JPS62203464A - Radiographic information reader - Google Patents

Abstract

PURPOSE:To sufficiently improve the sensitivity of radiographic information reading with less power consumption by using a photodetector comprised of photoelectric transducers using an electric circuit to which time series processing is applied to the signal of each picture element. CONSTITUTION:A line sensor 3 is arranged near downward to an accumulative type fluorescent material 10. The line sensor 3 is arranged so as to be prolonged over the entire reading region width of the sheet 10 in a direction nearly orthogonally intersecting with the direction Y of the said subscanning. Then a linear stimulating light source 2 prolonged in opposition via the sheet 10 to the line sensor 3 is arranged above the sheet 10. A laser beam as a stimulated light is made incident in the accumulative type fluorescent material 10 at an incident angle close to 0 deg., is transmitted through a multilayer film filter 30 whose transmittance is nearly 90% in an excellent manner, the beam reaches the storage fluorescent sheet 10, which is to be stimulated. That is, the laser beam 14 being a stimulated light is confined between the filter 30 and the sheet 10.

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 has been accumulated and recorded, thereby increasing the amount of photosensitivity emitted from the stimulable phosphor sheet. The present invention relates to a radiation image information reading device that photoelectrically detects emitted light and reads the radiation image information, and particularly relates to a radiation image information reading device that uses a multi-absorbing filter to improve the utilization efficiency of the excitation light. It is.

(Technical Background and Prior Art of the Invention) Certain phosphors contain tlitA rays (X-rays, α-rays, β-rays, T
When this phosphor is irradiated with excitation light such as visible light, a portion of this Maki IJJ ray energy is accumulated in the phosphor. It is known that the body exhibits photostimulated luminescence.
A phosphor exhibiting such properties is called a stimulable phosphor (stimulable phosphor).

Using this stimulable phosphor, radiation image information of a subject such as a human body is temporarily recorded on a stimulable phosphor sheet, and this stimulable phosphor sheet is irradiated with excitation light to generate stimulated luminescence light. The obtained stimulated luminescence light is photoelectrically read by a photodetector to generate 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 present applicant has already proposed a system for recording and reproducing radiation image information that outputs it as an image (Japanese Patent Application Laid-open Nos. 55-12429 and 56-11395, etc.). It has the practical advantage of recording images over a much wider radiation exposure ld compared to the radiographic systems used. 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 the amount of radiation exposure varies depending on various imaging conditions. Even if the value varies considerably, the amount of stimulated luminescence light emitted from the stimulable phosphor sheet is read by a photoelectric conversion means with the reading gain set to an appropriate value and converted into an electrical signal.
Recording materials such as photographic light-sensitive materials, CR
By outputting a radiation image as a visible image on a display device such as a T-type display device, 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 carriers, 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 element is processed sequentially by scanning the excitation light, the overall processing time becomes longer. There is a problem that high-speed reading is difficult. 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 condensing optical system.

In addition, although the latter method has the advantage that high-speed reading is possible and the reading device can be made compact, the sensitivity of the two-dimensional solid-state image sensor or semiconductor line sensor, S, /
The drawback is that N is 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 VC device of the present invention basically consists of the above-mentioned pixels. Stimulated luminescence light is detected by a photodetector consisting of divided photoelectric conversion elements, and this photodetector is placed on the side of the stimulable phosphor sheet opposite to the excitation light irradiation OA side so as to face the sheet. In the excitation light path close to the sheet, there is a multi-cover which reflects the stimulated luminescence light well regardless of the angle of incidence, while the reflectance of the excitation light increases as the angle of incidence of the excitation light increases. It is characterized by the arrangement of filters.

Since the above-mentioned detector is provided on the opposite side of the sheet from the excitation light source, there is no need to consider its placement in relation to the optical path of the excitation light; therefore, the above-mentioned photodetector is efficiently It can be placed at any position where emitted light can be incident. Further, as the detector provided in the apparatus of the present invention, a general photodetector that does not allow excitation light to pass through its structure can be used.

For example, as shown in Japanese Patent Application Laid-Open No. 60-111568M, a structure in which an electrode layer, a photoconductor, and divided transparent electrodes are stacked on a light-shielding substrate can be used.

In addition, the above-mentioned multi@film filter has two different optical refractive indexes.
It is made by sequentially laminating more than one type of substances on a substrate by vacuum evaporation or the like to a thickness of about 1/4 of the wavelength of light. In this case, various properties can be obtained by appropriately setting the optical refractive index and olfactory thickness of each substance. ,,As a low diffraction index material, for example, 3i0z,
MQFz, etc., while high curvature index materials include, for example, TICh.
, ZrO2, ZnS, etc. are used.

Also, placing the multi-filter in close proximity to the stimulable fluorescent sheet means placing it in contact with the sheet and placing it with a small gap between it and the cough sheet. shall include both.

(Effect) Many things like the above! If the II filter is placed in the excitation light path close to the stimulable phosphor sheet, the angle of incidence should be reduced by a sufficient amount (usually as close to Oo as possible).
The excitation light incident on the stimulable phosphor sheet passes through the multi-olfactory filter well and reaches the sheet. The excitation light that reaches the stimulable phosphor sheet and is diffusely reflected there returns to the multi-film filter at various angles, but at this time, the excitation light that enters the multi-film filter at a large angle of incidence is A large amount of the light is reflected and 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 multi-layer filter, so that the excitation light is effectively used for Fjjj activation of the stimulable phosphor. become.

On the other hand, by providing the multi-layer filter, the stimulated luminescent light emitted from the stimulable phosphor sheet by irradiation with the excitation light can be detected in the direction opposite to that of photodetection, that is, multi-layer filter.
It is also possible to prevent loss of stimulated luminescent light due to the luminescent light emitted on the side where the hood filter is provided not being detected.

In other words, the stimulated luminescence light emitted in the opposite direction to the photodetection is
Since it is well reflected by the 11fl filter regardless of the incident angle, this stimulated luminescence light can be made incident on a photodetector, and the ql-stimulated luminescence light can be detected more efficiently than before.

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

Figures 1.2 and 3 show a first embodiment of the device of the present invention. As an example, in the device of this embodiment, the reading section is formed as a line sensor. For example, X?
As shown in FIG.
The sheet is transported in the direction of arrow Y for sub-scanning by sheet transport means 11 such as a pair of nip rollers. A line sensor 3 is arranged close to the stimulable phosphor sheet 10 from below. 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. and sheet 1
A linear excitation light source 2 is disposed above the line sensor 3 and extends oppositely to the line sensor 3 with a sheet 10 interposed therebetween.

The linear excitation light source 2 may be, 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, a Xe lamp, etc., with an aperture having a row of slits or small holes. Combinations etc. 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 has a transparent electrode @7 on the light-shielding substrate 6,
It is formed by horizontally forming a photoconductor @8 and a transparent electrode 1!9. By dividing either or both of the transparent electrodes @7 and 9 into 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 @9 divided into pixels.

When reading radiation image information from the stimulable phosphor sheet 10, the sheet is linearly irradiated with excitation light 14 from the excitation light source 2. The stimulated luminescent light 15 carrying image information generated from the sheet 1 by this excitation light irradiation is transmitted through transparent electrodes!
! ! The light passes through the photoconductor @8 and is received by the photoconductor @8. As the photoconductor @8, a material whose energy gap ECI is smaller than the energy ilc/λz(-hν2) of the stimulated luminescent light 15 is used.

Further, the transparent electrode @9 (formed of ITO, for example) is divided into minute units in the longitudinal direction of the line sensor 3,
Potential difference generated between one divided transparent electrode @ 9 and transparent electrode stand 7 (photoconductor @ 8 between two electrodes @ 9
A potential difference generated by accumulation of signals caused by photocarriers generated upon reception of stimulated luminescence light 15 corresponds to an image signal for one pixel. The signals from the photocarriers taken out into the N-type portions 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 scanning line pitch in the direction of arrow Y with respect to the light source 2 and line sensor 3, the sheet 10
Image information over the entire surface of the image can be read as a time-series image signal.

Next, the scanning circuit following the line sensor 3 will be explained.

FIG. 4 is an equivalent circuit of a line sensor and a scanning circuit using a photoconductor. Signals from photocarriers generated when stimulated luminescence light (hv2) hits the solid-state photoelectric conversion elements 8a, 8b, and 8C using photoconductors are the photoconductors 3a,
Capacitor C in F3b, 8c! is accumulated in The accumulated photocarrier signal is transferred to the shift register 16.
The signals are sequentially read out by sequentially opening and closing the switch section 17, thereby obtaining time-series image signals. The image signal is then amplified by the amplifier 12 and output from its output terminal 13.

Incidentally, the M2S section including the switch section 17 and the shift register 91 may be replaced with a COD.

Moreover, the line sensor 3 is the actual f11. In addition to the above embodiments, for example, an array of photodiodes as shown in Japanese Patent Application Laid-Open No. 60-111568 may be used.

Furthermore, in the above example, the photodetector includes many solid-state photoelectric conversion elements.
Although it is described as a line sensor arranged in a row, the photodetector according to the sixth aspect of the present invention is not limited to this, and may be a point sensor having one solid-state photoelectric conversion element, or a point sensor having one solid-state photoelectric conversion element. It may also be a planar sensor arranged in a two-dimensional array.

Next, the action of the multi@olfactory filter 30 described above will be explained in detail. For example, this multi-filter filter 30 is a bandpass filter having spectral transmittance characteristics as shown in FIG. 5 when the incident angle to the filter is Oo, and as shown in FIGS. 2 and 3. As shown in FIG.
! 11130B. Konodai@olfactory filter 30
is arranged so that its multi-jli 303 is in direct contact with the sheet 10.

Further, the laser beam 14 is made incident on the multi-Ta high filter 30 in a substantially perpendicular direction, that is, at an angle of incidence of approximately 0°. The polychromatic filter 30 absorbs almost no light, so the transmittance shown in FIG.
The value subtracted from (100%) becomes the reflectance. In this embodiment, as the laser beam 14 which is excitation light, )-
A beam with a wavelength of 633 nm emitted from a 1e-Ne laser is used. As shown in FIG. 5, the light transmittance of the multi-layer filter 30 for the laser beam 14 is approximately 90% when the incident angle is Oo, that is, when the laser beam is incident for excitation of the sheet 10. ing. Further, the light transmittance of the multi-IIm filter 30 for light having wavelengths other than 630 to 650 nm and having an incident angle of Oo is approximately 0%.

- The stimulable phosphor sheet 10 subjected to radiation image information reading in the device according to the embodiment of the strength tree is excited by the laser beam 14, and the length of the stimulable phosphor sheet 10 is 360 to 4200 m (mainly 390 m).
It emits stimulated luminescence light 15 with a wavelength of 100 nm).

In FIG. 6, the above 390 n by multi@olfactory filter 30 is shown.
The dependence of the light transmittance on the incident angle at m and 6330 m is shown.

As mentioned above, the laser beam 14 as excitation light is Oo
Therefore, this laser beam 14 is made incident on the stimulable phosphor sheet 10 at an incident angle close to 9.
About 0% and many 1#! Transmits well through the A filter 30,
The light reaches the stimulable phosphor sheet 10 and excites the stimulable phosphor sheet 10 as described above. This laser beam 14
is reflected to some extent on the surface of the stimulable phosphor sheet 10 and returns to the multilayer filter 30 side.

This reflection is diffuse reflection, and the reflected light 14a enters the multilayer film filter 30 at various angles of incidence.

Of the reflected light 14a, the light that enters the multi-hat 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. Then, the stimulable phosphor sheet 10 is excited again. That is, in this device, the laser beam 14, which is excitation light, is confined between the multi-cover filter 30 and the stimulable phosphor sheet 10, and is effectively used for excitation of the stimulable phosphor sheet 10. Become so.

The stimulated luminescent light 15 also enters the multilayer filter 30 at different angles, but the multilayer filter 30
As shown in the figure, nearly 100% of the stimulated luminescence light 15 is always reflected regardless of its incident angle. Therefore, as shown in FIG. 2, most of the stimulated luminescent light 15 that has emitted toward the multilayer filter 30 is reflected by the multi-olfactory filter 30 and placed below the stimulable phosphor sheet 10. The light is made incident on the inner sensor 3. In this way, the above many @
By using the membrane filter, the device of this embodiment effectively utilizes the laser beam as excitation light to increase the amount of stimulated luminescence light, and also increases the lv! Efficiently detects exhaustion light and improves the sensitivity and S/N of the device.
can be significantly increased compared to conventional methods.

In addition, the multi@olfactory filter in the above-mentioned actual TF & embodiment has extremely favorable characteristics, such as reflecting nearly 100% of the incident stimulated luminescence light and transmitting about 90% of the excitation light when the incident angle is Oo. However, in general, the light transmittance of the excitation light is 70% or more when the incident angle is 0 to 5 degrees, and the reflectance of the excitation light is 60% or more when the incidence angle is 1 g 30' or more, In addition, if the reflectance of stimulated luminescence light is 60% or more, a preferable effect of increasing sensitivity can be achieved. In addition to the above-mentioned glass substrate, a transparent plastic sheet made of polyethylene terephthalate, polyethylene, polynylidene chloride, polyamide, or the like may be used as the substrate for supporting the polygon.

According to experiments conducted by the present inventors, by providing the multilayer filter 30 as described above to increase the efficiency of excitation light use, the reading sensitivity can be approximately doubled compared to the case where the multilayer filter 30 is not provided. I found out that it can be improved.

In addition, in the example explained above, the multiple filter 30
The stimulable phosphor sheet 10 is arranged so as to be in contact with the stimulable phosphor sheet 10, but as shown in FIG. It's okay. In general, radiation image information is read by transporting a stimulable phosphor sheet for sub-scanning, so if the multi@uta filter 30 is placed apart from the stimulable phosphor sheet 10 as described above, , stimulable phosphor sheet 10 and multi-vI! 1f of a filter 30
It is preferable because it prevents rotting.

Further, the multi-1vA filter may be provided in the excitation light optical path close to the stimulable phosphor sheet, and in addition to the one that moves relative to the sheet as described above, for example, a multi-1vA filter may be provided over the entire scanning area of the sheet. temporarily close together,
A filter feeder may be provided together with the sheet sub-scanning means to feed the multi-odor filter together with the sheet in the sub-scanning direction. In this case, multiple @II! If the filter is returned to the reading starting position and the operation of hanging it on the next sheet to be read is repeated, then only one multi-sacrificial filter needs to be provided.

(Effect of the explanation) As explained in detail above, in the radiation image information reading device of the present invention, the signal of each pixel is converted into a time series by an electric circuit rather than by a fixed distortion of a light spot. Since a detector is used, it is possible to sufficiently increase the reading speed of eA-ray image information, and since there is no need for a light deflector or condensing optical system for scanning the light spot, it is possible to miniaturize the device. In addition, in the non-defective device 6, the use efficiency of the excitation light can be sufficiently increased due to the action of the multi-film filter placed in the excitation light optical path close to the stimulable phosphor sheet, and at the same time, the luminance can be improved. The detection efficiency of exhaustion light can also be increased.

Therefore, according to the indefensible device, using a low-output excitation light source,
It is possible to reduce power consumption and sufficiently increase the sensitivity of reading image information on the makisen line, and also to improve the read signal's 8. /N can be increased.

Roughly speaking, this Benmeinsou @ has a multilayer hood filter placed in the excitation light optical path to achieve the above-mentioned effects.
According to the present device, a radiation image information reading system can be formed at a lower cost than in the case where all stimulable phosphor sheets are coated with expensive multi-layer filters.

[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 the spectral transmittance characteristics of the multilayer olfactory filter used in the device of the present invention, and FIG. A graph showing an example of the incident angle dependence of transmittance for exhaustion light. FIG. 7 is a side view showing another embodiment of the device of the present invention. 2... Excitation light source 3... Line sensor 6
...Light-shielding substrate 7...Transparent electrode 18...
・Photoconductor layer 9...Transparent pixel-divided! [! 10... Stimulable phosphor sheet 11... Sheet transport means 14... Excitation light 15... Stimulated luminescence light 30... Multi@membrane filter 3OA... Group
Temporary 303...Multi @ Figure 1 Figure '2 z1'''4 Figure 6 Figure 7 41 Angle

Claims (2)

[Claims] (1) Consisting of an excitation light source that irradiates excitation light onto a stimulable phosphor sheet on which radiographic image information is stored and recorded, and a pixel-divided photoelectric conversion element, which is placed on the side of the sheet opposite to the excitation light irradiation surface. a photodetector disposed opposite to the sheet; and the sheet, wherein the reflectance of the excitation light increases as the angle of incidence increases, while the sheet reflects the stimulated luminescence light well regardless of its angle of incidence. A radiation image information reading device consisting of a multilayer film filter placed in the excitation light optical path close to the . (2) The multilayer filter has a light transmittance of 70% or more for excitation light at an incident angle of 0 to 5 degrees, and an incident angle of 30 degrees.
2. The radiation image information reading device according to claim 1, wherein the reflectance of the excitation light of .degree. or more is 60% or more, and the reflectance of the stimulated luminescence light is 60% or more.