JPS6190280A - Radiograph reading device - Google Patents

Abstract

PURPOSE:To satisfy the read accuracy and read speed by providing plural reading head directing towards the cumulative fluorescent sheet wound around the circumference of a rotating drum and obtaining plural and simultaneous scanning by the rotation of the drum. CONSTITUTION:A rotating drum 11 rotates to the main scanning direction c at a specified constant speed, and a group of read head 121-12n synchronizes with this rotating speed and moved towards the sub-scanning direction d. Namely, the read heads 121-12n are first set at the right edge of the drum, and at the same time that the drum 11 rotates to main scanning direction c, the read heads 121-12n moves as one set towards the sub-scanning direction d, and the scanning line of the heads 121-12n will be E1-En. Each of the scanning line E1-En is bordering on each other in picture element pitch, and at one rotation of the drum 11, n number of read heads 121-12n scan the width W defined by 'picture element X n', and the edge of the width W contacts the edge of previous scanning edge W. Therefore, if the number n is increased, the rotation of the drum 11 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a radiation image reading device that can satisfy both reading accuracy and reading speed.

(Prior Art) As a conventional image reading device of this type, there is one shown in FIG. This converts the light beam emitted from a light beam generator 1 such as a laser into a mirror 2, a beam expander 3,
By passing through the mirror 4, you can change its direction and shape to create a galvano mirror or rotating polygon mirror (polygon mirror).
The light beam reflected and deflected by the deflector 5 is passed through a converging lens 6 such as an fθ lens and a mirror 7, and the light beam is passed through a converging lens 6 such as an fθ lens and a mirror 7. The phosphor sheet 8 is scanned along the main scanning direction a on the surface of the phosphor sheet (in which energy corresponding to the transmitted image of the subject is distributed and accumulated) by radiation such as a line, and the phosphor sheet 8 is excited. It is something that makes you The phosphor sheet 8 is
It is moved in the sub-scanning direction at a predetermined speed in synchronization with the main scanning. As a result, the stimulable phosphor sheet 8 sequentially emits stimulated light in the scanning order by the excitation light according to the radiation image stored and recorded in advance, and the emitted light is transmitted to the photoconductor 9 (for example, Utility Model Application No. 513-3126 The light is sequentially incident on a photodetector 10 such as a photomultiplier, where it is condensed and guided to a photodetector 10 such as a photomultiplier, where it is converted into a time-series electrical signal to obtain an electrical signal based on a radiation image.

In such a radiation image reading apparatus, it is desired to read stored images with good precision, that is, image quality, in as short a time as possible. However, image quality here refers to how minute spatial changes can be detected.
"Spatial resolution" and "gradation resolution," which refers to how minute changes in density (gradation) can be detected.

However, conventional reading devices scan with a single excitation light spot using a single beam and sequentially read the images stored and recorded on the stimulable phosphor sheet 8, which shortens the reading time. In order to achieve this, the scanning speed of the excitation light spot must be increased. Then, it is necessary to increase the scanning speed and obtain the necessary image quality, that is, spatial resolution and gradation reading accuracy.

Important factors that determine spatial resolution include the stimulated luminescence response speed of the stimulable phosphor and the frequency bandwidth of the luminescence detection system.

First, regarding the response speed of stimulated luminescence, a stimulable phosphor takes a finite amount of time after being irradiated with excitation light until the stimulated luminescence starts, or after the excitation light irradiation is cut off and until the stimulated luminescence disappears. If the response speed is slow, the reproduced image may cause a long trailing phenomenon in extreme cases. Therefore, the material is required to have sufficient high-speed response. Even if there is a highly efficient stimulable phosphor material that has high emission brightness relative to the excitation light illuminance, if the response speed is not sufficient, it should be used. materials with low efficiency and fast response must be used. This means that the level of the image signal obtained is lowered, and therefore only a reproduced image with insufficient gradation can be obtained.

On the other hand, in the luminescence detection system, the signal-to-noise ratio S/N is mainly dominated by shot noise because the stimulated luminescence from the stimulable phosphor is weak.

The magnitude of this shot noise is proportional to the square root of the frequency bandwidth of the light emission detection system. Therefore, in order to obtain the necessary spatial resolution, if the frequency bandwidth of the luminescence detection system is widened as the scanning speed increases, the S/N of the image signal obtained is
The unavoidable disadvantage is that the image quality deteriorates, the gradation resolution decreases, and the reproduced image becomes rough.

In this way, reading speed and accuracy, or image quality, are the same in conventional reading devices that use a single excitation light spot and a photodetection system.
There was a great deal of dissatisfaction with the idea that these were contradictory elements and that one had to be sacrificed.

(Object of the Invention) The present invention has been made in view of the above points, and its purpose is to provide a radiation image reading device that can satisfy both reading accuracy and reading speed. .

(Structure of the Invention) For this purpose, the radiation image reading device of the present invention has a stimulable phosphor sheet held around a rotating drum, and an excitation light irradiation section and an excitation light irradiation section facing the held sheet. A plurality of reading heads consisting of corresponding stimulated luminescence detection sections are provided,
Main scanning is performed by the rotation of the rotating drum, and sub-scanning is performed by moving the rotating drum relative to each reading head in the axial direction, so that a plurality of scanning lines are simultaneously scanned by the rotation of the rotating drum. ing.

(Example) Hereinafter, an example of the radiation image reading device of the present invention will be described. FIG. 2 shows one embodiment thereof. In this embodiment, a stimulable phosphor sheet 8 on which a radiographic image is recorded is wrapped around a rotating drum 11 and mounted.
While rotating this drum 11 in the main scanning direction C at a predetermined speed, the sheet 8 is excited with excitation light to cause stimulated luminescence, thereby reading an image.

121 to 12n are reading heads whose mutual positional relationship is fixed, each of which includes an excitation light irradiation section 12a and a photostimulator that detects and photoelectrically converts the stimulated light excited by the excitation light irradiation section 12a. It is configured in combination with the light emission detection section 12b. And these reading hands 12+-12
In the case of n, adjacent heads are arranged in a positional relationship shifted by a scanning line pitch (pixel pitch) in the axial direction of the drum 11 (sub-scanning direction d), but their arrangement in the sub-scanning direction d is - It is not a straight line, but is shifted by a predetermined angular interval in the main scanning direction C. This is because the scan line pinch is so narrow that a relatively large read head cannot be placed in a straight line at that pinch spacing.

In this embodiment, the rotary drum 11 is rotated at a predetermined constant speed in the main scanning direction C, and in synchronization with this speed, one group of reading heads 121 to 12n are integrally moved in the sub-scanning direction d. This synchronous relationship is such that during one rotation of the drum 11, the reading heads 12t to 12n of this one group move integrally in the sub-scanning direction d by a distance of r scanning line pitch x number of reading heads j. It is.

That is, in FIG. 3, the reading heads 121 to 12n
is positioned and set at the right end of the drum 11, and then the drum 11 is rotated in the main scanning direction C, and the first group of reading heads 121 to 12fl are integrally moved in the sub scanning direction d, so that each reading head 12t -12n scan line is E
+-En.

El is a scanning line excited and read by the reading head 12+, E2 is a scanning line similarly read by the reading head 122, and En is a scanning line similarly read by the reading head 12n. Each of these scanning lines E1 to En is a scanning line adjacent to each other with a pixel pinch, and when the rotating drum 11 rotates once, the n reading heads of one group °121 to 12n are scanned at a pitch of 1 pixel (scanning line pinch) x n
", and the width W is in contact with the adjacent previously scanned width portion. Multiple scan lines are
The recording medium, which is just cylindrical in shape, is traced along multiple spiral-shaped trajectories.

Therefore, if the number n of reading heads is increased, the rotating drum 110
The total number of rotations can be extremely reduced. That is, when the conventional scanning method shown in FIG. Since it is necessary to scan at each pixel pitch, the total number of rotations of the rotary drum 11 becomes extremely large. However, in this embodiment, as described above, a plurality of (n) scanning lines are scanned at the same time. The total number of rotations can be reduced.

Therefore, even if the scanning speed in the main scanning direction C is the same as before, the reading speed in the sub-scanning direction d is n times higher.

Of course, since the scanning speed per reading head is the same as in the prior art, it is possible to obtain an image with the same resolution and quality as in the prior art. From the above, the reading speed can be improved without sacrificing reading accuracy (image quality).

Conversely, if the overall reading speed is made the same as that of the single reading head in the above case, the rotational speed (main scanning speed) of the rotary drum 11 can be reduced to 1/n. Shot noise, which is a factor in S/H, is proportional to the square root of the bandwidth, and since the bandwidth is proportional to the main scanning speed, it is proportional to 1/n. Therefore, the S/N becomes S/Noc vri.

If the number n of reading heads is set to 4, the S/N will be doubled. That is, reading accuracy can be improved without sacrificing reading speed.

An encoder (not shown) is attached to the rotating shaft 11a of the rotating drum 11 to sequentially detect the rotational angular position thereof. A circuit is configured to detect the positional relationship. In addition, each reading head 121
.about.12n move integrally in the sub-scanning direction d (axial direction), and the circuit is configured so that the moving position can also be detected by another encoder provided in the moving mechanism as necessary.

In this way, one group of reading heads is moved in accordance with the amount of rotation of the drum 11, and reading is performed in an accurate width (sub-scanning direction). Of course, the amount of rotation of the drum and the movement of the first group of reading heads may be synchronized mechanically without using an encoder.

By the way, the encoder that detects the amount of rotation of the drum 11 can make the reading pitch in the main scanning direction C (rotation direction) constant by using the pulses. FIG. 4 is a diagram showing an example thereof. In the figure, image information (stimulated luminescence light) is read by a photomultiplier or the like of the stimulated luminescence detection section 12b of the reading head, passes through an amplifier 13, is held in a sample hold circuit 14, and is then sent to an A/D converter. 1
5, it is converted into a digital signal. Here, by inputting the encoder information to the sample bold circuit 14, the reading timing can be matched, and the reading pitch in the main scanning direction C can be made constant.

In this case, by making it possible to independently adjust the gain of each amplifier corresponding to each read head, it is possible to correct variations in excitation light and read sensitivity of each read head. This is the stimulated luminescence detection section 1 of the reading head.
Adjustment of the gain of 2b can be similarly performed.

In addition, the excitation light irradiation section 12a of the reading heads 12+ to 12n
In addition to configuring everything separately, including the light sources here:
A single common light source is configured, and a plurality of excitation light irradiation units 1 are transmitted from the light source using a flexible light guide such as an optical fiber.
It is also possible to conduct the light separately up to 2a. In the former case, a plurality of complex optical systems will be constructed around the rotating drum 11, but in the latter case, only the flexible light guide will need to face the rotating drum 11.
Design, manufacture, arrangement, and parts related to the excitation light irradiation section 12a
The adjustment process becomes extremely simple, and it is advantageous in terms of space and cost. Note that the stimulated luminescence detection sections 12b of the reading heads 12+ to 12n may be separated into a light condensing section and a detection section, and the two may be connected by a flexible light guide.

Further, the first group of reading heads 121 to 12n are connected to the rotating drum 1.
Although the positional relationship in the axial direction of 1 is fixed, it is not limited to this.

Further, as a light source for excitation light, a single wavelength laser light source, a multi-wavelength light emitting diode (LED), etc. can be used, but as a laser, a semiconductor laser is preferable because it is small in size, has good efficiency, and generates little heat.

Further, the above-mentioned stimulable phosphor sheet 8 may be used for the stimulable phosphor sheet 8 after being irradiated with the first light or high-energy radiation.
Thermal, mechanical, chemical, electrical, etc. stimulation (photostimulation excitation)
Accordingly, a phosphor that exhibits stimulated luminescence corresponding to the irradiation amount of initial light or high-energy radiation is used, but from a practical standpoint, it is preferable to use a phosphor that emits stimulated luminescence by stimulated excitation light of 500 nm or more. Good light body.

Examples of this phosphor include BaSO4:Ax (where A is Dy), as described in JP-A-48-80487.

At least one type of Tb, and X is 0.001≦x
<1 mol%. ), Japanese Patent Application Laid-open No. 1973-
Mg5O1:Ax described in No. 80488 (However, A is either Ho or Dy, and X is O, OO
1≦x1 mol%. ), Japanese Patent Application Publication No. 4
SrSO4:Ax described in No. 8-80489
(However, A is at least one of D)', Tb, and Tm, and X satisfies 0.001≦x<1 mol%. ), Mn is added to Na2SO4, CaSO4, BaSO4, etc. described in JP-A No. 51-29889.
, a phosphor containing at least one of Dy and Tb, Be0 described in JP-A-52-30487.
1L i F, fluorophores such as MgSO4 and CaF2,
L 12B described in JP-A No. 53-39277
407: Fluorescent material such as Cus Ag, JP-A-54-4
Li2O・ (B2Q2) described in No. 7883
x: Cu (where X is 2<'x≦3) and Li2O
・ (B202) x: cu, Ag (however, X is 2 x ≦
3), SrS:Ce, Sm, and SrS:Eu described in US Pat. No. 3,859,527.

Sm5La202 S: Eus Sm and (Zn,
Examples include phosphors represented by Cd)S:Mn and X (where X is halogen).

In addition, Zn described in JP-A No. 55-12142
S: Cu, Pb phosphor, general formula is Ba0-xAj! 20
3: Barium aluminate phosphor represented by Eu (0.8≦X≦10) and whose general formula is M'O x Si02:
A (However, ML is M g −, Ca , S r SZ n
%Cd or Ba, A is Cez T b, E
At least one of +J, Tm, Pb% Ti B i and Mn, and X satisfies 0.5≦X<2.5. )
Examples include alkaline earth metal silicate-based phosphors represented by:

Further, the general formula is (Ba1~.-, Mg, CaY)FX: eEn'' (where X is at least one of Br and C1, x,
y and e are numbers satisfying the following conditions, respectively: Q<x+y<Q, (3, xy≠0 and 10≦e≦5X10~2), an alkaline earth halide phosphor; The general formula described in JP-A No. 55-12144 is LnOX: xA (where Ln represents at least one of Lasy, Gct and Lu, X represents C/ and/or Br, and A represents Ce and/or
or Tb, and X represents a number satisfying 0<x<0.1.

), the general formula described in JP-A No. 55-12145 is (Ba, , M 1
one, X is at least one of Cm5Br and I, A is Eu s T b % Ce % Tm, Dy %
At least one of Pr, HoXNd, Yb and Er, X and y are 0≦X≦0.6 and O≦y≦0.2
represents a number that satisfies the condition. ), the general formula described in JP-A-55-84389 is BeF
X: xCe, yA (where X is at least one of C1, Br, and I, A is InXT7!, G d ,
S is at least one of m and Zr, and X and y
are respectively Q<x≦2×10 and Q<yS5
10'. ), JP-A-55-16
The general formula described in No. 0078 is MLFX-xA:)'Ln (However, MAL is M g 1Ca % B a SS r
% Z At least one of n and Cd, A is B
ed, MgO3Cab,, Sr',, Ba5s ZnO
,,Aj! 203, Y2O2, La20a, In2O
3. SiO2, TiO2, ZrO2, GeO2, SnO
2, Nb2O5, Te20s and T]102, Ln is EuX'rb, Ce, Tm, Dy
%Prs Ho1Nds Ybs Er, Sm and Gd
at least 1 it, and X is CI! ,Br
and I, and X and y are numbers satisfying the conditions of 5×10−piece≦X≦0.5 and O≦y≦0.2, respectively. ) Rare earth element activation 2
Valuable metal fluorohalide phosphor, general formula %) is a halogen. ), JP-A-57-1
General formula (I) described in No. 48285 or [■
], General formula (1) XM3 (PO4)2 ・NX2
: yA general formula (n) Ml (PO4)2 ・
yA (where M and N are each M g % Ca %
S r %Ba
n −, D y % P r % HO % Nd, Yb,
At least one of Er, Sb, Tl, Mn and Sn
Shows no seeds. Further, X and y are numbers that satisfy the condition of 0 and x≦6.0≦y≦1. ), the general formula (
If) or [■] General formula (III) nReX3
・mAXz,: xEu general formula (■) nReX3
・mAX, ;': xEu, yS (wherein, Re is L
at least one of as Gd and YSLu, A represents an alkaline earth metal, and at least one of Bas 5rsCa; x and x' represent at least one of F, Ca, and Br. Also, x and y are lXl0 <x<3XI
Q, lXl0<y<1XlO-' is a number that satisfies the condition, and n/m is 1×108<n/m<
The condition 7 x 10-1 is satisfied. ) There is a fluorophore represented by

As the light beam, as described above, a beam from an LED or a beam from a semiconductor laser is used.

A method of reading a radiation image written on a stimulable phosphor using a semiconductor laser is disclosed in Japanese Patent Laid-Open No. 59-15933, and the semiconductor laser used here is also preferred in the present invention. The wavelength of the semiconductor laser used is preferably 750 to 900 nm, and the beam spot diameter during reading is preferably 50 to 500 μm. In the case of LEDs, the emission wavelength is 750~
The diameter is preferably 900 μm, and the spot diameter is also preferably the same as in the case of a semiconductor laser. When the length of the rotating drum 11 in the circumferential direction is approximately 36 cm, and the scanning line pitch and pixel pitch (pixel pinch in the axial direction) are 100 μm, the number of heads in the case of a semiconductor laser is 2 to 10 due to the arrangement. , and in the case of LEDs, 5 to 10 pieces, 1
It is sufficient that the output per control is 2 to 5 mW or more.

A light beam that satisfies these conditions is particularly preferable for use in the stimulable (stimulable) phosphor described below.

The general formula of e % M g % Ca % S r % B
a % Z n , at least one divalent metal selected from Cd, Cu, and Ni. ML is SC,,Ys
La5CeSPr-.

Nd, Pm, Sn, Eu5Gd, Tb5Dy, Ho.

At least one divalent metal selected from ErlTm, Yb5Lu, Al, Ga, and In. X, X' and X" are at least one halogen selected from F, Cβ, Br and l. A is Eu, 7 b % Ce
1T m −, D y % P r −, Ho, Nd,
Yb.

Ers GdSLu55m, y, Ti, , Na, Ag
.

It is at least one metal selected from Cus and Mg. Also, a is a numerical value in the range of 0≦a<Q,5, b is a numerical value in the range of O≦b<6,5, and C is a numerical value in the range of O≦b<6,5.
<c≦0.2. ) and the like are mentioned.

(Effects of the Invention) As described above, the present invention provides a plurality of reading heads so as to face a stimulable phosphor sheet attached around a rotating drum. By performing sub-scanning by moving the rotating drum in the axial direction, multiple scanning lines are simultaneously scanned by the rotation of the rotating drum, so that both the reading accuracy and reading speed can be satisfied. I can do it. Furthermore, since it is possible to use a storage phosphor material that has a slow response speed for stimulated luminescence, this is advantageous in terms of material selection, and more efficient radiation image detection becomes possible. Furthermore, since a plurality of excitation light sources can be used in parallel, the excitation light intensity is increased overall, the S/N of the read signal is improved, and excellent gradation reading is possible.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional radiation image reading device, FIG. 2 is a side view of a radiation image reading device using a rotating drum according to an embodiment of the present invention, and FIG. 3 is a front view. 4 is a block diagram for making the reading hit constant. 8... Storable phosphor sheet, 11... Rotating drum,
121-12n...reading head, 12a...excitation light irradiation section, 12b...stimulated luminescence detection section, I3...amplifier, 14...sample hold circuit, 15...A/
D converter, E1 to En...scanning line, W...scanning width of one rotation.

Claims (1)

[Claims] (1) In a radiation image reading device that scans a stimulable phosphor sheet with excitation light and photoelectrically converts and reads radiation image information accumulated and recorded on the sheet, the sheet is held around a rotating drum. A plurality of reading heads each consisting of an excitation light irradiation unit and a stimulated luminescence detection unit corresponding to the excitation light irradiation unit are provided so as to face the held sheet, and main scanning by the rotation of the rotating drum and related to each of the reading heads is provided. A radiation image reading device characterized in that sub-scanning is performed by relative movement of the rotary drum in an axial direction so that a plurality of scanning lines are simultaneously scanned by rotation of the rotary drum.