JP2003008994A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide acting an image intensifier using a flat-panel sensor for an image receiving section as a receiver. SOLUTION: A caption 1 indicates the enclosure of an image intensifier, and a caption 2 is a photoelectric conversion face and has the same function as that of a photoelectric conversion face 52 shown in Fig. 6. A caption 3 indicates a flat-panel sensor and a caption 4 is radiant ray protection plate made of lead, which is placed to black an X-ray being a radiant ray to an electric system at a post-stage thereby avoiding the adverse effect to the electric system. A caption 5 is a controller for driving the flat-panel sensor 3 to conduct sensor drive, image processing and conversion to a video signal. A caption 6 is a TV camera, a caption 8 a power supply and a caption 7 a video signal output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image receiving device, and more particularly to an image receiving device for generating an image from an X-ray energy distribution.

[0002]

2. Description of the Related Art There is a method of imaging the transmission distribution of X-rays when observing the inside of a structure represented by a human body without invasion. In order to image the X-ray dose distribution, there is a method of forming a latent image on the silver salt film by the X-ray energy itself or light excited by the X-rays, and developing and observing the latent image. Also, if you want to obtain dynamic images in real time,
At present, it is general to use an image intensifier that converts excited light into photoelectrons, converges it with a photomultiplier tube, and captures a high-luminance image with a TV camera.

However, due to the recent sophistication of semiconductor technology,
Large-sized solid-state imaging devices have also been manufactured, and so-called flat panel sensors have been put into practical use, in which the spatial distribution obtained by converting the X-ray energy distribution into fluorescence or free electron hole pairs is directly converted into an electric signal by the large-sized solid-state imaging device. It's starting.

Since the image intensifier has a high convergence efficiency and can form an extremely highly sensitive image acquisition device, it requires a photomultiplier tube which is a large vacuum tube, and there is a limit to its size increase. Also, in order to make the convergence uniform, the tube surface, which is the image receiving surface, is curved almost spherically, and if there is a very strong energy part in the spatial distribution, "halation" etc. that spreads to the entire image will occur. It also includes problems such as doing.

FIG. 6 shows an image intensifier and T
1 is a schematic diagram of a configuration in which V cameras are combined. Reference numeral 51 is an image intensifier, which is a large vacuum tube. It has electrodes for focusing the photoelectrons or for zoom control for changing the field of view, and is supplied from a high-voltage power generator 54. It operates with a high voltage power supply. Reference numeral 55 indicates power supply, and reference numeral 56 indicates the above-mentioned electrode control signal. Reference numeral 52 is a fluorescent surface for converting X-rays into fluorescence and photoelectric conversion surface for converting fluorescence into photoelectrons on the entire surface of the image intensifier, and 53 is a casing for protecting the image intensifier 51. 57 is a T provided at the output part of the image intensifier 51.
This is a V camera, and photoelectrons converged by the image intensifier convert a visible image on the output fluorescent screen into a video signal. Reference numeral 59 represents a power input for the TV camera, and 58 represents a video signal output.

Compared with the image intensifier, the flat panel sensor is characterized in that it can be easily increased in size, an image can be acquired with perfect flatness, and a phenomenon such as halation is relatively unlikely to occur.

[0007]

An X-ray image pickup apparatus using an image intensifier has existed for a long time and is currently widely used in each medical facility. Although there are many advantages of replacing the image receiving portion with the flat panel sensor as described above, it is very difficult to retrofit only the image receiving portion because the structure of the sensor is too different.

The present invention has been made in view of the above problems, and an object thereof is to provide an image intensifier having a flat panel sensor as an image receiving portion as an image receiving device.

[0009]

In order to achieve the object of the present invention, for example, an image receiving apparatus of the present invention has the following configuration.

That is, a flat panel sensor for converting the X-ray energy distribution into an electric signal and a conversion means for converting the electric signal from the flat panel sensor into a video signal output by a predetermined television camera are provided.

Further, the converting means includes a correcting means for correcting the electric signal, and the correcting means is provided for each panel when the flat panel sensor is divided into a plurality of panels.

Further, the converting means further comprises a scaling means for scaling the image represented by the electric signal, and the scaling means generates a scaled image by interpolation processing between pixels.

