JP2002292929A - Imaging apparatus, imaging method, program for making computer execute imaging method, and computer readable recording medium with the program recorded therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the image quality of isolate dots regardless of emission characteristics of an LD. SOLUTION: In a driver circuit (LD driver) 100, an LUT part 103 corrects the gradation of inputted image data, a PWM part 104 converts the data to pulse width modulated data, and then a D/A conversion part 105 D/A converts and outputs the data as a driving signal. An isolate dot detection part 106 detects the isolate dot of output data of the LUT part 103, and a power control part 107 executes power modulation to the isolate dot among the driving signal. The power modulation part 107 varies an LD driving current to be outputted to the LD 110 at the detection time of the isolate dot in an increase direction or a decrease direction, thereby variably controlling an emission power of an isolate dot part so that an exposure energy of the isolate dot becomes equal to an exposure energy of continuous dots.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming an image by an electrophotographic method, such as a laser printer, a digital copying machine, and the like. And a computer-readable recording medium on which the program is recorded.

[0002]

2. Description of the Related Art In recent years, image forming units (engine units) of laser printers and digital copiers have been required to have high speed and high image quality. I'm advancing. For such a high speed and high resolution, Japanese Patent Laid-Open Publication No.
(27663321) and JP-A-2000-177.
No. 171 is disclosed.

[0003] Japanese Patent Application Laid-Open No. 2-132459 (Japanese Patent No. 2763)
No. 321) discloses an image forming method for a laser printer of a pulse width (PWM) modulation system.
An object of the present invention is to solve the problem that the latent image is difficult to be developed when the pulse width of the M signal is extremely short and the laser beam barely emits light.

When the toner has a volume average particle diameter of 5 to 9 μm, the carrier resistance is 107 Ω · cm or more, the toner volume average particle diameter is M, and the toner particle diameter is γ, the toner volume distribution is , M / 2 <γ <3 * M / 2
Contains 90% by volume or more of the toner, and 0 <γ <2
The configuration is such that the range of M includes 90% by volume or more of the toner. As a result, it is possible to improve the gradation in a portion where the image density is low and to achieve high image quality.

[0005] The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-177171 discloses an isolated one-dot pattern or one-dot pattern.
The exposure energy density in the case of a dot width line pattern is Ea, and the exposure energy density in the case of every other dot pattern or every other line pattern is Eb.
, The exposure energy is controlled so that Ea> Eb. As a result, it is possible to improve the tone reproducibility of the low density highlight portion including the isolated dot pattern.

[0006]

Problems to be Solved by the Invention
In the configuration of No. 9 (2763321), by using a toner having a small particle diameter, gradation can be secured in a portion where the image density is low, and roughness can be reduced. And the manufacturing process becomes complicated and expensive.

[0007] With the recent increase in the speed of devices and the increase in the density of images, laser diodes (LDs) have been developed.
The repetition frequency of e) is also increased, and the LD itself is required to have high-speed response. FIG. 8 is a light emission characteristic diagram of the LD.
If the response speed of the LD is slower than the LD drive frequency, the rising of light emission is slowed down in both the continuous dots shown in FIG. 8A and the isolated dots shown in FIG. 8B. As a result, the first dot of a continuous dot on one line,
And the exposure energy of the isolated dots is reduced. As a result, as shown by a dotted line in FIG. 8C, problems such as a narrowing of the first dot of a continuous horizontal line and a narrowing of a vertical line formed by one dot as compared with the horizontal line occur.

FIG. 9 is a diagram showing light emission characteristics of an LD having overshoot characteristics. FIG. 9 (a), (c)
FIG. 4 is a diagram showing a light emission characteristic diagram of an LD having no overshoot characteristic and an image forming state. In contrast, FIG.
In the case of an LD having an overshoot at the rising portion of light emission as shown in FIG. 9B, the exposure energy for an isolated dot becomes excessive, and as shown in FIG. There is a problem that the above spatial frequency becomes low.

To solve the above problem, Japanese Patent Laid-Open No. 2000-177
No. 171 discloses a technique that varies the exposure energy for the resolution mode and the dot pattern, but cannot improve the image quality of the rising portion of the light emission. In particular, in order to reduce the diameter of the beam spot on the photoconductor in response to the demand for high resolution, the emission wavelength of the LD is shifting from the conventional vicinity of 780 nm to a red LD near 650 nm on the short wavelength side. Generally, the shorter the oscillation wavelength is, the more the above problem tends to appear.

On the other hand, in order to improve the rising characteristics of light emission, a means for adjusting a bias current (offset light emission) in a region where there is no image can be considered. However, if too much bias current is applied, offset light emission becomes large. Ground stains are likely to occur. Here, the response of LD is
Although the material and chip structure differ depending on the wavelength, output power, and the like, an LD with fast response is expensive. In particular, high-speed laser printers and digital copiers that require multiple beams will significantly increase costs.

The present invention solves the above-mentioned problems, and provides an image forming apparatus and method capable of improving the image quality of an isolated dot regardless of the light emission characteristics of an LD, a program for causing a computer to execute the image forming method, and a recording of the program. It is intended to provide a computer-readable recording medium.

[0012]

In order to achieve the above object, an image forming apparatus according to the first aspect of the present invention scans a light beam emitted from a light emitting element based on input image data to form an image. In an image forming apparatus that forms an image on a carrier, an isolated dot detection unit that detects an isolated dot that is a non-emission dot before and after in the scanning direction of image data, and when an isolated dot is detected by the isolated dot detection unit, And a power control unit for variably controlling the emission power of the isolated dot portion in the drive signal supplied to the light emitting element so that the exposure energy of the isolated dot becomes equal to the exposure energy of the continuous dot.

According to the above configuration, when the isolated dot detection section detects the isolated dot, the power control section controls the drive signal supplied to the light emitting element so that the exposure energy of the isolated dot becomes equal to the exposure energy of the continuous dot. The emission power of the isolated dot portion is variably controlled.

Further, the isolated dot detecting section may be configured to detect the first dot of the continuous light emitting dots as an isolated dot.

According to the above arrangement, the isolated dot detection section detects the first dot of the continuous dot as an isolated dot, and the power control section determines that the exposure energy of the first dot of the continuous dot is equal to or less than the second dot of the continuous dot. The light emission power of the isolated dot portion in the drive signal supplied to the light emitting element is variably controlled so as to be equal to the exposure energy.

The power control section variably controls a driving signal using a correction power value set in advance according to the light emission rising characteristic of the light emitting element. Reduces the light emission power for isolated dots so as to cancel out the overshoot amount of exposure energy, and increases the light emission power for isolated dots so as to cancel out the undershoot amount of exposure energy for light emitting elements having undershoot characteristics. It may be configured to perform variable control.

According to the above configuration, the power control section variably controls the drive signal when detecting an isolated dot. However, for a light emitting element having an overshoot characteristic for each characteristic of the light emitting element, the power control section supplies the overshoot amount of exposure energy. Control is performed to reduce the light emission power for the isolated dot so as to negate it. Further, for a light emitting element having an undershoot characteristic, the light emitting power for the isolated dot is increased so as to cancel out the undershoot amount of exposure energy.

The isolated dot detecting section outputs control information consisting of a data off time until the isolated dot is detected when the isolated dot is detected, and the power control section outputs the control information in accordance with the data off time of the control information. Alternatively, the light emitting power of the isolated dot can be varied.

According to the above configuration, the isolated dot detection section includes:
When an isolated dot is detected, a data off time until the detection of the isolated dot is detected and output as control information. In accordance with the data off time of the input control information, the power control unit varies the light emission power of the isolated dot by taking the variable amount of the light emission power larger than the reference power as the data off time is longer.

Further, the power control section may be configured to vary the emission power of the second and subsequent dots in a stepwise manner when detecting continuous dots.

According to the above configuration, the isolated dot detection section includes:
The emission power for the second and subsequent dots is varied stepwise when detecting continuous dots.

An image forming method according to the present invention is directed to an image forming method for forming an image on an image carrier by scanning a light beam emitted from a light emitting element based on input image data. In the isolated dot portion of the drive signal supplied to the light emitting element, the isolated dot whose front and rear are non-light emitting dots is detected, and when the isolated dot is detected, the exposure energy of the isolated dot becomes equal to the exposure energy of the continuous dot. Is characterized in that the light emission power is variably controlled.

