JPH1165005A - Radiation image information reading method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce stimulated luminescent aftergrow caused by stimulated luminescent light emitted from an element void. SOLUTION: Read sensitivity is set by adjusting high voltage HV of a photoelectric converter 20 by a sensitivity setting means 30 on the basis of the image information obtained through a pre-reading means 50 so that the quantity of light of a stimulated luminescent light B emitted from an element omission part of the radiation image information may become more than the quantity of light corresponding to the least upper bound of an image recordable range of the photoelectric converter means 20. In normal reading, radiation energy of an outgoing laser light A from a laser beam source 11 on a sheet 1 is controlled by modulating intensity of the laser beam A by an acoustic optical light modulator 46 arranged on an optical path so that a signal level that has read the stimulated luminescent light B emitted from the element omission part may become smaller within the range wider than the least upper bound of the reading signal range of the photoelectric converter means 20 as monitoring an output signal V1 of the photoelectric converter means 20 through a monitor circuit 42.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for reading a radiation image using a stimulable phosphor used for medical diagnosis and the like.

[0002]

2. Description of the Related Art A stimulable fluorescent recording medium (e.g., a stimulable phosphor sheet or the like, in which radiation image information is stored and recorded.
It is simply referred to as “recording medium”. ) Is irradiated with excitation light such as X-rays, and a stimulating luminescent light that emits stimulating light in accordance with the radiation image information stored and recorded in the recording medium is detected to read the radiation image information. A type of radiation image information reading apparatus is known (Japanese Patent Application Laid-Open No. 62-18536, etc.).

In such a radiation image information reading apparatus, as a specific method of reading radiation image information from a recording medium in which radiation image information is stored and recorded, for example, a two-dimensional light beam such as a laser beam is used on a recording medium. There is a method in which an image signal is obtained by scanning in a time series and reading out the stimulated emission light generated at that time in a time series by a photoelectric conversion means such as a photomultiplier.

By the way, the recording medium has the property of emitting radiation energy accumulated in the phosphor as stimulating light when irradiated with excitation light, and the stimulating light rapidly (from the start of irradiation with excitation light). Nearly the highest emission intensity is reached (after several ns, for example), after which the emission intensity decreases slowly,
It has such a property that light emission continues as a so-called afterglow for a response time peculiar to the phosphor even after the excitation light irradiation is completed (such afterglow is referred to as stimulated emission afterglow). Therefore, when the recording medium is scanned with the excitation light and the stimulated emission light emitted in a time series is photoelectrically read, not only the emission component from the pixel being irradiated with the excitation light but also the irradiation of the excitation light has already been completed. Since the afterglow component from the pixel is read as the radiation image information component of the pixel being irradiated, the signal between the pixels is not completely separated, and the sharpness of the obtained image is reduced. Therefore, when a phosphor having a long stimulus afterglow for excitation is used, the sharpness of the image is reduced, and a radiation image having sufficiently high practically satisfactory sharpness cannot be obtained.

[0005] Such a phenomenon occurs in proportion to the irradiation amount (irradiation energy) of the excitation light per unit area on the recording medium, in other words, the light emission amount of the stimulated emission light. If there is a low light emission portion following the high light emission portion of the stimulated emission light, the afterglow component from the high light emission pixel becomes the original signal component as the signal component of the low light emission pixel. And is read superimposed on. For this reason, when a portion having a low light emission amount is read after a portion having a high light emission amount, a signal difference between the low light emission amount portions becomes small, and the image is observed as a relatively reduced contrast image. That is, it also causes the S / N of the image signal to deteriorate.

As a method of solving the above-described problem of the stimulated emission afterglow, for example, recording is performed by adding a differential value of a signal to a time-series signal in pixel units obtained by scanning with excitation light. There has been proposed a method of electrically correcting interference between signals in pixel units due to response characteristics (for example, attenuation characteristics) of stimulated emission light of a medium (see Japanese Patent Publication No. 2-15154).

[0007]

However, in the method proposed in Japanese Patent Publication No. 2-15154, interference between signals in pixel units is calculated by numerical calculation in consideration of the response characteristics of stimulated emission light. There is a problem that correction is required and a large amount of calculation is required.In addition, although the reduction of the sharpness and the reduction of the contrast of the radiographic image can be eliminated, the afterglow component is merely removed by the calculation, and the image is removed. The signal is S
However, the problem of deterioration of / N cannot be solved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-described problem of photostimulated afterglow by a simple method including the problem of S / N degradation. It is an object of the present invention to provide a radiation image information reading method and apparatus capable of reading at high speed and with high accuracy even if the scanning speed is increased.

[0009]

According to the radiation image information reading method of the present invention, a stimulable fluorescent recording medium on which radiation image information of a subject is stored is irradiated with excitation light, and stimulated emission from the recording medium is performed. A radiation image information reading method of reading image information of the subject by emitting light and reading the stimulated emission light emitted from the recording medium by a photoelectric conversion unit, wherein the radiation image information is stored and recorded on the recording medium. The reading sensitivity of the photoelectric conversion unit is adjusted so that the amount of the stimulating emission light emitted from the radiographic image information through the transparent portion is greater than the amount of light corresponding to the upper limit of the image recording area of the photoelectric conversion unit. The signal level obtained by setting and reading the stimulated emission light emitted from the transparent portion by the photoelectric conversion means is small within a range larger than the upper limit of the read signal area of the photoelectric conversion means. In so that, it is characterized in that for controlling the irradiation energy of the excitation light.

[0010] Here, the term "absence portion" refers to a portion directly irradiated on the recording medium without radiation penetrating the subject during recording. Also, "image recording available area"
The term "a" means a range of a desired amount of stimulated emission light emitted from the recording medium to which the photoelectric conversion means can output as a signal.

The expression "controlling the irradiation energy of the excitation light" means controlling the effective energy of the excitation light received per unit area by the recording medium. A method of attenuating the excitation light radiated from the light source in the optical path by an AOM (acoustic optical modulator), a method of controlling the amount of light by controlling an input voltage in the case of a semiconductor laser or the like, or a method of controlling the scanning speed of the laser light. There is a method of speeding up.

In the radiation image information reading method according to the present invention, prior to reading the image information of the subject, pre-reading of the stimulating light emitted from the recording medium is performed, and the image obtained by the pre-reading is read. It is desirable to set the reading sensitivity based on information.

Here, "pre-reading" is to grasp the outline of the image information previously stored and recorded on the recording medium prior to the so-called main reading for reading the image information from the recording medium. This means that the recording medium is irradiated (eg, scanned) with excitation light of a lower level than the excitation light at the time of (1), and the stimulated emission light emitted from the recording medium by this irradiation is read. This "look-ahead" is a well-known technique in this technical field, and is described in many gazettes (for example, JP-A-58-67241, JP-A-58-67243,
In the method for reading radiation image information according to the present invention, a plurality of sensitivity levels of the reading sensitivity are registered in advance in correspondence with a plurality of different photographing menus of the subject. Alternatively, among the plurality of registered sensitivity levels, the sensitivity level corresponding to the imaging menu of the radiation image information to be read may be set as the reading sensitivity.

Here, the "imaging menu" means an imaging region and an imaging method, and includes, for example, chest imaging, head imaging, angiography imaging, and the like.

[0015] On the other hand, the radiation image information reading apparatus according to the present invention is characterized in that the stimulable fluorescent recording medium on which the radiation image information of the subject is stored is irradiated with excitation light to cause the recording medium to emit stimulated emission light. What is claimed is: 1. A radiation image information reading apparatus comprising: a light irradiating unit; and a photoelectric conversion unit configured to read the stimulated emission light emitted from the recording medium, wherein the radiation image information stored and recorded on the recording medium is transparent. A sensitivity setting unit that sets the reading sensitivity of the photoelectric conversion unit so that the amount of the stimulating emission light emitted from the unit is larger than the amount of light corresponding to the upper limit of an image recordable area of the photoelectric conversion unit; The excitation is performed such that the signal level obtained by reading the stimulated emission light emitted from the transparent portion by the photoelectric conversion unit is reduced within a range larger than the upper limit of the read signal area of the photoelectric conversion unit. Is characterized in that a radiation energy control means for controlling the irradiation energy of the light.

In the radiation image information reading apparatus according to the present invention, prior to reading the image information of the subject, there is provided a pre-reading means for pre-reading stimulated emission light emitted from the recording medium, It is preferable that the means sets the reading sensitivity based on the image information obtained by the pre-reading.

In the radiation image information reading apparatus according to the present invention, there is provided a registration means for preliminarily registering a plurality of reading sensitivity levels in correspondence with a plurality of different photographing menus of the subject, The sensitivity setting means may set, as the reading sensitivity, the sensitivity level corresponding to the radiographic image information read menu selected from a plurality of registered sensitivity levels.

[0018]

According to the radiation image information reading method and apparatus according to the present invention, the amount of stimulated emission light emitted from the radiation image information through-hole is limited to the upper limit of the image recording area of the photoelectric conversion means. The reading sensitivity of the photoelectric conversion means is set so as to be larger than the corresponding light amount, and the signal level at which the photostimulated light emitted from the through-hole is detected by the photoelectric conversion means is in the read signal range of the photoelectric conversion means. Since the irradiation energy of the excitation light is controlled so as to be smaller within the range larger than the upper limit and to be at a normal level except for the non-exposed portion, the stimulated emission light emitted from other than the non-exposed portion is used. While maintaining the normal level, the afterglow component due to the stimulating light emitted from the through hole can be reduced, and
Since the afterglow component itself is reduced, noise due to the afterglow component can be reduced, and the S / S of the read signal can be reduced.
It is also possible to improve N. In addition, since excitation light at a normal level can be used for portions other than the light-extracted portion, image information of the subject portion required for diagnosis can be obtained with appropriate quality.

Further, if the pre-reading is performed prior to the main reading and the reading sensitivity is set, the reading conditions can be set more easily. In addition, the reading sensitivity can be automatically set according to the shooting menu, so that the reading conditions can be easily set.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of a method and apparatus for reading radiographic image information according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a radiation image information reading apparatus according to the present invention. The radiation image information reading apparatus according to the present configuration includes an excitation light irradiating unit 10 for scanning and irradiating the sheet 1 with excitation light (laser light A), and stimulating light emission B emitted from the sheet 1 upon receiving the laser light A. A photoelectric conversion unit 20 that photoelectrically converts the read image into an electric signal (image signal), a signal processing unit 30 that performs predetermined image signal processing on the image signal V0 read by the photoelectric conversion unit 20, and a reading sensitivity of the photoelectric conversion unit 20. A sensitivity setting means 30 to be set, an irradiation energy control means 40 for controlling an irradiation amount (irradiation energy) of the laser beam A to the sheet 1 per unit area (irradiation energy), a pre-reading means 50, and the sheet 1 are placed, and an arrow X0 , X1, as shown in FIG.
It is composed of

The excitation light irradiating means 10 includes a laser light source 11 composed of an SHG laser of a semiconductor excitation solid-state laser for emitting a laser light A of a predetermined wavelength, a rotary polygon mirror 12 for reflecting and deflecting the emitted laser light A, A motor 13 for rotating and driving the polygon mirror 12, an fθ lens 14 for condensing the laser beam A, and a reflection optical system 15 for changing the direction by reflecting the condensed laser beam A
And an excitation light irradiation means.

The photoelectric conversion means 20 is a light guide for condensing stimulated emission light B which emits at a light amount corresponding to the radiation image information stored and recorded on the sheet 1 by irradiation of the laser light A.
22, a photomultiplier 24 for amplifying the collected stimulated emission light B and performing photoelectric conversion.

The signal processing means 30 includes a logarithmic amplifier 32, an A / D
The sheet 1 includes a conversion circuit 33 and an image signal processing circuit 34.
The radiation image information stored and recorded on the
And after a predetermined signal processing is performed in the signal processing means 30, it is displayed as a visible image on a display device (not shown) or stored as digital data in a storage device (not shown). Provided for later processing.

The irradiation energy control means 40 includes a logarithmic amplifier 32
Monitor circuit 42 for monitoring the output signal V1 of the excitation circuit control circuit
44, an AOM (acousto-optic light modulator) 46 for modulating the intensity of the laser light A emitted from the laser light source 11.

Next, the operation of the radiation image information reading apparatus according to this embodiment will be described. The sheet 1 on which the radiation image information is stored and recorded by a radiation image information recording device or the like (not shown) is placed on the conveying means 60 and conveyed in the direction of the arrow X0 in the figure, and comprises an excitation light irradiating means 10 and a photoelectric converting means 20. It is carried into the reading unit. In the reading unit, the laser light A emitted from the laser light source 11 passes through an AOM 46 arranged on the optical path, and is rotated by a motor 13 at a high speed.
Is deflected in a predetermined direction, and the deflected laser light A is condensed by the fθ lens 14 and further reflected by the reflection optical system 15.
Irradiates the sheet 1 after being reflected. At this time, the rotation of the rotary polygon mirror 12 in the direction of the arrow K causes the laser beam A to main-scan the sheet 1 in the direction of the arrow Y. Scanning) is combined with the laser beam A uniformly.

From the surface of the sheet 1 irradiated with the laser light A, stimulated emission light B according to the stored and recorded radiation image information is emitted, and the stimulated emission light B is arranged on the upper surface of the sheet 1. Is condensed by the light guide 22
, The image signal V0 carrying the image information recorded on the sheet 1 is read.

Next, a method for determining the reading conditions of the radiation image information reading apparatus will be described. Note that the reading condition is defined as the stimulating light B read by the photoelectric conversion unit 20.
The maximum stimulating light emission amount S1 and the minimum stimulating light emission amount S2 of the image information range are displayed in a proper density range as a visible image, respectively, so that the maximum signal level Q1 and the minimum signal level Various conditions that affect the relationship between the amount of photostimulated luminescence light B in reading and the output of the radiation image information reading device so as to correspond to the signal level Q2, for example, reading sensitivity and scale factor that determine the relationship between input and output Or irradiation energy of excitation light in reading.

In this configuration example, prior to the normal reading of the image information (final reading), the sheet 1 is irradiated with the laser beam A having a lower energy than the laser beam A used in the main reading, and the pre-reading for reading the radiation image information is performed. Then, based on the image information obtained by the pre-reading, the following analysis is performed to determine the reading conditions in the main reading. Hereinafter, this method will be described.

Excitation light irradiating means and transport means for pre-reading are not specially provided in the present configuration example, and are substantially identical to those for main reading except that the irradiation energy of the laser beam A is reduced as described below. This pre-reading is performed by performing substantially the same reading. First, the intensity of the laser light A emitted from the laser light source 11 by the AOM 46 is modulated, so that the irradiation intensity of the laser light A to the sheet 1 is reduced.
The irradiation energy per unit area for irradiating the sheet 1 of the laser beam A is attenuated as compared with the case of the main reading. In such a state, the sheet 1 is scanned with the laser beam as described above,
The stimulated emission light B emitted thereby is read by the photoelectric conversion means 20, and the image signal V0 obtained by this pre-read is logarithmized by the logarithmic amplifier circuit 32. Logarithmic image signal
V1 is an image signal V2 digitized by the A / D converter 33
The image signal V2 is sent to the pre-reading means 50. It should be noted that it is possible to adopt a configuration in which excitation light irradiation means for pre-reading and transport means pre-reading means are provided separately and separately from those for main reading, without using the same means for pre-reading as in this configuration example. Of course, it is possible (see, for example, JP-A-4-1745). Further, as a method of attenuating the irradiation energy per unit area of the sheet 1 irradiated with the laser beam A as compared with the case of the main reading, in the present configuration example, a method of weakening the irradiation intensity of the laser beam A on the sheet 1 is adopted. , Is not necessarily limited to this,
Prior to the main reading, any method may be used as long as the outline of the image information accumulated and recorded on the sheet 1 is grasped in advance, and the reading conditions described later can be determined based on this.

FIG. 2 shows an example in which the pre-reading means 50 determines the reading conditions (particularly the reading sensitivity) of the photoelectric conversion means 20 in the main reading based on the image information obtained by the pre-reading. Image signal V2 obtained by look-ahead
Is sent to a histogram creating unit 54 that creates a histogram of the intensity of the image signal for each pixel (that is, a histogram of the amount of stimulated emission). The histogram created by the histogram creating means 54 is sent to the histogram analyzing means 56 and analyzed. FIG. 3 (A) shows a histogram pattern in the case of chest imaging, of which, for example, F is the mediastinum, G is the heart, H is the lung field, I is the skin and soft parts, and J is the skin. It is possible to know that it is outside the subject (that is, a plain part), and by analyzing the histogram in this way, an overview of the stored energy stored in the entire sheet, that is, a desired image information range (for example, from the mediastinum to the soft part) The maximum stimulating light emission amount S1 and the minimum stimulating light emission amount S2) can be obtained, and the reading sensitivity of the photoelectric conversion means 20 is set based on these based on the following. The figure
FIG. 3 (B) shows the histogram created by the histogram creating means 54 on the diagram showing the relationship between the amount of stimulated emission light B and the output value of the photoelectric conversion means 20. This figure 3
In (B), the horizontal axis indicates the amount of stimulated emission light B on the sheet 1, and the vertical axis indicates the output value of the photoelectric conversion means 20 as a digital value (that is, the output signal V2 of the A / D conversion circuit 33). It is a thing.

In this manner, a histogram of the amount of stimulated light emission is prepared by pre-reading, and the maximum amount of stimulated light emission S1 and the minimum amount of stimulated light emission within the desired image information range are obtained from the histogram.
Obtain S2, and set S1 so that S1 and S2 each become an appropriate output image.
Q1 and Q2 which are input signal ranges of the signal processing means 30 (that is, output signal ranges of the photoelectric conversion means 20) are determined in correspondence with 1 and S2.

By changing the scale factor expressed from the determined S1, S2 and Q1, Q2 in accordance with the size (S1-S2) of the desired range of the amount of stimulated emission, the signal processing means The magnitude of the range of the input signal level to 30 can be matched to the magnitude of the desired input signal level (Q1-Q2). Next, the reading sensitivity is changed so that the position in the range of the input signal level always matches the position in the range of the desired input signal level.

In this configuration example, the image signal V0 read by the photoelectric conversion means 20 is logarithmized by the logarithmic amplifier 32, and the logarithmized image signal V1 is converted into an A / D converter 33 for 10 bits (digital value 0). To 1023) digital signal V2. Therefore, the size (S1-S2) of the range of the amount of the stimulating light B emitted from the sheet 1 that can be output as an image signal by the photoelectric conversion means 20 is made to correspond to the 10-bit digital signal V2. In addition, the amount of stimulated emission light B (S3 in FIG. 3 (B)) emitted from the transparent portion (J in FIG. 3 (A)) of the radiation image information accumulated and recorded on the sheet 1 is: The reading sensitivity is set so as to be larger than the light amount corresponding to the upper limit of the image recording available area (in this example, the range of the amount of stimulated emission light capable of giving a digital value of 0 to 1023) L of the photoelectric conversion means 20. The reading sensitivity can be adjusted by changing the high voltage HV of the photoelectric conversion means 20. Therefore, a control signal V3 based on the histogram analysis obtained as described above is obtained, and the control signal V3 is sent to the sensitivity setting means 30, and the high voltage HV applied to the photoelectric conversion means 20 is changed to obtain the photoelectric signal. The reading sensitivity of the conversion means 20 is set.

In such a pre-reading, the irradiation amount P0 of the laser beam A when scanning an image area other than a blank portion in a main reading to be described later (hereinafter referred to as "steady state") is obtained in advance. You can also.

Next, a method of controlling the irradiation amount of the laser beam A to the sheet 1 in the main reading will be described with reference to FIG. First, after the reading sensitivity is set as described above, before performing the main reading, the conveying direction of the conveying unit 60 is reversed (X1 direction in FIG. 1), and the sheet 1 is returned to the original position (before performing the pre-reading). Position). First, the irradiation amount of the laser beam B is set to a value P0 in a steady state in the main reading. This value P0 can be obtained by analyzing the histogram obtained by pre-reading as described above, or a predetermined value can be set corresponding to the shooting menu. In such a state, the laser beam A is scanned on the sheet 1 as described above, and the radiation image information stored and recorded on the sheet 1 is read by the photoelectric conversion unit 20.

