JPH0481176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation image reading device that reads a radiation image recorded on a stimulable phosphor by scanning the stimulable phosphor with excitation light.

Conventionally, in order to read a radiation image from a storage phosphor (hereinafter simply referred to as a phosphor), it has been essential to irradiate the phosphor with excitation light. When reading, the reflected light of the excitation light irradiated to the phosphor is scattered inside the device,
Alternatively, light from outside the device may leak into the device. As mentioned above, since the emitted light from the phosphor and the reflected light from the excitation light or leaked light into the device are present inside the device, the emitted light and the reflected light or leaked light are simultaneously incident on the photodetector. However, the photodetector outputs a signal that is completely different from the originally required image signal due to the light emitted from the phosphor. Until now, in order to compensate for the drawbacks of the above-mentioned devices, there has been a method of removing reflected light by disposing a filter on the incident surface of the detector, but in this method, the transmittance of the filter is lower than that of the reflected light. On the other hand, if there is no zero, reflected light will enter the photodetector, albeit weakly. Alternatively, if the leaked light itself contains a component equivalent to the emitted light, the filter will not function for this component. As mentioned above, it is impossible to guide only the light emitted from the phosphor to the photodetector for signal processing with the conventional configuration using only a filter, and the reproduced image obtained from the signal by this method is The resulting image was completely different from the image produced by the emitted light.

In view of the above-mentioned points, the present invention has been made for the purpose of effectively separating the signal output from a photodetector into a signal due to light emitted from a phosphor and a signal due to light other than the emitted light. It is something.

Such an object of the present invention is to provide a radiation image reading device that scans a phosphor with excitation light and reads a radiation image recorded on the phosphor, in which at least a stimulable window phosphor is obtained by irradiation with excitation light. a photodetector that receives light from the phosphor and light from the reflective part having uniform reflectance and converts it into a signal; and from the signal of the photodetector, the light from the phosphor and the light from the reflective part This can be achieved by a radiation image reading apparatus having a signal processing section configured to output a signal corresponding only to the stimulated luminescence light from the phosphor. In particular, it is desirable to use a part of the phosphor material or a diffuse reflection material exhibiting the same reflection characteristics as the phosphor material as the reflecting part, and the light from the phosphor is collected and the light is detected. A light-concentrating conductor is disposed between the phosphor and the photodetector to guide the focused light to the phosphor, and an optical path is provided to guide the light from the phosphor to the photodetector. A good effect can also be obtained by inserting a filter that blocks the excitation light component therein. Alternatively, the photodetector is a photodetector that receives light from the phosphor and converts it into a signal;
The light detector may be divided into a photodetector that receives light including reflected light from the reflecting portion and converts it into a signal. Hereinafter, some embodiments of the present invention will be described based on the drawings.

First, FIG. 1 is an example of a schematic configuration diagram of the present invention. In Figure 1, the diffuse reflection plate 1a is 1
It shows the same reflection characteristics as the phosphor plate coated with the phosphor of b. A filter 1c has a characteristic of attenuating only excitation light such as a laser beam. Now, the excitation light emitted from a light source (not shown) scans the diffuse reflection plate 1a and the phosphor plate 1b in the main scanning direction (indicated by the self-arrow), and the reflected light from the reflection plate and the light from the phosphor are passes through a light-collecting conductor 1d having a light-receiving surface extending along the main scanning direction, and a filter 1c, and enters a photodetector 1e using, for example, a photo sensor. After the signal is converted into an electrical signal, it is input to the signal processing section 1f. By moving the diffuse reflection plate 1a and the phosphor plate 1b in the direction of the arrow, the excitation light can scan the entire surface of the phosphor plate 1b.

However, light from outside the device, leakage light from the junction between the filter 1c and the photodetector 1e, and reflected light components of the excitation light from the phosphor plate 1b are incident on the light condensing conductor 1d. As a result, light other than the light emitted by the phosphor is incident. Then,
A signal processing section 1f separates only the light emitted from the phosphor and generates an image output signal.

An example of the configuration of the signal processing section 1f is shown in FIG.
The timing charts are schematically shown in FIG. In the first scan, the excitation light first scans the diffuse reflection plate 1a, but when scanning the diffuse reflection plate 1a, the light incident on the photodetector 1e is the incident light of the excitation light, the leakage light, etc. The light other than the light emitted from the phosphor is detected by the photodetector 1.
It is converted into an electrical signal at e, and outputted through an amplifier 2a and a comparator 2b. Since the switches S ₁ , S ₂ , and S ₃ are open, _{S 2 is} closed, and S ₃ are closed at the above-mentioned time point, the light emission is performed by the holding circuit 2c, such as a conventionally known sample-and-hold circuit. Analog values corresponding to light other than light are held. When the scanning period of the phosphor plate 1b continues, S ₁
closed, _S2 open, and _S3 open, and the signal value of the holding circuit 2c is input to the negative input terminal of the comparator 2b.
When the phosphor plate 1b is scanned by this operation, the difference between the signal value corresponding to the light from the phosphor plate 1b of the photodetector 1e and the signal value due to light other than the emitted light is obtained as an output. It will be done. Will comparator 2b
In other words, the output of the signal processing section 1f is obtained by removing influences other than the emitted light. The control circuit 2d in FIG. 2 controls the operation of the signal processing unit 1f, and may be unique to the signal processing unit 1f, or may be common to the control circuit of the radiation image reading device. It may be. With this, the first scan is completed, the next scan begins, and the above-described operations are repeated.

FIG. 3 shows the signal waveform at each point when reading an image using the configuration shown in FIG.

Here, among the symbols in Fig. 3, 3a and 3a'' are diffuse reflector scanning periods, 3b' and 3b are phosphor plate scanning periods, 3c' and 3c are invalid periods, and 3d and 3d'' are 3e and 35'' are sample periods, and 3f', 3f, and 3f'' are hold periods.

Now, the signal waveform at point ○ in Figure 2 where the output of the photodetector has been amplified is shown by the input signal 3 in Figure 3.
Analog output by fluorescent light emission corresponding to the radiation image on the phosphor plate is obtained during the section b, 3b'', and the output when scanning the diffuse reflector plate, which is the reference, is 3 in the waveform of ○a.
This output is sampled and held in the period shown by 3e, 3e" of the holding circuit control signal ○b, and appears in the output waveform of the holding circuit output 3d, 3d" shown by ○c. It turns out.

Therefore, in order to subtract this output 3d, 3d'' from the input signal, it is input to one terminal of the comparator 2b, and the output of the comparator 2b, that is, the output signal of the signal processing section 1f, is the original radiation as shown in ○D. An output waveform of only the fluorescent light corresponding to the image is output.

Furthermore, in the example shown in Fig. 2, the signal is held in the holding circuit 2c as an analog value, but the analog value is once converted to a digital value, the signal value is held, and then converted to an analog value as necessary. You may also do so.
Furthermore, in the above example, the signal value for light other than the light emitted from the phosphor is held once per scan, but it may be held once per multiple scans or once per phosphor plate. You can also do this.

FIG. 4 shows another embodiment of the signal processing section. The excitation light first scans the diffuse reflection plate 1a,
The output of the photodetector 1e during the scanning corresponds to the filtered afterglow of the excitation light and the leaked light, and after being amplified by the amplifier 4a, it is held in the holding circuit 4b. While scanning the fluorescent plate 1b, the output of the holding circuit 4b is input to the zero adjustment terminal of an A/D converter (analog/digital converter), and the A/D converter adjusts the fluorescent light. body plate 1b
By calculating the output of the light from the phosphor and the output of the holding circuit 4b, it is possible to remove the influence of light other than the light emitted from the phosphor.

Further, FIG. 5 shows another embodiment of the signal processing section. The output of the photodetector 1e passes through the amplifier 5a to the A/
It is converted into a digital value by the D converter 5b. The digital value while scanning the diffuse reflection plate 1a is held in the holding circuit 5c, and when scanning the phosphor plate 1b, the digital value of the output by light from the phosphor plate 1b and the holding circuit 5c are stored. The digital value held in the phosphor is calculated and outputted by the calculation circuit 5d, thereby making it possible to eliminate the influence of light other than the light emitted from the phosphor.

In addition, in the above-mentioned figures 4 and 5, 4d,
5e is a control circuit that controls the operation of each signal processing section, and may be unique to each signal processing section, or may be common to the control circuit of the radiation image reading device. Further, the timing of holding in the holding circuit may be once for each scan, once for multiple scans, or once for each release of the phosphor plate.

In the above embodiment, the diffuse reflection plate was provided next to the phosphor plate in a direction perpendicular to the direction, but the diffuse reflection plate was provided in a direction parallel to the scanning direction of the phosphor plate to begin reading the phosphor plate. The diffuse reflection plate may be scanned beforehand and input to the holding circuit (see FIG. 6). Alternatively, a certain part of the phosphor plate may be used as an input to the holding circuit (see Figure 7), and a photodetector that detects the light from the phosphor plate and a light detector that detects the light from the reflective part. The detector may be independent (see FIG. 8). The signal processing section in the above case is as shown in FIG.

As described above, by using the device of the present invention, it is possible to effectively separate the stimulated luminescent light on the phosphor and light other than the luminescent light, and the radiation on the phosphor can be effectively separated. An image signal that is faithful to the image can be obtained.

[Brief explanation of drawings]

Figure 1 is a diagram showing the configuration of an embodiment of the present invention, in which a diffuse reflection plate is placed beside a stimulable phosphor along the sub-scanning direction indicated by the arrow, and is read by a single photodetector. It is. FIG. 2 shows an example of the configuration of the signal processing section, and FIG. 3 shows a timing chart of signals in the signal processing section. FIG. 4, FIG. 5, and FIG. 9 show other embodiments of the configuration of the signal processing section, and FIG.
7 and 8 show modified examples of the configuration of the present invention. 1a... Diffuse reflection plate, 1b... Accumulative phosphor plate, 1
c... Filter, 1d... Light condensing conductor, 1e, 8
e, 8e′...photodetector, 1f, 8f...signal processing unit,
2a, 4a, 5a, 9a, 9a'...Amplifier, 2b,
9b...Comparator, 2c, 4b, 5c, 9c...
Holding circuit, 2d, 4d, 5e, 9d...control circuit,
4e, 5b...A/D converter, 5d... Arithmetic circuit.

Claims (1)

[Scope of Claims] 1. In a radiation image reading device that scans a stimulable phosphor with excitation light and reads a radiation image recorded on the stimulable phosphor, at least a photodetector that receives light from the stimulable phosphor and light from a reflecting portion having a uniform reflectance and converts it into a signal, and detects the light from the stimulable phosphor and the reflection from the signal of the photodetector A radiation image reading device comprising a signal processing section configured to output a signal corresponding only to the stimulated luminescence light from the stimulable phosphor by comparing the light emitted from the stimulable phosphor. 2. The radiation image reading device according to claim 1, wherein a diffuse reflection material exhibiting reflection characteristics equivalent to that of a stimulable phosphor material is used as the reflection portion. 3. The radiation image reading device according to claim 1, wherein a portion of a stimulable phosphor material on which a radiation image is not formed is used as the reflecting portion. 4. The photodetector includes a photodetector that receives light from the stimulable phosphor and converts it into a signal, and a photodetector that receives light including reflected light from the reflection section and converts it into a signal. A radiation image reading device according to any one of claims 1 to 3, characterized in that the radiation image reading device comprises: 5. A light-concentrating conductor is provided between the stimulable phosphor and the photodetector so as to collect the light from the stimulable phosphor and guide the focused light to the photodetector. A radiation image reading device according to any one of claims 1 to 4, characterized in that a radiographic image reading device is provided. 6. Claim 1, characterized in that a filter for blocking an excitation light component is inserted in an optical path that guides light from the stimulable phosphor to the photodetector.
6. The radiation image reading device according to any one of items 5 to 5.