JPH047543A - Radiograph information reading means - Google Patents

Abstract

PURPOSE:To accurately read an image at a high speed by arranging phase conjugate wave generating members at the position where exciting light scattered by a phosphor sheet reaches. CONSTITUTION:A slit plate 50 composed of a phase conjugate wave generation member is arranged covering scanning lines 62 and the incidence surface 26 of an optical guide 28 and a reflecting plate 52 composed of a phase conjugate wave generating member is arranged nearby the projection surface 56 of the optical guide 28. The phase conjugate wave generating members generate light which has the same wave front with incident irradiation light and return through the same optical path by nonlinear effect. Consequently, even when a high-speed read is made, the image can accurately be read.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a radiation image information reading method for reading radiation image information stored and recorded on a stimulable phosphor sheet.

<Prior art> When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, R-rays, electron beams, ultraviolet rays, etc.), it accumulates a part of this radiation energy, and then It is known that when irradiated with excitation light such as visible light, it exhibits stimulated luminescence depending on the accumulated energy, and phosphors that exhibit this property are called stimulable phosphors (stimulable phosphors). ) is called.

Using this stimulable phosphor, radiation image information of a subject such as a human body is stored and recorded on a sheet having a layer of stimulable phosphor (hereinafter referred to as a phosphor sheet), and this phosphor sheet is then exposed to a laser beam. The stimulated luminescence light is generated by scanning two-dimensionally with excitation light such as, and the stimulated luminescence light is read photoelectrically to obtain an image signal. Based on this image signal, a recording material such as a photographic light-sensitive material is processed. The present applicant has proposed a radiation image information recording and reproducing system that reproduces a radiation image of a subject as a visible image on a display device such as a CRT (Japanese Patent Application Laid-Open No.
12429, 56-11395, etc.).

In such a radiation image information recording and reproducing system,
Conventionally, phosphor sheets have been read using various radiation image information reading devices as described below.

In a radiation image information reading device (hereinafter referred to as a reading device), excitation light of a constant intensity emitted from an excitation light source such as a He-Ne laser is reflected in the main scanning direction by an optical deflector such as a galvanometer mirror. The light is deflected and irradiates the phosphor sheet through various optical elements such as an fθ lens.

This phosphor sheet is conveyed in a sub-scanning direction substantially orthogonal to the previous main-scanning direction by a conveying means such as a belt conveyor or a nip roller.

Therefore, the excitation light deflected in the main scanning direction can two-dimensionally scan the entire surface of this phosphor sheet.

Stimulated luminescence light corresponding to the radiation image information accumulated and recorded there is generated from the part of the phosphor sheet that is irradiated with the excitation light.

This stimulated luminescence light is directly incident on the incident surface of the light guide, or is reflected by a condensing mirror arranged opposite to this incident surface and enters the incident surface of the light guide, and is guided by the light guide and excited. It enters a photomultiplier tube through a filter that cuts light in the wavelength range of light, where it is photoelectrically converted into an electrical signal, processed, and then reproduced as a visible image on a CRT or photosensitive material, or as a visible image on a CRT or photosensitive material. recorded and stored on a recording medium.

By the way, in order to read the radiation image information recorded on such a phosphor sheet at high speed, it is necessary to increase the scanning speed of the excitation light, but in this case, the recorded radiation Sufficient stimulated luminescence light cannot be obtained according to the image information, and the quality of the reproduced image deteriorates.

<Problems to be Solved by the Invention> As mentioned above, reading radiation image information recorded on a stimulable phosphor sheet involves exciting the stimulable phosphor by irradiating it with excitation light, and extracting the accumulated radiation. This is done by generating stimulated luminescence light depending on the energy and reading it photoelectrically.

However, when the scanning speed of the excitation light is increased, the irradiation time of the excitation light per unit area becomes shorter, resulting in a decrease in the amount of irradiation of the excitation light, and the amount of radiation increases depending on the accumulated and recorded radiation energy. Reading cannot be performed with a sufficient amount of excitation light to generate stimulated luminescence. Therefore, the reading sensitivity is reduced and the quality of the reproduced image is also reduced.

