This is similar to the manual machine tool method of clamping a micrometer onto a reference beam and adjusting the Vernier dial to zero using that object as the reference.
42.
The test beam passes through a somewhat large hole or aperture in the membrane, without losses due to absorption; the reference beam is focused onto the pinhole for highest transmission.
43.
A hologram is made by splitting a laser beam in two, aiming one half on the object to be depicted and then recombining it with the other half, the reference beam.
44.
Since the device is self-referencing it can be used in environments with a lot of vibrations or when no reference beam is available such as in many adaptive optics and short-wavelength scenarios.
45.
This holograph is illuminated with a reference beam to generate a hologram image of the object directly superimposed over the original object itself while the object is being subjected to some stress.
46.
The amplitude of the light at any point in the image is the sum of the light from the object ( object beam ) and the second beam ( reference beam ).
47.
In variants of the interference microscope where object and reference beam pass through the same objective, two images are produced of every object ( one being the " ghost image " ).
48.
The system can be seen as an interferometer with such a high intensity reference beam ( the local oscillator ) that unbalancing the interference by a single photon in the signal is measurable.
49.
If the hologram is illuminated with a light source incident at the original reference beam angle but a broad spectrum of wavelengths; reconstruction occurs only at the wavelength of the original laser used.
50.
The sensor also splits the laser beam into two parts; one ( the measurement beam ) is focused into the flow and the second ( the reference beam ) passes outside the flow.
