JPS63261341A - Radiation image information reading device - Google Patents

Abstract

PURPOSE:To maintain the quantity of emitted light of respective main scanning lines at a specified level and to prevent the uneven density of a reproduced image regardless of the pitches of the main scanning lines by detecting the uneven conveying speeds of a sub-scanning means to cause the nonuniform pitches of the main scanning lines and increasing or decreasing the quantity of stimulating light according to the conveying speeds. CONSTITUTION:For example, the signal based on the conveying speed of the sub- scanning means detected by a speed detector 10 such as encoder connected to a motor 7A is sent to a modulator driving circuit 4 which drives a modulator 3 to execute the modulation to change the quantity of the stimulating light 2 according to the conveying speeds of an accumulation type fluorescent material sheet 6. More specifically, the circuit 4 drives the modulator 3 so as to relatively increase the quantity of the stimulating light 2 when the signal S4 indicates that the conveying speed of the sub-scanning means is lower than a reference speed. Said circuit drives the modulator 3 so as to relatively decrease the quantity of the stimulating light 2 when the signal S4 indicates that the conveying speed of the sub-scanning means is higher than the reference speed. The uneven density of the image to be finally obtd. is thereby minimized even if there are the uneven pitches of the main scanning lines.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a radiation image information reading device that reads radiation image information stored and recorded on a stimulable phosphor sheet. The present invention relates to a radiation image information reading device that can perform reading without causing unevenness.

(Conventional technology) Certain phosphors are exposed to radiation (X-rays, α-rays, β-rays.

When irradiated with γ-rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, the phosphor changes depending on the accumulated energy. is known to exhibit stimulated luminescence, and phosphors exhibiting this property are called stimulable phosphors (stimulable phosphors).

Using this stimulable phosphor, radiographic image information of a subject such as a human body is stored and recorded on a -H stimulable phosphor sheet, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam for photostimulation. A radiographic image information recording and reproducing system has been proposed which generates a radiographic image of a subject that is suitable for diagnosis by emitting light, reading the generated photostimulated light in a charging manner to generate an image signal, and processing this image signal. There is. (For example, JP-A-55-124
29 No. 1 No. 56-11395, No. 55-163472
No. 56-104645, No. 55-116340, etc.) The radiation 1 image information reading device that reads radiation image information in the above system includes a main scanning means for scanning excitation light on a stimulable phosphor sheet, a storage sub-scanning means for conveying the phosphor sheet in a direction substantially perpendicular to the scanning direction of the excitation light;
J3 and a photoelectric reading means for photoelectrically detecting the stimulated luminescent light emitted from the scanning position of the excitation light two-dimensionally scanning the stimulable phosphor sheet. The image information read by this reading device is transferred onto a recording sheet conveyed in the sub-scanning direction by the reading device)
The image is recorded by main-scanning a light beam modulated based on the image signal thus obtained, and is reproduced as a pA image.

(Problems to be Solved by the Invention) In the above system, in order for the finally obtained reproduced image to have good image quality with no unevenness in arx, it is necessary to It is necessary that the pitch is always constant.

However, in reality, the conveyance speed of the stimulable phosphor sheet by the sub-scanning means becomes uneven due to causes such as disturbances, vibrations, or eccentricity of the motor of the sub-scanning means, and as a result, the pitch of the main scanning lines becomes uneven. This may cause some inconvenience.

That is, as shown in FIG. 3(a), the excitation light main scans in the direction of arrow X over the stimulable phosphor sheet which is sub-scanned in the direction of arrow Y to form a main scanning line of width W1. When a predetermined conveyance speed is such that adjacent main scanning lines overlap by a width W2, if the sub-scanning speed becomes slower than the predetermined speed, the main scanning lines overlap as shown in FIG. 3(b). The overlapping width W2' of the main scanning lines becomes larger than the width W2, and conversely, as the sub-scanning speed increases, the overlapping width of the main scanning lines becomes smaller than the width W2 or disappears completely as shown in FIG. 3(C). When the overlapping width of the main scanning lines becomes large, each main scanning line will excite more of the part that has already been excited by the previous main scanning line, so the amount of stimulated luminescence light obtained will decrease. As the overlapping width of the scanning lines becomes smaller, the amount of stimulated luminescence light obtained in each main scan increases. therefore,
In the recording device described above, if recording is always performed at a constant pitch, the sub-scanning speed in the reading device fluctuates as described above, causing unevenness in the pitch of the main scanning lines.
When the light amount level of the stimulated luminescence light generated by 1q changes, the reproduced image becomes distorted and its density becomes uneven, and there is a problem in that the density unevenness is particularly noticeable and tends to lead to deterioration of image quality. Fluctuations in the sub-scanning speed at the reading position of 5A and 1III! on the reproduced image. The relationship between the fluctuations of 1 is shown in FIG.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a radiation single image information reading device that can suppress the occurrence of density unevenness on a reproduced image even if the sub-scanning speed varies. The purpose is to

