JP2001296367A - Image information detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an image information detecting device using an image detector having a photoconductor sandwiched between electrodes free of disconnection breakage when a voltage is applied between the electrodes. SOLUTION: A bias switching means 4 which has switches SW1 and SW2 is provided between a high-voltage power source 40 and an image detector 10. Resistances R1 and R2 which function as a rush current suppressing means are provided between both input terminals (a) and (b) of the switch SW1 and the output terminal of the high-voltage power source 40. The output terminal of the switch SW1 is connected to the input terminal (a) of the switch SW2, and the output terminal of the switch SW2 is connected to an electrode layer 11 of the image detector 10. The input terminal (b) of the switch SW2 is grounded. An element 15a of the image detector 10 is grounded through a charge amplifier IC 33. When a voltage is applied to the image detector 10 and ceased, a rush current due to the capacity of the image detector 10 is limited by the resistances R1 and RT2, so breakage such as disconnection is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image information detecting apparatus, and more particularly, to an image information detecting apparatus provided with an image detector having a photoconductor which generates electric charge by being irradiated with electromagnetic waves such as radiation and exhibits conductivity. The present invention relates to an apparatus for recording image information and reading image information in a state where a voltage is applied to the image detector or a state where the application of the voltage is stopped.

[0002]

2. Description of the Related Art Conventionally, a facsimile, a copying machine, a radiation imaging apparatus, and the like have been known as apparatuses using an image detector.

In medical X-ray imaging, a photoconductor such as a selenium plate made of, for example, a-Se, which is sensitive to radiation such as X-rays, is used to reduce the exposure dose to a subject and improve diagnostic performance. A radiation solid-state detector (electrostatic recording medium) as an image detector, irradiating the image detector with X-rays, and storing an amount of electric charge corresponding to the dose of the irradiated X-rays in a power storage unit in the image detector By storing the radiation image information as an electrostatic latent image in the power storage unit by accumulating it as a latent image charge, and scanning the image detector on which the radiation image information is recorded with a laser beam or line light as reading light, Systems for reading radiation image information from the image detector have been proposed, and various types of image detectors have been proposed for use in these systems (for example, US Pat. No. 5,268,569). No., International Publication No. 59261, 1998
JP 9-5906, Japanese Patent Application No. Hei 10-232824 by the present applicant,
Nos. 10-271374 and 11-87922).

[0004]

As described above, various image detectors have been proposed. However, when recording image information or reading image information using these image detectors, at least an image detector is required. Once the voltage is applied to the detector, the image information is recorded or the image information is read while the voltage is applied to the image detector, or the application is stopped or the image detector is short-circuited. Basically, on / off control of voltage application to the image detector is performed.

When an image detector having a structure in which a photoconductor such as a-Se is sandwiched between electrodes is used, the charge generation efficiency in the photoconductor is increased, and an image with a good S / N ratio is obtained.
A high voltage of kV or more must be applied between the electrodes.
More specifically, in general radiography, the thickness of a-Se as a photoconductor is required to be 500 μm or more, and in this case, the potential gradient in the photoconductor is 10 ^5.
V / cm or more, and in order to generate an avalanche amplification effect in order to further increase the charge generation efficiency, it is set to be 10 ⁶ V / cm or more. The application of a voltage is required.

On the other hand, since the photoconductor is sandwiched between the electrodes, the image detector also functions as a capacitor and has a capacity. When on / off control of voltage application to the image detector is performed, the voltage When switching the application, a large charging current or discharging current, a so-called inrush current, flows, and breakage such as disconnection may occur at a location where the inrush current concentrates, for example, at an electrode portion to which a power cable is connected.

As a method for solving such a problem, for example, US Pat. No. 5,773,839 discloses a method of inserting a current limiting resistor between a power supply and an image detector, and US Pat. No. 5,969,360. Discloses a method of suppressing an inrush current by gradually increasing or decreasing the voltage applied to an image detector.

However, when a resistor is inserted as in US Pat. No. 5,773,839, for example, when obtaining an image signal corresponding to the accumulated charge of the image detector, the response deteriorates due to the effect of the resistor, and high-speed reading cannot be performed. Problems arise.

Further, US Pat. No. 5,969,360 does not disclose a specific method for gradually increasing or decreasing the applied voltage.

The present invention has been made in view of the above circumstances, and has excellent responsiveness. Even if on / off control of a high voltage applied to an image detector is performed, destruction such as smoke or disconnection due to an inrush current can be achieved. It is an object of the present invention to provide an image information detecting device that does not occur.

