1. Field of the Invention
The present invention relates to an optical scanning device, and more particularly to an optical scanning device which scans a radiated optical flux by making use of a predetermined oscillation of a resonance-type deflection element, and an image display device and a retinal scanning display which include such an optical scanning device.
2. Description of the Related Art
With respect to an optical scanning device which has been used as a laser printer device, an image display device or the like conventionally, there has been known an optical scanning device which uses a resonance-type deflection element capable of scanning an optical flux by making use of oscillation.
For example, JP-A-2005-181477 (patent document 1) discloses an image display device which includes an optical scanning device capable of performing scanning on an optical flux radiated from a light source in the high-speed scanning direction (horizontal direction) using the resonance-type deflection element. The optical flux scanned by the resonance-type deflection element is scanned by a deflection element arranged in a succeeding stage in the low-speed scanning direction (vertical direction), and is projected on a retina of an eye thus forming an image on a retina.
Here, it is necessary for this type of optical scanning device to scan optical fluxes such that positions of the optical fluxes corresponding to respective pixels (dots) in the scanning direction of the optical fluxes are arranged at equal intervals. However, when the resonance-type deflection element is used, in radiating the optical fluxes corresponding to the respective pixels at equal intervals from the light source, after scanning the optical fluxes corresponding to the respective pixels using the resonance-type deflection element, the positions of the optical fluxes corresponding to the respective pixels in the scanning direction of the optical fluxes are arranged at non-equal intervals in a sinusoidal shape. In this specification, hereinafter, the explanation will be made on a premise that the pixel implies a minimum unit of an image signal, and particularly implies a minimum unit of a digitalized image signal. That is, a component of the image signal which is read corresponding to each dot is explained as the pixel (pixel signal).
In view of the above, the optical fluxes corresponding to the respective pixels which are arranged at non-equal intervals by scanning using the resonance-type deflection element are optically corrected by an arc sin θ correction lens. However, the conventional optical correction using the arc sin θ correction lens requires an expensive optical system thus pushing up a cost.
To cope with such a drawback, there has been known a method which constitutes an optical scanning device without using the arc sin θ correction lens. That is, this method sets clocks for pixel scanning (dot clocks) to cycles corresponding to the optical scanning directions.
JP-B-5-3947 (Patent document 2) discloses an optical scanning device which includes an oscillator which generates reference clocks, and a first frequency divider which generates position control clocks by dividing the reference clocks, wherein dot clocks are generated based on the position control clocks, and the dot clocks are changed corresponding to scanning speeds of a resonance-type deflection element.