JP3244787B2 - Image forming apparatus and light amount control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and, more particularly, to a control of a light amount of a laser beam printer.

[0002]

2. Description of the Related Art The relationship between the current supplied to a laser diode and the light output differs for each individual laser diode.
Moreover, it also changes due to the heat generated by the laser diode itself,
It is not possible to make the laser emit light by simple open loop constant current control. Therefore, it is necessary to monitor the optical output of the laser and control it so that a desired optical output level is obtained. This control is called APC (Automatic Light Amount Control). FIG. 7 shows a laser control circuit for performing APC.

This laser control circuit is composed of a constant current circuit 1, a switching circuit 2, and an amplifier circuit 3.
The constant current circuit 1 is a voltage-current converter, and flows a current I1 according to the light amount signal 4 from the control device. A circuit for switching this with the laser lighting signal 5 is a switching circuit. The laser diode 6 emits light in accordance with the operation of the switching circuit 2.

[0004] The light emission amount is detected as a current value by the photodiode 7 and converted into a voltage by the resistor 8. The light emission amount converted into the voltage value is amplified by the amplifier 3 and becomes a light emission amount signal 9. The controller increases the level of the light quantity signal 4 while monitoring the light emission quantity signal 9.

FIG. 8 is a flowchart showing this APC operation. In this control, after activating the laser forcible lighting signal, the light emission amount signal is monitored, and if the light emission amount is lower than a desired value, the level of the light amount signal is increased by one step.
Conversely, if it is higher than the desired value, the light amount signal is lowered by one step. When the light emission amount reaches a desired value, AP
The C operation ends.

[0006] During this time, the laser beam scans in FIG.
It corresponds to the part corresponding to the arrow.

APC is performed not only at the beginning of image formation, but also at a portion corresponding to a space between sheets when a plurality of sheets are continuously recorded. There is also a place where APC is performed outside the image area as shown in FIG. This method uses 1
It is used when a light amount level is guaranteed for each line or when a line of a toner image visualized by a laser beam emitted between sheets affects image formation.

[0008]

However, in the above conventional example, the APC taking into account the droop characteristic of the laser diode is not performed, and the light emission amount signal after the forced lighting signal is activated (initial APC) is recorded. The light emission amount signal after the activation between the paper and the recording paper or for each line (inter-paper APC) indicates a different value.

For this reason, as shown in FIG. 6, when a plurality of continuous recordings are made, the amount of light emission of the first page is relatively large, and the image density is higher than that of the second and subsequent pages. .

[0010]

An image forming apparatus according to the present invention is an image forming apparatus for forming an image by using a light source for generating a light beam, comprising: detecting means for detecting a light amount of the light source; Means for controlling a drive current supplied to the light source so that the amount of light detected by the means becomes a target value, and continuously emits light from the light source prior to image formation by the current control means. Current control is performed, and then the light source is intermittently made to emit light in the same manner as the current control performed between pages, and the current control means determines a drive current at the time of image formation, and an image is formed using the determined drive current. It is characterized in that formation is started. Further, the light amount control method of the present invention includes a detecting unit for detecting a light amount of the light source, and a current controlling unit for controlling a driving current supplied to the light source so that the light amount detected by the detecting unit becomes a target value. A light amount control method of a light source of an image forming apparatus that forms an image using a light beam generated from the light source,
Prior to image formation, a step in which the light source is continuously lit to perform current control by the current control means, and thereafter, the current control is performed by intermittently illuminating the light source similarly to the light amount control performed between pages. Means for determining a drive current at the time of image formation by means, and a step of starting image formation using the determined drive current.

[0011]

【Example】

 Embodiment 1 FIG. 1 shows a basic circuit configuration of the present invention.

In FIG. 1, reference numeral 11 denotes a laser light source, and reference numeral 12 denotes laser light detecting means for detecting the output of laser light. 1
Reference numeral 3 denotes a laser light quantity control means for controlling a laser light source based on the output of the laser light detection means 12 so as to obtain a predetermined light output level. Be composed. Also,
Reference numeral 14 denotes a timing control unit for controlling the timing of the laser light amount control unit 13, and reference numeral 17 denotes a photoconductor that receives a laser beam and forms a latent image.

When the printer receives a print instruction, it supplies a laser driving current to turn on the laser light source 11, and the laser light detecting means 12 detects the laser light and controls the light quantity control means 13.
The light amount signal 9 is sent to The light amount control means 13 is provided in an area excluding the maximum recordable area (from A to B of the photoconductor 17) in the main scanning direction and in an area excluding the image guarantee area from the leading edge to the trailing edge of the recording paper in the sub-scanning direction. The control is performed so as to obtain a predetermined light amount while taking timing with a signal from the timing control means 14 so as to perform light amount control. And
When a predetermined amount of light is obtained, the photosensitive member 17 is irradiated with laser light to form a latent image.

FIG. 2 shows an operation procedure of light quantity control according to the present invention. Each step is shown in parentheses.

First, an initial APC by forced lighting is started (2), and it is determined whether the light emission amount has reached a predetermined value (3). If the light emission amount is lower than the predetermined value, the level of the light amount signal is increased by one step. When the light emission amount matches the predetermined value, the APC operation ends (4). Since the initial APC requires a long time of several tens of milliseconds until the operation is completed, the droop characteristic of the laser diode affects the setting of the light amount.

Therefore, after the operation of the initial APC is completed, the laser diode is cooled for a predetermined time, and (5) the inter-paper APC is started (6). In this case, the laser is emitted based on the result of the initial APC, and it is determined whether or not the light emission amount signal is a predetermined value (7). Conversely, when the light emission amount signal is lower than the predetermined value, the level of the light amount signal is increased by one step (9) and the light emission amount is adjusted. When the light emission amount signal matches the predetermined value, the paper interval APC is finished (10), and the first page is printed (11). After the printing of the first page is completed, the inter-sheet APC is executed as in the conventional case (12) to (1).
6) Print the second page (17). Similar operations are performed on the third and subsequent pages.

FIG. 3 shows the operation of the laser beam in the above printing sequence.

In this figure, A1 is an initial APC area by forcible lighting, A2 is an inter-paper APC area to be subsequently performed, and A
Reference numeral 3 denotes a first page print area, A4 denotes a paper interval APC area between the first page and the second page, and A5 denotes a waveform of each laser beam in the second page print area.

Here, the light emission amount setting in the area A2 and the area A
Since the setting of the light emission amount in the fourth page is almost equal, the print densities of the first page and the second and subsequent pages become equal, and a high-quality image can be formed.

Embodiment 2 FIG. 4 shows an operation procedure of a second embodiment of light quantity control according to the present invention. Each step is shown in parentheses as in the first embodiment.

In the case where designation of the number of prints can be detected from a printer controller (not shown) or an external host computer (not shown), when printing is started (1), it is first determined whether or not single page printing is performed (2). If a single page [1
For page] printing, conventional light amount control is performed. That is,
Initial APC by forced lighting is started (4) It is determined whether the light emission amount signal is a predetermined value (5). If the light emission amount signal is lower than the predetermined value, the level of the light amount signal is increased by one step, and the light emission amount is set to the predetermined value. When they match, the APC operation ends (6).
Then, printing is performed (7), and the process proceeds to the print standby routine control (8).

On the other hand, in the case of a print instruction for a plurality of sheets, the first embodiment
Light amount control similar to that described above is performed. That is, the initial APC by forced lighting is started (10), it is determined whether or not the light emission amount signal is a predetermined value (11). When the value coincides with the value, the APC operation ends (12). In printing of a plurality of sheets, the droop characteristic of the laser diode affects the light amount setting in the initial APC. Therefore, after the operation of the initial APC is completed, the laser diode is cooled for a predetermined time (13).
The paper interval APC is started (14).

In the paper interval APC, the laser is emitted based on the result of the initial APC to determine whether the light emission amount signal is a predetermined value (16). If the light emission amount signal is higher than the predetermined value, the level of the light amount signal is reduced by one step (17). ). Conversely, when the light emission amount signal is lower than the predetermined value, the level of the light amount signal is increased by one step to adjust the light emission amount (18). When the light emission amount signal coincides with the predetermined value, the paper interval APC is finished (1).
9) Print the first page (20). After the printing of the first page is completed, the paper interval APC is executed (21) to
(25) The second page is printed (26). Similar operations are performed on the third and subsequent pages.

By performing the above processing, it is possible to increase the printing speed in single-page printing, and to perform appropriate light quantity control without printing density difference between recording papers in multiple-sheet printing. Image formation is possible.

Third Embodiment FIG. 5 shows an operation procedure of a third embodiment of the light amount control according to the present invention. Each step is shown in parentheses as in the first embodiment.

