Patent ID: 7566131

Claim:
A refraction measuring instrument comprising: measuring means that has a light source for emitting a measurement light beam to an eye to be examined and performs objective measurement on refraction of the eye to be examined based on reflection light of the measurement light beam emitted from the light source, which is reflected on the eye to be examined; and an optical system, to which the light source and the measuring means are added, for simultaneously guiding the measurement light beam emitted from the light source and visible light incident thereon from an outside to the eye to be examined, wherein the optical system comprises a free-form-surface prism having a surface for combining the optical axis of the measurement light beam with the optical axis of the visible light by reflection of the measurement light beam and transmission of the visible light, and a deviation angle correcting prism for correcting a deviation angle of the visible light passing through the free-form-surface prism, wherein the light source emits the measurement light beam to be incident on the optical system from the direction different from that of the visible light, wherein the free-form-surface prism reflects the incident measurement light beam inside itself, so that the measurement light beam is incident on the eye to be examined, and reflects the reflection light from the eye to be examined inside itself to the direction different from that of the visible light, in order to output the reflection light to the measurement means, and wherein the measuring means measures the refraction of the eye to be examined while a subject is visually recognizing the outside through the visible light based on the reflection light of the measurement light beam which is guided to the eye to be examined through the optical system and reflected on the eye to be examined.