[0011]

According to the image information detecting apparatus of the present invention, a photoconductor which generates electric charges by being irradiated with an electromagnetic wave and two electrode layers sandwiching the photoconductor are provided. An image detector distributed in a dimensional manner, a power supply, voltage application control means for turning on / off the application of a voltage output from the power supply between the two electrode layers, and a charge amount generated by the photoconductor. An image signal acquiring unit for acquiring an image signal by acquiring an electric signal of a corresponding magnitude, wherein the power supply outputs a voltage of 1 KV or more; The rush current generated when the application of the voltage is stopped is reduced so that the rush current does not cause destruction of at least one of the image detector, the voltage application control means, and the image signal acquisition means, and more preferably all three. Is characterized in that the provided suppressing inrush current suppression means to the size.

There are various types of image detectors, but any type of image detector may be used as long as it has at least a photoconductor and two electrode layers are provided so as to sandwich the photoconductor. For example, as proposed by the present applicant in Japanese Patent Application Nos. Hei 10-232824 and No. 11-87922, a latent image polarity charge is generated by being irradiated with a recording electromagnetic wave carrying image information. A recording photoconductive layer, a power storage unit for storing the latent image polarity charge, and a reading photoconductive layer for generating a charge by being irradiated with a reading electromagnetic wave; A type that can be recorded as a latent image or a type that detects stimulated emission light emitted from a stimulable phosphor sheet as proposed by the present applicant in Japanese Patent Application No. 2000-50201-3. And the like. For these various detectors, it is necessary to apply a relatively high voltage or short-circuit between the two electrode layers sandwiching the photoconductor in the process of recording or reading for high S / N and high-speed reading. Things.

In order to obtain a high S / N, as described above,
This is why the potential gradient in the photoconductor needs to be 10 ⁵ V / cm or more, and a power supply that outputs a voltage of 1 KV or more is used.

Turning on / off the application of the voltage output from the power supply between the two electrode layers means applying a voltage between the two electrode layers, stopping the applied voltage, and short-circuiting the electrode layers. This is different from the above-mentioned US Pat. No. 5,773,839 in that reading must be performed in a power-supply stop state in which a resistor is inserted.

The rush current suppressing means used in the image information detecting device of the present invention includes an image detector, a voltage application control means, and a rush current at both the start of voltage application and the stop of voltage application. Any type may be used as long as the inrush current can be suppressed to such an extent that the image signal acquisition means is not destroyed. Preferably, it is a resistor disposed between the vessel and the vessel.

When a resistor is used as the rush current suppressing means, a voltage is applied from the power supply to the image detector via the resistor, and the voltage application to the image detector via the resistor is stopped. When the voltage between the two electrode layers becomes such that the breakdown does not occur due to an excessive current even if the two electrode layers are short-circuited, for example, the voltage between the two electrode layers of the image detector becomes substantially zero. Next, the voltage application control means is configured to short-circuit between both electrode layers.

The voltage application control means used in the image information detecting apparatus of the present invention preferably has a sufficiently low on-resistance and an extremely low off-resistance, and includes a relay and a drive control for driving and controlling the relay. Preferably, it comprises means.

When the high voltage applied to the image detector is switched by using a relay, the contact may be deteriorated due to chattering, or the image detector and peripheral circuits may be destroyed due to spike current due to arc discharge. To avoid these, it is preferable to use a reed relay where the contacts are located below atmospheric pressure.

[0019]

According to the image detecting apparatus of the present invention, the rush current suppressing means for suppressing the rush current to such a size that the image detector or the like does not break down is provided. Is short-circuited,
It is possible to make the device highly reliable and capable of high-speed reading. In addition, since a power supply that outputs a voltage of 1 KV or more is used, the charge generation efficiency in the photoconductor is increased and S
/ N can be obtained.

If a resistor is used as the rush current suppressing means,
The circuit configuration becomes simple, and even if the present invention is implemented, the cost increase is small.

Further, if the voltage application control means is composed of a relay having sufficiently small on-resistance and extremely small off-resistance and a drive control means for controlling the driving of the relay, the voltage application can be properly switched.

By using a reed relay whose contact point is lower than the atmospheric pressure, problems such as breakage due to arc discharge can be solved.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a side sectional view showing a schematic configuration of a chest imaging apparatus 1 according to one embodiment of the present invention. As shown in FIG. 1, the chest imaging apparatus 1 has an imaging unit 4 supported on an imaging support column 3 via a not-shown actuator such as a ball screw or a cylinder so as to be able to move up and down.

The imaging unit 4 includes a radiation image detector 10 as an imaging device formed on a glass substrate 5, a base 6 further holding the glass substrate 5 on which the image detector 10 is disposed, The exposure light source unit 20 for reading used when reading the radiation image information recorded in the detector 10, and the current flowing out of the image detector 10 when the scanning exposure light source unit 20 scans and exposes the image detector 10 is detected. A current detecting means 30 for obtaining an image signal; a high-voltage power supply unit 45 for applying a predetermined voltage to the image detector 10;
A pre-exposure light source unit 60 that irradiates the pre-exposure light to a light source 0 and a light-transmitting part that is arranged on the side facing the subject of the image detector 10 that absorbs scattered rays generated by the radiation transmitted through the subject (not shown) being scattered by the subject. A dynamic grid 70 and the grid 7
0, a control printed circuit board 80 constituting control means for controlling the pre-exposure section 60 and the reading exposure light source section 20 are arranged in the housing 2.

