JPS62213363A - Picture information reader - Google Patents

Abstract

PURPOSE:To improve the photodetection efficiency of reflected light or the like from a storage medium by allowing a light waveguide element arranged between a photodetector and the recording medium to make a read light incident on the recording medium to bring the photodetector sufficiently close to the recording medium. CONSTITUTION:The photodetector 20 is provided in face with a rotary drum 10 storing a storage fluorescent sheet 13 on which radiation picture information is stored and recorded and the light waveguide element 25 is fixed to a photodetection face 20a of the detector 20. The element 25 is arranged in a way that a light incident grating coupler 28 is unlocked from the detector 20, receives stimulated light 24 and a light radiation light condensing grating coupler 29 is opposed to the circumferential surface of the drum 10. Then the element 25 is made very thin as 1mm or below including the thickness of a disc 26 and the distance between the photodetection face 20a of the detector 20 and the sheet 13 is set sufficiently smaller even taking the optical path length for focusing the light 24 into consideration. Thus, the detector 20 is brought very close to the sheet 13 and the photodetection efficiency of the reflected light or the like from the sheet 13 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to an image information reading device, and more particularly, to scanning a reading light two-dimensionally over a recording medium on which image information is recorded, thereby scanning the recording medium. The present invention relates to an image information reading device configured to read image information by detecting emitted light or reflected light emitted from an image.

(Technical Background and Prior Art of the Invention) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a portion of this radiation energy is emitted by fluorescent light. It is known that when this phosphor is accumulated in the body and is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy; The fluorophore is called a storage fluorophore (stimulable fluorophore).

Using this stimulable phosphor, radiation image information of a subject such as a human body is temporarily recorded on a stimulable phosphor sheet, and the stimulable phosphor sheet is irradiated with excitation light to produce stimulated luminescence. The resulting stimulated luminescent light is photoelectrically read by a photodetector to obtain an image signal, and based on this image signal, a radiation image of the subject is displayed on a recording material such as a photographic light-sensitive material or a display device such as a CRT. The applicant has already proposed a radiation image information recording and reproducing system that outputs a visible image. (
JP-A-55-12429, JP-A-56-11395, etc. ) This system has the practical advantage of recording images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography.

In other words, in stimulable phosphors, it is recognized that the amount of emitted light that is stimulated and emitted by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range, and therefore, depending on various imaging conditions, radiation exposure Even if the amount fluctuates considerably, the amount of stimulated luminescent light emitted from the stimulable phosphor sheet is read by a photoelectric conversion means by setting the reading gain to an appropriate value and converted into an electrical signal. By outputting a radiation image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT using an electric signal, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained.

In the above-mentioned radiation image information recording and reproducing system, reading of stimulated luminescence light is roughly divided into two methods. In other words, in one method, pixel division is performed by excitation light scanning, and the detection of stimulated luminescence light is performed by a light receiving element (for example, a photomultiplier tube, etc.) having a wide light receiving surface. (for example, two-dimensional solid-state image sensors, semiconductor line sensors, etc.)
A time-series image signal is formed using an electric circuit.

The former method is superior in terms of sensitivity and signal-to-noise ratio of read signals compared to the latter method, which uses two-dimensional solid-state image sensors, semiconductor line sensors, etc., but Since the stimulated emission light is non-directional and has a low level, when implementing the former method, it is important to make the acceptance solid angle of the stimulated emission light as large as possible and collect as much light as possible to increase the light collection efficiency. It becomes necessary. If this light collection efficiency is low, the S/N ratio of the read signal will decrease, and in the worst case, it will become impossible to read the image information.

Therefore, as mentioned above, special light condensing bodies have been widely used in order to improve the light condensing efficiency of stimulated luminescence light as described above. This condenser is, for example, JP-A-56-12601, JP-A-56-12601;
As shown in No. 11396, etc., it is made of acrylic resin or the like, and has a flat light incident end surface extending along the excitation light main scanning line on the stimulable phosphor sheet, and a light receiving surface of a photodetector such as a photomultiplier tube. The light emitting end face is coupled to the light emitting end face.

If such a light collector is used, the efficiency of collecting stimulated luminescence light can be increased by arranging its light incident end face close to the stimulable phosphor sheet. However, the cost of such a complicatedly shaped light condensing body is high.