According to the above arrangement, the emission power of the isolated dot portion of the drive signal supplied to the light emitting element is variably controlled so that the exposure energy of the isolated dot becomes equal to the exposure energy of the continuous dot by detecting the isolated dot. .

Further, a configuration may be adopted in which the first dot of the continuous luminescent dots in the image data is detected as an isolated dot.

According to the above configuration, when the first dot of the continuous dot is detected as an isolated dot, the light emission is performed such that the exposure energy of the first dot of the continuous dot becomes equal to the exposure energy of the second and subsequent dots of the continuous dot. The light emission power of the isolated dot portion in the drive signal supplied to the element is variably controlled.

Further, when the isolated dot is detected, the drive signal is variably controlled using a correction power value set in advance according to the light emission rising characteristic of the light emitting element. Reduces the light emission power for isolated dots so as to cancel out the overshoot amount of exposure energy, and increases the light emission power for isolated dots so as to cancel out the undershoot amount of exposure energy for light emitting elements having undershoot characteristics. A configuration for performing variable control is also possible.

According to the above arrangement, when an isolated dot is detected,
For a light emitting element having an overshoot characteristic for each characteristic of the light emitting element, control is performed to reduce the light emitting power for the isolated dot so as to cancel the overshoot amount of exposure energy. Further, for a light emitting element having an undershoot characteristic, the light emitting power for the isolated dot is increased so as to cancel out the undershoot amount of exposure energy.

Further, at the time of detection of the isolated dot, the light emitting power of the isolated dot may be varied according to the data off time until the detection of the isolated dot.

According to the above configuration, when an isolated dot is detected, the data off time up to the detection of the isolated dot is detected, and in accordance with the data off time, the longer the data off time, the more the variable amount of the emission power is compared with the reference power. To make the emission power of the isolated dot variable.

Further, it is also possible to adopt a configuration in which the emission power of the second and subsequent dots is changed stepwise when the continuous dot is detected.

According to the above configuration, when the first dot of the continuous dot is detected as an isolated dot, the light emission is performed so that the exposure energy of the first dot of the continuous dot becomes equal to the exposure energy of the second and subsequent dots of the continuous dot. The light emission power of the isolated dot portion in the drive signal supplied to the element is variably controlled.

A program according to the present invention causes a computer to execute the above method.

The program having the above-described configuration variably controls the light emission power of the light emitting element when an isolated dot is detected by executing a computer program.

Further, a computer-readable recording medium of the present invention is characterized in that the program is recorded.

The computer-readable recording medium having the above configuration variably controls the light emission power of the light emitting element when a program executed by the computer reading detects an isolated dot.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus, an image forming method, a program for causing a computer to execute the image forming method, and a computer-readable recording medium storing the program according to an embodiment of the present invention will be described with reference to the drawings. It will be described with reference to FIG.

FIG. 1 is a block diagram showing the configuration of a driver circuit used in the image forming apparatus of the present invention. The driver circuit (LD driver) 100 generally includes a digital circuit unit 101 and an analog circuit unit 102. The image forming apparatus including the driver circuit 100 forms an image on an image carrier such as a photosensitive drum by scanning a light beam emitted from a light emitting element based on input image data.

The LUT unit 103 of the digital circuit unit 101 stores image data (D0 to D7) having 8-bit gradation.
Is input and output to the PWM unit 104 after gradation correction. The PWM unit 104 converts the grayscale data into pulse width modulation and converts the 5-bit (D0 to D4) pulse width data into D.
/ A conversion section 105. This PWM unit 104
A voltage / frequency converter (VCO) is provided inside, and is configured to perform pulse width modulation (PWM) by controlling clock delay and the like. The analog data that has been D / A converted by the D / A conversion unit 105 is a drive signal of an LD obtained by real-time conversion of a digital input.

The isolated dot detection unit 106 includes the LUT unit 10
Based on the output data of No. 3, an isolated dot and the head of a continuous dot are detected. For the isolated dot, a non-light emitting dot (data off) and a light emitting dot (data on) are determined from input image data, and one light emitting dot is located before and after the light emitting dot (before and after a scanning direction described later).
Is determined as an isolated dot when the dot is a non-light emitting dot.

