| 摘要 |
<p>A lens testing method and apparatus is disclosed to test the transfer function of a lens at a multiple number of points in the lens and to locate the best focal plane and format position of the lens within the specified focal range of the lens. The lens is mounted in the lens tester between the object plane and the image plane. The object plane has a multiple number of beam forming apertures which are illuminated to project individual light images through the lens to respective targets or target segments in the image plane. The targets are a multiple number of apertures geometrically similar to the object aperture, having a fixed orientation to the object plane apertures. The target and object planes are moved relative to one another such that the individual light images are moved across the apertures of their corresponding targets. The light images passing through the target apertures are sensed to determine the transfer function of the lens at the respective points in the image plane. The lens may be rotated 90.degree. to test the meridional and the sagittal transfer function of the lens at each point. In operating the lens tester, the lens is first moved to a suitable focal plane and the value of the transfer function at the desired points in the image are compared with predetermined minimum acceptable values of the transfer function. If the value of the transfer function at any tested point in the lens falls below the minimum acceptable value, the lens is moved to another suitable focal plane and again tested. Once all the points in the lens test above the minimum value of the transfer function for each respective point, the total of the transfer functions for each format position is determined by rotating the lens and testing again. The one best format position and focal plane is then found by comparing the total value of the transfer function for each point in each suitable focal plane within the lens focal range with the total value of the previous best focal plane. The lens may be rotated any number of steps in each focal plane to test as many format positions around the lens as desired to determine the best format position in the best focal plane.</p> |
