JPH0522225B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention conveys a sheet-like image recording medium while bringing it into close contact with a conveying means by suction,
The image recording medium is scanned two-dimensionally by the light beam by one-dimensionally deflecting the light beam in a direction substantially perpendicular to the conveyance direction, and the image recorded on the image recording medium by the scanning is The present invention relates to a light beam scanning method for reading and recording an image on the image recording medium.

Certain types of phosphors are exposed to radiation (X-rays, α-rays, β-rays,
When irradiated with γ-rays, ultraviolet rays, etc., a portion of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, the phosphor is exhausted according to the accumulated energy. Phosphors that are known to emit light are called stimulable phosphors.

Using this stimulable phosphor, radiation image information of a human body, etc. is recorded on a sheet having a layer made of stimulable phosphor (hereinafter referred to as a ``stimulable phosphor sheet'' or simply ``sheet''). , this stimulable phosphor sheet is scanned with excitation light such as a laser beam to generate stimulated luminescent light, the resulting stimulated luminescent light is read out photoelectrically to obtain an image signal, and a photograph is taken based on this image signal. The applicant has already proposed a radiation image recording and reproducing system that outputs a visible image to recording materials such as photosensitive materials, CRTs, and the like. (JP-A-55-12429, No. 56-11395, etc.) This system is extremely capable of recording images over an extremely wide radiation exposure range compared to conventional radiographic systems that use silver halide photography. It has practical advantages. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated to emit light due to excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure varies considerably due to various imaging conditions, the amount of emitted light can be read by the photoelectric exchange means by setting the reading gain to an appropriate value and converted into an electrical signal, and this electrical signal can be converted into an electrical signal. By outputting a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure can be obtained.

In addition, according to this system, the radiation image information stored and recorded in the stimulable phosphor is converted into an electrical signal and then subjected to appropriate signal processing. By outputting the image as a visible image on a display device, a very large effect can be obtained in that a radiation image with excellent suitability for observation and interpretation (diagnosis) can be obtained.

In the radiation image recording and reproducing system described above,
A practical and practical method for reading a radiation image from a stimulable phosphor sheet on which a radiation image has been stored and recorded is to scan the stimulable phosphor sheet two-dimensionally with a light beam such as a laser beam, and then One method is to detect the emitted stimulated luminescence light in time series with a photodetector such as a photo detector to obtain an image signal. The two-dimensional scanning of the light beam is usually performed by mechanically transporting the stimulable phosphor sheet in one direction to perform sub-scanning, and by deflecting the light beam one-dimensionally in a direction perpendicular to the sheet transporting direction to perform main scanning. This is done by doing the following. When performing two-dimensional scanning in this manner, an important requirement is to transport the stimulable phosphor sheet in one direction at a stable speed. In other words, while the stimulable phosphor sheet is conveyed at a constant speed in one direction for sub-scanning, when the light beam is scanned in a direction perpendicular to this for main scanning, the sheet is not conveyed at a constant speed with high precision. This causes uneven reading, and the final visible image used for observation and interpretation becomes an image with reduced suitability for observation and interpretation. In addition, stimulable phosphor sheets are usually formed to have flexibility in order to have suitability for transportation, but due to this flexibility, the sheet may lose its flatness. many. If the sheet loses its flatness in this way, there is a risk that the read image will be distorted, or that the sheet will collide with or get caught in the reading optical system during image reading. Therefore, as a mechanism used for conveying a stimulable phosphor sheet, for example, a suction box is placed inside a porous endless belt, and the sheet is placed on this belt. The sheet is brought into close contact with the belt, thereby maintaining the flatness of the sheet while being conveyed and allowing highly accurate, constant speed conveyance without slipping from the belt.

However, when the sheet is conveyed by bringing the sheet into close contact with the conveyance means using a suction box or the like as described above, the suction pressure is always constant from the start of sheet conveyance to the end of sheet conveyance. If it is constant, the following problems arise.