FIG. 4A shows a subject image K0 stored and recorded on the sheet 1, where K1 is a blank portion.
FIG. 4B shows a change in the light amount value of the stimulated emission light B emitted from the sheet 1 when the laser beam A scans the broken line portion of FIG. 4A. 4) shows the irradiation amount of the laser light A per unit area irradiated on the sheet 1, that is, the change of the irradiation energy of the laser light A.
(D) shows a change in the image signal (the output V1 of the logarithmic amplifier 32 in this configuration) read by the photoelectric conversion means 20. FIG. 4E shows that the image signal V1 is converted by the A / D conversion circuit 33.
5 shows a change in the value V2 digitized in the step S1. 4 (B) to 4 (E) are shown by solid lines when the excitation light control according to the present invention, that is, when the irradiation amount of the laser beam B to the sheet 1 is not controlled. The characteristics are shown.

The output signal V1 of the logarithmic amplifier 32 is monitored by the monitor circuit 42, and based on the output of the monitor circuit 42,
The AOM 46 is controlled by the excitation system control circuit 44 so that the output signal level obtained by detecting the amount of the stimulated emission light B emitted from K1 is as small as possible within a range larger than the upper limit of the read signal area of the photoelectric conversion means 20. To attenuate the amount of laser light A. In this manner, by changing (attenuating) the light amount of the laser light A passing through the AOM 46, the irradiation amount of the laser light A per unit area irradiated on the sheet 1, that is, the laser light A on the sheet 1 Excitation energy can be reduced. As described above, the emission amount of the stimulated emission light changes depending on the energy amount of the excitation light (laser light A) per unit area of the sheet 1. Therefore, the monitor circuit 42 monitors the image signal V1 to make it clear. Department K1
When the excitation system control circuit 44 determines that the amount of the stimulated emission light B is large, the amount of the stimulated emission light emitted from the transparent portion K1 is reduced by attenuating the amount of the laser light A passing through the AOM 46. Can be reduced.
By repeating such scanning, the amount of stimulated emission light emitted from the transparent portion K1 rapidly decreases. As described above, the smaller the amount of stimulated emission light, the smaller the amount of stimulated emission afterglow. Will be able to In addition, since the excitation light (laser light A) is attenuated to prevent the afterglow afterglow itself, the S / N can be improved. Changes in the amount of the stimulating light B when the excitation light is controlled as described above are shown by broken lines in FIGS. 4 (B) to 4 (E).

On the other hand, in the portion K0 other than the transparent portion, the irradiation energy of the laser beam A is set to the value P0 in the steady state, so that the image signal V1 at an appropriate signal level as image information required for diagnosis is obtained. Etc. can be obtained,
It can be displayed on a display device as a visible image with an appropriate gradation.

In the above description, the method of attenuating the amount of light applied to the sheet 1 by the AOM 46 when controlling the energy amount of the excitation light (laser light A) has been described. However, the present invention is not limited to this. A visible semiconductor laser may be used as 11, and the intensity of the laser light A emitted from the visible semiconductor laser may be directly modulated. Further, the transfer speed may be changed by the transfer means 60, or the laser light may be changed. A method of changing the relative speed of the excitation light to the sheet 1, such as changing the scanning speed of A, can also be used.

In the above description, a method of performing pre-reading prior to main reading when setting the reading sensitivity of the photoelectric conversion means 20 has been described, but it is not always necessary to perform pre-reading. For example, since a desired reading sensitivity level at the time of reading is known in advance by a photographing menu of the subject such as a chest or a heart, a plurality of photographing menus of the subject may be associated with a plurality of different photographing menus. The sensitivity level of the reading sensitivity may be registered in advance, and among the plurality of registered sensitivity levels, the sensitivity level corresponding to the imaging menu of the radiation image information to be read may be set as the reading sensitivity.

