At the beginning of colony counting, it was directly counted by human eyes or optical microscope, but it is easy to get visual fatigue, and the visual by different people will increase the possibility of colony counting errors or incorrect judgment of appearance types. Therefore, to avoid counting errors and unify the method for judging the outward appearance of colonies, an automatic colony counter by an optical system, a digital camera, and an optical image recognition system is needed. Moreover, the digital images can be saved for a long time, and it can be reviewed.

• Advantages of colony counter

1. Manual counting methods take time also there is huge quantities of specimen.
   In case of more than 300 colonies in one petri dish, it takes 5 minutes by manual measurement, but it takes only 3 seconds by automatic measurement.
2. Measuring method is not consistent due to visual measurement.
   Individual measurement with fi¬xed size range of colonies makes stable and consistent measurement.
3. Measurement accuracy decreases when in measuring a widespread colony.
   In terms of automatic measurement, widespread colonies can be excluded automatically from measurement objects. Measurable areas are automatically calculated and it enables accurate CFU conversion.
4. Existing measuring devices is unable to measure separately in terms of various color case.
   With a color photography lens, it can classify colonies based on different colors, sizes, brightness and so on.