Patent Number: 050739140
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS There will now be described preferred embodiments of a stereoscopic X-ray apparatus according to the present invention with reference to the accompanying drawings. First, the principle of the present invention is explained It is assumed that desired stereoscopy is obtained with the positional relation among an object 2 to be examined, stereoscopic X-ray tube 4, and image pick-up plane 6 (input fluorescent screen of an image intensifier tube) set as shown in FIG. 1A. At this time, a distance Di between two images of a point P in the object 2 created by X-rays irradiated from the right and left foci of the X-ray tube 4 corresponding to parallax between the two images relating to the stereoscopy can be derived as follows. That is, the following equation can be obtained if the convergence angle between the two X-rays is .theta.. EQU tan .theta.=Df/(Lx - Lo)=Di/Lo (1) where Df indicates a distance between the right and left foci of the X-ray tube 4, Lx indicates a distance between the right and left foci of the X-ray tube 4 and the image pick-up plane 6, and Lo indicates a distance between the object point P and the image pick-up plane 6. The distance Di between the two images picked-up on the plane 6 can be expressed as follows by rewriting the equation (1). EQU D=Df.times.Lo/(Lx- Lo) (2) At this time, the stereoscopic display state shown in FIG. 2A is obtained if two images are alternately displayed on one display unit. In this case, the right and left images displayed are deviated from each other in a horizontal direction on the same display unit, thus causing parallax between the right and left images and permitting the X-ray image of the object to be stereoscopically observed An observer can observe the same positional relation of the blood vessel and organizations from a view point of anatomy in the stereoscopic display under the desired stereoscopy as he or she observe the living body. Therefore the positional relation as shown in FIG. 1A is called a standard positional relation. If only the object 2 is moved towards the image pick-up plane 6 with the distance Lx between the right and left foci of the X-ray tube 4 and the image pick-up plane 6 kept unchanged in the standard positional relation as shown in FIG. 2B, the distance between the object point P and the image pick-up plane is changed to Lo' so that the distance (=Di') between the right and left images on the pick-up plane 6 becomes smaller than Di. As a result, the distance Di' between the right and left images corresponding to the parallax becomes smaller than that set in the standard positional relation as shown in FIG. 2B, and therefore the stereoscopy becomes weak. In order to compensate for reduction in the stereoscopy, the distance between the two images may be set to be larger when the two images are displayed. That is, the left image is shifted to the right and the right image is shifted to the left and then the images are displayed. As a result, the distance Di' between the images can be substantially increased, thereby making it possible to provide the same stereoscopy as in the case of FIG. 1A. In contrast, when the distance Lx" between the X-ray tube 4 and the image pick-up plane 6 becomes longer than Lx with the distance between the object point P and the right and left foci of the X-ray tube 4 kept unchanged as shown in FIG. 1C, the distance (=Di") between the right and left images on the pick-up plane 6 becomes longer than Di as shown in FIG. 2C. Also, in this case, if the distance Di" becomes excessively long, the stereoscopy becomes too strong to attain the desired stereoscopy. In order to compensate for this, the two images may be shifted to come closer to each other when they are displayed. Thus, the distance Di" between the images can be substantially reduced, making it possible to attain the same stereoscopy as in the case of FIG. 1A. FIGS. 2A to 2C show a case where the images are dynamically and stereoscopically displayed on one display unit, but when two display units are used to effect the static stereoscopic display, it is also possible to shift two images in the same manner as described above and then display the two images on two display units. Now, the construction of the first embodiment of the present invention based on the above-described principle is explained with reference to FIG. 3. A stereoscopic X-ray tube 12 having two foci separated by a preset distance from each other is disposed above an object 10 to be examined and lying on a bed (not shown). An image intensifier tube 14 and a TV camera 16 are integrally arranged below the object 10. The X-ray tube 12 alternately irradiates X-rays from the two foci towards the object 10. An X-ray image of the object 10 incident on the image intensifier tube 14 is converted to an optical image and picked-up by the TV camera 16. An image signal from the TV camera 16 is supplied to an image memory 20 via an A/D converter 18. The image memory 20 includes two frame memories 20a and 20b for storing respective X-ray images of the object 10 based on X-rays irradiated from the right and left foci of the X-ray tube 12. An output of the image memory 20 is supplied to a display unit 24 via a D/A converter 22. That is, output images of the frame memories 20a and 20b are alternately displayed on the display unit 24. Images on the display unit 24 are observed though field switcher glasses 26 with electronic shutters driven in synchronism with the alternate display operation. The positional relation among the X-ray tube 12, image intensifier tube 14, and object 10, that is, a distance between the image intensifier tube 14 and the object 10 and a distance between the image intensifier tube 14 and the X-ray tube 12 are changed according to the image pick-up condition and thus are detected by a position detector 28. The detection results are supplied to a read/write controller 30 for the image memory 20. A system controller 34 for synchronizing the entire control operations is connected to the glasses 26, read/write controller 30 and a high tension generator 32 to irradiate the X-ray. The operation of the first embodiment is explained with reference to FIGS. 4A to 4C. First, a distance between the object 10 and the image intensifier tube 14 and a distance between the X-ray tube 12 and the image intensifier tube 14 are detected by the position detector 28 and the detection results are supplied to the read/write controller 30. The memory 20 is set into the write-in mode, X-rays are alternately irradiated from the two foci and X-ray images thus created are written into the respective frame memories 20a and 20b. In this example, suppose that a left image created by the X-ray irradiated from the focus located on the right side when supplied from the TV camera 16 is stored into the frame memory 20a and a right image created by the X-ray irradiated from the focus located on the left side is stored into the frame memory 20b. Next, the memory 20 is set into the readout mode (at this time, the object may be removed from the bed) and image data items are alternately read out from the frame memories 20a and 20b in synchronism with the frame period of the display unit 24, supplied to the display unit 24 via the D/A converter 22, and displayed on the display unit 24. Then, the system controller 34 controls the ON/OFF operation of the right and left electronic shutters of the glasses 26 in synchronism with the operation of reading out data from the frame memories 20a and 20b so as to permit the left and right images to impinge on the left and right eyes, respectively. As a result, parallax occurs between the two images observed by the right and left eyes and the observer can stereoscopically observe the X-ray images of the object. However, under this condition, the parallax is determined by the positional relation of the object set at the image pick-up time and it is sometimes impossible to attain desired stereoscopy. Therefore, the read/write controller 30 checks the stereoscopy (distance between the right and left images) at the image pick-up time based on the positional relation among the X-ray tube 12, object 10, and image intensifier tube 14 detected by the position detector 28 and checks whether it is equal to the distance Di in the standard positional relation or not. If it is detected that it is not equal to the distance Di, the two images are shifted in a horizontal direction to adjust the distance between the two images. Shift of the image in a horizontal direction may be effected by changing readout addresses with respect to the write-in addresses for the image memory 20. Since the distance between the images is determined by the relative positions of the images, it is possible to shift only one of the images to adjust the distance. However, in order to prevent the image being out of the screen by the image shift, in this example, the right and left images are shifted in opposite directions by the same distance equal to half the difference between the distance set at the image pick-up time and the distance set in the standard positional relation. It is assumed now that the positional relation of the object at the image pick-up time is shown in FIG. 1C and an example of display as shown in FIG. 4B is obtained at this time. Further, it is assumed that an example of display obtained in the standard positional relation is shown in FIG. 4A. At this time, the shift amount .DELTA. is (Di" - Di)/2. Therefore, as shown in FIG. 4C, if the left and right images are read out after being shifted by .DELTA. in the right and left directions, respectively, the same stereoscopy as is obtained in the standard positional relation can be attained irrespective of the positional relation among the object, X-ray tube, and image intensifier tube set at the image pick-up time. At this time, if Di" is smaller than Di as shown in FIG. 1B, .DELTA. becomes negative so that the left image may be read out after being shifted by -.DELTA. in the right direction, that is, after being shifted by .DELTA. in the left direction and the right image may be read out after being shifted by -.DELTA. in the left direction, that is, after being shifted by .DELTA. in the right direction. Also, in this case, the same stereoscopy as is obtained in the standard positional relation shown in FIG. 1A can be attained. As described above, according to the first embodiment, X-ray images of the object are picked-up based on X-rays irradiated from the right and left foci of the X-ray tube 14 and stored into the frame memories, and the stored X-ray images are alternately read out from the frame memories and alternately displayed on the same display unit. The displayed images are observed through the glasses with electronic shutters driven in synchronism with the alternate display operation so that the stereoscopic image of the object can be observed. At the time of display, the positional relation of the object at the image pick-up time is checked and if it is detected that the standard positional relation is not attained, the two images are displayed after being horizontally shifted in order to compensate for deviation in the stereoscopy, so that stereoscopic display can always be obtained with desired stereoscopy. In the first embodiment, the dynamic stereoscopic display using one display unit is explained, but it is also possible to effect the static stereoscopic display for simultaneously displaying the two images on two display units positioned right and left. Further, in the first embodiment, the stereoscopic X-ray tube is used to obtain right and left X-ray images, but it is also possible to use a normal single-focus type X-ray tube, and in this case, the X-ray tube is revolved by a preset angle with the object set as its revolution center and X-rays are irradiated before and after the revolution. Further, the image intensifier tube is used to pick-up X-ray images which have passed the object, but it is also possible to photograph the X-ray images, read out the image information by means of an image reader, for example, and then store the image information into an image memory. In this case, the preset angle of revolution corresponds to the parallax of the images. Therefore, it is necessary to input the angle to the read-write controller 30. Now, the other embodiments are explained. In these embodiments, the same portions as those shown in the first embodiment are denoted by the same reference numerals and the detail explanation therefore is omitted. FIG. 5 is a block diagram showing the second embodiment. The second embodiment is similar to the first embodiment except that an image enlargement circuit 40 is connected between the image memory 20 and D/A converter 22. In the first embodiment, if the positional relation shown in FIG. 1B is set, a distance Di' between the two images becomes smaller than a distance Di set in the standard positional relation as shown in FIG. 6A, and in order to attain the same stereoscopy as in the standard positional relation, it is necessary to shift the two images so as to increase the distance between the two images. In this case, the left end of the right image frame enters the left image to cut away the left portion of the left image as shown by a hatched portion of broken lines in FIG. 6B. Likewise, the right end of the left image frame enters the right image to cut away the right portion of the right image as shown by a hatched portion of solid lines in FIG. 6B. In order to solve this problem, in the second embodiment, an output image from the image memory 20 shown in FIG. 7A is enlarged as shown in FIG. 7B by means of the image enlargement circuit 40. As a result, even if the two images are shifted to increase the distance therebetween, although the side portions of the images may extend outwardly of the screen of the display as shown in FIG. 7C and may not be displayed, the right and left end portions of the display screen does not cover the images so that part of the image will not be deleted and the effective display area of the image will not be reduced. The magnifying factor of the enlargement circuit 40 is so set that part of the image which is required to be positively observed may be displayed in the entire area of the display screen. FIG. 8 is a block diagram showing the third embodiment. The third embodiment differs from the first embodiment in that an adjuster 42 capable of adjusting the sensitivity of stereoscopy is connected to the read/ write controller 30 and the static stereoscopic display method of simultaneously displaying two images on two display units is used. In the above-described embodiments, the distance between the two images picked-up and displayed on the display screen is automatically adjusted to be set equal to the distance set in the standard positional relation as shown in FIG. 1A, but since the standard state in which the best stereoscopy is obtained may be different from person to person, the adjuster 42 is used to adjust the parallax (distance Di between the images) in this embodiment. Further, outputs of the frame memories 20a and 20b are respectively supplied to the display units 24a and 24b via the D/A converters 22a and 22b at the same time. Then, the images are observed by the right and left eyes through a stereoscopic viewer 44 for guiding the display images on the right and left display units 24a and 24b to the right and left eyes, thereby permitting the object to be stereoscopically observed. As described above, according to the stereoscopic X-ray apparatus of the present invention, two images obtained by irradiating X-rays in two directions to the object can be set into the stereoscopic display state by setting them with a distance determined according to the positional relation between the object and the X-ray tube and image intensifier tube set at the image pick-up time, and as a result, the stereoscopy at the time of stereoscopic display can be adjusted irrespective of the position of the object after they are picked-up so that desired stereoscopy can be attained under any image pick-up condition. Further, a stereoscopic X-ray apparatus can be provided in which the stereoscopy can be changed by changing the distance between the two displayed images so that the positional relation in the depth direction between two things can be correctly recognized by any person. The present invention is not limited to the above described embodiments, but can be variously modified. For example, instead of directly picking-up an output image of the image intensifier tube by use of the TV camera, the output image may be photographed on a film and image data on the film is read out by an image reader or the like after it is developed and then stored into an image memory A single-focus X-ray tube may be used as the X-ray tube instead of the stereoscopic X-ray tube, and in this case, X-rays are sequentially irradiated in two different directions set at different times Further, in the drawing, X-rays are irradiated from a position set above the object but can be irradiated from a position set under the object. In this case, the images obtained from the X-rays emitted from the right and left foci must be impinged on the left and right eyes, respectively so as to observe the front view of the object which is the standard for the diagnosis.