JPH02120062A - Image forming device - Google Patents

Abstract

PURPOSE:To form an image which is excellent in gradation characteristic precisely at low cost by a method wherein a plurality of light beams are established at specific laser power from a simple light source according to a number of gradation, and the same picture element area on a recording medium is irradiated thereby. CONSTITUTION:Laser beams 2, 3 radiated from a semiconductor laser 1 are converted to parallel light with a collimator lens 8, which are parallel on a same scanning line irradiated to a photosensible drum 7. In the case where laser beams 2, 3 of different power are outputted from the semiconductor laser 1, an electrostatic image can be formed on the photosensible drum 7 at a light quantity level, and 2<n> kinds of gradation expression become practicable to the number of light beams (n). When, for instance, density level signals which are weighted and diffused around, are recorded with the laser beams 2, 3, feeling roughness of a high light part of a recording image can be removed. Further, in the case where gradation image information is sent or received via communication medium, since a signal of which a pulse width is modulated is not required to be stored, the gradation image information can be sent or received at low coat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus that reads a density level signal with gradations and records an image with gradations.

(Prior Art) Conventionally, in this type of device, gradation is determined based on a digitalized image signal when forming an image with a laser beam printer, etc., as shown in Japanese Patent Laid-Open No. 183663/1983, for example. In order to obtain a pulse width modulated signal, the digital signal is converted to an analog signal as shown in Figure 5, and this converted signal is compared with a periodic pattern signal such as a triangular wave. Image recording was performed using a method that generated images.

FIG. 5 is a characteristic diagram showing the principle of conventional gradation signal generation.
The horizontal movement indicates time, and the vertical axis indicates the concentration level or driving potential.

In this figure, reference numeral 51 indicates a pattern signal, and the image density level signal 52 is waveform-shaped using this pattern signal 51 to generate a laser driver drive signal 53.

As can be seen from this figure, the image density level signal 52 is pulse width modulated by the pattern signal 51, and the laser driver drive signal 53 is input to a semiconductor laser (not shown) to record a gradation image.

[Problem to be solved by the invention]

However, in the above conventional example, the gradation is produced by a signal subjected to pulse width modulation, so in order to obtain a gradation signal with an increased number of gradations, the pulse width must be adjusted to match the gradation. It is necessary to narrow down the However, there are technical limits to narrowing down the beam diameter of the laser beam, and there are problems such as difficulty in controlling the drive current of the semiconductor laser.

Furthermore, since the sensitivity characteristics of the recording medium recorded by the laser beam vary depending on the laser beam spot, there is a problem that it is difficult to record an image with a desired gradation.

Furthermore, if the gradation signal is, for example, 256 gradations, it is necessary to send out information for 256 gradations for each pixel, which requires a large capacity memory and increases costs.

In addition, as another gradation signal generation device, Japanese Patent Application Laid-Open No. 62-1
As shown in Japanese Patent No. 067002, an error diffusion method has been used.

In the error diffusion method, in order to produce gradations, the density at a certain position is diffused by adding weight to the surrounding areas, and an image is formed by recording with or without recording as a binary signal.

For this reason, areas with high density are always recorded, so
Although the resolution is excellent, on the other hand, areas with low density are recorded as binary signals only after the diffused signals from the surroundings are integrated, so the roughness in the highlighted areas becomes noticeable in the output image. There was a problem.

This invention was made in order to solve the above-mentioned problems, and it is possible to set a plurality of light beams from a single light source to a predetermined laser power in accordance with the number of gradations, so that the same pixel on a recording medium can be illuminated. It is an object of the present invention to provide an image forming apparatus that can accurately form images with excellent gradation characteristics at low cost by irradiating a region.

[Means to solve the problem]

An image forming apparatus according to the present invention includes a light beam irradiation means that irradiates n light beams with different intensities based on manually inputted gradation image information, and a light beam irradiation means that irradiates n light beams with different intensities. A scanning exposure means for scanning and exposing the same position of the recording medium n times with the light beam of the recording medium is provided.

[Effect]

In this invention, when n light beams with different intensities are irradiated based on the gradation image information input from the light beam irradiation means, the scanning exposure means irradiates the recording medium with n light beams with different intensities. By exposing the same position n times,
An electrostatic latent image having gradation is formed on a recording medium.

〔Example〕

FIG. 1 is a plan view showing an example of an image forming apparatus according to an embodiment of the present invention, and 1 is a semiconductor laser serving as a light beam irradiation means of the present invention. It is composed of a monolithic semiconductor laser as shown, and irradiates, for example, two laser beams 2 and 3 with different intensities according to a drive signal output from a controller 9 based on input gradation image information. Note that the laser beam 2.3 irradiated by the semiconductor laser 1
is converted into parallel light by the collimator lens 8. A cylindrical lens 4 focuses each of the laser beams 2.3 on each mirror surface of the polygon mirror 5 perpendicularly.

The polygon mirror 5 is rotated at a constant speed by a scanner motor (not shown), and the laser beams 2.3 are focused on a scanning line at the same position on a photosensitive drum 7, which rotates at a constant speed, through an imaging lens 6 having fθ characteristics. image. That is, the laser beam 2.3 is irradiated parallel to the photosensitive drum 7 and on the same scanning line.

Incidentally, each of the above 4 to 6 constitutes the scanning exposure means of the present invention, and when n light beams with different powers are irradiated from the semiconductor laser 1 based on the input gradation image information, n light beams with different powers are irradiated by the semiconductor laser 1. A plurality of light beams are scanned and exposed onto the same line of the recording medium, and an electrostatic latent image having gradation is formed on the photosensitive drum 7 which becomes the recording medium.

FIG. 2(a) is a characteristic diagram illustrating the power level irradiated by the semiconductor laser 1 shown in FIG. 1, where the vertical axis shows the power level and the horizontal axis shows the laser beam number.

FIG. 2(b) is a characteristic diagram illustrating the combination of a plurality of light beams with different powers emitted from the semiconductor laser 1 shown in FIG. 1, where the vertical axis shows the output level and the horizontal axis shows the light amount. Indicates the combination number (laser beam number used), "0" indicates that each of the laser beams 2 and 3 is off, "1" corresponds to, for example, a state where only laser beam 3 is lit, and "2" indicates, for example, This corresponds to a state in which only the laser beam 2 is lit, and "3" corresponds to a state in which both laser beams 2.3 are lit.

As can be seen from these figures, for example, when the semiconductor laser 1 outputs laser beams 2.3 with different powers, an electrostatic latent image can be formed on the photosensitive drum 7 at four combinations of light intensity levels. In addition, if expressed in a general form, 2° gradation expression (n≦number of gradations≦2n) is possible for the number n of light beams.

For example, when a density level signal weighted and diffused around the surrounding area was recorded by the laser beam 2.3, it was possible to eliminate the roughness in the highlight portion of the recorded image caused by the conventional error diffusion method.

Furthermore, when transmitting and receiving gradation image information via a communication medium, there is no need to store pulse width modulated signals, so that gradation image information can be transmitted and received at low cost.

FIG. 3(a) is a characteristic diagram illustrating the power level in an image forming apparatus showing another embodiment of the present invention, and particularly corresponds to the case where image recording is performed using three beams having different amounts of light. In this figure, the vertical axis shows the power level, and the horizontal axis shows the laser beam number.

Figure 3 (b) is a characteristic diagram explaining the combination of multiple light beams with different powers, where the vertical axis shows the output level and the horizontal axis shows the light intensity combination number (laser beam number used).
"0" indicates that all three laser beams are off, "1" corresponds to, for example, only the second laser beam is lit, and "2" corresponds to, for example, only the second laser beam is lit. Corresponding to the state, rl+2J corresponds to a state in which both the first and second laser beams are turned on, "3" corresponds to a state in which the third laser beam is turned on, and rl+3'' corresponds to a state in which the first and second laser beams are both turned on, for example. Corresponds to the state in which both the third laser beams are turned on, for example, r2+3J is the second laser beam.
For example, "1+2+3" corresponds to a state in which all of the first to third laser beams are lit.

As can be seen from these figures, when the number of scanning beams is three, it is possible to generate signals with 23 different output values.

Note that the same applies to four or more.

In the above embodiment, a case has been described in which the laser beam 2.3 emitted from the semiconductor laser 1 is a light beam parallel to the scanning direction. As shown in (a), the speed can be increased by simultaneously scanning lines in which the laser beams 11, 12° 13 (having the output level characteristics shown in Fig. 4 (b)) are arranged in a direction intersecting the scanning direction. It becomes possible,
Moreover, image recording can be performed using a four-value output level signal.

〔Effect of the invention〕

As explained above, the present invention includes a light beam irradiation means that irradiates n light beams with different powers based on manually generated gradation image information, and a light beam irradiation means that irradiates n light beams with different powers. scanning exposure means for scanning and exposing the same position of the recording medium n times with a light beam of
Compared to conventional gradation image formation using pulse width modulation, the number of gradations can be significantly increased with a simpler circuit configuration. Therefore, excellent effects such as formation of an image with excellent gradation characteristics in detail at low cost and the ability to transmit and receive gradation image information at low cost are achieved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of an image forming apparatus showing an embodiment of the present invention, FIG. 2(a) is a characteristic diagram illustrating the power level irradiated by the semiconductor laser shown in FIG. FIG. 2(b) is a characteristic diagram illustrating the combination of a plurality of light beams with different powers irradiated by the semiconductor laser shown in FIG. 1, and FIG. 3(a) is a characteristic diagram showing another embodiment of the present invention. a characteristic diagram illustrating power levels in the image forming apparatus shown;
FIG. 4(b) is a characteristic diagram illustrating a combination of a plurality of light beams with different powers, and FIG. 4(a) is a diagram illustrating a light beam scanning arrangement of an image forming apparatus according to another embodiment of the present invention. 4(b) are characteristic diagrams illustrating the output level characteristics of each beam, and FIG. 5 is a characteristic diagram illustrating the conventional gray scale signal generation principle. In the figure, 1 is a semiconductor laser, 2 and 3 are laser beams, 4 is a cylindrical lens, 5 is a polygon mirror, 6 is an imaging lens, 7 is a photosensitive drum, 8 is a collimator lens, and 9 is a controller. Bencho Okai ゛゛＜Mimi

Claims (1)

[Claims] In an image forming device that forms an electrostatic latent image using a light beam exposed to a recording medium, and records the image on the recording medium by developing this electrostatic latent image, the intensity is adjusted based on the input gradation image information. a light beam irradiation means for irradiating n different light beams; and a scanning exposure means for scanning and exposing the same position on the recording medium n times with the n light beams of different intensities irradiated by the light beam irradiation means. An image forming apparatus comprising: