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US 5,212,501 AGranted
Image recording apparatus with a laser optical unit
AssigneeMinolta Camera Kabushiki Kaisha
InventorsHiromu Nakamura, Akiyoshi Hamada, Satoru Ono, Masanori Murakami, Toshio Naiki, Kunihiko Omura, Masahito Niikawa
Life of this patent
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Abstract
An image recording apparatus wherein a laser diode which is disposed on a focal point of a micro Fresnel lens emits a laser beam and the laser beam is collimated by the Fresnel lens and scanned on a photosensitive drum by a polygonal mirror and an f.theta. optical system. A change in temperature of the laser diode does not result in such serious defocus as to cause practical problems.
Claims19
An image recording apparatus comprising:
- a laser diode for emitting a laser beam in accordance with image data;
- a convergent member having a diffraction effect for collimating the laser beam, the convergent member being disposed in front of the laser diode;
- and
- optical scanning means for scanning the laser beam which passed through the convergent member on an image surface;
- wherein the image recording apparatus meets a condition expressed by an expression ##EQU17## in which expression, .DELTA..lambda. denotes a variation in wavelength of the laser beam from a designed wavelength .lambda. with a rise in temperature of the laser diode from a standard temperature;
- f.sub.co denotes a focal length of the convergent member when the laser beam has the wavelength .lambda.;
- D.sub.0 denotes a diameter of a beam spot on the image surface when the laser beam has the wavelength .lambda.;
- D.sub.1 denotes a tolerable limit of the diameter of the beam spot;
- and
- f.sub.H denotes a focal length of the optical scanning means in a main-scanning direction.
7 more elements
An image recording apparatus comprising:
- a laser diode for emitting a laser beam in accordance with image data;
- a convergent member having a diffraction effect for converging the laser beam into a convergent pencil of rays, the convergent member being disposed in front of the laser diode;
- and
- optical scanning means for scanning the laser beam which passed through the convergent member on an image surface;
- wherein the image recording apparatus meets a condition expressed by an expression ##EQU18## in which expression, .DELTA..lambda. denotes a variation in wavelength of the laser beam from a designed wavelength .lambda. with a rise in temperature of the laser diode from a standard temperature;
- f.sub.co denotes a focal length of the convergent member when the laser beam has the wavelength .lambda.;
- D.sub.0 denotes a diameter of a beam spot on the image surface when the laser beam has the wavelength .lambda.;
- D.sub.1 denotes a tolerable limit of the diameter of the beam spot;
- b.sub.1 denotes a distance between the convergent member and its image point;
- and
- b.sub.2 denotes a distance between the optical scanning means and the image surface.
8 more elements
An image recording apparatus comprising:
- a laser diode for emitting a laser beam in accordance with image data;
- a convergent member having a diffraction effect for converging the laser beam, the convergent member being disposed in front of the laser diode;
- optical scanning means for scanning the laser beam which passed through the convergent member on an image surface;
- current supply means for supplying the laser diode with a current, the current being switched between a first level in accordance with a first state of image data and a second level in accordance with a second state of image data;
- and
- current control means for adjusting the first level of the current so that the laser diode keeps its output at a specified level;
- wherein the first level and the second level of the current are determined such that the laser beam varies its wavelength only within a specified range while the laser diode is supplied with the current switched between the first level and the second level.
4 more elements
An image recording apparatus comprising:
- a laser diode for emitting a laser beam in accordance with image data;
- a convergent member having a diffraction effect for converging the laser beam, the convergent member being disposed in front of the laser diode;
- optical scanning means for scanning the laser beam which passed through the convergent member on an image surface;
- current supply means for supplying the laser diode with a current, the current being switched between a first level in accordance with a first state of image data and a second level in accordance with a second state of image data;
- and
- current control means for adjusting the first level so that the laser diode keeps its output at a specified level and for adjusting the second level so that the first level and the second level has a difference not more than a specified amount.
3 more elements
Dependencies are inferred from the claim text.