When erasing the residual energy of a sheet for which reading has been completed, the level of the read signal may be subjected to predetermined signal processing to calculate the erasing energy. When the present invention is applied, the signal level of the blank portion is read with a reduced level, so that if the conventional calculation method is used as it is, there is a possibility that a correct erase energy level cannot be calculated. on the other hand,
By controlling the energy amount of the excitation light as in the present invention, the stimulated emission light emitted from the transparent portion K1 is made as small as possible within a range larger than the upper limit of the read signal area of the photoelectric conversion means 20. Since the control is performed, the problem that the read signal level of the blank portion is large and exceeds the linear range of reading by the photoelectric conversion means is solved, and the problem that the correct signal level cannot be recognized is eliminated. Therefore, by referring to information on how much the excitation light has been attenuated when calculating the erasing energy, it is possible to calculate the erasing energy with higher accuracy than before.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a radiation image information reading apparatus according to the present invention.

FIG. 2 is a diagram for explaining the operation of a pre-reading means of the radiation image information reading apparatus.

FIG. 3 is a diagram illustrating a relationship between the amount of stimulated emission light and a signal read by a photoelectric conversion unit.

FIG. 4 is a diagram illustrating a method of controlling the energy of excitation light.

[Explanation of symbols]

 10 Excitation light irradiation means 20 Photoelectric conversion means 30 Signal processing means 40 Irradiation energy control means 50 Look-ahead means

Claims (6)

[Claims] 1. A stimulable fluorescent recording medium in which radiation image information of a subject is stored and recorded by irradiating the recording medium with excitation light to emit stimulating light, and the stimulating light emitted from the recording medium is emitted. In a radiation image information reading method for reading image information of the subject by reading emitted light with a photoelectric conversion unit, the stimulated emission light emitted from a transparent portion of the radiation image information accumulated and recorded on the recording medium The reading sensitivity of the photoelectric conversion unit is set so that the light amount of the photoelectric conversion unit is larger than the light amount corresponding to the upper limit of the image recordable area of the photoelectric conversion unit. It is characterized in that the irradiation energy of the excitation light is controlled so that the signal level obtained by reading the stimulated emission light becomes smaller within a range larger than the upper limit of the read signal area of the photoelectric conversion means. Radiation image information reading method and. 2. Prior to reading image information of the subject, pre-reading of stimulating light emitted from the recording medium is performed, and the reading sensitivity is set based on the image information obtained by the pre-reading. The method for reading radiation image information according to claim 1, wherein: 3. A plurality of sensitivity levels of the reading sensitivity are registered in advance in correspondence with a plurality of different photographing menus of the subject, and a radiographic image information reading menu to be read is selected from the plurality of registered sensitivity levels. 2. The radiation image information reading method according to claim 1, wherein the sensitivity level corresponding to the following is set as the reading sensitivity. 4. Excitation light irradiating means for irradiating excitation light to a stimulable fluorescent recording medium in which radiation image information of a subject is accumulated and recorded so as to emit stimulated emission light from the recording medium, and light emitted from the recording medium. A photoelectric conversion unit for reading the stimulated emission light, wherein the amount of the stimulated emission light emitted from the transparent portion of the radiation image information stored and recorded on the recording medium is A sensitivity setting unit for setting a reading sensitivity of the photoelectric conversion unit so as to be larger than an amount of light corresponding to an upper limit of an image recordable area of the photoelectric conversion unit; and light is emitted from the transparent portion by the photoelectric conversion unit. As the signal level of reading the stimulated emission light is reduced within a range larger than the upper limit of the read signal area of the photoelectric conversion unit,
A radiation image information reading apparatus, comprising: irradiation energy control means for controlling irradiation energy of the excitation light. 5. A read-ahead means for pre-reading the stimulating light emitted from the recording medium prior to reading the image information of the subject, wherein the sensitivity setting means comprises an image information obtained by the pre-read. 5. The radiation image information reading apparatus according to claim 4, wherein the reading sensitivity is set based on the following. 6. A registration unit for registering a plurality of sensitivity levels of the reading sensitivity in advance corresponding to a plurality of different photographing menus of the subject, wherein the sensitivity setting unit includes a plurality of registered sensitivity levels. 5. The radiation image information reading apparatus according to claim 4, wherein the sensitivity level corresponding to an imaging menu of the radiation image information to be read is set as the reading sensitivity.