2.11 Pushbroom Scanner

The pushbroom scanner or linear array sensor is a scanner without any mechanical scanning mirror but with a linear array of solid semiconductive elements which enables it to record one line of an image simultaneously, as shown is Figure 2.11.1.

The pushbroom scanner has an optical lens through which a line image is detected simultaneously perpendicular to the flight direction. Though the optical mechanical scanner scans and records mechanically pixel by pixel, the pushbroom scanner scans and records electronically line by line.

Figure 2.11.2 shows an example of the electronic scanning scheme by switching method.

Because pushbroom scanners have no mechanical parts, their mechanical reliability can be very high.

However, there will be some line noise because of sensitivity differences between the detecting elements.

Charge coupled devices, called CCD, are mostly adopted for linear array sensors. Therefore it is sometime called a linear CCD sensor or CCD camera. HRV of SPOT, MESSR of MOS-1, and OPS of JERS-1 are examples of linear CCD sensors as is the Itres CASI airborne system. As an example, MESSR of MOS-1 has 2048 elements with an interval of 14 mm. However CCD with 5,000 - 10,000 detector elements have been developed and available recently made available.


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