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: A guiding fixation method applied to an eye examination device is disclosed. The eye examination device at least includes a first default light source and a second default light source. The guiding fixation method includes steps of: (a) disposing at least one dummy light source between the first default light source and the second default light source; (b) when a distance between the eye examination device and an eye changes, the dummy light source emitting light to guide the eye to gaze at it; (c) when the distance between the eye examination device and the eye stops changing, switching to the first default light source and/or the second default light source to emit light to guide the eye to gaze at it.

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: A simplified and cost-effective three-axis positioning device and method for ophthalmic examination instrument is disclosed. The three-axis positioning device includes an illuminating optical path for projecting light to illuminate an examinee's fundus; an imaging optical path including an objective lens for receiving the examinee's fundus image and light reflected from the examinee's cornea and eye-lens; a software-based alignment module for determining intensity and position of the reflected light on the fundus image to generate auxiliary positioning information; and an image displaying unit for showing the fundus image, the reflected light, and the auxiliary positioning information. From the intensity and position of the reflected light, x-, y- and z-axis relative positions between the examinee's pupil and the objective lens are obtained. An examiner adjusts the relative positions in three axes until they fall within an allowable deviation range, and a clear fundus image can be obtained.