JP3387623B2 - Image forming 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 adjusting mechanism of an optical system of an image forming apparatus, and more particularly, to adjusting and correcting an optical path length of a variable power optical system using a fixed focus lens during zooming. is there.

[0002]

2. Description of the Related Art Conventionally, a variable power optical system using a fixed focus lens has been used in an image forming apparatus such as a copying machine. The reflected light from the document illuminated by the light source is imaged on the photoconductor through the imaging lens and the plurality of reflection mirrors, and an electrostatic latent image is generated there.

A variable power optical system of a copying machine using a fixed focus imaging lens is approximately represented by the following equation.

[0004]

[Equation 1] Here, f: focal length of imaging lens, m: magnification, a: distance from original document to imaging lens, b: distance from imaging lens to photoconductor, TC: distance from original document to photoconductor. .

The copier is provided with a drive mechanism for changing the position of the imaging lens and an optical path length adjusting device for adjusting the position of the optical system in order to achieve the above expression at an arbitrary magnification. ing.

The fixed focus lens (imaging lens) is
Due to a manufacturing error, the focal length varies by about 1 to 2%, so that defocus may occur even at the reference magnification (generally equal magnification). For this reason, it is general to perform focus adjustment by a focus adjustment mechanism.

[0007]

However, in the above-mentioned conventional example, there is a problem that it is difficult to adjust even the out-of-focus state during zooming.

Generally, the focal length of the imaging lens in a copying machine is about f = 200 mm. At this time, equal size (m
= 1) optical path length TC and expansion (m = 1.41)
The difference in optical path length TC at time is ΔTC = 23.8 mm
Is. The conventional optical path length adjusting device uses a cam mechanism, and when expanded (m = 1.41), ΔTC = 23.8 m
The eccentric cam is designed so that m.

However, if the manufacturing error of the lens is 2%, then f = 204 mm and the enlargement (m = 1.
41), the difference in optical path length required is ΔTC = 24.
3 mm, and with an eccentric cam, the displacement amount = 0.5 mm (2
A focus shift of 4.3 mm to 23.8 mm will occur. By the way, this displacement (def) = Δf (m +
It can be expressed as 1 / m-2).

As a method of solving such a situation, Japanese Patent Laid-Open No. 04-348334 and Japanese Patent Laid-Open No. 61-17213 are available.
Various techniques are disclosed in Japanese Patent Publication No. 4 and U.S. Pat. No. 4,077,715.

In the technique disclosed in Japanese Patent Laid-Open No. 04-348334, the displacement amount is corrected by a central processing unit (CPU).
Moreover, although it is performed electrically using a memory, there is a problem that the cost becomes very high.

Further, in the technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 61-172134, the amount of displacement is changed by changing the amount of movement of the optical path length correction device by deforming the guide member composed of a plurality of members into an arbitrary shape. It is to make a correction. This method has a problem that the number of parts increases and the configuration itself becomes complicated.

The technique disclosed in US Pat. No. 4,077,715 is shown in FIG. In the figure, a cam shaft 103 of an eccentric cam 102 is rotated by a drive motor 101, a cam follower 104 is provided as a follower of this eccentric cam 102, and the displacement of the cam follower 104 is coupled to an optical path length adjusting mechanism 105. . In this way, the optical path length adjusting mechanism 105 can be moved in the direction of arrow A by a predetermined amount according to an arbitrary magnification.

Further, in this patent, the initial angle of the eccentric cam 102 and the cam follower 104 is slightly shifted from the design value by the screw 106 as shown by the arrow B in the figure, and the optical path length adjusting mechanism 105 is adjusted. The amount of movement is corrected.

This is shown in FIG. Design value Δ
The initial angle of the eccentric cam 102 is adjusted in the direction C so as to reduce the displacement amount (def) between the difference between TC and the actual difference between ΔTC of the apparatus.

The broken line in the figure shows the change of the design value ΔTC, the solid line shows the change of ΔTC of the actual machine when deviated by Δf, the horizontal axis shows the magnification, and the vertical axis shows the ΔTC.

