A transmissive filter for correcting illuminance distribution is positioned between a lens for forming an image of an illuminated original on an image forming surface and the image forming surface, or between the original and the image forming lens, and having transparent areas for passing light therethrough and opaque areas for blocking light, for correcting illuminance irregularities on the image forming surface. The transmissive filter has lowest transmittance around an effective pupil formed by projecting an exit pupil of the lens onto the filter when the filter is disposed between the lens and the image forming surface, or lowest transmittance around an effective pupil formed by projecting an entrance pupil of the lens onto the filter when the filter is disposed between the original and the lens. The transmittance is progressively higher concentrically in a stepwise manner toward an axial center and an outer periphery of the filter.

A film scanner wherethrough light is transmitted to a photoresponsive device has an optical path whereby specularly transmitted light passes and impinges on a predetermined area of the device. Scattered light passes to the device but impinges upon the detecting surface thereof over a greater area than the predetermined area. To enhance the relative response of the device to scattered light, an attenuating filter is placed over the predetermined area of the detecting surface.

The focal range of a focussed laser beam is enlarged with a simple optical stop where the beam has a Gaussian cross-sectional profile. The stop is arranged between the laser producing the beam, and a beam focussing lens system, and it is provided with an aperture of predetermined diameter with respect to that of the laser beam whereby the outer portion of the beam represented by the low intensity skirts of the profile curve is stopped. This arrangement can influence the focal range up to a 75 percent increase over that obtained with the unstopped beam.

A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

Simple, inexpensive and durable multi-element lens systems are provided. These lens systems may be optically coupled to digital image-capturing devices, such as those used in digital cameras. Some lens systems of the present invention include a glass microsphere bonded to a planar surface of a glass hemisphere. In preferred lens systems, the thickness of the glass hemisphere is selected to form an image plane for transmitted light that is tangent to the surface of the microsphere. Accordingly, in digital cameras fabricated with such lens systems, the glass microsphere can be attached directly to a digital image-capturing device. These preferred lens systems require no focusing adjustment and are suitable for applications to requiring a wide field of view. In some embodiments, the glass microsphere is bonded to the glass hemisphere using a light-absorbing material in order to create an apodized pupil. Some such embodiments are fabricated with a light-absorbing material with an absorption coefficient that varies according to the wavelength of transmitted light.