Optical scanning device with at least one resin lens for controlling a beam waist position shift
First Claim
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1. An optical scanning device comprising:
- a light source that emits a light beam;
a first optical system that guides the light beam emitted by the light source;
an optical deflector that deflects the light beam guided by the first optical system; and
a second optical system that converges the light beam deflected by the optical deflector on a surface to be scanned, whereinthe first optical system includes at least one resin lens having a diffractive surface,the second optical system includes at least one resin optical element, anda beam diameter depth in a main scanning direction, Wm, that can have a maximum intensity of 1/e2, satisfies conditions
Δ
m1Δ
m2Δ
m3−
Δ
d1×
(f2/f1)2<
Wm/40
(1)
Δ
d1>
0 and Δ
m2<
0
(2)where, Δ
m1 is a beam waist position shift in the main scanning direction due to a change in the power in a refracting unit when the temperature in the first optical system rises by 1°
C., Δ
m2 is a beam waist position shift in the main scanning direction due to a change in the power in a diffracting unit when the temperature in the first optical system rises by 1°
C., Δ
m3 is a beam waist position shift in the main scanning direction when the temperature in the second optical system rises by 1°
C., Δ
d1 is a shift in the distance between a forward principal point of the first optical system in the main scanning direction and the light source when the temperature in the first optical system rises by 1°
C., f1 is a focal distance of the first optical system in the main scanning direction, and f2 is a focal distance of the second optical system in the main scanning direction.
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Abstract
A first optical system guides a light beam from a light source to an optical deflector, and a second optical system converges the light beam deflected by the optical deflector on a surface to be scanned. The first optical system includes at least one resin lens having a diffractive surface. The second optical system includes at least one resin optical element. A beam diameter depth in a main scanning direction, Wm, that can have a maximum intensity of 1/e2, satisfies conditions
Δm1+Δm2+Δm3−Δd1×(f2/f1)2<Wm/40 (1)
Δd1>0 and Δm2<0. (2)
44 Citations
16 Claims
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1. An optical scanning device comprising:
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a light source that emits a light beam; a first optical system that guides the light beam emitted by the light source; an optical deflector that deflects the light beam guided by the first optical system; and a second optical system that converges the light beam deflected by the optical deflector on a surface to be scanned, wherein the first optical system includes at least one resin lens having a diffractive surface, the second optical system includes at least one resin optical element, and a beam diameter depth in a main scanning direction, Wm, that can have a maximum intensity of 1/e2, satisfies conditions
Δ
m1Δ
m2Δ
m3−
Δ
d1×
(f2/f1)2<
Wm/40
(1)
Δ
d1>
0 and Δ
m2<
0
(2)where, Δ
m1 is a beam waist position shift in the main scanning direction due to a change in the power in a refracting unit when the temperature in the first optical system rises by 1°
C., Δ
m2 is a beam waist position shift in the main scanning direction due to a change in the power in a diffracting unit when the temperature in the first optical system rises by 1°
C., Δ
m3 is a beam waist position shift in the main scanning direction when the temperature in the second optical system rises by 1°
C., Δ
d1 is a shift in the distance between a forward principal point of the first optical system in the main scanning direction and the light source when the temperature in the first optical system rises by 1°
C., f1 is a focal distance of the first optical system in the main scanning direction, and f2 is a focal distance of the second optical system in the main scanning direction.- View Dependent Claims (2, 3, 4, 5)
where, Δ
m′
1 is a beam waist position shift in the main scanning direction due to a change in the power in the refracting unit of the first optical system, Δ
m′
2 is a beam waist position shift in the main scanning direction due to a change in the power in the diffracting unit of the first optical system, and Δ
m′
3 is a beam waist position shift in the second optical system in the main scanning direction, when the emission wavelength of the light source is increased by 1 nm.
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3. The optical scanning device according to claim 1, wherein the first optical system includes at least one glass lens, the power of the glass lens in the main scanning direction being greater than the power of the resin lens in the main scanning direction.
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4. The optical scanning device according to claim 1, wherein the first optical system and the second optical system include a plurality of lenses and all the lenses are resin lenses.
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5. The optical scanning device according to claim 1, further comprising a housing configured to house the first optical system and the second optical system, wherein the housing includes an air passage that allows flow of air between the first optical system and the second optical system.
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6. An optical scanning device comprising:
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a light source that emits a light beam; a first optical system that guides the light beam emitted by the light source; an optical deflector that deflects the light beam guided by the first optical system; and a second optical system that converges the light beam deflected by the optical deflector on a surface to be scanned, wherein the first optical system includes at least one resin lens having a diffractive surface, the second optical system includes at least one resin optical element, and a beam diameter depth in a sub-scanning direction, Ws, that can have a maximum intensity of 1/e2, satisfies conditions
Δ
s1+Δ
s2+Δ
s3−
Δ
d1×
(β
1×
β
2)2<
Ws/40
(4)
Δ
d1>
0 and Δ
s2+Δ
s2<
0
(5)where, Δ
s1 is a beam waist position shift in the sub-scanning direction due to a change in the power in a refracting unit when the temperature in the first optical system rises by 1°
C., Δ
s2 is a beam waist position shift in the sub-scanning direction due to a change in the power in a diffracting unit when the temperature in the first optical system rises by 1°
C., Δ
s3 is a beam waist position shift in the sub-scanning direction when the temperature in the second optical system rises by 1°
C., Δ
d1 is a shift in the distance between a forward principal point in a main scanning direction of the first optical system and the light source when the temperature in the first optical system rises by 1°
C., β
1 is a lateral magnification of the first optical system in the sub-scanning direction, and β
2 is a lateral magnification of the second optical system in the sub-scanning direction.- View Dependent Claims (7, 8, 9)
where, Δ
s′
1 is a beam waist position shift in the sub-scanning direction due to a change in the power in a refracting unit of the first optical system, Δ
s′
2 is a beam waist position shift in the sub-scanning direction due to a change in the power in the diffracting unit of the first optical system, and Δ
s′
3 is a beam waist position shift in the sub-scanning direction in the second optical system, when the emission wavelength of the light source is increased by 1 nm.
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8. The optical scanning device according to claim 6, wherein
the first optical system includes at least one resin lens having a diffractive surface, the second optical system includes at least one resin optical element, and a beam diameter depth in a main scanning direction, Wm, that can have a maximum intensity of 1/e2, satisfies conditions
Δ-
m1+Δ
m2+Δ
m3−
Δ
d1×
(f2/f1)2<
Wm/40
(1)
Δ
d1>
0 and Δ
m2<
0
(2)where, Δ
m1 is a beam waist position shift in the main scanning direction due to a change in the power in a refracting unit when the temperature in the first optical system rises by 1°
C., Δ
m2 is a beam waist position shift in the main scanning direction due to a change in the power in the diffracting unit when the temperature in the first optical system rises by 1°
C., Δ
m3 is a beam waist position shift in the main scanning direction when the temperature in the second optical system rises by 1°
C., Δ
d1 is a shift in the distance between a forward principal point of the first optical system in the main scanning direction and the light source when the temperature in the first optical system rises by 1°
C., f1 is a focal distance of the first optical system in the main scanning direction, and f2 is a focal distance of the second optical system in the main scanning direction.
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m1+Δ
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9. The optical scanning device according to claim 6, wherein the light source is a semiconductor laser device, and
the beam diameter depth in the main scanning direction, Wm, that can have a maximum intensity of 1/e2, satisfies a condition,
−-
Wm<
Δ
m′
1+Δ
m′
2+Δ
m′
3<
0
(3)where, Δ
m′
1 is a beam waist position shift in the main scanning direction due to a change in the power in the refracting unit of the first optical system, Δ
m′
2 is a beam waist position shift in the main scanning direction due to a change in the power in the diffracting unit of the first optical system, and Δ
m′
3 is a beam waist position shift in the second optical system in the main scanning direction, when the emission wavelength of the light source is increased by 1 nm.
