Abstract

Hologram reconstruction is very sensitive to the wavelength. When the reconstruction wavelength is changed, there is an angular and a focal-length shift resulting in both a lateral shift and a longitudinal shift of the reconstructed image. There is also associated wave front distortion. All these have adverse effects on the holographic scanners if semiconductor lasers are used as the light source. We have investigated these problems and found that by using an additional grating or hologram, these adverse effects can be sufficiently compensated so that the scanners can be used for practical applications. For example, our studies have shown that the angular shift can be reduced by 100 times while keeping the wave front distortion within an acceptable range. We also found that the scan line straightness worsens by as much as 34%. However, these may be still within the acceptable range for less critical applications. The trade-offs between different parameters for different applications are discussed. Our preliminary results indicate that a practical holographic scanner system employing GaAlAs (or GaAs) lasers with good efficiency and good wavelength shift tolerance can be designed and built.

© 1985 Optical Society of America