The image pickup section 4 receives the image signal from the current detecting means 30 through the inside of the support column 3 and outputs the image signal to the external image processing apparatus 1.
A signal cable 90 for outputting to the power supply 50 and a power cable 92 connected to an external AC (alternating current) power supply 152 through the inside of the support column 3 are provided.

As described above, since each element for recording and reading an image is housed in one housing 2,
The imaging unit 4 is compact and compact, and can be easily moved, which is practical.

The current detecting means 30 includes a printed circuit board 31,
A relatively short TAB with one end connected to the printed circuit board 31
(Tape Automated Bonding) Film 32 and Charge Amplifier IC Mounted on TAB Film 32
33. The other end of the TAB film 32 is connected to the image detector 10.

FIG. 2 is a diagram showing an arrangement relationship between an example of the image detector 10 and the exposure light source unit 20 for reading. In FIG. 2, a base 6, which will be described later, is omitted.

The image detector 10 records the radiation image information as an electrostatic latent image, and generates a current corresponding to the electrostatic latent image by being scanned with an electromagnetic wave for reading (hereinafter referred to as reading light). Specifically, as shown in FIG. 2, it is formed on a glass substrate 5 and has transparency to recording electromagnetic waves (hereinafter, referred to as recording light) such as X-rays transmitted through a subject. The first conductive layer 11, the recording photoconductive layer 12 which generates electric charge by being irradiated with the recording light and exhibits conductivity, and the latent image polar charge (for example, negative charge) charged on the first conductive layer 11. The charge transport layer 13 acts substantially as an insulator and acts substantially as a conductor for transport polarity charges (positive charges in the previous example) having a polarity opposite to the polarity of the latent image. Generates electric charge upon receiving to exhibit conductivity Preparative photoconductive layer 14, in which the second conductive layer 15 permeable to the reading light are laminated in this order. Recording photoconductive layer 12 and charge transport layer 13
A power storage unit 19 is formed at the interface with the semiconductor device.

The first conductive layer 11 and the second conductive layer 15 form electrodes, respectively. The electrode of the first conductive layer 11 is a two-dimensionally flat plate electrode, and the electrode of the second conductive layer 15 is As shown by oblique lines in the figure, a large number of elements (linear electrodes) 15a are formed as stripe electrodes arranged in a stripe at a pixel pitch (for example, see the electrostatic recording medium described in Japanese Patent Application No. 10-232824). . The arrangement direction of the elements 15a corresponds to the main scanning direction, and the longitudinal direction of the elements 15a corresponds to the sub-scanning direction.

The reading photoconductive layer 14 has high sensitivity to electromagnetic waves having wavelengths in the near-ultraviolet to blue region (300 to 550 nm), and has a wavelength in the red region (700 nm or more).
Those with low sensitivity to electromagnetic waves, specifically,
a-Se, PbI2, Bi12 (Ge, Si) O20,
At least one of perylene bisimide (R = n-propyl) and perylene bisimide (R = n-neopentyl)
A photoconductive substance containing one as a main component is preferable. In this embodiment, a-Se is used.

In this embodiment, the element 1
5a has a width of 50 μm, is arranged at a pixel pitch of 100 μm, and is made of a material that transmits light having a wavelength of 550 nm or less, for example, ITO or thin film Al.

The reading exposure light source section 20 is provided with a light source (not shown) for outputting reading light and an optical system (not shown) for irradiating the light output from the light source on the image detector 10 in a linear manner. By moving the light source and the optical system in the longitudinal direction of the element 15a of the image detector 10 while maintaining a necessary distance from the image detector 10, a linear reading is performed over the entire surface of the image detector 10 by a linear motor that does not. The scanning is performed by light.

As described above, the reading photoconductive layer 14 has high sensitivity to electromagnetic waves in the wavelength range of near ultraviolet to blue (300 to 550 nm), and has a wavelength in the red range (700 to 550 nm).
(nm or more), a light source that outputs light having a wavelength in the near ultraviolet to blue region of 550 nm or less is used.

Examples of the light source that emits reading light include a light source composed of a large number of LED chips and LD chips arranged in a line, and an L light source in which a plurality of light emitting points are originally formed in a line.
An ED array or an LD array may be used. Also,
For example, as proposed by the present applicant in Japanese Patent Application No. 11-242876, a planar light source integrally formed with an image detector in which a minute light source is arranged in a planar shape, and the planar light source If a reading exposure light source unit including a light source control unit for controlling is used, a space for moving the light source and a linear motor for moving the light source are not required, so that the entire apparatus can be configured more compactly. In addition, if the planar light source and the light source control means are configured to also serve as the pre-exposure light source section, it is not necessary to provide a special pre-exposure light source, so that the apparatus can be made more compact and the number of parts of the apparatus can be reduced. Therefore, an inexpensive device can be obtained.

