AUTOMATIC ELECTRONIC CAMERA FOR LABEL IMAGE CAPTURE

摘要

A hand held label reader (10) is capable of illuminating a label (20), capturing a digital image of two-dimensional information indicia (15) on the label, and decoding the digital image to provide decoded output data to a terminal (35). The target label is illuminated by a low variation illuminator that includes a circular LED array mounted behind a plano-convave dispersing lens. The automatic electronic camera, which includes a CCD camera and control circuitry, uses three images to adjust the intensity of the digital image and store a properly exposed image of the label in video RAM. The intensity of the digital image is adjusted by controlling the video system gain via adjusting the CCD array's integration time, the gain of a video amplifier, and the gain provided by an analog-to-digital converter. The gain provided by the analog-digital-converter is adjusted to compensate for the attenuation of light through the camera's lens assembly. For the first image, the digital image is obtained using a default setting for the gain. The image intensity is analyzed using a histogram process and new gain settings are determined. The second image is obtained using the gain settings derived from the first image. The second image intentity is analyzed and the gain settings are adjusted. These settings are used for the third video image. The digital image from the third image is stored in video RAM, where it is available to be decoded by a microprocessor.