Optical scanning system and imaging apparatus for using same
View Patent ↗A scanning unit includes a light source controllable to emit a light beam; a scanning mirror having a plurality of reflective surfaces, the scanning mirror receiving the light beam from the light source and deflecting at least portions of the light beam along a scan direction; and a collimator lens disposed between the light source and the scanning mirror, the collimator lens having a light incident surface that is spherical and a light exit surface that is aspheric such that the light beam, after passing through the collimator lens, is diverged by the collimator lens so as to be incident on at least two reflective surfaces of the scanning mirror.
1. A scanning system, comprising:
a light source controllable to emit a light beam;
a rotating scanning member having a plurality of reflective surfaces, the scanning member for receiving the light beam from the light source and deflecting at least portions of the light beam along a scan direction; and
a collimator lens disposed between the light source and the scanning member, the collimator lens positioned at a distance less than a focal length thereof from the light source such that as the light beam from the light source passes through and exits the collimator lens, the collimator lens diverges the light beam such that the light beam is incident on at least two reflective surfaces of the scanning member as a diverging light beam, wherein the collimator lens has a spherical light incident surface that is a concave surface and an aspheric light exit surface that is a convex surface.
2. The scanning system of claim 1 , wherein the light beam has a first width upon entering the collimator lens, and a second width that is at least twice greater than the first width at the scanning member.
3. The scanning system of claim 1 , wherein the collimator lens and the scanning member define therebetween an optical path of the light beam, the optical path having only a prescan lens disposed therealong.
4. The scanning system of claim 1 , further comprising at least one scan lens disposed downstream from the scanning member relative to an optical path of the light beam, the at least one scan lens for focusing the at least portions of the light beam on an imaging surface.
5. The scanning system of claim 1 , wherein a beam path length of the light beam from the light source to the scanning member is between about 100 mm to about 250 mm.
6. The scanning system of claim 1 , wherein the scanning member comprises a polygon mirror.
7. The scanning system of claim 1 , wherein the spherical light incident surface is defined by
z
1
=
(
r
1
)
2
R
1
(
1
+
1
-
(
r
1
)
2
(
R
1
)
2
)
,
wherein where z1 is a surface sag of the spherical light incident surface, R1 is a radius of curvature of the spherical light incident surface, and r1 is a distance from an optical axis of the collimator lens, and wherein the aspheric light exit surface is defined by
z
2
=
(
r
2
)
2
R
2
(
1
+
1
-
(
1
+
K
)
(
r
2
)
2
(
R
2
)
2
)
+
A
4
(
r
2
)
4
+
A
6
6
(
r
2
)
6
+
A
8
(
r
2
)
8
,
where z2 is a surface sag of the aspheric light exit surface, R2 is a radius of curvature of the aspheric light exit surface, r2 is a distance from an optical axis of the collimator lens, K is a conic coefficient, and A 4 , A 6 , and A 8 are the aspheric coefficients.
8. A scanning system for an imaging apparatus, comprising:
a light source controllable to emit a light beam;
a scanning mirror having a plurality of reflective surfaces, the scanning mirror receiving the light beam from the light source and deflecting at least portions of the light beam along a scan direction; and
a collimator lens disposed between the light source and the scanning mirror, the collimator lens having a light incident surface that is spherical and concave and a light exit surface that is aspheric and convex such that the collimator lens diverges the light beam upon exiting the collimator lens, the light beam being incident on at least two reflective surfaces of the scanning mirror as a diverging light beam.
9. The scanning system of claim 8 , wherein the light source is positioned along an optical axis of the collimator lens and at a distance from the collimator lens that is less than a focal length thereof.
10. The scanning system of claim 8 , wherein the light beam enters the light incident surface of the collimator lens at a first width, diverges upon exiting the light exit surface of the collimator lens, and arrives at the scanning mirror at a second width that is at least twice greater than the first width.
11. The scanning system of claim 10 , wherein the first width of the light beam is between about 4 mm and about 5 mm, and the second width of the light beam is between about 8 mm and about 14 mm.
12. The scanning system of claim 8 , wherein the collimator lens and the scanning mirror define therebetween an optical path of the light beam, the optical path having only a prescan lens disposed therealong.
13. The scanning system of claim 8 , further comprising at least one scan lens disposed downstream from the scanning mirror relative to an optical path of the light beam, the at least one scan lens for focusing the at least portions of the light beam on an imaging surface.
14. The scanning system of claim 8 , wherein the scanning mirror comprises a polygon mirror.
15. An imaging device, comprising:
a photoconductive member; and
a scanning unit generating a light beam and repeatedly scanning at least portions of the light beam across the photoconductive member to form scan lines thereon, the scanning unit including:
a light source for emitting the light beam;
a rotating scanning member having a plurality of reflective surfaces for receiving the light beam and deflecting at least portions thereof towards the photoconductive member; and
a collimator lens disposed between the light source and the scanning member, the collimator lens positioned at a distance less than a focal length thereof from the light source such that when the light beam from the light source passes through and exits the collimator lens, the collimator lens diverges the light beam such that the light beam, upon arriving at the scanning member, is a diverging light beam that has a width that is wider than a length of a reflective surface of the scanning member, wherein the collimator lens has a light incident surface that is spherical and concave and a light exit surface that is aspheric and is convex.
16. The imaging device of claim 15 , wherein the width of the light beam at the scanning member is at least twice greater than a width of the light beam at a light incident surface of the collimator lens.
17. The imaging device of claim 16 , wherein the width of the light beam at the light incident surface is between about 4 mm and about 5 mm, and the width of the light beam at the scanning member is between about 8 mm and about 14 mm.
18. The imaging device of claim 15 , wherein the scanning unit further includes a prescan lens disposed along an optical path of the light beam defined between the collimator lens and the scanning member, the prescan lens being the only optical component along the optical path.
19. The imaging device of claim 15 , wherein the scanning unit further includes at least one scan lens disposed between the scanning member and the photoconductive member, the at least one scan lens for focusing at least portions of the light beam deflected by the scanning member onto the photoconductive member.
20. The imaging device of claim 15 , wherein the collimator lens diverges the light beam such that the diverging light beam is incident on at least two reflective surfaces of the rotating scanning member at one time.