Assessment of image quality of optical systems

Spot diagrams and the synthesized images of the Siemens star object obtained by an image synthesizer in which the above spot diagrams obtained on a cathode-ray tube were used as the light sources, were compared with the aberration curves and the optical traasfer function of the same manufactured lens. The comparison was performed on several field angles and image planes. Systematic comparison of these results gives us versatile information about the image quality of the lens and enables us to understand the mutual relations existing between them. For instance, spurious resolution and heavy deterioration of the images were observed on the synthesized images when there were negative components in the transfer function. Also, it was found that there was an intimate relation between the above defects of images and the spread of the spot diagrams. Next we set the model lenses based on the above one. In these model lenses, certain aberrations were intentionally altered slightly from the initial values without changing the other aberrations. As for these model lens systems, comparisons similar to the above were performed in order to examine the effect and the way each aberration contributed to image quality.