JP3450015B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to any color image data.
Scanning the photoconductor with a predetermined amount of laser light based on
An image forming apparatus which forms a desired color image
Is .

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a schematic structure of a general image forming apparatus.

In an image forming apparatus, a drum-shaped photosensitive member (hereinafter, simply referred to as "photosensitive member") 1 as an image forming member is uniformly charged by a scorotron charger 2 and then binarized spot light is used as a scanning optical system. 8 to 12 form an imagewise exposure on the photoreceptor 1 to form a dot-shaped electrostatic latent image, which is reversely developed by the developing devices 4 to 6 to form a dot-shaped toner image. The steps are repeated to form a color toner image on the photoconductor 1, and the color toner image is transferred onto the paper surface and fixed to obtain a color image.

As shown in FIG. 4, the image forming apparatus includes a photosensitive member 1, a scorotron charger 2, developing devices 4 to 6, a semiconductor laser 7, scanning optical systems 8 to 12, a photodiode 13,
Control board 20, reference clock generation circuit 30,
It consists of drivers 40 and 50.

The photodiode 13 includes scanning optical systems 8 to.
The scanning light obtained by scanning the emitted light of the semiconductor laser 7 is detected by 12 and the index pulse signal IDX is output. The control board 20 outputs the drive signal L for the semiconductor laser 7, inputs the index pulse signal IDX, and outputs the same signal IDX to other circuits.

The reference clock generation circuit 30 outputs a pulse signal having the same repetition period as the pixel clock to the reference clock CK.
The reference clock CK is output to the control board 20 and the drivers 40 and 50. As a result, the rotation speed of the photoconductor 1 and the scanning of the scanning optical systems 8 to 12 are synchronized.

The photoconductor 1 has a motor M1 mounted on its drive shaft. The motor M1 is rotated by the driver 40 to rotate the photoconductor 1 at a predetermined speed.

Further, the polygon mirror 10 has a drive shaft of a motor M2 attached to the center of rotation thereof. Motor M2
Is rotated at a predetermined speed by the driver 50.

By inputting the reference clock CK from the reference clock generation circuit 30 to the drivers 40 and 50,
The rotation phases of the photoconductor 1 and the polygon mirror 10 are synchronized.

Further, the semiconductor laser 7 is oscillated according to the value of the image data D, and the polygon mirror 10 which rotates the laser light (emitted light) from the semiconductor laser 7 at a predetermined speed.
The fθ lens 11 and the cylindrical lenses 9 and 12 are used to deflect the light beam, and the finely focused spot is scanned on the uniformly charged upper surface of the photoreceptor 1. The semiconductor laser 7 is a coherent light source, a collimator lens 8 is provided as a light emission optical system, a polygon mirror 10 and an fθ lens 11 are provided as deflection optical systems, and the polygon mirror 1 is provided.
Cylindrical lenses 9 and 12 are provided as a surface tilt correction optical system based on 0.

A conventional example of a control board for such an image forming apparatus is shown in FIG.

In FIG. 5, the APC circuit 21 divides the input reference clock CK (FIG. 6A) to generate an APC start signal (control start pulse signal) as shown in FIG. 6B. To occur. The cycle of this APC start signal is a cycle of one page, and control of the amount of light emitted from the semiconductor laser 7 is started by the rise of the APC start signal.

This control is performed by the reference light amount r set in the APC circuit 21 and the photodiode built in the semiconductor laser 7.
Emitted light quantity m of laser 7 detected by (first detecting means)
Is compared with the reference light amount r
The output signal value R is changed so as to coincide with. The level of the laser drive signal L output from the laser drive circuit 22 corresponds to the output signal value R, and therefore the amount of light emitted from the laser 7 becomes a value corresponding to the signal value R.

The emitted light quantity m of the semiconductor laser 7 is as shown in FIG.
As shown in (c), the reference light amount r is obtained in a period of about half a line. The control of the emitted light amount m is a two-step control including an initial low precision control (coarse control) and a subsequent high precision control (fine control). For example, as shown in FIG. 6C, T1 =
Low precision control is performed during the period of 2 lines, and high precision control is performed during the period of T2 = 0.7 line. Then, the control is stopped when the emitted light amount m of the laser 7 becomes about 98% of the reference light amount r.