As the pre-exposure light source section 60, a light source which emits / extincts light in a short time and has very little afterglow is required. In this embodiment, an external electrode type rare gas fluorescent lamp is used. Specifically, the pre-exposure light source unit 60 includes, as shown in FIG.
A plurality of external electrode type rare gas fluorescent lamps 61 extending in the depth direction of the paper in the drawing, a wavelength selection filter 62 inserted between the fluorescent lamp 61 and the image detector 10, a fluorescent lamp 61
And a reflection plate 63 for efficiently reflecting the light output from the fluorescent lamp 61 to the image detector 10 side. The pre-exposure light only needs to irradiate the entire surface of the second electrode layer 15 of the image detector 10, and no particular light condensing means is required. However, the smaller the illuminance distribution, the better. Instead of the fluorescent lamp, for example, a light source in which LED chips are arranged in a plane can be used. Further, by providing the base 6 with wavelength selectivity, the wavelength selection filter 62 can be omitted.

When the electrostatic latent image is read from the image detector 10, basically all the stored latent image charges can be read out, but in some cases, the latent image charges cannot be completely read out and the image It may be read and left as a residual charge in the detector 10. When an electrostatic latent image is recorded on the image detector 10, a high voltage is applied to the image detector 10 before the irradiation of the recording light. Charge) is also accumulated in the image detector 10.
It is also known that various charges are accumulated in the image detector 10 before the irradiation of the recording light due to other causes. Unnecessary charges such as residual charges and dark current charges accumulated before the irradiation of the recording light are added to the charges carrying image information accumulated by irradiating the recording light. A signal output when the electrostatic latent image is read from the detector 10 includes a signal component due to unnecessary charges in addition to a signal based on charges carrying image information, and causes a residual image phenomenon and S / N deterioration. Cause problems.

In the "pre-exposure", this recording light is applied to the image detector 1
The purpose is to erase unnecessary charges accumulated in the image detector 10 before irradiating 0, and to solve problems such as an afterimage phenomenon and S / N deterioration.

FIG. 3 shows the image detector 1 of the image pickup unit 4 shown in FIG.
2A and 2B are diagrams showing more specifically the mounting portions of the base plate 6 and the base 5 supporting the same to the housing 2, wherein (A) is a front view seen from the image detector 10, (B), (C) ) Shows a cross-sectional view taken along the line BB and a line CC of (A), respectively. The base 6 supports the glass substrate 5 on which the image detector 10 is formed as shown in the figure. In general, the glass substrate 5 is very thin, having a thickness of 1.1 mm or less, whereas the base 6 is made of glass which is sufficiently thick so as not to bend even if it is arranged vertically as shown in FIG. Is 5 mm or more. The base 6 has transparency to light output from the reading light source and the pre-exposure light source, and has substantially the same refractive index and thermal expansion coefficient as those of the glass substrate 5. Further, in order to prevent light loss and stray light due to the reflection of the reading light, the reading light incident surface side 6 is used.
a is provided with an AR (anti-reflection) coat. The base 6 and the substrate 5 are bonded with an adhesive such as epoxy resin or Canadian balsam. As shown in FIG. 3, the base 6 is reinforced and fixed to the housing 2 at four corners, left, right and lower ends thereof by mounting members 7 made of metal or the like. In addition, between the upper end of the base 6 and the mounting member 7, the above-mentioned T for connecting the image detector 10 and the printed circuit board 31 is provided.
A gap 8 through which the AB film 32 passes is provided. More specifically, as shown in the sectional view (B), the image detector 1 of the base 6 is
A gap 8 is provided between the portion located above
The upper right corner of the base 6 shown in FIG. (A) is sandwiched by mounting members 7 as shown in a sectional view (C).

FIG. 4 shows the image detector 10, the current detecting means 3
FIG. 2 is a diagram showing details of connection states of a high voltage power supply unit 45 and 0. As shown in the figure, each element 15a of the image detector 10 is connected to a charge amplifier IC 33 via a print pattern (not shown) formed on a TAB film 32.
And a charge amplifier IC 33 formed on the TAB film 32 and a print pattern (not shown)
Is connected to the printed circuit board 31 via the. In this embodiment, instead of connecting all the elements 15a to one charge amplifier IC 33, several to several tens of charge amplifier ICs 33 are provided as a whole, and each of the charge amplifier ICs 33 is sequentially charged for several adjacent elements 15a. Amplifier I
It is connected to C33.

The first conductive layer 11 which is a plane electrode of the image detector 10 is provided with a non-image area 11a which is partially larger than the image recording area. In the non-image area 11a, the hot side (core wire) of the cable 46 output from the high-voltage power supply unit 45 arranged near the image detector 10
46a is directly bonded, and the ground side (jacket) 46b of the cable 46 is connected to the printed circuit board 31 by a screw 47. In the present embodiment, the hot side 46a is set to a negative potential with respect to the ground side 46b. The ground side 46b connected to the printed board 31
Each charge amplifier IC 33 through the TAB film 32
Connected to the charge amplifier IC 33
Of the reference potential.

As described above, in the device 1 having the above-described structure, the high-voltage power supply unit 45 is disposed near the image detector 10 and the printed circuit board 31, so that the power supply connection cable 46 can be shortened. Since the cable 46 is not required to be routed, the hot side 46a and the ground side 46b of the cable 46 are connected to the image detector 10 and the printed circuit board 31 by direct bonding or screwing. The cost can be reduced without the need.

In this embodiment, the TAB connection is used to connect the image detector 10 to the printed circuit board 31, but the connection may be made by wire bonding or anisotropic conductive rubber.

FIG. 5 shows details of the current detecting means 30 and the high-voltage power supply section 45 provided in the housing 2 and the image detector 10, the current detecting means 30, and the image arranged outside the apparatus 1. FIG. 3 is a block diagram showing a connection mode with a processing device 150 and the like.

The charge amplifier IC 33 provided on the TAB film 32 is connected to each element 1 of the image detector 10.
It comprises a number of charge amplifiers 33a and sample / hold (S / H) 33b connected to each 5a, and a multiplexer 33c for multiplexing signals from each sample / hold 33b. The current flowing out of the image detector 10 is converted into a voltage by each charge amplifier 33a,
The voltage is sampled and held by the sample and hold 33b at a predetermined timing, and the voltages corresponding to the sampled and held elements 15a are sequentially output from the multiplexer 33c so as to be switched in the arrangement order of the elements 15a (corresponding to a part of main scanning). Do). The signals sequentially output from the multiplexer 33c are
The voltage input to the multiplexer 31c provided above and the voltage corresponding to each element 15a is
The data is sequentially output from the multiplexer 31c so as to be switched in the arrangement order of a, and the main scanning is completed. Multiplexer 31
c are sequentially converted into digital signals by an A / D converter 31a, and the digital signals are stored in a memory 31b.
Is stored in

FIG. 6 is a diagram showing details of the high-voltage power supply unit 45 of the first embodiment and the manner of connection between the high-voltage power supply unit 45 and the image detector 10. The high-voltage power supply unit 45 includes a high-voltage power supply 40 that outputs a constant high voltage Vp of 1 kv or more between output terminals, and voltage application control means that controls on / off of voltage application from the high-voltage power supply 40 to the image detector 10. And a rush current suppressing means 48 having resistors R1 and R2 disposed between the high voltage power supply 40 and the bias switching means 42.

The bias switching means 42 of the first embodiment is provided with two-input and one-output switches SW1 and SW2. The output terminal of the switch SW2 is connected to the first conductive layer 11 of the image detector 10, one input terminal a of the switch SW2 is connected to the output terminal of the switch SW1, and the other input terminal b of the switch SW2 is grounded. And a charge amplifier IC by the ground side 46b of the cable 46.
Is also connected to the reference potential of

One input terminal a of the switch SW1 is connected to the hot side (−output side in this embodiment) of the high voltage power supply 40 via the resistor R1 constituting the rush current suppressing means 48, and the other input terminal a of the switch SW1. The input terminal b is connected to the ground side (+ output side in this embodiment) of the high-voltage power supply 40 via the resistor R2 constituting the rush current suppressing means 48 and is grounded.

The switches SW1 and SW2 are desirably switches having sufficiently low on-resistance and extremely high off-resistance, and are suitable as relays. Further, when switching the high voltage, it is necessary to avoid the deterioration of the contacts due to chattering or the destruction of the image detector 10 and the peripheral circuits due to the spike current due to the arc discharge. It is preferred to use a reed relay located, for example, an S-series reed relay from Kilovac.

When relays are used as the switches SW1 and SW2, as shown in FIG. 6B, a drive control circuit 42a for driving and controlling the relays is provided.

The resistance R constituting the inrush current suppressing means 48
As described later, R1 and R2 denote inrush currents generated when the bias is switched by the bias switching means 42, that is, when the application of the voltage to the image detector 10 is started or stopped, and particularly, the peak value (peak value) thereof. (A head value) is limited, and the non-image of the first conductive layer 11 to which the current of the device 1 is concentrated, for example, the printed pattern on the TAB film 32 connected to each element 15a or the core wire 46a of the cable 46 is directly bonded. In order to prevent the destruction of the region 11a and the like, the charging / discharging excessive current is provided.

Next, the high-voltage power supply unit 45 of the first embodiment
The operation of the chest imaging apparatus 1 having the above will be described with reference to a timing chart shown in FIG.

When the image detector 10 is not operating, the switch SW2 of the bias switching means 42 is set to the input terminal b side,
The two electrode layers 11 and 15 are connected to the charge amplifier IC 33 so that no voltage is applied from the high voltage power supply 40 to the image detector 10.
Short-circuit through the imaginary short. The switch SW1 may be in any state, but in this embodiment, it is set to the input terminal b side.

In the state where no voltage is applied to the image detector 10, first, the photographing unit 4 is adjusted to the size of the subject (patient).
Up and down for positioning. Next, the image detector 10 is irradiated with pre-exposure light to erase unnecessary charges accumulated in the image detector 10. The pre-exposure processing may be performed before or after applying a voltage to the image detector 10 described later. Further, a mode may be adopted in which pre-exposure light is irradiated before applying a voltage, and the light is turned off after applying a voltage.

At the time of photographing, first, both switches SW1 and SW2 of the bias switching means 42 are set to the input terminal a side,
The negative electrode (hot side) of the high voltage power supply 40 is connected to the first conductive layer 11 via the resistor R1, and the DC voltage from the high voltage power supply 40 is connected to the first conductive layer 11 via the imaginary short of the charge amplifier IC 33. The voltage is applied between the conductive layer 11 and the element 15a so that the conductive layers 11 and 15 are charged. As a result, a U-shaped electric field is formed between the plate electrode of the first conductive layer 11 of the image detector 10 and the element 15a, with the element 15a having a U-shaped recess.

Here, when both switches SW1 and SW2 of the bias switching means 42 are set to the input terminal a side,
A capacitor Cd (F) formed by the image detector 10 is connected between the high-voltage power supply 40 and the image detector 10 via a resistor R1 to obtain a time constant T.
1 = Charging current I so as to charge at C · R1 (sec)
c flows, and the voltage between the conductive layers 11 and 15 of the image detector 10 (hereinafter referred to as a bias voltage) gradually approaches the inter-terminal voltage Vp of the high-voltage power supply 40 with the time constant T1. Switch SW2
Assuming that a bias voltage applied between the output terminal of the image detector 10 and the first conductive layer 11 of the image detector 10, that is, between each element 15a and the first conductive layer 11, is Vd (V), the charging current Ic becomes Ic = It can be represented by (Vp-Vd) / R1.

When the resistor R1 is directly connected without providing the resistor R1, an extremely large current flows as is apparent from the equation representing the charging current Ic. In particular, immediately after the switches SW1 and SW2 are switched, the bias voltage Vd is 0V. An extremely large inrush current flows, and in some cases, breakage such as disconnection occurs. On the other hand, according to the configuration of the first embodiment of the present invention, the charging current Ic is Ic = Vp even at the peak value immediately after switching.
/ R1 and there is no risk of disconnection or smoking.

When the bias voltage Vd applied to the image detector 10 is V
After reaching p, when the photographer presses an irradiation button (not shown) at an appropriate timing, the grid 70 arranged on the side of the subject of the photographing unit 4 starts swinging, and this grid 7
The X-ray is emitted to the subject at the timing when the swing speed of 0 reaches the predetermined speed and a sufficient voltage is applied to the image detector 10 by the above-described voltage application.

When the image detector 10 is irradiated with X-rays transmitted through the subject, that is, recording light carrying radiation image information of the subject, positive and negative charge pairs are generated in the recording photoconductive layer 12 of the image detector 10. The negative charges therein are concentrated as latent image polar charges on the element 15a along the electric field distribution described above, and the negative charges are stored in the power storage unit 19 formed at the interface between the recording photoconductive layer 12 and the charge transport layer 13. Is accumulated. Since the amount of the accumulated negative charges, that is, the latent image polar charges, is substantially proportional to the amount of radiation transmitted through the subject, the latent image polar charges carry an electrostatic latent image. Thus, the electrostatic latent image is recorded on the image detector 10. On the other hand, the positive charges generated in the recording photoconductive layer 12 are attracted to the first conductive layer 11 and recombine with the negative charges injected from the high-voltage power supply 40 to disappear.

After reading an electrostatic latent image from the image detector 10 after irradiating an X-ray and recording an image, first, at timing t1, the switch S of the bias switching means 42 is switched on.
The switch SW1 is set to the input terminal b while W2 is maintained to the input terminal a, and both conductive layers 11, 15 of the image detector 10 are set.
The electric charges are rearranged via the resistor R2. At the time of this charge rearrangement, the capacitor Cd (F) formed by the image detector 10 is discharged through the resistor R2 at a time constant T2 = C · R2 (sec) in the opposite direction to the charge current Ic. , A bias current Vd of the image detector 10 gradually approaches 0 V with a time constant T2. This discharge current Id is expressed as Id =
Vd / R2.

When the resistor R2 is directly connected without providing the resistor R2, a very large current flows as is apparent from the equation representing the discharge current Id. Particularly, immediately after the switch SW1 is switched, the bias voltage Vd is Vp because the bias voltage Vd is Vp. An inrush current flows, possibly causing disconnection or smoke. On the other hand, according to the configuration of the first embodiment, the discharge current Id is | Id | = Vp / even at the peak value immediately after the switch SW1 is switched.
R2 can be limited, and there is no risk of breakage such as disconnection.

Here, if reading is performed while the resistor R2 is provided, the output response of the charge amplifier IC 33 during reading deteriorates due to the resistor R2, making it difficult to perform high-speed reading. Therefore, at timing t2 when the bias voltage Vd reaches approximately 0 V, the switch SW2 of the bias switching unit 42 is set to the input terminal b while the switch SW1 of the bias switching unit 42 is set to the input terminal b. 15 is a charge amplifier IC33
To be directly connected (short-circuited) through the imaginary short. Even if the switch SW2 is switched at the timing t2, the bias voltage Vd is sufficiently low, so that a large current that causes destruction does not flow.

After setting the switch SW2 to the input terminal b side,
The reading exposure light source unit 20 is operated to emit linear reading light L from the light source, and is moved to the element 15a in the longitudinal direction, that is, in the sub-scanning direction by a linear motor (not shown) to scan the entire surface of the image detector 10. Light source unit 20
The linear reading light L output from the device 15a of the image detector 10 via the base 6 and the glass substrate 5
Is irradiated.

Then, positive and negative charge pairs are generated in the reading photoconductive layer 14, and the positive charge therein is attracted to the negative charge (latent image polarity charge) stored in the power storage unit 19 so that the charge transport layer is attracted. 13, rapidly recombine with the latent image polar charge in the power storage unit 19 and disappear. On the other hand, the negative charges generated in the reading photoconductive layer 14 recombine with the positive charges injected into the second conductive layer 15 and disappear. Thus, the image detector 1
Negative charges accumulated in 0 disappear by charge recombination,
An electric current is generated in the image detector 10 due to the movement of the charges at the time of the charge recombination.

The current is detected in parallel (simultaneously) for each element 15a by the current detection charge amplifier 33a connected to each element 15a. The signal detected by the charge amplifier 33a is sampled and held by the sample and hold 33b, and is sequentially output from the multiplexer 33c so that the voltage corresponding to each of the sampled and held elements 15a is switched in the arrangement order of the elements 15a. The signals are further sequentially output by the multiplexer 31c, A / D converted by the A / D conversion unit 31a, and stored in the memory 31b as digital image signals.

With the scanning exposure of the reading light L, the image detector 10
The current flowing through the inside corresponds to the latent image charge, that is, the electrostatic latent image, and the image signal obtained by detecting this current represents the electrostatic latent image, so that the electrostatic latent image can be read.

At the time of reading, both conductive layers 11 and 15 of the image detector 10 are directly connected (short-circuited) via the imaginary short of the charge amplifier IC 33. Does not adversely affect high-speed reading.

The image signal once stored in the memory 31b is sent to an external image processing device 150 via a signal cable 90, and is subjected to appropriate image processing in the image processing device 150. Fifteen
1 and sent to the server or printer.

Next, a second embodiment of the present invention will be described focusing on differences from the first embodiment. FIG. 8 is a diagram illustrating details of the high-voltage power supply unit 45 according to the second embodiment and a connection state between the high-voltage power supply unit 45 and the image detector 10.
This corresponds to FIG. 6 of the first embodiment.

The high-voltage power supply unit 45 includes a voltage amplification type high-voltage power supply 40 that outputs a high voltage Vp of 1 kv or more according to the magnitude of the input control signal CTL. Switching means 42 as voltage application control means for turning on and off voltage application to the power supply, one resistor R3 disposed between the high voltage power supply 40 and the bias switching means 42, and a control signal for outputting the control signal CTL. Inrush current suppressing means 48 having a generating circuit 49 is provided.

The bias switching means 42 of the second embodiment is provided with a two-input one-output switch SW3.
An output terminal of the switch SW3 is connected to the first conductive layer 11 of the image detector 10, and one input terminal a of the switch SW3.
Is connected to the hot side (−output side in this embodiment) of the high voltage power supply 40 via the resistor R3 constituting the rush current suppressing means 48, and the other input terminal b of the switch SW3 is connected to the ground side of the high voltage power supply 40. (+ Output side in this embodiment) and grounded, and also connected to the reference potential of the charge amplifier IC by the ground side 46b of the cable 46. As described above, since the voltage amplification type high voltage power supply 40 is used, the number of switches is one compared to the first embodiment.
We need less. It is preferable to use a relay for the switch SW3 as in the first embodiment.

FIG. 9 is a timing chart for explaining the operation of the chest radiographing apparatus 1 provided with the high-voltage power supply unit 45 of the second embodiment, and corresponds to FIG. 7 of the first embodiment.

When the control signal CTL input from the control signal generation circuit 49 is 0 V, the voltage amplification type high voltage power supply 40 does not output a voltage (inter-terminal voltage = 0 V), and the control signal C
When TL is Vi other than 0 V, it outputs a high voltage corresponding to the magnitude of Vi, and the control signal CTL functions as the switch SW1 of the first embodiment. Note that the switch SW3 is the switch SW3 of the first embodiment.
Functions as 2.

In the second embodiment, the control signal CT
When the voltage is applied to the image detector 10 by the control of L and when the image detector 10 is stopped, the charging current Ic and the discharging current Id flow with the time constant T3 = C · R3 (sec). When the voltage between terminals is Vp (V), Vp
/ R3.

At the time of reading, as in the first embodiment,
Since the switch 3 is set to the input terminal b side so that the conductive layers 11 and 15 of the image detector 10 are directly connected (short-circuited) via the imaginary short of the charge amplifier IC 33, the inrush current limiting resistor R3 operates at high speed. There is no adverse effect on reading.

In each of the above embodiments, the resistor is used as the rush current suppressing means and the circuit configuration is simplified. However, the present invention is not limited to this. In any of the cases where the application is stopped, any type can be used as long as the inrush current can be suppressed to the extent that the image detector, the voltage application control means, and the image signal acquisition means are not destroyed by the inrush current. There may be.

In each of the above embodiments, the present invention is applied to a device for chest imaging, but the present invention is not limited to this, and can be applied to other devices for imaging.

In the above embodiment, the electrostatic recording medium described in Japanese Patent Application No. 10-232824 filed by the present applicant was used as the image detector. Any material having a photoconductor sandwiched between layers may be used.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a schematic configuration of a chest imaging apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of an image detector used in the chest imaging apparatus and a diagram showing an arrangement relationship between a reading exposure light source unit and the image detector;

FIG. 3 is a diagram showing a base supporting the image detector.

FIG. 4 is a diagram showing details of a connection mode of an image detector, a current detection unit, and a high-voltage power supply unit.

FIG. 5 is a block diagram showing details of a current detection unit and a high-voltage power supply unit and a connection mode between the current detection unit and the high-voltage power supply unit and an image detector;

FIG. 6 is a diagram illustrating details of a high-voltage power supply unit according to the first embodiment and a connection state with an image detector.

FIG. 7 is a timing chart illustrating the operation of the device including the high-voltage power supply unit according to the first embodiment.

FIG. 8 is a diagram illustrating details of a high-voltage power supply unit according to a second embodiment and a connection state with an image detector.

FIG. 9 is a timing chart illustrating the operation of the device including the high-voltage power supply unit according to the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 chest imaging device 3 imaging support column 4 imaging unit 10 radiation image detector 11 first conductive layer 12 recording photoconductive layer 13 charge transport layer 14 reading photoconductive layer 15 second conductive layer 15a Element (linear electrode) REFERENCE SIGNS LIST 19 power storage unit 20 exposure light source unit for reading 30 current detection unit 40 high voltage power supply 42 bias switching unit (voltage application control unit) 42 a drive control circuit 45 high voltage power supply unit 48 inrush current suppression unit 60 pre-exposure light source unit R1 resistance R2 resistance

Claims (6)

[Claims] 1. An image detector comprising: a photoconductor that generates electric charges by being irradiated with an electromagnetic wave; and an image detector in which two electrode layers disposed so as to sandwich the photoconductor are two-dimensionally distributed. A power supply, voltage application control means for turning on and off application of a voltage output from the power supply between the two electrode layers, and obtaining an electric signal having a magnitude corresponding to an amount of electric charge generated in the photoconductor. Wherein the power supply outputs a voltage of 1 KV or more, and the rush occurs when the application of the voltage is started and when the application of the voltage is stopped. Current, the image detector by the inrush current,
An image information detecting apparatus, comprising: an inrush current suppressing unit that suppresses at least one of the voltage application control unit and the image signal acquiring unit to a size that does not cause destruction. 2. An inrush current suppressing unit which reduces the inrush current by such an amount that the inrush current does not cause any damage to any of the image detector, the voltage application control unit, and the image signal acquisition unit. An image information detection apparatus characterized in that the image information is detected by the image information detection apparatus. 3. The image information detecting device according to claim 1, wherein said inrush current suppressing means is a resistor disposed between said power supply and said image detector. 4. A recording photoconductive layer for generating a latent image polarity charge by irradiating a recording electromagnetic wave carrying the image information with the image detector, and a storage for storing the latent image polarity charge. The image information detection device according to claim 1, further comprising a reading unit, and a reading photoconductive layer that generates an electric charge by being irradiated with a reading electromagnetic wave. 5. The image information detecting device according to claim 1, wherein said voltage application control means comprises a relay and a drive control means for driving and controlling said relay. 6. The image information detecting device according to claim 5, wherein the contact point of the relay is placed at a pressure lower than the atmospheric pressure.