Frame Grabbers Information
Frame grabbers are image processing computer boards that capture and store image data for industrial applications such as quality control. Frame grabbers can operate in monochrome or color. Monochrome is black and white, or grayscale; the image is presented in black, white, and grayscale. The range of colors is generated with varying combinations of different discrete colors. One common technique is sensing the red, green, and blue components (RGB) and combining them to create a wide spectrum of colors.
For frame grabbers that can handle camera outputs in an analog format, the analog camera specifications are important to consider. The input pixel acquisition depth is important to consider. The pixel depth refers to the number of bits in each pixel. Increasing the pixel depth increases the amount of detail that will be reproduced in the scanned image. Acquisition formats include RS170, CCIR, RS330, RS422, NTSC, Y/C, PAL, and RGB. For frame grabbers that can handle camera outputs in digital format, the input pixel acquisition depth is important to consider.
Common acquisition features for frame grabbers include:
- digitization accuracy S/N
- number of video inputs
- number of input lookup tables
- on-board video memory
- overlay buffer memory
- trigger input
- high resolution cameras
- line scan capture
- gain scaling
- offset scaling
Signal-to-Noise ratio is defined as the peak-to-peak camera signal output current to the RMS noise in the output current. This ratio represents how prevalent the noise component of a signal, and thus the image uncertainty, is in the total signal. Noise sources include sensor "dark current," electromagnetic interference, and any other spurious non-image signal elements. Higher SNR numbers represent less image degradation from noise. The number of video inputs is the number of video signals the frame grabber can handle simultaneously. High-resolution cameras support camera inputs greater than 1,000 x 1,000 pixels.
Output choices for frame grabbers include RS170, CCIR, RS330, RS422, NTSC, Y/C, RGB, PAL, SVGA, and VGA. Common display features include single screen (pass through) operation or dual screen operation, hardware image processor, hardware scaling, hardware region or interest, strobe output, and acceptance or generation of video timing signals. Computer bus interface choices for frame grabbers include PCSI bus, ISA/EISA bus, VESA/Local bus, PC card/PCMCIA, Mac-Nubus, Mac-PCI, Sun-Sbus, STD bus, Multibus, VME, and VXI/MXI. An important environmental parameter to consider is the operating temperature.
Chris Whytehead / CC BY-SA 3.0