WO2001077654A1

WO2001077654A1 - Digital imaging apparatus

Info

Publication number: WO2001077654A1
Application number: PCT/KR2000/000255
Authority: WO
Inventors: Young Hoon Shin
Original assignee: Star V-Ray Co., Ltd.
Priority date: 2000-03-23
Filing date: 2000-03-23
Publication date: 2001-10-18
Also published as: AU2000234617A1

Abstract

The present invention relates to a digital imaging device for wide screen, consisting of an optical system comprising light source, phosphorscent screen and a plurality of lens systems; imaging device; and image combining means for synthesizing the final image, wherein only visible light from a certain section of said phosphorscent screen is guided to the relevant lens system and more than one buffer having a plurality of holes for enhancing resolution are used. The subject invention discloses further an optical (support) construction in platform having lens holes for accommodation of a plurality of lenses and a lens for Rounded Brightness Enhancement Film which lets only such visible light from the visible light generated and released by said phosphorscent screen that is directed to an angle below a certain angle to said phosphorscent screen pass through it. With the means described above, the subject invention can not only enhance the resolution, sharpness, and brightness of an image, but also improve the mechanical stability and environmental durability of a device.

Description

DIGITAL IMAGING APPARATUS

Technical Field of the Invention

The present invention generally relates to a digital imaging apparatus for wide screen, in particular, to a digital imaging apparatus capable of producing images having excellent resolution, brightness, and sharpness while at the same time providing improved durability and stability.

Background of the Invention

In modern medical sciences, methods of imaging the inside of human body by using the properties of reflection, transmission, refraction, and scattering of ultrasonic wave, ultraviolet ray, or electromagnetic waves such as X-ray, gamma ray, etc. are widely used for clinical diagnostic applications. Among them, X-ray imaging apparatus utilizing the permeability of X-ray has become a typical clinical apparatus since long. Such an X-ray imaging apparatus requires a means which detects the X-ray transmitted through a body and converts the X-ray into an appropriate image signal. For these purposes, a wide variety of detectors (or sensors) are used.

Recently, a new apparatus has been developed wherein transmitted X-ray, radioactive ray such as gamma ray, or ultraviolet ray is made incident on a scintillator to be converted into visible light rays, and the visible light rays are then transmitted through an appropriate optical system so that the intensity of the transmitted visible light rays are observed. Such an X-ray imaging utilizing a scintillator apparatus comprises in general an X-ray source, a scintillator or phosphor that absorbs the transmitted X-ray and converts the same into visible light, an optical system capable of imaging the converted visible light, and an image-recording means for extracting and recording the images.

The scintillator used herein utilizes a so called intensifying screen containing a phosphorescent material that converts the transmitted invisible electromagnetic wave (X-ray, gamma ray, neutron, ion, electron, etc.) into visible light. The visible light generated by scintillation of the transmitted electromagnetic wave is detected by an electric photo-sensitive detector such as film, CCD (Charge Coupled Device), photocathode, photodiode, etc. and imaged. Here, a material capable of emitting a large number of light photons even with a small amount of rays transmitted (such as X-ray) is selected for use as scintillation material. The photo sensitive detector is relatively small in size in comparison to the scintillator (phosphorescent screen), and the visible light rays generated by scintillation are so scattered that they spread over a wide area of surface. Thus, in order to make the visible light rays incident appropriately on the photo sensitive detector, an optical system comprising one or more lens is used.

With respect to electronic imaging technique, U. S. Patent No. 5,105,087 has disclosed a technique utilizing multiple detector arrays to produce images over a large area for diagnostic mammography applications. This invention relies on multiple layers of detector elements, one above the other, to provide a complete image with no gap. A disadvantage with this system is that a sufficient number of photo detectors are required to cover the entire active area, which inevitably increases the cost of the device. Another shortage of this system is that, since edges of a detector array of one layer is located in front of a detector array of a lower layer, the quality of an image obtained by the detector of the lower layer is worsen by those edges.

In U. S. Patent No. 5,043,582, the photo sensitive properties of transistors in dynamic random access memory (DRAM) integrated circuits are used to detect photons emitted from X-ray sensitive phosphors. The use of DRAM cells as photo sensitive pixels results in less optical sensitivity because not the entire active area of each pixel is photo sensitive due to the requirements for addressing the DRAM cells. Furthermore, the detection scheme in this invention is binary in nature, so that complicated afterprocesses are needed to obtain gray scales. In U. S. Patent Nos. 5,142,557 and 5,216,250, optically coupled CCD techniques are used for X-ray imaging, wherein an optical lens is used to image the visible photons emitted by an X-ray sensitive phosphorescent screen onto a single CCD detector. Whereas the visible photons emitted by a phosphorescent screen have only to be guided to CCD detector by means of optical fibers or the like for obtaining a small- area X-ray imaging, a thicker bundle of optical fibers are necessary for a larger image, resulting in immense increase of the manufacture cost. In this case, an optical system such as a lens is used to condense the visible lights emitted by a phosphorescent screen and to send the condensed visible lights to a small CCD detector. Because the CCD detector is smaller than the phosphorescent screen, the image from the screen must be condensed to allow the entire image recorded by the detector. In other words, since a single CCD detector should image the entire area, the spatial resolution of the image will deteriorate.

To overcome these defects, U. S. Patent No. 5,844,242 provides a mosaic style electronic digital imaging arrays to scan the entire image. The imaging arrays are mounted on a carrier platform to form a pattern. The arrays are then exposed to X-ray- radiated portion and generate digital signals for partial images. The platform is subsequently moved (repositioned) to another portion of the image and the arrays are exposed to generate digital data for another portion of the image. While the arrays are being repositioned, the digital data so generated are transferred to a computer memory. This process is repeated until the entire image has been exposed to the arrays. Finally, the accumulated multiple image data are combined by a data processor to form a composite radiated image. This digital X-ray imaging system comprises an X-ray tube as the X-ray source, a phosphorescent screen that converts the X-ray traveled through an object into a visible light image, optical fibers which transmit the visible light image from the screen to a mosaic CCD arrays, a mosaic type CCD arrays which converts the visible light image into digital data, and a mechanical repositioning stage which repeatedly moves the CCD arrays to a new position until the entire image is exposed. Further, an aperture plate which serves to decrease the X-ray dose received by a patient by reducing the scattering of X-ray beam radiated from the X-ray tube onto the patent is also provided for.

Although this method might decrease the number of necessary detector, it requires, on the other hand, addition of mechanical device for scanning, making the apparatus to be bulky and the cost increased. Furthermore, it takes quite a few seconds to scan the entire image, which might make patients feel inconvenient. In addition, there is a possibility of blurring the image due to possible moving of the patient. What is still worse, the patients are exposed to increased dose of X-rays.

U. S. Patent 5,822,392, issued to General Electric Company, has disclosed method for use of a multi-resolution detector in embodying X-ray imaging such as X- ray tomography or digital radiography utilizing a computer. The multi-resolution detector in the above patents is comprised of two-dimensional low resolution detector elements of mXn arrays and one or more of high resolution detector elements that are provided around the low resolution detector elements. After scanning an object completely by using the multi-resolution detector, an image of high resolution is combined from the scanned data.

To summarize the above conventional methods, an imaging means having plural imaging elements, such as CCD arrays, CMOS imager, etc. should be used for producing a digital image larger than the conventional size (18 24cm). And, each partial image taken by each imaging element is used as a pixel for the entire image. Further, an optical system comprising one or more lens is used for converging the scattered visible lights generated by a phosphorescent screen on an imaging means. The number of lenses should be equal to that of the elements contained in the imaging means. Each imaging element and the corresponding lens system are used for imaging the visible lights generated by a predetermined region of the phosphorescent screen. Each of the partial images so produced constitutes a pixel for the entire image, i.e., a partial image (pixel) is made out of the visible light generated from a specific region of the phosphorescent screen. Here, for example, the imaging means is, CCD arrays and the imaging elements are CCD elements contained in the CCD arrays. However, the above-described digital imaging devices have the following disadvantages:

1) The entire image exhibits poor resolution, sharpness, and brightness, because the visible lights converted or emitted by the phosphorescent screen are so scattered that they cannot be converged on a single point.

2) Each of the imaging elements receives not only the visible light emitted from the corresponding region of the phosphorescent screen but also the light emitted from the neighboring region. In such case, the visible light from the neighboring region serves like a kind of background noise, thereby resulting in degradation of resolution and sharpness of the entire image. Thus, a guide means is needed which enables each lens system and each imaging element to receive only the visible light emitted from its corresponding region of the phosphorescent screen.

3) The conventional optical system has a configuration wherein each housing including a lens system is located on the upper end of the imaging element such as CCD element. However, this configuration is not strong enough to stand against the external environments. Further, in case where the connections of lens systems and CCD elements are indisposed due to external temperature changes, vibration, impact, etc., such indisposition should be compensated in isolated manner, which is quite burdensome. Still further, preciseness of the image is deteriorated and durability of the apparatus is not assured, because the connection portions of the optical system and imaging elements are easily to be distorted.

Detailed Description of the Invention

The present invention is intended to provide a digital imaging apparatus which is capable of overcoming the foregoing difficulties of the prior arts.

It is an objective of the present invention to provide a digital imaging apparatus with improved resolution, sharpness, and brightness by means of a film lens that can reduce scatter of the visible light emitted from a phosphorescent screen and improve directivity of the emitted visible light. It is another objective of the present invention to provide a digital imaging apparatus with improved resolution and sharpness by means of a guide means that can prevent the visible light emitted from one region of a phosphorescent screen from entering into an imaging element that is allotted to other region of the screen. It is a further objective of the present invention to provide a digital imaging apparatus with improved solidity and mechanical stability by means of a monolithic optical system structure that can firmly support plural lens systems.

These objectives can be achieved with a digital imaging apparatus which comprises a radiation light source for generating radiation light and emitting the generated radiation light; a phosphorescent screen that absorbs the light transmitted through an object and converts the same into visible light; an optical system with a plurality of lens systems by which the visible light generated and emitted from the phosphorescent screen are incident on an imaging means; an imaging means comprised of a plurality of imaging elements which generate electric signals consistent with the visible lights radiated from the optical system; and an image-combining means that produces a final image after receiving the electric signals, wherein a film lens is further included which is interposed between the phosphorescent screen and the optical system, and transmits only such visible lights that are incident on it at less than a predetermined angle with the perpendicular of the phosphorescent screen, among the lights emitted from the phosphorescent screen.

The film lens, called BEF (Brightness Enhancement Film), concentrates the scattered rays of light into a narrow-angled area while at the same time reflecting the remainder of rays as backlight for reuse. A BEF is an array of multiple prisms on a transparent substrate, the prisms being disposed in an adjacent manner. The peak angle as well as the valley angle of the commonly used prism are around 90°. However, U. S. Patent No. 5,917,664, issued to 3M Innovative Properties Company, uses a BEF in which one or more of the peak angle or the valley angle has a value different from 90°. Further, an RBEF (Rounded Brightness Enhancement Film), also from the above company, comprising prisms having rounded peaks can be used as well. The materials, configurations, and methods of manufacture of such BEF s are disclosed in detail in U. S. Patent Nos. 4,542,449, 5, 175,030, 5,591,527, 5,394,255, 5,183,597, and 5,932,626.

Instead of the film lens, or in addition thereto, a visible light guide means can be employed which is interposed between the phosphorescent screen and the optical system in order to guide the visible light emitted from a predetermined region of the phosphorescent screen to the corresponding lens system. This visible light guide means is comprised of one or more baffles with apertures on them, the number of the apertures being equal to the number of the lens systems. In case a visible light guide means comprises two or more baffles, the nearer the baffle's location to the phosphorescent screen, the larger the aperture of the baffle. And, the baffles are disposed in a manner that they are parallel to the screen with a predetermined distance from each other and their apertures are co-centered.

Any material that can retain suitable strength and help decrease the weight of the apparatus, e.g., aluminum plate, glass epoxy, paper epoxy, Bakelite plate, etc. can be used for the baffle. However, the baffle nearest to the phosphorescent screen is preferably made of aluminum so as to shield the residual radiation light such as X-ray remnant remaining after transmission through the phosphorescent screen. In order to eliminate the scattered rays except for the visible light rays to be guided to the optical system, it is desirable to color the baffles in black which exhibits an excellent absorptivity for light.

The baffles are to be sized almost equal to the size of CCD arrays and/or of the optical system structure. The thickness thereof should be as thin as possible so long as it can support the baffle itself, in order to reduce the weight of the apparatus. The apertures formed on the baffles are preferably circular. As for the size of the apertures, the size of the apertures of the baffle nearest to the phosphorescent screen is approximate to the value resulted from division of the area of the phosphorescent screen by the number of the imaging elements (the area of one lens system or the area of one region of the phosphorescent screen that is allotted to one imaging element), while the diameter of the apertures of the baffle most distant from the screen, is approximate to the diameter of the lens system neighboring that baffle.

Although the number of baffles to be used and the spacing between each baffle are not limited, three or five baffles are preferably used, and the suitable spacing can be determined based on the distance between the phosphorescent screen and the optical system, and on the number of baffles.

The apparatus further comprises an optical system structure by which the visible lights guided by the baffles are condensed and transferred to an imaging element such as CCD. The optical system structure is a platelike structure with circular apertures on it for insertion of plural lens systems. In addition to the lens insertion apertures, several further apertures can be formed in the remaining area of the structure exclusive of the minimal area needed for supporting the structure, whereby the weight of the apparatus can be reduced. A lens system comprised of one or more lens is inserted into each of the circular lens insertion aperture.

Next to the optical system structure is disposed an imaging means such as CCD array comprising imaging elements corresponding to the lens systems disposed in the circular lens insertion apertures, and thereby generates electric signals consistent with the visible lights condensed by each lens system and produces a composite image on the basis thereof. The thickness of such optical system structure, though varies depending on the focal length of each lens system, is preferably 30~50mm. The material thereof is not limited to a specific kind so long as it can support the optical system, but a light metal such as aluminum is used preferably.

The radiation light of the present invention may include all lights or electromagnetic waves which can be converted into visible light after being radiated onto a phosphorescent screen for producing an image. In addition to X-ray that is widely used in medical field or measuring field, rays having shorter wavelengths than visible light, such as gamma ray, ultraviolet ray, etc. can also be included.

Brief Description of the Drawings

Fig, 1 shows an overall construction of an X-ray imaging apparatus with wide range according to the conventional art.

Fig. 2 shows combination of multiple lens systems and the imaging elements according to the conventional art.

Fig. 3 shows an overall construction of a digital imaging apparatus according to the present invention.

Fig. 4 illustrates a side view of RBEF used in the present invention and shows the routes of visible lights transmitted through the RBEF. Fig. 5 a is a plane view of a baffle used in the present invention and Fig. 5b is a sectional side view of an imaging apparatus employing three baffles, showing also the guiding routes for visible light.

Fig. 6 shows an optical system structure used in the present invention, wherein Fig. 6a is a plane view, Fig. 6b is a sectional side view taken along the ling A-A, and Fig. 6c is a sectional view taken along the line B-B.

Fig. 7 is a drawing illustrating the effect of the baffles, wherein Fig. 7a is an image acquired without use of a baffle while Fig. 7b is an image acquired using baffles.

Fig. 8 is an X-ray image of the inside of a solder acquired by an imaging apparatus according to the present invention.

Description of the Preferred Embodiment

A detailed description of the preferred embodiments of the present invention is given below, making reference to the accompanying drawings.

Fig. 1 is a block diagram of X-ray imaging apparatus with wide range according to the conventional art. The apparatus comprises an X-ray source 11 that emits X-rays onto an object 12; a phosphorescent screen 13 that absorbs the X-ray transmitted through the object and converts the same into visible light; an optical system comprised of plural lens systems 14 that condense the visible light emitted from the phosphorescent screen and transfer the same to an imaging means 17; an imaging means 17 comprised of plural imaging elements 16 that convert the visible lights condensed by each lens system into electric signals; a lead wire 18 that transfers the electric signals from each imaging element to computer system 19; and a computer system 19 that receives electric signals from each imaging element and produces a final X-ray image.

The phosphorescent screen is also called a scintillator, which generally indicates such materials which can convert the energy retained by permeable radioactive rays into ultraviolet or visible light detectable by a photo sensitive detector. Permeable radioactive rays herein may include X-ray, gamma ray, α -particle, β -particle, thermal neutron, etc. A common plastic scintillator is of polymer matrix applied with two kinds of organic phosphorescent constituents. The polymer base most commonly used are polystyrene and poly(vinyltoluene). The construction of a scintillator and the method for manufacture thereof are disclosed in detail in U. S. Patent. No. 5,968,425.

The above mentioned optical system comprises a plurality of lens systems, each of which comprises one or more optical lens. Each lens system condenses the visible light it receives and transfers the same to an imaging element beneath it, wherein these plural lens systems are disposed in two-dimensional arrays. Generally, the optical system is used for transferring the visible light emitted from a phosphorescent screen to an imaging means smaller than the phosphorescent screen. The kind and the number of the optical lenses are determined according to the de-escalation rate of visible light.

An imaging means refers in general to devices that can absorb visible light and generate an analogue or a digital electric signal corresponding to the intensity of the absorbed visible light. CCD or CTD(Charge Injection Device) is most commonly used as such device. A CCD, which generates electrons in proportion to the intensity and/or the number of photons of the entered visible light and transfers the generated electrons to a controller through a register, thereby converting the visible light into electric signal, is comprised of nXn units of pixels. As this CCD is now widely used in the field of image industry, a detailed description thereof is omitted.

As shown in the drawings, the imaging means 17 comprises CCD arrays in which multiple CCD elements 16 are disposed on a substrate. Each CCD element generates an electric signal for the partial image from the area allotted to it, using the visible light condensed by a lens system disposed thereon, and then transfers the electric signal so generated to computer system 19 through lead' wire 18 formed on the substrate. The computer system herein, which receives electric signals from each imaging element and produces a composite image, is comprised of an input/output interface, a storage means, and a controller, like an ordinary computer. The computer system receives image signals from each CCD element and combines the same in a mosaic manner to produce a composite image. Meanwhile, as each partial image is distorted and some portions of the image are overlapped in the verge thereof, such distorted and overlapped portions should be compensated. The relevant technique is disclosed in PCT/KR99/00305. Fig. 2 shows combination of the lens systems and the CCD elements according to the conventional art. Each lens system comprised of one or more lens 21 is housed in a square-pillared housing 22 and each housing is joined and fixed on the substrate so as to be situated on its corresponding CCD element 23 arranged on substrate 24. The visible light emitted from the phosphorescent screen is condensed by the lens system in the housing and transferred to a CCD element therebeneath. Fig. 2b illustrates CCD arrays serving as an imaging means, in which multiple CCD elements 23 are two- dimensionally arrayed on a substrate 24, and each CCD element is comprised of nXn units of pixels 25. It is the number of pixels that dominates the performance of a CCD element. Commonly, 1024X1024 units of pixels constitute a chip and each chip constitutes a CCD element. Each chip is sized to be tens of mm.

Fig. 3 shows an overall construction of a digital imaging apparatus with wide screen according to the present invention, exemplifying an X-ray imaging apparatus. As the conventional imaging apparatus, the X-ray imaging apparatus pursuant to the present invention comprises an X-ray source 31 as a light source; a scintillator 33 that absorbs the X-ray transmitted through object 32 and converts it into visible light; an optical system comprising a plurality of lens systems 39 each of which is comprised of one or more lens; CCD arrays 37 that convert the visible lights condensed by the optical system into electric signals; and a computer system 38 that receives partial image data from each CCD element and combines them to a composite image. However, the present invention further comprises a brightness enhancement film lens 34 which is attached to the scintillator and condenses the scattered visible lights emitted from the scintillator, onto a specific region. Still further, a visible light guide means comprised of one or more baffle 35 is also employed, which is interposed between the scintillator (or film lens) and the optical system to guide the visible light from one region of the scintillator to its corresponding lens system while shielding visible lights emitted from other regions of the scintillator. Still further, also included is an optical system structure 36 which can monolithically embody an optical system comprised of plural lens systems 39. The visible light guide means (baffle), the brightness enhancement film lens, and the optical system structure which are characteristics of the present invention will be described in detail below, in reference to Figs. 4 through 6. The apparatus used in the present embodiment yields a wide range X-ray image (17"X17"), which is much larger than the conventional size, 18 cm X 24 cm. Fig. 4, illustrating the configuration and the arrangement of a BEF used as a film lens, shows different routes of the visible lights traveling through the film depending on the incident angles. As described above, a variety of BEFs are currently being provided. In the present invention, a rounded BEF (RBEF) is used, which is commercially sold by 3M™ Innovative Properties Company under the name of RBEF- 8M and RBEF- 8 T This RBEF is characterized in that, unlike an ordinary BEF, the peaks of its prisms are made round, and is generally used in a planar display such as LCD for notebooks, which not only improves the brightness by 35-45%, but also increases the viewing angle, together with relief for cut-off. As shown in Fig. 4, the visible light rays emitted from the scintillator and incident on the film at an angle of less than 40 degrees with the perpendicular of the screen are refracted by the film to converge around the center (region I), while the visible light rays incident on the film at an angle of more than 40 degrees are double reflected back to the scintillator, see Region II, or first reflected and then refracted to be released to sideways, see Region III. Thus, an image with improved brightness and sharpness can be yielded through enhancement of the directivity of the scattered visible light rays emitted from the scintillator and through increase of the intensity of the visible light incident on the optical system and on the imaging system therebeneath.

Fig. 5 shows the construction and arrangement of the baffles serving as a visible light guide means in the present invention, wherein Fig. 5a is a sectional view of three baffles in position and Fig. 5b is a plane view of a single baffle.

A baffle has a thin platelike form, including uniform apertures 59 formed thereon. The number of the apertures is equal to the number of lens system or the number of CCD element (for the convenience of illustration, only three apertures across and two down, resulting in a total of six apertures are shown in the drawing). The drawing illustrates three baffles 51, 52, 53 interposed between scintillator 33 and optical system 54. The size of apertures formed in a baffle is different from that formed in other baffles. The larger the apertures of a baffle are, the nearer the baffle is disposed to the scintillator. The nearer a baffle disposed to the optical system, the smaller the apertures formed in the baffle.

Each lens system 55, 55', 55" is responsible for a specific region of the scintillator. In the drawing, lens system 55 is allotted to region I of the scintillator, lens system 55' to region II, and lens system 55" to region III, to condense visible lights from respective regions and transfer the same to respective CCD elements. For, example, only the visible light emitted from region II should be incident on lens system 55', but in fact, the visible lights emitted from regions I and III are partially incident on lens system 55' due to heavy scatter of the visible lights emitted from the scintillator. Such visible lights serve like background noise to the image in region II, which effect should be eliminated. To this end, a baffle is employed. In case three baffles are arranged as in the drawing, the visible lights emitted from each region of the scintillator can be directed to their respective lens systems only.

The apertures formed in the baffle nearest to the scintillator are sized to be approximately the same as the area of a region of the scintillator and the apertures of the baffle most distant from the scintillator are sized to be a little larger than the aperture of the object lens of the lens system.

As mentioned above, the baffle nearest to the scintillator is made of aluminum and the rest are made of Bakelite. Each baffle is colored in black so as to effectively absorb the lights other than the guided visible light. The size of the apertures and the distance between each baffle can be varied in a suitable manner depending on the area of each region, incident aperture of the lens system, and the spacing between the scintillator and each lens system.

Fig. 6 illustrates an optical system structure used in the present invention, wherein Fig. 6a is a planar view and Figs. 6b and 6c are sectional view taken along the lines A-A and B-B of Fig. 6a, respectively. The optical system used herein comprises a total of 64 (8X8) lens systems, each of which has 6 lenses.

The optical system structure illustrated in the drawing is comprised of a plate 61 having a plurality of lens insertion apertures 62 for each lens system. In addition to the lens insertion apertures, one or more weight-reducing apertures 63 can be formed thereon. The weight-reducing aperture 63 is formed in the surplus area of the plate excluding the minimal area needed for supporting the structure, in order to reduce the weight of the structure. The optical system structure as shown in Fig. 6a has sixty-four circular lens insertion apertures 62 and a total of nine weight-reducing apertures 63 formed in elongated manner.

As shown in Figs. 6b and 6c, the lens insertion apertures are configured in step form, an aperture nearer to CCD element being made smaller, so that six lenses with different apertures can be inserted and fixed in the lens insertion apertures. The apertures of the lenses are about 27mm, 23.98mm, 19.43mm, 11.352mm, 10.344mm, and 8.0 mm, respectively. Further, a square recess 64 is formed nearest to CCD in order to allow a CCD element 58 corresponding to a lens system to be inserted therein. The CCD element used herein comprises a CCD chip of 14.6inni 14.6mDi that has 1024X 1024 units of pixels.

Disposed beneath the optical system structure is a CCD array substrate 57, in which the foregoing sixty-four CCD elements 64 are two-dimensionally arrayed. The optical system structure and the CCD array substrate are coupled through a screw bore 65 that is formed on the substrate. Fixed on the CCD array substrate are sixty-four CCD chips, and a wire is printed on the substrate to transfer electric signals from each CCD chip, to a computer system.

This optical system structure is comprised of an aluminum plate of which the size is 480m X480mmX47mm in widthXlengthXthickness. The lens insertion apertures are arranged checkerwise so as for each aperture to be distanced from neighboring apertures by 54mm. However, the size, thickness, and the material of the plate are not limited to the above but can be varied depending on different needs.

Conventionally, as illustrated in Fig. 2, each lens system is housed in a separate housing and each housing is fixed on the CCD array substrate in a manner to cover up the CCD element. With this configuration, each lens system and coupling of it to CCD element should individually be inspected and adjusted in case of system failure occurrence such as eccentric axes of the lens system caused by external impact, which work is quite burdensome. Further, as the housing that encloses the lens system is individually fixed on the substrate, overall durability of the apparatus against external environments (temperature, impact, vibration, etc.) is lowered. In contrast, use of the aforementioned monolithic optical system structure not only improves the mechanical durability of the apparatus due to its structure that firmly supports each lens system but also prevents lens system disturbance caused by external environments as the lenses are inserted in lens insertion apertures.

Fig. 7 is a drawing to show the change in X-ray image by use of a baffle wherein Fig. 7a is an X-ray image of the grip of a solder without using a baffle and Fig. 7b is an image of the same object obtained using a baffle mounted in the apparatus.

It can be seen from the drawings that although the image made without a baffle (Fig. 7a) is brighter than the image obtained with a baffle (Fig. 7b), the resolution thereof is so poor that its edges look blurred and vague. This is because, as already described above, a lens system and a CCD element which are allotted to receive only the visible light emitted from a specific region of the scintillator also inevitably receives visible lights emitted from neighboring region of the scintillator, and these lights act like background noise.

On the other hand, in case a baffle is mounted, although the overall brightness of the image is a bit decreased, the edges of the image look so clear, which exhibits a higher resolution. With respect to processing of the image taken, a high level of background noise makes the image processing difficult, if with a brighter image, whereas somewhat dark but dynamically wide-ranged image yields a final composite image of better quality. In this respect, use of a baffle can provide an image with higher resolution.

Fig. 8 is an image of the body of a solder taken by using the X-ray imaging apparatus pursuant to the present invention, showing that the overall image is clear and the resolution thereof, especially at the edges, is excellent.

Industrial Applicability

The digital imaging apparatus according to the present invention can provide an image with improved resolution, brightness, and contrast, compared to the conventional apparatus. By using an RBEF, scatter of visible light emitted from a phosphorescent screen can be reduced and directivity of the light can be improved, whereby sharpness and brightness are enhanced.

Further, by using a baffle that can screen the rays of visible light emitted from a phosphorescent screen and transmit only the desired rays of light to a corresponding lens system, sharpness and resolution of the image can be increased additionally.

Still further, by providing a monolithic optical system structure that can firmly support a plurality of lens systems, damage of the apparatus caused by external environments (vibration, temperature, impact, etc.) can be minimized and mechanical stability of the apparatus can be enhanced.

Claims

What is claimed is:

1. A digital imaging apparatus comprising a light source that generates radiation light and emits the same onto an object; a scintillator that absorbs the light transmitted through the object and converts the same into visible light; an optical system comprising a plurality of lens systems by which the visible light generated and emitted from the scintillator is made incident on an imaging means; an imaging means comprising a plurality of imaging elements that generate electric signals consistent with the visible light radiated from the optical system; and an image-combining means that receives the electric signals and produces a final image; wherein said digital imaging apparatus further comprises a visible light guide means that is interposed between said scintillator and optical system to guide only the visible light emitted from a specific region of the scintillator to a corresponding lens system; and said visible light guide means comprising at least one baffle that is disposed parallel to said scintillator and has apertures on it, the number of said aperture is equal to the number of said lens system.

2. The digital imaging apparatus as set forth in Claim 1, wherein said visible light guide means is comprised of two or more baffles with differently sized apertures thereon, a baffle nearer to said scintillator having larger apertures, and said baffles are disposed in a manner that they are distant to each other by a predetermined space and further that they are parallel to said scintillator to make their apertures coaxial.

3. The digital imaging apparatus as set forth in any one of Claim 1 or Claim 2, wherein said baffle is made of at least one of materials, aluminum and Bakelite, and is colored in black.

4. The digital imaging apparatus as set forth in any one of Claim 1 through

Claim 3, wherein a brightness enhancement film lens (BEF) is further included that is interposed between said scintillator and baffle and transmits only the visible light incident on it at less than a predetermined angle with the perpendicular of said scintillator, among all rays of the visible light generated and emitted from the scintillator, said film lens being an array of multiple prisms on a transparent substrate, said prisms being arrayed in an adjacent manner and having rounded peaks.

5. A digital imaging apparatus comprising a light source that generates radiation light and emits the same onto an object; a scintillator that absorbs the light transmitted through the object and converts the same into visible light; an optical system comprising a plurality of lens systems by which the visible light generated and emitted from the scintillator is made incident on an imaging means; an imaging means comprising a plurality of imaging elements that generate electric signals consistent with the visible light radiated from the optical system; and an image-combining means that receives the electric signals and produces a final image, wherein said optical system comprises a plate structure having plural lens insertion apertures for plural lens system; and plural lens systems that are formed by inserting one or more lens into said lens insertion apertures.

6. The digital imaging apparatus as set forth in Claim 5, wherein said plate structure has weight-reducing apertures that are formed in the remaining area of the plate structure excluding the minimal area needed for supporting the optical system.

7. The digital imaging apparatus as set forth in Claim 5, wherein said lens insertion apertures are configured in step form, an aperture nearer to imaging element being made smaller so as for two or more lenses with differently sized apertures are inserted in the lens insertion apertures, and a square recess is formed at the end of the apertures to allow an imaging element to be inserted into the recess.

8. The digital imaging apparatus as set forth in Claim 5, wherein said plate structure is made of aluminum.

9. The digital imaging apparatus as set forth in Claim 5, wherein said optical system comprises a total of sixty-four (eight in width and eight in length) lens systems each of which has six lenses, and an imaging means which is CCD arrays with sixty- four CCD chips arrayed on a substrate.

10. The digital imaging apparatus as set forth in any one of Claim 5 through Claim 9, which further comprises a visible light guide means that is interposed between said scintillator and optical system to guide only the visible light emitted from a specific region of the scintillator to a corresponding lens system; said visible light guide means comprising at least one baffle that is disposed parallel to said scintillator and has apertures on it, the number of said aperture is equal to the number of said lens system.

11. The digital imaging apparatus as set forth in any one of Claim 5 through Claim 9, wherein a brightness enhancement film lens (BEF) is further included that is interposed between said scintillator and optical system, and transmits only the visible light incident on it at less than a predetermined angle with the perpendicular of the scintillator, among all rays of light emitted from the scintillator, said film lens being an array of multiple prisms on a transparent substrate, said prisms being arrayed in an adjacent manner and having rounded peaks.

12. The digital imaging apparatus as set forth in Claim 10, wherein a brightness enhancement film lens (BEF) is further included that is interposed between said scintillator and baffle and transmits only the visible light incident on it at less than a predetermined angle with the perpendicular of the scintillator, among all rays of light emitted from the scintillator, said film lens being an array of multiple prisms on a transparent substrate, said prisms being arrayed in an adjacent manner and having rounded peaks.