The suction pressure is set to a relatively high suction pressure,
While this ensures that the sheet is held flat on the belt, a problem arises in that the suction blower causes the stimulable phosphor sheet to vibrate, thereby interfering with highly accurate reading. In addition, in order to ensure reliable conveyance, the suction box is divided into multiple pieces, and as the sheet is conveyed, each suction box is sequentially moved so that the sheet being conveyed completely covers at least two suction boxes. A method is adopted in which the sheet is brought into close contact with the conveying means by switching the operation, but in such a case, if the suction pressure is high, vibrations at the time of switching the suction become a particular problem. On the other hand, if the suction pressure is set to a relatively low suction pressure so that vibrations are not generated by the suction blower, a problem arises in that the stimulable phosphor sheet does not start being transported reliably by the transport means.

The above problem occurs not only when reading the stimulable phosphor sheet, but also when reading other sheet-like image recording media such as film, and when scanning the light beam for reading the image. This phenomenon can occur not only in light beam scanning (reading scanning) but also in light beam scanning (recording scanning) for recording images. In other words, sheet-shaped image recording media such as stimulable phosphor sheets and films are brought into close contact with the conveyance means by suction. This generally occurs when the sheet-like image recording medium is read or recorded with a light beam while being conveyed.

The present invention provides a light beam scanning method capable of solving the above-mentioned problems, specifically, a sheet-shaped image recording medium is conveyed in close contact with a conveyance means by a suction, and a light beam is transmitted one-dimensionally in a direction substantially orthogonal to the conveyance direction. A light beam scanning method in which the image recording medium is scanned two-dimensionally with the light beam by deflecting the light beam,
The conveyance of the image recording medium is reliably started, and the vibration of the image recording medium is not generated by the suction blower during reading or recording scanning, that is, when the image recording medium is irradiated with the light beam. Light beam scanning that allows images to be read or recorded.

In the light beam scanning method of the present invention, a sheet-shaped image recording medium is conveyed while being brought into close contact with a conveying means by a suction, and a light beam is one-dimensionally deflected in a direction substantially orthogonal to the conveying direction to convey the image recording medium. in a light beam scanning method in which the image recording medium is two-dimensionally scanned by the light beam, the suction pressure of the suction is set higher than the suction pressure during steady image recording medium conveyance at the start of conveyance of the image recording medium,
After the image recording medium has been conveyed the entire distance and before scanning of the image recording medium by the light beam is started, the suction pressure is reduced to the suction pressure during the steady conveyance of the image recording medium. It is characterized by causing

According to the present invention, the suction pressure at the start of conveyance of the image recording medium is set to a high suction pressure that reliably holds the image recording medium flat on the conveyance means, and at the same time, the suction pressure is set to be high enough to reliably hold the image recording medium flat on the conveyance means, and at the same time, it is possible to set the suction pressure at the beginning of conveyance of the image recording medium to be high enough to reliably hold the image recording medium flat on the conveyance means. Before the image recording medium is checked and scanned by the light beam, the suction pressure can be lowered to a level at which the image recording medium does not vibrate using the suction blower, and highly accurate reading or recording can be performed.

Hereinafter, embodiments in which the present invention is applied to a radiation image reading system using the stimulable phosphor sheet will be described in detail.

FIG. 1 is a schematic diagram showing an example of a radiation image reading system.

The stimulable phosphor sheet 10 on which the radiation image has been stored and recorded is once received by a sheet feeding device 1 that sequentially feeds the sheets one by one. The sheet received by the sheet feeding device is conveyed to the reading device 2 installed on the downstream side in an appropriate cycle. The stimulable phosphor sheet 10 carried into the reading device 2 is once held at the first sheet holding position 20, and then in the pre-reading reading system 21, radiation image information stored and recorded in the stimulable phosphor sheet 10 in advance is read. A so-called "pre-reading" is performed to grasp the stored record information. After this pre-reading, the stimulable phosphor sheet 10 passes through the second sheet holding position and is processed by the amplification factor, recording scale factor, or reproduced image processing based on the accumulated recording information obtained by the pre-reading in the main reading reading system 23. The radiation image used for observation and interpretation is read based on the conditions, so-called "main reading".

Among these two reading operations, pre-reading and main reading, the reading operation of main reading, which particularly requires highly accurate reading, will be described in detail below.

FIG. 2 is a perspective view of a radiation image reading system based on the present invention.

In FIG. 2, the reading system is constructed as follows.

A porous endless belt 201 is stretched between two rotating rollers 202a and 202b.
Two independent suction boxes 203a and 203b are arranged in a portion formed by stretching the endless belt 201.
An excitation light scanning means for scanning the excitation light at the middle part of the endless belt 201, that is, a laser light source 204, a galvanometer mirror, etc. for one-dimensionally deflecting the laser light 205 emitted from the laser light source 204. A light deflector 206 is provided. It has a linear incident surface that faces the scanning line obtained by deflecting the laser beam 205 with an optical deflector 206, and the light incident from this incident surface is totally internally reflected to the exit end. A light guide sheet 207 that transmits light to
is provided. A photodetector 208 such as a photodetector is brought into close contact with the exit end of the light-guiding sheet 207. This light guide sheet 207 is made by processing a transparent thermoplastic resin sheet such as acrylic resin, and the preferred shape, material, etc. of this light guide sheet are disclosed in Japanese Patent Application Laid-Open No. 55-87970,
It is disclosed in Publication No. 56-11397. In addition,
A filter is attached to the light-receiving surface of the photodetector 208, which transmits only light in the wavelength range of the stimulated luminescence light and cuts out light in the wavelength range of the excitation light, and detects only the stimulated luminescence light. It's getting wet. On the sheet receiving side of the conveyor belt 201, there are a carry-in belt 209 for causing the conveyor belt 201 to receive sheets, a pair of nip rolls 211, and a first position detection sensor 2 consisting of a photosensor and a light emitting diode.
12a and a second position detection sensor 212b are provided. Further, a discharge belt 210 is provided on the sheet discharge side of the conveyance belt 201.

The image reading operation in the radiation image reading system configured in this way is shown in FIGS. 2 and 3A to 3.
This will be explained with reference to Figure F.

As shown in FIG. 3A, the stimulable phosphor sheet 10 is carried into the reading system by the carrying belt 209.
The leading end of the sheet is sent out by the rotating nip roll 211 to a location where the first position detection sensor 212 is located, as shown in FIG. 3B. Here, the leading edge of the sheet is connected to the first position detection sensor 21.
When detected by 2a, the rotation of the nip roll 211 is stopped, and the conveyance of the sheet 10 is temporarily stopped. Next, when preparations for image reading are completed on the downstream side, conveyance of the sheet 10 by the nip roll 211 is started again. A second position detection sensor 212b is installed at a position where the rotational speed of the nip roll 211 is stable and the conveyance speed of the sheet is constant, and this sensor 212b detects the leading edge of the sheet 10 as shown in FIG. 3C. By rotating the nip roll 211 for a certain period of time from the time when is detected, the leading edge of the sheet is positioned a predetermined distance away from the location where the excitation light is scanned, as shown in FIG. 3D. In this state, suction of the suction box 203a is started, air is sucked through the opening of the porous endless belt 201, and the sheet 10 is brought into close contact with the porous endless belt 201. At this time, the porous endless belt 201 is rotated by rotating rollers 202a and 202a.
Since the sheet is being moved at a constant speed by 02b, conveyance of the sheet is started. The suction pressure at the start of conveyance of the sheet is set to be high enough to ensure the start of conveyance. After the sheet 10 is conveyed in this state and the upper part of the suction box 203a is completely covered with the sheet 10, the laser light source 203a is
When the photodiode 214 detects that the leading end of the sheet 10 has been irradiated with the laser beam 205 of No. 04, the suction pressure of the suction box 203a is lowered, and the stimulable phosphor sheet 10 is It is made so that it does not vibrate. The specific value of the suction pressure depends on the surface condition, dimensions, etc. of the sheet to be conveyed, but as a rough guide, for example, when conveying stimulable phosphor sheets in four, six, or half pieces, The following values are preferred:

The higher pressure value at the start of conveyance is 150mm.
_H2O ~ _2000mmH2O , 450mm considering economy
The lower pressure value during steady conveyance is preferably about 50 mm H ₂ O to 200 mm H ₂ O, preferably about ₁₅₀ mm H ₂ O in consideration of stability. As shown in FIG. 3E, the stimulable phosphor sheet 10 is brought into close contact with the conveyor belt 201 by the suction box 203a and sub-scanned by being conveyed, and the laser beam 205 emitted from the laser light source 204 is applied to the stimulable phosphor sheet 10. The laser beam 205 enters the sheet 10 while being deflected one-dimensionally by the optical deflector 206, and the sheet 10 is scanned two-dimensionally by the laser beam 205. In this way, when scanned by the laser beam 205, the stimulable phosphor sheet 10 emits stimulated luminescence light in an amount proportional to the radiation energy stored and recorded.
This emitted light enters the light guide sheet 207 from the incident surface, and is totally reflected inside the light guide sheet 207.
and reaches the photodetector 208. Since the light receiving surface of the detector 208 is provided with a filter as described above, only stimulated luminescence light is detected. In the case of pre-reading, the output of the photodetector 208 is used to set the amplification factor, recording scale factor, or reproduction image processing conditions for main reading. In addition, in the case of actual reading, it is used to reproduce the radiographic image used for observation interpretation. As shown in FIG. 3F, the seat 10 is placed in the suction box 203.
When the top of b is completely covered, suction box 20
3a is set to 0, the suction box 203b starts suctioning, and the sheet 1
Sheet 1 until the trailing edge of Sheet 0 is scanned by the excitation light.
The sheet 10 is brought into close contact with the conveyor belt 201, and the flatness of the sheet 10 is maintained while highly accurate and constant speed conveyance is performed. As shown in FIG. 1, the sheet 10 on which such reading operation has been completed is conveyed to the second sheet holding position 22 if the above-mentioned reading operation is pre-reading, and is conveyed to the third sheet holding position 22 if the reading operation is main reading. 24. When reading of a certain sheet is completed as described above, reading of the next sheet is started. The timing for carrying this sheet into the reading system is such that when it is detected that the trailing edge of the sheet has passed the reference position of the reading system, the sheet located at the upstream sheet holding position starts to be carried into the reading system. However, when changing the sheet conveyance speed in the reading system in order to keep the time required for reading constant depending on the sheet size, it is necessary to By changing the time it takes to start loading the sheet depending on the size of the sheet being read, the reading cycle time in the reading device can be shortened.

If the sheet located in the third sheet holding position 24 after the main reading is pre-reading by the pre-reading reading system 21, the sheet is held in the third sheet holding position 24 until the pre-reading is completed. In synchronization with the completion of pre-reading, the shutter 25 provided in the reading device 2 is released for a short time to eject the sheet from the reading device 2, and the sheet is carried into the noise canceling device 3. In this way, if the shutter 25 of the reading device 2 is not released while pre-reading is being performed, the erasing light will enter the reading device 2 from the noise canceling device 3 installed downstream of the reading device 2. Prevent leakage from interfering with pre-reading. The sheet 10 carried into the noise erasing device 3 is irradiated with light by an erasing light source 31 consisting of a plurality of fluorescent lamps arranged in parallel, thereby erasing the residual accumulated radiation energy in the stimulable phosphor sheet. After the radiation energy has been erased, the stimulable phosphor sheet 10 is sorted by sheet size or sheet type in a sorter 32 provided in the noise canceling device 3. Store the sheets in the tray. In this sorting of sheets, for example, sheet sizes are often set in advance by each hospital etc. where imaging is performed, so it is desirable to be able to arbitrarily set the sheet size or sheet type of the sheets to be sorted. For this purpose, for example, as shown in FIG. 1, a tray 321a for receiving sheets of two different sizes,
... 321f is a support stand 322 that supports the tray.
a, . . . 322f, and furthermore, it can be carried out by instructing by an appropriate switch means what shape or type of sheet is to be stored in which tray stored in which support base, and furthermore, this can be carried out by If there are two trays that receive sheets of the same sheet size or type, it is more preferable to send the sheets to the other tray when one tray is full. It would be very convenient in practice to be able to arbitrarily set the size or type of sheets to be sorted without changing the design of the sorter. Note that sheet types include, for example, sheets that were exposed to a large amount of radiation at the time of imaging and cannot be erased with the normal set erasing time, and sheets that cannot be erased with the normal erase time are stored in the same tray. It is convenient for handling if the sheets stored in this tray are further irradiated with light for erasing radiation energy.
In this case, the light irradiation is carried out by inserting the sheet 10 into the sheet feeding device 1 of the radiation image reading system, and transporting the sheet 10 into the noise canceling device 3 without reading and scanning with the reading device 2. The sheet 10 is removed from the noise erasing light source 3 of the noise erasing device 3 by controlling the control system of
This can be done by installing it under the noise canceling device 1, or by directly inserting it into a noise canceling device provided separately.

In the above embodiment, the stimulable phosphor sheet is conveyed in close contact with the conveying means by suction, and the sheet is read and scanned with a light beam. Light beam scanning is not limited to reading scanning, and recording by light beam scanning is not limited to reading other sheet-like image recording media such as film or reading images by light beam scanning. It is also applicable to cases where

As described above in detail, according to the present invention, the sheet-like image recording medium is reliably started to be conveyed by the conveying means for sub-scanning, and the sheet-like image recording medium is moved by the suction blower during light beam scanning. Since there is no vibration, highly accurate image reading or recording can be performed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a radiation image reading system, FIG. 2 is a perspective view of a radiation image reading system based on the present invention, and FIGS. 3A to 3F are radiation images shown in FIG. 2. FIG. 3 is a diagram illustrating an image reading operation in an image reading system. 1...Sheet feeding device, 2...Reading device, 3...
...Noise canceling device, 10...Stormable phosphor sheet, 20...First sheet holding position, 21...Reading system for prefetching, 22...Second sheet holding position,
23... Reading system for main reading, 24... Third sheet holding position, 25... Shutter, 31... Erasing light source, 32... Sorter, 201... Porous endless belt, 202a, 202b... Rotating roller,
203a, 203b...Suction box, 2
04... Laser light source, 205... Laser light, 20
6... Light deflector, 207... Light guide sheet, 20
8...Photodetector, 209...Carrying belt, 210
...Export belt, 211...Nitspro roll, 21
2a...first position detection sensor, 212b...
A second position detection sensor.

Claims (1)

[Claims] A sheet-shaped image recording medium is conveyed while being brought into close contact with a conveyance means by suction, and a light beam is one-dimensionally deflected in a direction substantially orthogonal to the conveyance direction, so that the image recording medium is two-dimensionally moved by the light beam. In the scanning light beam scanning method, the suction pressure of the suction is set higher than the suction pressure during normal image recording medium conveyance at the start of conveyance of the image recording medium, and after the image recording medium has been conveyed a certain distance. A light beam scanning method characterized in that the suction pressure is lowered to the suction pressure during the steady conveyance of the image recording medium before scanning of the image recording medium by the light beam is started.