Back to results
US 6,476,846 B1Granted
Multi-beam scanner and image forming apparatus including the same
AssigneeBrother Kogyo Kabushiki Kaisha
InventorsHiroyuki Kashima, Yumio Matsumoto, Yutaka Hattori
Life of this patent
Estimating the term…
Abstract
A multi-beam scanner has two light emitting points ch1, ch2 and an optical system. The light emitting points ch1, ch2 are separated by a distance Δalong a depth-of-focus direction. The longitudinal magnification α, or the image-side numerical aperture NA, of the optical system is set so that the surface to be scanned of a photosensitive drum is positioned within a range where the depths of focus de of the light beams from the two light emitting points ch1, ch2 overlap. The multi-beam scanner can focus the light beams onto the surface of the photosensitive drum at all the scanning positions even when the optical system has curvature of field.
Claims24
A multi-beam scanner, comprising:
- a light-emitting unit which has a plurality of light emitting portions for emitting a plurality of light beams, the plurality of light emitting portions being separated from one another in a depth direction of the light beams;
- a scanning unit that deflects the light beams in a main scanning direction in a plurality of lines across a surface of an object to be scanned, the plurality of lines being arranged along an auxiliary scanning direction that is substantially perpendicular to the main scanning direction;
- and
- a light converging unit converging the plurality of light beams onto the surface of the object to be scanned, the light converging unit allowing depths of focus of the light beams from all the light emitting portions to overlap on the surface of the object, wherein an amount of a range where depths of focus of the light beams from all the light emitting portions overlap has a positive value at all the scan positions of the surface of the object, wherein the light converging unit has a longitudinal magnification of a value setting the amount of the overlapping range to a positive value at all the scan positions of the surface of the object.
1 more element
A multi-beam scanner, comprising:
- a light-emitting unit which has a plurality of light emitting portions for emitting a plurality of light beams, the plurality of light emitting portions being separated from one another in a depth direction of the light beams;
- a scanning unit that deflects the light beams in a main scanning direction in a plurality of lines across a surface of an object to be scanned, the plurality of lines being arranged along an auxiliary scanning direction that is substantially perpendicular to the main scanning direction;
- and
- a light converging unit converging the plurality of light beams onto the surface of the object to be scanned, the light converging unit allowing depths of focus of the light beams from all the light emitting portions to overlap on the surface of the object, wherein the center portions of radiations from the plurality of light emitting portions, along the main scanning direction, are separated from one another in the depth direction of the light beams, the light converging unit allowing depths of focus, along the main scanning direction, of the light beams from all the light emitting portions to overlap on the surface of the object, an amount of a range where depths of focus, along the main scanning direction, of the light beams from all the light emitting portions overlap has a positive value at all the scan positions of the surface of the object, and the light converging unit has a longitudinal magnification, along the main scanning direction, of a value setting the amount of the overlapping range to a positive value at all the scan positions of the surface of the object.
1 more element
A multi-beam scanner, comprising:
- a light-emitting unit which has a plurality of light emitting portions for emitting a plurality of light beams, the plurality of light emitting portions being separated from one another in a depth direction of the light beams;
- a scanning unit that deflects the light beams in a main scanning direction in a plurality of light beams onto the surface of the object to be scanned, in a plurality of lines across a surface of an object to be scanned, the plurality of lines being arranged along an auxiliary scanning direction that is substantially perpendicular to the main scanning direction;
- and
- a light converging unit converging the plurality of light beams onto the surface of the object to be scanned, the light converging unit allowing depths of focus of the light beams from all the light emitting portions to overlap on the surface of the object, wherein the center portions of radiations from the plurality of light emitting portions, along the main scanning direction, are separated from one another in the depth direction of the light beams, the light converging unit allowing depths of focus, along the main scanning direction, of the light beams from all the light emitting portions to overlap on the surface of the object, and the light converging unit includes:
- a collimate lens, that is disposed between the light emitting unit and the scanning unit, for collimating, into approximate parallel beams, the light beams emitted from the light emitting points, the collimate lens having a focal length fco;
- and
- a scan lens unit, that is disposed between the scanning unit and the object to be scanned, for scanning the collimated light, which is deflected by the scanning unit, in the plurality of lines on the surface of the object to be scanned, the scan lens having a focal length fm in the main scanning direction, the focal length fco and the focal length fm satisfying the following inequality:
- (fm/fco)2·Δzm+Cfm<dem.
