JP3134566B2 - Image output device - 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 output device.
The image output device includes a color image output device such as a laser printer or a color copier, and a characteristic detection device of an optical deflector.

[0002]

2. Description of the Related Art Generally, in an image output apparatus such as a light beam scanning type printer or a digital copying machine, there is a problem of a scan jitter which degrades the quality of an output image, that is, a deviation of a start or end position of an optical scanning line. In particular, in a full-color copying machine or the like, the required accuracy of a writing position of a pixel, which is a constituent unit of an image, is very severe compared to a monochrome printer or the like.
Scan jitter must be made as small as possible.

It is considered that the occurrence of scan jitter is particularly greatly affected by variations in the shape of each reflecting surface of the rotating polyhedron. The scan jitter caused by the variation in the shape of the reflection surface appears repeatedly at the same cycle as the rotation of the rotary polygon mirror due to its nature. Therefore, if the timing of the repetition pattern and the start of the pattern (where the start point of the pattern is arbitrary) is known, scan jitter can be reduced by performing an appropriate correction process at an image signal output unit or the like. Can be. Normally, it is not necessary to perform this measurement frequently because the repetitive pattern of scan jitter does not change rapidly. However, knowing the start timing of the repetitive pattern requires at least one continuous printing operation (image writing operation). The times need to be done.

The following technique (J0) is known as a method for detecting a repetition pattern start timing known up to now.
1) and (J02) are known. (J01) A method in which marking is applied to portions other than the reflecting surface of the rotating polygon mirror and this is detected by a light emitting element and an optical sensor. (J02) A part of the reflecting surface of the rotating polygon mirror is processed to determine the inclination angle of the mirror surface. Partially change and deflect part of the incident light beam in a special direction,
A method of detecting by placing an optical sensor at the position irradiated by the deflection light,

[0005]

The repetitive pattern start timing detection methods (J01) and (J02) have the following problems. Problem of (J01) In this method, it is necessary to install a mark detecting sensor near the rotary polygon mirror, and the shape and material of the mirror cover for reducing the windage resistance of the rotary polygon mirror are restricted. (J02) Problem In this method, although it is a part of the rotary polygon mirror, the shape is processed, so that the effect of deformation due to centrifugal force increases, and the design of the rotary polygon mirror and the optical scanning device is restricted. become.
In addition, the cost increases due to special processing.

Further, in the case of introducing this into an optical scanning device which does not perform correction focusing on the scan jitter repetition pattern, the optical sensor is installed in the casing of the optical scanning device in the above-mentioned methods (J01) and (J02). It is often the case that it is not possible to respond due to structural restrictions of the casing, etc., because additional processing for inserting is necessary, and it is an issue to detect the start timing of the repetitive pattern without modifying the casing of the optical scanning device. I was

[0007] In view of the above circumstances, the present invention is directed to the following contents (O01) and (O02). (O01) In an image output apparatus in which optical scanning for writing an image on a latent image forming surface always starts from a specific reflecting surface of a rotary polygon mirror, the optical deflector and the casing of the optical scanning device are not modified. In addition, it is necessary to detect a deflection position of a specific reflecting surface. (O02) An image output device such as a color copying machine is capable of positioning a writing position of a pixel which is a constituent unit of an image with high accuracy.

[0008]

Next, the configuration of the present invention devised to solve the above-described problem will be described. The components of the present invention correspond to the components of the embodiments described later. For the sake of simplicity, the reference numerals of the components of the embodiment are enclosed in parentheses. The reason why the present invention is described in correspondence with the reference numerals of the following embodiments is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

In order to solve the above problems, an image output apparatus according to the present invention comprises a scanner motor (3) having magnetic detecting elements (11a, 11b, 11c) for detecting the position of a rotating field pole, and the scanner motor (3). ), An optical deflector constituted by a rotating polygon mirror (K) having a plurality of reflecting surfaces (K1 to K8) mounted on the rotor, and a light beam deflected by each reflecting surface of the rotating polygon mirror (K) The latent image forming surface (5a) on which optical scanning for image writing is performed by (L)
And a specific reflection surface detection unit for detecting a light deflection position of a specific reflection surface of the rotating polygon mirror (K) and outputting a specific reflection surface detection signal.
In left and means, an image output device image optical scanning for writing is always to begin from a particular reflective surface of the rotary polygonal mirror (K) of the latent image forming surface to (5a), the following requirements ( (Y01) the magnetic detection element (11a, 11b, 11c).
Outputs the specific reflection surface detection signal according to the change of the output signal
The specific reflection surface detecting means (8).

