JPH02306235A - Radiograph information reader - Google Patents

Abstract

PURPOSE:To improve sensitivity in reading by providing a band pass filter which transmits light having longer wavelength than stimulated luminous light. CONSTITUTION:When an accumulating phosphor sheet 3 is scanned with exciting light, the stimulated luminous flux is radiated from a point P to all the directions. The angle theta1 of the aperture for condensing of a light guiding path 1 is made larger, so that the luminous light is condensed more. In order to do so, the light guiding path 1 is made to approach to the light emitting posi tion P to enlarge the area of a light entering surface 1a. Thus, an incident angle theta2 on a wide band pass filter 11 provided between a light exiting surface 1b and a photoelectric converter 2 is made larger. Even when the angle theta2 is made larger, the light having the wavelength on the long wavelength side is transmitted through the filter 11 and inputted in the converter, thereby improv ing the sensitivity.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a radiation image information reading device that condenses stimulated luminescence light emitted by scanning a stimulable phosphor plate with excitation light and converts it into an electrical signal. Wavelength of light λ. and this wavelength λ. A broadband band-pass filter that transmits light with longer wavelengths is installed, and the purpose is to eliminate the attenuation of stimulated luminescence light that enters from an oblique direction and improve reading sensitivity. A light guide path for condensing the stimulated luminescence light generated by scanning, and a light guide path for transmitting light of the wavelength of the stimulated luminescence light and transmitting the stimulated luminescence light incident obliquely at the population or exit of this light guide path. It is equipped with a broadband bandpass filter that transmits light up to a wavelength longer than the wavelength of the stimulated luminescent light and blocks the excitation light, and converts the stimulated luminescent light extracted through the broadband bandpass filter into an electrical signal. The device is configured to read X-ray image information, etc.

[Industrial application field]

The present invention relates to a radiation image information reading device that condenses stimulated luminescence light emitted by scanning a stimulable phosphor plate with excitation light and converts it into an electrical signal.

[Prior art and problems to be solved by the invention] Conventionally, as a high-sensitivity, high-resolution X-ray imaging system, a stimulable phosphor plate (sheet) comprising a stimulable phosphor in a sheet form has been used. X-rays that have passed through the object are exposed to the object. The stimulable phosphor plate on which the exposed latent image exists is scanned with spot-shaped laser light as excitation light, and the stimulated luminescence light emitted at this time is focused and detected by PMT (photomultiply). However, there is a method of converting it into digital values and reading the X-ray image of the subject. At this time, in order to extract only the stimulated luminescent light emitted from the M multilayer phosphor plate and block the excitation light, the wavelength λ of the stimulated luminescent light is adjusted as shown in FIG. After passing through a narrowband bandpass filter, the light is photoelectrically converted to read an X-ray image.

However, the stimulated luminescent light emitted in all directions from the stimulable phosphor plate is collected by using a glass fiber or the like with a numerical aperture as large as possible, and of this concentrated light, the stimulated luminescent light is If we try to extract only light and perform photoelectric conversion, more light will enter the bandpass filter from an oblique direction, and the transmission characteristics of the bandpass filter will shift to the shorter wavelength side, as shown by the dotted line in Figure 5. There is a problem in that the detection sensitivity cannot be improved because the stimulated luminescence light is blocked.

The present invention relates to the wavelength λ of stimulated luminescence light. A broadband bandpass filter is provided that transmits light with a wavelength longer than the wavelength λ0, and the purpose is to eliminate attenuation of stimulated luminescence light incident from an oblique direction and improve reading sensitivity.

[Means to solve problems]

In FIG. 1, a means for solving the problem will be explained with reference to FIG. 1. In FIG. It is something.

The broadband bandpass filter 11 transmits light of the wavelength of the stimulated luminescence light at the entrance or exit of the light guide path l, and transmits the light of the long wavelength side to transmit the stimulated luminescence light that is incident obliquely, and also excite the light. It is a broadband bandpass filter that blocks light.

[Effect]

As shown in FIG. 1, the present invention provides a method for attaching stimulated luminescent light to the population or exit of a light guide path 1 that condenses stimulated luminescent light generated by scanning a stimulable phosphor plate 3 with excitation light. A broadband bandpass filter 11 is provided that transmits light with a wavelength of , and transmits stimulated luminescence light that is incident obliquely, and that transmits light with a long wavelength and blocks excitation light. The stimulated luminescent light is converted into an electrical signal to read an X-ray image.

Therefore, the wavelength λ of the stimulated luminescence light. and the light on the long wavelength side is i
A broadband bandpass filter 11 is provided, and the light transmitted through the filter is converted into an electrical signal to read the X-ray image, thereby attenuating the stimulated luminescence light incident from an oblique direction (and improving the reading sensitivity. It becomes possible to improve the performance.

(Embodiment) Next, the configuration and operation of an embodiment of the present invention will be explained in detail using FIGS. 1 to 4.

In FIG. 1(a), a light guide path 1b, a stimulable phosphor plate 3
The device condenses the stimulated luminescence light generated by scanning with excitation light and guides it to the photoelectric converter 2, which is made of a shaped transparent plastic or glass plate, or a bundle of many optical fibers. It is.

The large optical surface 1 a is a surface on which light emitted from the stimulable phosphor plate 3 enters the light guide path 1 . The greater the angle at which this large light surface 1a looks into the stimulable phosphor plate 3, the greater the light collection efficiency becomes.
It is possible to collect a large amount of stimulated luminescence light and increase detection sensitivity.

The light exit surface 1b is a surface from which light exits toward the photoelectric converter 2 from the light guide path l.

The photoelectric converter 2 is a PMT (photomultiplier) or the like,
It converts light into electrical signals.

The stimulable phosphor plate 3 exposes and accumulates X-rays that have passed through the subject.

The excitation light a1gi4 is a laser light generator or the like, and is a light source that emits excitation light for scanning the stimulable phosphor plate 3.

The galvanometer 5 scans the stimulable phosphor plate 3 with excitation light emitted from the excitation light source 4 .

The fθ lens 6 is used to form excitation light into a spot on the stimulable phosphor plate 3 and scan it at a constant speed.

The amplifier 8 amplifies the signal photoelectrically converted by the photoelectric converter 2.

A/D9 is an analog X amplified by amplifier 8.
It converts line image signals into digital X-ray image data.

The image memory 10 stores digital X-ray image data converted by the A/D 9.

The broadband bandpass filter 11 is related to this embodiment, and is used to transmit light having the wavelength of the stimulated luminescence light at the entrance or exit of the light guide path 1 and to transmit the stimulated luminescence light that is incident obliquely. This is a broadband bandpass filter (BPF) that transmits light on the long wavelength side and blocks excitation light (described later with reference to FIGS. 2 to 4).

Here, the operation of the configuration shown in FIG. 1(A) will be explained.

In FIG. 1(a), the excitation light source 4 has a wavelength of 780 mm.
Laser light emitted using a nm semiconductor laser is scanned in a line on the stimulable phosphor plate 3 via a galvanometer 5 and an rθ lens 6. In synchronization with this scanning, the precision fine movement stage 7 is moved in a direction orthogonal to the line scanning, and the entire surface of the stimulable phosphor plate 3 is line scanned. Stimulated luminescent light excited and emitted by line scanning with a laser beam is focused by a light guide path 1 constituted by a large number of glass or plastic fibers, and enters a broadband bandpass filter 11. The stimulated luminescent light that has passed through the broadband bandpass filter 11 is input to the photoelectric converter 2 and converted into an electrical signal. This converted electric signal (analog X-ray image signal) is amplified by an amplifier 8,
Convert to Dizikuru's XvA image data using D9,
It is recorded in the image memory 10. Then, the X-ray image data read from the image memory 10 is subjected to image processing and displayed on a CRT (not shown) or printed as a hard copy.

Next, the improvement in sensitivity by the broadband bandpass filter according to this embodiment will be explained using FIG. 1(b).

In FIG. 1(B), when the stimulable phosphor plate 3 is scanned with excitation light, stimulated luminescence light is emitted in all directions from the scanned point P, for example, as shown by the arrows. In order to collect more of the stimulated luminescence light emitted in all directions, the light guide path
The aperture angle θ for converging light is made as large as possible.

In order to increase this aperture angle θ1, an optical fiber having a numerical aperture as large as possible is used, the light guide path 1 is brought as close to the light emission position P of the stimulated luminescence light as possible, and the light entrance surface 1a of the light guide path 1 is Increase the area of

When the stimulated luminescence light is focused with the largest possible aperture angle θ in this way, a broadband bandpass according to this embodiment is formed between the light exit surface 1b at the exit of the light guide 1 and the photoelectric converter 2. When the filter 11 is provided, the angle of incidence from the light exit surface 1b to the broadband bandpass filter 11 is the illustrated angle θ2.
The stimulated luminescent light that has passed through the broadband bandpass filter 11 at this large angle θ2 is input to the photoelectric converter 2 for photoelectric conversion and converted into an X-ray image signal. At this time, in this embodiment, the wavelength λ of the stimulated luminescence light is used as the broadband bandpass filter 11. It has the characteristics of a so-called broadband bandpass filter (described later using Figure 2 (a)), which transmits the long wavelength side so as to transmit the stimulated luminescence light incident from an oblique direction. Therefore, even if the illustrated angle θ2 becomes large, the light can be transmitted through the broadband bandpass filter 11 and the photoelectric converter 2 can be operated manually, and the sensitivity can be improved.

FIG. 2 shows an example of a broadband bandpass filter according to the present invention.

FIG. 2(a) shows an example of the characteristics of a wideband bandpass filter. The horizontal axis represents the wavelength λ (nm), and the vertical axis represents the transmittance (
%). Incident angles in the figure O°, 20°, 40”, 60
° is the angle of light incident on the broadband bandpass filter 11 from the light exit surface 1b in Figure 2 (b), and i3 at this time
Each represents the characteristics of the error rate.

In FIG. 2(a), the wavelength λ of the stimulated luminescent light emitted from the stimulable phosphor plate 3. For example, if it is 400 nm,
Even if the incident angle to the broadband bandpass filter 11 is within the range of 0° to 60°, or even at a higher angle, the stimulated emitted light can be sufficiently transmitted and extracted. It becomes possible to detect X-ray image signals with high sensitivity. The wavelength of the excitation light is 632.8 nm (He-N
e laser light) and 780 nm (semiconductor laser light), and these lights are blocked by the broadband bandpass filter 11.

FIG. 2(b) shows an example of transmittance. In the figure, a indicates the transmittance obtained by the broadband bandpass filter 11 in FIG. 2 (A) according to this embodiment, and b indicates the transmittance obtained by the conventional narrowband bandpass filter 11 in FIG. 5. As can be seen by comparing these, according to this embodiment, the first
Even the stimulated luminescence light collected from a wide angle range in Figure c) can be detected by passing through the broadband bandpass filter 11, and an X-ray image can be read with high sensitivity from the stimulable phosphor plate 3. becomes possible.

FIG. 3 shows an example of a broadband bandpass filter according to the present invention.

Figure 3 (a) shows the short wavelength cut off edge fi.
This is an optical filter that cuts short wavelength light and transmits long wavelength light.

Figure 3 (b) shows the long wavelength cut off edge fi.
Indicates alter. This is an optical filter that cants long wavelength light and transmits short wavelength light.

These optical filters in Figure 3 (a) and Figure 3 (b) are as follows:
For example, by providing a so-called cavity layer that reflects wavelengths within the wavelength range that is to be blocked, and stacking a number of cavity layers whose blocking wavelengths are slightly shifted, it is possible to block light in a wide wavelength range as shown in the figure. This is how it was done.

Figure 3 (c) shows a broadband band pass filt.
Indicates er. If this is the case, Figure 3 (a) and Figure 3 (b)
It is obtained by stacking optical filters or by stacking two optical filters on one substrate.

As described above, by overlapping the short wavelength cant filter and the long wavelength cut filter, the wavelength λ of the stimulated luminescence light can be adjusted.

It is possible to create a broadband bandpass filter that transmits both wavelengths and wavelengths on the long wavelength side.

FIG. 4 shows an example of a broadband bandpass filter according to the present invention. This is a long wavelength cut off filter
is provided on a glass substrate. In this case, the short wavelength side is absorbed as shown by the dotted line due to the material of the glass substrate (containing impurities), so by providing a long wavelength cut filter on the glass substrate, a broadband bandpass filter is created as a result. be able to.

〔Effect of the invention〕

As explained above, according to the present invention, the wavelength λ of stimulated luminescence light. A broadband bandpass filter 11 that transmits light on the longer wavelength side is provided, and the light transmitted through this filter is converted into an electrical signal. Therefore, stimulated luminescence enters the broadband bandpass filter 11 from an oblique direction. Reading sensitivity can be improved by eliminating light attenuation. This makes it possible to improve the quality of X-ray images.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of one embodiment of the present invention, FIG. 2 is a characteristic diagram of a wideband bandpass filter according to the present invention, FIGS. 3 and 4 are examples of a wideband bandpass filter according to the present invention, and FIG. 5 shows an example of a conventional narrowband bandpass filter. In the figure, l is a light guide, 1a is a light entrance surface, 1b is a light exit surface, 2 is a photoelectric converter, 3 is a stimulable phosphor plate, 4 is an excitation light source, 1
0 represents an image memory, and 11 represents a broadband bandpass filter.

Claims (1)

[Scope of Claim] A radiation image information reading device that collects stimulated luminescence light emitted by scanning a stimulable phosphor plate with excitation light and converts it into an electrical signal, comprising: a stimulable phosphor plate ( 3) is scanned by excitation light to condense the stimulated luminescent light generated, and a light guide (1) that transmits and obliquely transmits light of the wavelength of the stimulated luminescent light at the entrance or exit of the light guide (1). In order to transmit the stimulated luminescence light incident from the stimulated luminescence light, the broadband bandpass filter (11) transmits light up to a wavelength longer than the wavelength of the stimulated luminescence light and blocks the excitation light. filter(
11) A radiation image information reading device characterized in that it is configured to convert stimulated luminescence light taken out through an electrical signal into an electrical signal and read X-ray image information or the like.