Select "Color" if the color fidelity or coloration of an object is important. If this is not the case, select "Mono". Monochrome cameras have some advantages. These include a higher sensitivity of the sensor compared to color cameras. In addition, no effort is required to create color information. Furthermore, the image information is immediately available in contrast to a color camera, which needs a certain amount of time to reconstruct the color information for each individual pixel.
Field of view (FoV) is the section of the object that is captured by the camera, i.e. that is imaged onto the sensor by the optics.
The size of the object has a direct influence on the required resolution or optics of the camera.
In principle, the larger the object, the further away from the camera it should be if it is to be completely captured by the camera.
In Machine Vision, there are great differences in the field of views that are used. They range from very small objects (e.g. printed circuit boards or microscopy) to large objects (e.g. vehicles on motorways).
The working distance is the distance between the object and the lens. In combination with the field of view,
the working distance defines the required focal length and resolution of the lens or system.
Pay attention to optical distortion, especially if the lens has a short focal length. The working distance should
correspond the field of view. In PCB inspection a small field of view and a small working distance is often useful,
in a toll bridge a large field of view and a large working distance.
The detail size describes the minimum characteristics to be detected in your field of view. This information is important to determine the right resolution. Resolution is the ability of a vision system to reproduce certain smallest structures.
Especially for the inspection of very small objects (e.g. passive electrical components or small barcodes) a high resolution and accuracy of the system is required. For reliable error detection, the optical resolution should be twice as high as the minimum error: optical resolution = detail size / 2.
Other applications, e.g. Flat Panel Display Inspection, can also have increased requirements with respect to resolution if small details on a large object are to be captured. Below we show one examples to illustrate what the detail size is.
The movement of objects mainly influences the usable shutter type of the camera. Rolling shutter sensors and cameras equipped with them are less expensive, but still offer very good sensitivity. For moving objects, however, their use is very limited.
The frame rate (frames per second) indicates how many frames per second the camera can capture and transmit.
Depending on the selected or possible interface, the required resolution and the selected image data format (8bit to 12bit), the frame rates of cameras range from a few frames per second to well over 1,000 frames per second.
For "flowing" images or streams (e.g. when used in microscopy or in the field of sports analysis), at least 25 frames per second should be achieved, or by now even more frequently 60 frames per second.
In classical factory applications (AOI) the camera is often used triggered and the required frame rate is determined by the cycle time of the machine.
Object speed is the speed by which the detected object moves through the field of view.
For example, in a factory, if you want to analyze objects on a conveyor belt, the object speed is the speed of the conveyor belt.
Rule of thumb: The faster the object moves, the higher the demands on the camera, the light and the entire system setup (trigger behavior, exposure time, etc.)
The interface is the combination of hardware and software used to transmit image data from the camera to the downstream system and control data from the system to the camera.
Different interfaces have different advantages and disadvantages with regard to various characteristics such as throughput/bandwidth, cable length, robustness, price, etc.
For example, GigE is widely used and usually already present in the applications and you can access the widely used RJ45 cables.
With USB 3.0, the simple setup (plug and play) and the higher bandwidth compared to GigE can particularly be emphasized.Interfaces such as CameraLink or CoaXPress require special peripherals on the host side, but in return offer advantages in terms of bandwidth and low CPU load.
Important for the choice of interface is the cable length supported by the interface. Depending on the selected interface, there are clear differences.
With GigE cables, long distances of up to 100 m can be bridged when high-quality cables are used
With USB 3.0, cable lengths beyond 8-10 m can often only be realized with optical solutions, but with short distances the cables are robust, inexpensive and widely used.