JPH04109264A - Optical system automatic adjusting device for image formation device - Google Patents

Abstract

PURPOSE:To enable even a person who does not have technical knowledge to put an optical system in focus by deciding whether or not the optical system is in focus automatically by the image formation device and adjusting the position of a constituent element of the optical system. CONSTITUTION:An image carrier 4 is exposed to a reference pattern arranged on an original platen 1 by using the optical system to form an image, which is detected by a detecting means 6; and a decision means decides whether the optical system is in focus or not according to the detection output. When it is decided that the optical system is not in focus, a position adjusting signal generating means generates a position adjusting signal and position adjusting means 28 and 29 adjust the position of the constituent element of the optical system. Said processes are repeated until the decision means decide that the optical system is put in focus. Consequently, the optical system can be put in focus automatically.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automatic adjustment device for the optical system of an image forming apparatus such as an electrophotographic or electrostatic recording type copying machine, or a facsimile printer. be.

[Conventional technology]

Conventionally, for example, an electronic system using an analog optical system, in which a document placed on a contact glass, which is a document mounting table, is exposed onto an image carrier using an optical system having a document irradiation lamp to form an electrostatic latent image of the document. A photocopy machine (hereinafter referred to as a copy machine)
When adjusting the focus of the optical system, a test chart for adjustment is placed on the contact glass, a copy of this test chart is made, and the service engineer compares the copy with the test chart to determine the focus of the optical system. The components of the optical system are determined as necessary.
By repeatedly adjusting the position of mirrors, etc.
The focus of the optical system was adjusted.6 In addition, in a document reading device using a digital optical system with COD, for example, a 200-dip test chart is read, the CCD output at this time is displayed on an oscilloscope, and the waveform is viewed. However, the focus was adjusted by adjusting the serviceman lens and scanner position.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, the adjuster determines how far the imaging state of the optical system deviates from the optimal state, and the amount of adjustment depends on empirical factors. Another problem is that the coordinator is limited to those who have specialized knowledge.

The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a device that can automatically focus the optical system of an image forming device. be.

[Means to solve the problem]

In order to achieve the above object, an optical system automatic adjustment device for an image forming apparatus according to the present invention exposes a document on a document table onto an image carrier, and causes the document to be hidden on the image carrier. an optical system for forming an image; and an image detection system for detecting an image formed by exposing a reference pattern placed on the document table onto the image carrier using the optical system. a position adjusting means for adjusting the position of a component of the optical system using a position adjustment signal; and a determining means for determining whether or not the optical system is in focus based on a detection output of the image checking means. and position adjustment signal generation means for generating the position adjustment signal according to the determination result of the determination means, and the position adjustment signal generation means detects when the determination means determines that the optical system is out of focus. The present invention is characterized in that the above-mentioned position adjustment signal is generated when the determination is made.

[Effect]

An image is formed by exposing a reference pattern placed on a document table onto the image carrier using an optical system, which is detected by an image detection means, and based on the detection output. , the determining means determines whether or not the optical system is in focus. When it is determined that the optical system is out of focus, the position adjustment signal generating means generates a position adjustment signal, and the position adjustment means adjusts the positions of the components of the optical system. By repeating the above steps until the determining means determines that the optical system is in focus, the optical system is automatically focused.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 to 5.

FIG. 1 is a schematic diagram of an electrophotographic copying machine (hereinafter referred to as a copying machine) that employs an optical system automatic adjustment device according to an embodiment of the present invention.

First, an overview of the entire copying machine will be explained.

In Fig. 1, contact glass 1, which is a document placement table,
The image of the upper original (not shown) is projected by the optical system 2 onto a drum-shaped photoreceptor 4, which is a latent image carrier, and which has already been uniformly charged by a negative charger 3. An electrostatic latent image is formed on 4.

Here, the optical system 2 includes a lamp 21 which is a light source for illuminating the original.
, first mirror to fourth mirror 22, 23°24.25,
The second scanner unit 27 has components of the optical system such as a lens 26 which is an imaging element, and also includes a second mirror 23 and a third mirror 24, for focusing the optical system 2. It is connected to a transport means (not shown) driven by a stepping motor 28 so that its relative position with respect to the lens 26 can be adjusted. Further, the stepping motor 28 is provided with a drive circuit 29.

The electrostatic latent image formed on the photoreceptor 4 is converted into a toner image by toner from a developing device 5 provided on the right side of the photoreceptor 4 . Here, the developing device N5 uses a two-component developer. This toner image is transferred by a transfer charger (not shown) onto a transfer paper conveyed from a paper feeding section (not shown). The transfer paper on which the toner image has been transferred is separated from the photoreceptor 4, passes through a fixing device (not shown), and is discharged outside the machine as copy paper.

On the other hand, residual toner is removed from the surface of the photoreceptor 4 after the transfer by a cleaning device (not shown) provided on the left side of the photoreceptor 4, and residual charges are removed by a charge-eliminating lamp (not shown). It is prepared for the next charging by 3.

The copying machine of this embodiment detects the focus state and automatically adjusts the relative position of the second scanner unit 27 with respect to the lens 26 for focusing according to the detection result. It has an adjustment mode.

In order to detect the focus state, a reference pattern 11 for irradiation, which is permanently installed at a position away from the original placement place on the contact glass 1 (the place where the original is placed during copying), is placed on the photoreceptor 4 using the optical system 2. is exposed to light to form an electrostatic latent image, this electrostatic latent image is developed by a developing device 5, and the amount of reflected light from this developed image is detected by an optical sensor 6 consisting of a light emitting element and a light receiving element.

As this reference pattern 11, for example, a dot-shaped pattern with a number of lines of 50 to 75 and an area ratio of 20 to 50% is suitable.

Detection of the reflected light by the optical sensor 6 is performed in order to correct the effects of the amount of light emitted by the light emitting element, changes in the sensitivity of the light receiving element over time, or toner adhesion on the optical sensor surface. Detection output Vs of the background part of the photoreceptor 4
a and the detection output VSP of the reference pattern section Vs
Performed using p/V sa.

This is because, as shown in Figure 2, the background part of the photoreceptor and the reference pattern part are affected by the above effects in the same way, so by taking the ratio of these detection outputs, the above effects can be canceled out. It is something.

When the reference pattern 11 in which black dots are formed on a white background is exposed onto the photoreceptor 4 using the optical system 2, a potential distribution as shown in FIG. 3 is formed. In the figure, a shows the potential distribution when the optical system 2 is in focus, and b shows the potential distribution when the optical system 2 is out of focus.

In this way, the maximum potential at the center of the black dot is not affected much by whether or not it is in focus, but the amount of light at the outline around the dot decreases when the dot is out of focus. A potential gradient is generated, and as a result, toner adhesion also occurs in this portion due to development, thereby reducing the amount of reflected light of the developed image of the reference pattern 11. The decrease in the amount of reflected light of the developed image of the reference pattern 11 is
This is so large that the focus of the optical system 2 is shifted, and if the above V80 is the same, the shift of the focus is ■sP.
becomes smaller.

Therefore, the above V sp / V sa is expressed as follows, with the relative position of the second scanner unit 27 to the lens 26 as the horizontal axis.
As shown in Figure 4, where Vgp/Vsa is taken on the vertical axis,
The value is highest at the position where the image is in focus, and the value decreases as you move away from this position.

In the automatic focus adjustment mode of this embodiment, the second scanner unit 27, which is an optical element that changes the focus state of the optical system 2, is moved relative to the lens 26, and the reference pattern is Repeating the formation of the developed image No. 11 and the detection of the amount of reflected light by the optical sensor 6,
Lens 2 of the second scanner unit 27 with good focus
6, and for this purpose, the output of the optical sensor 10 is input to the control section 7, and the control section 7 outputs the output of the stepping motor 2.
A drive signal is output to the drive circuit 29 of 8. Further, a dedicated switch (not shown) is provided for executing the automatic focus adjustment mode.

The automatic focus adjustment mode will be explained below with reference to FIG.

When the dedicated switch is turned on, the first step is to
The stepping motor 28 is driven to move the second scanner unit 27 to an adjustment start position a predetermined distance away from the lens 26. This adjustment start position is determined by the distance from the lens 26 when the optical system 2 is in focus (hereinafter, the position of the second scanner unit 27 at this distance is referred to as the focus position). ) is set to be definitely larger than .

Next, in a second step, a developed image is formed by exposing and developing the reference pattern 11, and an optical sensor measures the amount of reflected light.
Read the detection output in step 6 and set Vsp/Vsa.
is calculated and the result of this calculation is stored in register a.

Next, in a third step, the stepping motor 28 is driven to move the second scanner unit 27 in a direction closer to the lens 26 by Nmm, which is the reference movement unit.

This reference movement unit is set by the conjugate length of the optical system 2, etc., but numerically speaking, it is sufficient if the resolution of the stepping motor 28 is about 0.11.

Next, in the fourth step, a developed image is formed by exposing and developing the reference pattern 11 again, and the detection output of the amount of reflected light is read by the optical sensor 6, and Vsp/Vs
A is calculated and the result of the calculation is stored in register b.

Next, in the fourth step, the contents of both registers are read and compared. As described above, the adjustment start position is set so that the distance to the lens 26 is reliably larger than the distance to the lens 26 when the optical system 2 is in focus, and Since the movement in steps is a movement in the direction of bringing the second scanner unit 27 closer to the lens 26 by Nmm, the position after the movement by Nmm is usually closer to the focus position than the adjustment start position, and therefore, V 5 p/ read from register a
VS. , V s read from register b
p /V 5 G is larger (see Figure 4).

Here, V sp/V s read from register b
.

If O is larger, in the sixth step, V sp/V sa read from register b is stored in register a, and the process proceeds to the third step.

Thereafter, in the third step, the second scanner unit 27 is
While approaching the focus position by 11lIl, in the fourth step, the reference pattern 11 is exposed and developed to form a developed image, and the detection output Vsp/V, 0 is calculated, and the fifth step is performed.
V 5 p/V s before and after Nya movement in the step.

and V sP after Nmm movement in the 6th step.
/ V go is stored in register a by the second scanner unit 27 passing through the focus position.
V read from register b in step 8P/V
Repeat until it is determined that go is not larger.

■sp/ read from register b in the fifth step
If it is determined that V sa is not larger, the second scanner unit 27 is returned by Nmm in a seventh step. This is because the position before the Nmm movement in the third and final step may be considered to be the closest to the focus position, but this fifth step may be omitted. This ends automatic focus adjustment.

Note that the transfer paper is not fed while the above automatic focus adjustment mode is being executed.

As described above, in this embodiment, the reference pattern 11 is permanently installed at a position away from the document placement area on the contact glass (1), so the reference pattern 11 is placed on the document placement table during adjustment. You can save time and effort.

Also, turn on the special key to execute automatic focus adjustment mode.
Detection of the reference pattern 11 and adjustment of the optical system 2 are automatically repeated until the optical system 2 is in focus. However, service personnel can perform other inspections.

Furthermore, by detecting the developed image on the photoreceptor 4, it is determined whether or not the focus is correct, and since the transfer paper is not fed while the automatic focus adjustment mode is being executed, the conventional analog optical system is not used. Unlike copying machines using 2, there is no need for wasting transfer paper for focusing.

In each of the above embodiments, the reference pattern 11 is permanently installed at a position away from the document placement area on the contact glass 1, but instead of this, when executing the bin automatic mode, The reference pattern 11 may be placed on.

Immediately after starting the automatic focus adjustment mode, the second scanner unit 27 is moved to the adjustment start position a predetermined distance away from the lens 26, and a latent image of the first reference pattern is formed. However, instead of this,
The first latent image formation of the reference pattern 11 may be performed while the second scanner unit 27 remains in the position at the start of the automatic focus adjustment mode. In this case, by using the output of the optical sensor 6 before and after the movement of the second scanner unit 27 and the relationship shown in FIG. If it is determined that the object has moved in a direction away from the focus position, the direction of movement is reversed, and then the object is moved in the direction after the reversal.

Furthermore, in the above embodiment, it is determined whether or not the optical system 2 is in focus by comparing the detection values of the optical sensor 6 before and after the movement of the reference movement unit, but instead of this,
The detected value of the optical sensor 6 when the optical system 2 is in focus is determined in advance by experiment, and this detected value is used as the reference value for control, and the detected value of the optical sensor 6 at the time of detection and this standard are used. It may be determined whether the optical system 2 is in focus or not by comparing the values.

Further, in the above embodiment, the developed image of the reference pattern 11 is detected by the optical sensor 6, but instead of this, the electrostatic latent image of the reference pattern 11 may be detected by a potential sensor.
The transferred image of the reference pattern 11 transferred to the transfer paper may be detected by an optical sensor or the like.

Furthermore, in the above embodiment, the focus of the optical system 2 is adjusted by moving the second scanner unit 27, but any component other than this may be used as long as it is a component that can adjust the focus of the optical system 2. You may move it.

[Effects of the Invention] As described above, according to the present invention, the image forming apparatus automatically determines whether or not the optical system is in focus, and
Since the positions of the components of the optical system are adjusted, there is an excellent effect in that even a person without specialized knowledge can focus the optical system.

[Brief explanation of the drawing]

1 to 5 are drawings for explaining one embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a copying machine according to the embodiment, and FIG. 2 is a photoconductor background and a reference pattern. Figure 3 is a characteristic diagram showing the potential on the photoreceptor corresponding to the area containing the two dots of the reference pattern, and Figure 4 is a characteristic diagram showing the optical sensor output of the second scanner unit 27 of the optical system. Detection value of the optical sensor when changing the distance to the lens 26 V s p / V
FIG. 5 is a flowchart of the automatic focus adjustment mode. 2...Optical system, 21...Lamp 22
．． 23, 24, 25...Mirror 26...Lens, 27...Second scanner unit 5...Developing device 5.6...Light sensor, 7...Control unit patent applicant Ricoh Co., Ltd.Figure 1Figure 2Figure 3Figure 4Figure 5

Claims (2)

[Claims] (1) An optical system for exposing a document on a document tray onto an image carrier to form a latent image of the document on the image carrier; and a reference pattern arranged on the document tray. an image detection means for detecting an image formed by exposing the image carrier to light using the optical system; and a position adjustment means for adjusting the position of the component of the optical system using a position adjustment signal. and a determining means for determining whether or not the optical system is in focus based on the detection output of the image detecting means, and a position adjustment signal for generating the position adjustment signal according to the determination result of the determining means. generating means, wherein the position adjustment signal generating means generates the position adjustment signal when the determining means determines that the optical system is out of focus. System automatic adjustment device. (2) Prior to exposing the reference pattern onto the image carrier using the optical system, a means for reliably moving the constituent elements of the optical system to a predetermined position where the optical system becomes out of focus is provided. The position adjusting means positions the components of the optical system so as to move them by a predetermined distance in a fixed direction from the predetermined position, and the discriminating means adjusts the position of the components of the optical system so as to move them by a predetermined distance in a predetermined direction from the predetermined position. 2. The automatic optical system adjustment device for an image forming apparatus according to claim 1, wherein the output of the image detecting means is compared in magnitude.