JP2000238319A - Optical scanning device - Google Patents

Abstract

(57) [Summary] A writing position detection sensor can be disposed at an arbitrary position outside an image area of a photosensitive drum.
An optical scanning device capable of performing color shift correction within one pixel clock is also provided. SOLUTION: When a deflected light beam enters a specific position on the path of the light beam, it becomes a reference signal for determining a writing position of image data in a main scanning direction on a surface to be scanned of a photosensitive member. A writing position detection sensor 34 that outputs a detection signal, and a phase shift amount setting circuit 2 that sets the phase shift amount of the detection signal of the writing position detection sensor
02, a phase shift control circuit 206 that shifts the phase of the detection signal according to the phase shift amount set by the phase shift amount setting circuit, and image data output based on the output timing of the output signal of the phase shift control circuit. And an image data output timing control circuit 114.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of modulating a laser beam according to image information and scanning a laser beam on a surface to be scanned such as a photoreceptor.
The present invention relates to an optical scanning device used for an image recording device such as a laser printer or a digital copying machine that records an image by exposing.

[0002]

2. Description of the Related Art FIG. 8 shows the configuration of an optical system in an image recording apparatus such as a laser printer. In the figure, a light beam emitted from a laser diode 10 is converted into parallel light by a collimator lens 12, shaped by a slit 14, and then guided to a polygon mirror 24 via a cylinder lens 20. Thereafter, the light beam is rotated by a scanner motor (not shown).
, The scanning speed is converted to a constant value by the f · θ lens 26, an image is formed on the photosensitive drum 30 so as to have a predetermined width in the main scanning direction, and the cylinder mirror 2
8 forms an image on the photosensitive drum 30 so as to have a predetermined width in the sub-scanning direction. With this configuration, a light beam having a constant beam shape can be transferred to the photosensitive drum 3.
It becomes possible to scan at a constant speed on zero.

Further, the optical scanning device of the above image recording apparatus is
Even if the surface accuracy of the polygon mirror 24 fluctuates, the position of the image area on the photosensitive drum 30 where the image data is written on the photosensitive drum 30 is adjusted so that the writing position of the image data (including character information) does not shift in the main scanning direction. Prior to scanning, when a light beam emitted from the laser diode 10 is received, a scanning start position on the photosensitive drum 30, that is, a detection signal serving as a reference of a writing position of image data in the main scanning direction is transmitted to an f · θ lens. 26, reflection mirror 3
2. A control circuit 100 that obtains a reflected beam from the deflection surface of the polygon mirror 24 via the cylinder lens 33 and receives the reflected beam from the deflecting surface of the polygon mirror 24, and controls the writing operation of the image data. The configuration is such that writing of image data is started after a certain time has elapsed.

FIG. 9 shows the configuration of the control circuit 100, and FIG. 10 shows the operation timing at the start of recording of image data. In FIG. 9, a control circuit 100 synchronizes an image clock generator 102 that generates an image clock, which is a synchronization signal when writing image data on the photosensitive drum 30, with the image clock and a detection signal / HSYNC of a writing position detection sensor. Synchronization control circuit 104 and the synchronization control circuit 10
Counter 1 for counting the number of image clocks output from
06, a timing setting circuit 108 for setting the timing of writing image data, and a timing setting circuit 1
Register 110 in which the value set by 08 is set
A comparator 112 for comparing the count value of the counter 106 with the set value of the register 110; and an image clock for fetching an image clock and starting output of image data based on an output signal of the comparator 112. And an image data output timing control circuit 114 for controlling the timing.

In the above configuration, the control circuit 100 includes:
At time ti, the detection signal (//
HSYNC) is input (FIG. 10A), the counter 106 is reset by the detection signal, and the counter 106 outputs the image clock (IMG-CLK) synchronized with the detection signal output from the synchronization control circuit 104. Start counting (Fig. 1
0 (B)). The count value of the counter 106 is stored in the register 11
At the time tn when the set value set to 0 is reached, the image data output timing control circuit 114 sends the image data (IMG-DAT
The output of A) is started, and output is performed until time tn + tw (tw is an image data output period) (FIG. 10C).

By adjusting the output timing of the image data and outputting the image data in this manner, the write start position of each scanning line on the photosensitive drum 30 (FIG. 8) can be kept constant.

[0007]

However, in the above-described conventional optical scanning device, the signal is a reference signal for determining a writing start position (scanning start position) when writing image data in the main scanning direction of the photosensitive drum. It is necessary to dispose a writing position detection sensor for outputting a detection signal of a light beam immediately before scanning an image area where image data is written on the photosensitive drum, and a scanner motor for rotating a polygon mirror 24 for deflecting the light beam. Once the rotation direction is determined, the location of the writing position detection sensor is physically limited in relation to the optical system for scanning the light beam,
There is a problem that it is difficult to reduce the size of the device and the cost increases.

In a color laser printer, the writing position of each color in the image data can be adjusted only in units of one image clock. This displacement causes image color misregistration, resulting in a problem that the image quality is significantly reduced.

The present invention has been made in view of such circumstances, and is a light signal which is a reference signal for determining a write start position (scan start position) when writing image data in the main scanning direction of the photosensitive drum. An optical scanning device capable of disposing a writing position detection sensor that outputs a beam detection signal at an arbitrary position outside the image area of the photosensitive drum and performing color shift correction within one image clock is provided. The purpose is to provide.

[0010]

According to a first aspect of the present invention, there is provided a light source for emitting a light beam modulated based on image data, and a light source for emitting a light beam emitted from the light source. In an optical scanning device that deflects by a deflecting unit and writes image data by scanning on a surface to be scanned of a photoconductor, when a light beam deflected by the deflecting unit enters a specific position on a path of the light beam A writing position detection means for outputting a detection signal serving as a reference signal for determining a writing position of image data in the main scanning direction on the surface to be scanned of the photosensitive member; and a phase shift of a detection signal of the writing position detection means. Phase shift amount setting means for setting an amount, and a phase for shifting the phase of the detection signal according to the phase shift amount set by the phase shift amount setting means A shift control means, and having an image data output timing control means for controlling the output timing of the image data so as to output the image data based on the output timing of the output signal of the phase-shift control means.

According to a second aspect of the present invention, there is provided the optical scanning device according to the first aspect, wherein the phase shift amount setting means includes: The set amount of phase shift is determined based on a positional relationship between a position where the writing position detecting means is provided and a writing position of image data on the photoconductor.

According to a third aspect of the present invention, in the optical scanning device of the second aspect, the phase shift amount set by the phase shift amount setting means is further fine within one image clock. It is determined to be adjusted.

According to the first to third aspects of the present invention, a light source for emitting a light beam modulated based on image data, and a light beam emitted from the light source are deflected by a deflecting unit to form a photosensitive member. In an optical scanning device that writes image data by scanning on a surface to be scanned, when a light beam deflected by the deflecting unit enters a specific position on a path of the light beam, the light beam is scanned on the surface to be scanned of the photoconductor. A signal serving as a reference signal for determining a write start position of image data in the main scanning direction is detected by a write start position detecting means, and a phase shift amount of the detection signal of the write start position detecting means is set by a phase shift amount setting means. Along with
Since the phase of the detection signal is shifted by the phase shift control means in accordance with the phase shift amount set by the phase shift amount setting means, the phase shift amount can be arbitrarily set, so that the main component of the photosensitive drum can be adjusted. A writing position detection sensor that outputs a light beam detection signal, which is a reference signal for determining a writing position (scanning start position) when writing image data in the scanning direction, is provided at an arbitrary position outside the image area of the photosensitive drum. And a color printer or the like can perform color shift correction within one image clock.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a configuration of a control circuit of the optical scanning device according to the present invention. The control circuit 200 shown in the figure corresponds to the control circuit 100 of the conventional optical scanning device shown in FIG. 9, and the same components are denoted by the same reference numerals. The configuration of the optical system constituting the optical scanning device according to the embodiment of the present invention is the same as that shown in FIG. The configuration of the optical scanning device according to the present embodiment is different from the conventional optical scanning device shown in FIGS. 8 and 9 in terms of the configuration, except that the phase shift amount setting circuit 202, the D / A converter 204, and the phase shift control circuit 206 are provided. And the detection signal of the position detection sensor 34
The point is that the HSYNC phase shift amount can be set arbitrarily.

In FIG. 1, a control circuit 200 includes an image clock generator 102 for generating an image clock, which is a synchronization signal for writing image data on the photosensitive drum 30, and a phase shift of a detection signal / HSYNC of the position detection sensor 34. A phase shift amount setting circuit 202 for setting the amount, a D / A converter 204, and a phase shift controller 206 for shifting the phase of the detection signal / HSYNC of the position detection sensor 34 based on the output of the D / A converter 204. And the image clock generator 10
Clock and phase shift control circuit 2 output from 2
The synchronization control circuit 104 synchronizes with the detection signal / SHIFTHSYNC of the position detection sensor 34 whose phase has been shifted by 06.
And the output signal of the phase shift control circuit 206 / SHIFT HSYN
Image data that starts outputting image data at the first output timing of the synchronous image clock / IMG CLK synchronized with the detection signal / SHIFT HSYNC of the position detection sensor 34 output from the synchronization control circuit 104 with reference to C And an output timing control circuit 114.

The phase shift amount of the detection signal of the writing position detection sensor 34 set by the phase shift amount setting circuit 202 depends on the arrangement position of the writing position detection sensor 34 and the writing position of the image data on the photosensitive drum 30 (FIG. 8). Is determined based on the positional relationship with Further, the phase shift amount set by the phase shift amount setting circuit 202 is determined so as to be finely adjusted within a range of one image clock.

Here, the writing position detecting sensor 34 is provided in the writing position detecting means of the present invention in the phase shift amount setting circuit 2.
02 corresponds to the phase shift amount setting means of the present invention, the phase shift control circuit 206 corresponds to the phase shift control of the present invention, and the image data output timing control circuit 114 corresponds to the image data output timing control means of the present invention. I do.

The operation of the control circuit 200 having the above configuration will be described with reference to the timing chart shown in FIG. In the above configuration, the phase shift amount of the detection signal / HSYNC of the writing position detection sensor 34 set as digital data by the phase shift amount setting circuit 202 is converted into analog data by the D / A converter 204, and the phase shift control circuit 206 Supplied to

The detection signal /
HSYNC is input to the phase shift control circuit 206 (see FIG. 2).
(A)), at time tj, the phase is shifted by the phase shift amount Δθm set by the phase shift amount setting circuit 202, and is input to the synchronization control circuit 104 (FIG. 2 (B)).

In the synchronization control circuit 104, the image clock output from the image clock generator 102 is synchronized with the detection signal / SHIFT HSYNC of the position detection sensor 34 whose phase has been shifted by the phase shift control circuit 206. The control circuit 104 detects the detection signal of the position detection sensor 34 / SHIF
Synchronous image clock / IMG CLK synchronized with THSYNC
Is output to the image data output timing control circuit 114 (FIG. 2C).

Image data output timing control circuit 114
Is the output signal of the phase shift control circuit 206 / SHIFT HSYN
The first output timing of the image clock / IMG CLK output from the synchronization control circuit 104 with reference to C, for example, the output of image data starts at time tk, and the time tk + tw (t
The output is continued until (w is an output period of the image data) (FIG. 2D).

Next, FIG. 3 shows an example of a specific configuration of a main part of the control circuit 200 shown in FIG. The same components as those of the control circuit shown in FIG. 1 are denoted by the same reference numerals. 3, the D / A converter 204 includes a D / A converter 210,
D / A converter 212, the output of D / A converter 210 and D
And an adder 214 for adding the output of the / A converter 212. A phase shift amount for coarse adjustment is set in the D / A converter 210, and a phase shift amount for fine adjustment is set in the D / A converter 212. D / A converter 210
And the D / A converter 212 may be constituted by one D / A converter. Specifically, for example, using a 16-bit D / A converter, the upper 8 bits perform D / A conversion of data indicating the amount of phase shift for coarse adjustment, and the lower 8 bits perform fine adjustment for data. D / of data indicating the amount of phase shift
A conversion may be performed. The phase shift amount for coarse adjustment is set, for example, to a value within one image clock, that is, within one pixel.

The phase shift control circuit 206 functions as a transistor Q2, a resistor R2, and a buffer, and corrects a voltage fluctuation caused by a fluctuation in the ambient temperature of a base-emitter voltage of the transistor Q2, and as a stabilized constant current source. A constant current circuit including a functional operational amplifier OP1, a current mirror circuit including transistors Q1 and Q3 and resistors R1 and R3, a resistor R4 and a capacitor C1,
Monostable multivibrators 216, 218,
Terminal Rx / of monostable multivibrator 218
It comprises a series circuit composed of a capacitor C2 and a resistor R5 connected between a power supply Vcc and ground for setting a delay time to Cx.

The output terminal of the current mirror circuit is connected to the control terminal Rx / Cx of the monostable multivibrator 216 via a resistor R4, and the output terminal of the writing position detection sensor 35 is connected to the input terminal / A of the monostable multivibrator 216. ing. The input terminal B of the monostable multivibrator 216 is connected to the power supply Vcc. Further, the output terminal / Q1 of the monostable multivibrator 216 is connected to the monostable multivibrator 2
18, the input terminal A of the monostable multivibrator 218 is grounded. Control terminal Rx / of monostable multivibrator 218
Cx is a capacitor connected between the power supply Vcc and the ground.
2, connected to the connection point between the capacitor C2 and the resistor R5 in the series circuit composed of the resistor R5.

The phase shift amount control circuit 2 having the above configuration
Operation 06 will be described with reference to the timing charts of FIGS. First, the phase shift setting circuit 202
As a result, the amount of phase shift is set in the D / A converter 204 as digital data. In the D / A conversion unit 204, D
A phase shift amount for coarse adjustment is set in the / A converter 210, and a phase shift amount for fine adjustment is set in the D / A converter 212. After these phase shift amounts are converted into analog data, they are added by the adder 214 and input to the phase shift control circuit 206.

In the phase shift control circuit 206, a stable current I1 (= Vs / R2) flows through the transistor Q2 by the analog voltage Vs according to the set phase shift amount.

On the other hand, the characteristics of the transistors Q1 and Q3 are the same, that is, VBE1 = VBE3, hFE1 = hFE3 (where VB
E is a base-emitter voltage, and hFE is a current amplification factor. ) And the base current IB of the transistors Q1 and Q3 is set to be substantially zero. If the current flowing through the transistor Q3 is I2 in order to form a current mirror circuit by the transistors Q1 and Q3, then I1 × R1 =
I2 × R3. Here, if R1 = R3, the same current flows through the transistors Q1 and Q3.

That is, the capacitor C is synchronized with the fall of the detection signal / HSYNC of the writing position detection sensor 34.
1, the potential of the control terminal Rx / Cx of the monostable multivibrator 216 drops to the ground level, and then is proportional to the input voltage level corresponding to the phase shift amount set by the phase shift amount setting circuit 202. The capacitor C1 is charged with the current having the current value thus set, and the potential of the capacitor C1, that is, the potential at the control terminal Rx / Cx of the monostable multivibrator 216 rises above the specified value Vth (FIG. 4A,
(B)).

On the other hand, the potential of the / Q1 output terminal of the monostable multivibrator 216 goes low at time tk in synchronization with the fall of the detection signal / HSYNC of the writing position detection sensor 34, and the potential of the control terminal Rx / Cx. Is charged and attains a high level at time tk + 1 when it reaches the specified level Vth (FIG. 4C). As a result, the potential Vn of the control terminal Rx / Cx of the monostable multivibrator 218
Is charged to a predetermined potential in the initial state, but at time t
Since the trigger is applied at k + 1, the voltage drops to the ground level, and then C is determined by the constants of the capacitor C2 and the resistor R5.
The battery is charged with a time constant of 2R5 (FIG. 4D).

The monostable multivibrator 218
Of the Q2 output terminal at time tk according to the input conditions described above.
Since the trigger is activated at +1 and drops to a low level, the control terminal Rx of the monostable multivibrator 218
/ Kx when the potential Vn is charged and exceeds the specified value Vth
A signal / SHIFT HSYNC which becomes high level at +2 is output (FIG. 4 (E)). The output signal / SHIFT HSYNC of the monostable multivibrator 218 is shifted by the phase shift amount Δθm from the output time point of the detection signal / HSYNC of the writing position detection sensor 34, that is, the falling time point tk + 1.

Here, the phase shift amount Δθm is Δθ1, Δθ1,
2. If the output voltages VS of the adder 214 when Δθ3 (Δθ1 <Δθ2 <Δθ3) are V1, V2, and V3, respectively, the magnitude relation is V1>V2> V3.

That is, the phase shift amount Δθm decreases as the voltage level of the output voltage VS of the adder 214 increases, because the charging speed of the capacitor C1 increases (FIG. 7).
(A), (C), (D), (E)). That is, the phase shift amount and the input voltage level corresponding to the phase shift amount set by the phase shift amount setting circuit 202 are in inverse proportion. By setting the phase shift amount arbitrarily as described above, the write timing of the image data can be arbitrarily set.

The phase shift control circuit 2 shown in FIG.
In 06, two monostable multivibrators are used to obtain the signal / SHIFT HSYNC, but instead of the monostable multivibrator 218, a rising detection type differential circuit for detecting the rising of the signal as shown in FIG. 220 may be used. The operation timing in this case is shown in FIG.

As described above, according to the embodiment of the present invention, as shown in FIG.
Even when the detection signal / HSYNC of the writing position detection sensor 34 is detected in 0), normal image writing can be performed. In a color laser printer or the like, D / A
By setting the phase shift amount within one pixel clock by the converter 212 in accordance with the color shift amount, it becomes possible to correct the color shift amount within one pixel.

[0035]

As described above, according to the first to third aspects of the present invention, a light source for emitting a light beam modulated based on image data, and a light beam emitted from the light source are deflected. In an optical scanning device that deflects by means and writes image data by scanning on a surface to be scanned of a photoconductor, when a light beam deflected by the deflecting means enters a specific position on the path of the light beam, A signal serving as a reference signal for determining a writing position of image data in the main scanning direction on the surface to be scanned of the photoconductor is detected by a writing position detection unit, and detected by the phase shift amount setting unit by the writing position detection unit. The phase shift amount of the signal is set, and the detected signal is shifted by the phase shift control means in accordance with the phase shift amount set by the phase shift amount setting means. , The phase shift amount is arbitrarily set, so that a reference signal for determining a writing start position (scanning start position) when writing image data in the main scanning direction of the photosensitive drum is set. A write position detection sensor that outputs a detection signal of a certain light beam can be disposed at an arbitrary position outside the image area of the photosensitive drum, and a color printer or the like performs color shift correction within one image clock. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a control circuit in an optical scanning device according to the present invention.

FIG. 2 is a timing chart showing the operation of the control circuit shown in FIG.

FIG. 3 is a circuit diagram showing a specific configuration of a main part in the control circuit shown in FIG. 1;

FIG. 4 is a timing chart for explaining an operation of a main part of the control circuit shown in FIG. 3;

FIG. 5 is a block diagram showing another configuration example of the phase shift control circuit in FIG. 3;

6 is a timing chart showing operation timings of the circuit shown in FIG.

7 is a timing chart showing a relationship between an input voltage and a phase shift amount of the phase shift control circuit in FIG.

FIG. 8 is a configuration diagram showing a configuration of a conventional optical scanning device.

FIG. 9 is a block diagram showing a configuration of a control circuit in the conventional optical scanning device shown in FIG.

10 is a timing chart showing the operation of the control circuit shown in FIG.

[Explanation of symbols]

 34 Writing position detection sensor 102 Image clock generator 104 Synchronization control circuit 114 Image data output timing control circuit 200 Control circuit 202 Phase shift amount setting circuit 204 D / A conversion unit 206 Phase shift control circuit

Claims (3)

[Claims] 1. A light source for emitting a light beam modulated based on image data, and a light beam emitted from the light source is deflected by a deflecting unit and scanned on a surface to be scanned of a photoreceptor. When the light beam deflected by the deflecting means enters a specific position on the path of the light beam, the writing position of the image data in the main scanning direction on the surface to be scanned of the photoreceptor is set. A write start position detecting means for outputting a detection signal serving as a reference signal for determination; a phase shift amount setting means for setting a phase shift amount of a detection signal of the write start position detecting means; and a phase shift amount setting means. Phase shift control means for shifting the phase of the detection signal in accordance with the phase shift amount, and an output tie of the output signal of the phase shift control means. An optical scanning apparatus characterized by having an image data output timing control means for controlling the output timing of the image data so as to output the image data on the basis of the ring. 2. The phase shift amount set by the phase shift amount setting means is determined based on a positional relationship between an arrangement position of the writing position detection means and a writing position of image data on the photoconductor. The optical scanning device according to claim 1, wherein: 3. The apparatus according to claim 2, wherein the phase shift amount set by the phase shift amount setting means is further determined so as to be finely adjusted within one image clock. Optical scanning device.