Appearance
The violet 405 nm laser (whether constructed from GaN or frequency-doubled GaAs laser diodes) is not in fact blue, but appears to the eye as violet, a color for which a human eye has a very limited sensitivity. When pointed at many white objects (such as white paper or white clothes which have been washed in certain washing powders) the visual appearance of the laser dot changes from violet to blue, due actually to fluorescence from brightening dyes.
For display applications which must appear "true blue", a wavelength of 445–450 nm is required. With advances in production, and commercial sales of low-cost laser projectors, 445 nm InGaN laser diodes have dropped in price.
A last challenge in projection laser diodes is related to the construction of a "true green" InGaN laser (around 530 nm). Many companies have demonstrated devices working at only slightly shorter wavelengths: 480–500 nm.
Read more about this topic: Blue Laser
Famous quotes containing the word appearance:
“Look into the world—how often do you behold a sordid wretch, whose straight heart is open to no man’s affliction, taking shelter behind an appearance of piety, and putting on the garb of religion, which none but the merciful and compassionate have a title to wear.”
—Laurence Sterne (1713–1768)
“Never before has a generation of parents faced such awesome competition with the mass media for their children’s attention. While parents tout the virtues of premarital virginity, drug-free living, nonviolent resolution of social conflict, or character over physical appearance, their values are daily challenged by television soaps, rock music lyrics, tabloid headlines, and movie scenes extolling the importance of physical appearance and conformity.”
—Marianne E. Neifert (20th century)
“Do not look on his appearance or on the height of his stature, because I have rejected him; for the LORD does not see as mortals see; they look on the outward appearance, but the LORD looks on the heart.”
—Bible: Hebrew, 1 Samuel 16:7.