JPH05142684A - Arithmetic method and device for image information reading sensitivity - Google Patents

Abstract

PURPOSE:To provide arithmetic method and device for image information reading sensitivity by which the image information of good quality is rapidly read without readjusting the read gain of an image reader even in the case that the sensitivity of a sheet where the image information is recorded is changed because of version renewal. CONSTITUTION:A control circuit 24 reads the central sensitivity KC of the sheet to be read SC from a RAM 66, and reads the relative sensitivity KIP of the sheet SC and the relative sensitivity KO of a sheet SO for adjustment from a sensitivity parameter storage circuit 60. Then, the circuit 24 calculates a sensitivity coefficient KN from the relative sensitivity KIP, KO, and the central sensitivity KC, and further obtains reading sensitivity. Therefore, the image of good quality is rapidly and surely read even when the sensitivity of the sheet SC is different.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates a stimulable phosphor sheet, on which radiation image information is stored and recorded, with a laser beam or the like, and photoelectrically detects excited stimulated emission light using a photomultiplier. A method and apparatus for calculating image information reading sensitivity in an image reading apparatus, wherein a high-quality image signal is obtained by precisely calculating an applied voltage of a photomultiplier that determines reading sensitivity for reading the stimulated emission light. The present invention relates to a method and apparatus for calculating the image information reading sensitivity that enables the above.

[0002]

2. Description of the Related Art For example, in a medical field, a radiation image recording / reproducing system is used which obtains a radiation image of a subject by using a stimulable phosphor (stimulable phosphor). Here, the stimulable phosphor means that when it is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron rays, ultraviolet rays, etc.), a part of this radiation energy is accumulated, and then excitation light such as visible light is excited. Is a phosphor that stimulates light emission in response to the stored energy.

The above-mentioned radiation image recording / reproducing system uses this stimulable phosphor, and a sheet having a layer of the stimulable phosphor for temporarily storing the radiation image information of a subject such as a human body (hereinafter referred to as "accumulative phosphor sheet"). Or simply referred to as a "sheet"), the stimulable phosphor sheet is scanned with excitation light such as laser light to generate stimulated emission light, and the stimulated emission light is photoelectrically read to generate an electrical signal. Based on this electric signal, a radiation image of the subject is output as a visible image on a recording material such as a photographic photosensitive material or a display device such as a CRT.

Therefore, in such a radiation image recording / reproducing system, when the radiation image is read from the stimulable phosphor sheet on which the radiation image is accumulated and recorded, specifically, the following method is used.

That is, a stimulable phosphor sheet is two-dimensionally scanned with a light beam such as a laser beam, and stimulated emission light emitted from the sheet is detected in time series by a photodetector such as a photomultiplier. And obtain image information. In this case, the two-dimensional scanning of the light beam is usually performed by transporting the stimulable phosphor sheet in the sub-scanning direction by a belt conveyor and deflecting the light beam in the main scanning direction orthogonal to the transport direction of the sheet. Has achieved.

The reading sensitivity for reading the stimulated emission light is determined by the value of the high voltage applied to the photomultiplier. This high voltage is the sensitivity and reading of the reference stimulable phosphor sheet. It is calculated based on a sensitivity parameter represented by a relative value to the sensitivity of the stimulable phosphor sheet.

However, the sensitivity of the read accumulative phosphor sheet may be changed due to version upgrade or the like, and if the sensitivity of the read accumulative phosphor sheet is different from the previously stored sensitivity, it is written in the ROM. The sensitivity parameter was rewritten, and the read sensitivity was set as a reference by using the upgraded stimulable phosphor sheet.

That is, reference image information, for example,
Read the stimulable phosphor sheet with a new sensitivity, in which an image uniformly exposed at 1 mR (milliregen) is recorded,
The sensitivity parameter of the upgraded stimulable phosphor sheet is obtained from the read result, and the sensitivity parameter of the other stimulable phosphor sheet is calculated based on this, and the RO
The sensitivity parameter written in M was rewritten, and readjustment such as resetting the high voltage of the photomultiplier, which serves as a reference for reading the upgraded storage phosphor sheet, was performed.

