A study of the quality of holographic real images with the introduction of image point aberrations
The aim of this work is to investigate the effects of deviations from the ideal reconstruction on the quality of the holographic real image. The deviations include varying the angle of incidence of the reconstruction beam, varying the distance of the source of that beam, altering its wavelength from that of the recording, and changing the medium in which the hologram is replayed with respect to that in which it was recorded. From the results, the tolerance of several common recording geometries to these changes were evaluated and recommendations made as to which of the geometries are most suitable for use in the recording of holograms of which will result in images of the highest quality with respect to resolution and dimensionality for objects covering narrow and wide field angles. This is done for both in-air and underwater holograms. It is also the aim to evaluate the quality of each image theoretically to find the relationship between the ideal and the practically observed image resolutions. The theoretical values were calculated utilising third-order approximations based on work by Meier (1) and Champagne (2) to obtain coefficients for each of the point image aberrations present thus determining which of the aberrations are present for each variation in each goemetry and which determine the extent of the reduction in the quality of the image. These results were utilised in ensuing calculations of image resolution for each of the recording / reconstruction geometry combinations which exploit the aberration tolerance conditions proposed in the work by Born and Wolf(3). These theoretical values of resolution are compared to those found experimentally and reasons for discrepancies suggested.