Lasers read by shining a beam of light onto a surface and then detecting the light that reflects or scatters back. The pattern or intensity of the reflected light carries information that a sensor can interpret.
One common example, as seen in barcode scanners, illustrates this principle:
Reading Barcodes with a Laser
In systems designed to read barcodes, like those used in retail stores:
- A laser beam is focused onto the barcode.
- The light hits the bars (typically black) and spaces (typically white) of the barcode.
- Black bars absorb more light, while white spaces reflect more light.
- The light reflecting back from the barcode is directed towards a sensor.
According to the provided information:
The laser beam in a barcode scanner is focused on the barcode. Reflecting back to a sensor that reads the code.
The sensor detects the varying pattern of light reflection as the laser scans across the barcode. This pattern corresponds directly to the sequence of bars and spaces.
How the Sensor Interprets the Reflection
The sensor converts the incoming light (photons) into electrical signals. Brighter reflections from the white spaces generate stronger signals than the weaker reflections from the black bars. This creates a waveform representing the barcode pattern. Digital processing circuits then decode this waveform back into the numerical or alphabetical information stored in the barcode.
Other Ways Lasers Read
While barcode scanning is one prominent use, lasers are also fundamental to reading data from various optical media:
- CDs, DVDs, and Blu-ray Discs: Lasers read data stored as microscopic pits and lands (flat areas) on the disc surface. The laser beam reflects differently off the lands compared to the pits. A sensor detects these changes in reflection as the laser tracks across the spiral data path.
- Optical Character Recognition (OCR): In some advanced scanning systems, lasers can be used in conjunction with cameras to scan text or images, though typically laser is more about the scanning mechanism or focus rather than direct reading of character shapes like in barcodes.
In essence, whether reading simple patterns like barcodes or complex data on discs, the core principle involves directing a laser onto a surface and analyzing the way the light interacts with and reflects off that surface.
