JPH0687112B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention has a mechanism for reading a document, such as an analog copying machine, a digital copying machine, and a facsimile machine, and processes the read document information to form an image. The present invention relates to an image forming apparatus for forming an image. In particular, the present invention relates to an image forming apparatus having an enlargement and / or reduction function capable of changing a document image to a desired magnification.

<Prior Art> An analog copying machine will be described as an example. In a conventional copying machine, a document is pre-illuminated and scanned, the intensity of reflected light reflected by the document at that time is detected by a photo sensor, and the output of the photo sensor is output. It is known that the document density is automatically detected based on the above-mentioned method (for example, Japanese Patent Laid-Open No. 60-1172).
64, JP-A-61-63864).

FIG. 8 and FIG. 9 are a perspective view and a plan view in which the optical path of the exposure light of the conventional copying machine having the above-described structure is developed. Light emitted from a light source (not shown) is reflected by the original 2, condensed by the condenser lens 5, and given to the photoconductor 3. The light receiving sensor 1 such as a photo sensor is arranged outside the optical path 4 of the light given from the original 2 to the photoconductor 3,
The light to be given to the photoconductor 3 is not blocked. The light receiving sensor 1 is attached to a lens unit (not shown) so as to detect the light reflected at the substantially central portion of the document 2.

<Problems to be Solved by the Invention> By the way, in the case where the copying machine has an enlarging function or an enlarging and reducing function, the condenser lens 5 has an optical path 4 on the upstream side (original 2 side) or the downstream side (photoreceptor 3). Side). The condensing lens 5 is located at the position shown by the solid line in FIG. 9 at the time of copying at the same size, at the upstream side 5'as shown by the chain double-dashed line at the time of enlarging copying, and downstream from it at the time of reducing copying. Moved to side 5 ".

On the other hand, the light receiving sensor 1 is attached to the lens unit as described above, and its position is fixed regardless of the movement of the condenser lens 5.

However, in the case where the light receiving sensor 1 and the condenser lens 5 have the above-mentioned arrangement relationship and the condenser lens 5 moves in the optical path 4, the following problems occur. That is, when the condenser lens 5 moves to the upstream side 5'for enlargement copying, a part of the incident optical path 6 to the light receiving sensor 1 may be blocked (in the case of FIG. 9, hatching is added. Part of the light is blocked.).

When the document density is detected under such a condition, the amount of light detected by the light receiving sensor 1 is reduced by the amount of the incident light that is partially blocked, and the document 2 is erroneously determined to be relatively dark.

In order to solve the above problems, the light receiving sensor 1
However, if this is the case, it becomes difficult to adjust the amount of light received by the light receiving sensor 1, and the size of a lens unit (not shown) for mounting the light receiving sensor 1 must be increased. Further, when the light receiving sensor 1 is moved to the upstream side, a new problem is encountered that the movement of the reflecting mirror (not shown) forming the optical path 4 may be hindered by the light receiving sensor 1.

Further, in order to solve the above problem, it is conceivable that the light receiving sensor 1 can be moved together with the condenser lens 5, but since the light receiving sensor 1 is connected to the electric wiring, the light receiving sensor 1 Making the number 1 movable introduces another problem in the safety standard of the device.

The present invention has been made in view of the circumstances as described above, and even if the condenser lens 5 blocks a part of the incident light to the light receiving sensor 1 at the time of detecting the original density, an accurate original can be obtained regardless of the situation. An object of the present invention is to provide an image forming apparatus capable of detecting density.

<Means for Solving the Problems> The present invention relates to an optical path for guiding light from a document to a light receiving body, and a condenser lens capable of moving in the light path to an upstream side (original side) or a downstream side (light receiving side). An image forming apparatus capable of changing the original image formed on the light receiving body to a desired magnification by moving the condenser lens to a predetermined position in the optical path, and receiving light from the original. A light-receiving sensor for detecting the document density, and the light-receiving sensor is a part of the light to be received by the light-receiving sensor by the light-collecting lens, depending on the position where the light-collecting lens stops near the light-collecting lens. Is arranged at a position where it may be blocked, and further, storage means in which the relationship between the stop position of the condenser lens and the output correction value of the light-receiving sensor is stored in advance, and the storage unit according to the stop position of the condenser lens. Output correction from storage means An image forming apparatus comprising: a correction unit that reads out a value and corrects the output of the light receiving sensor.

<Operation> When a part of the light to be received by the light receiving sensor is blocked by the condenser lens, the correcting means reads the output correction value from the storage means and corrects the output of the light receiving sensor. Therefore, even if a part of the light to be received by the light receiving sensor is blocked by the condenser lens, the output of the light receiving sensor is corrected and the correct document density can be detected.

<Embodiment> FIG. 2 is a sectional view showing a schematic configuration of a copying machine 10 according to an embodiment of the present invention. A transparent contact glass 12 for setting a document 11 is provided on the upper surface of the copying machine 10, and a document cover 13 that can be opened and closed is provided thereon.

An exposure device 14 for reading a document is provided above the inside of the copying machine 10.
Is provided, and a mechanism for detecting the original density is incorporated in the exposure device 14.

The exposure device 14 includes a lamp unit 15 having a lamp 15L for illuminating the original 11 arranged on the contact glass 12. The lamp unit 15 is movable from a left end stop position shown by a solid line to a right end scanning end position shown by a two-dot chain line, and by moving the lamp unit 15, the document 11 is illuminated and scanned.

The lamp unit 15 is provided with a first mirror 16 for guiding the reflected light reflected by the original 11 in a predetermined direction.
The light reflected by the first mirror 16 is reflected by the second mirror 17 and the third mirror.
It is further reflected by the mirror 18. Second mirror 17 and third
The mirror 18 is attached to a common mirror frame 19, and is linked to the movement of the lamp unit 15 so as to follow the lamp unit 15 at a speed of about ½ of the moving intensity of the lamp unit 15. ing. This is to keep the optical path length from the document 11 to the condenser lens 21 constant. Therefore, when the lamp unit 15 reaches the scanning end position at the right end, which is shown by the chain double-dashed line in the figure, the mirror frame 19 moves to almost the center as shown by the chain double-dashed line.

The light reflected by the third mirror 18 is given to the fourth mirror 22 through the condenser lens 21 inserted in the optical path 20, and is reflected by the fourth mirror 22 so as to be applied to the photosensitive drum 23. Has become.

The copying machine 10 has an enlarging and reducing function, and the condenser lens 21 moves in the optical path 20 to the upstream side or the downstream side during the enlargement copy or the reduction copy.

Further, a light receiving sensor (not shown in FIG. 2) for detecting the document density is provided outside the optical path 20 on the side opposite to the condenser lens 21. This will be described later.

Around the photoconductor drum 23, along the rotation direction of the photoconductor drum 23, in order, a charger 24 for charging the drum surface to a constant potential, an erase lamp 25 for removing unnecessary charge, and an exposure. Developing device 26 for developing the electrostatic latent image formed by the above into a toner image, transfer / separation charger 27, cleaner 28 for removing the residual toner on the drum surface, and discharge lamp 29 for removing the residual charge.
Equipment necessary for the work is arranged.

Further, in order to feed the paper in accordance with the movement of each image forming device centering on the photoconductor drum 23, the paper feed cassette 30, the paper feed roller 32 for taking out the paper 31 in the paper feed cassette 30 one by one, There is provided a pair of registration rollers 33 for sending the paper to the photosensitive drum 23 (so-called secondary paper feeding) at the timing. In addition, in order to detect the presence or absence of paper on the registration roller pair 33, a registration switch is
44 are provided.

The toner image formed on the surface of the photoconductor drum 23 is transferred to a sheet of secondary paper that is fed by the action of the transfer / separation charger 27, and the sheet on which the toner image is transferred is the photoconductor drum 23.
It is peeled from the surface and sent to the fixing device 34. Then, the sheet on which the toner image is fixed by the fixing device 34 is discharged to the discharge tray 35.

FIG. 3 is a developed plan view of the optical path 20 of the exposure device 14 in the copying machine 10. As shown in FIG. 3, a condenser lens 21 is arranged in the optical path 20, and the light reflected by the original 11 is condensed by the condenser lens 21 and imaged on the photosensitive drum 23. .

When enlarging and copying, as shown by the chain double-dashed line, the condenser lens 21
Is moved to the original 11 side (upstream side) in the optical path 20 and stopped at a predetermined position. Conversely, during reduction copying, it is moved to the photosensitive drum 23 side (downstream side) and stopped at a predetermined position. For this movement, the condenser lens 21 is connected to the wire 38 hung on the two pulleys 37, and the wire 38 is connected to the lens motor.
It is designed to be moved by 36. Lens motor
36 is a step motor in this embodiment.

Further, in order to detect that the condenser lens 21 moved in this way has reached a predetermined reference position, specifically, a 1 × position represented by a solid line, a lens position detection switch 39
Is provided. The lens position detection switch 39 is made of, for example, a photoelectric switch including a light projecting element and a light receiving element, and whether or not the shielding plate 40 provided in the condenser lens 21 blocks light from the light projecting element to the light receiving element. It is possible to detect whether or not the condenser lens 21 has reached the reference position by the switching timing, and when the step motor 36 rotates by a certain number of steps from the reference position, the condenser lens 21 is desired to move to the upstream side or the downstream side. The amount can be moved.

Further, similarly to the conventional apparatus, a light receiving sensor 41 for detecting the original density is arranged outside the optical path 20 so as not to block the exposure light. The light receiving sensor 41 includes a photo sensor such as a photodiode that converts incident light into an electric signal,
The incident angle of light is regulated by a tubular member so that only the light reflected at the substantially central portion of the document 11 can be detected.

In the copying machine 10 according to this embodiment, the document alignment is based on the so-called center reference, and therefore the light receiving sensor is used.
Reference numeral 41 is designed to detect the light reflected at the substantially central portion of the document 11, but when the document alignment is a so-called one-sided reference, the light receiving sensor 41 is reflected by a fixed area on the reference end side of the document 11. It is only necessary to be able to detect the emitted light.

FIG. 4 is a diagram schematically showing the relationship between the tip position of the condenser lens 21 and the rate at which the incident light on the light receiving sensor 41 is blocked. When the condenser lens 21 moves to the upstream side in the optical path and the tip thereof reaches the position E1 beyond the position EQ, the light a1 of the light incident on the light receiving sensor 41 is blocked. Also, the condenser lens 21
At the position E2, the tip of the
a2 is blocked. Similarly, the light a3 is blocked at the position E3 and the light a4 is blocked at the position E4.

The relationship between the position of the tip of the condenser lens 21 and the rate at which part of the light incident on the light receiving sensor 41 is blocked is unique to the device. Therefore, in this embodiment, this relationship is measured and stored in advance, and the output of the light receiving sensor 41 is corrected by signal processing according to the stop position of the condenser lens 21.
This is the feature of this embodiment.

FIG. 5 is a block diagram showing a configuration of an electric control circuit in the copying machine 10. The control circuit mainly includes the CPU 42, and signals from the operation unit 43, the registration switch 44, and the lens position detection switch 39 are given to the CPU 42. Further, the output of the light receiving sensor 41 is converted into a digital signal by the analog / digital converter 48 and given to the CPU 42. The operation unit 43 is provided, for example, on the front side of the upper surface of the copying machine 10, and includes a print switch (not shown), an automatic exposure switch for switching whether or not to automatically detect the document density, an enlargement copy instruction switch, and a reduction copy instruction. Includes switches and magnification designation keys.

A memory 50 is connected to the CPU 42. The memory 50 stores the output correction value of the light receiving sensor 41 measured in advance. This output correction value is the condensing lens 21 described in FIG.
Based on the relationship between the tip position of and the ratio of the blocked light, for each tip stop position EQ, E1, E2, E3 and E4 of the condenser lens 21, the correction value 0 to be added to the output of the light receiving sensor 41, A1, A2, A3
And A4 are calculated and stored.

In this embodiment, the stop position of the condenser lens 21 is divided into four stages, and the output correction value at each stage is stored in the memory 50. The output correction value for each stage may be stored in the memory 50.

The drive control signal, the rotation direction control signal, and the reference clock output from the CPU 42 are given to the motor controller 45, and the motor controller 45 controls the rotation timing, rotation time, rotation direction, and the like of the optical motor 46. The optical motor 46 is for driving the lamp unit 15, the mirror frame 19, and the like that form the exposure device 14.

The CPU 42 also controls the driving of the lens motor 36 via the driver 47. Condensing lens 21 by lens motor 36
Is moved to a predetermined position. Further, the CPU 42 controls the lamp control circuit 49 to increase or decrease the voltage applied to the exposure lamp 15L to adjust the illuminance.

FIG. 1 is a flowchart showing the operation of the control circuit described above.

Next, along with the flow of FIG. 1, the operation of the copying machine 10 will be described with reference to FIGS.

When the CPU 42 determines that the print switch of the operation unit 43 is turned on (step S1), the condensing lens 21 is moved to the operation unit 43.
It is moved to the position corresponding to the copy magnification specified in (step S2).

In this embodiment, the configuration in which the condenser lens 21 is moved to the designated magnification position after the print switch is turned on in this way is adopted, but when the copy magnification is input from the operation unit 43, it is immediately collected. The optical lens 21 may be moved to the designated magnification position.

Next, the CPU 42 determines the state of the automatic exposure switch (not shown) of the operation unit 43 (step S3). When the automatic exposure switch is on, the document 11 is pre-illuminated and scanned, and the document density is detected based on the amount of light received by the light receiving sensor 41 at that time (step S4).

Then, the CPU 42 determines whether the copy magnification is a magnification that requires correction (step S5). If the tip of the condenser lens 21 is stopped at the position E1, E2, E3, or E4 on the upstream side of the position EQ as described with reference to FIG.
The CPU 42 reads the correction value for the lens position stored in the memory 50, and corrects the document density by adding the read correction value to the output of the light receiving sensor 41 (step S
7).

If the position of the condenser lens 21 is a magnification that does not require correction, the output of the light receiving sensor 41 is directly determined as the document density (step S6).

Then, the obtained document density is stored in the work area of the memory 50 or the like, and during the image processing of step S9 described later, the lamp control circuit 49 is controlled to adjust the illuminance of the lamp 15L so that the copy density is optimized. That is why. In this embodiment, the density is adjusted by adjusting the illuminance of the lamp 15L, but instead, the voltage of the charging charge 24 or the developing bias voltage of the developing device 26 is adjusted to optimize the copy density. May be adjusted to
Alternatively, the copy density may be adjusted by controlling any two or more of the lamp 15L, the charger 24, and the developing device 26, which are involved in the copy density, in combination.

If the automatic exposure switch is off in step S3, the above-mentioned control operations are skipped.

Next, the CPU 42 starts the paper feeding by the paper feeding roller 32 (step S8), rotates the optical motor 46 in the forward direction based on the turning on of the registration switch 44, adjusts the lamp voltage as described above, and the original 11 Image processing including illumination scanning is performed (step S9). Eventually, the trailing edge of the paper (in other words, the trailing edge of the document 11) supplied by the registration switch 44 being turned off is detected (step S10), and the optical motor 4
Reverse 6 to return the lamp unit 15 to the stop position (step S11).

Then, the control of steps S8 to S12 is repeated until the set number of copies is completed, and when it is determined that the set number of copies is completed, more specifically, the exposure operation for the final copy is performed. When it is finished or when it is determined that the last copy sheet has been discharged to the discharge tray 35 (step S12), the control operation is ended.

FIG. 6 is a flowchart showing another control operation by the control circuit of FIG. The control circuit shown in FIG. 5 may perform the control operation shown in FIG. 6 instead of the control operation shown in FIG.

Describing along the flow of FIG. 6, the CPU 42 has an operation unit 43.
When it is determined that the print switch is turned on (step S21), the condenser lens 21 is moved to a position corresponding to the copy magnification specified by the operation unit 43 (step S22).

Next, the CPU 42 determines the state of the automatic exposure switch (not shown) of the operation unit 43 (step S23). When the automatic exposure switch is on, it is determined whether or not the copy magnification is a magnification that needs correction (step S24). If the tip of the condenser lens 21 is at the position E1, E2, E3 or E4 as described in FIG.
The illuminance of the lamp 15L is corrected by (step S25).

More specifically, at a magnification that requires correction, part of the light incident on the light receiving sensor 41 is blocked (see FIG. 4), so the amount of light received by the light receiving sensor 41 decreases. Therefore, in order to compensate for the decrease, the voltage applied to the lamp 15L is corrected so that the illuminance of the lamp 15L is increased. The relationship between the applied voltage and the copy magnification is as shown in FIG. 7, for example, and this relationship is stored in the memory 50 in advance. When the voltage applied to the lamp 15L is increased by the correction, the original 11 is pre-illuminated and the light receiving sensor is operated at that time.
The document density is detected based on the amount of light received at 41 (step S26).

After that, similarly to the control of FIG. 1, the paper feed roller 32 starts the paper feed (step S27), and the registration switch 44
When the optical motor 46 is turned on, the optical motor 46 is normally rotated,
The voltage applied to the lamp 15L is adjusted based on the document density detected in 6 to perform image processing (step S28). The lamp voltage in this case is usually a lower voltage than the lamp voltage corrected in step S25. Because the corrected lamp voltage in step S25 is
Even when a part of the light given to the light receiving sensor 41 is blocked by 1, the lamp voltage is strengthened so that the lamp 15L is brightened so that it does not affect the amount of light detected by the light receiving sensor. This is because in the image processing in step S28, the lamp voltage is adjusted to keep the original density appropriate, and it does not matter that a part of the light is blocked.

Eventually, the registration switch 44 is turned off, so that the CPU 2 detects the trailing edge of the paper (step 29), reverses the optical motor 46, and returns the lamp unit 15 to the stop position (step S30). Then, the control of steps S27 to S31 is repeated until the copy of the set number of sheets is completed, and when it is determined that the copy of the set number of sheets is completed (step
S31), the control operation ends.

Although the above description has been made by taking the copying machine as an example, the present invention can be widely applied to the following apparatuses. In other words, it has an optical path that guides the light from the document to a light receiving body (not only the above-mentioned photosensitive drum but also a light receiving element such as a CCD), and is capable of moving the light in the optical path to the upstream side or the downstream side. The present invention can be applied to a device provided with a lens and including a document reading mechanism, such as the above-mentioned copying machine, as well as a digital copying machine and a facsimile.

<Effects of the Invention> Since the present invention is configured as described above, it is possible to obtain an apparatus that can always automatically and accurately detect a document density. In particular, in the case where the applied device can read an original at a desired scaling factor, accurate document density detection can be performed regardless of the scaling factor at the time of reading an original.

[Brief description of drawings]

FIG. 1 is a flowchart showing the control operation of the copying machine 10 to which the embodiment of the present invention is applied. FIG. 2 is a sectional view showing a schematic configuration of a copying machine 10 to which an embodiment of the present invention is applied. FIG. 3 is a plan view in which the optical path of the exposure light in the copying machine 10 is expanded and drawn. FIG. 4 is a diagram showing the relationship between the tip position of the condenser lens and the rate at which the light incident on the light receiving sensor is blocked. FIG. 5 is a block diagram showing the control circuit of the copying machine 10. FIG. 6 is a flow chart showing another operation of the control circuit of FIG. FIG. 7 is a diagram showing the relationship between the copy magnification and the voltage applied to the lamp 15L. FIG. 8 and FIG. 9 are a perspective view and a plan view of an exposure apparatus in a conventional copying machine, which is developed along an optical path. In the figure, 10 ... Copier, 11 ... Original, 12 ... Contact glass, 14 ... Exposure device, 20 ... Optical path, 21 ... Condensing lens, 23 ... Photosensitive drum, 36 ... Lens motor , 39
...... Lens position detection switch, 41 …… Receiving sensor, 42…
… Indicates a CPU.

Claims (1)

[Claims] Claim: What is claimed is: 1. An optical path for guiding light from a document to a light receiving body, and a condenser lens movable in the optical path to an upstream side (original side) or a downstream side (light receiving side). In an image forming apparatus capable of changing an original image formed on the light receiving body to a desired magnification by moving it to a predetermined position in an optical path, a light source for receiving the light from the original to detect the original density. A light receiving sensor is provided, and the light receiving sensor is located in the vicinity of the condenser lens at a position where a part of light to be received by the light receiving sensor may be blocked by the condenser lens depending on the position where the condenser lens stops. And a storage unit that stores the relationship between the stop position of the condenser lens and the output correction value of the light receiving sensor in advance, and the output correction value is read from the storage unit according to the stop position of the condenser lens. The light receiving sensor An image forming apparatus comprising a correction means for correcting the output.