BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates, in general, to a photographic printer for producing three-dimensional (3D) photographs on the lenticular print material. In particular, the present invention relates to a 3D photograph printing apparatus and method in which the lamination of lenticular print material is optional.

2. Prior Art

In lenticular 3D photography, the basic process involves taking a plurality of two-dimensional (2D) views from a number of horizontally spaced vantage points, and compressing these 2D views onto the photographic emulsion layer of the lenticules of a lenticular screen to form a 3D composite image of the scene. It is understood that the aforementioned lenticular screen is a sheet of transparent material with the front side embossed with an array of cylindrical lenses and the back side coated with a photographic emulsion or the lenticular screen is attached to a sheet of photographic film or paper. The precoated lenticular screen, will be hereafter referred to as the "print material." The composite image formed on the photographic emulsion of the print material is a lineoform image. The line spacing appearing on this lineoform image is identical to the spacing between lenticules on the lenticular screen.

In some 3D printing methods, a lamination procedure is required with the photographic film or paper being attached or bonded to a lenticular sheet after it has been exposed with compressed 2D images and chemically processed. In other 3D printing methods, however, lamination is optional. In particular, when the lenticular material is pre-coated with a photographic emulsion, lamination is avoided in the making of a 3D photograph.

Various techniques for compressing a plurality of 2D views onto the emulsion layers of lenticules of a lenticular screen have been disclosed in the past. Some of

these techniques require a lamination procedure. For example, U.S. Patent No.3,895,867 (Lo et al), issued July 22, 1975, discloses a technique for recording images on the emulsion layer underlying the lenticules. This particular technique involves repeatedly turning off the light on the projector and intermittently shifting the lenticular screen or the photographic film or paper during the printing process. After the exposure of multiple images is completed, the photographic film or paper is chemically processed and then bonded to a viewing lenticular screen to become a 3D photograph.

It is quite common that the dimension of the photographic paper changes after the chemical process which involves many soaking, rinsing and drying steps. As a result, the spacing on the line form image may not match the spacing between the lenticules on the lenticular screen that is used in exposure. In order to circumvent this spacing mismatch problem, one can use a "viewing" lenticular screen, instead of the lenticular screen originally used in exposure, for lamination. Unfortunately, the dimensional changes of the photographic film or paper may not be uniform throughout the print, nor are they predictable. Any mismatch between the line form image and the superimposed lenticular screen will result in a poor quality 3D print. Furthermore, lamination is very time-consuming, because the lineform image on the print material must be precisely aligned with the lenticules. Consequently, any printing process that requires lamination is not suitable for the mass production of 3D photographs.

In a 3D photographic printing method that does not require lamination, the print material of the lenticular screen is usually pre-coated with a photographic emulsion. After the exposure of multiple images is completed, the pre-coated lenticular screen is chemically processed and becomes a 3D photograph. Even if the dimension of the print material changes in the chemical process, the lineform image is still in perfect registration with the lenticules. To compose a 3D photograph on a pre- coated lenticular screen, one projects a plurality of 2D images, through one or more projection lenses, onto the lenticular print material at different angles. U.S Patent No.4,120,562 (Lo et al), issued on October 17, 1978, discloses a scanning method

which uses an apparatus for changing the projection angle by a predetermined amount during exposure. U.S. Patent No.5,028,950 (Fritsch), issued on July 2, 1991, discloses a dual-stage printer in which a single projection lens scans each 2D image on the negative to project the 2D images onto the print material. U.S. Patent No.5,111,236 (Lo), issued on March 27, 1990, discloses a method for simultaneously printing a number of 3D photographs by using a single projection lens with a large field of coverage. For example, if a set of three 2D views is used to compose a 3D photograph, then all three different 2D images are projected through a projection lens to simultaneously expose three different prints at three different projection angles. With this arrangement, each print must be exposed three times at different projection angles in order that the emulsion layer underlying the lenticules be filled with compressed 2D images. In this case, the aperture of the projection lens must be large enough to fill one third of the width of the lenticule, and the print material must be shifted to different locations to be exposed at different angles. U.S. Patent No. 4,852,972 (Lo), issued on June 8, 1987, discloses a method of controlling the variation of density across a lenticule in the printing of 3D photographs. The following patents also disclose early 3D printing techniques involving the projection of 2D images at different projection angles:

U.S. Patent No.4,059,354 (Lo et al), issued on November 22, 1974 U.S. Patent No.4, 101,210 (Lo et al), issued on July 18, 1978

U.S. Patent No.4, 132,468 (Lo et al), issued on June 2, 1979 In the printing methods disclosed in the patents in the above list, whenever a single projection lens is used, a scanning mechanism is required to move the projection lens, the source image (the negative, in this case) or the print material in order to change the projection angle. Even when a plurality of projection lenses or projectors is used, a scanning mechanism is usually required so that the photographic emulsion layer underlying each lenticule is filled with compressed images without having gaps between them. In all those printing methods that require scanning, at least two of the following three elements must be moved by mechanical means to cover the required projection angles: (a) the source image, (b) the projection lens, (c)

the print material. In order to produce an in-focus 3D photograph, the mechanical movement must be free of vibration and meandering. More importantly, the moving elements must travel at different speeds but in perfect synchronization. These requirements demand a mechanical design with high levels of sophistication. SUMMARY OF THE INVENTION

It is an object of this invention to develop a printer and method to improve the accuracy of 3D printing. The 3D photographic printing method and apparatus, according to the present invention, does not require the movement of either the projection lens or the print material. In certain arrangements, the source image can also remain stationary during the entire printing process. This greatly simplifies the mechanical design of the printer and increases the accuracy of printing.

Briefly, the 3D photographic printer, according to the present invention, uses a single, large-aperture projection lens to cover all of the projection angles necessary for filling the area underlying each lenticule with compressed 2D images. The aperture that is necessary for filling the entire area underlying each lenticule will be hereafter referred to as the "full aperture." By using a projection lens with a full aperture, the projection lens itself and the print material can be kept stationary during the entire printing process. In order that a single lens can be used to project a plurality of 2D images at different projection angles, a lens aperture plate is partitioned into a number of aperture sections corresponding to the number of images being projected. For example, if a set of N 2D images is used to compose a 3D photograph, then the lens aperture plate is partitioned into N aperture sections. During printing, only one of the N aperture sections is opened so that only one 2D image is projected at a time onto the print material at a particular angle. In the preferred embodiment of the printer, according to the present invention, a plurality of 2D images is displayed, one at a time, on a monitor screen. The position of the monitor screen is also fixed in relation to the projection lens and the print material during the entire printing process. Thus, the source image (the image displayed on the monitor screen), the projection lens and the print material are all at fixed locations during the printing process.

The 2D views which are used for composing a 3D photograph can be pre¬ recorded on photographic film or stored in an electronic medium. The 2D views can also be real-time images taken with one or more electronic cameras at the time of printing. The partitioned lens aperture plate can be controlled by mechanical means so that only one of the aperture sections is opened during the exposure of one 2D image. The partitioned lens aperture can also be a light valve, such as a liquid crystal device, which can be opened or closed in each aperture section by electro-optic means.

Alternatively, in place of the partitioned aperture plate, an opaque aperture plate with a single opening equal to the width of 1/N of the full aperture can be used. In order to cover all of the different projection angles, the plate is shifted to a different position to expose a different 2D view. It should be noted that the shifting of the aperture plate is carried out between the exposure of different 2D images but not during the exposure of a 2D image. Thus, the printing is intermittent. One variation of the printing method, discussed in the preceding paragraph, is to use an opaque plate with a narrow scanning slit, the dimension of which is much smaller than 1/N of the full aperture. In order to cover all the different angles of the full aperture in a single position, the scanning slit is moved across a distance equal to the full aperture in a continuous scanning motion. With this arrangement, each of the 2D views must be changed with proper timing so that the display on the monitor screen suffers no or insignificant disruptions during the exposure of all 2D views.

With a scanning slit, a real object can also be used as the source image, replacing the image displayed on the monitor screen. With this variation, neither an electronic camera nor an image displaying device is necessary. In order to change the 2D views, the object must be rotated intermittently or continuously during the printing process. It is understood that a real object can also be used as the source image in conjunction with a partitioned aperture or an aperture with a single 1/N opening. However, the object must be rotated intermittently to yield proper viewing angles.

With any of these arrangements, the projection lens and the print material can remain stationary during the entire printing process. Furthermore, when 2D images

are pre-recorded on an electronic medium and, at the time of printing, these 2D images are displayed on a monitor screen or projected on a projection screen, the source image can also be stationary. The 3D printing method and apparatus, according to the present invention, are preferably to be used to produce 3D photographs on pre-coated lenticular print materials. However, the disclosed method and apparatus can also be used when a lenticular screen is attached to the photographic print material.

The 3D printer, according to the present invention, can be an integrated printer which has a built-in chemical processing unit, or a separate printer wherein the exposed print material must be transferred out to a chemical processing unit.

As with other 3D printers, the disclosed method can be used to produce time- lapsed images or images of animated objects. On lenticular composite photographs, the images of a changing scene can be presented through different viewing angles. For example, a composite photograph can show the different blooming stages of a flower.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic presentation showing the top perspective of a printer wherein 2D images are displayed, one at a time, on a monitor screen and exposed through a large-aperture projection lens onto lenticular print material. FIG. 2 is a schematic presentation of the same printer wherein the lens aperture plate is partitioned into a number of aperture sections.

FIG. 3 is a schematic presentation showing a portion of a side view of the printer wherein the lens aperture plate is an opaque plate with a single opening equal to 1/N of the full aperture. FIG. 4 is a schematic presentation showing a portion of a side view of the printer wherein the lens aperture plate has a narrow slit.

FIG. 5 is a schematic presentation showing the relation between the full aperture and the width of a lenticule where all of the aperture sections of the aperture plate are open.

FIG. 6 to FIG. 8 are schematic presentations showing the relation between the width of the compressed image under each lenticule and the width of an open aperture section of a partitioned aperture plate.

FIG. 9 to FIG. 11 are schematic presentations showing the projected 2D images exposed through different aperture sections of a partitioned aperture plate.

FIG. 12 is a schematic presentation showing an electronic medium being used to store 2D images and to display a 2D image on a monitor screen.

FIG. 13 and FIG. 14 are schematic presentations showing an electronic camera being used to capture the 2D views of an object at different angles. FIG. 15 is a schematic presentation showing a bank of electronic cameras being used to capture the 2D views of an object at different viewing angles.

FIG. 16 is a schematic presentation showing an electronic camera being used to capture the 2D views of an object through the reflection of a plane mirror.

FIG. 17 is a schematic presentation showing an electronic camera being used to capture the 2D views recorded on film.

FIG. 18 is a schematic presentation showing a bank of electronic cameras being used to capture the 2D views recorded on film.

FIG. 19 is a schematic presentation showing a split screen being used to display four 2D images for simultaneously composing four 3D photographs. FIG. 20 is a schematic presentation showing a narrow aperture slit being scanned continuously across the lens aperture to change the projection angle while the object is rotated in synchronization so that the image of the object at different viewing angles is directly projected onto the print material.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic presentation showing the top view of the preferred embodiment of the 3D printer, according to the present invention. As shown, numeral 5 denotes an image storing device which stores 2D images to be used for composing 3D photographs. Numeral 45 denotes an image displaying means, such as a video monitor, for displaying a 2D image 30 for exposure. The displayed 2D image 30 represents one of N 2D views of the same scene taken at different viewing angles.

