JPH08279878A - Image forming device - Google Patents

Abstract

PURPOSE: To detect an error in a laser diode with high accuracy by providing a means allowing a data changeover means to select binary or multi-value data onto an engine board. CONSTITUTION: An engine board 32 is provided with a data changeover circuit 36, a laser diode lighting signal generating circuit 37 and a valid image area signal generating circuit 38 and has a function of outputting image data 39(A) from a controller board 31 being an input to the data changeover circuit 36 or laser diode lighting signal data 40(B) from a laser diode lighting signal generating circuit 37 to an output terminal (0) depending on a state of a selection signal input (S). Multi-value data (A) being the image data in the valid image area or binary data (B) generated on the engine board at the outside of the valid image area are selected depending on the function and fed to an LD board 33.

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, it facilitates the detection of an abnormality in a laser diode in an apparatus capable of expressing multi-level gradation without complicating the circuit configuration of the entire apparatus and It relates to means for improving accuracy.

[0002]

2. Description of the Related Art In recent years, page printers typified by laser printers have become available that are capable of gradation expression. The gradation expression method of a laser printer capable of gradation expression is generally such that, in addition to dither processing, the emission time of the laser diode is controlled for each dot so that pixel dots also have gradation. Target. The control of the light emitting time of the laser diode is performed by, for example, pulse width modulation (hereinafter, pulse width modulation) for controlling the pulse width of the power supplied to the diode.
This is called PWM). In this system, the image image data transmitted / received between the controller board, the engine board and the optical writing unit is 1 bit (binary data), which is a level that cannot be expressed in the conventional gradation.
It had the same data format as The Printer.

Usually, in a laser printer, a writing signal (hereinafter referred to as a VIDEO signal) transferred between an engine board and an optical writing unit is an optical signal from a controller board within an effective image area. Not only the image image data passed to the writing unit,
A laser diode lighting signal for horizontal synchronization detection (hereinafter referred to as / DETP) and a toner density detection pattern generation signal (hereinafter referred to as P pattern) which are generated on the engine board even outside the effective image area. It also has a signal component such as). In addition to the above, signals generated on the engine board include controller board signals.
Regardless of the presence or absence of the code, a test image signal or the like output within the effective image area is also required to perform a test print independently of the engine unit.

Vs created on these engine boards
The IDEO signal is a binary signal even in the conventional laser printer that cannot express the gradation. Further, in the PWM type tunable laser printer, since the image signal to be handled is binary, a special means is required also when synthesizing the signal component other than the image image data into the VIDEO signal. do not do. On the other hand, the laser printers currently being developed aim at higher quality gradation expression, and image image data between the controller board and the engine board and the engine board and the optical writing unit. A method (hereinafter referred to as PM control) in which the VIDEO signal between them is made multi-valued data of 2 bits or more and the lighting light amount of the writing laser diode is also controlled for each dot in addition to the conventional PWM control has been studied. ing.

However, in the PM control method currently being studied as described above, it is necessary to use multi-valued data for the image image data, but other data created on the engine board is originally required. It is not necessary to make multi-valued data, and in order to make these multi-valued data in order to ensure consistency with image image data, a new circuit configuration of the engine board and complication cannot be avoided, and the device There was a possibility that it would lead to an increase in size and cost.

Further, the following problems also occur when detecting an abnormal light emission amount of a laser diode (hereinafter referred to as an LD error) which has been conventionally performed. That is,
If there is an abnormality in the laser diode and its drive circuit, the specified light emission amount cannot be obtained, and normal printing and drawing cannot be performed. Therefore, conventionally, in order to detect an abnormality in the laser diode at an early stage, the laser diode is caused to emit the maximum light outside the effective image area, that is, in an area where an image is not actually drawn, and the amount of light is regulated. Control is performed to confirm that the value is greater than or equal to the value. In conventional binary control,
The diode has only two states of ON and OFF, and the light emission amount may be confirmed in the ON state which is the maximum light emission outside the effective image area.

