Light scanning apparatus and image forming apparatus

An apparatus comprising:

• a first deflector configured to deflect a first light flux from a first light source to scan a first surface in a main scanning direction;
• a first imaging optical system which includes a first optical element and a second optical element, and is configured to guide the deflected first light flux to the first surface;
• and
• a first incident optical system which includes a sub-scanning stop configured to restrict a light flux diameter in the sub-scanning direction of a first plurality of light fluxes from the first light source including a plurality of light emitting points, and is configured to cause the first plurality of light fluxes to enter a first deflecting surface of the first deflector,
• wherein, regarding an incident surface and an exit surface of each of the first optical element and the second optical element, when an intersection with an optical axis is set as an origin, an axis parallel to the optical axis is set as an x-axis, an axis perpendicular to the optical axis within a main scanning cross section is set as a y-axis, an axis perpendicular to the optical axis within a sub-scanning cross section is set as a z-axis, an aspherical coefficient is represented by Mmn, a curvature radius within the sub-scanning cross section including the optical axis is represented by r, a variation coefficient is represented by Ei, and shapes within the sub-scanning cross section of the incident surface and the exit surface of each of the first optical element and the second optical element are represented by the following equations:
• x
• =
• z
• 2
• /
• r
• ′
• 1
• +
• (
• 1
• -
• (
• z
• /
• r
• ′
• )
• 2
• )
• 1
• /
• 2
• +
• ∑
• n
• =
• 1
• 8
• ∑
• m
• =
• 0
• 1
• ⁢
• 6
• M
• m
• ⁢
• n
• ⁢
• y
• m
• ⁢
• z
• n
• r
• ′
• =
• r
• ⁡
• (
• 1
• +
• ∑
• i
• =
• 1
• 1
• ⁢
• 6
• E
• i
• ⁢
• y
• i
• )
• in each of the incident surface and the exit surface of the first optical element and each of the incident surface and the exit surface of the second optical element, at least one of values of Mmn is not equal to 0 provided that m is not equal to 0,
• wherein the incident surface and the exit surface of the second optical element have M01 of the same sign, and
• wherein the following inequality is satisfied:
• Ls≤Tc/(βs)2,
• where βs represents a lateral magnification of the first incident optical system within the sub-scanning cross section, Ls represents a distance on the optical axis from the first light source to the sub-scanning stop, and Tc represents a distance from an axial deflecting point of the first deflector to the first surface.