Optical scanner configured so a principal ray of an incident beam from a light source to a deflector and a principal ray of a scanning beam from the deflector to a scanned surface travel on same side (or opposite sides) of an optical axis of an optical element(s) having transmissive surfaces both convex (or both concave) toward the deflector in sub-scanning section respectively, and image forming apparatus using the same

An optical scanner comprising:

• a light source device;
• a deflecting device;
• a first optical system configured to guide an incident beam emitted from the light source device to the deflecting device;
• and
• a second optical system configured to guide a scanning beam deflected by the deflecting device to a surface to be scanned,
• the incident beam being a beam following a light path between the light source device and the deflecting device, and
• the scanning beam being a beam following a light path between the deflecting device and the surface to be scanned,
• wherein the second optical system includes at least one imaging optical element,
• wherein the incident beam passes through the at least one imaging optical element constituting the second optical system, and is obliquely incident on a deflecting surface of the deflecting device in a sub-scanning section,
• wherein both the principal ray of the incident beam and the principal ray of the scanning beam travels on the opposite side with each other with respect to the optical axis of the at least one imaging optical element constituting the second optical system through which the incident beam passes in a sub-scanning section, and
• wherein both the entrance surface and the exit surface of the at least one imaging optical element constituting the second optical system through which the incident beam passes are concave toward the deflecting device in the sub-scanning section,
• wherein the at least one imaging optical element is tilted in the sub-scanning section.

An optical scanner comprising:

• a light source device;
• a deflecting device;
• a first optical system configured to guide an incident beam emitted from the light source device to the deflecting device;
• and
• a second optical system configured to guide a scanning beam deflected by the deflecting device to a surface to be scanned,
• the incident beam being a beam following a light path between the light source device and the deflecting device, and
• the scanning beam being a beam following a light path between the deflecting device and the surface to be scanned,
• wherein the second optical system includes at least one imaging optical element,
• wherein the incident beam passes through the at least one imaging optical element constituting the second optical system, and is obliquely incident on a deflecting surface of the deflecting device in a sub-scanning section,
• wherein both the principal ray of the incident beam and the principal ray of the scanning beam travels on the opposite side with each other with respect to the optical axis of the at least one imaging optical element constituting the second optical system through which the incident beam passes in a sub-scanning section, and
• wherein both the entrance surface and the exit surface of the at least one imaging optical element constituting the second optical system through which the incident beam passes are concave toward the deflecting device in the sub-scanning section,
• wherein the at least one imaging optical element is a first imaging optical element and a second imaging optical element, wherein the first imaging optical element is tilted a first angle in the sub-scanning section, and wherein the second imaging optical element is tilted a second angle in the sub-scanning section.