JP2983666B2 - Multiple wavelength, multiple diode laser ROS - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser printing system using a multi-wavelength, multi-diode laser, and more particularly to a laser output system in which a diode output is scanned as an adjacent line on a photosensitive image plane. The present invention relates to an improved system including a distributed element.

One problem with conventional multiple beam laser scanning systems is that the distance (pitch) between multiple diodes is large (generally at least 5) compared to the light emitting area of the diodes.
Twice as large), which means that the diode output is imaged on the photoreceptor several scan lines apart. In the prior art, this problem has been addressed by first storing the scan line information using an electronic buffer and printing it in an interlaced scan. However, such buffers add to the cost and complexity of the system.

The present invention addresses the above problem by using multiple diode lasers, each having a diode with a different output wavelength, by dispersing a dispersive element, such as a prism or diffraction grating, into focus. The beams are arranged along the optical path so as to be close to each other when the beams are imaged on the light receiver.

[0004] The use of dispersive elements to achieve various purposes in scanning systems is known in the prior art. Toshiba Publication No. 63-155018 discloses placing a prism in the objective path of a polygon scanner to generate a parallel beam, but that beam of the same wavelength is used as disclosed in the present invention. They are not collected as adjacent lines.

The present invention is particularly directed to a laser light source for producing a plurality of light beam outputs, each having a different wavelength,
Light scanning means for receiving the output beam and guiding the beam along a light path as a plurality of scanning beams to simultaneously form a plurality of focused adjacent lines on the surface of the photosensitive surface;
It further relates to a multiple beam scanning system having the scanning means including dispersive elements arranged along the optical path to make each of the focused beams adjacent to the light receiver.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a multiple beam ROS scanning system having different wavelength diode outputs passing through a prism and focusing on the imaging plane as adjacent lines.

DESCRIPTION OF THE INVENTION In the drawing, reference numeral 10 denotes a side view of a dual beam ROS system. However, in the present invention, the laser does not always have a double diode output, but also includes an arrangement including two or more diodes. Laser source 1
2 has two independently addressable diodes 14, 16
Is incorporated, and each diode is a luminous body 1
I have 8,20. Diodes 14, 16 can be formed on a single semiconductor chip, as disclosed in US Pat. No. 4,445,125, the contents of which are incorporated herein by reference. The luminous bodies 18 and 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. (This distance ratio is the worst and the actual ratio may be large; the width shown is not a fixed ratio). The laser beam outputs 22, 24 have different wavelengths from the first aspect of the present invention. The beams 22, 24 are collimated by a collimator lens 26, and the lenses 26,
Focusing is performed at a certain magnification determined by the position 27. The parallel beam is focused on the surface of the polygon mirror 30 by the cylindrical lens 27. The beam is reflected from surface 28 as polygon 30 rotates along axis 31,
The light passes through the auxiliary correction lens 32. The beam is then swept across the surface of the photosensitive imaging surface 34 in the fast scan direction (towards the page) and scan lines 36, 38 across the imaging medium.
To form According to a second aspect of the invention, a 60 degree prism of the dispersive element of this embodiment is arranged along the optical path. The prism is located between lens 27 and polygon 30, but can be located at other locations. Prism 40 is sagittal (s
agittal) direction. The purpose of the prism 40 is to reduce the distance S between the diodes so that the scanning lines 36, 38 are formed adjacent to each other on the image plane, as will be seen below.

In order to better understand the significance of using a different diode wavelength output and prism 40, 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 and 16 having light emitters 18 and 20 having WHM (e). The space between the diodes is 0.01 m to (10 microns) and the output 24 is 7
The output 22 has a wavelength of 90 nm and the output 22 has a wavelength of 761 nm. The prism 40 has a surface 40A having an inclination 6
With a 0 degree prism, the rays 22, 24 are 50 on the surface 60A.
Guided at an incident angle of ゜. The illuminant outputs 22, 24 are approximately 2
Magnified by a factor of 0, at the surface of the surface 28 and further at the imaging surface 34,
Form spots as large as 0.04 mm (40 microns). Lens 32 is a 1x toroidal lens.

The operation will now be described.
4 and 16 are operated separately and simultaneously, respectively, at 761n
m, laser beam output having a wavelength of 790 nm 22,2
4 is generated. The beams are collimated by a collimator lens 26 and are turned 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 refractive index of the glass is reduced by the decreasing wavelength and the beams 22A, 24A are refracted by the surface 40A and directed slightly downward, reducing the 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 beam expanded to a point approximately 40 microns in size forms an image on the polygonal surface 28, It narrows until it is reflected. After passing through the 1x auxiliary correction lens 32, the reflected beam is swept in the high-speed scanning direction to form scanning lines 36 and 38. Although the position of the prism 40 is shown between the condenser lens 27 and the polygon 30, it can 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. For example, as long as the diode outputs have different wavelengths, it can be implemented with an array of three or four diodes. The diodes can also be located in multiple chip sources. The physical size of the prism may need to be increased to accommodate the increasing number of light rays passing through it, and while the prism is shown as a beam-dispersing element, a reflective or transmissive refractive grating Other elements such as can also be used.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Double beam ROS system 12 Laser source 14, 16 Diode 18, 20 Light emitter 22, 24 Beam output 26, 27 Lens 28 Surface 30 Polyhedral mirror polygon 31 Axis 32 Auxiliary correction lens 34 Photosensitive imaging surface 36, 38 Scanning line 40 Prism

Claims (1)

(57) [Claims] An optical scanning system comprising: a photosensitive surface; and a plurality of diodes arranged in a straight line on a common semiconductor substrate, the photosensitive surface having a light emitter with each diode separated by a pitch of width p. A semiconductor diode laser train comprising a laser; first means for generating a video drive signal; and said laser train of said laser train for emitting from said laser train a plurality of light beams, each output having a wavelength different by at least about 30 nm. Second means for providing the drive signal to at least some of the lasers; optical means for focusing the plurality of light beams on the photosensitive surface; and applying the plurality of light beams to form adjacent scan lines. Scanning means for scanning across the photosensitive surface; passing through the multiple beams to refract the multiple beams along a collection path that is a function of the wavelength difference. Optical refraction means positioned along the optical path to be scanned.