Loops control
Product: Inoculating loops
Settor: Biomedical
Vision System: Tattile
SmartReader M6-A with LVDS digital camera 1024x768 BW
Illumination: 2 IR illuminator
Application
One of the worldwide leader in the manufacturing of systems for microbiology pick and place, has developed a solution for automatic planting and streaking of all microbiological samples.
The system performs the following analysis:
- Barcode reading and identification;
- Preparation of samples (shaking and spinning);
- Sample opening;
- Liquid sample picking: these operations are done by a loop (metal ring) calibrated to pick a pre-set quantity of the sample;
- "Sowing" of sample on Petri dish
- Sample closing
- Labelling
The customer asked for a Vision System able to:
- Check the cleaning and deformity of loop (mounted on a thin metal swab)
- verify the presence of the sample on the loop
The customer needed to change its old vision system based on pattern matching because, in a delicate sector like microbiological inspection, it is necessary to have a state of the art solution.
The system is made of:
- Smart Reader M6-A LVDS
- I/O expansion module.
- LVDS camera B/W 1024x768.
- 2 x IR lighting systems with a switching regulator
The system uses IR illumination at around 810 nm: in this way it is immune from noises generated by ambient light.
The software has a pre-analisys function able to delete the bad reflection and detect the position of loops.
The algorithm perform 3 analisys, each one on 4 different loops:
First analisys is a "frontal control":
- correct shape of metal swab
- Classification control
- Empty loop
- Height of the loop
Second analisys is a "Lateral Control":
- Straightness of metal swab
- Classifcation control
- correct height
Thirth analisys is the "Check liquid presence":
- Straightness of metal swab
- Sample presence/absence on loops
Problematics
The main problem has been the correct evaluation of the lighting system.
The object looks like a thin watery film, sometimes not visible to the human eye. For this reason specific techniques have been used by Tattile engineers to identify the correct parameters useful for the measurements.
Two are the techniques used:
- Backlight: used for those loops with a capacity of more than 1 µL (10 and 30 µL). The liquid into the sample creates a Fish-eye effect and the end result is a darker region on the sample, which allows a more reliable measurement.
- Frontlight:used for those loops with a capacity of 1 µL. In this case the liquid film is far too thin to obtain a sufficient optical reflection and it is necessary to increase the distance between the source and the sample to appreciate the deviation of the smallest angles of light.
