admin_jsfisher wrote: ↑Sun Mar 28, 2021 9:08 pm
No, no, no, no. I need to hear more about this holoprinter you have DIyed.
Sure, what would you like to know in particular?
It is basically the same technique as developped by Yamaguchi in 1990, then refined by ZEBRA in the late 90s.
As seen in the video in my previous post, a 3D rendering software generates views (tens of thousands) which are sequentially displayed on a Spatial Light Modulator, then imaged/printed onto the film via some optics, as hogels, ie. small elementary holograms;
Allow me to quote Hans Bjelkhagen below who nicely retraced the history of this technology on the FB page:
Here is the history with references icluding patents which led to the ZEBRA and GEOLA printers:
As early as 1967, R.V.Pole [1] was able to create a crude reflection hologram based on multiple photographs. The process was intrinsically 2-step: first a two dimensional matrix of small lenslets was used to image photographs of an object taken from many different horizontal and vertical perspectives. The second step was an optical transfer of the lenslet matrix to a reflection hologram. Pole reported that the resulting "holographic stereograms" exhibited full three-dimensionality, exactly like ordinary holograms, but that the large inactive area between the lenslets caused image degradation akin to viewing an ordinary hologram through a coarse grid structure.
In 1969, DiBitetto [2] reported an alternative system in which a masked holographic plate was sequentially exposed to different perspective-view images. This solved the resolution problem inherent to Pole's work. Subsequent work by King et al [3] reported the production of a white light-viewable image-plane hologram (an H2) from a DeBitetto type (H1) master.
During the 1970's Lloyd Cross [4] and others, inspired by the invention of the rainbow hologram [5], tackled the problem of generating holographic stereograms in yet another way. Here transmission holography was used to produce bright rainbow holograms (without vertical parallax) using large cylindrical lenses for recording and cylindrical films for display. However this type of system, although popular for a time, proved ultimately to be rather inferior to the DeBitetto/King approach.
By the early 90's most large stereograms had therefore started to be recorded as reflection holograms using the DeBitetto/King model. In 1991 Walter Spierings and his company, the Dutch Holographic Company B.V. introduced the first full-colour reflection stereograms [6]. Although impressive these holograms were still derived from analogue photographic data. The transition to digital data started at MIT with the 1991 publication by Halle, Benton and others described the Ultragram [7]. This was the first use of digital image distortion techniques and provided a clear reason for going "fully digital". The advent of digital cameras and cheap spatial light modulators in recent years has only reinforced this doctrine. The original DeBitetto/King model is still used successfully today to produce full-colour horizontal parallax reflective holographic stereograms from digital camera or computer data.
With the advent of digital spatial light modulators a different avenue became available to create a high resolution reflection hologram from computer or camera data. This was 1-step or Direct-Write Digital Holography (DWDH). In this case one computes and print only a small element of a hologram at a time. In other words we consider the required hologram as being composed of a plurality of small micro-holograms arranged in the form of an (x,y) grid. With the advent of liquid crystal displays a far simpler solution became possible: a reference and object beam could be made to intersect at the surface of a photo-sensitive material to directly create the micro-hologram. The object beam is encoded with image data by being made to pass through a spatial light modulator such as a liquid crystal display (LCD) and a lens system. A step and repeat mechanism then writes a plurality of juxtaposed micro-holograms (these became to be known as holographic pixels or hogels [8]).
By using three of more laser wavelengths full-colour reflective hogels can be written at the same physical location. Since the hogel is inevitably chosen to be small (usually in the range of 0.1mm diameter to several mm) only small lasers are potentially required.
In 1988 Yamagushi, Ohyama and Honda became the first group to report experimental demonstration of DWDH [9]. In their one-colour system, a two-dimensional perspective sequence was generated to form an array of hogel mask frames which were recorded on video tape and downloaded one-by-one to a twisted nematic LCD. A laser beam was used to illuminate the LCD and a lens system employed to record a volume reflection hologram of the Fourier Transform of each mask. Each such hologram constituted a hogel and by sequentially advancing the holographic plate between exposures a matrix of abutting hogels was created. The resulting hologram reconstructed an accurate full parallax view of the original scene. The process appeared promising, but the 320-by-240 hogel array required many hours for recording.
The ZEBRA and GEOLA printers:
Klug et al [10], working at the US Company Zebra Imaging, extended the technique of Yamagushi et al. in the late 1990s to large-format full-colour reflection holography. Zebra proved beyond doubt that the DWDH technique was capable of generating large format digital colour holograms of a quality never before imagined. Brotherton-Ratcliffe et al in 1999 [11-14], working at the Lithuanian Company Geola, subsequently demonstrated that the technique could be made to work much faster and more reliably using pulsed RGB lasers.
REFERENCES:
[1] R. V. Pole, “3-D imagery and holograms of objects illuminated in white light,” Appl. Phys. Lett. 10, 1, 20-22 (1967).
[2] D. J. DeBitetto, “Holographic panoramic stereograms synthesized from white light recordings,” Appl. Opt. 8, 1740-1741 (1969).
[3] M. King, A. Noll and D. Berry, “A new approach to computer-generated holography,” Appl. Opt. 9, 471-475 (1970).
[4] L. Cross, “The Multiplex technique for cylindrical holographic stereograms,” in
SPIE San Diego August Seminar (1977) [Presented but not published].
[5] S. A. Benton, “Hologram reconstructions with extended incoherent sources,” J. Opt. Soc. Am. 59, 1545-1546A (1969).
[6] W. Spierings and E. van Nuland, “Calculating the right perspectives for multiple photo-generated holograms,” in Int’l Symposium on Display Holography, T .H. Jeong, ed., Proc. SPIE 1600, 96-108 (1992).
[7] M. Halle, S. Benton, M. Klug and J. Underkoffler, “The Ultragram: A generalized holographic stereogram,” in Practical Holography V, S. A. Benton, ed., Proc. SPIE 1461, 142-155 (1991).
[8] M. Lucente, "Diffraction-Specific Fringe Computation for Electro-Holography", Ph. D. Thesis, Dept. of Electrical Engineering and Computer Science, MIT, (1994).
[9] M. Yamaguchi, N. Ohyama and T. Honda, “Holographic 3-D printer,” in Practical Holography IV, S. A. Benton, ed., Proc. SPIE 1212, 84-92 (1990).
[10] M. Klug, M. Holzbach, A. Ferdman, "Method and apparatus for recording 1-step full-color full-parallax holographic stereograms", US Patent US6330088B1 (1998).
[11] D. Brotherton-Ratcliffe, S. J. Zacharovas, R. J. Bakanas, J. Pileckas, A. Nikolskij and
J. Kuchin, “Digital holographic printing using pulsed RGB lasers,” Opt. Eng. 50, 091307-1-9 (2011).
[12] D. Brotherton-Ratcliffe, F. M. Vergnes, A. Rodin and M. Grichine M, "Method and apparatus to print holograms" Lithuanian Patent LT4842 (1999).
[13] D. Brotherton-Ratcliffe, F. M. Vergnes, A. Rodin and M. Grichine, "Holographic printer", US Patent US7800803B2 (1999).
[14] A. Rodin, F. M. Vergnes and D. Brotherton-Ratcliffe, "Pulsed multiple colour laser", EU Patent EPO 1236073 (2001).