Abstract A ruby or other solid laser is made to generate two or more closely adjacent optical frequencies. By illuminating an object to be recorded holographically with the laser light, range contours are generated when the hologram is reconstructed. The range contours can be made to have distances on the order of 5 millimeters or more by utilizing a ruby laser. To this end, one of the two boundaries of the optical cavity for the laser is formed by a suitable mode selector, such, for example, as a Fabry-Perot resonant reflector, a prism or a grating. The thickness of the resonant reflector is so selected that two or more frequencies may be generated within the lasing linewidth of the laser. Preferably, in order to obtain better contrast, the optical length of the cavity is a multiple of the optical thickness of the resonant reflector. The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).
A holographic apparatus as defined in claim 1 wherein said pulsed laser is a ruby laser.
Claim 2
Dependent Claim
16 words
A holographic apparatus as defined in claim 1 wherein said pulsed laser is a neodymium laser.
Claim 3
Dependent Claim
39 words
A holographic apparatus as defined in claim 1 wherein said second optical means consists of an interferometric device for separating the light paths of the light from said laser in accordance with each of the frequencies of the light.
Claim 4
Dependent Claim
17 words
A holographic apparatus as defined in claim 1 wherein said second optical means consists of a prism.
Claim 5
Dependent Claim
19 words
A holographic apparatus as defined in claim 1 wherein said second optical means consists of a Fabry-Perot resonant reflector.
Claim 6
Dependent Claim
18 words
A holographic apparatus as defined in claim 6 wherein said resonant reflector consists of a slab of sapphire.
Claim 7
Dependent Claim
19 words
A holographic apparatus as defined in claim 6 wherein said resonant reflector consists of two spaced slabs of quartz.
Claim 8
Dependent Claim
36 words
A holographic apparatus as defined in claim 6 wherein said resonant reflector has an optical thickness selected to permit lasing of said laser at at least two separate frequencies, each being disposed within said lasing linewidth.
Claim 9
Dependent Claim
28 words
A holographic apparatus as defined in claim 6 wherein the optical length of said optical cavity is an integral multiple of the optical thickness of said resonant reflector.
Claim 10
Dependent Claim
195 words
Holographic apparatus for recording a hologram of an object to be recorded and for providing contour lines on the object when the hologram is viewed, said apparatus comprising: a. a pulsed laser including a ruby rod; b. optical means for pumping said ruby rod, said laser generating substantially coherent light having a given lasing linewidth of about 0.25 A.; c. said ruby rod being enclosed by an optical cavity, said optical cavity comprising a light reflector to define one end of said cavity and a Fabry-Perot resonant reflector defining the other end of said cavity, said resonant reflector having an optical thickness such as to select at least two frequencies within said lasing linewidth and providing sufficient gain for causing said laser to lase within said selected frequencies, said optical cavity having an optical length which is a multiple of the optical thickness of said resonant reflector; d. means for splitting the laser beam into a scene beam and a fixed reference beam; e. a light-sensitive recording medium disposed in a predetermined plane; and f. means for directing said reference beam onto said recording medium and for directing said scene beam first onto recording medium.