According to an embodiment, an optical apparatus includes an illumination unit, an imaging unit and a processing unit. The illumination unit emits a first ray having a first wavelength and a second ray having a second wavelength different from the first wavelength to an object. The imaging unit includes a first pixel which receives the first ray emitted to the object and a second pixel which receives the second ray emitted to the object to capture an image based on the first ray received by the first pixel and the second ray received by the second pixel. The processing unit calculates a first ray direction of the first ray and a second ray direction of the second ray based on the image captured by the imaging unit.