Light scanning apparatus and image forming apparatus

A light scanning apparatus comprising:

• a deflecting unit configured to deflect a light flux from a light source to scan a scanned surface in a main scanning direction;
• an incident optical system configured to guide the light flux from the light source to the deflecting unit;
• and
• an imaging optical system configured to guide the light flux deflected by the deflecting unit to the scanned surface,
• wherein, when the deflecting unit rotates at a constant angular velocity, a scanning angle between a principal ray of the light flux immediately after being deflected by the deflecting unit and an optical axis of the imaging optical system is represented by θ, an on-axis image height is represented by Y0, a first outermost off-axis image height on a side opposite to the light source with respect to the optical axis of the imaging optical system in a main scanning cross section is represented by Ymax−, a focal distance of the imaging optical system in the main scanning cross section is represented by ft, and a distance between a rear-side principal plane of the imaging optical system and the scanned surface on an optical path of a principal ray of the light flux that travels to the on-axis image height is represented by Sk, the following conditions are satisfied:
• 0.6
• ≤
• (
• dY
• max
• -
• /
• d
• ⁢
• θ
• )
• /
• (
• dY
• 0
• /
• d
• ⁢
• θ
• )
• ≤
• 0.98
• ;
• ⁢
• 0.5
• <
• Sk
• /
• ft
• <
• 1.
• .