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Wm<
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10. An optical scanning device comprising:
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a light source that emits a light beam; a coupling lens that shapes the light beam into a beam pattern; an anamorphic optical element that guides the light beam shaped by the coupling lens; an optical deflector that deflects the light beam guided by the anamorphic optical element; and a scanning optical system that converges the light beam deflected by the optical deflector on a surface to be scanned to form a laser spot, wherein the scanning optical system includes more than one resin lens, the anamorphic optical element is an anamorphic resin lens having a first surface and a second surface, the first surface being anamorphic refractive surface, the second surface bearing thereon a power diffractive surface with an elliptical shape and having an axis in a main scanning direction, and the power of the power diffractive surface in a sub-scanning direction is larger than the power in the main scanning direction, and the power of the power diffractive surface is set so that a beam waist position shift in the main scanning direction or the sub-scanning direction or both the main scanning direction and the sub-scanning direction, caused by mode hopping or temperature variation in the semiconductor laser device is substantially zero. - View Dependent Claims (11, 12, 13)
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14. An optical scanning device comprising:
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a light source that emits a light beam; a coupling lens that shapes the light beam into a beam pattern; an anamorphic optical element that guides the light beam shaped by the coupling lens; an optical deflector that deflects the light beam guided by the anamorphic optical element; and a scanning optical system that converges the light beam deflected by the optical deflector on a surface to be scanned to form a laser spot, wherein the scanning optical system includes more than one resin lens, the anamorphic optical element is an anamorphic resin lens having a first surface and a second surface, the first surface being anamorphic refractive surface, the second surface bearing thereon a power diffractive surface having an axis in a main scanning direction, the power of the power diffractive surface is set so that a beam waist position shift in the main scanning direction or a sub-scanning direction or both the main scanning direction and the sub-scanning direction, caused by mode hopping or temperature variation in the semiconductor laser device is substantially zero, and the power diffractive surface is an elliptical power diffractive surface formed on a plane surface.
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15. An image forming apparatus comprising an optical scanning device that includes
a light source that emits a light beam; -
a first optical system that guides the light beam emitted by the light source; an optical deflector that deflects the light beam guided by the first optical system; and a second optical system that converges the light beam deflected by the optical deflector on a surface to be scanned, wherein the first optical system includes at least one resin lens having a diffractive surface, the second optical system includes at least one resin optical element, and a beam diameter depth in a main scanning direction, Wm, that can have a maximum intensity of 1/e2, satisfies conditions
Δ
m1+Δ
m2+Δ
m3−
Δ
d1×
(f2/f1)2<
Wm/40
(1)
Δ
d1>
0 and Δ
m2<
0
(2)where, Δ
m1 is a beam waist position shift in the main scanning direction due to a change in the power in a refracting unit when the temperature in the first optical system rises by 1°
C., Δ
m2 is a beam waist position shift in the main scanning direction due to a change in the power in the diffracting unit when the temperature in the first optical system rises by 1°
C., Δ
m3 is a beam waist position shift in the main scanning direction when the temperature in the second optical system rises by 1°
C., Δ
d1 is a shift in the distance between a forward principal point of the first optical system in the main scanning direction and the light source when the temperature in the first optical system rises by 1°
C., f1 is a focal distance of the first optical system in the main scanning direction, and f2 is a focal distance of the second optical system in the main scanning direction.
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16. An image forming apparatus comprising:
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a photosensitive image bearing unit; an optical scanning unit that scan a surface of the image bearing unit with a light beam to thereby forming a latent image on the image bearing unit; and a developing unit that develops the latent image on the image bearing unit into a visual image, wherein the optical scanning unit includes a light source that emits a light beam; a coupling lens that shapes the light beam into a beam pattern; an anamorphic optical element that guides the light beam shaped by the coupling lens; an optical deflector that deflects the light beam guided by the anamorphic optical element; and a scanning optical system that converges the light beam deflected by the optical deflector on a surface to be scanned to form a laser spot, wherein the scanning optical system includes more than one resin lens, the anamorphic optical element is an anamorphic resin lens having a first surface and a second surface, the first surface being anamorphic refractive surface, the second surface bearing thereon a power diffractive surface with an elliptical shape and having an axis in a main scanning direction, and the power of the power diffractive surface in a sub-scanning direction is larger than the power in the main scanning direction, and the power of the power diffractive surface is set so that a beam waist position shift in the main scanning direction or the sub-scanning direction or both the main scanning direction and the sub-scanning direction, caused by mode hopping or temperature variation in the semiconductor laser device is substantially zero.
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Specification