For a thin double convex lens, refraction acts to focus all parallel rays to a point referred to as the principal focal point. The distance from the lens to that point is the principal focal length f of the lens. For a double concave lens where the rays are diverged, the principal focal length is the distance at which the back-projected rays would come together and it is given a negative sign. The lens strength in diopters is defined as the inverse of the focal length in meters. For a thick lens made from spherical surfaces, the focal distance will differ for different rays, and this change is called spherical aberration. The focal length for different wavelengths will also differ slightly, and this is called chromatic aberration.

Lenses and focal lengthchart

The most important characteristic of a lens is its principal focal length, or its inverse which is called the lens strength or lens "power". Optometrists usually prescribe corrective lenses in terms of the lens power in diopters. The lens power is the inverse of the focal length in meters: the physical unit for lens power is 1/meter which is called diopter.

La Fenêtre de Sécurité Laser Bleue a été une excellente addition à ma configuration laser. Avec un indice de densité optique de 6+ et une compatibilité avec ma diode laser 450 nm 1,6W PL TB450B, je me sens en sécurité en travaillant sur mes projets. Ces fenêtres offrent une protection fiable contre la radiation laser réfléchie de manière diffuse. Cependant, je me souviens toujours qu'elles sont une mesure de sécurité supplémentaire et non le seul moyen de protection. La sécurité ne doit jamais être compromise lors de la manipulation des lasers. De plus, il est bon de noter la tolérance dimensionnelle pour la fenêtre. Globalement, un excellent produit !

Focal lengthof lens formula

This shows parallel beams from two helium-neon lasers converging to the principal focal point of a 30 cm double convex lens. The rays then enter a diverging lens of focal length -10cm on the right. The laser beams were made visible with a spray can of artificial smoke.

The Blue Laser Windows can reduce the risk of light entering the eyes from diffusely reflected laser radiation. With an optical density (OD) rating of 6+ in the 190 nm to 540 nm range, they provide reliable protection. These windows are CE Rated and offer a 50% Visible Light Transmission.

Lenses and focal lengthcomparison

However, it is important to emphasize that these laser windows should not be relied upon as the sole means of eye protection against direct or indirect exposure to laser beams. They serve as an additional safety measure for diffusely scattered light. It is crucial to implement other precautionary measures, receive proper training, and adhere to established safe practices when working with lasers.

Please be aware that the window dimensions have a tolerance of ± 3 mm for both width and length. Additionally, minor edge chips may be present, not exceeding 3 mm in size.

These laser windows can help reduce the probability of light entering the user’s eye from a diffusely backscattered laser light. This product is rated at OD 6+ over the range of 190 to 540 nm, blocking deep ultraviolet to green including violet and blue light.

This website prioritizes your privacy, and we respect that by using only our own cookies. None of your data or cookies are shared outside our servers. Additionally, we use these cookies to ensure that the site runs faster and performs efficiently for a better user experience.

The principal focal length of a lens is determined by the index of refraction of the glass, the radii of curvature of the surfaces, and the medium in which the lens resides. It can be calculated from the lens-maker's formula for thin lenses.