Further, the image intensifier of the present invention comprises the above-mentioned image receiving device.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail according to preferred embodiments with reference to the accompanying drawings.

[First Embodiment] An image receiving apparatus according to the present embodiment uses a flat panel sensor having the same appearance as the above-mentioned image intensifier and having the same function of outputting a video signal. That is, since the image intensifier itself has a very large housing, the flat panel sensor, the sensor drive control device, the power supply device, and the video signal conversion device are all built in the housing. Less than,
The image receiving apparatus according to this embodiment will be described.

An image pickup device using an image intensifier has a photomultiplier tube in which a phosphor such as CsI is arranged on the input tube surface and a phosphor for converting an electron beam into fluorescence is arranged on the output tube surface, and an output tube. It consists of a TV camera attached to the tube surface.

FIG. 1 is a diagram showing a configuration example of an image pickup apparatus including the image receiving apparatus of the present embodiment, in which a flat panel sensor and a device related to its driving are built in an image intensifier.

Reference numeral 1 denotes an image intensifier casing,
A photoelectric conversion surface 2 has the same function as the photoelectric conversion surface 52 shown in FIG. 3 is a flat panel sensor. Four
Is a radiation protection plate made of lead or the like, and is installed so that X-rays, which are radiation, are not transmitted to the electrical system in the subsequent stage and have no adverse effect. Reference numeral 5 denotes a control device for driving the flat panel sensor 3, which drives the sensor, performs image processing, converts to a video signal, and the like. 6 is a TV camera, 8
Is a power supply, and 7 is a video signal output.

If the function of the image intensifier has a zooming function, a zoom control signal (field-of-view control signal) 9 is also input to the control device 5, and the same function is achieved by the enlargement function by image processing. Since the control device 5 performs the same function as a normal image intensifier + TV camera system, it continuously drives the flat panel sensor 3 and outputs a video signal of about 30 frames per second.

In the image receiving apparatus of this embodiment, the flat panel sensor and the drive-related apparatus are provided inside the image intensifier, but the invention is not limited to this, and the external protective housing shown in FIG. It is also possible to have the same shape as.

The difference between the flat panel sensor and the existing image intensifier + TV camera system is that the flat panel sensor, which is a solid-state image sensor, is an assembly of a plurality of sensors as pixels, and there is a large variation in the characteristics of each pixel. Can be mentioned. Therefore, it is necessary to correct the variation, but it is desirable to perform numerical processing with a digital signal in order to perform stable correction.

FIG. 2 is a block diagram showing the state of the correction. Reference numeral 20 represents one partial panel when the flat panel sensor 3 is divided into a plurality of partial panels.
Normal flat panel sensor is 1000 × 1000-2
Although it has a set of pixels of about 000 × 2000, if analog-digital conversion (A / D conversion) is performed on the image from the flat panel sensor as it is, it is 3 per second.
To obtain 0 frame image, 30MHz per pixel
A / D conversion must be performed at a speed of about 120 MHz. An image having a gradation number of 12 bits or more is usually required for medical use, and analog-to-digital conversion of 14 bits or more is necessary in consideration of ensuring the correction and the dynamic range. It is difficult to perform such highly accurate analog-digital conversion at high speed, and it is difficult to obtain reliable data with a high S / N ratio. Therefore, usually, the flat panel sensor is divided into partial panels, driven in parallel, and independently A / D-converted. For example, 200
In case of 0x2000 pixel flat panel sensor, 4x
If divided into 4 = 16 partial images and driven in parallel, a video signal of 30 frames per second can be output by A / D conversion of 7.5 MHz per pixel.

Although there are as many correction blocks as the number of partial panels according to the above description, only one partial panel control is shown here for the sake of simplicity. The figure schematically shows the form of gain and offset correction as a block diagram. Further, the flat panel sensor 3 is controlled by the control device 5, and converts a charge value proportional to the X-ray dose existing in each pixel into an electric quantity that is a voltage or a current, and sequentially scans and outputs the electric quantity. Therefore, in the figure, each part except the flat panel sensor 3 is each part in the control device 5.

A block 21 is an A / D converter for converting an analog electric quantity output from the flat panel sensor 3 (actually a partial panel) into a digital value. Two
Reference numeral 2 is a gate for branching the output of the A / D converter 21 into two. Reference numeral 23 is a memory that stores in advance an image signal output from the flat panel sensor 3 (actually a partial panel) as an offset fixed pattern image without irradiating X-rays. The block indicated by 25 is a block for performing the difference,
For each pixel of the A / D converted image, the value of the memory 23 at the corresponding position is sequentially subtracted, and the LUT table 26
Transfer to. As a result, the fixed pattern noise of the offset can be removed.

The block designated by 26 is a look-up table (Look Up) for logarithmic conversion used for performing division.
Table, LUT). The image from the block 26 is subjected to known image processing by the LUT table 26, and the image processed image is transferred to a block 30 for calculating a difference via a gate 27.

Reference numeral 29 is a memory for storing an image when an operation called calibration is performed in this apparatus, which is output from the flat panel sensor 3 (actually a partial panel) without irradiating X-rays. Although the image signal corresponding to the X-ray is stored in advance as an offset fixed pattern image, only the X-ray dose distribution itself and the gain variation for each pixel are captured in the absence of a subject. This calibration operation is performed about once a day at the beginning of work, and this operation corrects the gain variation that the flat panel sensor has for each pixel. In block 30, the difference in gain between the pixel logarithmically converted in block 26 and the corresponding pixel in the memory 29 is executed to correct the gain variation.

The correction result is stored in the position of the corresponding partial image in the frame memory 32 or 33 via the gate 31. These two frame memories 32 and 33
Are used alternately for each frame of the moving image. That is, when the data is written in the frame memory 32, the data is read from the frame memory 33, and when the data is written in the frame memory 33, the data is read from the frame memory 32. Therefore, the gate 31 switches the frame memory (either 32 or 33) to write, and the gate 34 switches the frame memory (either 32 or 33) to read.

FIG. 3 shows each block for performing image enlargement and the like, and each unit shown in FIG. 3 is each unit in the control device 5. Reference numeral 47 is a block for controlling each part shown in FIG.

In the image intensifier, a visual field area is set, and photoelectrons in that area are converged to perform zooming. On the other hand, with a flat panel sensor, such zooming is not possible, so data is collected before interpolation enlargement. The above-mentioned view control signal is input to the block 47 as an input signal for determining the interpolation enlargement ratio and the calling area from the frame memory. Here, the number of pixels of the output image is always constant with respect to the change of the number of pixels of the input image. Reference numeral 35 denotes a gate for controlling the pixel data read from the frame memory 34 shown in FIG. 2 in the raster direction, and the timing control for reading is controlled by the block 47.

FIG. 4 is a diagram for explaining a case of double magnification as an example of image enlargement by each unit shown in FIG. 1
01 is the entire frame memory 32 or 33, 102
Is a visual field area, and an area having a size of ½ in the vertical and horizontal directions with respect to the frame memory 32 or 33 is set in the central portion. This area image is enlarged by the video signal and becomes an image 103. That is, the block 47 reads the frame memory 101 from the read start position 104 of FIG. 4 in the direction of the arrow (raster direction) for the read area 102. Further, since the enlargement is doubled, the read timing is one read per two interpolation calculation output pixels.

However, the image processing is not limited to the above-described enlargement interpolation, and reduction interpolation can be performed depending on the interpolation method. Further, it is also possible to perform the same-size conversion between different dot pitches without performing enlargement or reduction.
Note that enlargement or reduction may be referred to as scaling.

Returning to FIG. 3, 36 is a register for storing one pixel, and 37 is a similar register. 36 and 3
Reference numeral 7 is a shift register. Numerals 38 and 39 denote multipliers which carry out an operation for multiplying the output data of the shift registers 36 and 37 by the coefficient appropriately generated from the block 47. Reference numeral 40 is a block that performs addition, and the shift register 3
The interpolated value between the output data from 6 and 37 is obtained. 41
Is a line buffer corresponding to one line of the frame memory, and 42 is a similar line buffer. The line buffer has a shift register structure and sequentially transfers pixel data to the next stage in one clock. 43 and 44 are multipliers having the same function as the multipliers 38 and 39. Therefore, with this configuration, enlargement by interpolation calculation is performed while reading image data. In this case, bilinear interpolation using two points is performed, but spline interpolation using four points can be performed with the same configuration. Reference numeral 46 is a block which converts the interpolated pixel data into an analog signal again and outputs a video signal equivalent to the video signal output from the TV camera 57 shown in FIG.

Further, since the image intensifier basically has an image receiving portion of a circular area, it is possible to mask and output the image area in a circular shape accordingly.

From the above description, it is possible to provide the image receiving device in which the flat panel sensor is attached to the image intensifier. As a result, the image receiving apparatus according to this embodiment can be used as an existing image intensifier, and can further benefit from the function of the flat panel sensor.

[Second Embodiment] In the first embodiment,
Zooming was performed by interpolation enlargement, but in this case, the substantial amount of information does not increase due to zooming. In this embodiment, a mechanism for changing the amount of information according to zooming is shown.

In this embodiment, for example, two TV cameras are used.
If it is 000 lines / frame, the flat panel sensor used for it is 4000 × 4000.

The flat panel sensor can be driven usually by switching using a transistor or switching using a voltage follower element, but if 2 lines are selected collectively and the output signals for 4 pixels are added in an analog manner, 2 × 2. Can be obtained by adding pixels, 4000 ×
4000 flat panel sensors 2000 x 2000
It can be treated as a pixel. As a result, the processing speed of the sampling A / D converter / electric system can be suppressed, and stable operation can be performed. For example, when the field of view area is halved, sampling is performed for each pixel without performing analog addition for the above four pixels. With this, when there is no need for interpolation calculation of an excessive enlargement ratio and the view field area is reduced,
The spatial resolution is improved, and the substantial amount of information can be increased.

For example, FIG. 5 shows a part of a flat pixel sensor for four pixels which realizes transmission by switching using a transistor, and a portion surrounded by a broken line circle shows one pixel. The diode in each pixel is a photodiode, and the detected photocurrent is charged in the capacitor and taken out by the line output capacitor. 11
Reference numeral 1 is a reset signal of the capacitor, which is reset for each frame, and 116 is a reset signal for each line, which is reset for each line. 112 and 113 are selected as the selection signals 114 and 115 of the respective lines, and the signals of the lines in which the switch using the transistor operates are 114 and 11
5 is output. If the entire image is taken out by addition of 2 × 2 pixels, pixel charges for two lines are charged in the output capacitor by selecting 112 and 113 at the same time. By adding the analog outputs of 114 and 115 at the output stage, 2 × 2 pixel addition can be performed. If the field of view becomes smaller, 112 and 113 are individually selected and the electric charge of each pixel is taken out independently.

[0039]

As described above, according to the present invention, an image intensifier having a flat panel sensor as an image receiving portion can be provided as an image receiving device.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of an imaging device including an image receiving device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a correction process.

FIG. 3 is a diagram showing each unit lock for performing image enlargement and the like.

FIG. 4 is a diagram illustrating a case of 2 × enlargement as an example of image enlargement by each unit illustrated in FIG.

FIG. 5 is a diagram showing a part of a flat panel sensor for four pixels that realizes transmission by switching using a transistor.

FIG. 6 is a diagram showing an outline of a configuration in which an image intensifier and a TV camera are combined.

Claims (6)

[Claims] 1. A flat panel sensor for converting an X-ray energy distribution into an electric signal, and a conversion unit for converting the electric signal from the flat panel sensor into a video signal output by a predetermined television camera. Image receiving device. 2. The conversion means comprises a correction means for correcting the electric signal, and the correction means is provided for each panel when the flat panel sensor is divided into a plurality of panels. The image receiving device according to claim 1. 3. The image receiving apparatus according to claim 2, wherein the correction unit corrects a gain and an offset with respect to a pixel included in the panel. 4. The conversion means further comprises a scaling means for scaling the image represented by the electric signal, and the scaling means generates a scaled image by interpolation processing between pixels. Item 1. The image receiving device according to Item 1. 5. The image receiving apparatus according to claim 1, wherein the conversion unit further adds adjacent pixels of an image represented by the electric signal and selects image acquisition with low resolution. 6. An image intensifier comprising the image receiving device according to claim 1. Description: