Why does astigmatism occur when I wear glasses to look at a panchromatic laser projector?

XLZ451

Member
Recently, some people bought panchromatic laser projection and found that wearing glasses to look at the projector will have color separation, that is, different colors of double shadows, also known as "astigmatism". This article will use the principle of panchromatic laser projection to explain why people wearing glasses will have astigmatism when looking at panchromatic laser projection.

What is the principle of light separation?​


The sunlight will be divided into red, orange, yellow, green, blue and purple seven colors of light after passing through the trigonal prism. The principle is: white light is a complex color light composed of various monochromatic light; the same medium has different refractive indices for different colors of light; different colors of light in the same medium propagate at different speeds.

What is the principle of light separation?

Because the same medium for a variety of monochromatic light refractive index is different, so through the prism, the angle of deflection of each monochromatic light is different. Therefore, white light passing through the prism will separate the monochromatic light, that is, dispersion. This principle can also explain the formation of the rainbow.

The lenses of eyeglasses are usually made of glass or glass resin, and this material also has different refractive indices for different wavelengths of light, thus producing different refraction angles for different wavelengths of light.

Why does astigmatism occur when I wear glasses to look at a panchromatic laser projector?​

Let's take a look at the promotional chart of a panchromatic laser projector, the light source of projection is composed of three beams of red, green and blue laser.

Why does astigmatism occur when I wear glasses to look at a panchromatic laser projector?

We know that the color of the laser is very "brilliant", that is, a single wavelength, the narrow bandwidth of light. But it is almost impossible to have such a single wavelength of light in nature. Monochromatic light in nature is a continuous broad spectrum light compared to laser light.

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The projected white light of the tri-color laser is incident on the lens of the glasses, and these three laser colors produce different fold angles, and because the bandwidth of these three laser colors is very narrow, a large part of the spectrum is missing in the middle, which makes the three laser colors pass through the glasses and produce fold angles without overlapping each other, and therefore produce color separation.

Why does astigmatism occur when I wear glasses to look at a panchromatic laser projector.jpg
There is another reason why color separation is worse if you look at a trichromatic laser projector with your glasses on at an oblique angle. That's because when squinting, the trichromatic laser light is obliquely incident on the lens, the light takes a longer path through the lens, and the color separation is more severe.

Similarly, the deeper the myopia, the thicker the lenses of the glasses will be, and the color separation will be more serious. And if we change the direction to look obliquely, this color separation will also change over with the direction.

Conclusion​

To sum up, people feedback that people who wear glasses will have astigmatism when watching panchromatic laser projection, in fact, the principle is the color separation caused by dispersion. Therefore, for people who do not have good eyesight and want to purchase a laser projector, it may be more suitable to use ALPD laser technology for monochrome laser projectors.

Dangbei laser 4k projector
 

Tinas

New member
I watched the game on Dangbei Mars Pro with my glasses on and there was no astigmatism. so maybe that's the advantage of ALPD technology. And the screen picture is very clear and bright.
 
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