Evening show


1. Do I need a licence to use a laser in theUK?
No, you can use any size laser without the need for any form of licence. The only thing you need to make sure of is that the laser projector has all the necessary safety features on it and it is used responsibly, following all Health and Safety Guidelines and specifically those detailed in the Health and Safety Executive's HSG95 "The radiation safety of lasers used for display purposes" document. BEWARE of disco shops that say you need a laser licence for larger power laser systems - this is completely FALSE and most probably a sales pitch to sell you what they have in store, also to put you off going to a specialist laser company.

2. What is the HSG95 document and where can I get hold of a copy?
It is a guidance notice published by the Health and Safety Executive. It explains the main points to take into account when using a laser in a public place. Please click this link HSG95 and search under book reference ISBN: 0717606910 to obtain your own copy.

3. Do I need to prepare an installation record for every show I perform?
It is wise to keep and have to hand written documentation of the laser system.

4. Can anybody operate a laser?
Only people with a knowledge of how to competently operate the laser system, and know what safety measures need to be considered should operate a laser display system. When you purchase a system, the company you purchase from needs to advise you on how to install and operate the system, and advise on safety issues.

5. Why does a laser system need to have a key?
The Key Switch is there to prevent unauthorised people from using the laser.

6. Can the laser be left running unattended?
The types of lasers used for laser shows should have someone in attendance, monitoring the show, at all times the laser is operational.

7. What does the term "divergence" mean?
Divergence is the term used to describe how quickly a laser beam spreads out. The unit of measurement is normally expressed in terms of milli-radians (mr). The smaller the number the less the beam spreads out.

8. What does the term "wavelength" mean?
Wavelength is used to describe what frequency(s) of laser radiation is emitted from the laser system. If the wavelengths are in the 400nm to 700nm range, humans can detect different wavelengths as being different colours. Common examples are 532nm for DPSS green lasers, and 630nm for red diodes.

9. What does irradiance mean?
Irradiance is the term used to describe the density of laser power per unit area. Basically it is the power of the beam divided by the area that it covers. As the beam extends further from the projector, the cross-sectional area of the beam increases because of the divergence of the beam. The increase in area, causes the irradiance (power density) to decrease. This is why it is safer to view laser beams over a longer distance. The units for irradiance is watts per square meter (wm-²).

10. What does Maximum Permissible Exposure or MPE mean?
The Maximum Permissible Exposure level or MPE is the scientifically researched threshold whereby the laser radiation exceeds safe levels, and would cause harm to human tissue. There are two main MPE levels, one for skin and one eyes. As eyes are far more susceptible to damage and require less radiation to cause damage, in light show applications the MPE levels for the eye are the most important values to consider. The Laser Safety Standard 60825, and HSG95 have tables in them which detail the applicable MPE levels for the various situation that can occur in laser light show use.

11. What harm can a laser cause to the human eye?
It depends upon the length of the exposure and how intense the laser beam is. In severe circumstances it can cause a complete loss of vision to the central part of your vision, which is used to pick out detail. It's fairly random as to how much and to what extent the damage occurs, which is dependant upon how quickly the eye reacts, and how powerful the beam entering the eye was. If a laser beam is in excess of the MPE the chances of sustaining an injury are increased. The injury may may go unnoticed if it hits part of the eye's peripheral vision. However if a hit is taken in the main part of the eye's vision (the fovea) the person may experience little blind spots in their vision, making it difficult to read text for example. IMPORTANT: Any damage caused to the eye's retina is permanent.

12. Is there a test I can do to check my eyesight?
If you are working with lasers regularly you should have your eyesight checked by an ophthalmologist, who will be able to analyse the eye's retina, and check for damage. There is a simple test you can perform to get an idea of if you have any problems with your eyesight (Amsler Grid vision test page). Of course, this test should not be used as a substitute to seeing a qualified specialist if you want to have your eyesight tested.

13. Is is okay to point single beams of light above the audience?
Yes, as long as it is not reflected back down into the audience, and is terminated correctly, it is safe to project virtually any laser effect 3m above and audience.

14. Is it okay to point beams of light into the audience?
No, only if the beam's irradiance is below that of the MPE can it be projected into the audience. Most of the time, with the lasers that are used for laser displays, the energy of a single beam is way in excess of the MPE, and should not be directed into the audience. If more than 1mW can enter the eye then the beam is unsafe.

15. Are there any dangers from effects scanned above the audience?
Laser effects projected 3 meters above the audience are eye safe. A survey should be taken to assess the likelihood of any reflective surfaces (such as high windows, chrome bars etc) bouncing stray beams back down into the audience.



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