Presentation on theme: "The HeNe laser used in holography research"— Presentation transcript:
1 The HeNe laser used in holography research An 8 milliwatt HeNe laser in S-135 of the Science Building. This is an example of an inexpensive random polarization Helium Neon laser emitting light at nm.
3 Holographic filmGlass PlateObjectLaser BeamReflection Holography in its simplest formFilm Emulsion
4 What is Reflection Holography? If coherent light beams (waves of the same phase with respect to each other) are allowed to combine the result will be as described in the previous bullet. This is called interferenceIn this research a helium neon (HeNe) laser is used to produce coherent light waves of wavelength 633 nanometers (nm) and can be identified by its bright red colorIn one form of a reflection hologram one beam penetrates the film and another similar beam is scattered from an object to the rear of the film backwards onto the film itself. The resulting interference produces a white light hologram of which several examples are shown hereThe process itself is referred to as holography; whereas the recording film is called a hologramThese terms were coined by Denis Gabor (the father of holography) in 1947The word hologram is derived from the Greek words “holos” (meaning whole or complete) and “gram” (meaning message)Light contains wave characteristics. Thus various light beams can interfere destructively (dark spot) or constructively (bright spot)
12 Some things you must be concerned about in Holography What is Polarization?Polarization of the laser beamLinear PolarizationRandom PolarizationAll laser light is polarized. The linear polarized laser if fixed. Rotate the laser to shift the polarization.
13 PFG-03M Slavich FilmUltra fine-grained red sensitive plates and film designed for reflection hologram recording. Average grain size is 8-12nm, resolving power more than 5000 lines/mm, spectral sensitivity range includes 633nm, 647nm.Using GP-2
15 JARB (JD-4) Processing Note typo error! The discovery of using JARB for quick processing of holograms recorded on Slavich PFG-03M plates and film was made by Tung H. Jeong, Riley Aumiller, Raymond Ro, and Jeff Blyth; thus it is called the JARB processing regime. Commercially, the chemical developer used is now called called JD-4.JARB is ideal for making holograms during a lecture demonstration, or for laboratory exercises or workshops where many students must make holograms in a limited time. The advantage of JARB is that it effectively increases the sensitivity of PFG-03M ten times, from 1.50 to 0.15 millijoules/cm2. Thus the exposure time for holograms is one-tenth as long as when processed in GP-2. The typical development time is 20 seconds. Finally, drying time is drastically reduced by using warm air (from a hair dryer) because the JARB development hardens the emulsion. The total processing time using JARB can be as short as three minutes, from developing to drying!Using PFG-03M film or plate, expose the hologram so that each square centimeter area receives 0.15 to 0.4 millijoules of energy (there is batch-to-batch variation). For example, if a 5 milliwatt diode laser without a lens is location 40 cm from the plate, the exposure time is approximately 5 to 7 seconds.
16 Viewing your hologramTo view your hologram, you need an appropriate viewing angle and light source. With the appropriate light source, view the image by shining the spot light at the hologram from approximately the same angle you had the laser shoot when you were first exposing plate. You might need to tilt the plate left and right or forward and back to maximize the brightness of the image. It may take some practice.As for the light source, ideally, you want a bright spot light. Spot lights concentrate the light using a built-in reflector so that all the light is confined to the correct angle. Spot light are available at any K-Mart, Wal-Mart, and most other retail store. As a cheap substitute, you could also use a $1.98 (batteries included!) Rayovac pin light from K-Mart. In general, you cannot view a reflection hologram with a laser, fluorescent light, or light from a frosted bulb.
17 The “standard medallion” used for calibration purposes