• Laser
• Drawing frequency
• Diode laser (semiconductor laser)
• Divergence
• Corner delay
• Galvanometer-Scanner (Galvos)
• Helium-Neon-Laser (HeNe)
• Coherence
• Optical fibres
• Luminance
• Position Resolution
• Protocol
• Retro-reflectors
• Scanner
• Watt/ Milliwatt
• Wavelength
• Livetime

The word "LASER" is an abbreviation for "Light amplification by stimulated emission of radiation". A laser is a device that produces coherent light. A line laser generates an exact, straight line for long distances with a very intense colour. In the beginning line lasers were made with gas tubes (Helium-Neon lasers) that was stimulated by high-voltage. Nowadays, lasers use semiconductor laser diodes for generating their light. The used gas or other medium determines the corresponding colour of the laser light (usually red or green).

The drawing frequency specifies the frame repetition rate of an image per second that is generated by a 2D-projector. The continuous repetition is necessary because the scanner beam itself is only a point and appears only as an outline if the same picture is repeatedly drawn. The laser beam will therefore draw the contour several times per second (at least 25 times) thereby producing the impression of a steady image. A higher drawing frequency will give a more quiet, steady impression. Forcing higher beam travel speeds, however, may result in softened edges and loss of precision.

The small motors moving the mirrors of the 2D-projector and repeating the same figure x times per second meet their upper limit at a frequency of about 80 Hz (i.e. 80 repetitions of the same image per second), which is also visible in a loss of precision (softened edges of the image, overshoots). The drawing frequency has to be accordingly adjusted, if large or very complex figures are projected, as the laser beam has to cover large distances or change directions a lot of times.

There are two parameters for adjusting the drawing frequency at our 2D-projector CPS, the "drawing frequency" and the "slow down length". As explained, the "drawing frequency" sets the maximal frequency with which the scanner projects the figures. The parameter "slow down length" automatically decreases the drawing frequency if a certain total line length (i.e. the size of the figure) is exceeded. Again, the shorter the total line length, the faster is the repetition of the scanned figure and the better is the picture quality for the user.

Diode lasers are semiconductors similar to an LED (light-emitting diode) but which produce coherent light. Diode lasers are small and efficient, which has led to their use in compact disc players, pen-type laser pointers and line projectors. Diode lasers are significantly smaller and lighter than Helium-Neon lasers and don't have any fragile parts. Therefore, the diode modules are unaffected by great accelerations, mechanical shocks and vibrations. Laser diodes can be switched on and off as often as desired.

An objective measure of the amount that a laser beam spreads as it leaves the laser head. High divergence produces larger spot sizes, which is undesired. Divergence can be a problem when the throw is long. Arrangements of lenses are usually used to minimise divergence in these cases.

CPS generates figures by repeating a contour with the laser beam over and over again. In order to get a high image quality the laser beam has to travel as fast as possible. However, corners become soft edges at higher speeds, i.e. to have sharp, crisp corners, the speed of the laser beam has to be drastically reduced before reaching them. Lower speeds mean lower drawing frequency and thus a decreased image quality. That is why each 2D-projection is a compromise between sharp corners (high value for corner delay = little time for drawing the rest of the picture) and a high drawing frequency (low value for corner delay = more time for drawing the rest of the picture). The user or the fitter decides how to solve this compromise for their application in order to receive the best possible image quality.

A galvanometer is a precise limited excursion motor, whose torque is directly proportional to the current. When current is applied the shaft of the galvos rotates through part of a circle. When current is removed, the shaft returns to the rest position. Strictly speaking, the galvos is the motor device only while a scanner includes the galvos, mirror mount and mirror.
Two scanners are needed to draw laser graphics. The scanners are arranged so the beam reflects first off one mirror (from the X-axis galvos), then off the other (from the Y-axis galvos). The first mirror moves the beam horizontally, the second moves it vertically. This arrangement means the scanners can position the beam anywhere within a square area.

A laser which contains a glass tube filled with a Helium-Neon gas mixture. Most produce red-orange light having a wavelength of 632.8 nanometers. "He-Ne's" are low powered, in the 0.5 to 50 milliwatt range. Most run on 110 or 220 volts, come with built-in power supplies and need no special cooling. Helium-Neon lasers are the most common type of gas lasers but are slowly replaced by semiconductor lasers because they are relatively large and heavy, are mechanically fragile because of their glass tube and need high-voltage for operation. A Helium-Neon laser should not be switched on and off too often as this leads to a drastic decrease in its lifetime (due to high strain on the high-voltage power supply).

A laser produces coherent light while conventional light sources produce incoherent light. Coherent light waves all travel the same direction (spatial coherence) at the same frequency and in phase (temporal coherence). This gives rise to the very narrow beam and intense, pure light that characterises lasers.

Operating the 2D-projector CPS in a surrounding of strong magnetic or electric interference fields, optical fibres should be used for data transmission instead of usual electric wires since these can transmit interferences as proper signals. Optical fibres are not effected by such negative influences and are therefore ideal for signal transmission in strong magnetic or electric interference fields. Signal transmission is not conducted electronically but optically via glass fibres.

A subjective measure of how brightness is perceived by the human eye. It depends not only on brightness of the light but also on the wavelength. Two lasers can be equal in brightness but a green beam has a higher luminance than red since the eye is more sensitive to green light.

The resolution tells you, in how many parts you can divide a picture. The CPS has a resolution of 65536 (16 bit), meaning you can project a separate point every 1mm onto a wall of 65m length or 65536 parallel and separate lines side by side. As a digital device, CPS can only project lines or points on one of these 65536 positions; a projection on the spaces in between these positions is not possible. Moving from left to right the laser point actually jumps from one position to the other instead of continuously covering the whole distance like in an analogue device.

The protocol is the type of communication between external software (e.g. the CNC machine) and our scanner. The communication of two devices with feed-back is called handshake. Operating without handshake means that information can only be transmitted in one direction without knowing whether the other system can receive this information or not. There are two different types of handshake: hardware handshake with a separate cable to send a signal in case the corresponding device cannot receive information, and software handshake, where this signal transmission is sent via the general communication line. The types of handshakes are standardised (protocol): software handshake uses "Xon/Xoff", hardware handshake uses "CTS/DTS".

New CPS systems are only delivered with retro-reflectors which replace the infrared drift sensors with cables. These are two little light reflectors (stickers) with the ability to reflect a light beam back the same direction it came. Moving across such a retro-reflector, the laser beam is reflected directly back to the scanner. The system detects the actual position of the laser beam and can adjust any inaccuracies due to thermal drift. The advantages of retro-reflectors are that they are flat, that they need only very little space (Ø 10 mm) and that there is no cable.

Scanners are engines moving a beam back and forth. In the laser field, a "scanner" means a galvanometer that turns a driving shaft a certain angle back and forth instead of continuously turning it around in the same direction. A small mirror (about 5x8mm) is fixed on the shaft. Two scanners are needed to draw laser graphics. Scanners are arranged so the beam reflects first off one mirror (from the X-axis galvos), then off the other (from the Y-axis galvos). The first mirror moves the beam horizontally, the second moves it vertically. This arrangement means scanners can position the beam anywhere within a square area.
Outlining the same contour repeatedly at a high speed, the illusion of a single standing image is generated. However, due to the net weight of the mirrors a scanner is limited to a certain speed, up to which it still works accurately. Complex scanner amplifiers are used to obtain the best projection quality.

An objective measure of power which is named after the inventor of the steam engine - James Watt (1736-1819).
In the laser field, it usually refers to the optical output power, or strength, of a laser beam. Large light show lasers are generally in the 1 to 20 watt range. Watts are also used in a more conventional sense, to measure electricity used by a laser. For example, a 10 W (optical) argon laser consumes around 10,000 W of electricity.

This describes the distance in electromagnetic waves from the crest of one wave to the next. In the laser industry, wavelength is important because it determines the perceived colour of light. Visible light has wavelengths extending from about 700 nanometers (red) through orange (~600 nm), yellow (~580 nm), green (~550 nm), blue (~450 nm) and violet (~400 nm). Z-LASER uses wavelength in the red (635nm) and green (532nm) colour range.