5 more elements
A multi-beam scanner, comprising:
- a light-emitting unit which has a plurality of light emitting portions for emitting a plurality of light beams, the plurality of light emitting portions being separated from one another in a depth direction of the light beams;
- a scanning unit that deflects the light beams in a main scanning direction in a plurality of lines across a surface of an object to be scanned, the plurality of lines being arranged along an auxiliary scanning direction that is substantially perpendicular to the main scanning direction;
- and
- a light converging unit converging the plurality of light beams onto the surface of the object to be scanned, the light converging unit allowing depths of focus of the light beams from all the light emitting portions to overlap on the surface of the object, wherein an amount of a range where depths of focus of the light beams from all the light emitting portions overlap has a positive value at all the scan positions of the surface of the object, and the light converging unit has an image-side numerical aperture of a value setting the amount of the overlapping range to a positive value at all the scan positions of the surface of the object.
1 more element
A multi-beam scanner, comprising:
- a light-emitting unit which has a plurality of light emitting portions for emitting a plurality of light beams, the plurality of light emitting portions being separated from one another in a depth direction of the light beams;
- a scanning unit that deflects the light beams in a main scanning direction in a plurality of lines across a surface of an object to be scanned, the plurality of lines being arranged along an auxiliary scanning direction that is substantially perpendicular to the main scanning direction;
- and
- a light converging unit converging the plurality of light beams onto the surface of the object to be scanned, the light converging unit allowing depths of focus of the light beams from all the light emitting portions to overlap on the surface of the object, wherein the center portions of radiations from the plurality of light emitting portions, along the main scanning direction, are separated from one another in the depth direction of the light beams, the light converging unit allowing depths of focus, along the main scanning direction, of the light beams from all the light emitting portions to overlap on the surface of the object, an amount of a range where depths of focus, along the main scanning direction, of the light beams from all the light emitting portions overlap has a positive value at all the scan positions of the surface of the object, and the light converging unit has an image-side numerical aperture, along the main scanning direction, of a value setting the amount of the overlapping range to a positive value at all the scan positions of the surface of the object.
1 more element
A multi-beam scanner, comprising:
- a light-emitting unit which has a plurality of light emitting portions for emitting a plurality of light beams, the plurality of light emitting portions being separated from one another in a depth direction of the light beams;
- a scanning unit that deflects the light beams in a main scanning direction in a plurality of lines across a surface of an object to be scanned, the plurality of lines being arranged along an auxiliary scanning direction that is substantially perpendicular to the main scanning direction;
- and
- a light converging unit converging the plurality of light beams onto the surface of the object to be scanned, the light converging unit allowing depths of focus of the light beams from all the light emitting portions to overlap on the surface of the object, wherein an amount of a range where depths of focus of the light beams from all the light emitting portions overlap has a positive value at all the scan positions of the surface of the object;
- and further comprising the object to be scanned, which is driven to rotate in the auxiliary scanning direction, wherein the light converging unit has an amount of the overlapping range (de−ΔS−Cf) to a positive value at all the scan positions of the surface of the object, wherein de is the amount of the focal depth of the light beams from the light emitting portions, ΔS is a distance between beam waist positions of the light beams in the depth direction, and Cf is an amount of the curvature of field in the light converging unit, and the surface of the object to be scanned is located in a substantial center of the overlapping range of (de−ΔS−Cf).
2 more elements
An image forming device comprising:
- a photosensitive body driven to rotate in the auxiliary scanning direction;
- and
- a multi-beam scanner, which includes:
- a light-emitting unit which has a plurality of light emitting portions for emitting a plurality of light beams, the plurality of light emitting portions being separated from one another in a depth direction of the light beams;
- a scanning unit that deflects the light beams in a main scanning direction in a plurality of lines across a surface of the photosensitive body, the plurality of lines being arranged along an auxiliary scanning direction that is substantially perpendicular to the main scanning direction;
- and
- a light converging unit converging the plurality of light beams onto the surface of the photosensitive body, the light converging unit allowing depths of focus of the light beams from all the light emitting portions to overlap on the surface of the photosensitive body, thereby serially irradiating the plurality of light beams on the photosensitive body to form latent images, wherein the surface of the photosensitive body is located in a substantial center of the overlapping range, in the depths of focus of the light beams from all the light emitting points, that has the amount of (de−ΔS−Cf) wherein de is the amount of the focal depth of the light beams from the light emitting portions, ΔS is a distance between beam waist positions of the light beams in the depth direction, and Cf is an amount of the curvature of field in the light converging unit.
4 more elements
Dependencies are inferred from the claim text.