What Is a Visual Sensor?
A visual sensor is a sensor that recognizes an object by extracting features such as the position, size, shape, and color of the object to be measured after removing noise components and digitizing the signal from the image signal captured by a video camera.
An example of the use of visual sensors is the visual inspection of products.
Normally, the visual inspection of a product is performed by experienced workers, but it is a very difficult task because the workers have to concentrate for a long period of time.
In such product appearance inspections, visual sensors are used to capture images of the product and compare them with data on normal products prepared in advance, making it possible to conduct highly accurate inspections in a short time.
Uses of Visual Sensors
Visual sensors are currently used in a variety of fields.
In industrial settings, they are being introduced into systems that replace visual inspections. As mentioned above, they are applied to visual inspections to check for scratches and defects, as well as presence/absence inspections to count quantities and check for missing items.
In combination with advanced image analysis technology, character identification and 3D measurement have also been realized.
They are also used to check for scratches and stains on the surface of metal, wood grain, and resin products, external shape and stains on food products, and foreign matter contamination, as well as to detect the state of component mounting and soldering defects on printed circuit boards, and to check for foreign matter contamination and scratches on semiconductors.
Principle of Visual Sensors
CCD sensors and CMOS sensors are used as image sensors.
CCD sensors utilize photodiodes that can detect light and convert it into a voltage.
Photodiodes have the property of converting light into voltage. The converted voltage is amplified.
This is collected and output as a single image data.
On the other hand, CMOS sensors use photodiodes in the same way, but the voltage-converted data for each pixel is output as a single image data after noise is removed.
Traditionally, CCD sensors were mainly used for performance and cost reasons, but are now being replaced by CMOS sensors due to their improved performance.
Image data extracted from a CCD or CMOS sensor is converted to digital data, which is then converted to storable data under the control of a system control controller such as an ASIC and transferred to memory.
Generally, image data stored in memory is used to process image data according to various purposes and applications. For example, it is assumed that features such as image size, color, and shape will be extracted and compared with reference data to perform appearance inspections.