On the other hand, in the case of multi-valued data, it is always performed in real time regardless of whether it is inside or outside the effective image area.
As the D error detection, when the driving current of the laser diode in which the light emission amount changes variously according to the multivalued data exceeds a predetermined value, for example, 100 mA, the LD is transferred from the optical writing unit to the engine board. An error signal is output, and as a result, an LD error signal is generated both inside and outside the effective image area. At this time, in order to reliably detect the LD error, it is convenient to maximize the light emission amount of the laser diode at the timing when the engine board can detect the LD error. Controller board
This is not possible in the effective image area where the image image data of the image is output to the VIDEO signal. That is,
If the image data is ignored in the effective image area and maximum light emission is performed, the image to be printed is changed. To perform the same control outside the effective image area,
A timing signal indicating that it is outside the effective image area is required in the diode control unit. However, in the currently used apparatus, the interface between the controller board and the engine board (usually In VIDEO I / F), a signal indicating an effective image area is often not obtained. However, in order to adopt the above method, in order to independently provide a means for detecting the outside of the effective image area in the engine board, not only a new design is required, but also versatility is lost and different types are used. A different unit is required for each device, which may increase the cost of the device.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and image image data can be switched between 1 bit and multi-valued bits, and the laser light amount for each pixel dot can be changed. In the image forming apparatus for controlling the tone and expressing the gradation, the image forming apparatus capable of detecting the error of the laser diode without causing the circuit configuration of the engine board to be complicated and having a circuit configuration having general versatility Is intended to provide.

[0009]

In order to achieve the above object, the invention according to claim 1 provides a controller board for receiving print data from a host computer and developing it into image image data, and a mechatronic control for an engine section. The controller board and the engine board have an engine board for supplying the image image data received from the controller board to the optical writing unit equipped with a laser diode and the like.
For example, a laser printer capable of expressing a gradation by controlling the light quantity of the laser diode for each dot corresponding to the case where the image image data transferred between the terminals is 1 bit and 2 bits or more. In an image forming apparatus, a timing signal generating means for indicating an effective image area on an engine board, a data switching means for switching image image data to be transferred to the optical writing unit between multivalued data and binary data, and a controller. When multi-valued data is selected as the image image data between the board and the engine board, the data switching means is switched to multi-valued at the timing within the effective image area, and the effective image area It is characterized in that a means for switching the data switching means to a binary value is provided at an external timing. According to a second aspect of the present invention, in the image forming apparatus, the laser diode is provided in the writing unit by maximizing the light emission amount of the laser diode in the 2-bit area of the image data outside the effective image area. It is characterized in that it is provided with means for detecting the abnormal light emission amount.

[0010]

According to the first aspect of the present invention, the controller board for receiving the print data from the host computer and developing the image data into the image image data, and the mechatronic control of the engine part and the image received from the controller board. Image
It has an engine board for supplying image data to an optical writing unit equipped with a laser diode, etc., and the case where the image image data transferred between the controller board and the engine board is 1 bit and 2 In an image forming apparatus such as a laser printer capable of expressing a gradation by controlling the light quantity of a laser diode for each dot corresponding to the case of more than a bit, the timing showing the effective image area on the engine board. The signal generating means, the data switching means for switching the image image data to be transferred to the optical writing unit between the multi-value data and the binary data, and the image image data between the controller board and the engine board. When multi-valued data is selected, the data switching means is switched to multi-valued at the timing within the effective image area, and the timing outside the effective image area is changed. Since in the ring with a means for switching the data switching means into a binary, it switches the image data into binary data in the effective image area outside, L
It becomes possible to perform D error detection.

According to a second aspect of the invention, in the image forming apparatus, the amount of light emitted from the laser diode is maximized in a 2-bit area of image data outside the effective image area,
Since a means for detecting an abnormality in the light emission amount of the laser diode provided in the writing unit is provided, it is possible to detect the laser error by setting the laser diode to the maximum light emission state by the binary data. Therefore, the accuracy is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional configuration diagram of a laser printer as an embodiment of an image forming apparatus to which the present invention is applied. In the figure, reference numeral 1 is an image forming apparatus main body including an upper case 1a and a lower case 1b, and 2 is a shaft for rotatably supporting the upper case 1a with respect to the lower case 1b. Belt-shaped photoconductors 4a to 4c installed in the substantially central portion of the image forming apparatus main body 1 are rollers for driving and guiding the photoconductor 3, and a known charging means 5 is provided around the photoconductor 3. , Electrophotographic forming process means including developing means 6, transfer means 7, and cleaning means 8 are arranged. In addition,
This electrophotographic process means is further provided with an optical writing means which will be described later. Further, 9 is a sheet feeding cassette, 10 is a sheet feeding roller, 11 is a pair of registration rollers, 12 is a fixing unit including a fixing roller 12a and a pressure roller 12b, 13 is a discharging roller, 14 is a discharging tray, and 15 is a photosensitive member. An optical writing unit arranged below the body 3 and a base cover 16 and a scanner motor 18, a polygon mirror 19, an fθ lens 20, a mirror 21, and an outer portion of the developing unit 6 provided in the space. And a cylinder lens 22 provided in the.

In the laser printer, a sheet (not shown) fed from the sheet feeding cassette 9 by the sheet feeding roller 10 is conveyed to the upper side of the photoconductor 3 by the registration roller pair 11 with a timing. The photoconductor 3 is driven and guided by the rollers 4a to 4c in the counterclockwise direction indicated by the arrow in the figure, and the surface of the photoconductor 3 is uniformly charged by the charging means 5, and then the laser light L from the optical writing means 5 is irradiated. By doing so, an electrostatic latent image is formed. When the electrostatic latent image passes through the developing means 6, it is visualized by toner (not shown) and transferred onto the sheet conveyed to the upper portion of the photoconductor 3 via the transfer means 7. The sheet transferred as described above is conveyed between the fixing roller 12a and the pressure roller 12b of the fixing unit 12 and the visible image is fixed. The sheet that has passed through the fixing unit 12 is ejected to the sheet ejection tray 14 by the sheet ejection roller 13.

Explaining the method of forming an electrostatic latent image by the laser light L, the laser light L blinking in response to an image information signal output from a laser unit (not shown) is directed to the polygon mirror 19. It is incident and polygon scanning is performed by repeating scanning within a certain angle range. The deflected laser light L is f
An image is linearly formed at the optical writing position on the photoconductor 3 by the θ lens 20, and is corrected so as to move at the projection point at a constant speed. The light enters the photoconductor 3 via the mirror 21 and the cylinder lens 22. Main scanning is performed by deflection of the incident laser light L, and sub scanning is performed by rotation of the photoconductor to write an image corresponding to the image information signal, thereby forming an electrostatic latent image. The series of controls are executed by the engine board 23 provided inside the apparatus.

FIG. 2 is a schematic block diagram showing an embodiment of the engine board according to the present invention. In the figure, 31 is a controller board, which is a host computer.
The image data for printout is created from the print data received from the printer and is supplied to the engine board. Reference numeral 32 is an engine board, which is a signal for writing a laser diode for writing such as / DETP, P pattern, LD error detection output, in addition to the image image data received from the controller board 31. Is added to the image image data and supplied as VIDEO data to the LD board. Reference numeral 33 denotes an LD board, which is provided inside the optical writing means and which has an engine board 3
The built-in laser according to the VIDEO signal received from
This is to turn on the diode. The controller board 31 and the engine board 32 are connected by a connector 34, and the engine board 32 and the LD board 33 are connected by a harness 35.

The engine board 32 has a data switching circuit 36 and a laser diode lighting signal generating circuit 37.
And an effective image area signal producing circuit 38. The data switching circuit 36 produces image image data (multi-valued data) and a writing laser diode lighting signal (2) produced by the engine board. Value data) and output as a VIDEO signal. Reference numeral 39 in the figure is image image data supplied from the controller board 31 to the engine board 32, and is a 1-bit binary signal in a conventional printer that cannot express gradation or a printer that only uses PWM control. There is P in addition to PWM
In a tone-representable printer that performs M control, multi-valued data of 2 bits or more is used. Further, the writing laser diode lighting signal 40 supplied from the laser diode lighting signal generating circuit 37 to the data switching circuit 36 is binary data, and the effective image area signal creating circuit 38 outputs the effective image area. The timing signal 41 shown is output. The LD board 33 is provided with a laser diode drive circuit 43 for driving the laser diode 42.

The features of the apparatus constructed as described above are that the image image data 39 (A) from the controller board 31 which is the input of the data switching circuit 36 and the laser diode lighting signal generation circuit 37 are used. The laser diode lighting signal data 40 (B) is output from the output terminal (0) depending on the state of the selection signal input (S). With this function, multi-valued data (A) which is image image data in the effective image area and binary signal (B) signal generated on the engine board outside the effective image area are selected. And supply it to the LD board. Therefore, VIDEO
The signal contains multi-valued data according to the image data in the effective image area, and the laser diode controls the light emission amount based on the gradation specified for each dot, and outside the effective image area. Turns on / off a 1-bit binary value,
In the ON state, the maximum light emission state is controlled.

In the case where the engine board 32 is independently subjected to the test print regardless of the presence or absence of the controller board 31, the laser diode lighting signal generating circuit 37 performs the test even in the effective image area. The writing laser diode lighting signal may be controlled according to the print data. Since the circuit of this part can use the conventional binary data circuit as it is,
It can be shared with other devices, and when performing test printing, binary signals are generated in both the inside and outside of the effective image area, and the data switching circuit 36 always selects the input (B). You can control to. In the case of actually implementing the present invention, the engine board 32 can be further miniaturized by integrating the circuit in the broken line in the engine board 32 of FIG. 2 with a gate array or the like. You can

FIG. 3 is a diagram showing a specific embodiment of the data switching circuit 36. In the figure, 301 is a multiplexer, which is an ID input to the input terminals A0 to A3.
0 to ID3 are image image data A supplied from the control board, and second input terminals B0 to B
A laser diode lighting signal 1 bit generated in the engine board is commonly supplied to ED3 as ED0 (B) input, and VD0 to VD3 are output from output terminals O0 to O3. The S terminal supplies a signal indicating the inside and outside of the effective image area, and is created by the effective image area generation circuit 38 shown in FIG. 2 as described above, and is shown as / VARID in this example. In this circuit, / VARID becomes LOW level in the effective image area, and
Input (A0-A3) is selected, multi-valued data is selected for each dot in accordance with image image data, and O output (O
0-O3) to LD board VIDEO signal VD0-V
Supplied as D3. That is, as in this example, VD
In the case of 4-bit multi-valued data of 0 to VD3, the laser diode emits the maximum light when all of the 4 bits are HIGH,
When all 4 bits are LOW, the laser diode is turned off, and light is emitted at 16 different values depending on the bit value. When / VARID is HIGH, it indicates that it is outside the effective image area. At that time, B input is selected and binary data is output for each dot. Everything goes HIGH or LOW, and the laser diode either emits maximum light or goes out.

FIG. 4 shows an effective image area creating circuit (3 in FIG. 2).
It is a figure which shows the specific circuit example of 8). 40 in the figure
Reference numeral 1 is a flip-flop whose engine input is connected to its D input.
CPU data is input to the counter 402, and a counter 402 has a reset input R with a synchronization signal (/ V) in the sub-scanning direction.
SYNC) is supplied, and a synchronization signal (/ DETP) signal in the main scanning direction is supplied to the clock input (CK). Four
A magnitude comparator 03 supplies the output of the counter 402 to the A input and the output of the flip-flop 401 to the B input, and when both data values match, the A / B signal goes low. To do.

404 is a second flip-flop,
When the D input becomes LOW, the state at that time is held until the reset input (R) becomes LOW and is output from the terminal Q. Reference numeral 405 is the CPU data of the engine board supplied to the third flip-flop terminal D, and 406 is the second magnitude comparator, which is the first flip-flop supplied to the terminal A similarly to the above 403. When the output of 402 and the output data of the third flip-flop 405 supplied to the terminal B match, a LOW signal is generated at the output of / A = B. A fourth flip-flop 407 holds the state value at that time when the signal supplied to the terminal D becomes LOW, and outputs it from the terminal Q until the data at the reset terminal R becomes LOW.

Reference numeral 408 is a fifth flip-flop,
The CPU data of the engine board is supplied to the terminal D and 4
Reference numeral 09 denotes a second counter. The reset terminal R is supplied with a synchronizing signal (/ DETP) in the main scanning direction, and the clock terminal CK is supplied with a system clock signal of the engine board. 410 is a third magnitude comparator, and when the data of the A input and the B input match / A =
Set B output to LOW. A sixth flip-flop 411 holds the state at that time when the terminal D becomes LOW until the reset terminal R becomes LOW, and outputs it from the terminal Q. Reference numeral 412 is a seventh flip-flop, and the CPU data of the engine board is supplied to the terminal D. 41
Reference numeral 3 is a fourth magnitude comparator, which makes the output of A / B LOW when the data of the A input and the data of the B input match. Reference numeral 414 denotes an eighth flip-flop, which has a terminal D
When LOW becomes LOW, the state at that time is reset terminal R
Hold until LOW and output from terminal Q. 41
Gate circuits 5 and 416 are gate circuits.

The operation of the above configuration will be described. When the CPU of the engine board receives the designation of the paper size from the controller board at the start of printing, the value of the effective image area starting point in the sub-scanning direction is sent to the flip-flop 401.
Further, the value of the effective image area end point in the sub-scanning direction is set in the flip-flop 405. As a result, the value of the effective image area start point in the sub-scanning direction is held by the flip-flop 401 and input to the terminal B of the magnitude comparator 403, and the value of the effective image area end point in the sub-scanning direction is the flip-flop. It is held at 405 and input to the terminal B of the magnitude comparator 406.

Upon writing, when / VSYNC is received, the counter 402 is reset to the initial state /
Count the number of DETP pulses. That is, the writing lines in the sub-scanning direction are counted. Counter 40
The output of 2 is the magnitude comparators 403 and 40.
Since it is connected to the terminal A of No. 6, when the count value reaches the value set in the flip-flop 401, that is, the effective image area starting point in the sub-scanning direction, the magnitude
The decomparator 403 sets / A = B to LOW, and the flip-flop 404 holds the state and outputs it from the terminal Q.

Therefore, at this time, the flip-flop 403
The terminal Q (417) of is changed from HIGH to LOW, and the LOW state is maintained. At this time, the flip-flop 407 reset input R changes from the LOW state to the HIGH state, so that the input of the terminal D is held and the terminal Q can be output. Therefore, the value of the counter 402 is the flip-flop 4
When the value of the effective image area end point in the sub-scanning direction set to 05 is reached, the magnitude comparator 406 outputs / A.
= B is set to LOW, the flip-flop 407 holds the state and outputs from the terminal Q. Here, the terminal Q output of the flip-flop 407 is the flip-flop 4
Since it is connected to the reset terminal R of No. 04, it is reset when the reset terminal becomes LOW, and the output of the terminal Q becomes the initial state. Therefore, the above 417 (Q terminal output of the flip-flop 404) changes from LOW to HIGH at this time. According to the above control, one input signal to the gate 415 changes from HIGH to LOW at the start point of the effective image area in the sub-scanning direction, and further changes from LOW to HIGH at the end point of the effective image area in the sub-scanning direction. Changes to.

Since / VSYNC is output prior to writing in the sub-scanning direction as long as printer output continues, the above sequence is repeated while printout continues. Here, the signal 417 is an effective image area signal (/ FGATE) in the sub-scanning direction. Further, the circuit shown in FIG. 4 has the same circuit configuration as the upper and lower sides, and the upper circuit similarly generates an effective image area signal in the sub-scanning direction and the lower circuit in the main scanning direction.

That is, when the CPU of the engine board receives the designation of the paper size from the controller board during printing, the value of the effective image area start point in the main scanning direction is sent to the flip-flop 408 and the main scanning. The value of the end point of the effective image area in the direction is set in the flip-flop 412.
As a result, the value of the effective image area start point in the sub-scanning direction is held by the flip-flop 408 and input to the terminal B of the magnitude comparator 410, and the value of the effective image area end point in the main scanning direction is the flip-flop. 412, and terminal B of the magnitude comparator 413.
Is input to

When writing to each line, / DETP
When the counter 409 is received, the counter 409 is reset to the initial state and counts the number of system clock pulses of the engine board. That is, the scanning time in the main scanning direction is counted asynchronously with the controller board.
The output of the counter 409 is the magnitude comparator 4
Since it is connected to the terminals A of 10 and 413, the count value is the value set in the flip-flop 408,
That is, when the effective image area start point in the main scanning direction is reached,
The magnitude comparator 410 sets / A = B to LOW, and the flip-flop 411 holds the state and outputs it from the terminal Q.

Therefore, at this time, the flip-flop 411
The terminal Q (419) of is changed from HIGH to LOW, and the LOW state is maintained. At this time, since the reset input R of the flip-flop 414 changes from the LOW state to the HIGH state, the input of the terminal D is held and the terminal Q can be output. Therefore, when the value of the counter 409 becomes the value of the effective image area end point in the main scanning direction set in the flip-flop 412, the magnitude comparator 413 outputs /
A = B is set to LOW, the flip-flop 414 holds the state and outputs from the terminal Q.

Here, the terminal Q of the flip-flop 414
Since the output is connected to the reset terminal R of the flip-flop 411, it is reset when the reset terminal becomes LOW, and the terminal Q output becomes the initial state. Therefore, the above-mentioned 419 (Q terminal output of the flip-flop 411) changes from LOW to HIGH at this time. According to the above control,
The other input signal of the gate 415 changes from HIGH to LOW at the start point of the effective image area in the main scanning direction, and further changes from LOW to HIGH at the end point of the effective image area in the main scanning direction.
Change to H.

Since / DETP is output prior to writing of each line in the main scanning direction as long as printer output continues, the above sequence is repeated while printout continues. Here, the signal 419 is set as an effective image area signal (/ LGATE) in the main scanning direction.

As described above, the signals indicating the effective image area in the sub-scanning direction and the main scanning direction are / FGATE and / LG.
When obtained as ATE, the gate 415 that inputs these two signals is the LO when both of the above two signals are LOW.
Output W. That is, the LOW signal is generated only for the effective image area in the sub scanning direction and the main scanning direction.
Further, the gate 416 inputs the output of the gate 415 and the / E signal, of which the / E signal is the engine boat.
It is possible to freely set LOW and HIGH by the CPU of the driver. Further, as shown in FIG. 3, it is the output of the gate 416 /
The VARID signal is connected to the S terminal of the multiplexer 301, so if this signal is LOW, ID0-ID
3 multi-valued data, and if this / VARID signal is HIGH, ED0 is selected. Furthermore, C of the engine board
If the / E signal is made HIGH by the PU, the gate 416 will always output HIGH regardless of the level of one terminal signal, so the / VARID signal will be in the HIGH state and ED0 will always be selected. . Therefore, the CPU of the engine board can always select the binary data regardless of whether it is inside or outside the effective image area, which is convenient when performing a print test.

FIG. 5 shows an example of the waveform of each signal, where the / E signal is in the LOW state. That is, (a) is a / VSYNC signal, which is a vertical synchronization signal for printing out, and a general VIDE signal.
In the O I / F, it is supplied from the controller board to the engine board. Further, (b) is a / DETP signal, which is a horizontal synchronizing signal at the time of printout, and is supplied from the engine board to the controller board in a general VIDEO I / F.

(C) is the / FGATE signal, which is normally generated inside the controller board, but in the present invention, it is generated independently inside the engine board. This signal is not supplied from the controller board to the engine board in a general VIDEO I / F. In the example shown here, the effective image area start point in the sub-scanning direction is 2, and the effective image end point in the sub-scanning direction is n-2.

(D) is the / DETP signal, which is the same as that shown in FIG. 2, but in relation to the description of other signals,
The cycle is enlarged and displayed. (E) is CPU CLK
It is a signal and a system clock for driving the CPU in the engine board. Here, the horizontal scanning position is used as a reference clock for designating based on the / DETP signal (Fig. 5-e). ing. (F) is the / LGATE signal, which normally exists in the controller board, but in a general VIDEO I / F, it is not supplied from the controller board to the engine board, and in the present invention, Is provided inside the engine board with means for generating this signal independently of the controller board. In this example, the effective image area start point in the main scanning direction is 4 and the effective image area end point in the main operation port is n-2. (G) is / VARI
It is a D signal and becomes LOW when both / FGATE and / LGATE are LOW. In this example, this signal is
It switches to select multi-valued data when LOW and binary data when HIGH.

[0036]

As described above, according to the present invention,
First, it has a controller board for developing image image data and an engine board for supplying to an optical writing unit equipped with a laser diode, etc., and the case where the image image data is 1 bit. In an image forming apparatus capable of expressing gradation by controlling the light quantity of a laser diode for each dot corresponding to the case of 2 bits or more, a timing signal generating means for indicating an effective image area on an engine board, Data switching means for switching the image image data transferred to the optical writing unit to multi-valued data and binary data;
When multi-valued data is selected for the image image data between the controller board and the engine board, the data switching means is switched to multi-valued at the timing within the effective image area, and the effective image Since the means for switching the data switching means to the binary value is provided at the timing outside the area, it becomes possible to switch the image data to the binary data outside the effective image area and perform the LD error detection, which is versatile. Use the unit you have,
Highly accurate laser diode error detection is possible.

According to a second means of the present invention, in the image forming apparatus, the amount of light emitted from the laser diode is maximized in a 2-bit area of image data outside the effective image area,
Since a means for detecting an abnormality in the light emission amount of the laser diode provided in the writing unit is provided, it is possible to detect the laser error by setting the laser diode to the maximum light emission state by the binary data. Therefore, the accuracy is further improved.

[Brief description of drawings]

FIG. 1 is a sectional configuration diagram of a laser printer showing an embodiment of an image forming apparatus to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration example of a main part in an image processing apparatus adopting the present invention.

FIG. 3 is a diagram showing a specific configuration example of a data switching circuit according to an embodiment of the present invention.

FIG. 4 is a block diagram showing an embodiment of an effective image area creating circuit according to the present invention.

5A to 5G are diagrams showing signal waveform examples in an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Axis, 3 ... Photoconductor, 4a,
4b, 4c ... Rollers, 5 ... Charging means, 6 ... Developing means,
7 ... Transfer means, 8 ... Cleaning means, 9 ... Paper feeding cassette, 10 ... Paper feeding roller, 11 ... Registration roller, 12 ... Fixing section, 13 ... Discharge roller, 14 ... Discharge tray, 15 ... Optical writing means , 16-base cover, 17-base cover space, 18-scanner motor, 19-polygon mirror, 20-fθ lens,
21 ... Mirror, 22 ... Cylinder lens, 23 ... Engine board, 31 ... Controller board, 32 ... Engine board, 33 ... LD board, 34 ... Connector,
35 ... Harness, 36 ... Data switching circuit, 37
... laser diode lighting signal generating circuit, 38 ... effective image area creating circuit, 39 ... image image data, 40 ...
Laser diode lighting signal data, 41 ... Effective image area timing signal, 42 ... Laser diode, 43 ... Laser diode drive circuit 301 ... Data switching circuit, 401, 404, 40
5, 407, 408, 411, 412, 414 ... Flip-flops, 402, 409 ... Counters, 403,
406, 410, 413 ... Magnitude comparator
415, 416 ... Gate, 417 ... Sub-scanning direction effective image area signal, 419 ... Main scanning direction effective image area signal.

Claims (2)

[Claims] 1. A controller board which receives print data from a host computer and develops it into image image data, and performs mechatronic control of an engine section and also stores image image data received from the controller board. It has an engine board for supplying to an optical writing unit equipped with the diode, etc., and has a controller board and an engine board.
For example, a laser printer capable of expressing a gradation by controlling the light quantity of the laser diode for each dot corresponding to the case where the image image data transferred between the terminals is 1 bit and 2 bits or more. In an image forming apparatus, a timing signal generating means for indicating an effective image area on an engine board, a data switching means for switching image image data to be transferred to the optical writing unit between multivalued data and binary data, and a controller. When multi-valued data is selected as the image image data between the board and the engine board, the data switching means is switched to multi-valued at the timing within the effective image area, and the effective image area An image forming apparatus comprising means for switching the data switching means to binary at external timing. 2. A means for maximizing the light emission amount of the laser diode in the 2-bit area of the image data outside the effective image area to detect an abnormality in the light emission amount of the laser diode of the writing unit. The image forming apparatus according to claim 1, wherein: