JP2002278005A - Radiation image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deterioration in the S/N of an output signal in correlative double sampling processing due to variance in delay among output signals of elements in difference line sensors and in one line sensor of a radiation image reader which photoelectrically converts stimulable light emitted by a stimulable phosphor sheet by a detecting means constituted by arraying line sensors in a horizontal scanning direction and performs the correlative double sampling processing for the photoelectrically converted signal to make a read. SOLUTION: A sampling control means 32 divides line sensors into two areas 23 and 24, determines the timing of the correlative double sampling processing by the areas, and controls a sampling means 31 according to the determined timing so that proper correlative double sampling processing is performed by the areas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exciting a radiation image stored in a stimulable phosphor sheet with linear excitation light.
The present invention relates to a radiation image reading apparatus that reads the stimulated emission light by a line sensor.

[0002]

2. Description of the Related Art When a stimulable phosphor is irradiated with radiation, a part of the radiation energy is accumulated, and then, when irradiated with excitation light such as visible light or laser light, the stimulable phosphor is stimulated according to the accumulated radiation energy. Emission light is emitted. Conventionally, using this stimulable phosphor (stimulable phosphor), for example, a stimulable phosphor sheet in which the stimulable phosphor is laminated on a support is irradiated with radiation transmitted through a subject such as a human body. Thus, the radiation image is once accumulated and recorded, the stimulable phosphor sheet is irradiated with excitation light such as laser light to generate stimulated emission light, and the stimulated emission light is photoelectrically converted to generate an image signal. The radiographic image reader to be obtained is CR (Computed Radio)
graphy).

[0003] The image signal obtained by the above system is subjected to image processing such as gradation processing and frequency processing suitable for observation and interpretation, and the image signal after these processing is applied to a diagnostic visible image ( This is recorded on a film as a final image) or displayed on a high-definition CRT and provided for diagnosis by a doctor or the like.

Further, in a radiation image reading apparatus using the above-mentioned stimulable phosphor sheet, from the viewpoints of shortening the reading time of the stimulable emission light, making the apparatus compact and reducing the cost, the sheet is used as an excitation light source. In contrast, a line light source that irradiates the excitation light linearly is used, and the length direction of the linear portion of the sheet irradiated with the excitation light by the line light source (hereinafter, referred to as
A line sensor in which a large number of photoelectric conversion elements are arranged along the main scanning direction), and one of the line light source and the line sensor and the phosphor sheet is relatively positioned with respect to the other. Japanese Patent Application Laid-Open No. S60-11156 proposes a configuration provided with a scanning means for moving in a direction substantially perpendicular to the length direction of the shape portion (hereinafter referred to as a sub-scanning direction).
No. 8, JP-A-60-236354, JP-A-1-101540, etc.).

When the stimulated emission light is photoelectrically converted and read by the line sensor, noise and the like included in the output signal of the line sensor are reduced for each pixel of the photoelectric conversion element of the line sensor for the purpose of reducing noise and the like. A technique called so-called correlated double sampling, which obtains accurate pixel data by taking the difference between the level of the feedthrough component included in the output signal and the level of the search signal component, is widely used.

That is, as shown in FIG. 9, the output signal of the line sensor generally includes a reset pulse component RP corresponding to a period for canceling the accumulated electric charge and an electric charge for each pixel (per cycle). It is composed of a feed-through component FT corresponding to a period in which the light is not accumulated, and a search signal component PS having a level corresponding to the accumulated electric charge according to the intensity of light applied to the light receiving portion of the photoelectric conversion element. ing.
In the following description, the level in the feedthrough component FT is called a feedthrough level, and the level in the pixel signal component PS is called a data level. As described above, the feedthrough level is the level of the output signal of the line sensor in a state where no electric charge is accumulated. Therefore, by subtracting the feedthrough level from the data level, accurate pixel data from which the influence of noise or the like is removed is obtained. Can be obtained. In such correlated double sampling, an output signal of a line sensor, which is an analog signal, is converted into digital data by an A / D converter.
So-called digital correlated double sampling (hereinafter referred to as digital CDS (Corre)) performs correlated double sampling on the output signal of the photoelectric conversion element converted to the digital data.
referred to as “latable double sampling).

In the digital CDS, it is necessary that the accurate feedthrough level and the accurate data level are sampled by the A / D converter.

When the sampling timing of the A / D converter is determined, two sampling points are required during one cycle of the output signal of the line sensor, so that a timing signal of twice the frequency is used. When the line sensor is operated at high speed, the A / D timing signal naturally becomes high speed. A / D timing signal should be fast, A
The restriction (pulse width) of the timing signal input to the / D converter is also strict, and therefore, it is desirable to set the duty ratio of the timing signal of the A / D converter to approximately 50%. Assuming that the duty ratio of the timing signal of the A / D converter is approximately 50%, the sampling timing of the data level is located after the data level from the sampling positional relationship of the feedthrough level of the output signal of the photoelectric conversion probe. Become.

Further, when the photoelectric conversion element is operated at a high speed, the period of the feedthrough component FT is shortened. It is desirable to sample the levels.

For this reason, as a specific example, for example, in an A / D converter that performs sampling at the falling edge of a timing signal (clock signal) for determining the sampling timing in the A / D converter, FIG. It is desirable that the timing relationship shown in FIG.

That is, the falling edge of the timing signal is located substantially at the center of the feedthrough one component FT, and the falling edge of the next pulse is located relatively behind the pixel signal component PS. This is set so that sampling is performed at the falling edge.

Here, when the stimulable phosphor sheet is read by the above-described radiation image reading apparatus, the size of the stimulable phosphor sheet to be read is larger than the length of the line sensor. Is performed in a single scan in the sub-scanning direction, it is necessary to use an array of a plurality of line sensors in the main scanning direction as detecting means.

[0013]

However, at this time, the output signals output from the plurality of line sensors have individual differences due to manufacturing problems. Appropriate sampling timing of the signal in the A / D converter is different. Further, even in a single line sensor, there is a variation in delay of an output signal between photoelectric conversion elements, and accordingly, a suitable sampling timing is similarly different. Therefore, if a common timing signal is used for the correlated double sampling processing for all the line sensors in the detection means, the output signals between the line sensors in the plurality of line sensors and between the photoelectric conversion elements in one line sensor are output. S / N of the output signal to be output is deteriorated due to the variation of the delay of the output signal. In particular, when the photoelectric conversion element is operated at a high speed, this deterioration becomes more remarkable.

In view of the above problems, the present invention photoelectrically converts stimulated emission light emitted from a stimulable phosphor sheet by a detection means having a plurality of line sensors arranged in a main scanning direction, In a radiation image reading apparatus that performs reading by applying a correlated double sampling process to a photoelectrically converted signal, correlated double sampling due to a variation in delay of an output signal between each line sensor and between each photoelectric conversion element in the line sensor, and the like. An object of the present invention is to provide a radiation image reading apparatus capable of reducing deterioration of S / N of an output signal during processing.

[0015]

A first radiation image reading apparatus according to the present invention irradiates a part of the surface of a stimulable phosphor sheet on which a radiation image is accumulated with excitation light linearly in a main scanning direction. Irradiation means and a large number of photoelectric conversion elements that receive stimulated emission light emitted from a portion where excitation light is linearly irradiated by the irradiation means of the phosphor sheet and photoelectrically convert and receive the stimulated emission light are linearly arranged in the main scanning direction. Detecting means in which a plurality of line sensors are arranged in the main scanning direction, sampling means for performing a correlated double sampling process on an analog image signal output from the detecting means to output a digital image signal, irradiation means, and Scanning means for moving one of the detecting means and the phosphor sheet relative to the other in the sub-scanning direction different from the main scanning direction, and moving the digital image signal output from the sampling means In the radiation image reading apparatus having reading means for sequentially reading in accordance with the timing, the timing of the correlated double sampling process is determined for each of the plurality of line sensors, and the correlation is determined for each of the plurality of line sensors based on the determined timing. A sampling control means for controlling the sampling means to perform the double sampling process is provided.

Here, in the sampling means of the present invention,
In order to perform so-called correlated double sampling on the analog image signal output from the detection means, a timing signal for sampling is generated, the analog image signal is sampled according to the timing signal, and the sampling value is determined according to the sampling value. A digital image signal is output.

