JPH0749461A - Multiplex wavelength and multiplex diode laser ros - Google Patents

Abstract

PURPOSE: To introduce beams as necessary adjacent lines on a photosensitive surface by improving the device so that it is not necessary to buffer the scanning lines of a multiple diode laser ROS scanning system. CONSTITUTION: The wavelength of a diode output is selected so as to be made different between each diode 14 and 16 within a selection range. Beams are made in parallel, and introduced through a distributing element such as a prism 40 arranged so that the beams can be mutually focused. The beams are reflected on a reflection surface 28 of a polygon 30, and then swept as adjacent scanning lines 36 and 38 across a surface 34 of an image forming medium.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION The present invention relates to a laser printing system using a multi-wavelength, multi-diode laser, and more particularly, it is arranged in an optical scanning path so that a diode output is scanned as an adjacent line on a photosensitive image plane. And an improved system including distributed elements.

One problem with conventional multi-beam laser scanning systems is that the distance (pitch) between the multiple diodes is large compared to the light emitting area of the diodes (generally at least 5).
That is, the diode output is imaged on the photoreceptor in a few scan lines separated. The prior art has addressed this problem by first using an electronic buffer to store scan line information and printing it in the form of interlaced scanning. However, such buffers add cost and complexity to the system.

The present invention addresses the above problems by using multiple diode lasers, each having a diode with a different output wavelength, to focus dispersive elements such as prisms or diffraction gratings. These beams are arranged along the optical path so that they are close to each other when they are imaged on the light acceptor.

It is known in the prior art to use dispersive elements to achieve various purposes in scanning systems. Toshiba Publication No. 63-155018 discloses placing a prism in the objective of a polygon scanner to produce a collimated beam, but that beam of the same wavelength is as disclosed by this invention. It will not be collected as an adjacent line.

The present invention specifically provides a laser light source for producing multiple light beam outputs, each having a different wavelength.
Optical scanning means for receiving the output beam and for guiding the beams along the optical path as a plurality of scanning beams to simultaneously form a plurality of in-focus adjacent lines on the surface of the photosensitive surface;
It further relates to a multi-beam scanning system having said scanning means including dispersive elements arranged along the optical path to bring each focused beam to an adjacent line at the light acceptor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side schematic view of a multi-beam ROS scanning system with diode outputs of different wavelengths passing through a prism and focusing on the image plane as adjacent lines.

DESCRIPTION OF THE INVENTION In the drawings, 10 shows a side view of a dual beam ROS system. However, in the present invention, the laser does not necessarily have a dual diode output, and an array including two or more diodes is also included. Laser source 1
2 has two independently manageable diodes 14, 16
, Each diode is a light emitter 1
I have 8 and 20. The diodes 14, 16 may be formed on a single semiconductor chip, as disclosed in U.S. Pat. No. 4,445,125, which is hereby incorporated by reference. The light emitters 18, 20 have an FMHM (full width at half maximum) of e and are separated by a pitch width p of about 5 times the distance e. (The ratio of this distance is the lowest, and the actual ratio may be large. The widths shown are not constant.) The laser beam outputs 22 and 24 have different wavelengths from the first aspect of the present invention. The beams 22 and 24 are collimated by a collimator lens 26, and a cylindrical lens 27 causes a lens 26 along the optical path,
Focusing is performed at a certain magnification determined by the position of 27. The collimated beam is focused by the cylindrical lens 27 onto the face of the polygon mirror 30. The beam is reflected from surface 28 as polygon 30 rotates along axis 31,
It passes through the auxiliary correction lens 32. The beam is then swept in the fast scan direction (towards the page) across the surface of the photosensitive imaging surface 34, and scan lines 36, 38 across the imaging medium.
To form. From the second aspect of the invention, the 60 degree prism of the dispersive element of this embodiment is placed along the optical path. The prism is placed between the lens 27 and the polygon 30, but it can be placed in other positions. Prism 40 is sagittal (s
It has a refractive power in the agittal direction. The purpose of the prism 40 is to reduce the distance S between the diodes so that the scan lines 36, 38 are formed adjacent to each other in the image plane, as will be seen below.

To make the significance of using a different diode wavelength output and prism 40 more clear, a detailed example of a scanning system will now be given. Referring again to FIG. 1, the laser source 12 has a 0.002 mm (2 micron) F
It is formed of diodes 14, 16 having light emitters 18, 20 with WHM (e). The space between the diodes is 0.01m to (10 microns) and the output 24 is 7
It has a wavelength of 90 nm and the output 22 has a wavelength of 761 nm. The surface 40A of the prism 40 has an inclination 6
With a 0 degree prism, rays 22 and 24 are 50 on surface 60A.
It is guided at an incident angle of °. The luminous body outputs 22 and 24 are almost 2
It is magnified 0 times, and at the surface of the surface 28 and further on the image plane 34,
Form a spot with a size of 0.04 mm (40 microns). Lens 32 is a 1x toroidal lens.

The operation of the diode 1 will be described below.
4 and 16 operate separately and at the same time, 761n each
m, laser beam output 22, 2 having wavelength of 790 nm
4 is generated. The beams are collimated by collimator lens 26 and transformed into parallel beams 22A, 24A. The collimated beam then passes through the converging cylindrical lens 27 and the surface 40A
Through the prism 40. They are no longer parallel because the index of refraction of the glass decreases with the decreasing wavelength and the beams 22A, 24A are refracted by the surface 40A and directed slightly downward, causing less refraction of the lower wavelength output 22. Due to the incidence of the two rays and the refraction at the surface 40B, the separation between the two beams 22B, 24B is such that the expanded beam is imaged on a polygonal surface 28 to a point approximately 40 microns in size, and then It becomes narrow until it reflects. The reflected beam passes through the 1 × auxiliary correction lens 32 and is then swept in the fast scan direction to form scan lines 36, 38. Although the position of the prism 40 is shown between the condenser lens 27 and the polygon 30, it may be arranged at another position along the optical path determined by a normal lens design method.

Although the present invention discloses a dual beam diode, it is not so limited. It can also be implemented with 3 to 4 diode arrays, for example as long as the diode outputs have different wavelengths. It is also possible to arrange the diodes in multiple chip sources. The physical size of the prism may need to be increased to accommodate the increasing number of rays that pass through it, and while the prism is shown as a beam dispersive element, a reflective or transmissive refractive grating Other elements such as can also be used.

[Brief description of drawings]

FIG. 1 is a side schematic view of a multi-beam ROS scanning system with diode outputs of different wavelengths passing through a prism and focusing on the image plane as adjacent lines.

[Explanation of symbols]

 10 Dual beam ROS system 12 Laser source 14, 16 Diode 18, 20 Light emitter 22, 24 Beam output 26, 27 Lens 28 Surface 30 Multi-faceted mirror polygon 31 Axis 32 Auxiliary correction lens 34 Photosensitive imaging surface 36, 38 Scan line 40 prism

Claims (2)

[Claims] 1. A multi-beam scanning system including: a laser light source for producing a plurality of light beam outputs having different wavelengths; a plurality of focal points on a surface of a photosensitive surface for receiving the output beam. Optical scanning means for guiding the beams along the optical path as a plurality of scanning beams for simultaneously forming the adjacent lines aligned with each other, and along the optical path for collecting the focused scanning beams as the adjacent lines of the optical acceptor. A scanning means including distributed elements arranged. 2. The system of claim 1, wherein the dispersive element is a prism having a sagittal refractive power.