As for the head of the continuous dot, the head dot (one head dot in the scanning direction) of the continuous light emitting dot after the non-light emitting dot is determined as the head of the continuous dot. The isolated dot detection unit 106 detects the time information from the data off time to the on time of the isolated dot or the leading dot by a timer or the like, together with the detection of the head of the isolated dot or the continuous dot, and the D / A conversion unit 105 , And outputs these control information.

In the following description, the term "isolated dot" refers to both the case where there is no light-emitting dot before and after the dot, and the one of the first dot during light-emitting scanning of continuous dots.

This control information is output, for example, in two bits, and one bit of the two bits is used to indicate whether power modulation is necessary in accordance with the presence or absence of an isolated dot, and the other one bit is used. Therefore, the data off time is assumed to be used. The data off time can be expressed in more stages using not only two bits but also a larger number of bits. The D / A conversion unit 105 performs D / A conversion on the control information output from the isolated dot detection unit 106 and performs power conversion on the power control unit 107.
Variably (correction) output the drive signal.

The power control unit 107 includes a D / A conversion unit 10
5 is constituted by an amplifier for amplifying the drive signal which is the output of No. 5. The power control unit 107 includes the isolated dot detection unit 10
When the isolated dot is detected based on the control information output from the control unit 6, the power modulation is performed on the drive signal. Power modulation unit 1
In 07, the drive signal, that is, the LD, corresponds to the control amount determined when the control information after the D / A conversion indicates the detection of the isolated dot.
The LD drive current output to 110 is varied in an increasing or decreasing direction. If the control information indicates the detection of an isolated dot and indicates a control amount including the data off time, the drive signal is further stepped based on the control amount corresponding to the data off time. Perform modulation.

The LD 110, which is a light emitting element, is detected by a photodiode (PD) 111 and a transistor 11
2. It is incorporated in a part of a negative feedback circuit 114 including a resistor 113. The negative feedback circuit 114 detects the light emission state of the LD 110 that emits light based on the drive signal (LD drive current) output from the power control unit 107 on the PD 111 side, and feeds back the light reception level to the power control unit 107. The current supplied to the LD 110 is controlled so that the light emitting state (light emission luminance) of the LD 110 can be kept constant.

The above driver circuit 100 is, for example,
Input 8-bit digital gradation data (D0 to D
7) the pulse width modulation (eight division) in the PWM unit 104;
By the product of power modulation (32 divisions) (8 × 32 = 256) in the power control unit 107, 256
The light emitting element (LD) 110 can be driven to emit light by the gradation data of the gradation. The driver circuit 100 may be constituted by a hardware function constituted by circuit elements or the like, or may be constituted by a software function for causing a microcomputer or the like to execute a predetermined light emission drive program.

[Embodiment 1] Next, description will be made on the content of detection control of an isolated dot by the above-described isolated dot detection unit 106 which is a main part of the present invention.

FIG. 2 is a diagram showing a state of an isolated dot. In FIG. 2A, isolated dots correspond to a, b, and c. FIG. 2B shows a current waveform (duty ratio 100%) of a drive signal in the case of normal drive (when power modulation is not performed).
FIG. 2C is a diagram showing a waveform of the light emitting state of the LD 110 in the same state. In these figures, dots corresponding to image data are sequentially emitted by scanning in the horizontal axis direction of (a),
In (b) and (c), the horizontal axis direction is described corresponding to the scanning time.

As shown in FIG. 2 (b), if the driving signal has a uniform current waveform without power modulation, as shown in FIG. 2 (c), the light emission waveform of the LD 110 at the isolated dots a, b and c respectively. It has the characteristic that the rise becomes slow. This is based on the fact that the luminous energy (the amount of time integration of the luminous power) is lower than that of the continuous dot by an amount that is dull at the first dot of the isolated dot and the continuous dot. Note that FIG.
The broken line in (c) indicates the desired light emission power (reference power) required for forming one dot, and shows a state in which it takes a long time to reach the reference power because the rise is slow.

Therefore, when an isolated dot is detected, the isolated dot detection unit 106 outputs control information for temporarily increasing the amount of current in order to correct the luminous energy shortage only for the isolated dot.

Specifically, as shown in the conceptual diagram of FIG.
The exposure energy corresponding to the area (time integral value of the emission power) of the necessary exposure energy (dotted portion) shown in FIG. 3A is obtained.

