US 6,370,175 B1 · Laser beam luminous energy correction method, laser driving apparatus, laser beam scanner and image recording device

Abstract

The object of the present invention is to precisely correct the luminous energy of a laser beam on a scanned surface which varies according to scanning and varies according to an angle of incidence with the scanned surface when a laser beam emitted from a semiconductor laser for emitting a laser beam having luminous energy according to supply current is scanned on the scanned surface via a scanning optical system. To achieve the above object, only modulation current when supply current supplied to a semiconductor laser is divided into threshold current having a current value in the vicinity in the spontaneous emission area of an extrapolated point which is an intersection with an axis when a linear part corresponding to a laser emission area in the supply current-to-output luminous energy characteristic of the semiconductor laser is extrapolated up to the axis showing that luminous energy is zero and modulation current which is a residual current component acquired by subtracting threshold current from supply current is regulated based upon a gain control value acquired by multiplying a gain set value which functions as the criterion of gain for converting image data to modulation current by a correction coefficient according to an angle of incidence.

Claims23

Dependent claims

A laser beam luminous energy correction method for correcting the variation of an output beam according to a beam position or an angle of incidence with a scanned surface when a beam output from a laser is scanned on the scanned surface via a scanning optical system,

said correction method comprising the steps of:
correcting a current value exceeding a threshold current part having a current value in the vicinity in a spontaneous emission area of an extrapolated point which is an intersection with an axis when a linear part corresponding to a laser emission area in the driving current-to-output beam luminous energy characteristic of said laser is extrapolated up to the axis showing that luminous energy is zero with a correction value for correcting the variation of an output beam according to a beam position or an angle of incidence with the scanned surface;
and
driving said laser based upon the result of the correction and the threshold current.

1 more element

A laser driving apparatus for and generating supply current modulated according to image data and driving a semiconductor laser for emitting a laser beam having luminous energy according to supply current by the supply current for scanning a scanned surface via a scanning optical system,

said laser driving apparatus comprising:
a modulation current source to which a predetermined gain control signal and image data are input for outputting modulation current which composes a part of the supply current, by which the image data is converted so that it has gain according to the gain control signal and which is modulated according to the image data;
a threshold current source for outputting threshold current included in the modulation current and the supply current according to a predetermined current control signal;
and
an operation section for generating the gain control signal by multiplying a gain set value which functions as the criterion of the gain of the modulation current source by a correction value according to a beam position or an angle of incidence varying according to scanning with the scanned surface of a laser beam emitted from said semiconductor laser, and generating the current control signal to control so that threshold current output from said threshold current source is a current value in the vicinity in a spontaneous emission area of an extrapolated point which is an intersection with an axis when a linear part corresponding to a laser emission area in the supply current-to-output beam luminous energy characteristic of said semiconductor laser is extrapolated up to the axis showing that luminous energy is zero.

2 more elements

A laser driving apparatus for generating supply current modulated according to image data and driving a semiconductor laser for emitting a laser beam having luminous energy according to the supply current for scanning a scanned surface via a scanning optical system by the supply current,

said laser driving apparatus comprising:
a modulation current source to which a predetermined gain control value and image data are input for outputting modulation current which composes a part of the supply current, by which the image data is converted so that it has gain according to the gain control value and which is modulated according to the image data;
gain correction means for generating the gain control value by multiplying a gain set value which functions as the criterion of the gain of said modulation current source by a correction value according to a beam position or an angle of incidence varying according to scanning with the scanned surface of a laser beam emitted from said semiconductor laser and transmitting the gain control value to said modulation current source;
a threshold current source for generating threshold current according to a current control value and composing the modulation current and the supply current;
monitor value generation means for generating a monitor value by adding a first monitor value to which a predetermined set value is converted so that it has gain according to the gain control value and a second monitor value according to the current control value;
current control value generation means to which an emission luminous energy monitoring signal for monitoring the emission luminous energy of said semiconductor laser and a predetermined first reference value are input for generating the current control value so that said semiconductor laser emits a beam having emission luminous energy corresponding to the first reference value;
gain set value generation means to which a monitor value generated by said monitor value generation means and a predetermined second reference value are input for generating the gain set value so that a monitor value corresponding to the second reference value is generated by said monitor value generation means;
first sample-hold means which can be switched to a through state in which input is output as it is and to a hold state in which a value the input of which is sample-held is output for supplying a current control value generated by said current control value generation means as it is in the through state and with the current control value held in the hold state to said bias current source and said monitor value generation means;
and
second sample-hold means which can be switched to a through state in which input is output as it is and to a hold state in which a value the input of which is sample-held is output for supplying a gain set value generated by said gain set value generation means as it is in the through state and with the gain set value held in the hold state to said gain correction means and said monitor value generation means, wherein
said laser driving apparatus is provided with:
a first mode for keeping said first and second sample-hold means through and controlling the gain set value and the current control value using a correction value fixed in said gain correction means;
and
a second mode for keeping said first and second sample-hold means sample-held, generating the gain control value using a correction value according to the angle of incidence in said gain correction means and outputting driving current by which image data is converted so that the image data has gain according to the gain control value in said driving current source and which is modulated according to the image data.

11 more elements

A laser beam scanner for scanning a predetermined scanned surface by a laser beam holding image information,

said laser beam scanner comprising:
a semiconductor laser for emitting a laser beam having luminous energy according to supply current;
a laser driving circuit for generating supply current modulated according to image data and driving said semiconductor laser by the supply current;
and
a scanning optical system for helping a laser beam emitted from said semiconductor laser to scan the predetermined scanned surface, wherein:
said laser driving circuit comprises:
generation means for generating a correction value for correcting the variation of an output beam according to an angle of incidence with the scanned surface;
multiplication means for multiplying a reference value by a correction value from said generation means;
first generation means with a constant current source the current value of which is controlled based upon the result of the multiplication by said multiplication means, said first generation means being for generating modulation current acquired by modulating current flowing in said constant current source according to the image data;
second generation means for generating threshold current having a current value in the vicinity in a spontaneous emission area of an extrapolated point which is an intersection with an axis when a linear part corresponding to a laser emission area in the driving current-to-output beam luminous energy characteristic of said laser is extrapolated up to the axis showing that luminous energy is zero;
and
addition means for driving a laser based upon current generated from the first and second current sources.

9 more elements

A laser driving method for generating supply current modulated according to image data and driving a semiconductor laser for emitting a laser beam having luminous energy according to supply current by the supply current for scanning a scanned surface via a scanning optical system,

said laser driving method comprising the steps of:
modulation in which a predetermined gain control signal and image data are input for outputting modulation current which composes a part of the supply current, by which the image data is converted so that it has gain according to the gain control signal and which is modulated according to the image data;
outputting threshold current included in the modulation current and the supply current according to a predetermined current control signal;
and
generating the gain control signal by multiplying a gain set value which functions as the criterion of the gain of said modulation step by a correction value according to an angle of incidence varying according to scanning with the scanned surface of a laser beam emitted from said semiconductor laser, and
generating the current control signal to control so that threshold current output from said threshold current source is a current value in the vicinity in a spontaneous emission area of an extrapolated point which is an intersection with an axis when a linear part corresponding to a laser emission area in the supply current-to-output beam luminous energy characteristic of said semiconductor laser is extrapolated up to the axis showing that luminous energy is zero.

3 more elements

A laser driving method for generating supply current modulated according to image data and driving a semiconductor laser for emitting a laser beam having luminous energy according to the supply current for scanning a scanned surface via a scanning optical system by the supply current,

said laser driving method comprising the steps of:
outputting modulation current which composes a part of the supply current by a modulation current source to which a predetermined gain control value and image data are input, by which the image data is converted so that it has gain according to the gain control value and which is modulated according to the image data;
generating the gain control value by gain correction means by multiplying a gain set value which functions as the criterion of the gain of said modulation current source by a correction value according to an angle of incidence varying according to scanning with the scanned surface of a laser beam emitted from said semiconductor laser and transmitting the gain control value to said modulation current source by gain correction means;
generating threshold current by a threshold current source according to a current control value and composing the modulation current and the supply current;
generating a monitor value by monitor value generation means by adding a first monitor value to which a predetermined set value is converted so that it has gain according to the gain control value and a second monitor value according to the current control value;
generating the current control value by current control value generation means to which an emission luminous energy monitoring signal for monitoring the emission luminous energy of said semiconductor laser and a predetermined first reference value are input so that said semiconductor laser emits a beam having emission luminous energy corresponding to the first reference value;
generating the gain set value so that a monitor value corresponding to the second reference value is generated by said monitor value generation means by gain set value generation means to which a monitor value generated by said monitor value generation means and a predetermined second reference value are input;
supplying a current control value generated by said current control value generation means as it is in the through state and with the current control value held in the hold state to said bias current source and said monitor value generation means, by first sample-hold means capable to be switched to a through state in which input is output as it is and to a hold state in which a value the input of which is sample-held is output;
and
supplying a gain set value generated by said gain set value generation means as it is in the through state and with the gain set value held in the hold state to said gain correction means and said monitor value generation means, by second sample-hold means capable to switched to a through state in which input is output as it is and to a hold state in which a value the input of which is sample-held is output, wherein
said laser driving apparatus utilizes:
a first mode for keeping said first and second sample-hold means through and controlling the gain set value and the current control value using a correction value fixed in said gain correction means;
and
a second mode for keeping said first and second sample-hold means sample-held, generating the gain control value using a correction value according to the angle of incidence in said gain correction means and outputting driving current by which image data is converted so that the image data has gain according to the gain control value in said driving current source and which is modulated according to the image data.

11 more elements

A laser beam scanning method for scanning a predetermined scanned surface by a laser beam holding image information,

said laser beam scanning method comprising the steps of:
emitting a laser beam having luminous energy according to supply current by a semiconductor laser;
generating supply current modulated according to image data and driving said semiconductor laser by the supply current by a laser driving circuit;
and
scanning the predetermined scanned surface by a scanning optical system for helping a laser beam emitted from said semiconductor laser, wherein:
said semiconductor laser driving method comprises the steps of:
generating a correction value for correcting the variation of an output beam according to an angle of incidence with the scanned surface by generation means;
multiplying a reference value by a correction value from said generation means by multiplication means;
generating modulation current acquired by modulating current flowing in said constant current source according to the image data by first generation means with a constant current source the current value of which is controlled based upon the result of the multiplication by said multiplication means, by said first generation means;
generating threshold current having a current value in the vicinity in a spontaneous emission area of an extrapolated point which is an intersection with an axis when a linear part corresponding to a laser emission area in the driving current-to-output beam luminous energy characteristic of said laser is extrapolated up to the axis showing that luminous energy is zero, by second generation means;
and
driving a laser based upon current generated from said first and second current sources by addition means.

9 more elements

Dependencies are inferred from the claim text.

Laser beam luminous energy correction method, laser driving apparatus, laser beam scanner and image recording device

Life of this patent

Laser beam luminous energy correction method, laser driving apparatus, laser beam scanner and image recording device

Life of this patent

Abstract

Claims23