Apparatus for limiting the output signal frequency band of an optical sensor

DETAILED DESCRIPTION Accordingly, it is an object of the present invention to provide a signal processing apparatus for a digital camera having a solid-state imaging device that can eliminate the above-noted defects inherent in the prior art.
Another object of this invention is to provide a signal processing apparatus for a solid-state video camera that is capable of satisfactorily depressing aliasing noise that is included in the digital signal.
A further object of this invention is to provide a processing apparatus for a solid-state video camera that can improve the modulation transfer function characteristic at the high-frequency band.
In accordance with an aspect of the present invention, the above objects are accomplished by providing a signal processing apparatus for use with a video camera that includes at least one solid-state image sensing device, a first clock generator that generates a sampling clock signal having a frequency f1 that is used to drive the solid-state image sensing device, an optical low-pass filter, a pre-signal processing circuit that includes an electrical low-pass filter and an analog-to-digital converter, and a main signal processing system connected to the pre-signal processing circuit.
This apparatus is characterized in that the frequency f1 is selected higher than the frequency f2 so that the optical low-pass filter depresses a frequency component band of f1-1/2 f2 to f1 of the image signal, and the electrical low-pass filter depresses the frequency component band which is higher than 1/2 f2.
The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof to be read in conjunction with the accompanying drawings in which like reference numerals represent the same or similar elements.