When this exposure energy is converted into a current waveform shown in FIG. 3B, a predetermined correction amount (current amount) Δi with respect to the reference power (the power of the second and subsequent dots of the continuous dot indicated by oblique lines). Just increase it.

When the power control unit 107 receives control information indicating that an isolated dot has been detected from the isolated dot detection unit 106, the power control unit 107 corrects and outputs the drive signal by the correction amount Δi. In the power control unit 107, a correction amount Δi of an increase required when detecting an isolated dot is set and held in advance.

Therefore, when the isolated dot detection unit 106 detects the isolated dots a, b, and c shown in FIG.
Based on the control information (correction amount) output by the isolated dot detection unit 106, the power control unit 107 changes the current amount of the drive signal for these isolated dots by Δi as shown in the current waveform of FIG. Performs power modulation that increases by an amount and outputs the result. As a result, as shown in the light emission waveform of FIG. 2E, the light emission power of the same isolated dot can be made equal to that of the second and subsequent consecutive dots.

As a result, it is possible to secure exposure energy for isolated dots, to form an image of an isolated dot to a desired size, and to make the thickness of vertical and horizontal lines of an isolated dot the same as that of a continuous dot. Can be obtained. In particular, the image quality of the isolated dot portion can be improved even when the LD 110 having a slow emission rising characteristic (referred to as an undershoot characteristic for convenience) is used.

Next, FIG. 4 shows the state of the isolated dot when the duty ratio of the drive signal is less than 100% (when the duty ratio is 66%). In this case, in the current waveform without power modulation shown in FIG.
As in the case of%, the emission power is reduced at the isolated dots a, b, and c. For continuous dots, 1
The light emission power of the dot is low similarly to the isolated dot.
After the dot, heat is generated in advance by the emission of the first dot, so that the response of the emission is faster, the amount of decrease in the emission power is smaller than that of the first dot, and almost the desired exposure energy is reached.

Therefore, as described above, the duty ratio is 1
Even when the duty is less than 00%, the concept shown in FIG. 3 can be applied as in the case of duty 100%. And FIG.
As shown in the current waveform of FIG.
Detects the isolated dots a, b, and c, based on the control information (correction amount) output by the isolated dot detection unit 106,
The power control unit 107 increases the current amount by the correction amount Δi only for the isolated dots a, b, and c. As a result, as shown in the light emission waveform of FIG. 4E, the light emission power of the same isolated dot can be made the same as that of the continuous dot, and the image quality can be improved.

In order to further improve the image quality of the isolated dot, the data off time until the detection of the isolated dot is considered. When detecting an isolated dot, the isolated dot detection unit 106 sets the peak value of the emission power to be higher than the reference power in a predetermined range as the data off time becomes longer, and sets the peak value of the emission power to the reference power as the data off time becomes shorter. The control information (control amount) to be approached is output, and the power control unit 107 performs power control in the same step.

On the other hand, in the second and subsequent dots of the continuous dot, it is considered that the light-emitting dot is previously heated by the light emission of the preceding dot during scanning. When detecting a continuous dot, the isolated dot detection unit 106 detects one of the continuous dots.
As the data off time up to the dot is longer, the peak value of the light emission power is set higher than the reference power in a predetermined range, and thereafter, the peak value of the light emission power of the first dot is up to the predetermined dot (for example, For the second dot and the third dot), control information (correction amount) for stepwise reducing the peak value of the emission power to the reference power value is output, and the power control unit 107 performs power control in the same step. Thereby, it becomes possible to cope with the LD 110 having more various rising characteristics of the light emission waveform.

The stepwise variable control of the light emission power is as follows.
As described above, the bits indicating the data off time of the control information are constituted by a large number of bits, and can be handled by increasing the number of stages. For example, if the above-mentioned data off time is represented by using 5 bits, the power control unit 107 can perform power control with a 32-step correction amount.

[Second Embodiment] In the second embodiment, the LD
A description will be given of the control contents when the light emission waveform has an overshoot characteristic. The basic configuration of the second embodiment is the same as that of FIG.

