Abstract: An optotype calibration method is disclosed. The optotype calibration method includes steps of: (a) when a first optotype and a second optotype located outside an observable area, moving the observable area from an original position until the first optotype or the second optotype appears in the observable area; (b) adjusting a focus mechanism to make the first optotype and the second optotype close to each other; (c) moving the observable area back to the original position; and (d) repeating the steps (a)˜(c) until the first optotype and the second optotype align with each other.

Abstract: An absorption type near-infrared filter comprising a first multilayer film, a second multilayer film, and an absorption film, wherein in the ultraviolet band, the difference of between the wavelength with the transmittance at 80% of the absorbing film and the wavelength with the reflectivity at 80% of the first multilayer film falls in the range between 25 nm and 37 nm, the difference of between the wavelength with the transmittance at 50% of the absorbing film and the wavelength with the reflectivity at 50% of the first multilayer film falls in the range between 6 nm and 14 nm, and the difference of between the wavelength with the transmittance at 20% of the absorbing film and the wavelength with the reflectivity at 20% of the first multilayer film falls in the range between ?6 nm and 2.5 nm.

Abstract: An absorption type near-infrared filter comprising a first multilayer film, a second multilayer film, and an absorption film, wherein in the ultraviolet band, the difference of between the wavelength with the transmittance at 80% of the absorbing film and the wavelength with the reflectivity at 80% of the first multilayer film falls in the range between 25 nm and 37 nm, the difference of between the wavelength with the transmittance at 50% of the absorbing film and the wavelength with the reflectivity at 50% of the first multilayer film falls in the range between 6 nm and 14 nm, and the difference of between the wavelength with the transmittance at 20% of the absorbing film and the wavelength with the reflectivity at 20% of the first multilayer film falls in the range between ?6 nm and 2.5 nm.

Abstract: An absorption type near-infrared filter comprising a first multilayer film, a second multilayer film, and an absorption film comprising an infrared absorbing dye with a weight percentage between 1% and 3%, wherein in the infrared band, the difference between the wavelength with the transmittance at 80% of the absorption film and the wavelength with the reflectivity at 80% of the first multilayer film ranges between 130 nm and 145 nm; the difference between the wavelength with the transmittance at 50% of the absorption film and the wavelength with the reflectivity at 50% of the first multilayer film ranges between 75 nm and 90 nm; the difference between the wavelength with the transmittance at 20% of the absorption film and the wavelength with the reflectivity at 20% of the first multilayer film ranges between 25 nm and 45 nm.

Abstract: An absorption type near-infrared filter comprising a first multilayer film, a second multilayer film, and an absorption film comprising an infrared absorbing dye with a weight percentage between 1% and 3%, wherein in the infrared band, the difference between the wavelength with the transmittance at 80% of the absorption film and the wavelength with the reflectivity at 80% of the first multilayer film ranges between 130 nm and 145 nm; the difference between the wavelength with the transmittance at 50% of the absorption film and the wavelength with the reflectivity at 50% of the first multilayer film ranges between 75 nm and 90 nm; the difference between the wavelength with the transmittance at 20% of the absorption film and the wavelength with the reflectivity at 20% of the first multilayer film ranges between 25 nm and 45 nm.

Abstract: The present disclosure is related to a filter, which includes a near infrared light filtering substrate, having a near infrared light absorbing dye; an absorbing layer, having a near infrared light absorbing dye and an ultraviolet light absorbing dye, and formed on one surface of the near infrared light filtering substrate; a first multi-layer film, formed on the absorbing layer; and a second multi-layer film, formed on the other surface of the near infrared light filtering substrate.