JPH09238284A - X-ray photographing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust light quantity within short time without a change in a picture characteristic and to improve reliability at the time of operating for plural times by providing more than one optical diaphragms and liquid crystal filters. SOLUTION: An X-ray source generating an X-ray, an image intensifier (I.I) 101 converting the X-ray passing through a subject into a visible image, an X-ray television camera 107 which image-picks up the visible image and a light quantity adjusting means which is laid between I.I 101 and the X-ray television camera 107 and adjusts the light quantity of the visible image in I.I. 101 are provided. The light quantity adjusting means has more than one optical diaphragms 105 and liquid crystal filters 1. Since optical diaphragm diameters for respective visual fields in I.I. 101 are always constant, the stable image characteristic can be obtained. Since re-adjustment is not required in the optical diaphragms 105 when sensitivity by the visual field is corrected, adjusting time can be shortened. The reliability of the liquid crystal filter 1 can be improved without the need of mechanical driving.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray imaging apparatus, and more particularly to an X-ray imaging apparatus for picking up a visible image output from an image intensifier by an image pickup means.

[0002]

2. Description of the Related Art Conventionally, in an X-ray imaging apparatus using an image intensifier (hereinafter referred to as II), the I.I. I. Output light (visible image) of X
An optical diaphragm (auto iris) was used as a light amount adjusting means when transmitting to a line television camera.

In recent X-ray radiographing apparatuses, various fluoroscopic / radiographic methods (for example, continuous fluoroscopy, pulse fluoroscopy, low dose mode fluoroscopy, high dose mode fluoroscopy, DA (Digital Angiog) are available.
raphy), DSA (Digital Subtraction Angiogra)
(Phy) shooting, etc.), a combination of an optical diaphragm (iris) and an ND (Neutral Density) filter is used for shooting in order to widen the dynamic range that is a range that enables appropriate shooting.

FIG. 4 shows the I.D. I. It is a conceptual diagram which shows the relationship between an optical system, and an X-ray television camera.

As shown in FIG. 4, the X-rays emitted from the X-ray tube (not shown) onto the subject are I.D. I. The incident dose R is incident on 101. I. I. The output light of 101 is I.I. I. Lens 102, first ND filter 103, second ND filter 104, and optical diaphragm (iris) 105
The incident light amount F is incident on the X-ray television camera 107 via the television lens 106 and the television lens 106. In addition, 103a, 1
04a is the first and second ND filters 103 and 1 respectively.
This is a solenoid for inserting / removing 04 into / from the optical path.

By the way, in the structure shown in FIG. 4, I.V.
I. There are two types of light amount adjustment, which are associated with the switching of the field of view, and the light amount adjustment which is associated with the difference in the above-mentioned imaging method.

However, conventionally, the roles of adjusting the light amounts of the optical diaphragm 105 and the first and second ND filters 103 and 104 are not clearly distinguished, so that the optical diaphragm 105 is not distinguished.
When the amount of light is too large to be adjusted by, the first and second ND filters 103 and 104 are individually or simultaneously inserted in the optical path, and the optical diaphragm 105 is readjusted according to the inserted state.

Here, the incident light quantity F of the X-ray TV camera is expressed by the following equation.

F = R · G _X · T _L · T _I R = I. I. Incident dose on the light source G _X = I. I. Conversion coefficient T _L = I. I. Composite transmittance of lens and television lens T _I = Composite transmittance of optical diaphragm and ND filter = a · b where a = transmittance of ND filter, b = transmittance of diaphragm and the above-mentioned optical diaphragm and ND filter Composite transmittance T
_As shown in FIG. 5, _I is the first ND filter (transmittance a
Whichever of 1) or the second ND filter (transmittance a2) is selected, it can be corrected by adjusting the transmittance b of the optical diaphragm. That is, in order to obtain a certain combined transmittance T _I ,
It can be said that the combination of the optical diaphragm and the ND filter has arbitrariness.

[0010]

However, since the combination of the optical diaphragm and the ND filter has the above-mentioned optionality for the same incident dose to the image intensifier, the difference in the diaphragm diameter (the diaphragm transmittance b However, there is a drawback that stable performance cannot be obtained due to a change in image characteristics (change in MTF, for example, a relationship between aperture diameter, depth of focus and focus, and vignetting due to excessive aperture).

Further, the first and second ND filters 103 and 10
Since the respective transmittances of Nos. 4 and 5 are constant (fixed), they can be used only as a rough shift of the light quantity level, and there is a drawback that fine adjustment always requires readjustment of the optical diaphragm, and the adjustment time becomes long.

Further, since the ND filter is mechanically inserted into and removed from the optical path using a solenoid, there is a drawback that the reliability is deteriorated when it is operated many times.

Therefore, an object of the present invention is to perform light quantity adjustment within a short time without changing image characteristics (change in MTF).
An object of the present invention is to provide an X-ray imaging apparatus that is highly reliable even when operating many times.

[0014]

In order to solve the above problems, the present invention provides an X-ray source for generating X-rays and an image intensifier for converting the X-rays that have passed through an object into a visible image. And an image pickup unit for picking up a visible image of the image intensifier, and a light amount adjusting unit interposed between the image intensifier and the image pickup unit for adjusting the light amount of the visible image of the image intensifier. And the light quantity adjusting means includes one or more iris diaphragm means and liquid crystal filter means, respectively.

According to the present invention, the iris diaphragm means and the liquid crystal filter means as the light quantity adjusting means interposed between the image intensifier and the image pickup means are, for example,
The iris diaphragm means is an I.D. I. The amount of light is adjusted when the field of view is switched, while the liquid crystal filter means capable of continuously changing the amount of light is responsible for adjusting the amount of light by the fluoroscopic / imaging method.

In this way, the I.D. I. Since the diameter of the optical diaphragm for each field of view is always constant, stable image characteristics can be obtained. I. If the sensitivity is corrected by the field of view, it is not necessary to readjust after that, and the adjustment time can be shortened. Further, the liquid crystal filter means does not require mechanical driving and reliability is improved.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to illustrated embodiments. Note that the same reference numerals are given to the already described portions, and redundant description is omitted.

(1) Example of Embodiment FIG. 1 shows the I.D. I. It is a conceptual diagram which shows the relationship between an optical system, and a television camera.

As shown in FIG. I. 101 and the X-ray television camera 107 on the optical path, I. A liquid crystal filter 1 capable of continuously adjusting the amount of light is inserted between the lens 102 and the optical diaphragm 105.

As shown in FIG. 2, the liquid crystal filter 1 is composed of a liquid crystal 2 sandwiched between PETs 3, and a peripheral portion thereof sandwiched by an intermediate film 4 made of polyvinyl butyral or the like. Reference numeral 5 is a power supply terminal.

As a characteristic of the liquid crystal filter, the transmittance at the time of transparency is high (for example, parallel light transmittance; 82%,
It is preferable that the total light transmittance (sum of scattered light and parallel light rays); 89%) and the ability to follow change in transmittance with respect to signals are high.

Next, the operation will be described.

First, in the configuration shown in FIG. I.
The light amount adjustment when switching the field of view of 101 is performed by the optical diaphragm 105. The diameter of the optical diaphragm 105 can be set to a desired size. I. Readjustment due to changes in the incident dose of 101 is not necessary.

Next, the light quantity adjustment by the fluoroscopic / photographing method is as follows.
The liquid crystal filter 1 shares the work. Here, in the conventional ND filter (see FIG. 4), since it is impossible to continuously change the light amount adjustment, it is necessary to readjust the optical diaphragm 105.
On the other hand, since the liquid crystal filter 1 can continuously change the light amount, it is not necessary to readjust the optical diaphragm 105, and the light amount can be set accurately. By doing so, the I.D. I. If the field of view is constant, the diameter of the optical diaphragm can be constant, so that the performance of image characteristics is stable.

The liquid crystal filter 1 does not require a mechanical drive section and has a durability against energization of more than 1 million cycles. Compared with a conventional mechanical insertion / removal means (for example, a solenoid) into the optical path, The reliability can be dramatically improved.

Further, in the present embodiment, the light quantity adjustment for switching the field of view between I and I is handled by the optical diaphragm 105, and the light quantity adjustment by the photographing technique is handled by the liquid crystal filter 1.
You may reverse this responsibility.

Further, in this embodiment, one optical diaphragm and one liquid crystal filter are arranged, but a plurality of optical diaphragms and liquid crystal filters may be arranged.

(2) Modified Example FIG. 3 shows a modified example of the liquid crystal filter and the optical diaphragm. (A) is a perspective view, (B) is a side view, and (C) is a front view when the optical diaphragm is opened. FIG. 1D is a front view when the optical diaphragm is narrowed.

As shown in FIGS. 3A and 3B, an arm 12a is projectingly formed on the ring-shaped optical diaphragm 12, and a rotation hole 12b for inserting a shaft (not shown) is formed at the tip of the arm 12a. Has been formed.

A liquid crystal filter 1a is integrally attached to the upper surface of the ring portion of the optical diaphragm 12.

Then, with the rotary hole 12b inserted in the shaft, the liquid crystal filter 1a and the optical diaphragm 12 are
I. I. The optical path between 101 and the television camera 107 is made removable.

With this structure, the liquid crystal filter and the optical diaphragm can be integrally formed, and the number of parts can be reduced.

3 (C) and 3 (D) are plan views when the aperture of the optical diaphragm is large and when it is small.

[0034]

As described above, according to the present invention, as the light quantity adjusting means which is interposed between the image intensifier and the image pickup means, and which adjusts the light quantity of the visible image of the image intensifier, respectively, Since more than one iris diaphragm means and liquid crystal filter means are provided, the following effects can be obtained.

I. Differences in Fluoroscopy / Radiographing Method I. Since the optical aperture diameter can be made constant with respect to the change of the incident dose of, stable image characteristics can be obtained.

The adjustment time of the light quantity can be shortened.

The reliability of the light control means (iris diaphragm and liquid crystal filter) can be maintained even after long-term operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a liquid crystal filter used in the embodiment example.

3A and 3B are modifications of the embodiment, in which FIG. 3A is a perspective view in which a liquid crystal filter and an optical diaphragm are integrated, FIG. 3B is a side view, and FIG. 3C is a front view in which the optical diaphragm is opened. (D) is a front view with the optical diaphragm closed.

FIG. 4 is a configuration diagram of a conventional example.

FIG. 5 is a diagram showing a relationship between an ND filter and a diameter of an optical diaphragm.

[Explanation of symbols]

 1,1a Liquid crystal filter 2 Liquid crystal 12,105 Optical aperture 101 Image intensifier 107 X-ray television camera

Claims (1)

[Claims] 1. An X-ray source that generates X-rays, an image intensifier that converts the X-rays that have passed through an object into a visible image, and an imaging unit that captures a visible image of the image intensifier. And a light quantity adjusting means interposed between the image intensifier and the image pickup means and adjusting the light quantity of the visible image of the image intensifier, wherein the light quantity adjusting means each include one or more iris. An X-ray imaging apparatus having aperture means and liquid crystal filter means.