(Explanation of Terms) The "image output device" according to the present invention includes a monochrome image output device, a multi-color image output device, a full-color image output device, a characteristic detection device of an optical deflector, and the like. Further, the “reflection surface” refers to a flat surface or a curved surface processed so as to reflect an incident light beam (L) such as a laser beam. The "rotating polygon mirror" means at least two reflecting surfaces (K1 to K8) by directly forming a reflecting surface (K1 to K8) on a surface portion thereof or fixing a member having the reflecting surface (K1 to K8). K1 to K8)
This is the name of a part that is attached to the rotating member of the motor or that is rotated by being integrated with the rotating member of the motor and performs light deflection. Any material can be used for the rotating polygon mirror (K) as long as it does not break or change its shape when it is rotated at a predetermined rotation speed.
For example, there are aluminum, iron, resin and the like. The "specific reflection surface"
Is the reflecting surface (K1 to K8) of the rotary polygon mirror (K)
Among them, the reflection surface (K1 to K8) which particularly starts the writing scan by the actual light beam (L) is particularly indicated. The "magnetic detection element" refers to an element having a magnetic detection surface and capable of outputting the direction of a magnetic field on the surface by a difference in electrical state, and an example of which is a Hall element utilizing the Hall effect. .

(Embodiment 1 of the present invention) An embodiment 1 of an image output apparatus of the present invention is a scanner motor (3) having magnetic detecting elements (11a, 11b, 11c) for detecting the position of a rotating field pole, and a scanner motor (3). Multiple reflecting surfaces (K1 to K8) mounted on the rotor of the scanner motor (3)
Image deflector constituted by a rotating polygonal mirror (K) having an optical system, and latent image formation in which optical scanning for image writing is performed by a light beam (L) deflected by each reflecting surface of the rotating polygonal mirror (K) (5a), and a yellow image, a magenta image, and a cyan image are sequentially written on the latent image forming surface (5a) to form a color image. (Y011) A specific reflection surface detection means (8) for outputting a specific reflection surface detection signal in response to a change in an output signal of the magnetic detection element (11a, 11b, 11c). (Y012) Optical scanning for writing each color image on the latent image forming surface (5a) always starts from a specific reflecting surface (K1 to K8) defined for each color of the rotary polygon mirror (K). Hands to do
Dan.

(Second Embodiment of the Present Invention) The second embodiment of the image output apparatus of the present invention is the same as the first embodiment.
In the image output device of (1), the following requirements (Y013) to (Y0
(Y013) the magnetic detection element (11a, 11b, 11c)
When the output signal reaches the specified state, the reference
Means for outputting a reference reflection surface detection signal.
Optical scanning device to obtain the starting position of the optical scanning line after
Out of the SOS sensor provided in or near the
Counting means for counting the number n of force outputs.
Reflecting surface detecting means, when it reaches the number of times no set by the (Y014) the output times n, the start of optical scanning by the rotary polygon mirror predetermined reflection surface from said specific reflective surface no + 1 th of (K) (Y015) the yellow and black colors on the latent image forming surface (5a).
Zenta, the optical scanning values of the no at the start of optical scanning for image writing of the respective colors of cyan, which is set for each color
Means to start.

(Third Embodiment of the Present Invention) The third embodiment of the image output apparatus of the present invention is the same as the first embodiment.
Or the following requirements for the image output device of (2) (Y016)
(Y016) when the rotor is at a predetermined reference rotation position
The magnetic detection elements (11a, 11a,
11b, 11c) a reference position memory for storing the output state
And the output state stored in the reference position storage means.
And the actual state of the magnetic sensing elements (11a, 11b, 11c)
Comparing means for comparing with the output state of the
If the output status matches the actual output status,
A reference reflection surface detection signal output means for outputting a projection surface detection signal.
Said specific reflection surface detecting means (8).

(Fourth Embodiment of the Present Invention) The fourth embodiment of the image output apparatus of the present invention is the same as the third embodiment.
In the image output device of (1), the following requirements (Y017), (Y0
(Y017) wherein the magnetic detection element (11a, 11b, 11c)
A combination pattern of three output signals;
The magnetic sensing element (11a, 11b, 11c)
The reference position storage means for storing an output state, (Y018) the said rotating field poles is two scanner motor (3).

[0015]

[0016]

[0017]

[0018]

Next, the operation of the present invention having the above-mentioned features will be described. (Operation of the Present Invention) The image output device of the present invention having the above-described features has an optical deflector. A plurality of reflecting surfaces (K1 to K1) of this optical deflector
The rotating polygon mirror (K) having (8) is rotationally driven by a scanner motor (3) having magnetic detecting elements (11a, 11b, 11c) for detecting the position of the rotating field pole. Optical scanning for image writing is performed on the latent image forming surface (5a) by the light beam (L) deflected on each of the reflecting surfaces (K1 to K8) of the rotary polygon mirror (K). Optical scanning for writing an image on the latent image forming surface (5a) is always started from a specific reflecting surface of the rotary polygon mirror (K). The specific reflection surface is detected by a specific reflection surface detection unit (8) that outputs a specific reflection surface detection signal according to a change in an output signal of the magnetic detection element (11a, 11b, 11c). That is, the present invention
Ming's image output device is originally installed on the scanner motor (3).
The rotating field pole and the magnetic sensing element (11a,
11b, 11c), a new optical deflector
Each of the reflecting surfaces can be provided without providing a simple rotational position detecting member.
Can be detected.

(Operation of Embodiment 1 of the Present Invention) Embodiment 1 of the image output apparatus of the present invention having the above-mentioned features.
Has an optical deflector. The rotary polygon mirror (K) having a plurality of reflection surfaces (K1 to K8) of this optical deflector is provided with magnetic detecting elements (11a, 11b, 11) for detecting the position of the rotating field pole.
It is rotationally driven by a scanner motor (3) having c). The light beam (L) deflected on each of the reflection surfaces (K1 to K8) of the rotary polygon mirror (K) causes the latent image forming surface (5).
In (a), optical scanning for writing an image is performed. The light scanning is performed for each color of yellow, magenta, and cyan.
The scanning order for each color can be arbitrarily determined. Also,
It is also possible to perform optical scanning for writing a black image to be developed with black toner. Optical scanning for writing each color image on the latent image forming surface (5a) always starts from a specific reflecting surface defined for each color of the rotating polygon mirror (K).
The specific reflective surface is used for the optical polarizer to detect a new rotational position.
Originally installed on the scanner motor (3) without any components
The magnetic sensing elements (11a, 11b, 11
c) Generates a specific reflection surface detection signal in accordance with the output signal change.
It is detected by the specific reflection surface detecting means (8).

(Operation of the Second Embodiment of the Present Invention) In the image output device of the second embodiment of the present invention, after the reference reflection surface detection signal is output, the counting means obtains the start position of the optical scanning line. The number of times n of the output of the SOS sensor provided in or near the optical scanning device casing is counted. Then, the output number n is equal to the set number no.
Is reached, the optical scanning is started by the (n + 1) th predetermined reflection surface (specific reflection surface) from the reference reflection surface of the rotary polygon mirror (K). As the value of no, an appropriate value is set for each color of Y (yellow), M (magenta), and C (cyan), and the latent image forming surface (5a) is set according to the set number of times no. ) Starts the optical scanning for writing the image of each of the colors Y, M, and C. The number of times no
Is adjusted for each color image output device, color unevenness on the output image can be reduced. In other words, the scan jitter repetition pattern when each color is output as an image is checked before moving on to the printing operation, and the combination of each pattern that minimizes pixels is selected. SOS
The value of the output counting number no can be set. Then, the image writing operation can be started thereafter.

(Operation of the Third Embodiment of the Present Invention) In the third embodiment of the image output apparatus of the present invention, the reference position storage means (16) of the specific reflection surface detecting means (8) includes:
The output state of the magnetic detection elements (11a, 11b, 11c) of the scanner motor (3) when the rotor is at the reference rotation position is stored. The comparison means (12) compares the output state stored in the reference position storage means (16) with the actual output state of the magnetic detection elements (11a, 11b, 11c), and if they match, A coincidence signal (reference reflection surface detection signal) is output. The time when the coincidence signal (reference reflection surface detection signal) is output is when the reference reflection surface comes to a predetermined position. The specific reflection surface detection signal is output according to an output of a coincidence signal output when the reference reflection surface reaches a predetermined position.

(Operation of the Fourth Embodiment of the Present Invention) In the fourth embodiment of the image output apparatus of the present invention, the number of rotating field poles of the scanner motor (3) is two, and the magnetic detecting elements (11a, 11b, 11c) are used. ) Are provided. The reference position storage means (16) stores a combination pattern of output signals of three magnetic detection elements (11a, 11b, 11c) as output states of the magnetic detection elements (11a, 11b, 11c). You. One output signal is O
In the case of binary values of N and OFF, the combination patterns are six patterns. Any of the six patterns can be stored. The number of patterns to be stored may be one, but may be plural. For example, if all six patterns are stored, 360 °
It becomes possible to detect the position of the rotating polygonal mirror (K) every time it rotates by ÷ 6 = 60 °.

[0023]

[0024]

[0025]

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical deflector of the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments. The image output device of this embodiment is a device for detecting the characteristics of an optical deflector, and associates the vertical ruled lines dots of an output image with the reflecting surfaces (K1 to K8) of the rotating polygon mirror (K) to thereby enable the rotation of the rotating polygon mirror. This is for estimating the deformation amount of each part. FIG. 1 is a diagram showing a configuration of an embodiment according to the present invention. The optical scanning device 4 includes a light beam source 1 that emits a light beam L, a scanner motor 3 equipped with a rotating polygon mirror K, an optical lens system through which the light beam L passes or reflects, an SOS sensor 6, and a device for fixing these components. It is composed of an optical casing and the like. As shown in FIG. 2, the scanner motor 3 has a rotor magnet 3a and a stator 3b. The photosensitive drum 5 is a hollow cylinder that rotates at a constant speed in the sub-scanning direction, and forms a latent image on a latent image forming surface (photosensitive film) 5 a formed on the outer surface by scanning light from the optical scanning device 4. Is done.

The motor driver 7 controls the commutation of the stator currents Ix, Iy, Iz (not shown) by output signals from the magnetic detecting elements 11a, 11b, 11c (see FIG. 2) inside the scanner motor 3. The constant speed rotation control of the scanner motor 3 is performed.

Next, the magnetic detecting elements 11a, 11b, 11 for detecting the position of the rotating field pole of the scanner motor 3 of the optical deflector.
A description will be given of the fact that a predetermined reflection surface of the rotary polygon mirror K can be detected from the change in the output of c, and that the optical scanning can be started from the predetermined reflection surface. 2A and 2B are explanatory diagrams of a scanner motor 3 for rotating the rotary polygon mirror K. FIG. 2A is a diagram showing the relationship between the rotary polygon mirror K and the scanner motor 3, and FIG. 2B is three magnetic detecting elements inside the scanner motor 3. 11a, 11b,
It is a schematic diagram of 11c arrangement. FIG. 3 shows the magnetic sensing element 1
It is a timing chart of the output of 1a, 11b, 11c. The three magnetic sensing elements 11a, 11b, 11c are shown in FIG.
As shown at B, the stator 3b is disposed 120 degrees apart from the stator 3b disposed around the rotor magnet 3a inside the motor. Individual magnetic sensing elements 11a, 11b, 1
1c outputs a positive or negative output according to the polarity of the closest part of the rotor magnet 3a. Here, ignoring the magnitudes of the outputs of the three magnetic sensing elements 11a, 11b, 11c and focusing only on their polarities, as shown in FIG. 3, at least one of the rotor magnets 3a rotates by 60 degrees.
It can be seen that the polarity of the two magnetic detecting elements 11a, 11b, 11c is inverted, and six types of output patterns are output during one rotation of the rotor magnet 3a.

Therefore, for example, in FIG.
If the output of 1b is positive and the output of 11c is negative (range x in FIG. 3), the output of this pattern always occurs when the magnetic pole of the rotor magnet 3a comes within a range of ± 30 degrees from the direction of FIG. 2B. Will be. Then, when the rotor further rotates and the magnetic pole of the rotor magnet 3a faces a specific direction, the output pattern changes to the next pattern (point P in FIG. 3). Here, since the rotor magnet 3a and the rotary polygon mirror K are both mounted on the same rotating shaft, the reflecting surface that performs light deflection at this time is the same reflecting surface every time and faces the same direction each time. However, at this time, the direction of reflection of the light beam L by the reflection surface differs depending on how the rotating polygon mirror K is attached to the motor, which output pattern changes are to be observed, and the like.

If the magnetic sensing elements (11a, 11b,
11c) When the light beam L is incident on the SOS sensor at the moment when the output pattern changes, and an SOS signal is generated,
There is a possibility that the counting operation of the SOS signal becomes unstable and a counting error occurs. SO to avoid this
By delaying the S signal and adjusting the amount of delay, the output of the magnetic detection element and the SOS signal do not overlap, and a stable operation can be realized.

As will be described later, in this embodiment, a change in the output pattern of the magnetic detection elements (11a, 11b, 11c) is used as a trigger to start counting, and the number n of occurrences is counted from the next SOS sensor output. When the count reaches a preset number no, image writing (printing or drawing) is started from the output of the next SOS sensor. The change in the output pattern of the magnetic sensing elements (11a, 11b, 11c) is used as a trigger for starting the printing operation, and the next S
Image writing (printing or drawing) can be started from the output of the OS sensor (sensor corresponding to no = 1).

The specific reflection surface detecting means 8 shown in FIG. 1 generates a specific reflection surface detection signal from the output signals from the magnetic detecting elements 11a, 11b and 11c and the SOS signal generated by the SOS sensor, and a print control unit. 9 is output. The print control unit 9 enters a signal waiting state when a print command from the main control unit 10 is received, and starts sending dot data for instructing the laser driver 11 on the light amount of the light beam L when detecting the specific reflection surface detection signal. I do. The laser driver 11 increases or decreases the drive current of the light beam source 1 according to the dot data, changes the light amount of the light beam L, and writes a latent image on the photosensitive drum 5.

Next, the specific reflection surface detecting means 8 will be described. FIG. 4 is a functional block diagram showing the specific reflection surface detecting means 8. In FIG. 4, the outputs of the magnetic detecting elements 11a, 11b, 11c are input to a pattern comparing means 12. The reference position storage means 16 stores the magnetic detecting elements 11a and 11a when the rotating polygon mirror K reaches a specific position.
Output patterns of 11b and 11c are stored. The pattern comparing means 12 includes the magnetic detecting elements 11a, 11b, 1
It has a function of comparing the output of 1c with the pattern stored in the reference position storage means 16 and outputting a reset pulse (reference reflection surface detection pulse) to the down counter 13 when they match.

The surface number storage means 17 stores the surface number of the reflection surface to be detected, and presets this value each time the down counter 13 is reset. The surface number is 0 for the reflection surface that is performing optical deflection at the moment when the pattern comparison means 12 outputs the reset pulse (reference reflection surface detection pulse), and 1, 2, 3,... The numbers of the reflecting surfaces Ki (i = 1, 2, 3,...) Given in order. The delay means 15 sends the SOS signal to the clock input of the down counter 13 after delaying the SOS signal by an arbitrary time. This delay time depends on the SOS signal and the pattern comparing means 12.
A value is set so that the reset signal from is not sent to the down counter 13 at the same time.

The down counter 13 decrements the count value by one each time the clock signal from the delay means 15 is input, and repeats this until the count value becomes zero. When the count value becomes zero, the down counter 13 outputs the specific reflection surface detection signal to the outside via the buffer 14, and waits until the next reset pulse comes.

Generally, in a laser printer, a digital copying machine, or the like using an optical scanning device, it is known that there is a shift in the start or end position of the optical scanning line, that is, the presence of scan jitter. This scan jitter degrades the output image quality, and in particular, in full-color copying and the like, its influence is great, so it must be reduced as much as possible. Causes of this scan jitter include vibration of optical components in the optical scanning device,
There are fluctuations in the output timing of print data, fluctuations in the optical scanning speed that occur in the process of deflecting the light beam L, and the like. In particular, reduction of the fluctuations in the optical scanning speed is most important.

The fluctuation of the light scanning speed is caused by the fluctuation of the rotation speed of the rotary polygon mirror K for performing the light deflection and the variation of the shape of the reflecting surface. In particular, the latter is said to have extremely large effects such as centrifugal force caused by rotation and thermal expansion of members, in addition to variations resulting from the processing accuracy of parts. However, it is very difficult to check the state of the reflecting surface during high-speed rotation, and the effect of the centrifugal force and thermal expansion cannot be known by direct observation. Therefore, in the present embodiment, the following method is adopted instead of the method of directly measuring the shape. That is, an optical deflector having a rotating polygon mirror K to be measured as shown in FIG. 5A is mounted on a laser printer, and a large number of vertical ruled lines are printed out as shown in FIG. 5B. A large number of dots are arranged in the vertical scanning line in the sub-scanning direction. By measuring the positional deviation of the dots, the speed fluctuation in the main scanning direction can be estimated.

At this time, it is necessary that the dots of the output image and the reflecting surface on which optical scanning was performed at that time completely correspond to each other. From this and the shape measurement result of the rotating polygon mirror K in the stationary state, the amount of deformation of the reflecting surface due to rotation can be estimated. There are several methods for associating the dots with the reflecting surfaces, but one of the reflecting surfaces of the rotating polygon mirror K is defined as a reference surface (that is, a predetermined reflecting surface), and light scanning is always performed on this reference surface. The easiest way is to take measures by starting printing from.

FIG. 5 shows, as an example, a comparison with an output image when a rotating polygon mirror K having eight reflecting surfaces on the side faces rotates clockwise. Assuming that the reference surface is the first surface, the dots of the vertical ruled line formed by optical scanning on the first surface are the first, ninth, seventeenth,... Dots. Similarly, the dots of the vertical ruled line formed by the optical scanning by the second surface can be second, tenth, eighteenth,. At this time, the speed fluctuation in the main scanning direction can be estimated from the deviation of each dot from the reference position in the horizontal direction.

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG. FIG. 6 shows a processing flow (specific reflection surface detection flow) when the functions of the elements 12 to 17 of the specific reflection surface detection means 8 of FIG. 4 are realized using a microcomputer. In FIG. 6, when the specific reflection surface detection flow of the specific reflection surface detection means 8 is started, in step S1, the magnetic detection elements 11a, 11b, 1
The output signal 1c is taken into the pattern comparing means 12. Next, in step S2, the signal pattern (the pattern of the output signals of the magnetic detection elements 11a, 11b, 11c) stored in the reference position storage means 16 is taken into the pattern comparison means 12.

Next, in step S3, the pattern of the output signal of the magnetic sensing elements 11a, 11b, 11c is compared with the signal pattern stored in the reference position storage means 16, and whether the two patterns match. It is determined whether or not. If they do not match, the process returns to step S1. If they match, the process proceeds to step S4, where the down counter 13
Reset. Next, in step S5, the contents of the surface number storage means 17 are set in the down counter 13. Next, the process proceeds to step S6. In step S6, SOS
The signal output is taken in from the signal input unit.

Next, in step S7, it is determined whether an SOS signal has been generated. If no, the process returns to step S6. If yes, go to step S8. In step S8, the down counter is decremented. Next, in step S9, it is determined whether the count value = 0. If no (NO), the process proceeds to step S6. If yes, the process moves to step S10. In step S10, a specific reflection surface detection signal is output.
Then, the processing of the specific reflection surface detection flow ends.

(Effect peculiar to the embodiment) In this embodiment, it is not necessary to add a new sensor to the optical scanning device or change the shape of the rotary polygon mirror K as in the conventional case. Even in an optical scanning device that cannot be used, the amount of deformation of each part of the rotary polygon mirror K can be estimated.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. A modified embodiment of the present invention is illustrated in the following (H01). (H01) The present invention is also applicable to image output devices other than the optical deflector characteristic detection device, for example, image output devices such as laser beam printers and digital copiers. In particular, when applied to a color image output device, it is possible to obtain a high-quality image with little color shift.

[0045]

The image output device of the present invention has the following (E01)
To (E04). (E01) Since there is no need to install a mark detection sensor near the rotating polygon mirror to detect the start timing of the scan jitter repetitive pattern, a mirror cover is designed to reduce the windage resistance of the rotating polygon mirror. No restrictions are imposed on the shape and material. (E02) Since unnecessary shape processing is not performed on the rotary polygon mirror, deformation of the reflecting surface shape due to centrifugal force can be suppressed as much as possible. (E03) There is no need for special processing, so there is no increase in cost. (E04) When trying to introduce this into an optical scanning device that has not performed correction focusing on the scan jitter repetition pattern, no additional processing of the optical scanning device is required, and it is compatible with most optical scanning devices. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of an image output apparatus according to the present invention.

FIG. 2 is an explanatory view of a rotating polygon mirror K and a scanner motor 3 for rotating the same, FIG. 2A is a diagram showing the relationship between the rotating polygon mirror K and the scanner motor 3, and FIG. Three magnetic detecting elements 11a, 1 inside the motor 3
It is a schematic diagram of 1b, 11c arrangement.

FIG. 3 is a magnetic sensing element 11a, 11 according to the embodiment.
It is a timing chart of the output of b, 11c.

FIG. 4 is a functional block diagram showing the specific reflection surface detecting means 8 of FIG. 1;

FIG. 5 is an explanatory diagram showing the relationship between the rotary polygon mirror K of the embodiment and an output image when the mirror rotates clockwise. FIG. 5A shows the rotation of an optical deflector mounted on a laser printer or the like. FIG. 5B is a view showing a polygon mirror K, and FIG. 5B is a view showing a number of vertical ruled lines printed out by the rotary polygon mirror K of FIG. 5A.

FIG. 6 is a diagram showing a processing flow (specific reflection surface detection flow) performed by the microcomputer when the functions of the elements 12 to 17 in FIG. 4 are realized by using the microcomputer.

[Description of Signs] L: light beam 1: light beam source, 2: rotary polygon mirror, 3: scanner motor, 4: optical scanning device, 5, photosensitive drum, 6: SOS sensor, 7: motor driver, 8: Light deflection surface detection means, 9
... Print control unit, 10 ... Laser driver, 11a, 1
1b, 11c: magnetic detecting element, 12: pattern comparing means,
13: Down counter, 14: Buffer, 15: Delay means, 16: Reference position storage means, 17: Surface number storage means,

Claims (1)

(57) [Claims] An optical deflector comprising a scanner motor having a magnetic detecting element for detecting the position of a rotating field pole, a rotary polygon mirror having a plurality of reflecting surfaces mounted on a rotor of the scanner motor, and A latent image forming surface on which optical scanning for image writing is performed by a light beam deflected by each reflecting surface of the polygon mirror, and a light deflection position of a specific reflecting surface of the rotary polygon mirror are detected to detect a specific reflecting surface detection signal. and it outputs a special
An image output apparatus having a constant reflection surface detecting means, wherein the optical scanning for writing an image on the latent image forming surface always starts from a specific reflection surface of the rotary polygon mirror, the following requirement (Y01) is satisfied. (Y01) a feature according to a change in an output signal of the magnetic detection element.
The specific reflection surface detecting means for outputting a constant reflection surface detection signal.