초록 ▼

A method and apparatus for reading bar codes or other images while reducing or eliminating the need for self-generated illumination. An image reader is preferably embodied as a handheld unit and comprises an efficient optical collection system including an aperture with a high aspect ratio and/or a

A method and apparatus for reading bar codes or other images while reducing or eliminating the need for self-generated illumination. An image reader is preferably embodied as a handheld unit and comprises an efficient optical collection system including an aperture with a high aspect ratio and/or a multi-focal lens or lenses. An optically transmissive spacer affixed to the front of the handheld unit allows ambient light to be collected at close range, and a diffuser may be used to reflect ambient light from the handheld unit to provide additional illumination at close range. A masked CCD detector with rectangular pixels receives collected light and is coupled to an adaptive exposure circuit for preventing saturation of the CCD detector at high illumination levels. A correlated double sampling circuit coupled to the adaptive exposure circuit rejects common mode noise and allows operation in lower light levels. The correlated double sampling circuit is connected to a signal processor which uses a derivative based technique for detecting edges of the image. A decoder uses the edge detection information to decode encoded information from the image.

대표청구항 ▼

[ What is claimed is:] [1.] An apparatus for reading encoded images comprising:focusing optics for collecting light;a photosensor positioned so as to receive light collected by said focusing optics, and generating a photosensor output signal thereby;a correlated double sampling circuit connected to

[ What is claimed is:] [1.] An apparatus for reading encoded images comprising:focusing optics for collecting light;a photosensor positioned so as to receive light collected by said focusing optics, and generating a photosensor output signal thereby;a correlated double sampling circuit connected to said photosensor output signal, said correlated double sampling circuit comprising circuitry selected from the group consisting of: a dual slope processor and a dual sampler processor; anda decoder connected to said correlated double sampling circuit.