[0009]

However, in the above-mentioned reading sensitivity calculation method in the prior art, the sensitivity of the upgraded reference stimulable phosphor sheet is previously stored in the ROM.
Each time the sensitivity of the reference stimulable phosphor sheet written in is different, the contents of the ROM must be rewritten.
When the read-accumulation phosphor sheet has a plurality of sensitivities, there are problems that the method of use becomes complicated and much adjustment time is spent.

The present invention has been made to solve such a conventional problem, and an image reading apparatus can be used even when the sensitivity of the read-accumulation phosphor sheet is changed by version upgrade or the like. When readjusting the reading gain of R
It is an object of the present invention to provide an image information reading sensitivity calculation method and device that can read image information quickly and without the need to rewrite the sensitivity parameter in the OM.

[0011]

In order to achieve the above object, the first aspect of the present invention is to irradiate a stimulable phosphor sheet on which radiation image information is recorded with a laser beam or the like so that the stimulable phosphor is A reference accumulative phosphor sheet, which is a method of calculating image information reading sensitivity in an image information reading device that photoelectrically detects stimulated emission light excited according to image information recorded on a sheet by using a photomultiplier. The first step of reading out the relative sensitivity of the stimulable phosphor sheet to be read from the sensitivity parameter storage means for storing the relative sensitivity represented by the relative value of the reference sensitivity and the sensitivity parameter storage means used for adjustment. A second step of reading the relative sensitivity of the stimulable phosphor sheet, the relative sensitivity of the read stimulable phosphor sheet, and the relative sensitivity of the stimulable phosphor sheet used for the adjustment; The center sensitivity in reading a third step of calculating the sensitivity coefficients from the center sensitivity constant has been read, the stimulable phosphor sheet used for the adjustment,
A fourth step of calculating the reading sensitivity for reading the image information recorded on the read stimulable phosphor sheet based on the sensitivity coefficient obtained in the third step.

Further, a second aspect of the invention is to irradiate a stimulable phosphor sheet, on which radiation image information is recorded, with a laser beam or the like to excite the stimulable phosphor sheet according to the image information recorded on the stimulable phosphor sheet. An arithmetic device of image information reading sensitivity in an image information reading device for photoelectrically detecting exhaust emission light by using a photomultiplier, setting means for setting a central sensitivity of reading, and a reference of a reference accumulative phosphor sheet. Sensitivity parameter storage means for storing the relative sensitivity of the accumulative phosphor sheet and the read accumulative phosphor sheet used for the adjustment represented by the relative value with the sensitivity, and the central sensitivity set from the setting means, From the relative sensitivity of the stimulable phosphor sheet and the relative sensitivity of the stimulable phosphor sheet to be read used for adjustment stored in the sensitivity parameter storage means, A sensitivity coefficient calculation means for calculating a sensitivity coefficient of the light-emitting sheet, and a reading sensitivity calculation means for calculating a reading sensitivity for reading the image information recorded on the storage phosphor sheet to be read from the sensitivity coefficient. And

[0013]

The relative sensitivity of the adjusting stimulable phosphor sheet and the relative sensitivity of the stimulable phosphor sheet to be read, which are represented by the relative values of the reference sensitivity of the reference stimulable phosphor sheet, and the sensitivity set by the setting means. The sensitivity coefficient calculation means calculates the sensitivity coefficient of the read and accumulative phosphor sheet from the central sensitivity of the read and accumulative phosphor sheet. Based on this sensitivity coefficient, the reading sensitivity calculation means calculates the reading sensitivity for reading the image information of the read stimulable phosphor sheet.

Therefore, even if the sensitivity of the stimulable phosphor sheet to be read differs every time image information is read, it is not necessary to readjust the read sensitivity.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a method and apparatus for calculating an image information reading sensitivity according to the present invention will be described in detail below with reference to the accompanying drawings with reference to the preferred embodiments.

