JPS62169145A - Radiograph information reader - Google Patents

Abstract

PURPOSE:To obtain a radiograph picture information reader which is small in size and whose read-processing speed is high and sensitivity and S/N are improved, by providing a photodetector on the exciting light projected surface side of an accumulation type phosphor sheet under a condition where the photodetector is faced to the surface. CONSTITUTION:A line sensor 3 is arranged closely to an accumulation type phosphor sheet 10 from the topside. This line sensor 3 is formed of a light shielding layer 6 provided by putting slits or small holes in a row on a transparent base plate 5, transparent electrode layer 7, thin photoconductive layer 8, and transparent electrode layer 9, which are piled up in the order. When the transparent electrode layer 9 is divided into picture elements at every picture element the laminated body forms a row of numerous solid-state photoelectric transducers corresponding to the picture elements. A multilayer film filter 30 is provided on the surface of the above-mentioned transparent electrode layer 9. Therefore, the receiving three-dimensional angles of stimulated luminescence can be made wider and the S/N of read signals can sufficiently be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention is directed to irradiating excitation light to a stimulable phosphor sheet on which radiographic image information is accumulated and recorded, thereby excitation light emitted from the stimulable phosphor sheet. Regarding a radiation image information reading device that photoelectrically detects stimulated luminescence light and reads the radiation image information, in particular, a radiation image information reading device that uses a multilayer filter to improve the utilization efficiency of the excitation light. It is related to.

(Technical Background and Prior Art of the Invention) When certain types of phosphors are irradiated with radiation (X-rays, α-rays, 8-rays, γ-rays, electron beams, ultraviolet rays, etc.), part of the radiation energy is emitted into 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, and it is known that this phosphor exhibits this property. The fluorophore is called a storage fluorophore (stimulable fluorophore).

Using this stimulable phosphor, fj' of a subject such as a human body
Once the NA image information is recorded on a stimulable phosphor sheet,
This stimulable phosphor sheet is irradiated with excitation light to produce stimulated luminescent light, and the resulting stimulated luminescent light is photoelectrically read by a photodetector to obtain an image signal. Based on this image signal, a photograph is taken. The present applicant has already proposed a radiation image information recording and reproducing system that outputs a teaching line image of a subject as a visible image to a recording material such as a photosensitive material and a display device such as a CRT. (Unexamined Japanese Patent Publication No. 55-12429, 56=11395
No. etc. ) This system has the practical advantage of being able to record images over a significantly wider range of radiation exposures than conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, 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. Even if the exposure amount varies considerably, the amount of stimulated luminescence 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.
Using this electrical signal, recording materials such as photographic light-sensitive materials, CR
By outputting the teaching line image as a visible image on a display device such as T, it is possible to obtain a radiographic image that is not affected by fluctuations in direct line exposure.

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.

However, in the former method, an optical deflector is required to scan the excitation light, making the device complicated and large.Also, since each pixel is processed one by one by scanning the excitation light, the overall processing time becomes longer. The drawback is that high-speed reading is difficult, and when a photomultiplier tube is used, there is a problem in that the device tends to be particularly large due to the multiplier tube body and its light focusing optical system.

Although the latter method has the advantage that high-speed reading is possible and the reading device can be made compact, it has the disadvantage that the sensitivity and S/N of the two-dimensional solid-state image sensor and semiconductor line sensor are not good.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and it can be formed into a small size, has a fast reading processing speed, and has rough sensitivity,
It is an object of the present invention to provide a radiation image information reading device that is excellent in terms of S,/N (Structure of the Invention) The radiation image information reading device of the present invention basically uses the above-mentioned pixel-divided Stimulated luminescence light is detected by a photodetector comprising a photoelectric conversion element, and this photodetector is placed on the excitation light irradiation surface side of the stimulable phosphor sheet so as to face the sheet, Between the photodetector and the stimulable phosphor sheet, there is a multilayer structure that increases the reflectance of the excitation light as the angle of incidence increases, while transmitting the emitted light well regardless of the angle of incidence. It is characterized by the arrangement of a membrane filter.

