Laser printer capable of changing a pixel density

Claim 2

A laser printer for forming an image on a photoreceptor through scanning of a laser beam, that can be modulated based on image data, by scanning means, and capable of changing a pixel density on the photoreceptor, comprising: pixel density change means for changing the pixel density of the image to be formed, by changing a scanning cycle of said scanning means; scanning detection means for detecting a scanning condition of said laser beam based on a predetermined reference cycle according to said changed pixel density and producing a corresponding signal; control means responsive to the scanning detection signal for monitoring the laser printer operation, and means for disabling the effect of the scanning detection means while the pixel density is being changed by the pixel density change means to prevent an erroneous response by the control means.

Claim 3

A laser printer in accordance with claim 1, wherein said scanning detection means comprises density detection means for detecting said changed pixel density, detection cycle change means responsive to an output of detection from said density detection means, for changing the reference cycle for detecting the scanning condition of said laser beam.

Claim 4

A laser printer in accordance with claim 1, wherein emission of said laser beam is forbidden in response to an output of detection from said scanning detection means indicating abnormality in scanning of said laser beam.

Claim 5

A laser printer for forming an image on a photoreceptor through scanning of a laser beam, that can be modulated based on image data, by scanning means, and capable of changing a pixel density on the photodetector, comprising: pixel density change means for changing the pixel density of the image to be formed, by changing a scanning cycle of the scanning means; scanning detection means for detecting a scanning condition of the laser beam based on a predetermined reference cycle according to said changed pixel density, and producing a corresponding signal including: density detection means for detecting the changed pixel density, and detection cycle change means responsive to an output of detection from the density detection means, for changing the reference cycle for detecting the scanning condition of the laser beam, control means responsive to the scanning detection signal for monitoring the laser printer operation; means for disabling the effect of the scanning detection means while the pixel density is being changed by the pixel density change means to prevent an erroneous response by the control means; detection mark formation means for forming a mark for detection of a density of the image by applying the laser beam on the photoreceptor, outside an area where the image is to be formed; image formation control means for controlling conditions for forming the image by detecting a density of the formed mark, and mark formation control means for controlling operation of the detection mark formation means dependent on an operation state of the pixel density change means.

Claim 6

A laser printer for forming an image on a photoreceptor through scanning of a laser beam, that can be modulated based on image data, by scanning means, and capable of changing a pixel density on the photodetector, comprising: pixel density change means for changing the pixel density of the image to be formed, by changing a scanning cycle of the scanning means; scanning detection means for detecting a scanning condition of the laser beam based on a predetermined reference cycle according to said changed pixel density, and producing a corresponding signal including: density detection means for detecting the changed pixel density, and detection cycle change means responsive to an output of detection from the density detection means, for changing the reference cycle for detecting the scanning condition of the laser beam, control means responsive to the scanning detection signal for monitoring the laser printer operation; means for disabling the effect of the scanning detection means while the pixel density is being changed by the pixel density change means to prevent an erroneous response by the control means; detection mark formation means for forming a mark for detection of a density of the image by applying the laser beam on the photoreceptor, outside an area where the image is to be formed; image formation control means for controlling conditions for forming the image by detecting a density of the formed mark, and mark formation control means for controlling operation of the detection mark formation means dependent on an operation state of the pixel density change means.

Claim 7

A laser printer in accordance with claim 1, wherein said scanning means is a polygon mirror to be rotated for receiving said laser beam and outputting the same after reflection thereon, and said pixel density change means changes a rotating speed of said polygon mirror.

Claim 8

A laser printer in accordance with claim 5, wherein forbidding of the detection by said scanning detection means is cancelled when the changed rotating speed of said polygon mirror becomes constant.

Claim 9

A laser printer for forming an image on a photoreceptor through scanning of a laser beam modulated based on image data by scanning means, and being capable of changing a pixel density, comprising: pixel density change means for changing the pixel density of the image to be formed, by changing a scanning cycle of said scanning means, detection mark formation means for forming a mark for detection of a density of said image by applying said laser beam on said photoreceptor, outside an area where said image is to be formed, image formation control means for controlling conditions for forming said image by detecting a density of said formed mark, and mark formation control means for controlling operation of said detection mark formation means dependent on an operation state of said pixel density change means.

Claim 10

A laser printer for forming an image on a photoreceptor through scanning of a laser beam modulated based on image data by scanning means, and being capable of changing a pixel density, comprising: pixel density change means for changing the pixel density of the image to be formed, by changing a scanning cycle of said scanning means, detection mark formation means for forming a mark for detection of a density of said image by applying said laser beam on said photoreceptor, outside an area where said image is to be formed, image formation control means for controlling conditions for forming said image by detecting a density of said formed mark, and mark formation control means for controlling operation of said detection mark formation means dependent on an operation state of said pixel density change means.

Claim 11

A laser printer in accordance with claim 7, wherein said mark formation control means forbids formation of the mark by said detection mark formation means while the pixel density is being changed by said pixel density change means.

Claim 12

A laser printer in accordance with claim 8, further comprising change instructing means for instructing a change of said pixel density, wherein said mark formation control means defers output of an instruction from said change instructing means while said mark is being formed by said detection mark formation means.

Claim 13

A laser printer in accordance with claim 8, wherein said scanning means is a polygon mirror to be rotated for receiving said laser beam and outputting the same after reflection thereon, and said pixel density change means changes a rotating speed of said polygon mirror.

Claim 14

A laser printer in accordance with claim 10, wherein said mark formation control means forbids emission of said laser beam while the rotating speed of said polygon mirror is not constant.

Claim 15

A laser printer in accordance with claim 11, wherein said mark is formed by application of said laser beam through rotation of said polygon mirror.

Claim 16

A laser printer in accordance with claim 9, wherein said scanning means is a polygon mirror to be rotated for receiving said laser beam and outputting the same after reflection thereon, and said pixel density change means changes a rotating speed of said polygon mirror.

Claim 17

A laser printer in accordance with claim 13, wherein said mark formation control means cancels the deferring of said output of the instruction when the rotating speed of said polygon mirror becomes constant.

Claim 18

A laser printer in accordance with claim 14, wherein said mark is formed by application of said laser beam through rotation of said polygon mirror.

Claim 19

A laser printer for forming an image on a photoreceptor through scanning of a laser beam modulated based on image data by scanning means, and being capable of changing a pixel density, comprising: pixel density change means for changing the pixel density of the image to be formed, by changing a scanning cycle of said scanning means, and emission forbidding means for forbidding emission of said laser beam while the pixel density is being changed by said pixel density change means.

Claim 20

A laser printer for forming an image on a photoreceptor through scanning of a laser beam modulated based on image data by scanning means, and being capable of changing a pixel density, comprising: pixel density change means for changing the pixel density of the image to be formed, by changing a scanning cycle of said scanning means, and emission forbidding means for forbidding emission of said laser beam while the pixel density is being changed by said pixel density change means.

Claim 21

A laser printer in accordance with claim 16, wherein said scanning means is a polygon mirror to be rotated for receiving said laser beam and outputting the same after reflection thereon, and said pixel density change means changes a rotating speed of said polygon mirror.

Claim 22

A laser printer in accordance with claim 17, wherein said emission forbidding means forbids emission of said laser beam while the rotating speed of said polygon mirror is not constant.