CN1060161A - Slit radiography apparatus - Google Patents

Abstract

A kind of narrow slit X-ray photographic apparatus is made up of a kind of absorption device.These parts are connected with a slit diaphragm.Absorb device and be made of electronically controlled piezoelectric reed, control assembly provides control signal to piezoelectric reed.Receive the control signal that is used to control these reeds for each piezoelectric reed by damping device.For each reed, this device comprises an emf measuring circuit.And when work, provide an output signal to represent the back electromotive force that produces by corresponding reed.The signal combination of the piezoelectric reed that these corresponding output signals are relevant with control is eliminated the free vibration of reed.

Description

Slit radiography apparatus

The present invention relates to a kind of slit radiography apparatus, this device comprises an absorption device that is connected with slit diaphragm, and this device comprises electronic controlled piezoelectric reed, and this device also comprises a control device, and this device provides control signal for piezoelectric reed.

Deutsche Bundespatent (application number No.8400845) provide a kind of device, this device comprises an x-ray source, this x-ray source can scan to the patient or the object of receiving check with a kind of flat fan-shaped X beam by a slit diaphragm, in order to obtain uniform radioscopic image: near slit shape diaphragm, be provided with one and absorb device, this device is made up of the absorber element of a plurality of placed adjacent, and these elements can be inserted into X-ray beam in varying degrees under the control of electric control signal.

Each absorber element can influence a sector of fan-shaped x-ray beam.The detector of the back by being placed on patient or object can obtain control signal.This detector can be measured the radiation dose of the X-ray beam of each sector, and appropriate electric control signal is provided.

With regard to absorber element, the reed that adopts piezoelectric to make is better, reed one end is clamped fixing, and the other end can rotate into X-ray beam under the control of above-mentioned electric control signal.Itself can absorb a certain amount of X-radiation these reeds, and, also can place the particular components that absorbs X-radiation at its free end.

These reeds can be the simple reeds that adopts piezoelectric, make it form crooked shape by the control voltage that is added on its upper and lower surface.

These reeds also can be so-called twin crystal elements.This element by two up and down the two-layer piezoelectric that stacks constitute, control voltage is added on two above the lateral surface between (be end face and bottom surface, their electric short circuits are together) and the central common sides.

Concerning these reeds, importantly to be swift in response and accurately to electric control signal.But have been found that resonance effect may take place these reeds.Its result makes these reeds out of hand even be directed at its fracture.Can prevent this free vibration for the method for control signal filtering although adopt,, adopt this wave filter still can cause the control of these reeds slow.

So, just need a kind of equipment to stop this vibration of the piezoelectric reed in the narrow slit X-ray photographic apparatus with effective and efficient manner.Keep of the rapid reaction of these reeds simultaneously to control signal.

In order to reach this purpose, according to the present invention, the feature of the device of described type is that it has this device of a damping device (damping devive) to receive the control signal of reed, and comprising electromotive force (EMF) metering circuit that is used for each reed, this circuit also interacts with reed.When work, this device provides the output signal of a representative by the back electromotive force of reed generation.This signal combines with the control signal of relevant reed.

It is to be noted, European patent (application number No.0,155,065) method of the vibration of the various reed type carriers that come damping reed type absorber element or absorber element by means of the modes that produce eddy current in mechanical system or the metal blade on being attached to reed has been described.But these technique known also are not suitable for the reed of piezoelectric.These reeds are quite crisp and also need suitable exceptional space in absorbing device in addition.

The present invention will obtain more detailed description by the accompanying drawing with reference to the property of the following describes embodiment.

The side view that has shown to Fig. 1 diagrammatic an example of the narrow slit X-ray photographic apparatus that constitutes by the absorption device.

The side view that has shown to Fig. 2 diagrammatic an example of the piezoelectric reed that constitutes by absorber element;

Fig. 3 adopts the form of block scheme to show that how controlled piezoelectric reed is according to the present invention; And

Fig. 4 has shown an illustrative embodiment of the part of Fig. 3.

The side view that has shown to Fig. 1 diagrammatic an embodiment of the known narrow slit X-ray photographic apparatus that constitutes by the absorption device, this device that shows comprises an x-ray source 1, this radiographic source can scan wanting checked patient or object by slit-type diaphragm 2 direction along arrow 5 indications in the plane vertical with fan-ray beam 3.An X-ray detector 6, it can comprise the X ray picture image intensifier tube of an X-ray film box or a prolate that is synchronized with the movement, be used to pick up pass the patient ray to form required X ray image.When work, x-ray source sways along direction as shown in arrow 7, and X-ray beam is scanned along the direction shown in the arrow 5, and above-mentioned axle preferably passes through the focus of the X ray of x-ray source perpendicular to figure plane.

In order to obtain uniform radioscopic image, adopted a kind of absorption device 8 that can regulate the X-ray beam of each sector, this device is made of the piezoelectric reed of placed adjacent, piezoelectric reed also is called piezoelectric ceramic piece by people, because they are to be the example of this reed by the shown in Figure 2 of the stupalith manufacturing with piezoelectric property, each reed can influence a specific region of X ray stream 3, therefore, one end of reed is fixed, X ray stream is inserted in reed bending when suitable electric signal is provided to reed, the free end of having as a result.Required control signal is provided by detector 9.In this example, detector 9 is used to pick up the electric signal that passes patient's X-radiation constantly and the X-ray beam of each sector is provided at each between patient and X-ray detector.This electric signal is added to corresponding reed by treatment circuit 10.As shown in the figure, this detector can be the ray detector of the prolate that is synchronized with the movement with X-ray beam, also can be the static detector of bidimensional.

Fig. 2 is a kind of side schematic view of twin crystal type piezoelectric ceramic piece 11, and it comprises two the piezoelectric thin slices 12 and 13 that stack mutually.Shown thin slice in this example, also provides an absorber element at its free end fixing in carrier 14 near the one end.Intermittent line has been represented the working position that it is possible.Reed is by the control Control of Voltage, and in when work, control voltage is added between two terminals 16 and 17, wherein an end be connected in thin slice 12 and 13 between central surface 18.The other end is connected in the lateral surface 19,20 of two thin slices.

Fig. 3 has shown the block scheme of the control circuit of piezoelectric reed by way of example.

The present invention according to principle be, piezoelectric reed produces a back electromotive force in when work, its size depends on that the degree of crook of reed just can draw the antihunt signal of a corresponding reed from back electromotive force, to prevent the resonance effect of reed.

According to the present invention, the back electromotive force of each reed is constantly detected.Subtract each other by the processing back control signal of giving that instantaneous back electromotive force electric signal that obtains and the process of being supplied with reed by detector 9 are possible.These obtain explanation by Fig. 3.At work, after the control signal process that is provided by detector 9 is given processing.The input end 31 of the control circuit 30 shown in appearing at.This signal is sent into amplifier 33 by feedback point 32.The output signal of amplifier 33 is sent into electromotive force testing circuit 34(and below will be described in detail).Electromotive force testing circuit 34 is coupled to the piezoelectric reed of representing with the frame 35 of figure signal among Fig. 5.In addition, the electromotive force testing circuit form (will explaining in detail later on) depend on in the signal of the moment of relevant reed back electromotive force, and pass through feedback amplifier 36 negative feedbacks to feedback point 32.

Back electromotive force depends on the motion of reed, and makes control circuit 30 form a kind of so-called dynamic feedback system.

According to the present invention, represent the feedback signal of the back electromotive force of reed to obtain during operation by means of the circuit of the type among Fig. 4 for example.

What Fig. 4 showed is the bridge circuit that 4 40-43 of branch are arranged.Branch 41 comprises two interfaces 44,45, and they are connected in controlled reed 46 when work.Branch 42,43 all comprises a resistance R, and the resistance of this resistance is desirable 10K Ω in actual conditions.

Suppose the element Q of its characteristic corresponding to a clip is connected in the branch road 40 of bridge circuit, the back electromotive force that this bridge circuit can be used for measuring reed 46 is for this purpose, and the output signal that amplifier 33 provides is sent in the interface of summit 47(branch road 40 and 41) and the interface of 48(branch road 42 and 43) between.This signal is also controlled reed 46.Between the other summit 49 and 50 of bridge circuit, produce feedback signal in order to the back electromotive force of reflection reed 46.This signal is admitted to differential amplifier.This amplifier is equivalent to the feedback amplifier 36 among Fig. 3 or thinks be configured in its circuit.

Element Q can be a capacitor because piezoelectric ceramic piece be substantially have capacitive.But, had better adopt the piezoelectric ceramic piece similar as element Q to the reed that will control.But the reed as element Q will be completely fixed, and makes its not reason motion and produce back electromotive force.So the signal that manifests between the summit 49 and 50 all is the back electromotive force of reed 46.As pointing out, since reed has capacitive character, and the other branch road 43,43 of bridge is revealed as resistance R in this example, and the output signal of bridge and the input signal of differential are proportional.So the movement rate of feedback signal and reed 46 is proportional.By this feedback signal, the motion of reed is well controlled.Reed is guaranteed to the rapid reaction of control signal simultaneously.

Should be pointed out that by above disclosure for those skilled in the art person, various modifications are conspicuous, for example, the resistance R in bridge circuit can be replaced by capacitor.In this embodiment, the output signal of bridge is not proportional with movement rate, but proportional with its time integral.That is to say with reed free-ended depart from proportional.This and similar modification all is considered as falling into scope of the present invention.

Claims (6)

1, a kind of narrow slit X-ray photographic apparatus, constitute by a kind of absorption piece, these parts are connected with a slit diaphragm, and comprise automatically controlled piezoelectric reed, with a control assembly, these parts provide the control electric signal for each reed, it is characterized in that: receive described control signal by a kind of damping device, this device comprises the emf measuring circuit that is used for each reed, and interact with it, these parts provide the output signal of the expression back electromotive force that reed produces when work, this signal is combined with the control signal of control piezoelectric reed.

2, device according to claim 1, it is characterized in that the damping unit that is used for each reed comprises a control circuit, this circuit has the input end and the feedback point that are used for the control signal of relevant reed, the output signal of sending from emf measuring circuit by feedback amplifier by negative feedback point so far, also has an amplifier that output signal is fed to the input end of emf measuring circuit from feedback point, in circuit, testing circuit also provides damping control signal for reed.

3, device according to claim 1 and 2, it is characterized in that, emf measuring circuit comprises a bridge circuit, this circuit has parallel the passing through of two covers and exports the bridge branch road that link is together in series, its output terminal links together, and the first cover bridge branch road has the first bridge branch road, and it comprises an element and second a bridge branch road of representing the electrical characteristics of piezoelectric reed, it comprises a resistance, and the second cover bridge branch road comprises the 3rd a bridge branch road that the reed that will control is arranged.With the 4th bridge branch road that comprises a resistance.

4, device according to claim 3 is characterized in that, the element of representing the piezoelectric reed electrical characteristics is a capacitor.

5, device according to claim 3, it is characterized in that representing the element of the electrical characteristics of piezoelectric reed is a fixing piezoelectric reed.

According to the described device of claim 3 to 5, it is characterized in that 6, the 2nd and the 4th bridge branch road comprises a capacitor that replaces resistance.

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