How To Select A Digital Area Scan Camera Ron Bryan
1st Vision, Inc.
The choice of a digital area scan camera encompasses many questions about your application and requirements. This guide is designed to help you in your choice
How to select a digital area scan camera
Resolution Area scan cameras generate digital images comprised of pixels which correspond to some area that the camera “sees”. Since a pixel is the smallest individual unit that the camera can detect, this is the baseline for selecting camera resolution. A general rule is Area to be viewed/size of minimum object = Resolution An example of this is if the camera has to view an area 10” wide and you need to be able to detect a feature 1/10”, your required camera resolution would be at least 10”/.01 = 1000 pixels
How to select a digital area scan camera
Frame Rate How often a camera generates an image is called frame rate. If you need to snap an image of an event which occurs 20 times/second, you will need a camera with a minimum frame rate of 20 frames/second
How to select a digital area scan camera
Moving or Stationary? If the camera needs to stop motion (imaging a moving object or the camera is moving) defines much about the sensor type required. Interlaced (CCD) or Rolling Shutter (CMOS) sensors expose (acquire light) over parts of the sensor at various times, so when imaging moving objects, blurring can occur in the images. If you do need to stop motion Progressive (CCD) or Global Shutter (CMOS) sensors are preferred How to select a digital area scan camera
Spectral Response What wavelength of the light spectrum a camera can detect refers to it’s spectral response. Some applications require the camera to see outside of the visible (to humans) range. For some applications imaging the human eye, the eye is illuminated with near IR illumination, which doesn’t bother the human. In this case the camera must be sensitive in the near IR to be effective How to select a digital area scan camera
Sensitivity Camera sensitivity defines how much light is needed to generate images. The following conditions often require high sensitivity cameras: - High magnification - Stop motion requiring fast shutter times - Dark environments How to select a digital area scan camera
Image Quality An in depth analysis of this topic would take up much more than one slide, but suffice to say that CCD sensors continue to generate higher quality images than CMOS. For many applications, CMOS will be more than good enough. This choice really depends upon your particular application requirements How to select a digital area scan camera
Camera Output Format Many camera output choices now exist with the most popular being Camera Link, USB2.0 and Firewire (IEEE1394A/B). Each one has its own set of tradeoffs, a summary of which is as follows:
How to select a digital area scan camera
Camera LinkTM - Highest data rates available. Requires special frame grabber hardware - Doesn’t provide camera power - Deterministic image transfer and signaling - Image transfer is via DMA from Frame Grabber - Highest overall system cost - Sustained data rates upto ~1Gb/second How to select a digital area scan camera
USB2.0 -
Simplest to use. Very available Camera is typically powered from USB Image transfer is non deterministic Image transfer is via programmed I/O (CPU copies data from camera into PC memory) - Sustained data rates upto ~40Mb/second How to select a digital area scan camera
Firewire (IEEE1394A) -
Easy to use. Quite available Camera is typically powered from Firewire Image transfer is deterministic Image transfer is via DMA Sustained data rates upto ~40Mb/second
How to select a digital area scan camera
Summary Selecting the right camera for your application requires thinking about all of the above topics before selecting a camera
