Scanning optical device
View Patent ↗A scanning optical device includes at least one light source unit for emitting a light beam, a first deflector for deflecting the emitted light beam in an auxiliary scanning direction, a condensing optical system for generating an intermediate image of the light beam deflected by the first deflector, a collecting optical system for condensing a light beam diverged from the generated intermediate image, a second deflector for deflecting the condensed light beam in a main-scanning direction, and a scanning optical system for scanning the surface to be scanned with the light beam deflected by the second deflector. The condensing optical system has an f-θ characteristic, the collecting optical system has an f-sin θ characteristic, and the scanning optical system has an f-sin θ characteristic.
1. An scanning optical device that scans a light beam in two directions, the two directions being a main scanning direction and an auxiliary scanning direction, the optical scanning device comprising:
at least one light source unit that emits the light beam;
a first deflector that deflects the emitted light beam in the auxiliary scanning direction;
a condensing optical system that generates an intermediate image of the light beam deflected by the first deflector;
a collecting optical system that collects each chief ray corresponding each intermediate image formed by the condensing optical system;
a second deflector that deflects the light beam collected by the collecting optical system in the main scanning direction; and
a scanning optical system that scans the light beam, the light beam being deflected by the second deflector, on a surface to be scanned,
wherein the condensing optical system is configured to have an f-θ characteristic, the collecting optical system is configured to have an f-sin θ characteristic, and the scanning optical system is configured to have an f-sin θ characteristic, respectively.
2. The scanning optical device according to claim 1 , wherein, when the scanning optical device is configured to have a plurality of light source units, the plurality of light source units are arranged in line in at least one of the main scanning direction and the auxiliary scanning direction.
3. The scanning optical device according to claim 2 , wherein, when the plurality of light source units are configured such that three or more the light source units are arranged in line in the auxiliary scanning direction, the plurality of light source units are arranged such that respective angles between optical axes of the neighboring two light source units are equal.
4. The scanning optical system according to claim 1 , wherein, when the light source unit is arranged such that an optical axis of the light source unit makes an angle A with a central axis of the scanning optical system on a main scanning plane including the central axis of the scanning optical device and the main scanning direction, and when a maximum absolute value of an angle between the light beam deflected by the first deflector and the central axis on an auxiliary scanning plane including the central axis and the auxiliary scanning direction is defined as B, while a total number of scanning lines corresponding to one frame on the surface to be scanned is defined as N, a following conditional equation is satisfied:
1
-
0.25
N
≤
tan
B
B
·
arctan
tan
2
B
+
(
tan
A
cos
B
)
2
tan
2
B
+
(
tan
A
cos
B
)
2
≤
1
+
0.25
N
5. The scanning optical device according to claim 1 , wherein deflection surfaces of the first deflector and the second deflector are arranged at optically conjugate positions by the condensing optical system and the collecting optical system.
6. A scanning optical device for scanning a plurality of scanning lines on a surface to be scanned, the scanning optical device comprising:
a plurality of light source units for emitting light beams, the plurality of light source units being spaced evenly apart in an auxiliary scanning direction, the auxiliary scanning direction being a direction perpendicular to a main scanning direction, wherein the scanning lines are scanned in the main scanning direction;
a collecting optical system that collects chief rays of respective emitted light beams;
a deflector that deflects the collected respective light beams in the main scanning direction; and
a scanning optical system that scans the light beams deflected by the deflector on the surface to be scanned,
wherein the collecting optical system is configured to have an f-sin θ characteristic and the scanning optical system is configured to have an f-sin θ characteristic.
7. The scanning optical device according to claim 6 , wherein the plurality of light source units are an array light source having a plurality of light source units that are evenly spaced apart in the auxiliary scanning direction.
8. The scanning optical device according to claim 7 , wherein the scanning optical device includes a plurality of array light sources arranged in line in the main scanning direction.