the image accumulation signals are read out by the second and subsequent readout signals. The image accumulation signal is reset each time the data is read. While the photographing signal continues, the image signal is accumulated again until the next readout. As the time interval t, for example, an image display interval during fluoroscopy (1/30 sec) or the like is used. The reading time interval t is not limited to this, and may be an appropriate interval.

Each time the CCD read value is input to the image processing unit 28 and collected at the timing shown in FIG. The collected signals are fully added in the image processing unit 28. FIG. 5 is a block diagram of the image processing unit 28 from the viewpoint of adding read signals.

As shown in the figure, the image processing unit 28 performs dark-light output correction on the readout signal by the dark-light output correction unit (unit) 32. Output correction at dark
This is performed by subtracting the dark-time output corresponding to the read time interval t based on the previously known dark-time output characteristics of the CCD. The dark output correction unit 32 is an example of an embodiment of a correction unit in the present invention.

The corrected read signals of each time are sequentially added by the adding unit 34. The addition is performed pixel by pixel. As described above, by fully adding the readout signals after the dark-time output correction, it is possible to obtain image data with a wide dynamic range (dynamic range) not including the dark-time output. The addition unit 34 is an example of an embodiment of an addition unit in the present invention.

An image is formed by the image forming unit 36 based on such image data. Image forming unit 3
FIG. 6 shows an example of an embodiment of an image generating means according to the present invention. Since the dynamic range of the image data output from the addition unit 34 is wide, a high-quality image can be obtained. The obtained image is stored in the memory.

Steps 514 to 502 are performed until the photographing of all scheduled images is completed.
Return to and repeat.

In the above, an example in which X-rays are used as radiation has been described. However, the radiation is not limited to X-rays, and may be other types of radiation such as γ-rays. However, at present, X-rays are preferable because practical means regarding generation, detection, control, and the like are the most substantial.

Also, an example has been described in which a fluorescent image generated on the output surface of the image intensifier is photographed. However, the image to be photographed is not limited to a fluorescent image representing a radiation image, but a normal optical image formed through a lens. Of course, it can be an image.

[0038]

As described above in detail, according to the present invention, a method and an apparatus for acquiring an optical signal which is not affected by an output of a CCD at the time of darkness, and a photographing apparatus using such an optical signal acquiring apparatus Can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a flowchart of the operation of the apparatus shown in FIG. 1;

FIG. 3 is a time chart of the operation of the device shown in FIG. 1;

4 is a time chart of the operation of the device shown in FIG.

FIG. 5 is a block diagram of an image processing unit.

[Explanation of symbols]

 Reference Signs List 2 X-ray tube 4 Image intensifier 6 Object to be photographed 8 Support plate 10 X-ray beam 12 CCD camera 14 Optical sensor 20 High-voltage generating unit 22 Imaging control unit 24 Operation unit 26 CCD reading unit 28 Image processing unit 30 Display unit 32 Dark Power output correction unit 34 Addition unit 36 Image forming unit

Claims (9)

[Claims] An optical signal is received by a charge-coupled device, and an electric signal accumulated by the charge-coupled device is read a plurality of times at a time interval shorter than an input time of the optical signal; 3. A method for acquiring an optical signal, comprising: correcting signals based on dark-time output of the charge-coupled device; and adding the corrected electric signals. 2. The method according to claim 1, wherein the optical signal is obtained by converting radiation. 3. The method according to claim 2, wherein the radiation is X-rays. 4. A charge-coupled device for receiving an optical signal.
A device; reading means for reading the electric signal accumulated by the charge-coupled device a plurality of times at a time interval shorter than the input time of the optical signal; and reading the electric signal read a plurality of times from the charge-coupled device. An optical signal acquisition device comprising: a correction unit that corrects based on an electric power output; and an addition unit that fully adds the corrected electric signal. 5. The optical signal acquisition device according to claim 4, wherein said optical signal is obtained by converting radiation. 6. The optical signal acquisition device according to claim 5, wherein the radiation is an X-ray. 7. A charge-coupled device for receiving a two-dimensionally distributed optical signal, and reading the electrical signal accumulated by the charge-coupled device a plurality of times at a time interval shorter than the input time of the optical signal Means for correcting the electric signals read out a plurality of times based on the dark-time output of the charge-coupled device, and adding means for fully adding the corrected electric signals for each pixel; An image generating means for generating an image based on the fully added electric signal. 8. The imaging apparatus according to claim 7, wherein the optical signal is obtained by converting radiation. 9. The imaging apparatus according to claim 8, wherein the radiation is an X-ray.