JPS6025200A - Automatic exposure-compensating circuit in panorama x-ray photographic device - Google Patents

Abstract

PURPOSE:To prevent any excessive feed back control so as to improve the quality of picture images by obtaining a compensation signal when a sensor plunges into a special region by measuring the amount of X-rays transmitted by a photographed subjected and detecting the plunge of the sensor into the special region according to a signal produced by the sensor. CONSTITUTION:In a panorama X-ray photographing device, X-rays transmitted by a photographed subject 17 and a film 4 are detected by a sensor 7 before being fed back to the driving circuit (A) of an X-ray tube 3 through a compensating circuit 18 and comparing means 13 and 14. The compensating circuit 18 consists of a circuit 20 for detecting the plunge of the sensor 7 into special regions having bone breakage or containing metallic members, and an analogue multiplexer 19 for selecting the output signal of the circuit 20 and a sensor signal. When a signal is sent from the circuit 20, the multiplexer 19 is switched and a compensation signal is formed. As a result, clear picture images can be obtained by maintaining the degree of exposure at a constant level by avoiding excessive feed back control during the time when the sensor 7 plunges into special regions.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a panoramic X-ray imaging device, especially an X-ray device for dental diagnosis.
The present invention relates to an automatic exposure compensation path in a line photography device.

The quality of an X-ray photograph obtained with an X-ray photographing device is determined by the metric properties of the subject and the balance between the tube current and tube voltage of the X-ray tube, and the degree of darkening on the X-ray photograph side. (concentration ratio). In particular, with X-ray imaging equipment used for panoramic imaging in dental diagnosis, the amount of X-rays that reach the film differs depending on the differences between adults and children, gender, or the same subject, such as the anterior teeth and small/molar areas. As a result, even if good contrast is obtained in one part of the film, the degree of blackening in other parts of the film deviates significantly from the optimum value, resulting in a situation where good contrast cannot be obtained.

To solve this problem, the automatic exposure mechanism usually detects the amount of X-rays remaining transmitted through the X-ray film and the subject, and feeds back this information to control the tube voltage or tube current of the X-ray tube. .

By the way, the sensor that detects the amount of transmitted X-rays during this X-ray photography scans the area under the eyes of the person to be photographed.

This is because it is naturally predicted that in the dental arch, a metal crown as a prosthesis is attached to the tooth, and the presence of this metal crown will avoid a significant change in the transmitted X-ray detection value of the sensor. It's for a reason. Figure 1 (al) shows the standard pattern of this sensor output signal waveform. If there is a section where a prosthesis is attached, and Senna is applied to the affected bone defect or 911 special part of the metal attachment, the Senna output will be as shown in Figure 1 [
b) (state affected by bone defect), Fig. 1 (a) state affected by metal attachment) shows a sudden change as shown in Fig. 1, and excessive feedback control is applied. , the image on the film becomes slightly pale (Blue Fire 4t'l)
(metallic attachments), and even in the case of h displacement, it is not recommended for examination 1v1.. (i. I had no choice but to take pictures using Maenial operations.

Therefore, the purpose of this invention is to treat people with bone defects or metal attachments, as well as people with special bone structures (
For example, the user 111 can take excessive feedback control h1 (suppressing 1 and equally self 1) even for a person with a particularly large face).
Provides 1J exposed ura compensation circuit.

That is, the present invention detects the remaining amount of X-rays transmitted through the subject using a sensor and returns this to the X-ray tube to automatically control exposure, in which the above-mentioned senna output signal and this senna are An output circuit is provided to selectively feed back a compensation signal when the Senna enters a special part, and a circuit is provided to detect entry into the special part from the amount of change in the output signal of the Senna, and the detection signal of this detection circuit causes the output to be The present invention is characterized in that it is an automatic exposure compensation circuit in a panoramic X-ray imaging apparatus that sends out a compensation signal from the circuit.

According to this invention, excessive feedback control can be avoided when the sensor enters a special site such as a bone defect, and the exposure of the special site can be kept constant using a compensation signal.
It has now become possible to automatically take X-ray images of images that are clear enough for diagnosis even on subjects with metal attachments.

The details of this invention will be described below using a preferred embodiment configuration.

Figure 2 shows the basic structure of the feedback system of a panoramic dental X-ray imaging device.T1 block (a) is an X-ray tube driver circuit and a feedback control circuit, which includes a power supply (9) and an X-ray tube (3). is connected, the X-ray remaining amount sensor 1#'' (7) is detected through the person (17) and the X-ray film (4), and this is detected by the compensation circuit fl16 and the comparison means (131 (7)) according to the present invention.
141 to the above-mentioned block (Al).Furthermore, a specific example of such a feedback system is explained using Figure I!8, which includes a high voltage transformer (1), a filament transformer (2) ), and the high-voltage equipment of the X-ray tube (3) are housed in the X-ray irradiation head.A photoelectric conversion device that corresponds to this head and outputs an electrical signal corresponding to the luminance of the fluorescent plate (5)!1. 6) is provided, and this etc. (5)
(Is) constitutes the aforementioned senna (7). (8) is amplification! This is a circuit that amplifies the sensor output with I (8b). On the other hand, on the head side, a high voltage transformer (1
) and the negative side of the filament transformer (2) are each connected to the AC power supply (9) via a power on/off switch (IJ), and a feedback control transistor is connected to the negative side of each. (111i12 is provided,
Feedback control transistor fill (by changing the base bias (conduction angle) of 13, high voltage transformer (1),
Feedback control is applied to the filament transformer (2).

Therefore, the output of the amplifier circuit (8) is sent to both the tube voltage control comparator (to) and the tube current control comparator (141), and these comparators (1m) adjust the pace bias at 141. (1!1l (1! is the setter for the above reference signal.

In this circuit, first, the optimum relationship ratio between the tube voltage value and the tube current value is determined. For example, when the tube voltage is 60KVO, the tube current is 5! So that the music flows, f3 Q KV again.
In this case, a circuit is manufactured by setting the tube voltage value and tube current value in a certain correspondence relationship so that 10 nm is lost, and the reference signal setting device (15+(1η) is adjusted. This relationship ratio is based on clinical data.

In operation, as the X-ray tube (3) is activated, the X-rays pass through the teeth of the subject (171) and expose the film (4), forming an image of the teeth on the limb film (4). Therefore, the optical 'ill conversion device (6) outputs a signal corresponding to the X-ray intensity, and this is sent as a sensor output to the comparator (13+141) via the amplifier circuit (8). Compare this value with the value predetermined by the reference signal setter f+51 (Iω, and set l'il Rf so that they match.
The pace bias of the i control transistor 11υf17J is changed to radically drive the high voltage transformer (1) and filament transformer (2). Thus, both the tube voltage and tube current of the X-ray tube (5) are simultaneously #fc feedback controlled.

In such automatic calculation circuit 1.13, the compensation circuit f18) t, the amplifier circuit (8) and the comparator f according to the present invention
Equipped between 131 and 141. The circuit in Figure 4 is the details, and it is fil! Explaining this using the time chart in Fig. 5, the present invention consists of a circuit (analog multiplexer in the figure) (II in the figure) that selects and outputs a sensor output signal and a compensation signal as described below, and a sensor (7) in a special part. The senna output signal [Figure 5 (a)
In addition to being sent to the analog multiplexer, the signal ll is input to the detection circuit (2) in three branches. That is, the differentiating circuit (21) captures the temporal change in the senna output signal (a) as shown in FIG. Only when the amount of change exceeds the voltage vref, that is, when the amount of change is large, is extracted as shown in FIG. 5 (0). Also, the senna output signal (
all enters the saturation voltage detection circuit (for example, composed of a window comparator) t23, and 4a-'FJ at the time when the saturation level Lmax, I, min of the (ET 9 (al) has been reached is extracted. ) 3% In this case, the saturation level refers to the peak 1rnay and the minimum level i, min of the sensor output.Thus, the AND circuit of the signal (Q) and the signal (dJ) is taken. Therefore, among the signals (01) and (02) with a large amount of change extracted in FIG. However, for (02), l + nin at this point
Since the corresponding saturation voltage is detected, the AND circuit
outputs the signals shown in Fig. 5 (e, l), and this outputs the signals of sensor (7).
) is detected to have entered a special part of the photographed person (1η).In the case of Fig. 5, the special part is caused by a metal attachment, but it is detected in the same way even if it is a special part caused by a bone defect. This special part entry signal (6) is sent to a memory (for example, a bistable multivibrator) (2) and a sample-and-hold circuit (a), and the memory (c) stores the special part entry point and also outputs the signal shown in #X5. (The output of f7 is sent to the AND circuit (A). The sample and hold circuit (A) passes the sensor output signal J! The circuit (branch) as a kind of analog signal memory enters a special part (
? The signal at the level immediately before entering the special part at No. I (-3, that is, the compensation signal [Fig. 6) is sent to the multiplexer (11. At the same time, the signal (d) and (f) Switching signal by logical product [61st g (g)
) is also sent to multiplexer +11.

In the multiplexer (11), in the normal state, the senna output signal (j1) that enters directly is selected and sent as is to the comparators f131 and f14, but when the switching signal (g) is input, Compensation Select No. 16 (hl), send it to the comparator (13 + 141 K'', compensate the senna output signal within the saturation range 11 as shown in Figure 13, and force excessive feedback control. This compensation value level is the level immediately before entering the special area.Although this explanation describes the case where the special area only appears once during imaging, the book (circuit) The structure is such that compensation will be provided each time there is hail.

@The circuit shown in Figure 4 is a sample hold circuit (a) as shown above.
The signal level immediately before entering the special part is stored, and this is used as the compensation value level of the compensation signal (h).This compensation value level is set in advance, and when entering the special part, this compensation signal may be output from the multiplexer t<11. This circuit is shown in Figure 6.
The memory □□□ memorizes that the senna (7) has entered the special part, and sends the inrush signal to the AND circuit (A), and the multiplexer (II has a compensation signal % V (10
is always given, and this compensation signal 97oora is selectively output by the output of the AND circuit (2) upon entering the special portion.

In addition, this compensation signal yaom is always sent to a multiplexer (I
A sensor 11g2 is provided to detect a special part separately from the sensor (7), and a compensation signal veom is given by the special part detection operation by the sensor, and this is used as the output signal of the AND circuit diagram. FIG. 7 shows a circuit diagram for this purpose.

[Brief explanation of the drawing]

FIGS. 1(a), 1(b), and 1(0) show each pattern of the senna output signal, and are for explaining the technical problem of the present invention. FIG. 2 is a schematic diagram showing the basic configuration of the feedback system. FIG. 3 shows a specific example of the 81st circuit. ! Figure 4 is a circuit diagram of an embodiment of Jin's invention. FIG. 5 is a time chart of the circuit of FIG. 4. FIGS. 6 and 7 are circuit diagrams showing modified examples of the present invention, respectively. C code explanation) (3)...X-ray tube, (4)--X-ray film, (7)
... No. 17, O9 --- Output circuit (multiplexer)
, (to)...detection circuit. -End- Attorney Patent Attorney (6285) Hidehiko Matsuno BA544-

Claims (1)

[Claims] (1) In a device that detects the remaining amount of transmitted X-rays of the subject using a sensor and returns this to the X@tube to automatically control exposure, the above sensor output signal and this sensor An automatic exposure compensation circuit for a panoramic X-ray imaging apparatus, which is provided with a circuit for generating a compensation signal when the temperature reaches 6t, and sends out a compensation signal from the output 1m path based on the detection signal of this detection circuit.