Look a little closer
See the mechanism
A full-width optical strip travels along the page
Read the diagram steps
Read an early strip. The CIS module illuminates one strip through the glass. A short lens array directs reflected light to nearby photoreceptors.
Read later strips. The same module moves along the stationary document. Its line of sensors reads across the page while travel supplies the other image dimension.
Original functional schematic; dimensions and motion are exaggerated, not measured. CIS architecture: no folded CCD mirror path. Plan view and optical inset have different scales; RGB illumination is shown conceptually.
Diagram basis: Canon: Scanner subsection, CIS light sources and lens array.
Sources: Canon
Light travels down to a nearby sensor
In the contact image sensor, or CIS, arrangement described by Canon, red, green and blue LEDs illuminate the document. A lens array directs the reflected light to a row of photoreceptors close beneath it. The module spans the scanning width.
Sources: Canon
The second dimension comes from movement
Each position supplies a line across the page. Moving the module along the bed supplies the next line and then the next. The page can remain on the glass while the reading strip progresses from one end to the other.
Sources: Canon
A CCD scanner folds a longer path
Canon also describes CCD scanners that use mirrors and a lens to project a reduced image onto a line sensor. A CIS module keeps the lens array and detectors near the document instead. Both read lines, but their optical paths differ.
Sources: Canon
The thing to remember
The sensor row reads across; movement carries that row along the page.
What this example leaves out
This is a CIS flatbed explanation. It does not describe every scanner optical layout or the separate task of recognizing text.
Sources & further reading
Source access dates are listed below. Manufacturer descriptions and patents support the specific constructions described, not every product.
- Technology Used in Office Multifunction Devices — Scanner ↗
Canon · Retrieved 2026-10-18 · CIS RGB illumination, lens array, full-width photoreceptors, close document spacing and distinction from CCD folded optics.
Read Scanner subsection, HTML lines 235–240. Text read, embedded video not watched. CIS selected for article; Canon overview is not a detailed service drawing of every flatbed scanner.
