Patent ID: 7471471

Claim:
A refractive optical unit comprising: a reflective optical element that reflects a light ray incoming from a subject along a first optical axis into a direction along a second optical axis intersecting with the first optical axis, the light ray traveling along the second optical axis to form an image of the subject on an image plane; a housing having an opening; a plurality of lens groups housed in the housing; a lens holder that holds one of the plurality of lens groups disposed between the reflective optical element and the image plane, wherein the lens holder has an adjusting unit protruding from the opening of the housing, and a supporting-point section located in a position opposite to the adjusting unit with reference to the one of the plurality of lens groups, the supporting-point section having an elongate hole; and a guide rod that penetrates through the elongate hole and holds part of the plurality of lens groups freely moving along the second optical axis; wherein before the lens holder is fixed in the housing, the one of the plurality of lens groups held in the lens holder can be adjusted by being parallel moved lengthwise of the elongate hole and by being rotated about the guide rod.