After the control of the amount of emitted light is stopped, the output signal value R is fixed to the final value RR during the control period. The amount of light emitted from the semiconductor laser 7 thereafter in the period of one page is a binary light amount value or zero light amount value according to the fixed output signal value RR. Which value will be determined by the image data D input to the laser drive circuit 22.

[0016]

However, in the above-mentioned conventional control board, as shown in FIG. 6 (c), a constant value r from the rising edge of the APC start signal.
It takes about 3 line period to settle in, the amount of emitted light of the semiconductor laser 7 is small immediately after the rise of the APC start signal, and the index pulse signal IDX is not output from the photodiode 13 (the amount of emitted light of the laser 7 is (It is about 50% of the reference light amount r when one line has passed from the rise of the APC start signal).

Therefore, the index pulse signal IDX
As shown in FIG. 6 (d), the pulse signal train is such that two pulses are omitted in the period of one page. Therefore, control may become unstable in other circuits that require the index pulse signal IDX.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a control board of an image forming apparatus in which no pulse dropout occurs in an index pulse signal.

[0019]

In order to solve the above-mentioned problems, the image forming apparatus according to the present invention uses an arbitrary image data.
Scanning the photoconductor with a predetermined amount of laser light based on the
A device for forming a desired image, a laser with a predetermined amount of light
The semiconductor laser that emits light and the semiconductor laser are
A laser drive circuit driven based on image data;
Of the semiconductor laser driven by a laser drive circuit
First detection means for detecting the amount of emitted light, and the first detection means
The laser light of the predetermined emitted light amount detected by the
A scanning optical system for scanning the photoconductor and the scanning optical system.
The laser beam to the photoconductor that is scanned by
Second detecting means for outputting a pulse signal, and the second detecting means.
The index pulse signal obtained from the detection means of
Based on the initial pulse signal for starting the semiconductor laser
Control timing pulse signal
Live means and laser detected by the first detecting means
Light emission amount of light and obtained from the timing generating means
Based on the control timing pulse signal, the laser drive time
A light quantity control means for controlling a path, and the light quantity control means
Is a control timing obtained from the timing generating means.
Output signal to the laser drive circuit based on the pulse signal.
It is characterized in that to fix the issue value.

[0020]

[Action] Oite the image forming equipment according to the invention, FIG. 1
As shown in the timing generator (hereinafter simply timing
Initial pulse generation circuit 24 of that grayed means 23), FIG. 2
An initial pulse signal (hereinafter simply referred to as initial pulse a) for starting the semiconductor laser as shown in (a) is generated. This initial pulse a is transmitted through the OR circuit 25 to the APC circuit (optical
Quantity control means) 21 and this APC circuit 21
An APC start signal (FIG. 2B) is generated as a control start pulse signal which rises at the trailing edge of the initial pulse a.

After the generation of this APC start signal, the emitted light quantity (FIG. 2C) of the semiconductor laser 7 (FIG. 4) is the reference light quantity r.
Is controlled so that Light intensity emitted from the semiconductor laser m
Is a two-step control of low precision control and high precision control. In low precision control, the laser 7
The emitted light amount m of is brought close to the reference light amount r, and is matched with the reference light amount r in the next high-precision control.

When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped, and the emitted light amount is determined by the fixed output signal value RR by the image data D input to the laser drive circuit 22 or It is controlled to a binary value of zero light intensity.

After the semiconductor laser 7 is activated in this way, laser light emitted from the semiconductor laser 7 (emission
Light) is the photodiode shown in FIG. 4 (second detection means)
The index pulse signal IDX (FIG. 2) which is detected for each line by 13 and is a pulse train with an interval of one line.
(D)) is input to the APC control circuit 23.

When the index pulse signal IDX input to the APC control circuit 23 is input to the APC circuit 21 via the OR circuit 25 and the APC start signal rises at the trailing edge of the signal IDX, the emitted light amount m of the semiconductor laser 7
Is controlled to be the reference light amount r. When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped as described above.

Output signal b of the OR circuit 25 (FIG. 2 (e))
Is a control timing pulse signal as a logical sum signal of the initial pulse a and the index pulse signal IDX,
The APC start signal is obtained by dividing the control timing pulse signal b, and rises when the signal b falls.

