Today, quality control and the desire for absolute safety have contributed to the introduction of numerous sensors in our lives. Optical technologies have played an increasingly important role in this development because they combine the advantages of a small design, reduced production costs, fast measurement speeds, high precision, reliability, and non-contact measurements across large distances.
Simple distance measurement devices and sensors used to measure rooms or calculate distances up to 200 m are now available in well-stocked hardware stores.
Inexpensive laser diodes are usually integrated into these devices. Such laser diodes emit in the visible spectral range and are commonly found in consumer products such as CD and DVD players. Silicon PIN photodiodes are used as receivers.
The Receiver - Avalanche Diodes with Major Advantages
Applying reflectors to the receiver side or using more sensitive receivers increases the range. A low-cost Si avalanche photodiode (APD) can measure distances up to four times that of a PIN diode at the same laser power of the sender. A low-noise, high-end APD achieves distances ten times that of a PIN diode.
Using Powerful Pulsed Lasers in the Sender
Powerful pulsed laser diodes (PLDs) can be used in the sender. These diodes emit in the near infrared range (NIR) typically at a wavelength of 905 nm. This means that, although the beam is not visible and despite high optical peak powers, with adequately small pulse widths, it is easier to achieve eye safety in a system. With the use of special PLDs, this power can amount to up to 400 watts. A few tens of watts suffice to measure distances up to 1 km. Distance measurement devices with these components are used in industry, measurement technology, and entertainment.
Some examples include:
Securing cranes and vehicles at safe distances
- Distance and fluid level measurements in silos or crucibles, even at high temperatures
- Measurement of the position and dimensions of red-hot materials in a steel mill
- Measurement of the height of buildings, trees, and other objects in municipal and agrarian areas
- Measurement of the profile of stone quarries or mining waste heaps
- Sensors for ship docking systems
- Ceilometers make high-resolution detection and distance measurements of clouds and aerosol layers up to 13,000 m possible
- Golfers try to improve their handicap with laser rangefinders
- Hunters measure distances with a sighting telescope