As in the second embodiment, when the designation of the number of prints can be detected from a printer controller (not shown) or an external host computer (not shown), when a print instruction is received, an initial APC by forced lighting is started ( 2) It is determined whether the light emission amount signal is a predetermined value (34). If the light emission amount signal is lower than the predetermined value, the level of the light amount signal is increased by one step, and the APC operation is terminated when the light emission amount matches the predetermined value (5). ). Here, it is determined whether or not the printing is a single page (5).
If it is a single page, printing is performed (6), and control is transferred to the print standby routine control (8).

On the other hand, if a print instruction is issued for a plurality of sheets, the laser diode is cooled for a predetermined time in consideration of the droop characteristics of the laser diode in the initial APC (13), and the inter-paper APC is started (14). First, the laser is emitted based on the result of the initial APC, and it is determined whether the light emission amount signal is a predetermined value (10). If the light emission amount signal is higher than the predetermined value, the level of the light amount signal is reduced by one step (11). Conversely, when the light emission amount signal is lower than the predetermined value, the level of the light amount signal is increased by one step (12) to adjust the light emission amount. When the light emission amount signal matches the predetermined value, the paper interval APC is finished (13), and the first page is printed (14). And 1
After the printing of the page is completed, the paper interval APC is executed (15).
(19) The second page is printed (20). Similar operations are performed on the third and subsequent pages.

By performing the above processing, it is possible to increase the printing speed in single-page printing, and to perform appropriate light amount control without printing density difference for each recording paper in multiple-sheet printing. Image formation is possible.

[0029]

According to the present invention, due to the difference between the control results when the light source is continuously lit and the current control is performed, and when the light source is intermittently lit and the current control is performed, the following results are obtained. It is possible to suppress a situation in which the density of the image formed on the page is different from that of the image formed on the second and subsequent pages.

Further, since the invention is a laser lighting sequence control method, it is possible to improve the print quality without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a first embodiment of the present invention.

FIG. 3 is a schematic diagram showing light emission timing of a laser diode in the first embodiment of the present invention.

FIG. 4 is a flowchart showing a second embodiment of the present invention.

FIG. 5 is a flowchart showing a third embodiment of the present invention.

FIG. 6 is a schematic diagram showing light emission timing of a laser diode in a conventional example.

FIG. 7 is a circuit diagram showing a circuit configuration of a laser light emitting circuit in a conventional example.

FIG. 8 is a flowchart showing an operation procedure of APC in a conventional example.

FIG. 9 is a schematic diagram illustrating a scanning position of a laser beam during APC in a conventional example.

FIG. 10 is a schematic diagram of another example illustrating a scanning position of a laser beam in APC in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Constant current diagram 2 Switching circuit 3 Amplifier 6 Laser diode 7 Photodiode 8 Resistance 11 Laser light source 12 Laser light detection means 13 Light quantity control means 14 Timing control means 15 Output level setting means 16 Optical output level judgment means 17 Photoconductor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-189560 (JP, A) JP-A-2-151173 (JP, A) JP-A-62-116071 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) B41J 2/44 G02B 26/10 H04N 1/113

Claims (4)

(57) [Claims] 1. An image forming apparatus that forms an image using a light source that generates a light beam, comprising: a detecting unit configured to detect a light amount of the light source; and a light amount detected by the detecting unit is set to a target value. Current control means for controlling the drive current supplied to the light source, and prior to image formation, the light source is continuously lit to perform current control by the current control means, and thereafter, between pages. An image forming apparatus characterized in that the light source is intermittently illuminated as in the case of current control, a drive current for image formation is determined by the current control means, and image formation is started using the determined drive current. . A scanning unit that scans a light beam generated from the light source, wherein the current control performed between the pages is performed during a period in which the light beam scans a non-image area. Characterized by
The image forming apparatus according to claim 1 . 3. The image forming apparatus according to claim 1, wherein when forming a one-page image, current control performed by intermittently emitting light from the light source is canceled prior to image formation. 4. A light source comprising: detecting means for detecting a light amount of a light source; and current control means for controlling a drive current supplied to the light source so that the light amount detected by the detecting means becomes a target value. A light amount control method for a light source of an image forming apparatus that forms an image using a light beam generated by the light source, wherein the light source is continuously illuminated prior to image formation, and current control is performed by the current control unit. After that, similarly to the light amount control performed between pages, the light source is intermittently made to emit light, and the current control means determines a drive current at the time of image formation. The image formation is performed using the determined drive current. A light amount control method comprising a step of starting.