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A new type of heterodyne interferometer was made through direct modulation of a diode laser wavelength. A measurement accuracy of better than lambda/50 and repeatability of lambda/100 were obtained. This interferometer shows promise for use in testing wavefront aberrations, especially in optical disk systems.

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As a new method of making high-quality and high-storage-density holograms capable of storing such image information as pictures and portraits, combination of the sampling method and random phase shifter method is proposed. This method reduces the concentrations of information light energy on the hologram plane which are located evenly in the just Fourier-transformed plane. As an experimental result, the light waves passing through 106 sampling points on a frame information with random phases were focused into a spot to make a hologram of 2.0-mm diameter. The reconstructed image from the hologram showed high quality without speckle and high efficiency.