Abstract: A new method of fabricating holographic θ modulation board is proposed. The filter is available to allow only ±1 frequency spectrum to pass in the spatial filtering optical system, thus two overlapping one-dimensional grating images and the sinusoidal interference fringes on the output plane are obtained when a parallel monochromatic beam of laser light focuses on the input plane. Three-equal-time exposal is necessary to record the figures of interference fringes with three different directions by using a rotatable bracket with hollow template and holographic plate, thus the θ modulation board is done.

Key words: holographic grating, θ modulation, spatial filtering, Fourier transform