The analog image signal generated by the detection means is, for example, a signal as shown in FIG. 9, and the output level of the field through component differs greatly from that of the pixel signal component. Therefore, it is possible to specify each field of the field through component and the pixel signal component based on the digital data sampled by each timing signal when the phase of the timing signal is changed. By positioning each sampling timing in the specified area, the levels of the field-through component and the pixel signal component can be sampled with high accuracy.

The above-mentioned "determining the timing of the correlated double sampling process for each of the plurality of line sensors" means, for example, individually determining the timing of the correlated double sampling for each of the plurality of line sensors as described above. Means to do.

According to a second radiation image reading apparatus of the present invention, there is provided irradiation means for irradiating a part of the surface of a stimulable phosphor sheet on which a radiation image is stored with excitation light linearly in a main scanning direction; A line sensor in which a large number of photoelectric conversion elements that receive stimulated emission light emitted from a portion where excitation light is linearly irradiated by irradiation means of a sheet and perform photoelectric conversion are linearly arranged in the main scanning direction. , A sampling means for performing a correlated double sampling process on an analog image signal output from the detection means to output a digital image signal, an irradiation means, a detection means, and a phosphor. Scanning means for moving one of the sheets relative to the other in a sub-scanning direction different from the main scanning direction, and digital image signals output from the sampling means in sequence according to the movement. In the radiation image reading apparatus having a reading means for taking seen, each line sensor at least 2
And sampling control means for controlling the sampling means so as to determine the timing of the correlated double sampling processing for each of the areas and to perform the correlated double sampling processing for each of the areas based on the determined timing. It is characterized by the following.

The above-mentioned “dividing each line sensor into at least two regions and determining the timing of the correlated double sampling process for each region” means that at least two regions are divided for each line sensor of a plurality of line sensors. This means that the timing of correlated double sampling is individually determined for all the divided areas, for example, as described above.

Further, the sampling control means can determine the timing when the radiation image reading apparatus is started.

[0022]

According to the first radiation image reading apparatus of the present invention, the timing of the correlated double sampling processing is determined by the sampling control means for each of the plurality of line sensors, and the determined timing is determined. Since the sampling means is controlled so as to perform the correlated double sampling processing for each of the line sensors based on the plurality of line sensors, it is assumed that there is a variation in the delay of the output signal among the line sensors of the plurality of line sensors. Also, the correlated double sampling process can be performed at an appropriate timing for each line sensor, and the S / N of the output signal can be improved.

According to the second radiation image reading apparatus of the present invention, each line sensor is divided into at least two regions by the sampling control means, and the timing of the correlated double sampling processing is determined for each of the regions. The sampling means is controlled so as to perform the correlated double sampling processing for each area based on the timing. Therefore, even if there is a variation in the delay of the output signal between Correlated double sampling processing can be performed on the region at an appropriate timing, and the S / N of the output signal can be improved.

In the first and second radiographic image reading apparatuses according to the present invention, when the timing of the correlated double sampling is determined when the apparatus is started, the correlated double sampling is periodically performed. Since the timing of the sampling process can be adjusted to an appropriate timing, even if the delay of the output signal varies due to aging, environmental factors, or the like, the deterioration of the S / N of the output signal can be reduced. .

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. 1 is a perspective view showing an embodiment of the radiation image reading apparatus according to the present invention, FIG. 2 is a sectional view showing a cross section taken along line II of the radiation image reading apparatus shown in FIG. 1, and FIGS. FIG. 3 is a diagram showing a detailed configuration of a line sensor 20 of the reader shown in FIG.

The radiation image reading apparatus according to the present invention comprises a scanning belt 40 on which a stimulable phosphor sheet (hereinafter, referred to as a phosphor sheet) 50 on which a radiation image is accumulated and recorded is conveyed in a direction indicated by an arrow Y. An excitation light source 11 that emits the excitation light (hereinafter simply referred to as excitation light) L substantially parallel to the surface of the phosphor sheet 50, a collimator lens that collects the linear excitation light L emitted from the excitation light source 11, and one direction Optical system 1 consisting of a combination of toric lenses that expands the beam only in
2. The excitation light L is disposed so as to be inclined at an angle of 45 degrees with respect to the surface of the phosphor sheet 50, and is set so as to reflect the excitation light L in a substantially vertical direction toward the phosphor sheet 50 and transmit a stimulated emission light M described later. The dichroic mirror 14, the linear excitation light L reflected by the dichroic mirror 14 is condensed on the phosphor sheet 50 into a line extending in the X direction, and the phosphor sheet 50 is irradiated with the excitation light. A refractive index distributed lens array 15 (a lens in which a large number of refractive index distributed lenses are arranged, and a plurality of refractive index distributed lenses are arranged so that the stimulated luminescence light M corresponding to the accumulated and recorded radiation image emitted from the lens is a parallel light flux. Selfoc lens array),
A second luminous flux M, which is converted into a parallel luminous flux by the first selfoc lens array 15 and transmitted through the dichroic mirror 14, is condensed on a line sensor 20, which will be described later.
The excitation light L reflected on the surface of the phosphor sheet 50 slightly mixed with the stimulated emission light M transmitted through the SELFOC lens array 16 and the second SELFOC lens array 16 is cut. Excitation light cut filter 1 to be transmitted
7. Stimulated light M transmitted through the excitation light cut filter 17
Detecting means 20 for receiving and photoelectrically converting the analog image signal, a sampling means 31 for digitizing an analog image signal output from the detecting means 20 by an A / D converter 34, performing correlated double sampling, and outputting a digital image signal, Reading means 30 for sequentially reading digital image signals output from sampling means 31 in accordance with the movement of scanning belt 40
It has.

As the excitation light source 11, the light source itself may emit linear excitation light, or may be a linear one using an optical system.

The selfoc lens array 16 forms an image of the photostimulated light M on the phosphor sheet 50 in a one-to-one size on the light receiving surface of the line sensor.

An optical system 12 composed of a collimator lens and a toric lens is provided with an excitation light L from an excitation light source 11.
On the phosphor sheet 50 to a desired irradiation area.

The detecting means 20 has a plurality of (for example, 1,000 or more) photoelectric conversion elements 21 arranged in the X direction as shown in FIG. 3, and a plurality of line sensors 22 arranged in the X direction. It is.

Further, as shown in FIG. 4, the sampling means 31 outputs the analog image signals output from the line sensors 22 of the detection means 20 into one analog image signal. An amplifier 33 for amplifying the analog image signal; an A / D converter 34 for sampling and digitizing the analog image signal amplified by the amplifier 33 in accordance with a timing signal output from a timing generator 36 described later; The correlated double sampling circuit (hereinafter, referred to as CDS) 35 which performs a correlated double sampling process on the digital pixel data output from the device 34 and outputs it as a digital image signal, and the sampling timing in the A / D converter 34 are described above. Line sensor 2
Sampling control means 3 which determines each of the divided regions 23 and 24 within the area 2 and controls the correlated double sampling processing for each region at each timing.
2 is provided. In the CDS 35, the A / D converter 34
The field data representing the level of the field through component and the pixel data representing the level of the pixel signal component are sampled, and the field through data is subtracted from the pixel data for each pixel. And
The result is output as a digital image signal. The sampling timing of the field data and pixel data in the A / D converter 34 is determined and controlled for each of the regions by the sampling control means 32. The determination of the sampling timing in each region will be described later.

The timing generator 36 divides the frequency of a clock signal from a clock signal generator (not shown) by a frequency divider including a plurality of delay circuits based on a sampling timing set value from a sampling control signal. It generates a timing signal. By switching and operating a plurality of delay circuits of the frequency divider, it is possible to generate various timing signals based on the clock signal.

Next, the operation of the radiation image reading apparatus according to this embodiment will be described. First, the apparatus is started up by turning on a power supply (not shown) of the apparatus. At this time, the sampling control means 32 determines and sets the sampling timing of the field data and pixel data in the A / D converter 34 for each of the regions 23 and 24 of all the line sensors 22.
The operation will be described with reference to the flowchart of FIG. Here, the case where the line sensor 22 of the detecting means 20 operates with a clock signal of 12 MHz and the phase of the timing signal input to the A / D converter 34 can be changed by the timing generator 36 in units of 1 ns. Will be described. When the sampling timing is determined, the fluorescent sheet 50 is not set on the scanning belt 40.

