JPH09193451A - Light scanner for image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to suitably and uniformly control a weak exposure part over the entire surface by sensing the weak exposure part potential of the entire photosensitive member and controlling an exposure light source when the entire member is the weak exposure part in the member formed with an electrostatic latent image made of a non-exposure part, the weak exposure part and strong exposure part thereon. SOLUTION: The light emitted from a light source 1 such as a semiconductor laser is deflected and scanned by a rotary polygonal mirror 4 via a collimator lens 2 and a cylindrical lens 3, passed through an Fθ lens 5 and focused on a photosensitive member 6 charged by a charger 20. At this time, the surface potentials on the member 6 after the emission are sensed by surface potential sensors 21 to become weak exposure part potential sensing means. When the potential on the member 6 is sensed in an intermediate potential sensing mode, the position of the member 6 is also sensed simultaneously, and the potential distribution of the entire member is input to a memory. It is calculated by an arithmetic circuit based on the data, and the intensity of the source 1 is controlled so that the potentials sensed by the sensors 21 become constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device of an image forming apparatus.

[0002]

2. Description of the Related Art FIG. 2 shows an optical scanning device of a conventional image forming apparatus. The light emitted from the semiconductor laser light source 1 is made into parallel light by the collimator lens 2, passes through the cylinder lens 3 provided for correcting the surface tilt of the rotary polygon mirror 4, and is deflected and scanned by the rotary polygon mirror 4. . After this, the Fθ lens 5
Thus, an image is formed on the photoconductor 6 charged by the charger 20. The intensity of the laser light is modulated by the image data, and an electrostatic latent image is formed on the photoconductor 6. It is known that the light reflectance of parts such as a rotating polygon mirror and an Fθ lens changes depending on the incident angle α as shown in FIG. In general, the reflectance of light is higher when α is larger than when it is small. That is, in the case of a transparent optical component such as an Fθ lens, the light transmittance is lower when α is larger than when it is small. In addition, the light transmittance may change depending on the dust attached to the optical components, the deflection angle of the optical scanning device, and the like.

In the conventional optical scanning device as shown in FIG. 2 due to various reasons as described above, the intensity of the light irradiated on the photosensitive member changes depending on the deflection angle. Therefore, the surface potential in the scanning direction is not uniform. In addition, the surface potential is not uniform due to variations in the sensitivity of the photoconductor in the scanning direction, variations in charging ability, variations in charging of the charger 20, and unevenness.

As one of the image forming methods, an electrostatic latent image composed of a non-exposed portion, a weakly exposed portion and a strongly exposed portion is formed on a uniformly charged photoreceptor, and the non-exposed portion and the strong exposed portion are formed. There is a system of forming a visible image by supplying a developer to the area.

[0005]

In this system,
If the potential of the weakly exposed portion corresponding to the background portion of the printed matter fluctuates, the developer will be attached to the background portion, which will seriously affect the print quality.

An object of the present invention is to provide an optical scanning device of an image forming apparatus capable of appropriately and uniformly controlling a weakly exposed portion over the entire surface of a photosensitive member.

[0007]

The above object is to form an electrostatic latent image consisting of a non-exposed portion, a weakly exposed portion and a strongly exposed portion on a uniformly charged photoreceptor, and to form the non-exposed portion and the strong exposed portion. In a light scanning device of an image forming apparatus that supplies a developer to a portion to form a visible image, a weak exposure for detecting a weakly exposed portion potential of the entire photosensitive body when the entire photosensitive body is a weakly exposed portion Part potential detection means, storage means for storing the detection data of the weak exposure part potential detection means, and arithmetic means for controlling the light output of the exposure light source so that the weak exposure part potentials are appropriate and uniform. It is achieved by

[0008]

1 is a schematic configuration diagram showing an embodiment of an optical scanning device of the present invention. Light emitted from a light source 1 such as a semiconductor laser passes through a collimator lens 2 to be collimated, and then is deflected and scanned by a rotary polygon mirror 4 through a cylinder lens 3, passes through an Fθ lens 5, and is charged by a charger 20. An image is formed on the formed photoconductor 6. There are a plurality of surface potential sensors 21 serving as weakly exposed portion potential detection means, and they are arranged side by side in the scanning direction. This is for detecting the surface potential on the photoconductor 6 after irradiation with light. In the weak exposure portion potential control mode, the semiconductor laser 1 is turned on to detect the entire weak exposure portion potential on the photoconductor 6. The weakly exposed portion potential is detected when the printer is initially operating or when the printer is temporarily stopped, such as when toner is replenished.

Next, the flow of the weakly exposed portion potential (hereinafter referred to as "intermediate potential") control will be described. In the intermediate potential detection mode, the semiconductor laser is turned on and a plurality of surface potential sensors on the photoconductor detect the intermediate potential. At the same time, the position of the photoconductor is also detected by the sensor 23, and the intermediate potential distribution of the entire photoconductor is stored in the memory serving as a storage unit. An example of a certain scanning direction in this memory is shown at 8 in FIG. In the case of this example, the intermediate potential is high in the central portion of the photoconductor and low in the peripheral portion.
After that, the arithmetic circuit calculates based on this data. The light intensity of the light source 1 is controlled so that the intermediate potential detected by the surface potential sensor 21 becomes appropriate and constant. In controlling the light intensity, the optical output of the semiconductor laser is increased when the detected intermediate potential is higher than a predetermined value, and the optical output of the semiconductor laser is reduced when the detected intermediate potential is lower than the predetermined value, and It should be set to an appropriate value.

The optical output of the first corrected semiconductor laser,
When the potential on the photoconductor is lowered, it is detected again by the surface potential sensor, and the optical output of the semiconductor laser is increased when the detected intermediate potential is higher than the predetermined value. The light output of the semiconductor laser in a small place is reduced and set to an appropriate value.
This is repeated, and it is optimal when there is no change in the intermediate potential before and after correction. The calculation result of this example is shown in 9 of FIG. Reference numeral 9 in FIG. 4 denotes the light output of the semiconductor laser alone, and in this example, the light intensity is set to be large in the center and small in the periphery. The intermediate potential after this correction has an appropriate and constant value irrespective of the scanning angle of view, as indicated by 10 in FIG. If the semiconductor laser controller controls the output of the semiconductor laser based on the calculation result and the print data, an optical scanning device in which the intermediate potential does not change depending on the scanning angle of view can be obtained.

Next, another embodiment of the present invention will be described with reference to FIG. This embodiment differs from the previous embodiments in that the surface potential sensor is single. Surface potential sensor 2
2 moves in the direction of arrow 12 to detect the surface potential of the entire scanning area. At the same time, the position of the sensor 22 is detected by the position sensor 24. The subsequent processing can be realized in the same manner as in the previous embodiment, so the description thereof will be omitted.

[0012]

According to the present invention, the weakly exposed portion potential of the entire photoconductor is detected by the weakly exposed portion potential detecting means, and the weakly exposed portion potential is made appropriate and uniform based on the detection data of the weakly exposed portion potential detecting means. Therefore, the light output of the exposure light source is controlled so that the variation in the potential of the weakly exposed portion can be eliminated, and the optical scanning device of the high-quality image forming apparatus in which the developer does not adhere to the background portion is provided. You can

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a conventional example.

FIG. 3 is an explanatory diagram showing how light is reflected.

FIG. 4 is an explanatory diagram showing a relationship between an intermediate potential, a scanning angle of view, and light intensity.

FIG. 5 is a schematic configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

1 is a light source, 2 is a collimator lens, 3 is a cylinder lens, 4 is a rotary polygon mirror, 5 is an Fθ lens, 6 is a photoconductor, 2
Reference numeral 0 is a charger, 21 and 22 are surface potential sensors, 23 is a rotational position sensor, and 24 is a position sensor.

Claims (4)

[Claims] 1. An electrostatic latent image comprising a non-exposed portion, a weakly exposed portion and a strongly exposed portion is formed on a uniformly charged photosensitive member, and a developer is supplied to the non-exposed portion and the strongly exposed portion. In an optical scanning device of an image forming apparatus for forming a visible image, a weakly exposed portion potential detecting means for detecting a weakly exposed portion potential of the entire photosensitive body when the entire photosensitive body is a weakly exposed portion; An image forming apparatus comprising: a storage unit that stores detection data of the exposure unit potential detection unit; and a calculation unit that controls the light output of the exposure light source so that the weak exposure unit potentials are appropriate and uniform. Optical scanning device. 2. The optical scanning device of an image forming apparatus according to claim 1, wherein a plurality of the weakly exposed portion potential detecting means are provided over the entire scanning region on the photosensitive member. 3. The light for an image forming apparatus according to claim 1, wherein the weakly exposed portion potential detecting means is provided singly, and the weakly exposed portion potential detecting means is provided so as to be movable in the scanning direction. Scanning device. 4. The optical scanning device for an image forming apparatus according to claim 1, wherein the weakly exposed portion potential is detected when the image forming apparatus is not printing.