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Image Sensing and Acquisition

Prepared by

S.Rohini

Assistant Professor

Depatment of CS & IT

CPA College

Bodinayakanur

CARDAMOM PLANTERS’ ASSOCIATION COLLEGE�(Re-accredited with ‘B’ Grade by NAAC) �Pankajam Nagar, Bodinayakanur - 625 582.�

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Image Sensing and Acquisition

  • Images are generated by the combination of an “illumination” source and the reflection or absorption of energy from that source by the elements of the “scene” being imaged.
  • The illumination may originate from a source of EM energy, such as a radar, infrared, or X-ray system.
  • Image acquisition may be of different types:
    • Single image Sensor
    • Sensor Stripes that may be a linear or circular
    • Array Sensors

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Image Acquisition using Single Sensor

  • Simple idea is photo diode as a sensor.
  • According to the illumination of light, output waveform is generated.
  • Output is proportional to the incident light intensity.
  • Filter is used to improve selectivity

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Line Sensor

Array Sensor

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Image Acquisition using Single Sensor

  • To generate 2-d image, the sensor must have relative displacement in both X- and Y- direction.
  • Sensor is mounted on lead screw, film negative is on drum.
  • A light source is inside the drum.
  • As the light passes through the film, its intensity is modified by the film density before it is captured by the sensor.
  • This "modulation" of the light intensity causes corresponding variations in the sensor voltage, which are converted to image intensity levels by digitization.

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Image Acquisition using Sensor Stripes

  • The strip provides imaging elements in one direction.
  • Motion perpendicular to the strip provides imaging in the other direction, as shown in Fig.
  • This arrangement is used in most flat bed scanners.
  • Sensing devices with 4000 or more in-line sensors are possible.
  • They are used in airborne imaging applications, in which the imaging system is mounted on an aircraft that flies at a constant altitude and speed over the geographical area to be imaged.

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Image Acquisition using Sensor Stripes

  • Sensor strips in a ring configuration are used in medical and industrial imaging to obtain cross-sectional (“slice”) images of 3-D objects.
  • A rotating X-ray source provides illumination, and X-ray sensitive sensors opposite the source collect the energy that passes through the object.
  • This is the basis for medical and industrial computerized axial tomography (CAT) imaging