The Fa­ther of Holog­ra­phy

DEN­NIS GA­BOR

The Borneo Post - Good English - - Short Story Section -

HUN­GAR­IAN in­ven­tor Den­nis Ga­bor is known as the Fa­ther of Holog­ra­phy.

When the Firt World War ended in late 1918, he be­gan stud­ies in elec­tri­cal en­gi­neer­ing in Bu­dapest which he fin­ished at the Tech­ni­cal Hochschule Ber­lin-Char­lot­ten­burg, where he ob­tained a Diploma in Elec­tri­cal En­gi­neer­ing in 1924. He also at­tained the de­gree of Doc­tor of En­gi­neer­ing (Dr-Ing.) in 1927 with a the­sis re­lated to the de­vel­op­ment of one of the first high speed cath­ode ray os­cil­lo­graphs.

That year he also joined Siemens

& Halske AG, Ber­lin, where he started work­ing in one of the phys­i­cal lab­o­ra­to­ries, in which Ga­bor be­gan to de­velop some of his nu­mer­ous in­ven­tions. As proof of his fruit­ful work as an in­ven­tor, Ga­bor filed 62 patents be­tween 1928 and 1971. In 1933, a few weeks af­ter Hitler came to power, Ga­bor left Ger­many be­cause the com­pany did not re­new his con­tract due to his Jewish ori­gin. In 1934, and af­ter a short pe­riod in Hun­gary, he went to Eng­land, where he got a job with the Bri­tish Thom­son-Hous­ton Com­pany in Rugby.

Through­out his en­tire life Ga­bor al­ways said he was an en­gi­neer and in­ven­tor rather than a sci­en­tist, even though his work was al­most al­ways re­lated to ap­plied physics. But Ga­bor was also a hu­man­ist in the sense of the Re­nais­sance: vo­ra­cious reader, writer, es­say­ist, man con­cerned about the tech­no­log­i­cal so­ci­ety of the late twen­ti­eth cen­tury and mem­ber of the Club of Rome. Since 1958 he de­voted much of his time to study the fu­ture of our in­dus­trial civil­i­sa­tion on which he pub­lished, among oth­ers, the book In­vent­ing the Fu­ture, pub­lished in 1963, and where he stated:

“You can­not pre­dict the fu­ture, but you can cre­ate it.”

Holog­ra­phy be­gins to take its first steps in 1947 in a lab­o­ra­tory of an elec­tri­cal en­gi­neer­ing com­pany where Ga­bor was work­ing on im­prov­ing the elec­tron mi­cro­scope. This in­stru­ment had in­creased one hun­dred times the re­solv­ing power of the best op­ti­cal mi­cro­scopes and it was very close to solv­ing the atomic struc­tures, but the sys­tem was not quite per­fect. Its main lim­i­ta­tion was re­lated to the spher­i­cal aber­ra­tion of the mag­netic lenses of the mi­cro­scope. To solve this prob­lem Ga­bor asked him­self: “Why not take a bad elec­tron pic­ture, but one which con­tains the whole in­for­ma­tion, and cor­rect it by op­ti­cal means?”

Ga­bor came up with the an­swer to this ques­tion while he was wait­ing for a game of ten­nis on Easter Day 1947 and it was to con­sider a two-step process. In the first stage, the record­ing, the in­ter­fer­ence pat­tern be­tween a co­her­ent elec­tron beam (ob­ject wave) and a “co­her­ent back­ground” (ref­er­ence wave) is recorded on a pho­to­graphic plate. Ga­bor called this in­ter­fer­ence pat­tern “holo­gram”, from the Greek word “ho­los”, the “whole”, be­cause it con­tained the whole in­for­ma­tion (am­pli­tude and phase) of the ob­ject wave.

In the sec­ond stage, the re­con­struc­tion, the holo­gram is il­lu­mi­nated with vis­i­ble light and the orig­i­nal wave­front is re­con­structed, so that the aber­ra­tions of the elec­tron op­tics can be cor­rected by op­ti­cal meth­ods. There­fore, the phys­i­cal prin­ci­ples of holog­ra­phy are based on the wave na­ture of light and they are in­ter­fer­ence (record­ing step) and dif­frac­tion (re­con­struc­tion step). He spent the rest of the year work­ing on his ‘new mi­cro­scopic prin­ci­ple’.

To ob­tain con­trast in­ter­fer­ence fringes it is nec­es­sary to use a light source of high co­her­ence, which did not ex­ist in times of Ga­bor (the laser was in­vented in 1960). Due to this, Ga­bor made his first holo­gram in 1948 us­ing a light source that con­sisted of a mer­cury arc lamp with a nar­row-band green fil­ter, one of the best co­her­ent light sources be­fore the laser.

The ob­ject was a tiny cir­cu­lar trans­parency (1.4 mm di­am­e­ter) of opaque let­ter­ing on a clear back­ground con­tain­ing the names of Huy­gens, Young and Fres­nel, three physi­cists who were con­sid­ered im­por­tant by Ga­bor be­cause they de­vel­oped the phys­i­cal ba­sis of his tech­nique, which he called “wave-front re­con­struc­tion”.

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