As the photodetector described above, a configuration that allows excitation light to pass through can also be considered. Such a type of photodetector is, for example, as shown in Japanese Patent Application Laid-Open No. 111568/1983, which includes a transparent substrate, a light shield 1 having a slit or a small hole for passage of excitation light, and a first transparent electrode. A constant layer, a photoconductor 1, and a second transparent electrode stacked one after another, or as shown in Japanese Patent Application No. 59-148440 filed by the present applicant, the above-mentioned transparent substrate Instead, it is possible to use a light-shielding substrate and provide a through-hole in the substrate for passage of excitation light, thereby eliminating the need for the light-shielding layer.

Furthermore, in the apparatus of the present invention, a general photodetector that cannot pass excitation light can also be used. When using such a photodetector, the photodetector is arranged so that the axis of incidence of excitation light on the stimulable phosphor sheet and the receiving axis of the photodetector form an angle, and a multilayer filter is used. It may be placed close to the seat. In this case, only one photodetector may be provided, or the excitation may be predetermined! 2 with II @ in between
You may also provide one.

The multi@olfactory filter described above is made by depositing two or more types of substances with different optical diffraction rates on a substrate at one wavelength of light by vacuum evaporation, etc.
It has a thickness of /4 culm and is made up of several to several dozen layers stacked one after the other. In this case, various characteristics can be obtained by appropriately setting the optical diffraction index and pitch thickness of each material.
An example of a low refractive index material is S! 02, MgF
2, etc., while high refractive index materials include, for example, TiCh, Z
rCh, znS, etc. are used.

In order to place a multi-olfactory filter between the excitation light irradiation part of the stimulable phosphor sheet and the photodetector, it is possible to attach the filter to the surface of the photodetector, or conversely, to place the olfactory filter between the excitation light irradiated part of the stimulable phosphor sheet and the photodetector. It may be attached to the surface of the stimulable phosphor sheet, or it may be placed at a small distance from both the stimulable phosphor sheet and the photodetector.

(Function) When a multi-layer filter as described above is provided between the excitation light irradiation part of the stimulable phosphor sheet and the photodetector, the incident angle can be made sufficiently small (normally The excitation light incident on the stimulable phosphor sheet (as close to Oo as possible) passes through the multilayer filter well and reaches the sheet. The excitation light that reaches the stimulable phosphor sheet and is diffusely reflected there returns to the multilayer filter with various square shapes.At this time, the excitation light that enters the multi-layer filter at a large angle of incidence is A large amount of the light is reflected at the point where the light is turned back toward the stimulable phosphor sheet. In other words, the excitation light reflected on the stimulable phosphor sheet is trapped, so to speak, between the sheet and the multifilter, and the excitation light is effectively used to excite the stimulable phosphor. It becomes like this.

On the other hand, the stimulated luminescent light emitted from the stimulable phosphor sheet by irradiation with the excitation light is also emitted from the sheet at various angles, but this stimulated luminescent light has the characteristics described above. Embodiments The present invention will be described in detail below based on the embodiments shown in the drawings.

1.2 and 3 show a first embodiment of the present invention. In this embodiment, the reading section is formed as a line sensor, as an example. For example, a stimulable phosphor sheet 10 that accumulates and records transmitted radiation image information of a subject such as a human body by irradiating radiation such as X-rays through the subject is an endless belt or the like as shown in FIG. The sheet conveying means 11 conveys the sheet in the direction of arrow Y for sub-scanning. Then, the line sensor 3 is brought close to the stimulable phosphor sheet 10 from above.
are arranged. The line sensor 3 is arranged to extend across the entire width of the recording area of the sheet 10 in a direction substantially perpendicular to the sub-scanning direction Y. A linear excitation light source 2 is arranged above the line sensor 3 and extends over the line sensor 3. This linear excitation light source 2
For example, an array of LEDs or semiconductor lasers that emit light simultaneously in a row, or a non-directional light source such as a fluorescent lamp, an e-lamp, etc. combined with an aperture having a row of slits or small holes. Things can be used.

FIGS. 2 and 3 show the normal cross-sectional shape and side cross-sectional shape of the line sensor 3, respectively.
．． The line sensor 3 will be explained in detail with reference to FIG. The line sensor 3 is formed by laminating a light-shielding layer 6 having a series of slits or small holes on a transparent substrate 5, a transparent electrode layer 7, an N@photoconductor 18, and a transparent electrode 19. By dividing either or both of the transparent electrode layers 7 and 9 for each pixel, this product forms a series of a large number of solid-state photoelectric conversion elements corresponding to the pixels. As an example, this device has a transparent electrode layer 9 divided into pixels, and a polypus filter 30, which will be described in detail later, is installed on the surface of the transparent electrode layer 9 facing the stimulable phosphor sheet 10. Or is provided.

When reading ray image information from the stimulable phosphor sheet 10, the sheet 10 is irradiated with excitation light 14 from the excitation light source 2 through the line sensor 3. That is, the excitation light 14
are transparent substrate 5 of line sensor 3, slit (or small hole) provided in light shielding layer 6, transparent type *@7, photoconductor@
8 and a stimulable phosphor sheet 10 through a transparent electrode @9
is irradiated in a linear manner. Stimulated luminescent light 15 carrying image information generated from the sheet 1 by this excitation light irradiation passes through the transparent electrode 9 and is received by the photoconductor table 8 . The energy gap E9 of the photoconductor-8 is larger than the energy hC/λ1 (-hν1) of the excitation light 14, and the energy i1c/λ2 (-hν1) of the stimulated luminescence light 15.
=hv2) is used.

For example, the US patent f! When using alkaline earth metal fluorohalides activated with rare earth elements described in No. 239968 etc., znS, Zn5
e, CdS, Tio2, Zr1O, etc. can be used.

In addition, when the excitation light 14 includes a short wave component, the excitation light source 2
A shortwave cut filter 4 may be inserted between the line sensor 3 and the line sensor 3 to allow only long wave components to pass.The transparent electrode @9 (formed of ITO, for example)
It is divided into microscopic parts in the longitudinal direction, and the divided 1
Two transparent f! Potential difference generated between one electrode 17.9 and the transparent electrode 7 (in the photoconductor @8 between the two electrodes 17.9, a signal generated by the photocarriers generated by receiving the stimulated luminescent light 15 is accumulated) (potential difference) corresponds to an image signal for one pixel. The signals from the photocarriers taken out for each of the electrodes thus divided are sequentially read out in time series using a shift register, which will be described later. This makes it possible to obtain an image signal for one scanning line. Thereafter, by repeating the above-mentioned operation each time the stimulable phosphor sheet 10 is moved one scan line pitch in the direction of the arrow Y relative to the light source 2 and line sensor 3, image information covering the entire surface of the sheet 10 can be obtained. It can be read as a time-series image signal.

Next, the scanning circuit following the line sensor 3 will be explained.
FIG. 4 shows an equivalent circuit of an in-sensor and a scanning circuit using a photoconductor. Signals generated by photocarriers generated when stimulated luminescence light (hν2) hits solid-state photoelectric conversion elements 8a, 8b, 8c using photoconductors are transmitted by photoconductors 8a, 8c.
b, stored in capacitor C1 in 8c. The signals of the accumulated photocarriers are transferred to the l! They are sequentially read out by opening and closing the IJj order, thereby obtaining time-series image signals. The image signal is then amplified by the amplifier 12 and output from its output terminal 13.

Note that the M2S section including the switch section 17 and the shift register 16 may be replaced with a COD.

Further, the line sensor 3 may be similar to the embodiments described above, for example, a photo diode array as shown in Japanese Patent Laid-Open No. 60-111568. Furthermore, instead of providing the light-shielding layer 6 having slits or small holes as described above, as shown in Japanese Patent Application No. 148440/1989 by the present applicant,
The substrate 5 may be a light-shielding substrate, and the substrate may be provided with a through hole for passage of excitation light.

Furthermore, in the above example, the photodetector includes many solid-state photoelectric conversion elements.
Although the photodetector in the invention is not limited to this, it may be a point-like sensor having one solid-state photoelectric conversion element, or it may be a two-dimensional sensor with a solid-state photoelectric conversion element. It may also be a planar sensor arranged in a target array.

Next, the action of the multilayer filter 30 described above will be explained in detail. This multilayer film filter 30 is, for example, a short-pass filter having high spectral transmission characteristics as shown in FIG. It consists of a polygon 30B as described above. In this embodiment, the filter 30 includes the transparent electrode 19 of the line sensor 3.
The substrate 30A is placed in close contact with the stimulable phosphor sheet 10, and the multi-layer 303 is placed at a minute distance from the stimulable phosphor sheet 10. Note that this multilayer filter 30 absorbs almost no light, so the transmittance shown in FIG. 5 is 1 (100
%) is the counter-proposal. In a non-implemented embodiment, a beam with a wavelength of 633 nm is used as the excitation light 14. As shown in FIG.
The light transmittance of the multi@horo filter 30 is approximately 90 when the above incident angles are O', 30", and 45 degrees, respectively.
%, 20%, and 5%, and as the incident angle increases, the reflectance decreases rapidly (that is, the reflectance increases). −
The stimulable phosphor sheet 10 subjected to I11 ray image information reading in the power tree embodiment device is exposed to the excitation light 14.
360-420nm (mainly 390nm
It emits stimulated luminescence light 15 with a wavelength of >. As shown in FIG. 5, the multi-@horo filter 30 transmits light in this wavelength range well with 90% transmission regardless of the incident angle. Incidentally, the dependence of the transmittance of the light of 390 nm and 633 nm on the incident angle is shown in FIG. 6 for easy understanding.

The excitation light 14 is incident on the stimulable phosphor sheet 10 at an angle of incidence close to Oo, as shown in FIG. Therefore, this excitation light 14 satisfactorily passes through the multi-layer filter 30 with a transmittance of about 90%, reaches the stimulable phosphor sheet 10, and excites the stimulable phosphor as described above. This excitation light 14 is reflected to a certain extent on the surface of the phosphor layer of the stimulable phosphor sheet 10 and returns to the multilateral filter 30 side. This reflection is diffuse reflection, and the reflected light 14a enters the multi-olfactory filter 30 at various angles of incidence. Of the reflected light 14a, the light that enters the multilayer filter 30 at a large incident angle is reflected at a high reflectance by the filter 30 having the above-mentioned characteristics, and is reflected again to the stimulable phosphor sheet 10 side. to excite the storage fluorophore. That is, in this device, the excitation light 14 is confined between the multi-stimulating filter 30 and the stimulable phosphor sheet 10, and is effectively used for excitation of the stimulable phosphor. .

Incidentally, the stimulated luminescent light 15 also enters the multi@hood filter 30 at different angles, but the multi-olfactory filter 30 transmits the stimulated luminescent light 15 well regardless of the angle of incidence, as explained earlier. Therefore, the stimulated luminescence light 15 efficiently enters the line sensor 3.

According to experiments conducted by the present inventors, by providing the multilayer filter 30 as described above and increasing the utilization efficiency of excitation light, the reading sensation can be approximately doubled compared to the case where the multilayer filter 30 is not provided. It was found that it was possible to increase

Note that a lens optical system (for example, a rod lens array, etc.) for condensing luminescent light is disposed between the multi-reflection filter 30 attached to the line sensor 3 and the stimulable phosphor sheet 10. Good too. In this case, the stimulable phosphor sheet 1
The excitation light (reflected light) 14a reflected on the 0 surface, passed through the lens optical system, and returned to the polyolfactory filter 30 is reflected by the polyololfactory filter 30, and passes through almost the same optical path within the lens optical system again. Returning to the stimulable phosphor sheet 10,
Since the sheet 10 is folded back at approximately the same position, the excitation efficiency is improved.

Furthermore, in the example explained above, the multi-nine filter 30
is attached to the line sensor 3, and as shown in FIG. 7, the multi@olfactory filter 30 is placed on or closely held on the stimulable phosphor sheet 10 and conveyed together with the sheet 10. It's okay.

Even in this case, since the multi@hood filter 30 is placed in the excitation light optical path between the stimulable phosphor sheet 10 and the line sensor 3, the same effect as described above can be obtained. . In this case, the multi-filter may be applied to all of the stimulable phosphor sheets 10, or the multi-filter may be applied from the top of the stimulable phosphor sheet whose image has been read to the reading start position. If the operation of returning the sheet and overlapping it on the next sheet to be read is repeated, only one multi-membrane filter is required. In general, as shown in FIG. 8, the multi-hole filter 30 may be placed close to both the line sensor 3 and the stimulable phosphor sheets 1 to 10 while being separated from them.

Furthermore, in the embodiments described above, a short-pass filter having the spectral transmittance characteristics shown in FIG. A filter (the spectral transmittance characteristics of which are schematically shown in FIG. 9) may also be used. In other words, such a band-pass filter type multilayer filter has spectral transmittance characteristics in which the reflectance of excitation light increases as the angle of incidence increases, while the stimulated luminescence light is transmitted satisfactorily regardless of the angle of incidence. The same effect as described above can be obtained by using a material having . FIG. 10 shows an example of the dependence of the light transmittance on the angle of incidence of this multi-olfactory filter, which is a bandpass filter.

6 In the device of the present invention, as a multilayer film filter, the excitation light transmittance is 70% or more, preferably 80% or more (that is, the excitation light reflectance is 30% or less, and more preferably 20% or less) at an incident angle of 5°, And the excitation light reflectance is 60% or more, preferably 70% or more at an incident angle of 30° or more, and the stimulated luminescence light transmittance is 60% or more and more preferably 80% or more at an incident angle of 0 to 40°. It is preferable to use

(Effects of the Invention) As explained in detail above, in the radiation image information reading device of the present invention, a photodetector consisting of a photoelectric conversion element that converts the signal of each pixel into a time series not by scanning a light spot but by an electric circuit. Since the system uses a system, it is possible to sufficiently increase the reading speed of the teaching line image information, and since there is no need for a beam 1 deflector for constant distortion of the light spot or a condensing optical system, it is a unit that can achieve miniaturization of the device. In addition, in the device of the present invention, since the photodetector is arranged opposite to the excitation light irradiation part of the stimulable phosphor sheet, the solid angle for receiving the stimulated luminescence light is large, and the read signal S
, / It is not possible to sufficiently increase N. Furthermore, in the invented device, the efficiency of excitation light utilization can be sufficiently increased by the action of a multilayer filter placed between the stimulable phosphor sheet and the photodetector. .

Therefore, according to the apparatus of the present invention, it is possible to sufficiently increase the sensitivity of reading radiation image information by using a low-output excitation light source and reducing power consumption.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing a device according to one embodiment of the present invention, FIGS. 2 and 3 are a front sectional view and a side sectional view showing the main parts of the device according to the embodiment, respectively, and FIG. 4 is a schematic perspective view showing a device according to the embodiment described above. FIG. 5 is a graph showing an example of the spectral transmittance characteristics of the multilayer film filter used in the device of the present invention on a light incident angle cylinder; FIG. 6 is a circuit diagram showing the scanning circuit used in the device of the present invention; FIG. A graph showing an example of the dependence of the transmittance of a filter on the angle of incidence for excitation light and stimulated emission light. FIG. 9 is a graph showing the spectral transmittance characteristics of another multilayer filter that can be used in the device of the present invention, and FIG. 10 is a graph showing the incident angle of the transmittance for excitation light and stimulated luminescence light of the above-mentioned another multilayer filter. It is a graph showing an example of dependence. 2... Excitation light source 3... Line sensor 5
. . . Transparent blocking plate 6 . ... Sheet transport means 14 ... - Excitation light 15 ... Stimulated luminescence light 30 ... Multilayer film filter 30A ... Substrate 303 ... Voluntary procedure n) 1 Commissioner of the Japan Patent Office Dear February 2, 1986
0th 14+1, Indication of the case Japanese Patent Application No. 11657/1986 2, Name of the invention Radiographic image information reading device 3, Person making the amendment Relationship to the case Patent applicant Address 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name Name
Fuji Shaki Film Co., Ltd. 4, Agent 5-2-1-6 Roppongi, Minato-ku, Tokyo Number of inventions to be increased by amendment None 7 Target of amendment Drawings

Claims (3)

[Claims] (1) Consisting of an excitation light source that irradiates excitation light onto a stimulable phosphor sheet on which radiation image information is stored and recorded, and a pixel-divided photoelectric conversion element, facing the excitation light irradiation surface of the sheet. a photodetector arranged as a sheet, and a photodetector having a reflectance for the excitation light that increases as the angle of incidence thereof increases, while allowing the stimulated luminescence light to pass through satisfactorily regardless of its angle of incidence; A radiation image information reading device consisting of a multilayer film filter placed between the device and the device. (2) The radiation image information reading device according to claim 1, wherein the multilayer filter is a short pass filter. (3) The radiation image information reading device according to claim 1, wherein the multilayer filter is a bandpass filter.