FIG. 5 is a diagram showing LD characteristics having an overshoot in the light emission waveform. In the case of this LD110,
As shown in the current waveform of FIG. 5B, if the drive signal has a uniform current waveform without power modulation, isolated dots (including the first continuous dot) a, b, and c
As shown in the light emission waveform of FIG. 5C, the light emission power exceeds the reference power, the light emission energy is excessive, and the interval between adjacent dots is destroyed, thereby deteriorating the image quality.

Therefore, when an isolated dot is detected, the isolated dot detection unit 106 outputs control information for temporarily reducing the amount of current to correct excessive exposure energy only for the isolated dot.

Specifically, as shown in the conceptual diagram of FIG.
The exposure energy corresponding to the area (time integral of the emission power) of the necessary exposure energy (dotted portion) shown in FIG. 6A is obtained. When this exposure energy is converted into the current waveform shown in FIG. 6B, it is reduced by a predetermined correction amount (current amount) -Δi with respect to the reference power (the power of the second and subsequent dots of the continuous dot shown by oblique lines). Equal to

Therefore, based on the control information (correction amount) that the isolated dot detecting section 106 detects and outputs the isolated dots a, b, and c shown in FIG.
Performs power modulation on these isolated dots to reduce the current amount of the drive signal by -Δi, as shown by the current waveform in FIG. 5D, and outputs the result. As a result, FIG.
As shown in the light emission waveform of (e), the light emission power of the same isolated dot can be made the same as that of the second and subsequent consecutive dots.

Next, FIG. 7 shows the state of the same isolated dot when the duty ratio of the drive signal is less than 100% (when the duty ratio is 66%). In this case, in the current waveform without power modulation shown in FIG.
%, The light emission power becomes excessive at the isolated dots a, b, and c.

Regarding the continuous dots, the first dot has an excessive light emission power as in the case of the isolated dot. However, since the second dot and subsequent dots are heated in advance by the emission of the first dot, the first dot emits light more than the first dot. , The light emission response is improved, the emission power excess becomes smaller than that of the first dot, and almost the desired exposure energy is reached.

Therefore, as described above, the duty ratio is 1
Even when the duty is less than 00%, the concept shown in FIG. 6 can be applied as in the case of duty 100%. And FIG.
As shown in the current waveform of FIG.
Detects the isolated dots a, b, and c, based on the control information (correction amount) output by the isolated dot detection unit 106,
The power control unit 107 reduces the current amount by the correction amount -Δi only for the isolated dots a, b, and c. As a result, as shown in the light emission waveform of FIG. 7E, the light emission power of the same isolated dot can be made the same as that of the continuous dot, and the image quality can be improved.

A method for improving the image quality of isolated dots and continuous dots with higher accuracy is described in the first embodiment.
In the same manner as described above, the light emission power may be controlled in a more stepwise manner based on the data off time. When detecting an isolated dot, the isolated dot detection unit 106 controls the drive with a light emission power smaller than the reference power value as the data off time is shorter. At the time of continuous dot detection, as the data off time until the continuous dot detection is shorter, drive control is performed with a light emission power smaller than the reference power value. Control information (correction amount) for increasing the peak value of the emission power stepwise to the reference power value is output. Also in the second embodiment, the above-described data off time is represented by using a large number of bits, and power control can be performed with a multi-step correction amount.

The control of the drive current described in each of the above embodiments can be similarly applied to drive circuits having various configurations such as the wavelength of the LD and the connection type of anode common / cathode common. When the LD has an undershoot emission characteristic, the emission drive according to the first embodiment is effective.
When the light emitting device has an overshoot light emission characteristic, the light emission drive according to the second embodiment is effective. The light emission drive described in the first embodiment is not limited to the LD having the undershoot characteristic, and an image quality improvement effect of an isolated dot can be obtained when a general LD other than the LD having the overshoot characteristic is used. Needless to say.

As described above, the present invention can be widely applied to various light emitting devices including LDs having various light emitting characteristics, regardless of the difference in light emitting characteristics of LDs. In particular, the image quality of isolated dots can be improved using an inexpensive LD without using an expensive LD with a short emission wavelength or an expensive LD with good responsiveness without using an expensive LD.

The image forming method described in the above embodiment is executed by executing a prepared program on an image forming apparatus such as a laser printer and a digital copying machine, and a computer such as a personal computer and a workstation. It can also be achieved.
This program is recorded on a computer-readable recording medium such as a hard disk, a floppy (registered trademark) disk, a CD-ROM, an MO, and a DVD, and is read out from the recording medium and executed by the computer.
This program can be distributed via the recording medium and a network such as the Internet.

[0072]

According to the first aspect of the present invention, an isolated dot is desired because the emission power of the isolated dot is variably controlled so that the exposure energy of the isolated dot becomes equal to the exposure energy of the continuous dot. It can be formed in the size, and the quality of the formed image can be improved. In particular, there is an effect that an image forming apparatus capable of achieving high quality of a low density image portion including an isolated dot can be obtained. In particular, it is possible to improve the image quality of an electrophotographic image forming apparatus such as a laser printer or a digital copying machine that forms an image on an image carrier at low cost.

According to the second aspect of the invention, the first continuous dot is also detected as an isolated dot, and the emission power of the first dot is set to be equal to the exposure energy of the second and subsequent dots. Because of the variably controlled configuration, it is possible to obtain an image forming apparatus capable of improving the quality of a formed image, such as making the thickness of continuous vertical and horizontal lines uniform.

According to the third aspect of the invention, even if the light emitting element has an overshoot characteristic or an undershoot characteristic, the light emitting power for the isolated dot is variably controlled so as to cancel the characteristic.
Even if an expensive light emitting element having good responsiveness is not used, an image forming apparatus capable of improving the quality of an isolated dot formed image and reducing the cost by driving control of the light emitting element having various characteristics can be obtained.

According to the fourth aspect of the present invention, since the emission power is variably controlled in more detail based on the data off time until the detection of the isolated dot, an image forming apparatus capable of improving the quality of the image formed by the isolated dot can be obtained. Is obtained.

According to the fifth aspect of the invention, since the emission power of the second and subsequent dots of the continuous dot is variably controlled in more detail, it is possible to improve the quality of the image formed by the continuous dot. Further, there is an effect that an image forming apparatus that can correspond to a light emitting element having various light emission waveform rising characteristics can be obtained.

According to the sixth aspect of the present invention, an image of a low-density portion including an isolated dot can be enhanced by a simple configuration in which the isolated dot is detected and the drive signal supplied to the light emitting element is variably controlled by the emission power. There is an effect that an image forming method capable of improving quality can be obtained.

According to the seventh aspect of the present invention, a vertical line and a horizontal line composed of continuous dots are formed by a simple structure in which the first dot of the continuous dots is detected and the driving signal supplied to the light emitting element is variably controlled by the light emission power. This produces an effect that an image forming method capable of improving the quality of the image can be obtained.

According to the eighth aspect of the present invention, even if the light emitting element has an overshoot characteristic or an undershoot characteristic, the light emitting power for the isolated dot is variably controlled so as to cancel the characteristic.
There is an effect that an image forming method can be obtained in which the quality of an isolated dot formed image can be easily improved by drive control for light emitting elements having various characteristics without using expensive light emitting elements having good responsiveness.

According to the ninth aspect of the present invention, since the light emission power is variably controlled in more detail based on the data off time until the detection of the isolated dot, an image forming method capable of increasing the quality of the image formed by the isolated dot can be achieved. Is obtained.

According to the tenth aspect of the present invention, since the emission power of the second and subsequent dots of the continuous dot is variably controlled in more detail, it is possible to improve the quality of the image formed by the continuous dot and to achieve various light emission. There is an effect that an image forming method that can correspond to a light emitting element having a waveform rising characteristic can be obtained.

According to the eleventh aspect of the present invention, there is provided a program capable of variably controlling the light emission power of a light emitting element when an isolated dot is detected by causing a computer to execute the method, thereby improving the image quality of the isolated dot portion. Is obtained.

According to the twelfth aspect of the present invention, when a program executed by reading by a computer detects an isolated dot, the computer can variably control the light emission power of the light emitting element to improve the image quality of the isolated dot portion. There is an effect that a readable recording medium can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image forming apparatus according to the present invention.

FIG. 2 is a drive control (du) according to the first embodiment of the apparatus.
FIG. 4 is a diagram for explaining a ty ratio of 100%).

FIG. 3 is a diagram for explaining the relationship between the exposure energy of the isolated dots and the drive current according to the first embodiment;

FIG. 4 is a diagram showing a drive control (du) according to the first embodiment of the apparatus.
FIG. 9 is a diagram for explaining a ty ratio of 66%).

FIG. 5 is a diagram illustrating a drive control (du) according to the second embodiment of the apparatus.
FIG. 4 is a diagram for explaining a ty ratio of 100%).

FIG. 6 is a diagram for explaining a relationship between exposure energy and drive current of an isolated dot according to the second exemplary embodiment;

FIG. 7 is a diagram showing a drive control (du) according to the second embodiment of the apparatus.
FIG. 9 is a diagram for explaining a ty ratio of 66%).

FIG. 8 is a diagram illustrating light emission characteristics of a general LD and an image forming state.

FIG. 9 is a diagram illustrating light emission characteristics and an image forming state of an LD having overshoot characteristics.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 driver circuit (LD driver) 101 digital circuit section 102 analog circuit section 103 LUT section 104 PWM section 105 D / A conversion section 106 isolated dot detection section 107 power control section 110 LD 111 PD 112 TR 113 resistor 114 negative feedback circuit

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C362 AA03 AA22 AA54 AA56 AA61 AA63 CA09 CA10 CA14 CB37 2H027 DB00 DE07 EA02 EB03 EC11 EC20 2H076 AB05 AB12 AB22 AB75 DA17 DA19 DA22 5C051 AA02 CA06 DB29 DE30

Claims (12)

[Claims] 1. An image forming apparatus for forming an image on an image carrier by scanning a light beam emitted from a light emitting element based on input image data, wherein non-light emitting dots are arranged before and after the image data in the scanning direction. An isolated dot detection unit for detecting an isolated dot, and a drive signal supplied to the light emitting element so that the exposure energy of the isolated dot becomes equal to the exposure energy of the continuous dot when the isolated dot is detected by the isolated dot detection unit. An image forming apparatus comprising: a power control unit that variably controls light emission power of an isolated dot portion. 2. The image forming apparatus according to claim 1, wherein the isolated dot detection unit detects a first one of consecutive light-emitting dots as an isolated dot. 3. The power control section variably controls a drive signal using a correction power value set in advance according to a light emission rising characteristic of a light emitting element. Reduces the light emission power for isolated dots so as to cancel the overshoot amount of exposure energy, and increases the light emission power for isolated dots so as to cancel the undershoot amount of exposure energy for light emitting elements having undershoot characteristics. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus performs variable control. 4. The isolated dot detection section outputs control information including a data off time until the isolated dot is detected when the isolated dot is detected, and the power control section responds to the data off time of the control information. 2. The image forming apparatus according to claim 1, wherein the light emitting power of the isolated dot is varied. 5. The image forming apparatus according to claim 2, wherein the power control unit changes the emission power of the second and subsequent dots in a stepwise manner when a continuous dot is detected. 6. An image forming method for forming an image on an image carrier by scanning a light beam emitted from a light emitting element on the basis of input image data, wherein non-light emitting dots are arranged before and after in the scanning direction of the image data. And variably controls the emission power of the drive signal supplied to the light emitting element so that the exposure energy of the isolated dot becomes equal to the exposure energy of the continuous dot when the isolated dot is detected. An image forming method. 7. The image forming method according to claim 6, wherein the first dot of the continuous luminescent dots in the image data is detected as an isolated dot. 8. A driving signal variably controlled by using a correction power value set in advance according to a light emission rising characteristic of a light emitting element when an isolated dot is detected according to any one of claims 6 and 7. For a light emitting element having an overshoot characteristic, the light emitting power for an isolated dot is reduced so as to cancel out the exposure energy of the overshoot amount, and for a light emitting element having an undershoot characteristic, an exposure of an undershoot amount is performed. An image forming method, comprising: performing variable control for increasing light emission power for an isolated dot so as to cancel energy. 9. At the time of detecting an isolated dot according to claim 6, according to a data off time until the detection of the isolated dot,
An image forming method characterized by varying the light emission power of an isolated dot. 10. An image forming method according to claim 7, wherein the emission power of the second and subsequent dots is changed stepwise when detecting the continuous dots. 11. A program for causing a computer to execute the method according to claim 6. 12. A computer readable recording medium on which the program according to claim 11 is recorded.