Compact electronic speckle pattern interferometer using a near infrared diode laser and a reflection holographic optical element

The complicated experimental set-ups required for existing electronic speckle pattern interferometers limit their application potential. To overcome the limitations we present a simple and very compact electronic speckle pattern interferometer. Our system does not use expensive and complicated optical elements. We used a near infrared reflection holographic optical element for the first time in an out-of-plane sensitive electronic speckle pattern interferometer operating with a near infrared diode laser. The use of a holographic optical element drastically reduces the number of optical elements; the final system only consists of a CCD camera, a HOE and a test object, with significant reductions in system costs and time spent aligning the system. Reflection holographic optical elements were recorded in HP-650 emulsions using a He-Ne laser. The hologram was reconstructed using a laser diode operating at 784 nm by swelling the emulsion. Current modulation of the laser diode was utilized to introduce the desired phase shifts for fringe analysis.