(Means for Solving the Problems) The radiation image information reading device of the present invention includes a speed detector that detects the conveyance speed (sub-scanning speed) of the stimulable phosphor sheet, and a , characterized by comprising a light amount adjustment means for adjusting the light amount of the excitation light so that the light amount of the excitation light when the speed is low is greater than when the -12 speed is high. It is.

(Function) In a radiation image information reading device, even if the radiation energy accumulated in the stimulable phosphor sheet is constant, if the amount of excitation light increases, the stimulated luminescence emitted from the stimulable phosphor sheet increases. The amount of light increases. Therefore, in the above device, when the sub-scanning speed is slow and the light level of the obtained stimulated luminescence light is low, the sub-scanning speed is increased by increasing the light amount of excitation light compared to when the sub-scanning speed is high. Fluctuations in the light amount level of stimulated luminescence light due to speed can be offset, and density unevenness can be prevented from occurring on the reproduced image.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an outline of a radiation image information reading device according to an embodiment of the present invention.

The excitation light 2 emitted from the Rede light source 1 passes through an optical modulator 3, which will be described later, and then enters a galvanometer mirror 5, where it is deflected by an anti-tA, and is stored below the galvanometer mirror 5. A main scan is performed on the fluorescent phosphor sheet 6 in the direction of the arrow X. The stimulable phosphor sheet 6 is attracted onto an endless belt device 7, which is a sub-scanning means, and is driven by a motor 7A.
The stimulable phosphor sheet 6
Two-dimensional scanning is performed by the excitation light 2 over the entire surface.

According to the excitation and scanning by the light 2, the part of the stimulable phosphor sheet irradiated with the excitation light 2 emits stimulated light according to the image information accumulated and recorded there, and this emitted light is transmitted to the stimulable phosphor sheet. The light enters the light guide 8 from the incident end surface 8a of a transparent light guide 8, which has an incident end surface 8a formed in parallel to the main scanning line in the vicinity. The light guide 8 has a flat front end 8b located near the stimulable phosphor sheet 6, and gradually becomes cylindrical toward the rear end, and has a substantially cylindrical shape at the rear end 8C. Since the photomultiplier 9 is connected to the photomultiplier 9 provided on the exit end surface, the stimulated emitted light entering from the entrance end surface 8a is transmitted to the rear end portion 8.
The emitted light is collected at C and transmitted to the photomultiplier 9 via a filter (V not shown) that selectively transmits the stimulated luminescent light. In the illustrated apparatus, the photomultiplier and the light guide constitute a light iRi extraction means. In the photomultiplier 9, the stimulated luminescent light is converted into an electrical signal, and the obtained electrical signal is sent to the image information reading circuit 15 for processing and then output to the image recording device.

In the above reading device, if the stimulable phosphor sheet 6 is conveyed correctly at a constant speed by the endless belt device 7, the pitch of the main scanning lines formed by the excitation light 2 will be constant, and finally IIl The density level of the reproduced image is uniform over the entire surface, but the motor 7A
If the conveyance speed fluctuates due to eccentricity or vibration, and a difference occurs in the pitch of the main scanning lines, there is an inconvenience that density unevenness occurs in the reproduced image. Therefore, in this embodiment, as an example, a speed detector 10 such as an encoder is installed on the motor 7A.
A signal based on the conveyance speed of the DJ scanning means detected by the speed detector 10 is sent to the modulator drive circuit 4 that drives the modulator 3, and a signal based on the conveyance speed of the stimulable phosphor sheet 6 is sent to the modulator drive circuit 4 that drives the modulator 3. Modulation is performed to change the amount of excitation light 2.

Hereinafter, the control of the amount of excitation light will be explained with reference to FIG.

The speed detector 10 generates a pulse signal S1 corresponding to the actual conveyance speed of the endless belt device 7, while the reference clock generating means 11 generates a pulse signal S1 corresponding to the reference speed which is a predetermined conveyance speed of the stimulable phosphor sheet. A pulse signal S2 with a constant interval is generated. These signals 81 and 82 are added together and sent to the deviation counter 12, and the deviation counter 12 calculates the deviation between the two signals during one main scan of the excitation light 2, i.e. - main scanning time. A signal S3 corresponding to the difference between the actual conveyance speed of the sub-scanning means and the reference speed is output. The output signal S3 is converted into an analog signal by the D/Δ converter 13, and then the gain is adjusted by the gain adjustment means 14. The control signal S4 finally obtained in this manner is input to the modulator drive circuit 4. When the signal S4 indicates that the conveyance speed of the sub-scanning means is slower than the reference speed, the modulator drive circuit 4 controls the modulator 3 to perform modulation to relatively increase the amount of excitation light. When the signal 8S4 indicates that the conveyance speed of the sub-scanning means is faster than the reference speed, the modulator 3 is driven so as to perform modulation to relatively reduce the distance between the excitation lights. Note that when the laser light source 1 is a semiconductor laser capable of analog direct modulation, the driving current of the semiconductor laser may be changed based on the control signal S4 to perform modulation corresponding to the above-mentioned uneven conveyance speed. good. In any case, the increase or decrease in the light intensity of the light beam corresponds to the width of each main scanning line, and is set in advance so that the light emission level for each main scanning line is constant. ing.

In this way, the transport speed for the stimulable phosphor sheet 6 within -1 scanning time is detected, and when the transport speed is low, the amount of excitation light is relatively large, and when the transport speed is high, the amount of excitation light is relatively large. If the excitation light is modulated for each main scan so that the amount of excitation light is relatively small, even if the bitches of the main scan line are uneven due to uneven conveyance speed, the final result is (
It is possible to minimize the turbidity unevenness of the image.

Note that a) various means can be used as the light amount adjusting means in addition to the one using the optical modulator as described above. For example, an optical wedge whose optical density gradually changes depending on the position is installed on the optical path of the excitation light, and this optical wedge is moved in accordance with the output of a speed detector. You may also make adjustments.

<Effects of the Invention> As explained above, according to the radiation image information reading device of the present invention, unevenness in the conveying speed of the sub-scanning means that makes the pitch of the main scanning line non-uniform is detected, and excitation is performed according to the conveying speed. By increasing or decreasing the amount of light, the level of light emitted from each main scanning line can be kept constant regardless of the pitch of the main scanning lines. Therefore, the reproduced image obtained based on the above-mentioned emitted light has good image quality without unevenness in IA degree.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an overview of a radiation image information reading device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a mechanism for controlling the amount of excitation light, and FIG. 3 (a>, (b), (c) is a schematic diagram showing the state of the main scanning line depending on the sub-scanning speed, and FIG. 4 is a graph showing the relationship between the sub-scanning speed and the reproduced image density. 1... Rade light source 2... Excitation light 3 ... Optical deflector 5 ... Galvanometer mirror 6 ... Stimulative phosphor sheet 7 ... Endless belt device 9 ... Photo multiplier 10 ... Speed detector 10 Ω 1988 May 26th

Claims (1)

[Scope of Claims] Main scanning means for one-dimensionally scanning excitation light on a stimulable phosphor sheet on which radiographic image information has been accumulated and recorded, the stimulable phosphor sheet being arranged in a main scanning direction of the excitation light. In a radiation image information reading device comprising a sub-scanning means for conveying in a vertical direction, and a photoelectric reading means for photoelectrically detecting stimulated luminescent light carrying the radiation image information emitted from the main scanning position of the excitation light. , a speed detector that detects the speed of the conveyance; and based on the output of the speed detector, the amount of the excitation light when the speed is low is greater than when the speed is high. A radiation image information reading device characterized by comprising a light amount adjusting means for adjusting the amount of excitation light.