As a radiation image information reading device that can improve the condensing efficiency of stimulated luminescence light without using this kind of condenser, for example, Japanese Patent Laid-Open No. 5
The one shown in No. 5-48674 is known. This radiation image information reading device arranges a photodetector such as a photomultiplier tube close to a stimulable phosphor sheet without using a lens system, and also connects the photodetector and the stimulable phosphor sheet. A reflective optical element such as a prism is disposed between them, and the excitation light traveling towards the gap between the reflective optical element and the photodetector is reflected by the reflective optical element and onto the stimulable phosphor sheet. It is designed so that it is incident. With this configuration, even if the photodetector is placed close to the stimulable phosphor sheet, it is possible to make the excitation light incident on the stimulable phosphor sheet.

However, even in the above-mentioned radiation image information reading device, in order to arrange reflective optical elements such as prisms, and to enable the excitation light beam to travel, which actually has a considerable beam diameter, the photodetector and storage It is necessary to provide a certain amount of space between the photodetector and the phosphor sheet, which makes it difficult to bring the photodetector sufficiently close to the stimulable phosphor sheet.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and it is possible to place a photodetector sufficiently close to a recording medium such as a stimulable phosphor sheet, thereby making it possible to detect light from the recording medium. It is an object of the present invention to provide an image information reading device that can greatly increase the efficiency of receiving emitted stimulated luminescence light and reflected light.

(Structure of the Invention) As described above, the image information reading device of the present invention makes the reading light from the reading light source two-dimensionally scan the recording medium on which image information is recorded, and the reading light scans the recording medium by scanning the reading light. In an image information reading device that photoelectrically detects luminescent light such as stimulated luminescent light or reflected light emitted from a source and reads image information carried by this light, a photodetector is used to detect the luminescent light or reflected light through a lens system. An optical waveguide element is placed between the photodetector and the recording medium in place of the aforementioned prism, and the reading light is transmitted through the optical waveguide element. is introduced between a photodetector and a recording medium, and is emitted from the element to be incident on the recording medium. The above-mentioned optical waveguide element has an optical waveguide formed on a substrate, and a light incident part and a condensing grating coupler for light output are provided on the surface of the optical waveguide, and the read light from the read light source is converted into the above-mentioned light. The reading light is taken into the optical waveguide from the incident part, and is arranged so that the reading light that has traveled through the optical waveguide is outputted from the light-emitting condensing grating coupler and focused on the recording medium.

As is well known, the optical waveguide described above can be formed extremely thin, so that the photodetector can be placed sufficiently close to the recording medium.

Note that the optical waveguide element placed at the position described above will block part of the emitted light or reflected light emitted from the recording medium, so in order to increase the efficiency of receiving this light, a photodetector It is preferable to form the area as small as possible compared to the light receiving surface.

(Embodiments) Hereinafter, the present invention will be described in detail based on actual file embodiments shown in the drawings.

1 and 2 are each part of the present invention 7I! 2 shows a planar shape and a side surface shape of an image information reading device according to an embodiment. The rotating drum 10 is rotatably supported around a shaft 11, and is rotated by a main scanning motor 12 in the direction of the arrow. As an example, the apparatus of this embodiment is formed to read radiation image information from a stimulable phosphor sheet, and the stimulable phosphor sheet 13 to be read is placed on the circumferential surface of the rotating drum 10. Retained. The stimulable phosphor sheet 13 has the structure described above, and radiographic image information is accumulated and recorded by, for example, irradiating radiation that has passed through the subject.

Note that this stimulable phosphor sheet 13 is formed using a flexible support, and is bendable in order to be held on the surface of the rotating drum 10 as described above.

A guide rod 14 and a screw rod 15 are arranged near the circumferential surface of the rotating drum 10 in parallel with the shaft 11, respectively. A reading head 16 is slidably held on the guide rod 14 via a sliding portion 17 . The reading head 16 also has a female threaded portion 18 screwed onto the screw rod 15, and is capable of being screwed forward and backward with respect to the screw rod 15. The screw rod 15 is adapted to be rotated by a sub-scanning motor 19, and when the screw rod 15 is rotated, the reading head 16 is moved along the screw rod 15 and the guide rod 14 in the direction of the arrow Y. Moving.