The displayed 2D image can be photographed image, computer generated graphics, medical image or any images suitable for composing a 3D print. Numeral 75 denotes a shutter for controlling the exposure time during printing. The shutter can be iris type, or linear type operated in either a vertical or horizontal direction. Numerals 55 and 56 denote two parts of a large-aperture projection lens. Either part of the projection lens may be a multi-element lens. Numeral 60 denotes a lens aperture plate which is partitioned into a number of aperture sections, each of which is independently controlled by a mechanical means so that only one section is opened during the exposure of a 2D image. The lens aperture 60 can also be a light valve such as a liquid crystal device which can be shut or opened in separate aperture sections by electro-optic means. The light valve can be opened and shut in the same sequence as the mechanical aperture sections in a lens aperture plate. Depending on the lens design, the aperture plate 60 may be placed behind or in front of the projection lens. Numeral 80 denotes lenticular print material. The print material can be a single sheet or a section of a roll, and it is preferably pre-coated with a photographic emulsion so that lamination can be avoided. Numeral 90 denotes a projected 2D image on the print material.

FIG. 2 is a schematic presentation of the printer. In order to explain the printing method, we use a set of three 2D views for composing a 3D photograph, or N=3. It is understood that N can be as small as two and as large as tens of thousands when the 2D images are acquired at the video rate. As shown in FIG. 2, the lens aperture plate 60 is partitioned into three aperture sections, denoted by 61, 62 and 63. The height of these aperture sections can be adjusted for sharpness control. Only one of the aperture sections is opened during the exposure of the respective 2D image at a particular projection angle. It is understood that the lens aperture plate can be partitioned into either equal aperture sections or unequal sections. Even when N is a small number, it is advantageous to have the lens aperture plate partitioned into N aperture sections. The number of partitioned aperture sections may or may not be equal to the number of 2D views to be used to compose a 3D photograph. Thus, the

full lens aperture plate can be partitioned into any number of aperture sections, ranging from two to fifty for a practical application.

FIG. 3 is a schematic presentation of the printer wherein a lens aperture plate 65 has only one lens aperture 66 instead of lens aperture plate 60 with multiple apertures 61, 62 and 63 as shown in FIG. 2. The width of the opening 66 is equal to 1/N of the full aperture. In order to cover three different projection angles for exposing three 2D views, the aperture plate 65 must be shifted to different locations so that the aperture 66 is, in effect, replacing each of the aperture sections 61, 62 and 63 as shown in FIG. 2. FIG. 4 is a schematic presentation of the printer wherein a lens aperture plate

67 with one narrow aperture, or slit, 68 is used. The slit width is smaller than 1/N of the full aperture. However, when N is a large number, the slit width can be equal or even larger than 1/N of the full aperture. In order to cover all the projection angles for exposing N 2D views, the slit 68 must be shifted across the full aperture, preferably in a continuous scanning motion. With this arrangement, it is imperative that the display on the monitor screen suffers no or insignificant disruption when one 2D view is changed to another. It should be noted that a narrower slit requires a longer exposure time which may limit how narrow the width of the slit can be. The practical slit width is determined by the optical characteristics of the lenticules and the viewing distance, among other factors. With a continuously scanning slit, a shutter 75 may not be necessary when the lens aperture plate is used for continuous scanning.

FIG. 5 shows the total width of all the aperture sections 61, 62 and 63 in relation to the width of a lenticule on the print material 80. When the print material is located at the image plane of the projection lens, the total projection angle 70 through all aperture sections must cover the entire width 89 of the lenticule. The total projection angle 70 is determined by the total width of aperture sections 61, 62 and 63 and the focusing properties of the projection lens. As shown, the aperture plate 60 is partitioned into three aperture sections 61, 62 and 63 for exposing three 2D images onto the print material 80.

FIG. 6 shows the compressed image 81 underlying each lenticule when the first 2D image 31 is exposed through the projection lens and the opened aperture section 61 of the lens aperture plate 60, onto the print material 80. As shown, the projection angle is denoted by numeral 71. FIG. 7 shows the compressed image 82 underlying each lenticule when the second 2D image 32 is exposed through the projection lens and the opened aperture section 62 of the lens aperture plate 60, onto the print material 80. As shown, the projection angle is denoted by numeral 72.

FIG. 8 shows the compressed 2D image 83 underlying each lenticule when the third 2D image 33 is exposed through the projection lens and the opened aperture section 63 of the lens aperture plate 60, onto the print material 80. As shown, the projection angle is denoted by numeral 73.

FIG. 9 shows the projected 2D image 91 on the print material 80 when the first 2D image 31 is exposed through the projection lens and the opened aperture section 61 of the lens aperture plate 60.

FIG. 10 shows the projected 2D image 92 on the print material 80 when the second 2D image 32 is exposed through the projection lens and the opened aperture section 62 of the lens aperture plate 60.

FIG. 11 shows the projected 2D image 93 on the print material when the third 2D image 33 is exposed through the projection lens and the opened aperture section 63 of the lens aperture plate 60.

It should be noted that the displayed 2D images 31, 32 and 33 in Figs. 9, 10 and 11 are mirror images so that the projected images 91, 92 and 93 on the print material are normal and not reversed. The displayed images can be reversed to become mirror images, either electronically or optically. If necessary, the images are reversed in intensity and color to become complementary negative images before they are displayed for exposure. Also, the 2D images 31, 32 and 33 must be arranged in a proper order so that the compressed images 81, 82 and 83 yield the correct left and right parallax, and the resulting 3D composite image is normal and not pseudoscopic.

FIG. 12 shows that the 2D images to be used for composing 3D photographs can be stored in an electronic medium such as a hard-disk in a computer 6, a computer diskette 7, or a CD-ROM 8.

FIG. 13 shows an electronic camera 10, such as a video camera, being used for acquiring three 2D views of an object 100 from three different viewing angles. As shown, while the camera 10 is kept stationary, the object 100 is rotated intermittently to yield 2D images as viewed from different angles. Alternatively, the object can be rotated continuously with the 2D images being acquired intermittently. However, when a narrow slit 68 is used to control the projection angle, as shown in FIG. 4, the 2D images can be acquired intermittently or continuously. The 2D images can be displayed in real-times or recorded for later use.

FIG. 14 shows an electronic camera 10 being used to acquire different 2D views of a stationary object 100 from different viewing angles. As shown, the camera 10 moves in relation to the object to three different locations, preferably along a circular track. The track's center of curvature coincides with a certain point (known as the key subject in 3D photography) of the object 100. With such an arrangement, the key subjects in the projected images on the print material will be in good registration with each other. If the camera is moved along a different track, such as a straight track, then for proper key subject alignment, the acquired 2D images must be properly shifted before they are displayed on the monitor 45 screen.

FIG. 15 shows a bank of three electronic cameras 11, 12 and 13 being used to acquire three 2D views of an object 100 from three viewing angles. The acquired 2D images can be stored in an image storing device for later use or they can be immediately displayed, one at a time, on the monitor for composing a 3D photograph. To achieve a good key subject registration on the 3D photograph, the relative position of the cameras must be properly adjusted.

In FIG. 13 to FIG. 15, the 2D images acquired by the electronic camera must be electronically reversed to become mirror images as they are displayed on the monitor 45 for exposure. Alternatively, the 2D images can be reversed optically as shown in FIG. 16.

FIG. 16 shows an electronic camera 10 being used to acquire the 2D images of an object 100 through the reflection of a plane mirror 77. The mirror 77 is preferably a front-coated, or first-surface mirror.

FIG. 17 shows a set of three 2D images 21, 22 and 23 recorded on a film strip 20 being sequentially captured by an electronic camera 10 so that the 2D images can be displayed, one at a time, on the monitor 45 screen for printing. As with the image acquisition method described with reference to FIG. 14, the position of the camera in relation to the 2D views on the film strip 20 must be pre-calibrated for proper key subject alignment. FIG. 18 shows a set of three 2D images 21, 22 and 23 recorded on a film strip

20 being captured by a bank of three video cameras 11, 12 and 13 so that the 2D images can be displayed, one at a time, on the monitor 45 screen for printing. As with the image acquisition method described with reference to FIG. 15, the position of the cameras in relation to the 2D views on the film strip 20 must be pre-calibrated. FIG. 19 shows four 2D images, 130, 230, 330 and 430, being displayed on a split screen so that four 3D photographs can be composed simultaneously. As with the single 2D image 30 shown in FIG. 1, each of the four 2D images 130, 230, 330 and 430 represents one of the N 2D views taken from different viewing angles. The four 2D images 130, 230, 330 and 430 can be the same or different. It is understood that the number of 2D images simultaneously displayed on a split screen can be any number ranging from 2 to 100 for a practical application.

FIG. 20 is a schematic presentation showing an object 100 being used as the source image. The object is rotated continuously, in synchronization with the scanning motion of the aperture slit 68. However, a plane first-surface mirror 77 must be used to optically achieve image reversal. As shown in FIG. 20, the mirror 77 is placed between the object and the projection lens at an appropriate angle. It is understood that the mirror 77 can also be placed between the projection lens and the print material 80.

While the present invention has been described with reference to the preferred embodiment, it shall be understood by those skilled in the art that various changes

may be made and components may be substituted without departing from the scope of the invention. For example, the image displaying device 45 shown in FIG. 1 can be an image projection system where an image is displayed on a projection screen. Also, the shutter 75 shown in FIG. 1 to FIG. 4 can be a movable plate which is flipped away from the light path during exposure. Furthermore, the lens aperture plate 60 itself can also be used as a shutter while maintaining the aperture partitioning functions. Moreover, the displayed image can be electronically dimmed out to become a black screen so that the shutter 75 is not necessary.

While the 3D printing method and apparatus, according to the present invention, have been described with reference to the use of three 2D images for composing a 3D photograph, it is the intention of the present invention that the number of 2D images used for composing a 3D photograph can be as small as two and as large as tens of thousands when the 2D images are acquired at the video rate.

THE METHOD OF OPERATION OF THE PRINTER

The method of operation presented in this section is described in accordance with a printer which uses:

1. A monitor screen for displaying a plurality of 2D images, one at a time, 2. A set of three 2D images for composing a 3D photograph,

3. A large-aperture projection lens,

4. An aperture plate which is an opaque plate with a single opening with a width equal to one third of the full aperture and is placed between two parts of the projection lens, 5. A shutter for controlling the exposure time in accordance with the image brightness and the optical characteristics of the print material, 6. A lenticular-type print material.

The arrangement of the printer components is similar to the schematic presentation in Figure 1 and Figure 3.

Before the printing process starts, the shutter is closed and the aperture plate is located in the first printing position which can be the rightmost position as depicted in Figure 3.

After the first 2D image is displayed on the monitor screen, the shutter is opened to expose the displayed image through the projection lens onto the print material. After an appropriate duration, the shutter is closed.

The second 2D image is then displayed on the monitor screen and the aperture plate is moved to the second position which is the center position. The shutter is again opened to expose the displayed image through the projection lens onto the print material. After an appropriate duration, the shutter is closed.

The third 2D image is then displayed on the monitor screen and the aperture plate is moved to the third position which is the leftmost position in this arrangement. The shutter is again opened to expose the displayed image through the projection lens onto the print material. After an appropriate duration, the shutter is closed. The print material is now exposed with all three 2D images at proper angles.

It is brought to a chemical processing unit to complete the photographic processing steps.

The above description sets forth the best mode of the invention as known to the inventor at this time, and the above Examples are for illustrative purposes only, as it is obvious that one skilled in the art may make modifications to this process without departing from the spirit and scope of the invention and its equivalents as set forth in the appended claims.