First, in step 10, the A / D converter 3 is closed in a state where light incident on the line sensor 22 of the detecting means 20 is shielded by closing a shutter (not shown).
The analog signal output from 4 is sampled. The sampling control means 32 includes the line sensor 22.
Is the field-through component F when operating at 12 MHz.
T and a first area A1 (see FIG. 6) that includes a reset pulse component RP and a part of the pixel signal component PS that are in contact with both ends of the field through component FT, respectively, and a rear end side of the pixel signal component PS. The sampling timing of each region of the second region A2 including a part thereof and a part of the reset pulse component RP in contact with the rear end of the pixel signal component PS is set in advance. A1 is applied to the area 23 of the line sensor 22 every 1 ns.
The digital signal output from the / D converter is sampled.

FIG. 7A shows an example of the state of digital data obtained by this sampling. In the figure, the horizontal axis represents the sampling timing, and the vertical axis represents the digital data obtained by sampling as the ratio of the output level to the saturation level of the photoelectric conversion element 21 of the line sensor 22. (The same applies to FIGS. 7B, 7C, 7D, 7F, and 7H).

As shown in the figure, in the first area A1, the line sensor 2 is not turned on during the period corresponding to the reset pulse component RP.
The output level of the second region 23 is 0%, but during the period corresponding to the field-through component FT and the pixel signal component PS, the output level is constant low because of the light-shielded state. As described above, the waveform state of the analog image signal output from the area 23 in the light-shielded state can be known from the sampling data obtained by the processing in step 10.

In the next step 12, the blue LED (not shown) emits light and the shutter (not shown) is fully opened, so that a predetermined amount of light is incident on the line sensor 22. The digital signal output from the area 23 of the line sensor 22 is sampled.
Here, the first region A1 and the second region A2
In both cases, sampling is performed on the region 23 every 1 nS in the same manner as in step 10 described above. In the present embodiment, a blue LED is used as a light source, but any light source may be used as long as it can emit a constant amount of light. Furthermore, the range of irradiation with one light emission is at least the region 23.
May be included, and the entire line sensor 22 may be set as the irradiation range, or the entire detection unit 20 may be set as the irradiation range. However, it is necessary to finally provide a configuration capable of irradiating the entire detection means 20.

FIGS. 7B and 7C respectively show an example of the state of the digital signal in the first area A1 and the second area A2 obtained as a result of the sampling in step 12.

As shown in FIG. 7B, in the first area A1, up to the area corresponding to the field-through component FT, the state is substantially the same as that shown in FIG. In the area corresponding to PS, the magnitude of the digital signal in the area 23 has increased to a level close to 100%.

On the other hand, as shown in FIG. 7C, in the second area A2, in the area corresponding to the pixel signal component PS, the area 2
Although the magnitude of the digital signal of No. 3 is at a level close to 100%, the magnitude of the digital signal drops to near 0% in a region corresponding to the next reset pulse component RP. As described above, the waveform state of the analog image signal output from the area 23 of the line sensor 22 in the illumination state can be known from the sampling data obtained by the processing in step 12.

In the next step 14, the above step 10
In addition, the magnitude of the digital signal of the area 23 in the light-shielded state in the first area A1 sampled in step 12 (see FIG. 7A) and the magnitude of the digital signal of the area 23 in the illumination state (see FIG. 7B ) Is assumed, and areas corresponding to the feedthrough component FT and the pixel signal component PS are assumed.

That is, as shown in FIG. 7 (D), an area where the amount of change (difference) in the magnitude of each sampled digital signal in each of the light-shielded state and the illumination state is equal to or smaller than a predetermined amount is fed. A candidate area for the through component FT (expressed as a “feedthrough temporary area” in the figure)
A region where the variation is larger than the predetermined amount is defined as a pixel signal component PS.
(In the figure, referred to as a “temporary data area”).

In the next step 16, the above step 12
Area A in the illumination state sampled at
1 (see FIG. 7B), the amount of change in the magnitude of the digital signal (corresponding to the gradient of the digital signal waveform in the region 23) is calculated, and the feedthrough component FT is calculated based on the gradient. Is determined.

FIG. 7E shows the calculation result of the slope of the digital signal output from the area 23 of the line sensor 22 shown in FIG. 7B. In FIG. 7, the horizontal axis indicates the sampling timing, and the vertical axis indicates the inclination direction (+ direction and one direction) with reference to the time when the inclination is 0 (zero) (FIG. 7 (G)). The same).

At the time of illumination, as shown in FIG. 7, the level is substantially constant in the area of the field through component FT, and the level is larger than the levels of the other components (the reset pulse component RP and the pixel signal component PS). It is different.
Therefore, in FIG. 7E, after the positions P1, P2, and P3 whose inclinations change in one direction from 0 (zero) are extracted as candidates for both end positions of the castle of the feedthrough component FT, the positions P1 to P3 are extracted. Of these, positions included in the field-through candidate area determined in step 14 (in this case, the delays P1 and P2) are determined as both end positions of the area of the feedthrough component FT.

Thus, as shown in FIG. 7 (F), the area of the feedthrough component FT with respect to the area 23 (expressed as “feedthrough area” in FIG. 7) is determined.

In the next step 18, the above step 10
It is determined whether or not the processing from step 16 to step 16 has been completed for each area of all the line sensors. If the processing has not been completed, the process returns to step 10 and the processing from step 10 to step 16 for the remaining line sensor areas. Are repeated, and the process proceeds to step 20.

In step 20, the area of the feedthrough component FT is determined for each area of the line sensor of the detection means 20, and the center position of the area of the field through component FT is set as the sampling timing set value of the field through level FL. Sampling control means 3
2 in a RAM (not shown).

In the next step 22, the line sensor 22
For the region 23, the amount of change in the sampled digital signal (the waveform of the digital signal in the region 23) is determined using the output level of the second region A2 in the illumination state sampled in step 12 (see FIG. 7C). (Corresponding to the slope), and the sampling timing set value of the data level DL is provisionally determined based on the slope.

FIG. 7 (G) shows the calculation of the inclination of the digital signal in the area 23 of the line sensor 22 shown in FIG. 7 (C).

At the time of illumination, as shown in FIG. 9, the level is substantially constant in the area of the pixel signal component PS, and the level is largely different from the level of the reset pulse component RP. Therefore, in FIG.
The position P4 that changes in the ten directions from (zero) is the pixel signal component P
It is determined as the rear end position of the area S, and is temporarily determined as the sampling timing set value of the data level DL.

Then, in the next step 24, it is determined whether or not the processing in the step 22 has been completed for all the line sensor areas of the detection means 20, and if not completed, the flow returns to the step 22. After the process of step 22 is repeatedly executed for the remaining line sensor area, the process proceeds to step 26. If the provisional setting has been completed for all the regions, the process proceeds to step 26, and the time at which the line sensor 22 is moved back a predetermined time (4 nS in this embodiment) from the position P4 provisionally set for each region in step 24. 23 is determined as a sampling timing set value of the data level DL, and the set value is stored in a RAM (not shown) of the sampling control means 32.

Therefore, in the next step 28, the feedthrough level F for each region obtained by the above processing is obtained.
It is determined whether the determination of the set value of the sampling timing of L and the set value of the sampling timing of the data level DL has been completed for each area of all the line sensors in the detection means 20, and if not completed, the process returns to step 10. The same processing as described above is repeated for a line sensor for which each sampling timing value of each area has not been determined. When the determination of each sampling timing value is completed for each area of all the line sensors, the process proceeds to step 30.

In the next step 30, an engineering check is performed for each sampling timing set value of the feedthrough level FL and the data level DL determined by the above processing. That is, it is determined whether or not each determined sampling timing set value satisfies the input condition of the A / D converter 34. If not, a message indicating an error is displayed on the display. In this way, the process is terminated after the occurrence of the error is clearly indicated to the operator. On the other hand, if the input condition is satisfied, the process ends without specifying the occurrence of the error.

The sampling timing set value of each of the field through level FL and the data level DL determined by the above processing is determined by the timing generator 36.
In the timing generator 36, the falling edge of the timing signal input to the A / D converter 34 based on the input value corresponds to the sampling timing set value of the feedthrough level FL, and The timing signal is generated such that the falling edge corresponds to the sampling timing set value of the data level DL.

Next, the operation of the present apparatus for reading the phosphor sheet based on the correlation double sampling timing determined as described above will be described.

First, by moving the scanning belt 40 in the direction of arrow Y, the scanning belt 40 is placed on the scanning belt 40.
The phosphor sheet 50 on which the radiation image has been stored is indicated by an arrow Y.
Transport in the direction. At this time, the conveying speed of the phosphor sheet is equal to the moving speed of the belt 40, and the moving speed of the belt 40 is input to the reading means 30.

On the other hand, the excitation light source 11 generates the linear excitation light L
Is emitted substantially parallel to the surface of the phosphor sheet 50, the excitation light L is converted into a parallel beam by an optical system 12 including a collimator lens and a toric lens provided on the optical path, and the fluorescent light is emitted by a dichroic mirror 14. The light is reflected in the orthogonal direction perpendicular to the body sheet 50, and the reflected light is linearly extended along the X direction on the phosphor sheet 50 disposed on the phosphor sheet 50 by the first Selfoc lens 15. Is incident substantially perpendicularly.

The stimulable phosphor in the light condensing area is excited by the linear excitation light L incident on the phosphor sheet 50, and the light is incident from the light condensing area into the inside of the phosphor sheet 50 to be in the vicinity of the light condensing area. It diffuses and excites the stimulable phosphor in the vicinity of the light collection area. As a result, stimulated emission light M having an intensity corresponding to the stored and recorded radiation image is emitted from the light-collecting region of the phosphor sheet 50 and its vicinity. This stimulated emission light M is
It is made into a parallel light beam by the first Selfoc lens 15,
The light passes through the dichroic mirror 14 and is condensed by the second selfoc lens array 16 on the photoelectric conversion element 21 of the line sensor 22 of the detection means 20. At this time, the second
Even if the excitation light L reflected on the surface of the phosphor sheet 50 slightly exists in the stimulated emission light M transmitted through the SELFOC lens array 16, the excitation light L is cut by the excitation light cut filter 17. Does not enter.

The stimulated emission light M incident on the photoelectric conversion element 21 is photoelectrically converted and output from the detection means 20 as an analog image signal, and is input to the sampling means 31. In the sampling means 31, the amplifier 33
The analog image signal input at is amplified and input to the A / D converter. The analog image signal input to the A / D converter 34 is sampled based on the timing signal output from the timing generator 36,
It is output as a digital image signal. At this time, the timing generator 36 outputs a timing signal based on the sampling timing set value of the field through level and the data level set in the sampling control means 32 for each line sensor area as described above.
The digital signal output from the A / D converter 34 is a CDS
The CDS 35 subtracts the field-through data at the field-through level from the pixel data at the data level sampled by the A / D converter 34. Then, the result is output as a digital image signal. The digital image signal output from the sampling means 31 is sent to the scanning belt 4 by the reading means 30.
The image is sequentially read in accordance with the movement of the phosphor sheet 50 by 0, and is output to the subsequent image processing apparatus.

According to the radiation image reading apparatus of the present invention, each line sensor is divided into at least two regions by the sampling control means 32, and the timing of the correlated double sampling processing is determined for each region. The sampling means 31 is controlled so as to perform the correlated double sampling processing for each area based on the above. Can be subjected to the correlated double sampling processing at an appropriate timing, and the S / N of the output signal can be improved.

If the timing of the correlated double sampling is determined at the start-up of the apparatus, the timing of the correlated double sampling can be periodically adjusted to an appropriate timing. Even if the delay of the output signal varies due to a temporal or environmental cause, it is possible to reduce the deterioration of the S / N of the output signal.

In the above embodiment, the detecting means 20
The analog signal from the line sensor 22 is collectively input to the A / D converter 34 by the multiplexer 37, so that the A / D converter 34 is reduced to reduce the cost. However, as shown in FIG. The A / D converter 34 may be provided for each of the line sensors 22 of the detection means 20. Also in this case, similarly to the above embodiment, a timing signal based on a sampling timing set value set for each area of each line sensor is input to the A / D converter 34. With the configuration shown in FIG. 8, the occurrence of noise due to the use of the multiplexer 37 can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a radiation image reading apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing a cross section taken along line II of the radiation image reading apparatus shown in FIG. 1;

FIG. 3 is a diagram showing details of a line sensor of the radiation image reading apparatus shown in FIGS. 1 and 2;

FIG. 4 is a diagram showing details of a sampling unit of the radiation image reading apparatus shown in FIGS. 1 and 2;

FIG. 5 is a flowchart showing an operation of determining a sampling timing signal of correlated double sampling in the radiation image reading apparatus according to the present invention.

FIG. 6 is a diagram showing states of an output signal and a sampling timing signal output from a detection unit of the radiation image reading apparatus shown in FIGS. 1 and 2;

FIG. 7A shows a sampling result of the first area in the light-shielded state, FIG. 7B shows a sampling result of the first area in the illumination state, FIG. 7C shows a sampling result of the second area in the illumination state, and FIG. D) shows the temporary field-through area and the data temporary area, (E) shows the calculation result of the inclination in (B), (F) shows the area of the determined field-through component, and (G) shows the inclination in (C). The calculation result of
(H) is a graph each showing the determination result of the sampling timing of the data level.

FIG. 8 is a schematic configuration diagram of a sampling unit of another embodiment of the radiation image reading apparatus according to the present invention.

FIG. 9 is a diagram illustrating an example of a state of an analog signal output from each area of the line sensor and a relationship between the analog signal and an A / D conversion timing signal;

[Explanation of symbols]

Reference Signs List 11 excitation light source 12 optical system including collimator lens and toric lens 16 self-fox lens array 17 excitation light cut filter 20 detecting means 21 photoelectric conversion element 22 line sensor 23, 24 area 30 reading means 31 sampling means 32 sampling control means 33 amplifier 34 A / D converter 35 CDS 36 Timing generator 37 Multiplexer 40 Scanning belt 50 Storage phosphor sheet L Excitation light M Stimulated emission light

Claims (3)

[Claims] 1. An irradiating means for irradiating a part of the surface of a stimulable phosphor sheet on which a radiation image is stored with excitation light linearly in a main scanning direction, and said stimulating light by said irradiating means of said phosphor sheet. A plurality of line sensors, in which a large number of photoelectric conversion elements that receive stimulated emission light emitted from a portion irradiated linearly and perform photoelectric conversion, are linearly arranged in the main scanning direction, are provided in the main scanning direction. Detection means arranged in sequence, sampling means for performing a correlated double sampling process on an analog image signal output from the detection means and outputting a digital image signal; and a means for irradiating means, the detection means and the phosphor sheet Scanning means for moving one relative to the other in a sub-scanning direction different from the main scanning direction; and the digital image signal output from the sampling means for the movement. A reading means for sequentially reading the plurality of line sensors, wherein a timing of the correlated double sampling processing is determined for each of the plurality of line sensors, and the plurality of line sensors are determined based on the determined timing. A radiation image reading apparatus comprising: a sampling control unit that controls the sampling unit so as to perform the correlated double sampling process every time. 2. Irradiation means for irradiating a part of the surface of a stimulable phosphor sheet on which a radiation image is accumulated with excitation light linearly in a main scanning direction, and said excitation light by said irradiation means of said phosphor sheet. A plurality of line sensors, in which a large number of photoelectric conversion elements that receive stimulated emission light emitted from a portion irradiated linearly and perform photoelectric conversion, are linearly arranged in the main scanning direction, are provided in the main scanning direction. Detection means arranged in sequence, sampling means for performing a correlated double sampling process on an analog image signal output from the detection means and outputting a digital image signal; and a means for irradiating means, the detection means and the phosphor sheet Scanning means for moving one relative to the other in a sub-scanning direction different from the main scanning direction; and the digital image signal output from the sampling means for the movement. A radiation image reading apparatus comprising: a reading unit that sequentially reads the line sensors in the same manner; divides each line sensor into at least two regions; determines a timing of the correlated double sampling processing for each of the regions; A radiation image reading apparatus, comprising: a sampling control unit that controls the sampling unit so as to perform the correlated double sampling process for each of the regions based on the area. 3. The radiation image reading apparatus according to claim 1, wherein the sampling control means determines the timing when the radiation image reading apparatus starts up.