Moreover, some percentage of the excitation light incident on the phosphor sheet is always scattered by the phosphor sheet and becomes flare, so it is impossible to make the light beam completely act on the excitation of the stimulable phosphor. This is an obstacle to high-efficiency reading during high-speed reading.

Therefore, in order to read the radiographic image information accumulated and recorded on the phosphor sheet at high speed, it is necessary to use a correspondingly high amount of excitation light. By increasing the output of the excitation light source such as a light source, or if the amount of light is insufficient even after increasing the output of the excitation light source, multiple light sources can be used to combine the light beams to excite each one. This was addressed by increasing the amount of light.

However, there are limits to improving the output of the excitation light source.
Another problem is that as the output increases, the cost of the light source also increases. Further, when multiplexing a plurality of light beams, an optical system for this purpose is required, and the cost of the entire apparatus becomes high.

The purpose of the present invention is to solve the problems of the prior art described above, and by improving the utilization efficiency of the excitation light beam,
To provide a radiation image information reading method capable of reading image information at high speed without reducing reading sensitivity and resulting image quality deterioration of reproduced images even when applying a low-output excitation light source. There is a particular thing.

Means for Solving the Problems> In order to achieve the above object, the present invention irradiates scanning excitation light onto a stimulable phosphor sheet on which radiographic image information is accumulated and recorded, thereby extracting information from the stimulable phosphor sheet. A radiation image information reading method for photoelectrically reading the generated stimulated luminescence light, wherein a phase conjugate wave generating member is arranged at least in a part of the position where the excitation light scattered by the stimulable phosphor sheet reaches. The present invention also provides a radiation image information reading method characterized in that the phase conjugate wave generating member substantially returns the excitation light scattered by the stimulable phosphor sheet to the scattering point.

Further, it is preferable to improve the phase conjugate wave generation efficiency by bombing the phase conjugate wave generating member.

<Operation of the Invention> The radiation image information reading method of the present invention having the above-mentioned predetermined configuration uses the phase conjugate wave generating member to generate excitation light scattered by the stimulable phosphor sheet and the light incident on the scattering point. This enables reading with a sufficient amount of excitation light without the need to increase the output of the excitation light source, etc., even when reading at high speed.

A phase conjugate wave generating member is a material that, when irradiated with light, generates light that returns along the same optical path with the same wavefront as the incident light due to a nonlinear effect. The radiation image information reading method of the present invention is capable of generating phase A conjugate wave generating member generates light that travels in the opposite direction on the same optical path with the same wavefront as this scattered light, and returns this light to the scattering point of the scattered excitation light on the stimulable phosphor sheet to excite the stimulable phosphor. It is something that is made to work.

Therefore, according to the radiation image information reading method of the present invention, excitation light acts on reading with higher efficiency than conventional reading methods, and it is possible to excite the stimulable phosphor with a high amount of light.
Even when reading at high speed, it is possible to perform accurate image reading with a sufficient amount of light without significantly increasing the output of the excitation light source compared to conventional methods.

In addition, preferably by bombing the phase conjugate wave generating member by irradiation with light, etc., it is possible to amplify the optical output generated by the phase conjugate wave generating member, and it is possible to amplify the optical output generated by the phase conjugate wave generating member. It is possible to read radiographic image information accurately and efficiently using a certain amount of excitation light.

<Embodiments> Hereinafter, a radiation image information reading method (hereinafter referred to as reading method) according to the present invention will be described in detail based on preferred embodiments shown in the attached drawings.

FIG. 1 shows a schematic perspective view of an example of a radiation image information reading device to which the reading method of the present invention is applied.

The illustrated radiation image information reading device 10 (hereinafter referred to as the reading device 10) is a stimulable phosphor sheet A (hereinafter referred to as the phosphor sheet A) on which radiation image information is stored and recorded.
This phosphor sheet A is scanned two-dimensionally with excitation light.
The radiation image information recorded on the phosphor sheet A is read by generating stimulated luminescence light corresponding to the image information stored and recorded on the phosphor sheet A and photoelectrically measuring the stimulated luminescence light. This reading device 10 applies the reading method of the present invention, and has a slit plate 50 and a reflecting plate 52 made of a phase conjugate wave generating member. The slit plate 50 and the reflection plate 52 will be explained in detail later.

In the illustrated reading device 10, a scanning optical system that deflects excitation light in the main scanning direction indicated by arrow a and scans the phosphor sheet A basically includes a laser light source 12, a galvanometer mirror 14, and an fθ lens 16. It consists of

Excitation light is emitted from a laser light source 12 and enters a galvanometer mirror 14 . The laser light source 12 may be He, depending on the stimulable phosphor applied to the phosphor sheet A.
Various light sources such as a -Ne laser can be used.

The excitation light incident on the galvanometer mirror 14 is reflected and deflected in the main scanning direction shown by arrow a, falls down, enters the fθ lens 16, and converges on the scanning line 62 (see Figure 2). The focus is adjusted so that the phosphor sheet A is irradiated through the slit 54 of the slit plate 50. Note that the optical deflector applied to the present invention is not limited to the galvanometer mirror 20 shown in the illustration.
Any known optical deflector such as a polygon mirror or resonant scanner can be used.

Further, it goes without saying that such an excitation light scanning optical system may be provided with various optical elements such as various surface tilt correction optical systems and mirrors for changing the optical path, as necessary.

On the other hand, the phosphor sheet A is placed on a belt conveyor composed of an endless belt 20 and rollers 22 and 24 that stretch the belt. The phosphor sheet A is moved in the main scanning direction (arrow a direction) by this belt conveyor.
It is conveyed in the sub-scanning direction (the direction indicated by the arrow) which is substantially perpendicular to the .

As a result, the entire surface of the phosphor sheet A is two-dimensionally scanned by the excitation light deflected in the main scanning direction.

Stimulated luminescence light is emitted from the position of the phosphor sheet A that is irradiated with the excitation light in accordance with the radiation image information stored there. This stimulated luminescent light is collected by a focusing optical system and photoelectrically converted into image information.

FIG. 2 shows a schematic side view of the light collection system of the reading device 10.

The stimulated luminescent light emitted from the phosphor sheet A is incident on the incident surface 2.
Reference numeral 6 indicates the excitation light directly on the light guide 28 disposed corresponding to the vicinity of the scanning line, or after being supported by the slit plate 50 and reflected by the condensing mirror 30 disposed corresponding to the vicinity of the scanning line. The light propagates through the light guide 28 through repeated total reflection, passes through the dichroic mirror 58 and exits from the exit surface 56, passes through the filter 60, and the included excitation light is cut off and enters the photomultiplier tube 32. It is incident and photoelectrically converted.

The converted electrical signal is transferred to the image processing device 34 for processing, and is reproduced as a visible image on a CRT 40 or the like, or stored and saved in a storage medium 42 or the like.

Here, when performing high-speed reading, it is necessary to improve the scanning speed of the excitation light. As a result, the amount of light per unit area of the phosphor sheet is insufficient, making it impossible to read images well.In conventional reading devices, the amount of excitation light is increased by improving the output of the laser light source 12. Alternatively, if the desired amount of excitation light cannot be obtained even by improving the output, the insufficient amount of excitation light during high-speed reading can be addressed by combining the light beams using a plurality of laser light sources 12. Ta.

However, there are limits to improving the output of laser light sources.
Further, as mentioned above, the above method has the problem that the cost of the apparatus inevitably increases.

On the other hand, the illustrated reading device 10 applies the reading method of the present invention, and has a scanning line 18 and a light guide 28.
A slit plate 50 made of a phase conjugate wave generating member covers the incident surface 26 of the light guide 28, and a reflecting plate 52 made of a phase conjugate wave generating member near the output surface 56 of the light guide 28.
are arranged. In addition, the light guide 2 below the reflector 52
A dichroic mirror 58 that reflects the excitation light and transmits the stimulated luminescence light is disposed within the light guide 28 at an angle that reflects the excitation light traveling inside the light guide 28 upward.

Phase conjugate wave generating member
0 ptics or less is pco. ) has the property of generating light that returns along the same optical path with the same wavefront as the incident light with which it is irradiated due to a nonlinear effect.

Not all of the excitation light incident on the phosphor sheet A is excited by the stimulable phosphor, and much of it is scattered by the phosphor sheet A, and the scattered excitation light becomes a flare. This obstructs accurate reading. In the reading method of the present invention, by placing a PCO at a position where this scattered excitation light reaches, the POC generates light that travels in the opposite direction on the same optical path with the same wavefront as the incident light. When light enters scattering points of excitation light on the phosphor sheet, it acts on the excitation of the stimulable phosphor. By arranging the plate 52 at the illustrated position, the excitation scattered light and the light having the same wavefront that are incident on both are returned to the scattering point on the phosphor sheet A along the same optical path.

In other words, as shown in FIG. 3, most of the excitation light that has passed through the slit 54 of the slit plate 50 and entered the scanning line 62 does not act on the excitation of the stimulable phosphor, and the surface of the phosphor sheet A It will be scattered in parts.

However, in the illustrated apparatus, a slit plate 50 made of PCO is arranged to surround the scanning line 62 and the incident surface 26 of the light guide, so that a part of the excitation light scattered by the phosphor sheet A is The PCO that enters the slit plate 50 and thereby forms the slit plate 50 generates light having the same wavefront as the incident excitation light that travels in the same optical path in the opposite direction. Therefore, this slit plate 50 (PCO
) is incident on the same position on the scanning line 18 and acts to excite the stimulable phosphor.

On the other hand, the excitation light that is scattered by the phosphor sheet A and enters the light guide 28 from the entrance surface 26 travels upward within the light guide 28 while repeating total reflection, similar to the stimulated luminescence light.
Here, the illustrated light guide 28 includes a dichroic mirror 58 that reflects the excitation light and transmits the stimulated luminescence light, and a reflecting plate 52 made of PCO is disposed above the dichroic mirror 58 ( (see FIG. 2), the excitation light that has progressed is reflected upward by the dichroic mirror 58 and enters the reflection plate 52.

As aforementioned. Since the reflecting plate 52 is made of PCO, this PCo generates light having the same wavefront as the incident excitation light and traveling in the same optical path in the opposite direction. Therefore, this light travels in the opposite direction along the same optical path as the excitation light while repeating total reflection within the light guide 28, exits from the entrance surface 26, enters the same position on the scanning line 18, and enters the stimulable phosphor. Acts on excitation.

Here, the ratio of the intensity of light generated to the excitation light incident on the PCO is r; the excitation light that enters the PCO after being scattered by the phosphor sheet A to the total amount (PO) of the excitation light that has entered the phosphor sheet A. When the amount of is divided by a;, (amount of light generated by pco)/Po=a−r.

Therefore, the total amount of light Ps used to excite the stimulable phosphor is expressed by the sum of the geometric series shown below.

Ps= [1+a-r+ (a-r) 2] +--]
1-a-r Therefore, if a-r=0.1, Ps=1.1 ・P.

If a-r=0.5, Ps=2·P.

If a-r=0.75, Ps=4·P.

becomes. Therefore, even if the output of the excitation light is low, the total amount of light Ps used to excite the stimulable phosphor can be increased.

In the reading method of the present invention, by arranging the pco at the position where the excitation light scattered by the phosphor sheet reaches, for example, the position shown in the illustrated example, it is possible to excite the stimulable phosphor with a high amount of light. Even when reading images at high speed, there is no need to improve the output of the laser light source as in conventional devices.

Examples of pco applicable to the reading method of the present invention include LiNbO3, Bi+2Si2o03 (BSO), B
aTiO3, Sr, -X BaXNb20a (SBN
), gaseous Na, etc. are specifically exemplified.

Although such PCo may be used as it is, it is preferable to perform bombing to amplify the light generated by the incidence of excitation light before use. Various methods can be applied as a bombing method, but
A preferred method is a method of irradiating the same or different types of excitation light from the back side of the surface on which the excitation light is incident, of a member formed from PCO, such as the slit plate 50 or the reflection plate 52. Bumping can also be performed by applying a voltage to a member formed from PCO.

In the reading method of the present invention, by bombing the applied PCO, the amount of light generated by excitation light irradiation can be amplified, and a high amount of light can be accumulated without using a high-power laser light source. This makes it possible to excite the fluorescent phosphor, and even if high-speed image reading is performed, more accurate image information reading and reproduction of the obtained image into a visible image can be performed.

In the illustrated reading device, as shown in FIGS. 2 and 3, the condensing mirror 30 is fixed to a slit plate 50 made of PCO, so that the light is scattered by the phosphor sheet A and placed at this position. In order not to reflect the incident excitation light to an unnecessary position and also to generate light by the PCO with this excitation light, the condenser mirror 3° reflects the stimulated luminescence light and transmits the excitation light. Preferably, it is a dichroic mirror.

In this way, the stimulated luminescent light excited by the excitation light L5 and the light generated from the PCO forming the slit plate 50 and the reflection plate 52 is transmitted from the incident surface 26 to the light guide 2.
8, travels inside the light guide while repeating total reflection, passes through the dichroic mirror 58, and exits at the exit surface 56.
After the excitation light is emitted from the filter 60 and included in the excitation light is cut off by the filter 60, the excitation light enters the photomultiplier tube 32 and is photoelectrically converted.

The electrical signal obtained here is transferred to the image processing device 34, processed, and reproduced as a visible image on a CRT 40, etc.
Alternatively, it is stored and saved in the storage medium 42 or the like.

Although the radiation image information reading method according to the present invention has been described in detail above, the present invention is not limited thereto, and various changes and improvements may be made without departing from the gist of the present invention. Of course.

<Effects of the Invention> As explained in detail above, according to the radiation image information reading method of the present invention, by arranging the phase conjugate wave generating member at the position where the excitation light scattered by the phosphor sheet reaches, The excitation light acts on the reading with higher efficiency than the conventional reading method, and it is possible to excite the stimulable phosphor with a high light intensity, even when reading at a high speed. It is possible to perform accurate image reading using a sufficient amount of light without significantly increasing the output of the light source.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing a radiation image information reading device to which a radiation image information reading method according to the present invention is applied. FIG. 2 is a diagram conceptually showing a condensing system of the radiation image information reading device shown in FIG. 1. FIG. 3 is a diagram conceptually showing the configuration of the radiation image information reading device shown in FIG. 1 near the scanning line. Explanation of symbols 10... Radiation image information reading device, 12... Laser light source, 14... Galvanometer mirror 16... fθ lens, 20... Endless belt, 2224... Roller, 26... Incident surface, 28... Light guide, 30... Condensing mirror 32... Photomultiplier tube, 34... Image processing device, 40... CRT. 42... Image recording medium, 50... Slit plate, 52... Reflection plate, 54... Slit plate, 56... Output surface, 58... Dichroic mirror 60... Filter, 62 ...Scanning line, A...Stormative phosphor sheet, B...Excitation light

Claims (1)

[Claims] (1) A radiation image information reading method that irradiates a stimulable phosphor sheet on which radiation image information is accumulated and recorded with scanning excitation light and photoelectrically reads stimulated luminescence light generated from the stimulable phosphor sheet. A phase conjugate wave generating member is arranged at least in a part of the position where the excitation light scattered by the stimulable phosphor sheet reaches, and the phase conjugate wave generating member causes the excitation light to be scattered by the stimulable phosphor sheet. A radiation image information reading method characterized by substantially returning excitation light to a scattering point.