Optics & Optical Coatings
Guide
Laser Safety
Laser light irradiating into the eyes could cause serious disability that leads to blindness.
For this reason, the Ministry of Health, Labor and Welfare issued a directive “Preventive Measures against Disabilities Caused by Laser Light” for laser users and manufacturers. Laser users must confirm with the safety managers of their businesses or organizations. Safety standards or safety measures vary depending on the businesses or organizations. JIS C 6802 specifies the classes of laser products. According to the specification, laser products have a label of the corresponding laser class. JIS defines staged preventive measures for users according to the classification.
When purchasing or using a laser, make sure to check the class of the laser, and use upon understanding the risk.
Laser Safety Glasses
Laser safety glasses to be used are predetermined for each laser.
If you use glasses not compatible with the wavelength of the laser to be used, you cannot get protection and it is very dangerous.
Select the laser safety glasses appropriate for the wavelength of the laser to be used.
Handling of Optics
Some optics split light into multiple beams.
(Glan-Thompson prism, PBS, beamspliter, etc.)
When using these optics, terminate all divided beams safely.
Also, optics having a shape like a prism may split a beam in an unexpected direction.
Make sure to check the all circumferences of a prism, and safely handle stray light.
Installation of Optical Systems
When installing an optical system, the desired height of laser beam is said to be higher than the eye level of standing workers or lower than the eye level of seated workers.Installing a fire-retardant beam enclosure around optical paths is also effective to prevent unnecessary laser exposure.
Laser Installation Environment
To prevent laser beams from reaching outside of an experiment space, covering the experiment space with a darkroom is very effective as a safety measure.
A darkroom can also be a partition of a laser controlled area to limit entrance to only authorized people.
In addition, it can eliminate the influence of disturbance light from an optical experiment, which is effective when performing optical adjustment with weak light.
Handling of Optics
Optics has a limited life span and degradation starts from the moment the package is opened.
Scratches, dirt or dust will accumulate on its surface after lengthy usage and will cause light to scatter or diffract and with the high possibility of poor optical performance.
The durability of optics will change depending on the purpose of experiment and usage environment, but generally they can be used for two to three years.
Handling
Handling of optics requires good care and understanding to prevent surface scratches or dirt. Importantly, do not touch the polished surface.
Lightly hold the ground surface or its edge.
When handling optics, it is good practice to use finger sacks.
When fixing an optic in a holder, do not tighten the optic retaining screw too hard unless for special occasions such as transportation.
Tightening the screw too hard may break the optic or significantly deteriorate the performance of the optic.
Lightly tighten the screw so that the optic does not move.
If the optic retaining screw might get loose due to vibration or the like, we recommend adhering the optic to the holder, or fastening the screw with screw locking glue.
Cleaning
Should an optical component get dusty or dirty, first check if the condition permits cleaning.
Cleaning optics with paper on Gold and Aluminium coating without protective coating is not recommended as it will cause scratches.
As for Dielectric multi-layer coating with protective coating, it is possible but we recommend cleaning to its minimum to avoid risk of scratches.
When wiping optics, always remove them from the holder for effective cleaning.
Wiping an optic in a holder is very difficult and requires experience.
- Prepare several lens papers*1, alcohol (ethanol, methanol, etc.), finger sacks (powder-free type if available), and air blower*2
- Put finger sacks on the fingers of both hands, and wipe off dirt from the finger sacks using paper moistened with alcohol. Then, fold a lens paper into a strip of 3 to 4cm width.
- With the non-dominant hand, hold the edge of the optic as shown in the picture.
- Moisten the folded lens paper lightly with alcohol, and fold it so that it tucks into the faces of the optic.
- Hold the center of the optic with the lens paper, and rotate the optic using the fingers of the non-dominant hand.
- Gradually move the lens paper from the center of the optic toward the edge, and when it reaches the edge, slowly relax the fingers holding the paper, and remove the paper from the optic.
- Hold the surface of the optic against the light to check cleanliness.
Use the air blower to blow off fine dust on the surface of the optic. - If there is still dirt or traces of wiping, change the lens paper, and wipe the optic again with the same procedure.
After finished wiping (change to) Upon finishing the wiping process, keep in a powder paper or special plastic case.
The art of wiping optics is to do it lightly with constant pressure.
*1 Lens Paper (SLP-2) / *2 Air Blower (DOP)
Cleaning
Optics are very stable in our general environment, but if kept in a location with high temperature and humidity for long periods, its surface may get cloudy and mold may also develop on the optics if left unattended. When optics is not being used, keep them in a dry container.
For storage of large optics and optical devices, use a Dry-Cabi®*3.
Ensure the power is on for optimum performance.
In addition, when storing an optic just purchased, we recommend storing it after taking it out from the package.
*3 Dry-Cabi®*3 (H-D-M2)
Check the color of silica gel periodically, and when the color becomes reddish, replace with new silica gel.
Use of a transparent lunch box is convenient because you can check the color of silica gel without opening the cover.
You can reuse the reddish silica gel if you dry it in an oven.
If dust is on the surface of an optic and you irradiate the surface with a strong laser, the dust will burn and the stain caused might not be removed from the optic surface.
For this reason, we recommend the use of a cover to prevent dust from adhering on optical systems when they are not used.
Just before using an optical system, we also recommend that you remove dust from optics using an air blower or by cleaning.