JPS62169571A - Information reader for radiation picture - Google Patents

Abstract

PURPOSE:To improve the availability of excited light and to ensure reading with high sensitivity with use of an exciting light source of a small output, by providing a multi-layer filter which increases the reflection factor to the excited light in response to the increase of the incident angle and also transmits satisfactorily the emitted bright light regardless of said incident angle to the optical path of the excited light close to a storage-type fluorescent sheet. CONSTITUTION:This multi-layer filter 30 is equal to a short path filter having spectral transmission factor characteristics. A laser beam 13, i.e., excited light is made incident on a storage-type fluorescent sheet 10 at an incident angle close to 0 deg.. Then the beam 13 passes through the filter satisfactorily with a transmission factor of about 90% and reaches the sheet 10 to excite a storage- type phosphor 10B. The light which is made incident on the filter 30 at a large incident angle is reflected by the filter 30 with a high reflection factor out of the reflected light 13a and sent back again to the sheet 10 to excite the phosphor 10B. That is, the beam 13 is enclosed between the filter 30 and the sheet 10 and then used effectively to excite the phosphor 10B.

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. The present invention relates to a radiation image information reading device that photoelectrically detects stimulated luminescence light to read the radiation image information, and particularly relates to a radiation image information reading device that uses a multilayer filter to improve the utilization efficiency of the excitation light. I can buy things.

(Technical Background and Prior Art of the Invention) When certain kinds of phosphors are irradiated with radiation (X-rays, α-rays, 8-rays, γ-rays, electron beams, ultraviolet rays, etc.), a part of this radiation energy is released. It is known that the phosphor is accumulated in a phosphor, and when this phosphor is irradiated with excitation light such as phosphor, the phosphor exhibits exhaustion light depending on the accumulated energy. A fluorophore that exhibits yellow color is an accumulative fluorophore (exhaustive fluorophore).
Using a stimulable phosphor called a stimulable phosphor, radiation image information of a photographic object such as a human body is recorded on the stimulable phosphor sheet 1, and this stimulable phosphor sheet is exposed to a laser beam. The stimulated luminescence light is generated by scanning two-dimensionally with excitation light such as Based on this, a teaching line image information recording and reproducing system has already been proposed by Mr. Hondashi, which outputs the image of the subject as a visible image on a recording material such as a photographic light-sensitive material or a display device such as a CRT. (Mochima Sho 55-1242g, Mochima Sho 56-+t395.

) This system has the practical advantage of being able to record images over a much wider range of radiation exposure compared to conventional silver-based radiographic systems; In the light body, there are !)lI! It is recognized that the amount of emitted light that is stimulated and emitted by excitation after accumulation is proportional to the amount of I exposure over a very wide range. Even if the amount of stimulated light emitted from the stimulable phosphor sheet changes, the reading gain is set to an appropriate value, the photoelectric conversion means reads it and converts it into an electrical signal, and this electrical signal is used. By outputting the teaching line image as a visible image on a recording material such as a photographic photosensitive material board 1 or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained.

By the way, in the above-mentioned radiation image information recording and reproducing system, a problem has conventionally been recognized that the utilization efficiency of excitation light is low. In other words, most of the excitation light such as laser light is reflected on the surface of the stimulable phosphor sheet,
This is because the storage phosphor is effectively utilized. In the past, especially when reading with high sensitivity was required, a high-output excitation light source was required, and the power consumption thereof also increased, which was an inconvenience.

(Object of the Invention) The present invention was made in view of the above circumstances, and it is necessary to develop a radiation line that sufficiently increases the utilization efficiency of excitation light and thus enables high-sensitivity reading with a low-output excitation light source. The purpose of this invention is to provide an image information reading device.

(Structure of the Invention) As described above, the copper wire image information reading device of the present invention scans excitation light two-dimensionally on a stimulable phosphor sheet.
The luminescent light emitted by the projection line image information reading device (1), which is photoelectrically read by a photodetector (r), the excitation light optical path (r) in the vicinity of the stimulable phosphor sheet.
We have provided a multilayer filter that increases the incident height of the excitation light by increasing its incidence angle, while transmitting the stimulated luminescence light with good visibility regardless of its incidence angle. 'J@
Required for QQ.

Above) The multilayer IQ filter is made by vacuum-depositing two or more kinds of materials with different optical properties onto a substrate, and then forming a layer of 10 layers one after the other, since the optical density of about 9 is different. That's what happens. In this case, by setting the light @ orimoto ayohi call of each substance appropriately, the properties of the growth can be improved. In addition, as 1 for a low refractive index object (for example, S:Oz, ヅC+F2, etc., on the other hand, as a crystal netf ratio tgo, for example, 102, ';l r O:!).

ZnS'4 is also used.

Furthermore, arranging the multilayer film filter in close proximity to the stimulable fluorescent sheet means arranging it in contact with the sheet, and arranging it with a minute gap between it and the sheet. shall include both.

(Function) When the above-mentioned multi-layer filter or stimulable phosphor sheet is placed in the excitation light optical path, the incident angle should be made sufficiently small (usually as close to Oo as possible). >The inferior tl light emitted onto the stimulable phosphor sheet b passes through the multilayer filter well and reaches the stimulable phosphor sheet i. Then, the excitation light that is orgy 0 = I returns to the multilayer filter at different angles, but at this time, the excitation light that enters the multilayer filter at a wide angle of incidence is reflected in each prefecture in the filter. , the excitation light reflected on the stimulable phosphor sheet is reflected again to the stimulable phosphor sheet.
In other words, it becomes trapped between the phosphor and the multilayer filter, and is effectively used for the generation of the stimulable phosphor (excited light).

On the other hand, iI! emitted from the stimulable phosphor sheet by irradiation with the excitation light! Although the stimulated luminescence light is also emitted from the sheet at different angles, the stimulated luminescence light can be detected with a high fA rate by a photodetector since it passes well through the multilayer filter having the characteristics described above.

(Embodiment) Hereinafter, the explanation will be explained in detail based on the embodiment shown in the drawings.

FIGS. 1 and 2 show a first sling-like device of the present invention. For example, the stimulable phosphor sheet 10 that accumulates and records transmitted light line image information of a subject such as a human body by irradiating a teaching ray such as an X-ray through the subject is a first
As shown in the figure, the sheet is conveyed in the direction of the arrow Y for sub-inspection by a sheet conveying means 11 such as a belt or the like. Further, a laser beam 13 as excitation light emitted from the laser light source 12 is deflected by a galvanometer mirror 14 that swings back and forth, and a multi-layer filter 3 to be described later is used.
0 and main scans the stimulable phosphor sheet 10 in the direction of the arrow X, which is approximately at an angle of 100 degrees with the sub-scanning direction Y. From the 100 locations on the sheet irradiated with the laser beam 13 in this way,
Stimulated luminescent light 15 is emitted in an amount corresponding to the Makiken line image information that has been stored and recorded. This stimulated luminescent light 15 passes through the multilayer filter 30, is collected by a condenser 16, and is photoelectrically detected by a photomultiplier (photomultiplier tube) 17 as a photodetector. The light condensing beam 16 is made by molding a light guide material such as an acrylic plate, and extends along the linear incident end surface 16a or the beam scanning line on the stimulable phosphor sheet 10. The light receiving surface of the photomultiplier 17 is coupled to the annularly formed output end surface 16b.

The emitted light 15 entering the light condenser 16 from the incident end surface 16a travels inside the light condensing body 16 in a manner similar to that of a full-blade, and exits from the output end surface 16b to form a multiplier. The amount of stimulated luminescence light 15 received at -17 and carrying the radiographic image information is the photomultiplier v-
17. Incidentally, the stimulable phosphor sheet 10
A condensing mirror 31 is arranged near the surface of the sheet 10 along the main scanning line (see FIG. 2), and the stimulated luminescence light 15 that does not directly go to the condenser 16 is also collected by the mirror. The light is reflected at 31 and is efficiently collected on the condenser 16 side.

The analog output signal (read image signal @) S of the photomultiplier 17 is amplified by the logarithmic amplifier 20,
, /D converter 21 digitizes with a predetermined recording slurry factor. Is the digital read image signal @Sd obtained in this way an image processing device? 2 is input to an image reproducing device 23 such as a CRT or optical scanning recording device, and in the image reproducing device 23, the projection line image that has been stored and recorded on the stimulable phosphor sheet 10 is reproduced. The operation 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 a spectral transmission characteristic as shown in FIG. 3, and as shown in FIG. Multilayer 1 like! ! It consists of 30B.

In this embodiment, the M-laminated phosphor sheet 10
A multilayer filter 30 is arranged so that the above poly-1] 13OB is in direct contact with the stimulable phosphor layer 10[3 formed on the support 10A (for example, made of carphone-filled PET: polyethylene terephthalate, etc.). In fact, this multilayer filter 30 absorbs almost no light, and therefore has a reflection height that is less than the transmittance shown in FIG. 3 from 1 (100%). In this embodiment, a beam with a wavelength of 633 nm emitted from a j-1e-Ne laser is used as the laser beam 13 required as excitation light. As shown in FIG. 3, the light transmittance of the multilayer filter 30 to the laser beam 13 is approximately 90% at the above-mentioned incident angles O', 30', 45', and 8, respectively.
20%, then 5%, which rapidly decreases as the angle of incidence increases (
In other words, the reflectance increases). -5 The stimulable phosphor sheet 10 subjected to one teaching line image reading in the apparatus of this embodiment is excited by the laser beam 13, and has a wavelength of 360-, -42Qnm (mainly 390nm).
It emits exhausted light 15 with a wavelength of >. As shown in FIG. 3, the multilayer filter 301 satisfactorily transmits light in this wavelength range with a transmittance of 90% #J regardless of the incident angle; The incident angle dependence of is shown in FIG. 8 for easy understanding.

As shown in FIG. 2, a laser beam 13 serving as excitation light is made incident on the stimulable phosphor sheet 10 at an incident angle close to O. This laser beam 13 passes through the multilayer filter 30 with a transmittance of about 90%, reaches the stimulable phosphor sheet 10, and excites the stimulable phosphor 10B as described above. . This laser beam 13 is emitted from the surface of the phosphor layer 10 [3 of the stimulable phosphor sheet 10 and returns to the multilayer filter 30 side. This reflection is diffuse reflection, and the reflected light 13a is reflected by the multi-influence filter 30
Of such reflected light 13a that is incident on the multilayer filter 30 at various incident angles, the light that is incident on the multilayer filter 30 at a large incident angle is highly reflected by the filter 30 having the above-mentioned characteristics. It returns to the stimulable phosphor sheet 10 side again to excite the stimulable phosphor 103. In other words, in this device, the laser beam 13 generated by the excitation light is reflected by the multi-IHGi filter 30 and accumulated. The stimulable phosphor sheet 10 is trapped between the stimulable phosphor sheet 10 and used for loading to excite the stimulable phosphor 103.

Note that the stimulated luminescent light 15 also enters the polyolfactory filter 30 at different angles, but the polyolfactory filter 30 transmits the stimulated luminescent light 15 well regardless of the angle of incidence, as described above. Therefore, the stimulated luminescent light 15 efficiently enters the condenser 16.

Here, the effect of the above-mentioned multi@call filter 30 will be explained in detail by citing numerical values. As a comparative example, reading was carried out using the following devices 1 to 2, and the reading sensitivity in each case was measured.

It should be noted that the parts not specifically described are the same as those in the apparatus shown in FIG. 1 above.

■A device that does not include a multi-filter filter 30.

■The substrate glass 30 instead of the multi-filter 30
A device with only A installed.

(2) An apparatus using a multilayer filter having the spectral transmittance shown in FIG. 4 instead of the multilayer filter 30.

A device (fifth
(see figure).

′ is the device of the above-mentioned embodiment.

The table below shows the reading sensitivity in each case.2This sensitivity is based on the sensitivity of the conventional device (■) as 100! = Determined by relative sensitivity. Also, the sharpness CTF (Contr) of the read image
ast Trans4erpunction> was also measured. Furthermore, CTFL, C! Fz is 1 line each/#
, the force measurement is all 1 in the CTF for 2 lines/ro
Data for line 7fHM was taken for 8 lines, and the average value was taken as the measured value.

As shown in this table, the devices of the present invention (devices with ■, ■, and C power) can improve the reading sensitivity by about twice as much as the conventional devices while keeping the excitation light energy unchanged. I can do it. Note that when using the apparatus of the present invention, the sharpness of the read image is lower than when using the conventional g position. This is thought to be because the excitation light once scattered on the stimulable phosphor sheet 10 is used to excite the stimulable phosphor sheet 10, so that excitation is performed by the partially ejected excitation light. This sharpness can be increased by, for example, making the phosphor layer 10B of the stimulable phosphor sheet 10 thinner,
Furthermore, if particularly high sharpness is not required, but instead high sensitivity is required, the above-mentioned measures for improving sharpness may not be performed.

In addition, in the example explained above, the multi@simulation filter 30
is arranged so as to be in contact with the stimulable phosphor sheet 10, and as shown in FIG. You can do it like this. Generally, reading of 1ill copper wire image information is carried out by conveying the stimulable phosphor sheet for sub-scanning.
If it is placed apart from the stimulable phosphor sheet 10,
Accumulative phosphor sheet] 0; B and multi@olfactory filter 30
If the single-fold filter 30 is arranged in this way, which is preferable because it prevents wear, the sharpness will drop considerably, so the above-mentioned sharpness improvement device may be provided as necessary.

Furthermore, in the embodiments described above, a short-pass filter having the spectral transmittance characteristics shown in FIG. 3 or 4 is used as the multilayer@filter, but in the present invention, a short-pass filter having the spectral transmittance characteristics shown in FIG. It is also not possible to use a multilayer filter (the spectral transmittance characteristics of which are schematically shown in FIG. 7). In other words, as a band-pass filter type multilayer filter, the reflectance for excitation light increases as the angle of incidence increases, while the spectral transmittance of stimulated luminescence light is well transmitted regardless of the angle of incidence. If you look at what has its own characteristics, you will be impressed by the effect of the same work as the previous one.

An example of the incident angle dependence of the light transmission rate of this band-pass filter is shown in Fig. 9 using the apparatus of the present invention (preparation 1). The light reflectance is 70% or more, more preferably 80% or more (that is, the excitation light reflectance is 30% or less, preferably 20% or less), and the excitation crossing q4 ratio is more preferably 60% or more at an incident angle of 30' or more. is 70%
In the above, it is preferable to use a material having a 1iiFR emission light transmittance of 60% or more, preferably 80% or more at an incident angle of 0 to 40'.

(Effects of the Invention) As explained in detail above, in the teaching line image information reading device of the present invention, the excitation light is utilized by the action of the multi@mimetic filter disposed in the excitation light optical path close to the stimulable phosphor sheet. It is now possible to sufficiently increase efficiency. Therefore, according to the device of the present invention, a low-output excitation light source is used, power consumption is reduced, and mosquitoes can be eliminated! ) It is impossible to sufficiently increase the sensitivity of reading one-line image information. Furthermore, since the device of the present invention requires a multilayer filter that produces the above-mentioned effects to be placed in the excitation light path, the device does not require expensive multilayer filters for all stimulable phosphor sheets. It is possible to form a radiation image information reading system at a lower cost than in the case where the wave troughs are formed.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view showing a device according to one embodiment of the invention, Fig. 2 is a side view showing an enlarged main part of the device according to the above embodiment, and Figs. Graphs showing examples of spectral transmittance characteristics of the multi-q filter used for each incident color of light; FIGS. 5 and 6 are side views showing an apparatus according to another embodiment of the present invention, and FIG. Graphs showing the spectral transmittance characteristics of another multilayer filter that can be used in the device of the present invention, FIGS. 8 and 9 show the transmittance of the multilayer filter used in the device of the present invention to excitation light and stimulated luminescence light. This is a graph showing an example of the dependence of the angle of incidence on the angle of incidence. 10... Stimulative phosphor sheet 11... Sheet conveyance means 12... Laser light source 13... Laser beam 14
... Calhanometer mirror 15 ... Stimulated luminescence light 17
...Photo multiplier 30...Multi@III filter 30△...Glass substrate 3013...Multi@olfactory map engraving (no change in content) rSt Muno 2nd diagram! p 51z 1 Figure 6 11 10B 10A (Voluntary) Amendment to the procedure Director General of the Patent Office February 20, 1985 1. Indication of the case Patent Application No. 10753/1988 2. Title of the invention Radiographic image information reading device 3. Relationship with the case of the person making the amendment Patent applicant Location 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name Name
Fuji Photo Film Co., Ltd. 4, Agent

Claims (3)

[Claims] (1) Excitation light is scanned two-dimensionally on a stimulable phosphor sheet on which radiographic image information is accumulated and recorded, and stimulated luminescence light emitted from the part of the sheet that has been scanned by this excitation light is optically detected. In the radiation image information reading device that photoelectrically reads the information using a device, the stimulated luminescence light is transmitted to the excitation light optical path close to the sheet, while the reflectance of the excitation light increases as the angle of incidence increases. A radiation image information reading device characterized by being provided with a multilayer filter that allows good transmission regardless of the incident angle. (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.