US 10,520,848 B2Granted

Image forming apparatus with variable light emission amounts

AssigneeCanon Kabushiki Kaisha

InventorsSatoshi Ishida, Takeshi Shimba, Tatsuya Hotogi

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Abstract

When a photosensitive member and a developing portion are in a separation state and in a start-up period, a first light emission is performed in an image region and a non-image region. When light is detected at least twice during a period when the first light emission is being performed, a second light emission is performed in the non-image region. When a prescribed period of time has elapsed from the start of the second light emission, a third light emission is performed in the image region in a third light emission amount that is smaller than a second light emission amount during a period in which the photosensitive member makes at least one revolution. After the third light emission is performed, the photosensitive member and the developing portion are switched to a contact state.

Claims20

Dependent claims

An image forming apparatus, comprising:

a photosensitive member;
a developing portion configured to switch between a contact state where the developing portion comes into contact with the photosensitive member and a separation state where the developing portion separates from the photosensitive member, and develop a toner image on the photosensitive member in the contact state;
an irradiating portion configured to irradiate light;
a rotating polygon mirror configured to reflect light irradiated from the irradiating portion and scan an image region and a non-image region on the photosensitive member;
a detecting portion configured to detect light reflected by the rotating polygon mirror;
and
a control portion configured to control so that light is irradiated from the irradiating portion in a first light emission amount for forming an electrostatic latent image in an image portion and in a second light emission amount for controlling a potential of a non-image portion, the second light emission amount being smaller than the first light emission amount, wherein
the control portion controls so that:
when the photosensitive member and the developing portion are in the separation state, and in a start-up period in which a rotational speed of the rotating polygon mirror is controlled such that the rotating polygon mirror rotates at a prescribed rotational speed, a first light emission is performed in which the irradiating portion is caused to scan the image region and the non-image region;
when light is detected at least twice by the detecting portion during a first period when the first light emission is being performed, a second light emission is performed in which the irradiating portion is caused to scan the non-image region;
when a prescribed period of time has elapsed from the start of the second light emission, a third light emission is performed in which the image region is scanned in a third light emission amount that is smaller than the second light emission amount during a second period in which the photosensitive member makes at least one revolution;
and
after the third light emission is performed, the photosensitive member and the developing portion are switched to the contact state.

10 more elements

An image forming apparatus, comprising:

an image bearing member configured to be rotationally driven;
an irradiating portion which has a rotating polygon mirror that reflects light emitted from a light source toward the image bearing member and configured to irradiate light from the light source to the image bearing member to form a latent image;
a control portion configured to control so as to cause light from the light source to be irradiated to the image bearing member in a first light emission amount for forming the latent image in an image portion and in a second light emission amount for controlling a potential of a non-image portion, the second light emission amount being smaller than the first light emission amount;
and
an acquiring portion configured to acquire information related to a rotational speed of the rotating polygon mirror and a rotational speed of the image bearing member, wherein
the control portion determines the second light emission amount that is emitted from the light source in a start-up period of the rotating polygon mirror performed prior to image formation, based on a correspondence relationship between information related to the rotational speed of the rotating polygon mirror and the rotational speed of the image bearing member acquired by the acquiring portion, and the second light emission amount.

3 more elements

Dependencies are inferred from the claim text.