In FIG. 1, reference numeral 10 indicates an image reading apparatus for carrying out the present invention.

The image reading device 10 includes a laser scanning unit 12 for scanning the stimulable phosphor sheet S on which image information is stored and recorded by a light beam La in the main scanning direction (direction of arrow C in FIG. 1), and the laser scanning unit 12. An image reading unit 14 that photoelectrically converts stimulated emission light that stimulates emission by scanning with the light beam La, and a synchronization signal generation unit 16 that detects a scanning position of the light beam Lb and generates a start point detection signal and a synchronization signal. A signal processing unit 18 that digitizes a signal from the image reading unit 14 by a synchronization signal and stores the digitized signal in an image memory.

Further, the image reading device 10 includes a display device 20 such as a CRT which displays the output signal from the signal processing unit 18 as a visible image as necessary, and a high voltage applied to the image reading unit 14. High voltage generating circuit (hereinafter referred to as HV generating circuit) 22 for generating
2 and the control circuit 24 that controls the high voltage generated by the control circuit 2.

The laser scanning unit 12 emits a light beam L, a laser light source 26, a beam expander 28 for shaping the light beam L into a beam having a desired thickness, and a galvanometer mirror for reflecting and deflecting the light beam L. 30, a scanning lens 32 arranged in the optical path of the light beam L, and a half mirror 34 arranged in the optical path extending in the main scanning direction.

The half mirror 34 reflects, of the incident light beam L, a light beam required for scanning as a light beam La for scanning, and transmits the remaining light beam as a light beam Lb for synchronization. The light beam La reflected by the half mirror 34 is the galvanometer mirror 30.
The stimulable phosphor sheet S is scanned in the main scanning direction (the direction of arrow C) in order to make the rotation action.

The image reading section 14 is a long photomultiplier 36 as a photoelectric conversion means, and light for guiding stimulated emission light emitted from the stimulable phosphor sheet S by the light beam La to the light receiving surface of the photomultiplier 36. And a guide 38. In this case, the light receiving surface of the photomultiplier 36 extends in the main scanning direction, and the incident surface of the light guide 38 is close to the stimulable phosphor sheet S and the main scanning direction (arrow C).
Direction).

The synchronizing signal generator 16 is the half mirror 3
4, a transmission portion 40a that transmits the light beam Lb that has passed through 4,
Also, a grid 42 in which reflecting portions 40b for reflecting the light beam Lb are alternately arranged along the scanning direction of the light beam Lb, and a cylindrical light guide arranged behind the grid 42. 44 and a light beam L transmitted from the grid 42 provided at both ends of the light guide 44.
It is composed of optical sensors 46a and 46b for detecting b, and a synchronization signal generation circuit 48 for generating a start point detection signal and a synchronization signal based on grid signals output from the optical sensors 46a and 46b. In this case, a wide transmission part (not shown) is formed at the top of the grid 42 to detect the start point of the effective scanning area of the stimulable phosphor sheet S.

On the other hand, the signal processing section 18 includes a log amplifier circuit 50 for logarithmically amplifying the output electric signal of the photomultiplier 36, and an A / D conversion circuit for converting an analog signal supplied from the log amplifier circuit 50 into a digital signal. 52
An image processing circuit 54 for performing gradation processing, frequency processing and the like on the digital signal; an image memory 56 for storing the image signal subjected to the image processing; and an image signal stored in the image memory 56. The display device 20 including a D / A conversion circuit 58 for converting into an analog value and a CRT or the like forms a reproduced image as a visible image as needed by a signal output from the D / A conversion circuit 58.

The control circuit 24 stores sensitivity information for each type of the stimulable phosphor sheet S, that is, a sensitivity parameter storage circuit 60 for storing a so-called sensitivity parameter as a look-up table (hereinafter referred to as LUT), and a stimulable phosphor to be read. A bar code reader 62 for reading a bar code provided on the body sheet S _C , an ID terminal 64 for inputting a standard sensitivity K _C for reading image information recorded on the read sheet S _C , and the standard sensitivity RA that temporarily stores K _C, etc.
M66 is connected.

The standard sensitivity K _C is a standard value of the sensitivity coefficient determined by the photographed part recorded on the read sheet S _C , for example, the head or legs.

Image reading apparatus 10 for carrying out the present invention
Is basically configured as described above. Next, when the sheet to be read S _C is loaded in the image reading device 10 and the image information recorded on the sheet to be read S _C is read. The action and effect of will be described.

The sheet S loaded in the image reading device 10 is conveyed to the image reading position under the action of a sheet body conveying mechanism (not shown), and is further conveyed in the sub scanning direction (direction of arrow A in FIG. 1) at the image reading position. At this time, the light beam L emitted from the laser light source 26 scans the sheet S in the main scanning direction (direction of arrow C in FIG. 1) by the rotation of the galvanometer mirror 30.

That is, the light beam L is shaped into a beam having a desired thickness by the beam expander 28, reaches the half mirror 34 via the galvanometer mirror 30 and the scanning lens 32, and is scanned by the half mirror 34. It becomes the light beam La and the light beam Lb for synchronization.
The light beam La reaches the sheet S, and the light beam Lb reaches the grid 42.

The sheet S irradiated with the light beam La emits stimulated emission according to the stored image record information of the object. This stimulated emission light is incident on the photomultiplier 36 via a light guide 38 arranged in the main scanning direction of the sheet S,
It is converted into an electrical signal. Then, the signal from the photomultiplier 36 is input to the A / D conversion circuit 52 via the log amplifier circuit 50.

On the other hand, the light beam Lb which has passed through the half mirror 34 is incident on the grid 42 which constitutes the synchronizing signal generator 16. Next, the light beam La is scanned in the direction of arrow D by the swing motion of the galvanometer mirror 30, and moves from one end of the grid 42 to the other end. In this case, the light beam L transmitted through the transmission part 40a of the grid 42
b enters the light guide 44.

The light beam Lb is the light beam L of the light guide 44.
The light guide 44 is diffused in various different directions by a diffusion zone (not shown) formed on the side opposite to the incident side of b.
Total reflection is repeated inside to reach the optical sensors 46a and 46b, and photoelectric conversion is performed to generate a grid signal. In this case, the grid signal is the grid 4 as described above.
The output signal is phase-modulated due to the wide transmission part (not shown) at the start point of 2.

Therefore, the A / D conversion circuit 52 takes in the image signal with the wide pulse related to the phase modulation section as the effective scanning start point on the main scanning line. The captured image signal is subjected to frequency processing, gradation processing, etc. by the image processing circuit 54 and recorded in the image memory 56, and the image signal recorded in the image memory 56 is necessary via the D / A conversion circuit 58. Accordingly, it is displayed as a visible image on the display device 20 such as a CRT.

FIG. 2 shows an LUT stored in advance in the sensitivity parameter storage circuit 60. This LUT is a type indicating the sensitivity of the sheet S, and the minimum read pixel size when reading image information from each sheet S (hereinafter referred to as the LUT). , Sampling size). With this relative sensitivity, the sensitivity K _S of the reference sheet S _S is set to “0”,
The sensitivities of the other sheets S are shown by relative values of the number of digits with respect to the sensitivities of the reference sheets S _S , where +100 indicates a one-digit high sensitivity and -100 indicates a one-digit low sensitivity.

By the way, in the image reading device 10, 1 mR
The image information of the sheet S that has been uniformly exposed by (millilen) is read, and the reading sensitivity is adjusted. That is, if the type of the sheet S used for the adjustment is S _O2 and the sampling size for reading the image information is 100 μm, the relative sensitivity K _{O of} the image signal read from the sheet S _O2.
Is adjusted to −5 (see FIG. 2), the high voltage V _O of the HV generation circuit 22 is adjusted. The high voltage V _O is the image reading device 10.
A reading sensitivity, high voltage V _O is stored in the RAM66 together with the relative sensitivity K _O of the sheet S _O2 used in the adjustment.

An image whose reading sensitivity is adjusted in this way
Relative sensitivity K _IPThe read sea
To S_C2Reading sensitivity when reading image information recorded on
A method of calculating is explained.

[0036] First, the operator inputs the central sensitivity K _C of reading of the reading the sheet S _C2 from the ID terminal 64, and is loaded into the image reading apparatus 10 to be read sheet S _C2. The read sheet S _C2 is attached with a barcode for recording the sheet type, sampling size and the like.

In this case, the central sensitivity K _C is a reading sensitivity that serves as a reference when reading a recorded image, and when the image is taken on the sheet S _C2 to be read, the image taking part, for example, the head or legs, etc. Since the reference radiation dose irradiated by is different, it is set corresponding to this reference radiation dose.

Therefore, the control circuit 24 controls the ID terminal 6
The center sensitivity K _C input from 4 is read, and this is RA
The data is stored in M66 (step S1), and the type of the sheet S _C2 to be read and the sampling size, for example, 100 μm are read from the barcode through the barcode reader 62 (step S2).

The control circuit 24 reads the relative sensitivity K _IP of the read sheet S _C2 from the sensitivity parameter storage circuit 60 based on the information on the type of the read sheet S _C2 and the sampling size of 100 μm (step S3). The relative sensitivity K _O of the adjustment sheet S _O2 stored in advance in the RAM 66 is read (step S4).

The sheet to be read S_C2Relative sensitivity of_IPWhen,
Sheet S used for adjustment_O2Relative sensitivity of_OAnd ID
Sheet S input from terminal 64_C2Feeling of heart
Degree K _CAnd the sensitivity coefficient K based on the following equation_NCompute
(Step S5).

K _N = K _C − (K _IP −K _O ) (1) The sensitivity coefficient K _N obtained by the above equation (1) and the high voltage V _O of the sheet S _O2 used for the adjustment, From the coefficient k and the control circuit 24, the high voltage V _N that determines the reading sensitivity of the sheet S _{C2 to} be read is calculated according to the following equation (step S6).

V _N = V _O × 10 ^{k * KN} (2) Here, k is data peculiar to the photomultiplier 36, and is the height applied to the photomultiplier 36 required to change the sensitivity by one digit. The number of digits of change in the voltage V _O (normally 0.
12 to 0.14). Note that this data is also stored in the RAM 66 in advance.

In this way, the photomultiplier 3
The value of the high voltage V _N applied to 6 is determined.

In this case, in the above equation (1), if K _IP > K _O , the sensitivity coefficient K _N becomes smaller than the central sensitivity K _C , and K
_{If IP} <K _O, it indicates that the sensitivity coefficient K _N is larger than the central sensitivity K _C.

As described above, in this embodiment, the LUT of the relative sensitivity represented by the type of the sheet S and the sampling size is used.
Is stored in advance, and the relative sensitivity K _O of the sheet S _O used for the adjustment read from the LUT, the relative sensitivity K _IP of the read sheet S _C , and the read sheet S input from the ID terminal 64. and a _C2 central sensitivity K _C of calculating the sensitivity coefficient K _N, be determined and the sensitivity coefficient K _N, and the high voltage V _O obtained by adjusting the reading sensitivity of the read sheet S _C and a coefficient k This makes it possible to easily calculate the optimum reading sensitivity even when the type of sheet S _{C2 to} be read is different.

Further, since the sensitivity of each sheet S stored in the LUT is stored as a relative value with respect to the sensitivity K _S of the reference sheet S _S , the sheet S _O2 used for adjustment is stored.
It is not limited to the type of.

When the type of the sheet S _C2 to be read increases due to version upgrade or the like, additional recording is simply performed in the LUT stored in the sensitivity parameter storage circuit 60.
The new sensitivity stimulable phosphor sheet can be used immediately.

[0048]

With the method and apparatus for calculating the image information reading sensitivity according to the present invention, it is not necessary to readjust read sensitivity even if the sensitivity of the stimulable phosphor sheet to be read is different each time image information is read. Therefore, even when adjusted with a stimulable phosphor sheet having any sensitivity, it is possible to quickly calculate the reading sensitivity of a plurality of stimulable phosphor sheets having different sensitivities,
In addition, it becomes possible to carry out accurately. Therefore, the image information can be read quickly and accurately.

When the sensitivity of the stimulable phosphor sheet to be read is added due to version upgrade or the like, the relative sensitivity stored in the sensitivity parameter storage means is simply rewritten, and the new version of the stimulable phosphor sheet is stored. It is possible to quickly adjust the reading sensitivity when reading the image information stored in.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image reading apparatus that implements an image information reading sensitivity calculation method and apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a LUT of sensitivity parameters.

FIG. 3 is an operation flowchart for adjusting the image information reading sensitivity by the image reading apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Image reading device 12 ... Laser scanning part 14 ... Image reading part 16 ... Synchronous signal generation part 18 ... Signal processing part 20 ... Display means 22 ... High voltage generation circuit (HV generation circuit) 24 ... Control circuit 36 ... Photomultiplier 52 ... A / D conversion circuit 60 ... Sensitivity parameter storage circuit 62 ... Bar code reader 64 ... ID terminal 66 ... RAM S ... Storage phosphor sheet

Claims (2)

[Claims] 1. A photomultiplier that stimulates stimulated emission according to image information recorded on the stimulable phosphor sheet by irradiating the stimulable phosphor sheet on which radiation image information is recorded with laser light or the like. A method for calculating the image information reading sensitivity in an image information reading device that photoelectrically detects using a pliers, and a sensitivity parameter memory that stores the relative sensitivity represented by the relative value with the reference sensitivity of the reference accumulative phosphor sheet. A first step of reading the relative sensitivity of the stimulable phosphor sheet to be read from the means; a second step of reading the relative sensitivity of the stimulable phosphor sheet used for adjustment from the sensitivity parameter storage means; Third, a sensitivity coefficient is calculated from the relative sensitivity of the stimulable phosphor sheet, the relative sensitivity of the stimulable phosphor sheet used for the adjustment, and the set center sensitivity of reading.
Image information recorded on the read stimulable phosphor sheet from the central sensitivity at the time of reading the stimulable phosphor sheet used for the adjustment and the sensitivity coefficient obtained at the third step. A fourth step of calculating the reading sensitivity to read, and a method of calculating the image information reading sensitivity, comprising: 2. A photomultiplier that emits stimulated emission light that is excited in accordance with the image information recorded on the stimulable phosphor sheet by irradiating the stimulable phosphor sheet on which radiation image information is recorded with laser light or the like. A device for calculating the image information reading sensitivity in an image information reading device that photoelectrically detects using a plier, which is a relative value between the setting means for setting the central reading sensitivity and the reference sensitivity of the reference accumulative phosphor sheet. Sensitivity parameter storage means for storing the relative sensitivity of the accumulative phosphor sheet and the read accumulative phosphor sheet used for the adjustment represented, the central sensitivity set from the setting means, and the sensitivity parameter storage means Based on the relative sensitivity of the stimulable phosphor sheet and the relative sensitivity of the read stimulable phosphor sheet used for the stored adjustment, the sensitivity factor of the read stimulable phosphor sheet is determined. The image information reading sensitivity, which comprises: a sensitivity coefficient calculating means for calculating the reading sensitivity, and a reading sensitivity calculating means for calculating the reading sensitivity for reading the image information recorded on the stimulable phosphor sheet to be read from the sensitivity coefficient. Computing device.