Kinds Of Photosensitive Devices Used By Barcode Scanners

- Dec 11, 2019-

At present, there are four kinds of photosensitive devices used by barcode scanners in the market: photomultiplier tube, silicon oxide isolation CCD, semiconductor isolation CCD, contact photosensitive devices (CIS or LIDE).

The mainstream is two kinds of CCD, the principle is simple: on a single silicon crystal set into thousands to tens of thousands of phototransistors, these phototransistors are divided into three columns, respectively with red green blue filter cover, so as to achieve color scanning. Two kinds of CCD comparison, silicon oxide isolation CCD is better than semiconductor isolation CCD, familiar with the physics of friends naturally know the reason. It is simply said that the semiconductor CCD transistor leakage phenomenon will affect the scanning accuracy, with silicon oxide isolation will greatly reduce the leakage phenomenon (this is the insulator), of course, it is better to add the temperature control, because both semiconductor and conductor are generally temperature sensitive, heating conductivity will generally improve. Now the majority of the mainstream market is semiconductor isolation CCD, silicon oxide isolation CCD is less, obviously because the cost is higher. If you want to understand the effect of a bar code scanner, it is important to understand the quality of the bar code scanner is the photoelectric element, even if it is a semiconductor isolation quality is also different.

Contact photoreceptors, which typically use cadmium sulfide, the material we use to make photosensitive resistors, should be much cheaper to produce than CCDS (which is why CIS barcode scanners with the same accuracy are always cheaper than CCD barcode scanners on the market). The scanning distance is short, the scanning definition is low and sometimes even cannot reach the nominal value, the temperature change is easy to affect the scanning precision, these are the fatal problems of this kind of barcode scanner. Those familiar with physics should know that cadmium sulfide has a greater electrical leakage between resistors than a semiconductor partition, which reduces accuracy.

Photomultiplier tube, photosensitive material is mainly the oxide of cesium metal. Its scanning accuracy, even the degree of temperature and noise are the best, but also the most expensive. The average user, like me, is a dream user. It's too expensive and we'll skip over the specific technical features here.

The optoelectronic components of a barcode scanner are important factors in determining its performance, as are control circuits and software. It may be difficult to gain direct access to the information. We often only know a limited amount of content (trade secrets), when we judge the performance of a barcode scanner, we only rely on the actual operation and evaluation of the software to know.