A photodetector 20 is fixed to the lower surface of the reading head 16, that is, the surface on the rotating drum 10 side, with the light receiving surface 20a facing the rotating drum 10 side. The photodetector 20 is preferably one that can detect weak light and has a high S/N ratio, such as a photomultiplier tube, a channel plate for photoelectron amplification, or the like. Further, a reading light source 23 consisting of a laser light source 21 such as a semiconductor laser and a collimator lens 22 is fixed to the reading head 16 . A laser beam (divergent beam) emitted from a laser light source 21 is made into a parallel beam by a collimator lens 22, and this parallel beam is used as excitation light 24 to be applied to the rotating drum 10.
It is designed to be ejected to the side. Note that the reading light source 23 is fixed to the reading head 16 in such a manner that its beam emitting axis is oblique to the light receiving axis of the photodetector 20.

An optical waveguide element 25 is fixed to the light receiving surface 20a of the photodetector 20. This optical waveguide element 25 is connected to the light receiving surface 2.
It consists of a substrate 26 directly attached to the substrate 26 and an optical waveguide 21 formed on the substrate 26. On the surface of the optical waveguide 21, a grating coupler 28 for light incidence and a concentrator for light output are arranged at a distance from each other. An optical grating coupler 29 is formed. In this embodiment, as an example, an LtNbO3 wafer is used as the substrate 26, and the optical waveguide 21 is formed by providing a Ti diffusion film on the surface of this wafer. Note that other crystalline substrates made of sapphire, Si, etc. may also be used as the substrate 26. Furthermore, the optical waveguide 21 is not limited to the Ti diffusion described above, but may also be formed by sputtering or vapor depositing other materials on the substrate 26. Regarding optical waveguides, for example, Titamir (T
, Tam1 r)li [Intearated Optics J
(Topics in Applied Physics (Top
ics in Applied Physics
) Vol. 7) Springer Verlag (Sprinoe)
r-Verlao) (1975): Nishihara, Haruna, and Suhara, co-authored, ``Optical Integrated Circuits'' published by J Ohmsha (1985), etc., have detailed descriptions, and in the present invention, these known optical waveguides are used as the optical waveguide 27. Either can be used.

The light incident grating coupler 28 is a so-called linear grating coupler in which a plurality of linear grid patterns are arranged in parallel in the left-right direction in FIG. On the other hand, the condensing grating coupler 29 for light emission has a plurality of quadratic grid patterns arranged side by side in the waveguide direction of the optical waveguide 21, that is, in the left-right direction in FIG. 2, and the curvature of each pattern and the pitch between the patterns are changed. It is something that can be done. Note that such a condensing grating coupler is described in detail in, for example, IEICE technical research report 0QC83-8, 4, pages 47 to 54.

In the optical waveguide element 25, the grating coupler 28 for light incidence comes off from the photodetector 20 and receives the excitation light 24,
A light-emitting condensing grating coupler 29 is arranged to face the circumferential surface of the rotating drum 10.

Further, the photodetector 20 has a light receiving surface 20a that is connected to the rotating drum 1.
0 is placed sufficiently close to the stimulable phosphor sheet 13 on top of the stimulable phosphor sheet 13.

Hereinafter, the operation and effects of the image information reading device of this embodiment having the above configuration will be explained. Storable phosphor sheet 1
3, the rotary drum 10 holding the sheet 13 is rotated by the soil scanning motor 12 as described above, and at the same time, the sub-scanning motor 13 is driven in synchronization with the main scanning motor 12. The screw rod 15 is rotated. Also, the laser light source 21 is driven,
Excitation light 24 is emitted from the reading light source 23 . This excitation light 24 is taken into the optical waveguide 27 from the light incidence grating coupler 28, and travels within the optical waveguide 21 to the left in FIG. The excitation light 24 is extracted out of the optical waveguide 27 by a condensing grating coupler 29 for light emission, and is directed to the lower part of FIG.
Go to the side. Here, since the light-emitting condensing grating coupler 29 has the structure described above, the excitation light 24 emitted from the light-emitting condensing grating coupler 29 is condensed, and the excitation light 24 is collected by the stimulable phosphor. It focuses into a small spot within the sheet 13.

A portion of the stimulable phosphor sheet 13 that has been irradiated with the excitation light 24 in this manner emits stimulated luminescent light 30 of light m corresponding to the radiation energy accumulated in that portion. This stimulated luminescence light 30 is received by the light receiving surface 20a of the photodetector 20 having a large area, and the photodetector 20
A read image signal S corresponding to the amount of light is emitted from the light source.

As described above, since the rotating drum 10 is being rotated when the excitation light 24 is irradiated onto the stimulable phosphor sheet 13, the excitation light 24 passes over the stimulable phosphor sheet 13 in the circumferential direction of the rotating drum, that is, in the first direction. Scan in the direction of arrow X in Figure 1 (main scan)
. At the same time, the screw rod 15 is rotated and the reading head 16 is moved in the direction of arrow Y, so that the excitation light 2
4 is scanned in this direction (sub-scanning). In this way, the stimulable phosphor sheet 13 is two-dimensionally scanned by the excitation light 24, so that the time-series read image signal S carrying the radiation image information stored and recorded on the stimulable phosphor sheet 13 is can get. This read image signal S is subjected to processing such as amplification and digitization in the reading circuit 40, and is then processed by the image processing circuit 4.
1 to the image reproduction device 42. This image reproducing device 42 includes, for example, a CRT, an optical scanning recording device, etc.
Based on the read image signal S, the stimulable phosphor sheet 1
Replay the radiation image recorded in 3. In this way, without immediately reproducing the image in the image reproducing device 42,
The image signal S may be temporarily recorded on a recording medium such as an optical disk or a magnetic disk.

Note that in order to accurately focus the excitation light 24 on the stimulable phosphor sheet 13, it is necessary to focus the excitation light 24 on the optical waveguide element 2.
5 and the optical waveguide element? 5 and the stimulable phosphor sheet 13, that is, the light receiving surface 2 of the photodetector 20
It is only necessary to adjust the distance between Oa and the circumferential surface of the rotating drum 10 to a predetermined value.

The optical waveguide element 25, which functions to guide the excitation light 24 between the photodetector 20 and the stimulable phosphor sheet 13, can be formed extremely thin, for example, about 1 mm or less including the substrate, and therefore the photodetector The distance between the light-receiving surface 20a of 20 and the stimulable phosphor sheet 13 is, for example, several mm (for example, 3 to 4 mm) even considering the optical path length for focusing the excitation light 24.
) can be set sufficiently small. Therefore, the light receiving efficiency of the stimulated luminescent light 30 is significantly increased compared to the conventional device. In order to increase the light receiving efficiency of the stimulated luminescent light 30 in this way, it is necessary to make the area of the optical waveguide element 25 sufficiently smaller than the area of the light receiving surface 20a. FIG. 3 shows the device according to this embodiment viewed from the direction of arrow B in FIG. Assuming that the angle at which the element 25 is viewed is β, it is desirable to set the area of the optical waveguide element 25 so that β/α is 15% or less, more preferably 10% or less.

Further, in order to increase the light receiving efficiency, the circumferential surface of the rotating drum 10 and the support of the stimulable phosphor sheet 13 may be made of a light-transmitting material, and then the structure shown in FIG. 4 may be adopted. good. In this Fig. 4, elements equivalent to those in Fig. 1.2 are given the same number f1, and explanations thereof will be omitted (same as under CIX). In the apparatus shown in FIG. 4, there is also a photodetector 20' inside the rotating drum 10.
The photodetector 20' is moved together with the photodetector 20 by, for example, being connected to the reading head 16, so that the stimulated luminescence light 30 is simultaneously detected by the two photodetectors 20 and 20'. There is. That is, the stimulated luminescence light 30 is the excitation light 24
Since the stimulable luminescent light 30 is also emitted toward the back side of the sheet at the location on the stimulable phosphor sheet 13 that has been irradiated by detection becomes possible, and light collection efficiency is further increased. In this case, the output signals of both photodetectors 20 and 20 are added to form a read image signal.

In the embodiment device described above, the optical waveguide element 2
5 is fixed to the surface of the light-receiving surface 20a of the photodetector 20, but the optical waveguide element 25 may be placed between the photodetector 20 and the stimulable phosphor sheet 13 by other methods. . However, if the optical waveguide element 25 is directly fixed to the light-receiving surface 20a, it is advantageous to shorten the distance between the photodetector 20 and the stimulable phosphor sheet 13, and the holding means for the optical waveguide element 25 is is not required separately, which is advantageous in terms of simplification of the device.

Furthermore, in the embodiment device described above, the light incidence grating coupler 28 is used as the light incidence part of the optical waveguide element 25, but in order to take the excitation light 24 into the optical waveguide 27, a coupler prism, etc. Alternatively, a semiconductor laser or the like may be directly coupled to the end face of the optical waveguide 27 as a light incidence part. When the light source is directly coupled to the optical waveguide 21 in this manner, a waveguide lens may be appropriately formed in the optical waveguide 27 to collimate the excitation light beam.

Furthermore, in the embodiment device described above, the excitation light 24 is scanned two-dimensionally over the stimulable phosphor sheet 13 by the rotation of the rotary drum 10 and the lateral movement of the reading head 16. The two-dimensional scanning of 24 is not limited to this method, but may be performed using other known methods. For example, the apparatus shown in FIG. 5 reads radiation image information from a disk-shaped stimulable phosphor sheet 50. In this apparatus, the disk-shaped stimulable phosphor sheet 50 is rotated by a motor 51. At the same time, the reading head 16 is moved in the radial direction of the stimulable phosphor sheet 50. Even in this case, the stimulable phosphor sheet 50 is two-dimensionally scanned by the excitation light 24, and the radiation image information recorded thereon can be read. For example, when reading radiation image information from a stimulable phosphor sheet formed in a rectangular shape, the stimulable phosphor sheet is fed in a sub-scanning direction and read in a direction substantially perpendicular to the sub-scanning direction. Main scanning may be performed by moving the head 16, or two-dimensional scanning of the excitation light may be performed by moving the reading head 16 in the vertical and horizontal directions while keeping the stimulable phosphor sheet fixed. It's okay.

Furthermore, the present invention is not limited to an apparatus for reading radiation image information from a stimulable phosphor sheet as described above, but is also applicable to other recording media by scanning the reading light two-dimensionally, thereby emitting light from the recording medium. The present invention can be applied to any image information reading device that reads image information by detecting emitted light or reflected light.

(Effects of the Invention) As explained above in detail, in the image information reading device of the present invention, the reading light is made incident on the recording medium by the optical waveguide element disposed between the photodetector and the recording medium. , the photodetector can be arranged and placed sufficiently close to the recording medium.

Therefore, according to the apparatus of the present invention, it is possible to greatly increase the light receiving efficiency of emitted light or reflected light from a recording medium, and obtain a read image signal with a high S/N ratio.

[Brief explanation of drawings]

1 and 2 are respectively a plan view and a partially cutaway side view showing a device according to a partial embodiment of the present invention, and FIG. 3 is a diagram showing the above-described embodiment 711!
FIG. 4 is a partially cutaway side view showing another embodiment of the device of the present invention; FIG. 5 is a partially cutaway side view of a device of embodiment B of the present invention; FIG. It is a partially broken side view. 10... Rotating drum 12.19.51...
Motor 13.50...Storage phosphor sheet 14...
・Guide rod 15...Screw rod 16...
・Reading head 20.20'...photodetector 20a
... Light receiving surface 23 of photodetector ... Reading light source
24... Excitation light 25... Optical waveguide element 26.
... Substrate 21 ... Optical waveguide 28 ... Grating coupler for light incidence 29 ...
Light-emitting condensing grating coupler 30...stimulated luminescent light Fig. 3 Fig. 4

Claims (4)

[Claims] (1) Scanning light from a reading light source two-dimensionally over a recording medium on which image information is recorded, and photoelectrically detecting the emitted light or reflected light emitted from the recording medium by scanning the reading light. An image information reading device that reads the image information using a photodetector, which is arranged close to the recording medium and directly detects the emitted light or reflected light without going through a lens system; and an optical waveguide on the substrate. A light incident portion and a condensing grating coupler for light output are provided on the surface of the optical waveguide, and between the photodetector and the recording medium,
The light incidence part is disposed away from the photodetector and the light emitting condensing grating coupler is arranged so as to face the recording medium, and reads the reading light from the reading light source from the light incidence part into the optical waveguide. 1. An image information reading device comprising: an optical waveguide element that causes reading light traveling therein to be emitted from a light-emitting condensing grating coupler and focused on a recording medium. (2) The recording medium is a stimulable phosphor sheet, and the reading light source is an excitation light source that emits excitation light that causes radiation energy stored in the stimulable phosphor sheet to be released as stimulated luminescence light. An image information reading device according to claim 1, characterized in that: (3) A patent claim characterized in that a solid angle at which the optical waveguide element is viewed from a light emitting point or a reflection point on the recording medium is sufficiently smaller than a solid angle at which the light receiving surface of the photodetector is viewed from the same point. The image information reading device according to the range 1 or 2. (4) The image information reading device according to any one of claims 1 to 3, wherein the optical waveguide element is fixed on a light receiving surface of a photodetector.