View source for HoloVID

'''HoloVID''' is a [[measuring instrument]], originally developed by Mark Slater for the [[holographic]] dimensional measurement of the internal [[isogrid]] structural webbing of the [[Delta (rocket family)|Delta]] family of [[launch vehicle]]s in 1981.

==History==
Delta launch vehicles were produced by [[McDonnell Douglas]] Astronautics until the line was purchased by [[Boeing]]. Milled out of T6 Aluminum on {{convert|40|by|20|ft|0|adj=on}} horizontal mills, the inspection of the huge sheets took longer than the original manufacturing. It was estimated that a [[Real-time computing|real time]] [[in situ]] inspection device could cut costs so an Independent [[Research and development|Research and Development]] (IRAD) budget was generated to solve the problem.  Two solutions were worked simultaneously by [[Mark Slater (composer)|Mark Slater]]: a photo-optical technique utilizing a [[holographic lens]] and an ultrasonic technique utilizing configurable micro-transducer multiplexed arrays.

A pair of HoloVIDs for simultaneous frontside and backside weld feedback was later used at [[Martin Marietta]] to inspect the long weld seams which hold the [[Space Shuttle external tank|External Tanks]] of the [[Space Shuttle]] together.  By controlling the weld bead profile in real time as it was [[gas tungsten arc welding|TIG generated]], an optimum weight vs. performance ratio could be obtained, saving the rocket engines from having to waste thrust energy while guaranteeing the highest possible web strengths.

==Usage==
Many corporations ([[Kodak]], [[Immunex]], [[Boeing]], [[Johnson & Johnson]], [[The Aerospace Corporation]], [[Silverline Helicopters]], and others) use customized versions of the Six Dimensional Non-Contact Reader w/ Integrated Holographic Optical Processing for applications from [[supercomputer]] [[surface-mount technology|surface mount]] pad assessment to genetic biochemical assay analysis.

==Specifications==
HoloVID belongs to a class of sensor known as a [[structured-light 3D scanner]] device.  The use of structured light to extract three-dimensional shape information is a well known technique.<ref>{{cite document |title=Real Time control of a Robot with a Mobile Camera |publisher=[[SRI International]], [[Artificial Intelligence Center]] |first=Gerald J. |last=Agin |date=February 1979 |id=Technical note 179}}</ref><ref>{{cite book |chapter=A RANSAC-based approach to model fitting and its application to finding cylinders in range data |title=Proceedings of the 7th International Joint Conference on Artificial Intelligence |volume=2 |first1=Robert C. |last1=Bolles |first2=Martin A. |last2=Fischler |pages=637–643 |date=24 August 1981}}</ref>  The use of single planes of light to measure the distance and orientation of objects has been reported several times.<ref>{{cite journal |title=Surface Measurement by Space-encoded Projected Beam Systems |journal=Computer Graphics and Image Processing |first1=J. L. |last1=Posdamer |first2=M. D. |last2=Altschuler |volume=18 |issue=1 |pages=1–17 |date=January 1982 |doi=10.1016/0146-664X(82)90096-X}}</ref><ref>{{cite book |chapter-url=http://www.ijcai.org/Proceedings/75/Papers/099.pdf |chapter=Forming Models of Plane-and-Cylinder Faceted Bodies from Light Stripes |title=Proceedings of the 4th International Joint Conference on Artificial Intelligence |volume=1 |first1=R. J. |last1=Popplestone |first2=C. M. |last2=Brown |first3=A. P. |last3=Ambler |first4=G. F. |last4=Crawford |pages=664–668 |date=3 September 1975}}</ref><ref>{{cite journal |url=https://pdfs.semanticscholar.org/cf57/5f36027ae74c628d6251d6453bc7c590b45e.pdf |archive-url=https://web.archive.org/web/20161019030826/https://pdfs.semanticscholar.org/cf57/5f36027ae74c628d6251d6453bc7c590b45e.pdf |url-status=dead |archive-date=2016-10-19 |title=Object Recognition Using Three-Dimensional Information |journal=IEEE Transactions on Pattern Analysis and Machine Intelligence |first1=Masaki |last1=Oshima |first2=Yoshiaki |last2=Shirai |volume=5 |issue=4 |pages=353–361 |date=April 1983 |doi=10.1109/TPAMI.1983.4767405|pmid=21869120 |s2cid=17612273 }}</ref>

