More particularly, the present invention relates to an optical tube assembly and a reflective photographing apparatus for photographing a photographic image to implement virtual reality, which solves distortion and mismatch occurring at image borders when several images photographed by a camera are merged, and also relates to a method for merging photographic images photographed using the camera or the reflective photographing apparatus adopting such an optical tube assembly.

BACKGROUND ART Recently, World Wide Web (WWW) broadens its application more owing to development and improvement of the description language expressing 3-dimensional virtual space. For example, a user may works on the street or purchases an article at a store in a virtual space as if he/she is in a real world. A so-called VRML (Virtual Reality Modeling Language), which enables realization of such a virtual space, is well disclosed in"Learn About VRML: Building and Browsing Three-Dimensional

Computer Space" [1St ed. 3.25. 1996, Prentis Hall] written by Mark Pesco. In order to realize a virtual space with the VRML technique, high technologies such as 3-dimensional rendering or texture mapping are required.

In order to give the better sense of the real to a user, it is required that 3-dimensional virtual space is implemented on the basis of a real space. To move the real space to a virtual space, a plurality of photographic images photographed by an optical camera are traditionally merged. The photographic image based virtual reality rapidly shows a plurality of digitalized photographic images as a user selects, or according to movement of the user, thereby making the user feel as if he/she watches a real space. As mentioned above, the photographic image based virtual reality may obtain the sense of perspective since each photographic image already has optical perspective representation. Thus, the photographic image base virtual reality is better than animation which has relatively worse reality.

Generally, the photographic image based virtual reality is implemented using a panorama method and an object method. The panorama method generates one sheet of long panorama image by photographing a real scene in several photographs with rotating a camera positioned at a certain height at 360 degrees, and then stitching the photographic images to eliminate an overlapped portion. The image stitching may be realized using programs such as Photo Vista produced by LivePicture, Quick Stitch produced by Enroute Imaging, and Visual Stitcher produced by PanaView. The panorama image produced as above may be displayed by inserting a corresponding plug-in in a web browser or executing a Java, and it makes a user as if he/she watches around a real scene with turning his/her head. Meanwhile, the object method

photographs an object with rotating a camera at 360 degrees around the object and then merges images with the use of an object stitching program. The object stitching program may be Reality Studio produced by LivePicture, or QuickTime VR produced by Apple.

In addition to the panorama image and the object image, an image which is continuously enlarged or reduced according to movement of a user who works on or changes his/her course in a virtual reality may be realized on the basis of photographic images. Inventor of this application has already suggested a method for implementing a virtual space by merging a plurality of photographic images, photographed by an optical camera in Korean Patent Application No. 10-2002-08817. According to the document, a plurality of source images obtained by photographing a real space with an optical camera is cut in a predetermined size to keep mutual continuity, and then produced into subframes having a predetermined reduction rate with each other in correspondence to the source images. And then, if a user inputs an event signal by clicking a mouse, the subframes move on the monitor watched by the user with the corresponding images being enlarged or reduced, thereby displaying a virtual space.

As mentioned above, stitching the photographic images photographed by a camera is commonly conducted to implement the photographic image based virtual reality. The aforementioned stitching programs unite various images to make one wide-ranged omniview up to 360 degrees. The stitching process includes various steps such as correction of camera angle and tilt between successive images overlapped with each other, image arrangement, and texture mapping. In addition, the stitching program may project various linear images into a spherical, cylindrical or cubic shape.

At this time, it is important to connect the images without distortion and mismatch.

Distortion generated when the photographic images are merged is generally caused from the angle of view of the optical camera, which are well described below with reference to FIGs. la and lb.

FIG. la is a schematic view showing that an optical camera Co having an angle of view ((H)) photographs an image IL at a position PL, and then photographs an image IR after laterally moving to a position PR. Reference numerals OL and OR designate figures projected to the images IL and IR respectively for an object OB which is photographed from both positions PL and PR. Referring to FIG. la, the object OB is photographed with being inclined left on the basis of the front in the image IL, while the object OB is photographed with being inclined right in the image IR. Thus, if the images IL and IR are merged by eliminating an overlapped portion and then stitching simply according to the pixel information, the object OB is somewhat distorted in the merged image, differently from its real looks.

Such image distortion is identically shown in the front and back movement of the camera as well as in the lateral movement, as shown in FIG. lb. In FIG. lb, the camera Co photographs a scene including the object OB at a position PB to get an image IB, and then the camera Co advances as much as a predetermined distance and photographs the object OB at a position PF to get an image IF. In this case, if an overlapped portion of two images IB and IF is eliminated according to a predetermined reduction rate and two images IB and IF are then merged, it is found that the image including the object is distorted as in the case of FIG. la.

Such image distortion and mismatch are inevitably generated since the optical

camera has an angle of view. That is to say, since the camera has an angle of view, if the position of the camera is changed against the object, a minimum incidence angle from the object to the camera is also changed. Thus, if images photographed with different angles of view are merged, the image distortion is unavoidable.

DISCLOSURE OF INVENTION The present invention is designed to solve such problems of the prior art, and therefore an object of the invention is to provide an optical tube assembly for photographing a photographic image, which is capable of photographing images without distortion even though the images are merged to implement a photographic image based / virtual reality, and a reflective photographic apparatus for replacing the tube.

Another object of the invention is to provide a method for merging photographic images, photographed by the optical tube assembly or the reflective photographic apparatus, without distortion in order to implement a photographic image based virtual reality.

In order to accomplish the above object, the present invention provides a BRIEF DESCRIPTION OF THE DRAWINGS These and other features, aspects, and advantages of preferred embodiments of the present invention will be more fully described in the following detailed description,

taken accompanying drawings. In the drawings: FIG. la is a schematic view showing distortion of merged images photographed by an optical camera from laterally different positions according to the prior art; FIG. 1b is a schematic view showing distortion of merged images photographed by an optical camera from longitudinally different (or, front and back) positions according to the prior art; FIG. 2 is an exploded perspective view showing an optical tube assembly according to the embodiment of the present invention; FIG. 3 is a side sectional view showing the optical tube assembly according to an embodiment of the present invention; FIGs. 4a to 4c show lens arrangements of the optical tube assembly according to the embodiment of the present invention, in which FIG. 4a shows the case that an angle of view (0) is zero, FIG. 4b shows the case that an angle of view ((H)) is positive, and FIG. 4c shows the case that an angle of view (0) is negative; FIG. 5a is a schematic view for illustrating the process of merging images photographed from laterally different positions by a camera adopting the optical tube assembly according to the embodiment of the present invention; FIG. 5b is a schematic view for illustrating the process of merging images photographed from longitudinally different (or, front and back) positions by a camera adopting the optical tube assembly according to the embodiment of the present invention; FIG. 6 is a perspective view schematically showing arrangement of lens adopted in an optical tube assembly according to another embodiment of the present invention;

FIG. 7a is a schematic view for illustrating the process of merging panorama scenes with the use of a camera adopting the optical tube assembly of FIG. 6; FIG. 7b is a schematic view for illustrating the process of merging object images with the use of a camera adopting the optical tube assembly of FIG. 6; FIG. 8 is a schematic plane view showing a 3-dimensional real space for illustrating the process of photographing images according to another embodiment of the present invention; FIG. 9 shows an example of photographing a source image with the use of the camera adopting the optical tube assembly according to a preferred embodiment of the present invention ; FIG. 10 is a diagram for illustrating the method of photographing a 3-dimensional real space according to a preferred embodiment of the present invention; FIG. 11 is a diagram showing an example of merging source images according to a preferred embodiment of the present invention ; FIG. 12 is a diagram showing an example of implementing a virtual reality space with the use of the merged image of FIG. 11 according to a preferred embodiment of the present invention; FIG. 13 is a diagram showing an example of an omni-directional panorama image merged into a cubic shape according to a preferred embodiment of the present invention; FIG. 14 is a schematic view showing a development figure of the merged cubic image of FIG. 13; FIG. 15 is a diagram showing an example of a panorama image merged with

each row image according to a preferred embodiment of the present invention; FIG. 16 is a diagram showing an example of implementing a virtual reality space with the use of the merged image of FIG. 15 according to a preferred embodiment of the present invention; FIG. 17 is a diagram showing an example of displaying a virtual reality space on a monitor according to a preferred embodiment of the present invention; FIGs. 18a and 18b show an example of photographing a source image with the use of a camera adopting the optical tube assembly according to another embodiment of the present invention; FIG. 19 is a plane view schematically showing a 3-dimensional real space for illustrating the process of photographing an image according to still another embodiment of the present invention; FIG. 20 is a diagram showing an example of a panorama image merged with each row image according to still another embodiment of the present invention ; FIG. 21 is a schematic side view showing a reflective photographing apparatus according to another aspect of the present invention; FIGs. 22a to 22c show arrangement of a concave reflective mirror of the reflective photographing apparatus and a camera according to an embodiment of the present invention, in which FIG. 22a shows the case that an angle of view (0) is zero, FIG. 22b shows the case that an angle of view (#) is positive, and FIG. 22c shows the case that an angle of view (#) is negative, respectively.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

According to the present invention, an image in a real space is photographed with the use of an optical tube assembly which is designed not to generate distortion when the images are merged. Such an optical tube assembly may be simply attached to a general camera having a common angle of view.

An optical tube assembly according to a preferred embodiment of the present invention is shown in FIGs. 2 and 3. Referring to FIGs. 2 and 3, the optical tube assembly of the present invention has a cylindrical case 10 including a lens and other components therein.

According to the present invention, a plurality of lenses for changing an incident light path are included in the cylindrical case 10. In this embodiment, the lenses are composed of a convex lens 20 for condensing incident light, and a concave lens 30 for diverging incident light. Preferably, the convex lens 20 and the concave lens 30 are installed in the case 10 with their outer circumferences being gripped by support rings 21 and 31 and combination rings 22 and 32. As described later, the convex lens 20 and the concave lens 30 are subsequently arranged with a predetermined distance in order to make a suitable light path so that the light entering into the cylindrical case 10 is condensed by the convex lens 20 and then refracted by the concave lens 30 to enter the opening of an objective lens holder 2 of a camera 1. Reference numeral 40 designates a ring cap combined to the rear end of the cylindrical case 10.

The optical tube assembly according to the present invention is detachably combined with the objective lens holder 2 of a general camera. Such detachable

combination may be realized using a well-known technique, for example by combining a camera filter thereto. According to this embodiment, a screwed protrusion 31b is formed on the support ring 31 of the concave lens 30, and the screwed protrusion 31b is combined with a screw formed on the front inner circumference of the objective lens holder 2 of the camera 1 in order to combine the optical tube assembly with the camera.

It should be understood that the optical tube assembly may be combined with the objective lens holder of the camera in various ways, not limited to the above example.

According to the present invention, the lenses are configured so that an angle of view ((9) against an object or a scene to be photographed. is zero. The term"angle of view99 used in this specification and claims is defined as an angle viewed or photographed by the camera when the camera photographs an object or a scene.

Specifically, a camera whose angle of view (0) is positive may photograph a scene over a wider range than a section of the objective lens or the objective lens holder, which is corresponding to a commonly-used conventional camera. That is to say, an incident light condensed from the object to the objective lens is projected on a film of the camera.

For example, a fisheye lens whose angle of view (0) is 180 degree may photograph an entire hemispherical view in one image. Meanwhile, a camera whose angle of view (0) is negative may photograph a scene over a narrower range than a sectional area of the objective lens or the lens holder. That is to say, an incident light diverged from the object to the objective lens is projected on a film of the camera. In addition, if an angle of view (0) is zero, only a scene viewed over the same area as the section of the objective lens or the lens holder may be photographed. It means only the scene incident in parallel from the object is projected on the film of the camera.

FIG. 4a shows arrangement of the lenses adopted in the optical tube assembly according to the present invention. FIG. 4a shows only the lenses schematically, and other components are not shown for the convenience of description. Referring to FIG.

4a, the convex lens 20 and the concave lens 30 are arranged so that an angle of view (0) of the optical tube assembly of the present invention is zero. That is to say, the convex lens 20 and the concave lens 30 are positioned with a distance Do so that only the light incident from an object or a scene in parallel is input on the film of the camera, but a condensed light or a diverged light is not projected onto the film of the camera. Thus, an angel of view (0) of the optical tube assembly according to the present invention is zero, and the camera adopting this optical tube assembly may photograph only a front view seen within the range corresponding to the size of the optical tube camera lens or the section of the cylindrical case. The distance Do between the lenses may be calculated and set so that an angle of view (e)) is zero from a focus. distance of each lens.

Though it is described that the lenses are composed of a convex lens and a concave lens, it should be understood that the lenses may be configured to have various arrangements, not limited to that example, if an angle of view (@) of the optical tube assembly becomes zero. For example, three or more lenses may be arranged to make an angle of view (0) be zero.

Now, an image obtained by actual photographing of the camera adopting the optical tube assembly configured as above is described. FIG. 5a shows a result of photographing images while a camera adopting the optical tube assembly according to the present invention is laterally moved. Here, the camera and other components are not depicted in the figure for convenience. Referring to FIG. 5a, since the angle of

view (@) of the optical tube assembly is zero, an image I'L photographed by the camera at a position PL is a region corresponding to the light incident to the lens 20 from the object in parallel. In addition, an image I'R photographed after moving the camera to a position PR is also a region corresponding to the light incident to the lens 20 from the object in parallel. Thus, in case of a specific object O, only a front figure is always photographed though the camera is moved laterally, not inclined as in case of the conventional case. As a result, if two images I'L and I'R photographed at different positions are merged with eliminating their overlapped portion, no image distortion is generated.

FIG. 5b shows that the camera adopting the optical tube assembly according to the present invention photographs images while being moved front and back. As shown in FIG. 5b, images I'B and I'F photographed at different positions Pn and PF are all obtained by projecting the light incident to the lens from the object in parallel on a film. Thus, similar to the above case, though the camera advances from the position PB to the position PF, only one side of the object OB is photographed, not inclined.

According to one embodiment of the present invention, the lens may be a plano-cylindrical lens as shown in FIG. 6. The lens shown in FIG. 6 is composed of a plano-cylindrical concave lens 20'and a plano-cylindrical convex lens 30'. As well known in the art, the plano-cylindrical lens is used for converting a point image into a line image, and broadly used for line-detector-array illumination as in a laser printer.

If the plano-cylindrical concave and convex lenses 20'and 30'are arranged in parallel as shown in FIG. 6, an object may be photographed with only the length L being changed, without any change in the width W. That is to say, in the optical tube

assembly of the present invention having the plano-cylindrical lenses 20'and 30', an angle of view (0) is zero in the width W direction of the object, but the angle of view (0) is positive in the length L direction of the object.

According to an optical tube assembly according to still another embodiment of the present invention, at least one of the lenses which convert a light path may changes its position in order to adjust an angle of view (0). For this reason, the optical tube assembly of the present invention has a moving unit for moving at least one of the lenses, which is well shown in FIGs. 2 and 3 as an example.

Referring to FIGs. 2 and 3, the moving unit includes an inner cylinder 11 installed in the cylindrical case 10 and having a plurality of elongated holes 11a formed in a longitudinal direction, and a protrusion 21a protruded on the outer circumference of the support ring 21, which supports the convex lens 20, and having a rack formed on its upper surface. The inner cylinder 11 is smaller than the inner circumference of the cylindrical case 10 and larger than the outer circumference of the support ring 21.

Thus, when the support ring 21 is installed in the inner cylinder 11, the protrusion 21a is positioned in the elongated hole 11a so that the inner cylinder 11 may slide in the longitudinal direction. At this time, a screw 10a is formed on the inner circumference of the cylindrical case 10 and screwed to the rack of the protrusion 21a. Then, the support ring 31 for supporting the concave lens 30 is interposed to the rear end of the inner cylinder 11 and combined thereto by screwing a screw 41 into a hole 31a. The inner cylinder 11 inserted into the cylindrical case 10 is supported by a flange 40 combined by a screw 41 to a hole 10b formed in the rear end of the cylindrical case 10.

In such a combined state, if the cylindrical case 10 is rotated, the rotating

movement of the cylindrical case 10 is converted into a linear reciprocating movement of the support ring 21 and the convex lens 20 supported by the support ring 21 by means of the screw 10a formed on the inner circumference of the cylindrical case 10 and the rack formed on the protrusion 21a. Thus, if a user rotates the cylindrical case 10 in a clockwise or counterclockwise direction, the protrusion 21a reciprocates with sliding along the elongated hole 11a of the inner cylinder 11. Accordingly, the convex lens 20 becomes relatively more distant from or nearer to the fixed concave lens 30.

Preferably, when the cylindrical case 10 is rotated, an elastic member 13 such as rubber may be provided on the outer circumference of the cylindrical case 10 in order to prevent slipperiness.

Though the moving unit is described according to specific drawings and embodiments, it should be understood that the moving unit may adopt other modifications capable of changing a distance between the lenses using a well-known means, not limited to the above case.

According to the optical tube assembly of the present invention, the angle of view (0) may be adjusted according to a relative distance between the lenses, as shown in FIGs. 4a to 4c as an example.

FIG. 4a shows a lens arrangement in the case that an angle of view (0) is zero.

That is to say, the distance Do between the lenses 20 and 30 is set so that an angle of view (@) is zero.

FIG. 4b shows the case that an angle of view (E)) is positive. That is to say, if the cylindrical case 10 of the optical tube assembly shown in FIG. 1 is rotated in one direction to make one lens (or, the convex lens) 20 move toward the other lens (or, the

concave lens) 30, the light path is changed to make an angle of view ((9) into a positive value. In this case, the distance D1 between the lenses 20 and 30 becomes smaller than the original distance Do.

Meanwhile, FIG. 4c shows the case that an angle of view (G)) is negative. That is to say, if the cylindrical case 10 of the optical tube assembly is rotated in a reverse direction to make one lens (or, the convex lens) 20 move far away from the other lens (or, the concave lens) 30, the light path is changed to make an angle of view (#) into a negative value. In this case, the distance Da between the lenses 20 and 30 becomes larger than the original distance Do.

The optical tube assembly configured as mentioned above according to the present invention may adjust an angle of view ((H)) selectively according to the kind of a desired merged image. For example, as shown in FIG. 7a, when desiring to merge a panorama image, a user combines the optical tube assembly of the present invention to a camera and then adjusts the arrangement of lenses so that an angle of view (0) has a positive value. Then, since the light incident to the object from the center 0 is perpendicular, though two images le, and 102 photographed at different angles are merged with eliminating an overlapped image Iov, image distortion is not generated.

FIG. 7b shows an example that an object source image is obtained by continually photographing an object with rotating around the object positioned at the center O. In this case, in the optical tube assembly of the present invention, the lens arrangement is adjusted so that the angle of view (#) has a negative value, or the light path linking from the object to the lens passes through the center O. Then, the light incident from the camera lens (not shown) to the object is perpendicular like the above case, though two

images I «, 3 and I#3 photographed at different angles are merged with eliminating an overlapped image lov, image distortion is not generated Now, a method for photographing a real space with the use of the optical tube assembly according to the present invention and then making a virtual space by merging the photographed images is described.

FIG. 8 is a plane view schematically showing a space like a hallway which is connected from a position °l to a position °2, and then perpendicularly curved and connected to a position 03. According to the present invention, such a complex space may be implemented by merging 3-dimentional panorama image and collimated light images photographed using the optical tube assembly whose angle of view ((3) is zero.

FIG. 9 shows an example of photographing a unit collimated light image according to a preferred embodiment of the present invention. In order to photograph the unit collimated light image, the optical tube assembly of the present invention is attached to a general optical camera. Then, the lens arrangement is adjusted with the use of the moving unit to adjust the lens distance (Do) so that the angle of view (0) becomes zero as shown in FIG. 4a. The lenses used in this embodiment are plano-cylindrical lenses 20'and 30'. In this case, the plano-cylindrical lenses 20'and 30'are arranged so that the angle of view ((H)) is zero in a perspective direction, i. e. in a direction that a user moves front or back. That is to say, a width W direction of the unit image lu photographed by the camera Co is identical to the perspective direction, e. g. a direction that a camera (or, a user) moves in the hall way, and the angle of view (#) is zero in this direction. Meanwhile, an angle of view (0) in a length L direction perpendicular to the width W direction of the unit image lu (i. e. a rotating direction of

the camera as described later) is made to have a positive value so that a relatively wider range may be photographed. The length L direction of the image Iu is identical to a rotating direction of the camera for photographing. Thus, like the example of FIG. 7a, though the images photographed with rotating a camera whose angle of view ((H)) is positive at the center are merged, image distortion is not generated.

FIG. 10 is a diagram for illustrating a method for photographing the space shown in FIG. 8 with the use of the camera adopting the optical tube assembly having the above-mentioned lens arrangement. The camera (not shown) is positioned on the centerline Lo of the hallway. At this time, the lenses of the optical tube assembly are arranged so that the angle of view ( (D) is zero in a perspective direction, i. e. a direction of the centerline Lo of the hallway, while the angle of view ( (D) is positive. in a lateral direction perpendicular to the perspective direction. In this case, the photographing direction of the camera is perpendicular to the surface of the object, and at 180 degrees to the ground (see FIG. 9).

In this state, the ceiling of the hallway is photographed to obtain a top source image Isl-T in a first row. Then, the camera is laterally rotated as much as 90 degrees and then photographs a right source image Iso-R of the same size. Then, the camera is downwardly rotated to photograph a bottom source image Isi-B, and then rotated to photograph a left source image IS1-L-In such a way, a plurality of first row source images Isi-T, Isi-R, Isi-B and IS1-L may be obtained with rotating the camera at a right angle in an advancing direction (or, a perspective direction). Though this embodiment is described to generate four source images, it will be understood to those skilled in the art that the rotating angle of the camera and the number of photographed images may be

suitably adjusted according to the lateral angle of view (0) of the optical tube assembly attached to the camera.

If the photographing for the first row is completed, the camera is advanced in the perspective direction along the centerline Le, and then source images Is2-T, Is2-R, IS2-B and IS2-L for the second row are obtained in the same way. At this time, the camera is preferably advanced as much as a distance capable of photographing the second row source image IS2 to be partially overlapped with the first row source image Is, as shown by a dotted line in FIG. 8 so that no area is missed.

The camera photographs intermittent and continual rotating images with advancing as much as a predetermined pitch in the same way to generate third to seventh row source images IS3-T, IS3-R, IS3-B and LS3-L to IS7-T ; IS7-R, IS7-B and Is7-L. The term"intermittent and continual rotating images"used in the specification and claims is defined as a plurality of images photographed by a camera which advances by a predetermined pitch step by step with rotating so that the images are partially overlapped, and it should be interpreted based on the definition.

The source images IS1-T to IS7-L are merged with each other or stitched to have the arrangement of FIG. 11 after overlapped portions are eliminated. Specifically, in each row shown in FIG. 10, overlapped portions between the top, right, bottom and left source images Isi-T, IS1-R, IS1-B and IS1-L of the first row are suitably eliminated and then the source images are stitched. At this time, since the angle of view (#) of the camera is positive, the light incident to each of the source images Isl-T, Isl-R, Isi-B and Is1-L is always perpendicular. Thus, though the source images Isi-T, ISl-R, Isi-B and Isi-L are merged with eliminating their overlapped portions, image distortion is not generated.

By using such lateral image merging, the first to seventh row images Il to 17 are obtained.

Subsequently, each row images I, to I7 are merged in an advancing direction, i. e. a perspective direction. In this case, the images are also simply stitched with eliminating their overlapped portions. Here, since the angle of view (0) is positive in the advancing direction due to the lens arrangement of the optical tube assembly, the light incident to each row image Il to 17 from the camera is always perpendicular. Thus, the same object is photographed at the same angle, not inclined, even in different rows.

As a result, though each of the row images I1 to I7 is simply stitched, image distortion is not generated.

FIG. 11 schematically shows the process of merging all of the source images in the aforementioned method. As shown in FIG. 11, each of the row images Il to I7 and the top, right, bottom and left images IT, IR, IB and IL may be merged without distortion.

Such image stitching may be accomplished using a well-known stitching program, as mentioned above. The merged image may be configured into a 3-dimensional virtual space as shown in FIG. 12 by using a separate program.

According to the present invention, the images photographed using an optical tube assembly whose angle of view (0) is zero may be merged with common panorama images to implement a perfect virtual reality space. Referring to FIG. 8 again, in order to obtain the panorama images, a camera whose angle of view (E)) is positive at the center position °l is used to photograph an omni-directional scene, and then obtains a plurality of source images. For photographing at this time, as an example ; the camera is oriented vertically upward on the basis of the ground and then photographs the top

source image, and then is inclined about 45 degrees and then photographs top-midway panorama source images in order with rotating. Then, the camera is positioned in parallel with the ground and then photographs midway panorama source images with rotating, and then is rotated with being inclined downward about 45 degrees and obtains bottom-midway panorama source images, and then finally is oriented downward toward the bottom and photographs bottom source images.

Such source images are digitalized and then merged with each other by means of a stitching program. Preferably, the panorama source images may be merged and then converted into a cubic shape shown in FIG. 13. For example, QuickTime VR produced by Apple makes a plurality of panorama source images be stitched into a cubic merged panorama image Icu, which may be operated on Web by means of a program such as Shockwave produced by Macromedia.

Referring to FIG. 8 again, on a plane Pol which pass through the'center 1 and is perpendicular to an advancing direction of the camera (or, a user), i. e. a perspective direction, the first row image I1 and the cubic panorama image Icu are all photographed by means of collimated incident light. Thus, though two images are merged, image distortion is never generated at their border (expressed by a dotted line in FIG. 13). In addition, the images positioned right over the plane Pol as a border should be eliminated during the merging process since they are overlapped with the first row image Il. This may be easily understood when referring to FIG. 14 which shows the cubic panorama image Icu in a virtual development view. That is to say, the cubic panorama image Icu, which is to be continuously stitched with the first row image Il, is corresponding to the entire side A image and half of the sides B, C, D and E expressed by hatch.

Accordingly, the overlapped portions are eliminated, and then the cubic panorama image Icu and the first to seventh row images Ij to I7 are merged as shown in FIG. 15.

The merged image may be configured as shown in FIG. 16 by means of the aforementioned program, thereby implementing a 3-dimensional virtual reality space.

At the positions 02 and 03, the cubic panorama image and each row image may be merged in the same way.

FIG. 17 shows an example of a virtual reality space, seen from the position 02 toward the position Ot in FIG. 8. For example, an image in which the panorama image Icu and each row image Il to I7 are merged is displayed in a screen margin M of a monitor, a user watches. At this time, the seventh row image I7 nearest to the user is relatively enlarged, and the images are gradually reduced at a predetermined ratio as they are more distant from the user. Preferably, the images are set in correspondence to sub-frames, which are obtained by dividing the screen region, so the images may be enlarged or reduced in a sub-frame unit according to an input signal of the user. This technique is disclosed in Korean Patent Application No. 10-2002-08817 filed by the same inventor as this application, and it should be considered as one embodiment to which the aspect of the present invention may be applied.

In this embodiment, though each row is an image photographed by the camera in a vertical direction, the image which is once stitched may generate an image seen from a different direction by using an image-based rendering technique.

Furthermore, though this embodiment is described with the example that the cubic panorama image and the row images in a rectangular tunnel shape are merged, it is also possible that row images are merged into a cylindrical shape and then a panorama

image of a semispherical shape (see Isp in FIG. 8) is merged thereto. The shape of each row image and the shape of the panorama image may be changed as required, and they may be selected as desired with the use of the existing stitching program, not limited to the above embodiment.

According to still another embodiment of the present invention, the camera adopting the optical tube assembly may photograph an object in a tilted state. FIGs.

18a and 18b show an example that the optical tube assembly of the present invention photographs an object with being tilted at an angle Op of 45 degrees to the object.

Specifically, as shown in FIG. 18a, when photographing a first row source image IS1-T in a hallway, the camera is positioned. on the centerline Lo of the hallway and tilted so that a tilt angle Op is 45 degrees. At this time, the lenses 20'and 30'of the optical tube assembly are arranged so that an angle of view (0) is zero in the perspective direction, i. e. an advancing direction of the camera (or, the user) as mentioned above. Thus, an incident angle of the camera is 45 degrees to the width (W)-directional surface of the object. At this time, a collimated light is incident in the width W direction.

Accordingly, though the source images photographed by the camera which is advancing are merged, image distortion is not generated. The optical tube assembly has an a positive value of the angle of view (0) in a length L direction of the object, i. e. a direction perpendicular to the advancing direction. Such arrangement is advantageous to allow increasing the photographable width W of the object, beyond the limit of the optical tube assembly which is capable of photographing an image just in a range corresponding to the width of the objective lens 20'or the width of the incident opening of the cylindrical case.

Moreover, when photographing the first source image Isi-p corresponding to the right wall of the hallway, the camera and the optical tube assembly are rotated as shown in FIG. 18b so that the tilt angle Op to the centerline Lo is still kept at 45 degrees. At this time, an angle of view (0) to the perspective direction is also zero, similarly to the above case. FIG. 19 schematically shows an example that the camera photographs with being tilted at 45 degrees to the hallway.

In the same way, the first and seventh source images IS1-T, ISI-R, IS1-B and IS1-L to IS7-T, IS7-R, IS7-B and IS7-L are obtained. Each of the obtained row images is merged in the same way as shown in FIG. 11. Here, since the source images are all photographed by the collimated incident light since the angle of view (0) is zero to the perspective direction, i. e. a width direction, image distortion is not generated though the images are merged.

In this embodiment, the processes of photographing and merging the cubic panorama image Icu are identical to the former embodiment. However, when the cubic panorama image Icu is merged with the first row image Il, a border region for stitching is a conical surface Pco tilted at 45 degrees with a center position Oi as an apex since the camera is tilted at 45 degrees, as shown in FIG. 19. Thus, all sides A, B, C, D and E except a side F should be merged among the cubic panorama image Icu as shown in FIG. 14, and a border of merging is positioned between the sides B, C, D and E and the source images of each row as shown in FIG. 20. The panorama image and the source image of each row are merged in a way not limited to this embodiment, and it will be apparent to those skilled in the art that the image merging border may be suitably changed according to the tilt angle of the camera.

According to still another aspect of the invention, a photographic image for implementing a virtual reality space may be photographed by a reflective photographing apparatus, which is shown in FIG. 21 as an example.

Referring to FIG. 21, the reflective photographing apparatus of the present invention includes a support unit 50 and a photographing unit 60. The support unit 50 includes a plurality of legs 51 for supporting the apparatus and a base 52 on which the photographing unit 60 is positioned. Preferably, the leg 51 is configured so that its length is adjustable as desired. In addition, the photographing unit 60 is combined to the base 52 so that it is rotatable and its tilt angle is adjustable.

A concave reflective mirror 61 for condensing incident light is installed to the photographing unit 60, and a camera 62 is reciprocably installed on the centerline Lc of the concave reflective mirror 61. Specifically, the camera 62 is combined to the end of a support bar 65 slidably combined to a support 64 combined to a frame 63. The support bar 65 is slidable through a support hole formed in the support 64 for example, so the camera 62 installed at the end thereof is also reciprocatable to move toward or far from the concave reflective mirror 61. Preferably, a scale is marked on the support bar 65 so that a user may recognize a position of the camera 62. More preferably, there is additionally provided a locking unit for fixing the support bar 65 to the support 64.

According to the reflective photographing apparatus configured as mentioned above, an angle of view (0) to an object may be suitably adjusted by changing a distance between the concave reflective mirror 61 and the camera 62. This will be described in more detail with reference to FIGs. 22a to 22c.

FIG. 22a shows the cast that an angle of view (0) is zero. In FIG. 22a, the

distance Do'between the concave reflective mirror 61 and the camera position Pc is set so that only light in parallel with the concave reflective mirror 61 is incident on the camera from the object. This corresponds to the lens arrangement of the optical tube assembly shown in FIG. 4a.

If the reflective photographing apparatus is used, it is possible to photograph an image having a size corresponding to the diameter of the reflective mirror, so relatively broader photographic image is obtained rather than the case using the former optical tube assembly.

FIG. 22b shows the case that an angle of view (E)) is positive. In FIG. 22b, the distance Dl'between the concave reflective mirror 61 and the camera position Pc is set so that only light condensed to the concave reflective mirror 61 is incident on the camera from the object. At this time, the distance satisfies this relation of Dl'< Do'.

This corresponds to the lens arrangement of the optical tube assembly shown in FIG. 4b.

FIG. 22c shows the case that an angle of view (@) is negative. In FIG. 22c, the distance Dz'between the concave reflective mirror 61 and the camera position Pc is set so that only light diverged to the concave reflective mirror 61 is incident on the camera from the object. At this time, the distance satisfies this relation of D2'> Do'. This corresponds to the lens arrangement of the optical tube assembly shown in FIG. 4c.

INDUSTRIAL APPLICABILITY The optical tube assembly and the reflective photographing apparatus according to the present invention may adjust an angle of view (0) selectively as required to implement a panorama image, an object image and a 3-dimensional virtual reality space

since the angle of view (0) may be adjusted to a positive value, zero and a negative value.

When photographing and merging images with the use of a camera adopting the optical tube assembly or the reflective photographing apparatus according to the present invention, image distortion is never generated though a plurality of source images are merged with eliminating overlapped portions since only images corresponding to the light perpendicularly incident on the object from the camera are photographed.

In addition, the optical tube assembly of the present invention may be simply attached to a camera, and the images photographed by the camera may be merged as they are without any correction, so it makes the work very efficient and dose not require any complex program algorithm. Thus, when a user desires to implement photographic image based virtual reality space, the user may photographs photographic images and then easily implement the virtual reality space by using a well-known stitching program, according to the method of the present invention.

The present invention has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.