Method and apparatus for recording a flat field image

A flat field image printing apparatus comprising:

• a light source responsive to an image modulated signal and producing an image modulated light beam;
• a beam deflector supported for rotary motion to deflect said image modulated light beam onto an image recording medium in response to said rotary motion;
• and
• a lens assembly configured to convert said deflected image modulated light beam into an achromatic focused beam spot which moves repeatedly in a first scan direction and over a range of scan angles to provide a highly resolved printed image across said recording medium,
• wherein said lens assembly comprises
• a first lens having a negative power,
• a second lens having a positive power, and
• a third lens having a positive power,
• wherein said first, second and third lenses are arranged in the order from the object to tile image side and satisfy the following formulae (1) to (6)
• −3.6<1<−3.0 (1)
• 1.6<2<2.0 (2)
• 1.5<3<1.8 (3)
• ν1<34 (4)
• 44<v2<61 (5)
• 37<v3<51 (6)
• where n is the power of the nth lens with respect to the total power of the lens assembly and vn represents the Abbe dispersion number of the nth lens.

A flat field image printing apparatus comprising:

• a light source responsive to an image modulated signal and producing an image modulated light beam;
• a beam deflector supported for rotary motion to deflect said image modulated light beam onto an image recording medium in response to said rotary motion;
• and
• a lens assembly configured to convert said deflected image modulated light beam into an achromatic focused beam spot which moves repeatedly in a first scan direction and over a range of scan angles to provide a highly resolved printed image across said recording medium,
• wherein said lens assembly comprises
• a first lens having a negative power and a refractive index in the range of 1.64 to 1.85,
• a second lens having a positive power and a refractive index in the range of 1.60 to 1.75,
• a third lens having a positive power and a refractive index in the range of 1.65 to 1.75, and
• wherein said first, second and third lenses are arranged in the order from the object to the image side.

An f-theta lens assembly configured to convert an image modulated light beam into an achromatic focused beam spot which moves repeatedly in a first scan direction and over a range of scan angles to provide a highly resolved image comprising

• a first lens having a negative power,
• a second lens having a positive power, and
• a third lens having a positive power,
• wherein said first, second and third lenses are arranged in the order from object to image side and satisfy the following formulae (1) to (6)
• −3.6<ø1<−3.0 (1)
• 1.6<ø2<2.0 (2)
• 1.5<ø3<1.8 (3)
• ν1<34 (4)
• 44<ν2<61 (5)
• 37<ν3<51 (6)
• where øn is the power of the nth lens with respect to the total power of the lens assembly and νn represents the Abbe dispersion number of the nth lens.

A high-speed flat field image printing apparatus comprising:

• a plurality of light sources responsive to an image modulated signal and producing a plurality of image modulated light beams having a plurality of wavelengths;
• a beam deflector supported for rotary motion to deflect said plurality of image modulated light beams onto an image recording medium in response to said rotary motion;
• and
• a lens assembly configured to convert said plurality of deflected image modulated light beams into a plurality of achromatic focused beam spots which move repeatedly in a first scan direction and over a range of scan angles to provide a highly resolved printed image across said recording medium.

A high-speed flat field image printing apparatus comprising:

• a plurality of light sources responsive to an image modulated signal and producing a plurality of image modulated light beams having a plurality of wavelengths;
• a beam deflector supported for rotary motion to deflect said plurality of image modulated light beams onto an image recording medium in response to said rotary motion;
• and
• a lens assembly configured to convert said plurality of deflected image modulated light beams into a plurality of achromatic focused beam spots which move repeatedly in a first scan direction and over a range of scan angles to provide a highly resolved printed image across said recording medium,
• wherein said lens assembly comprises
• a first lens having a negative power,
• a second lens having a positive power, and
• a third lens having a positive power,
• wherein said first, second and third lenses are arranged in the order from the object to the image side and satisfy the following formulae (1) to (6)
• −3.6<1<−3.0 (1)
• 1.6<2<2.0 (2)
• 1.5<3<1.8 (3)
• v1<34 (4)
• 44<v2<61 (5)
• 37<v3<51 (6)
• where n is the power of the nth lens with respect to the total power of the lens assembly and vn represents the Abbe dispersion number of the nth lens.

A high-speed flat field image printing apparatus comprising:

• a plurality of light sources responsive to an image modulated signal and producing a plurality of image modulated light beams having a plurality of wavelengths;
• a beam deflector supported for rotary motion to deflect said plurality of image modulated light beams onto an image recording medium in response to said rotary motion;
• and
• a lens assembly configured to convert said plurality of deflected image modulated light beams into a plurality of achromatic focused beam spots which move repeatedly in a first scan direction and over a range of scan angles to provide a highly resolved printed image across said recording medium,
• wherein said lens assembly comprises
• a first lens having a negative power and a refractive index in the range of 1.64 to 1.85
• a second lens having a positive power and a refractive index in the range of 1.60 to 1.75, and
• a third lens having a positive power and a refractive index in the range of 1.65 to 1.75,
• wherein said first, second and third lenses are arranged in the order from the object to the image side.

A flat field image printing apparatus comprising:

• a light source responsive to an image modulated signal and producing an image modulated light beam;
• a beam deflector supported for rotary motion to deflect said image modulated light beam onto an image recording medium in response to said rotary motion;
• and
• a f-theta lens assembly configured to convert said deflected image modulated light beam into an achromatic focused beam spot which moves repeatedly in a first scan direction and over a range of scan angles to provide a highly resolved printed image across said recording medium, wherein said f-theta lens assembly is configured to produce an achromatic focused beam spot over a range of wavelengths in the visible and near infrared spectral wavelength range.