The use of multiple planes<ref>{{cite book |chapter=Six-Dimensional Vision System |title=Proceedings of the SPIE: Robot Vision |volume=0336 |first1=J. |last1=Albus |first2=E. |last2=Kent |first3=M. |last3=Nashman |first4=P. |last4=Mansbach |first5=L. |last5=Palombo |first6=M. |last6=Shneier |editor-first1=Azriel |editor-last1=Rosenfeld |pages=142–153 |date=22 November 1982 |doi=10.1117/12.933622 |bibcode=1982SPIE..336..142A|s2cid=64868995 }}</ref><ref>{{cite journal |title=Welding machine using shape detector |journal=Mitsubishi-Denki-Giho |language=ja |first=S. |last=Okada |volume=47 |issue=2 |page=157 |date=1973}}</ref><ref>{{cite document |title=Progress Report on Visual Inspection of Solder Joints |publisher=Massachusetts Institute of Technology, Artificial Intelligence Lab |first=Dave |last=Taenzer |date=1975 |id=Working Paper 96}}</ref> and multiple points<ref>{{cite book |chapter=Automatic Visual Inspection Of Solder Joints On Printed Circuit Boards |title=Proceedings of the SPIE: Robot Vision |volume=0336 |first=Yasuo |last=Nakagawa |editor-first1=Azriel |editor-last1=Rosenfeld |pages=121–127 |date=22 November 1982 |doi=10.1117/12.933619 |bibcode=1982SPIE..336..121N|s2cid=109280087 }}</ref><ref>{{cite document |title=Low-level processing of registered range and intensity data |publisher=[[SRI International]], [[Artificial Intelligence Center]] |first1=R. O. |last1=Duda |first2=D. |last2=Nitzan |date=March 1976 |id=Technical note 129}}</ref> of light to measure shapes and construct volumetric estimates of objects has also been widely reported.<ref>{{cite book |chapter=The Measurement and Use of Registered Reflectance and Range Data in Scene Analysis |title=Proceedings of the IEEE |first1=David |last1=Nitzan |first2=Alfred E. |last2=Brain |first3=Richard O. |last3=Duda |volume=65 |issue=2 |pages=206–220 |date=February 1977 |doi=10.1109/PROC.1977.10458|s2cid=8234002 }}</ref>

The use of segmented phase holograms to selectively deflect portions of an image [[wavefront]] is unusual.  The holographic optical components used in this device split tessellated segments of a returning wave front in programmable bulk areas and shaped patches to achieve a unique capability, increasing both the size of an object which can be read and the [[Cartesian coordinate system|z-axis]] depth per point which is measurable, while also increasing the simultaneous operations possible, which is a significant advance in the previous state of art.

==Operational modes==
A [[Laser|laser beam]] is made to impinge onto a target surface.  The angle of the initially [[Nonlinear optics|nonlinear optical]] field can be non-[[orthogonal]] to the surface.  This [[light beam]] is then reflected by the surface in a wide conical spread function which is geometrically related to the [[angle of incidence (optics)|incidence angle]], light frequency, wavelength and relative [[surface roughness]].  A portion of this reflected light enters the [[Optics|optical system]] coaxially, where a 'stop' shadows the edges.  In a single point reader, this edge is viewed along a radius by a [[photodiode array]].

The output of this device is a boxcar output where the photodiodes are sequentially lit diode-by-diode as the object distance changes in relation to the sensor, until either no diodes are lit or all diodes are lit.  The residual product charge dynamic value in each light diode cell is a function of the [[bias current]], the [[dark current (physics)|dark current]] and the incident [[ionizing radiation]] (in this case, the returning laser light).

In the multipoint system, the HoloVID, the cursor point is [[acousto-optical]]ly scanned in the x-axis across a <math>k\theta</math> monaxial transformer.  A monaxial holographic lens collects the wave front and reconstructs the pattern onto the single dimensional photodiode array and a two dimensional matrix sensor. [[Image processing]] of the sensor data derives the correlation between the compressed wave front and the actual physical object.

==References==
{{Reflist}}

[[Category:Dimensional instruments]]
[[Category:Holography]]
[[Category:Optical devices]]