Single-chip monochrome cameras
Until today, monochrome cameras are the workhorses in machine vision. Despite the competition in the form of colour cameras, most applications get along with the additional colour information if this is not specially required.
Workaround for the use of monochrome cameras in colour lenses of similar brightness: when using monochrome cameras, single colours of the test objects can be brightened or darkened using coloured lighting and can thus still be differentiated. In this way the use of a colour camera can possibly be avoided.
Advantages over colour cameras
- High sensor and detail resolution: no misinformation like in the case of single-chip colour cameras due to colour interpolation, higher resolution than in the case of three-chip colour cameras
- Smaller data quantity of the image information allows for higher frame rates when transmitting the images
- High sensitivity to light: the entire light quantity incides on the sensor, no additional light-reduction colour filters on the pixels like in the case of single-chip colour cameras or losses of light due to prisms like in the case of three-chip cameras
Spectral sensitivity of standard sensors
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Important for machine vision
- The majority of monochrome area scan cameras are equipped with CCD sensors by Sony. Special cameras with higher-resolution CCDs or particularly fast frame rates often use TrueSense(Kodak) CCD sensors. Look for state-of-the-art sensor elements which are more sensitive and lower in noise than previous versions in most of the cases.
- CCD sensors have a high linearity and homogeneity. In case of high-quality measuring applications and inspections which make extreme requirements for the image quality, this is ideal.
- Extremely high frame rates can be achieved using CMOS sensors.
- CMOS sensors are particularly resistant to overexposure and do not show any blooming and smearing effects. Ideal for the inspection of strongly reflecting materials.
- Miniaturised cameras are often cheaper, technical features or the signal processing, however, are "downgraded". In case of high-quality measuring applications and inspections which make extreme requirements for the image quality, this can lead to losses in the evaluation result.
- Despite identical sensors, cameras of different manufacturers vary in the image quality, depending on the triggering and signal processing. Yet the manufacturers' data sheets with their detailed information are not directly comparable. Get expert advice!