CCD Cameras

Charge coupled device (CCD) cameras contain light-sensitive silicon chips that detect electrons excited by incoming light. They also contain micro circuitry that transfers a detected signal along a row of discrete picture elements or pixels, scanning the image very rapidly. CCD cameras use two-dimensional CCD arrays with many thousand of pixels. They are often used in machine vision applications.

CCD cameras 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.  Multiple chip color is a method of capturing color in which multiple chips are each dedicated to capturing part of the color image, such as one color, and the results are combined to generate the full color image.  They typically employ color separation devices such as beamsplitters rather than having integral filters on the sensors.

Important performance specifications to consider when searching for CCD cameras include horizontal resolution, maximum frame rate, shutter speed, sensitivity, and signal-to-noise ratio.  Horizontal resolution is the maximum number of individual picture elements that can be distinguished in a single scanning line. It is most common to characterize horizontal video resolution corrected for the image aspect ratio, or specify the resolution in the largest circle than can fit in a rectangular image.  Thus, for example a 640 x 480 image would be specified as 480 horizontal lines.  Maximum frame rates for CCD cameras are the number of frames that can be captured per unit time, typically frames per second.  Shutter time is the time of exposure or light collection.  Typically may be set across a wide range.  Sensitivity refers to minimum scene illumination for the CCD camera to produce good image quality.  The standard unit for illuminance is the lux, or lumens per square meter (lm/m²).  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.

Analog video formats used by CCD cameras include NTSC, PAL, SECAM, RS-170, RS-330, and CCIR.  Digital output interfaces common to vision sensors include RS232, RS422, RS485, parallel interfaces, Ethernet, DeviceNet, ARCNET, PROFIBUS, CANbus, Foundation Fieldbus, IEEE 1394 (Firewire), Modem, SCSI, TTL, USB, and radio or wireless.  CCD cameras choices for bits or pixels include 8 bits, 10 bits, 12 bits, 14 bits, or 16 bits.  Color outputs are typically RGB, Y P_bP_r, Y/C (S-video), or composite.

Other parameters to consider when specifying CCD cameras include specialty applications, performance features, physical features, lens mounting, shutter control, sensor specifications, dimensions, and operating environment parameters.

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Part Numbers for CCD Cameras