As described above, the APC start signal is the control timing pulse signal b, that is, the index pulse signal I.
Since the pulse rises at the fall of DX, the pulse of the index pulse signal IDX does not exist immediately after the rise of the APC start signal, and the emitted light quantity m of the semiconductor laser 7 is 2
Since the reference light amount r is rapidly approached by the step control, the APC
Immediately after the start signal rises, the amount of light emitted from the semiconductor laser is greatly reduced, so that the problem that the pulse disappears does not occur.

[0027]

EXAMPLES Next, an example of an image forming equipment according to this invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and differs from FIG. 5 in that an APC control circuit (timing means) 23 is added.

The APC control circuit 23 has a second detecting means.
The index pulse signal IDX output from the photodiode 13 (FIG. 4) as an example is input. Further, as shown in FIG. 2A, the initial pulse generation circuit 24 generates one initial pulse a synchronized with the rotating operation of the polygon mirror 10 for starting the semiconductor laser 7 (FIG. 4). .

Initial pulse a and index pulse signal I
DX is input to the OR circuit 25 and becomes a logical sum signal (control timing pulse signal) b (FIG. 2 (e)). The pulse P1 of the control timing pulse signal b is a pulse corresponding to the initial pulse a, and the other pulses are pulses corresponding to the pulse of the index pulse signal IDX.

First, the initial pulse a is input to the APC circuit (light quantity control means) 21 via the OR circuit 25, and this A
In the PC circuit 21, an APC start signal (see FIG. 2) as a control start pulse signal that rises at the trailing edge of the initial pulse a
(B)) occurs.

This APC start signal is shown in FIG.
As indicated by the dotted lines in (c) and (e), control is performed such that the pulse P1 of the control timing pulse signal b corresponding to the initial pulse a rises and rises, and the emitted light amount m of the semiconductor laser 7 becomes the reference light amount r. To be done. As shown in FIG. 2C, the emitted light amount m of the laser 7 approaches the reference light amount r in the period of one line. The control of the emitted light amount m will be described later. The emitted light amount of the laser 7 is controlled by changing the output signal value R of the APC circuit 21. When the emitted light amount m of the laser 7 matches the reference light amount r, the output signal value R is the value at the time of the match. (Final value) Fixed to RR.

When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped, and the emitted light amount is determined by the fixed output signal value RR by the image data D input to the laser drive circuit 22 or It is controlled to a binary value of zero light intensity (FIG. 2 (c) shows only the emitted light intensity determined by the output signal value RR).

In this way, after the semiconductor laser 7 is activated, the laser light output from the scanning optical systems 8 to 12 (FIG. 4) in which the emitted light of the semiconductor laser 7 is the scanning light is converted by the photodiode 13 into one. Detecting for each line, an index pulse signal IDX, which is a pulse train with an interval of one line, is obtained (FIG. 2 (d)). This index pulse signal IDX
Is input to the APC control circuit 23 through the terminal T1,
Further, via the OR circuit 25, the control timing pulse signal b
Is input to the APC circuit 21 to generate an APC start signal.

As can be seen from FIGS. 2 (b) and 2 (e), A
The PC start signal is a signal that divides the control timing pulse signal b and rises when the control timing pulse signal b falls. The frequency division is such that the number of pulses of the control timing pulse signal b, for example, 3600 becomes one.

The APC start signal of the APC circuit 21 is
As indicated by the dotted lines in FIGS. 2B, 2C, and 2E, the index pulse signal IDX rises due to the trailing edge of the pulse P2, and the emitted light amount m of the semiconductor laser 7 is changed to the reference light amount r.
When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped as described above. The interval between the pulses P1 and P2 is one page period.

In this way, the APC start signal rises due to the trailing edge of the pulse of the index pulse signal IDX, so the pulse of the index pulse signal IDX is A
It does not exist immediately after the rise of the PC start signal, and the problem that the pulse disappears due to a large decrease in the emitted light amount of the semiconductor laser immediately after the APC start signal does not occur.

Next, control of the amount of light emitted from the semiconductor laser 7 in FIG. 2 will be described with reference to FIG.

In the control shown in FIG. 3, low precision control (coarse control) with a large level difference of one step is performed in the first control period (for example, one line period) t1, and the next control period (for example, one line period). In the period t2, high precision control (fine control) with a small level difference of one step is performed. With this two-step control, the emitted light amount m of the semiconductor laser 7 can be quickly brought close to the reference light amount r to prevent disappearance of the index pulse signal IDX.
When the reference light amount r is approached to some extent, the level difference of one step can be reduced to improve the control accuracy of the emitted light amount m.

[0040]

As described above , according to the image forming apparatus of the present invention, the laser beam scanned on the photoconductor is detected.
Starts up the obtained index pulse signal and semiconductor laser
Control pulse generated based on the initial pulse signal for
Based on the aiming pulse signal and the amount of light emitted from the semiconductor laser.
Based on the light amount control means for controlling the laser drive circuit,
This light quantity control means is based on the control timing pulse signal.
The output signal value to the laser drive circuit is fixed.
It This configuration control timing pulse signal based on
In synchronization with the control start pulse signal which rises Zui, half
Light intensity control to match the emitted light intensity of the conductor laser with the reference light intensity
Can be executed. Therefore, when the laser light is initially emitted
Based on the initial pulse signal, which is an index pseudo signal.
By generating the control start pulse signal, the emitted light amount of the semiconductor laser is significantly reduced, and even if the index pulse signal is not detected, the emitted light amount itself of the semiconductor laser can be rapidly increased compared to the conventional method . , Laser light
It is possible to prevent the omission of the index pulse signal while reaching a predetermined amount of emitted light . This index pulse
It becomes possible to execute other control using signals accurately.
It

[Brief description of drawings]

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

FIG. 2 is a time chart for explaining the operation of the circuit of FIG.

FIG. 3 is a time chart showing another example of controlling the emitted light amount of the semiconductor laser.

FIG. 4 is a configuration diagram showing a general image forming apparatus.

FIG. 5 is a block diagram showing a conventional control board of the image forming apparatus.

FIG. 6 is a time chart for explaining the operation of the circuit of FIG.

[Explanation of symbols]

21 APC circuit (light quantity control means) 22 Laser drive circuit 23 APC control circuit (timing means) 24 Initial pulse generation circuit 25 OR circuit

Front Page Continuation (72) Inventor Kenji Taki 2970 Ishikawa-cho, Hachioji, Tokyo Konica Corporation (72) Inventor Shoji Akamatsu 2970 Ishikawa-cho, Hachioji, Tokyo Konica Corporation (72) Inventor Takao Kurohata Tokyo 2970 Ishikawa-cho, Hachioji-shi, Konica Corporation (56) Reference JP-A-1-187574 (JP, A) JP-A-2-71572 (JP, A) JP-A-4-27971 (JP, A) Kaihei 3-41870 (JP, A) JP-A-2-238473 (JP, A) JP-A-61-159863 (JP, A) JP-A-2-20885 (JP, A) JP-A-1-300219 ( (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/113 B41J 2/44 G02B 26/10

Claims (2)

(57) [Claims] 1. A predetermined amount of light based on arbitrary image data
A device that scans a laser beam on a photoconductor to form a desired image.
And a semiconductor laser that emits a laser light of a predetermined light quantity, and the semiconductor laser is driven based on the image data.
A laser driving circuit and the semiconductor laser driven by the laser driving circuit.
A first detecting means for detecting the amount of light emitted from the first detector, and a predetermined amount of light emitted from the first detector.
A scanning optical system for scanning the laser beam on the photosensitive member, the laser beam to the photosensitive member to be scanned by said scanning optical system
Second detection that detects the
Output means and the index pulse signal obtained from the second detecting means.
Signal and an initial pulse signal for starting the semiconductor laser
A tie that generates a control timing pulse signal based on
And the emission light of the laser light detected by the first detecting means.
Quantity and control timing obtained from the timing generating means
Control the laser drive circuit based on the pulse signal.
And a light amount control means for controlling the light quantity, the light quantity control means being a control timing pattern obtained from the timing generation means.
Output signal value to the laser drive circuit based on the loose signal
An image forming apparatus characterized by fixing the . 2. The light amount control means is a control that rises based on the control timing pulse signal.
The semiconductor laser output is synchronized with the start pulse signal.
Performing light intensity control that matches the amount of light emitted with the reference amount of light
The image forming apparatus according to claim 1, wherein: