Patent Application
20130271803
The present invention relates to a system for forming a hologram, and more particularly to a system for forming an optical hologram.
In a conventional optical holographic technology, a portion of a coherent beam is used to irradiate to an object, and the reflected light from the object or the light transmitted through the object is incident to a holographic plate. This light is called as an object beam. Another portion of the coherent beam is projected onto the holographic plate to be used as a reference beam. Since the object beam and the reference beam are from the same coherent beam, the object beam and the reference beam are interfered with each other at the holographic plate to result in many bright and dark interference fringes. The interference pattern recorded on the holographic plate is formed as a hologram. The shape of the interference pattern indicates the phase relationship between the object beam and the reference beam. The bright/dark contrast level of the interference pattern indicates the intensity relationship between the object beam and the reference beam.
Conventionally, a disk-type multiplex holographic system uses a cylindrical lens to generate holograms. Due to the cylindrical lens, the hologram obtained at each shot is a long thin fan-shaped segment. Since the reconstructed image viewed by the observer is the combination of the images that are reconstructed from many small individual segments, the reconstructed image is usually suffered from distortion. Moreover, numerous vertical dark lines are superimposed on the reconstructed image, which is referred as a picket-fence effect.
Moreover, in comparison with the conventional disk-type multiplex holographic system, a conventional image-plane disk-type multiplex holographic system utilizes a simplified optical system because the cylindrical lens is omitted. By multiple exposures, the object image is imaged on a holographic film. However, due to the multiple exposures of the film, the brightness of the reconstructed image is possibly insufficient. Under this circumstance, the holographic image is not aesthetically pleasing, and it is difficult to produce a large-sized reconstructed image.
Therefore, there is a need of providing an approach to solve the problems resulted from the multiple exposures of the film.
The present invention provides a holographic image forming system for producing a reference beam carrying the image information of a target object, thereby reducing the interference fringes of the film, which are generated by the object beam and the reference beam. Consequently, the times of multiple exposures of the film are reduced, and the brightness of the reconstructed image is enhanced. In addition, the holographic image forming system can be employed to produce large-sized holograms.
The present invention further provides a holographic image forming system for producing a reference beam carrying the image information of a target object. In addition, a half-cylindrical lens is arranged in the optical path of the object beam and upstream of the film. The arrangement of the half-cylindrical lens is effective to reduce the undesired interference fringes of the film, which are generated by the object beam and the reference beam. Consequently, the times of multiple exposures of the film are reduced, and the brightness of the reconstructed image is enhanced. In addition, the holographic image forming system can be employed to produce large-sized holograms.
The present invention still provides a holographic image forming system for producing a reference beam carrying the image information of a target object. By slicing pixels from the image. In such way, the pixel values of two image frames of the target object are reduced and complementary to each other. The image slicing process is effective to reduce the undesired interference fringes of the film, which are generated by the object beam and the reference beam. Consequently, the times of multiple exposures of the film are reduced, and the brightness of the reconstructed image is enhanced. In addition, the holographic image forming system can be employed to produce large-sized holograms.
The present invention still provides a holographic image forming system for producing a reference beam carrying the image information of a target object, thereby reducing the exposure regions of the interference fringes of the film, which are generated by the object beam and the reference beam. Consequently, the times of multiple exposures of the film are reduced, and the brightness of the reconstructed image is enhanced. In addition, the holographic image forming system can be employed to produce large-sized holograms.
In accordance with an aspect of the present invention, there is provided a holographic image forming system. The holographic image forming system includes an illumination unit, a beam splitting unit, a reference beam processing unit, an image generating unit, an object beam processing unit, and a film. The illumination unit is used for providing a coherent beam. The beam splitting unit is used for splitting the coherent beam into a reference beam and an object beam. The reference beam processing unit includes an image generator for receiving the reference beam and outputting a reference light wave carrying an image information of a target object. The image generating unit is used for providing at least one image of the target object. The object beam processing unit is used for guiding the object beam to the image generating unit, thereby generating an object light wave. When the reference light wave and the object light wave are incident to the film, the reference light wave and the object light wave are interfered with each other to result in a plurality of interference fringes on the film.
In an embodiment, the illumination unit includes a gas laser beam generator, a carbon dioxide laser beam generator, a liquid laser beam generator, a solid laser beam generator, or a semiconductor laser beam generator.
In an embodiment, the coherent beam is a visible beam or an invisible beam.
In an embodiment, the beam splitting unit includes a beam splitter.
In an embodiment, the image generating unit includes an image-processing electronic device for performing a color separating operation on the image, thereby outputting a first monochromatic component image and a second monochromatic component image. A first monochromatic color of the first monochromatic component image is different from a second monochromatic color of the second monochromatic component image.
In an embodiment, the object beam processing unit includes an angle adjustable element for adjusting an included angle between the object light wave carrying the first monochromatic component image or the second monochromatic component image and the reference light wave. The reference light wave is incident to the film at a fixed reference beam angle, so that the included angle corresponding to the first monochromatic component image is different from the included angle corresponding to the second monochromatic component image.
In an embodiment, the object beam processing unit includes an object beam imaging system including a half-cylindrical lens. The object light wave is directed from the object beam imaging system to the film through the half-cylindrical lens. The film is located within a depth-of-field range and near a focal plane distance of the object beam imaging system, but the film is not located at the focal plane distance.
In an embodiment, the image generating unit further captures multiple image frames of the image of a target object with the preset number of capture pixels, and processes the multiple image frames with the preset number of projection pixels, then the processed multiple image frames are recorded on the film, wherein the pixel number of projection pixels is lower than the pixel number of capture pixels.
In an embodiment, an image information of the first image at the projection pixel is complementary to an image information of the second image at the projection pixel.
In an embodiment, the film has a planar shape, a disc-type shape, a cylindrical shape or a conical shape.
In an embodiment, the image includes multiple image frames of the target object, and the multiple image frames of the target object are captured from multiple viewpoints.
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
The present invention provides a holographic image forming system. The holographic image forming system may be employed to synthesize various holograms such as rainbow holograms, reflection holograms, multi-viewpoint holograms, true color holograms or integral holograms according to different imaging principles. The present invention will be illustrated by referring to a holographic image forming system for synthesizing a specified hologram. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for the purpose of illustration and description only.
In this context, the term “reference beam angle” denotes an included angle between a reference beam and a normal line of the film. In a case that the film is planar, the film has a single normal line. Whereas, in a case that the film is rolled as a cylindrical shape or a conical shape, the film has multiple normal lines. The definition of the reference beam angle may be varied according to the practical requirements. For example, the term “reference beam angle” may denote an included angle between the reference beam and a tangent plane of the film. In the following embodiments, the reference beam angle is a fixed angle.
The illumination unit 10 is used for providing a coherent beam 101. For example, the illumination unit 10 may be any kind of laser beam generator for emitting a coherent laser beam 101. Dependent on the medium of the laser beam generator, the laser beam generator includes for example a gas laser beam generator (e.g. a helium-neon laser beam generator), a carbon dioxide laser beam generator, a liquid laser beam generator, a solid laser beam generator, or a semiconductor laser beam generator. Depending on the wavelength of the laser beam, the laser beam may be a visible laser beam or an invisible laser beam.
After the coherent beam 101 from the illumination unit 10 is received by the beam splitting unit 12, the coherent beam 101 is split into a reference beam 121 and an object beam 123. The beam splitting unit 12 may comprise a beam splitter (BS) 122. Moreover, the beam splitting unit 12 may further comprise a plurality of optical elements. For example, a reflective mirror 124 is located at a proper position to guide the coherent beam 101. In other words, the beam splitting unit 12 is used for splitting the coherent beam 101 into the reference beam 121 and the object beam 123.
The reference beam 121 from the beam splitting unit 12 is received by the reference beam processing unit 14. Moreover, according to the reference beam 121, the reference beam processing unit 14 outputs a reference light wave 141. In an embodiment, the reference beam processing unit 14 comprises a spatial filter (SF) 142 for eliminating the adverse influence of the spatial noise on the reference beam 121. For example, the spatial filter 142 is composed of a confocal convex lens set and a pin hole. The composition of the spatial filter 142 is not limited to the combination of the confocal convex lens set and the pin hole.
Moreover, the reference beam processing unit 14 further comprises an image generator 148. After the reference beam 121 is guided to the image generator 148 through the optical elements 146′ and then passes through the lens set 144, the generated reference light wave 141 will carry the image information of the target object. In such way, the percentage of the reference light wave 141 that is outside the target image to be incident to the film 20 will be reduced. Under this circumstance, the undesired interference fringes and the times of multiple exposures are both reduced.
Moreover, the reference beam processing unit 14 may comprise other optical elements for guiding or optimizing the reference beam 121 in order to output the reference light wave 141. For example, a lens set 144 with different focal lengths of lens, or the like. The reference beam processing unit 14 may further comprise a light-adjustable part such as an amplitude adjustable part, a phase adjustable part or an angle adjustable part. After the reference beam 121 is processed by the reference beam processing unit 14, the reference light wave 141 is outputted from the reference beam processing unit 14. By adjusting an incident angle of the reference light wave 141 with respect to the film 20, the reference light wave 141 will be incident to the film 20 at a reference beam angle.
The image generating unit 16 is used for providing at least one image. In this context, the term “image” denotes an image of a target object 162 captured from a single viewpoint or multiple images frames of the target object 162 captured from multiple viewpoints. Moreover, the target object 162 may be monochromatic or polychromatic, or the target object 162 may have gray levels. In an embodiment, the image generating unit 16 comprises an image pickup device 164, an image-processing electronic device 166, and a display device 168. For example, the image pickup device 164 is a CCD camera for capturing the image of the target object 162 from one viewpoint or capturing multiple images frames of the target object 162 from multiple viewpoints. Moreover, the position of the image pickup device 164 or the target object 162 is adjustable, so that the image of the target object 162 may be captured by the image pickup device 164 from a desired viewpoint. For example, the image-processing electronic device 166 is a computer for receiving the image 161 from the image pickup device 164 and processing the image 161.
Moreover, since the reference beam processing unit 14 has the image generator 148 for generating the reference light wave 141 carrying the image information of the target object, the image 161 captured by the image pickup device 164 is also transmitted to the image generator 148. Alternatively, after the image 161 is processed by the image-processing electronic device 166, the processed image is transmitted to the image generator 148 of the reference beam processing unit 14.
Moreover, for example, the display device 168 is a LCD screen for displaying the processed image 163 of the image-processing electronic device 166.
Moreover, by the object beam processing unit 18, the object beam 123 from the beam splitting unit 12 is guided to the image generating unit 16, thereby generating an object light wave 181. In this embodiment, the object beam processing unit 18 comprises several optical elements. The optical elements may include but are not limited to a lens set 182, a reflective mirror 184, or the like. By these optical elements, the object beam 123 is guided to the display device 168 of the image generating unit 16, thereby imaging the object beam 123 as the object light wave 181 and outputting the object light wave 181.
Furthermore, the reference light wave 141 and the object light wave 181 are incident to the film 20 to result in a plurality of interference fringes on the film 20. Since the reference light wave 141 carrying the image information of the target object is effective to reduce the times of multiple exposures of the film, the brightness of the reconstructed image is enhanced.
In the first, second or the following embodiment, the image-processing electronic device 166 of the image processing operation performed by the image generating unit 16 will be illustrated in more details as follows.
In practice, after the image slicing process is performed, the reconstructed image is not obviously inconsistent. On the other hand, since the pixel number of each image frame is reduced, the times of multiple exposures of the film in the subsequent processes may be reduced. Consequently, the hologram of the present invention can provide the effects that many of the conventional holograms fail to present because of excessive exposure times, or the hologram of the present invention can solve the drawbacks of the conventional hologram from small size and insufficient brightness.
It is noted that the arrangement of the half-cylindrical lens 186 or the use of the image slicing process is effective to reduce the times of multiple exposures of the film. As for the single-frame image or the image with less number of image frames, either the arrangement of the half-cylindrical lens 186 or the use of the image slicing process is feasible. As for the image with multiple image frames, the arrangement of the half-cylindrical lens and the use of the image slicing process are simultaneously applied to the holographic image forming system. Consequently, a bright and clear reconstructed image can be obtained.
Since the use of the image slicing process and the arrangement of the half-cylindrical lens can reduce the times of multiple exposures of the film, the applications of the holographic image forming system can be expanded. For example, the image can be recorded on specified positions of the film 20. For example, if the film 20 is a disc-type film, the image may be recorded on specified radius positions of the disc-type film. Moreover, since the images of different target objects may be recorded on different radius positions, an image in a racetrack arrangement may be generated. After the image is reconstructed, the target images recorded on different tracks may be observed. Consequently, the reconstructed image is more diverse.
For example, since multiple exposures of the film result in deteriorated diffraction efficiency, the conventional holographic image forming system may only produce small-sized holograms of the target object. However, since the image slicing process is adopted by the holographic image forming system of the present invention, the times of multiple exposures of the film will be reduced, or even a multi-channel image of the target object can be produced, or a multi-viewpoint image can be produced to result in the dynamic effect. As for the image reconstructing efficacy, the observer can view the reconstructed image from the 15-degree viewpoint to the 45-degree viewpoint, or different observers in front of the film can view different reconstructed images.
For the colorful target object 162, the object beam processing unit 18′ further comprises an angle adjustable element 188. For example, the angle adjustable element 188 comprises one or more reflective mirrors or them equipped with driving module (not shown), and the incident angle of the object light wave 181 with respect to the film 20 is adjusted by the angle adjustable element 188. For example, if the first monochromatic component image is a red component image and the second monochromatic component image is a green component image, the incident angle of the object light wave 181 with respect to the film 20 may be adjusted by the angle adjustable element 188. Consequently, there is a first included angle between the object light wave 181 corresponding to the red component image and the reference light wave 141, and there is a second included angle between the object light wave 181 corresponding to the green component image and the reference light wave 141. Similarly, if the third monochromatic component image is a blue component image, there is a third included angle between the object light wave 181 corresponding to the blue component image and the reference light wave 141. Since the incident angle of the reference light wave 141 with respect to the film 20 is unchanged, only the incident angles of the object light wave 181 corresponding to different color component images are adjusted. Moreover, the exposure regions of the film 20 corresponding to the three color component images may be identical, partially superimposed or non-superimposed.
As known, it is difficult to adjust the optical system of the holographic image forming system. Once an optical element is adjusted after the optical system is established, the process of reconstructing the optical path is very time-consuming. For solving this drawback, before the object light wave is incident to the film, the holographic image forming system of the present invention utilizes the angle adjustable element 188 to adjust the incident angle of the object beam. This adjusting way has many benefits. For example, the imaging optical system may be kept unchanged in order to reduce the time of reconstructing the optical path. Moreover, as mentioned above, by adjusting the included angle between the individual monochromatic component image and the reference light wave that has the fixed incident angle, the object light wave and the reference light wave are incident to the film to result in interference fringes. When the image is reconstructed from the film, since the reference beam source is fixed, the reconstructed image shows the color effect.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 101113348 | Apr 2012 | TW | national |