However, although it is possible to perform correction in the same magnification and enlargement or in the same magnification and reduction, it is difficult to perform a series of corrections in enlargement-equal magnification-reduction. This is the displacement amount (def) = Δf (m
If it can be expressed as + 1 / m-2), Δ (delta) expansion and Δ (delta) reduction always have the same sign.
The correction method shown in FIG. 8 can only perform correction in which Δ expansion and Δ reduction have different signs. This is shown in FIG.

As shown in FIG. 10, at the time of enlargement, the design value ΔTC is corrected in the direction C approaching the change of the actual machine ΔTC, but at the time of reduction, the design value ΔTC is corrected in the direction C1 and the displacement. The amount (def) becomes large and defocus magnification occurs.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide an image forming apparatus equipped with an optical system capable of reducing the focus shift even at an arbitrary magnification.

Another object of the present invention is to provide an image forming apparatus which is inexpensive and which can change the magnification of an optical image with a simple structure.

Still another object of the present invention is to provide an image provided with an improved optical path length adjusting mechanism capable of accurately adjusting and correcting the optical path length during zooming of a zooming optical system using a fixed focus lens. To provide a forming apparatus.

[0022]

In order to solve the above-mentioned problems of the prior art, the present invention provides an optical system for forming an image of reflected light from an optical scanning object, and the optical system according to the magnification of the image. In an image forming apparatus that has an optical path length adjusting unit that adjusts the optical path length of the reflected light by changing the position of the system, and the optical path length adjusting unit is an image forming apparatus that forms an image based on the formed image. includes a driving member, a driven member which is displaced in response to rotation of said driving member, and a correction mechanism for changing the relative distance between the driven member and the rotation axis of said driving member, before
The driving member has a similar cross-sectional shape perpendicular to its axis,
Is formed so that the similarity ratio changes continuously in the direction,
The correction mechanism moves the driven member in the axial direction of the driving member.
It is movable, and the driven member is connected to the optical system.

Alternatively, the reflected light from the optical scanning target is combined.
An optical system for forming an image and the optical system according to the magnification of the image.
The optical path length of the reflected light can be adjusted by changing the position of
An optical path length adjusting means for adjusting the optical path length, and based on the formed image.
In the image forming apparatus for forming an image, the optical path length
The adjusting means is a prime mover consisting of an eccentric cam connected to the drive source.
The member and the driving member are displaced according to the rotation, and the magnification is expanded.
A first driven member that is driven by the driving member at a large time;
Second driven member driven by the driving member when the ratio is reduced
A driven member having a rotary shaft of the driving member and the driven member.
A correction mechanism for changing the relative distance between the moving members,
The correction mechanism is the same as the rotating shaft of the eccentric cam at the same magnification
It is possible to correct the relative distance between the cam receiving portions of the driven member.
And the relative distance between the first driven member and the second driven member.
Separation can be corrected, and the driven member is connected to the optical system.
It is characterized by being.

[0024]

[0025]

[0026]

In a preferred embodiment, the driven member has a rotating member that is rotatably supported, and a first end portion of the rotating member abuts the eccentric cam and faces the first end portion. The second end is connected to the optical system, and the correction mechanism can correct the position of the rotation shaft of the rotation member.

[0028]

According to the present invention, the optical path length adjusting means is provided with the driving member and the driven member and changes the relative distance between the rotation shaft of the driving member and the driven member. It is possible to appropriately correct the optical path length caused by the manufacturing error of the lens and the like, and as a result, it is possible to obtain a high-quality image output.

[0029]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a view showing the schematic arrangement of a copying machine according to this embodiment. In the figure, 1 is a platen glass on which a document to be scanned is placed, 2 is a full-speed mirror stand that moves at a predetermined scanning speed, 3 is a half-speed mirror stand that moves at half the scanning speed, and 4 is a Fixed-focus imaging lens, 5 optical path length adjusting mirror base, 6 folding mirror, 7 photoconductor, 8
Is an optical path length adjusting device.

The full-speed mirror base 3 has a lamp 11 for illuminating an original, a reflector 12 for irradiating the original from the lamp 11, a slit 13, and a full-speed mirror 14.
And are installed. When scanning the original, the original is illuminated and the reflected light is transmitted through the slit 13 to the full-speed mirror 1.
4 is supplied to the half-speed mirror stand 3. Two half-speed mirror bases 15 are attached to the half-speed mirror base 3, and the reflected light is reflected by these mirrors 15 and supplied to the imaging lens 4.

The position of the imaging lens 4 is changed by a driving system (not shown) according to various magnifications. 4a is
The position when m times (m> 1) is shown, and 4b shows the position when 1 / m times. The light from the imaging lens 4 is imaged on the photoconductor 7 via the optical path length adjusting mirror 16 and the folding mirror 6 attached to the optical path length adjusting mirror base 5, and a latent image is formed here.

Incidentally, the optical path of the reflected light shown by the solid line in the figure shows the one at the same magnification, and the electrostatic process around the optical system and the photosensitive member 7 ahead of the illumination system is not shown. Since it is similar to a conventional copying machine, it will not be described in detail here.

The optical path length adjusting device 8 moves the position of the optical path length adjusting mirror base 5 according to various magnifications to adjust the optical path length.
And correction. In order to correct the optical path length when m times or 1 / m times, the optical path length adjusting device 8
The optical path length adjusting mirror base 5a is moved to the position shown by the broken line.

Here, the amount of movement of the optical path length adjusting mirror base 5 is the optical path length difference Δ with respect to the focal length f of the imaging lens 4.
It can be shown that TC = f (m + 1 / m-2). In the present embodiment, the imaging lens is moved to a predetermined position and the optical path length is adjusted and corrected by the optical path length adjusting device 8 in response to the user setting the arbitrary magnification m.

FIG. 2 shows a detailed structure of the optical path length adjusting device. The optical path length adjusting device 8 includes an eccentric cam 20 as a driving node.
And a cam follower 24 as a follower. An elongated slide groove 23 extending in the lateral direction is formed substantially on the center line of the eccentric cam 20. The rotary shaft of the drive system 21 is inserted into the slide groove 23, and the rotary shaft and the eccentric cam 20 are fixed by a set screw 22. The eccentric cam 20 is configured to be movable laterally in the slide groove 23 by loosening the retaining screw 22, and the rotation center can be set at an arbitrary position in the slide groove 23.

The cam follower 24 abuts on the cam surface of the eccentric cam 20 on the rotation axis of the eccentric cam 20, and the eccentric cam 2
It is displaced laterally in response to 0 rotation. Cam follower 2
A slide groove 27 is formed at the other end portion of 4 as shown in the figure, and is fixed to the connecting member 25 by a fastening screw 26 via the slide groove 27. The relative positional relationship between the cam follower 24 and the connecting member 25 can be adjusted in the direction of the slide groove 27 by loosening the fastening screw 26.
Further, the guide pin 25a projects from the connecting member 25,
The guide pin 25a is also arranged in the slide groove 27, and the slide groove 27 and the slide groove 23 are arranged so as to be substantially parallel to each other at the time of initial setting.

A spring 28 is connected to the connecting member 25, and the other end of the spring 28 is connected to a fixed portion of the device. Therefore, the connecting member 25 is biased in the direction of the arrow D, that is, the tip portion d of the cam follower 24 is brought into contact with the cam surface a of the eccentric cam 20. Also,
The end of the connecting member 5 is connected to the optical path length adjusting mirror base 5 described above, and transmits the displacement of the eccentric cam 20 to the optical path length adjusting mirror base 5 via the cam follower 24.

Here, as shown in the figure, the eccentric cam 20 and the cam follower 24 are in contact with each other at the portions a and d. The eccentric cam 20 has a center of "o" and polar coordinates (r
The shape is _(m) , θ _(m) ). When P is an arbitrary point on the cam surface, ∠aop = θ. Also, r = op
Is. At this time, ΔTC = (op-oa) is the change amount of the optical path length from the document to the photoconductor when m times. Since the optical path length adjusting mirror base 5 is a C-shaped folding mirror frame, the change in the optical path length is doubled.

Now, the design value is r (m = 1) = oa.

When the arbitrary magnification M (<1), the eccentric cam 2
0 rotates by θ = ∠aob by the drive system 21. At this time, ΔTC _M = (ob-oa) _yz = f (M + 1 / M
-2).

When the magnification is arbitrary 1 / M, the eccentric cam 20
Is rotated by θ = ∠aoc by the drive system 21. At this time, ΔTC _{1 / M} = (oc-oa) _xz = f (M + 1 / M
-2).

Here, it is assumed that the focal length f of the imaging lens 4 deviates from the design value by Δf (Δf> 0). At this time, ΔTC is ΔTC _M = ΔTC _{1 / M} = (f + Δ
f) (M + 1 / M-2), and the displacement amount (def) =
(F + Δf) (M + 1 / M-2) -f (M + 1 / M-
2) = Δf (M + 1 / M−2), and the amount of focus shift is caused by this amount. Therefore, the relative distance between the rotation shaft of the eccentric cam 20 and the cam follower 24 is set by
Loosen and adjust 2 to set the position of the rotary shaft from 0 to 01. At this time, ΔTC _M = (o ₁ b ₁ −o ₁ a) _xz ≈
(F + Δf) (M + 1 / M-2), ΔTC _{1 / M} = (o ₁
c ₁ −o ₁ a) _xz≈ (f + Δf) (M + 1 / M-2).

That is, [(o ₁ b ₁ −o ₁ a) − (ob
-Oa)] _xz ≈ Δf (M + 1 / M-2).
The change in ΔTC at this time is shown in FIG. The solid line in the figure is
The actual ΔTC change of the copying machine when deviated by Δf is shown, and the broken line shows the ΔTC change of the design value. The ΔTC of the actual machine can be corrected in the E direction, and the deviation amount can be reduced.

However, the rotation axis of the eccentric cam 20 is changed from o to o ₁
When you shift to, cam follower 24 by the amount of oo ₁
Need to be moved away from the cam. In this case, the fastening screw 26 is loosened to shift along the slide groove 27, and the cam follower 24 is fixed again by the fastening screw 26.

Next, FIG. 4 shows a structural example of an optical path length adjusting device according to the second embodiment of the present invention.

In the present embodiment, the eccentric cam 30 has a substantially trapezoidal swivel shape so that the cam surface in a cross section taken along a plane perpendicular to the axis O has a similar shape. The cam follower 31 is set on the cam follower base 32. On the cam follower base 32, an upright screw rod 33 and a parallel pin 34 parallel to this are provided.
The screw rod 33 and the parallel pin 34 are inserted into the corresponding holes of the cam follower 31. At this time, the spring 35 is inserted on the screw rod 33 between the cam follower 31 and the follower base 32, and the screw 36 attached on the screw rod 33 on the cam follower 31 is rotated, so that the cam follower 31 moves. The height is adjustable. The parallel pin 34 guides the cam follower 31 which moves up and down.

A slide groove 27 is formed at the end of the cam follower base 32 as in the above embodiment, and the cam follower base 32 can be shifted in the direction of the arrow D by a fastening screw 26. Also, the connecting member 2
The reference numeral 5 is connected to the optical path length adjusting mirror base 5, and the spring 28 presses the cam follower 31 against the cam surface.

By moving the cam follower 31 in the vertical direction, the relative distance from the eccentric cam 30 can be corrected. That is, when the focal length is shorter than the design value of the imaging lens 4, the cam follower 31 is moved upward, and when the focal length is longer than the design value, the cam follower 31 is moved downward. As a result, the movement amount of the cam follower 31, that is, the movement amount of the optical path length adjusting mirror base 5 can be corrected.

Further, the correction of the focus at the same magnification is performed by, for example,
L when the contact d of the cam follower 31 moves from a to e on the cam surface (moves the cam follower 31 upward)
Because it is displaced, loosen the fastening screw 26, move the cam follower base 32 to the cam side by l, and again screw 26
Fixed by.

As another example of this embodiment, a mechanism for moving the eccentric cam 30 in the vertical direction may be provided while the cam follower 31 is moved in the vertical direction.

The shape of the eccentric cam may be as shown in FIG. That is, in the cylindrical coordinate system, (h (Δ
f), r (m, Δf), θ (m)), r = r ₀ + ΔT
The shape of the eccentric cam 39 is such that C = r ₀ + (f + Δf) (m + 1 / m-2).

Next, the construction of the optical path length adjusting device according to the third embodiment of the present invention is shown in FIG.

In this embodiment, the cam follower, which is a driven member of the eccentric cam 40, has first and second cam followers 41 and 42, both of which are extended from the cam follower 43 and are parallel pins 44 and screw rods. It has a hole through which 45 passes. On the screw rod 45 between the cam followers 41 and 42,
A spring 46 is inserted, and screws 47 and 48 are attached to both ends of the screw rod 45 to regulate the positioning of the cam followers 41 and 42.

The spring 46 has a very strong elasticity and fixes the cam followers 41 and 42. However, when the spring strength of the spring 46 cannot be sufficiently obtained, screws 47 and 47 are used instead of the spring 46. Screws may be arranged so as to face 48 and be sandwiched. The cam followers 41 and 42 contact the eccentric cam 40 at the time of reduction and expansion, respectively, and at least one contacts the eccentric cam 40 at the time of equal magnification. The state of the figure shows the contact of the cam follower at the same magnification.

By configuring as in this embodiment, the distance of oa (or oa ₁ ) at the time of reference (equal magnification) is changed, and separate cam followers are prepared at the time of expansion and reduction, The deviation amount can be corrected separately.

Next, the construction of the optical path length adjusting device according to the fourth embodiment of the present invention is shown in FIG. As described above, according to Δf of the imaging lens, TC = f (m + 1 / m + 2),
The variation ΔTC = f (m + 1 / m-2) from the same size is ΔTC
= (F + Δf) (m + 1 / m-2). For this reason,
It can be seen that it is sufficient to satisfy ΔTC = k (m + 1 / m-2) with respect to the design value. However, k = (f + Δf) / f.

The optical path length adjusting device of this embodiment is provided with the eccentric cam 5
0 and a cam follower portion 51 driven by this eccentric cam. The tip of the cam follower portion 51 abuts on the cam surface of the eccentric cam 50, and an elongated groove 52 is formed in the center thereof. A support member 53 for axially supporting the cam follower portion 51 is inserted into the elongated groove 52, and the cam follower portion 51 is inserted at an arbitrary position in the groove.
It is configured to be able to pivot. Further, the other end of the cam follower portion 51 is rotatably coupled to a coupling portion 54 coupled to the optical path length adjusting mirror base 5 via a rotation boss 55. In this way, according to the rotation of the eccentric cam 50, the cam follower portion 51 rotates about the support member 53 as an axis.

In the design value, the support member 53 is located at the center line of the eccentric cam 50 and the center of the rotary boss 55, and the connecting member 54 is provided in the same amount in the direction opposite to the moving direction of the cam contact portion of the cam follower portion 51. Be moved. It is for this reason that the direction of the cam is opposite to that of the first to third embodiments described above.

Assuming that the focal length of the imaging lens 4 is displaced by Δf> 0 from the design value and becomes f + Δf, the support member 53 is located at a position of (f + Δf) / f = b / a = k. Is moved to 53a, the required ΔT as described above
C is obtained. As described above, in this embodiment, the optical path length can be corrected by changing the relative distance between the support member 53 that supports the cam follower portion and the axis of the eccentric cam 50.

As described above, in the variable power optical system having the fixed focus lens, the optical path length (TC) at the time of variable power caused by the manufacturing error of the focal length of the lens can be corrected. It is possible to reduce the focus shift and obtain high-precision image quality.

Further, since the optical path length correction can be realized with an inexpensive and simple structure without using expensive hardware such as an electronic circuit, it is possible to provide a small-sized and low-priced copying machine.

[0063]

As described in detail above, according to the present invention, it is possible to appropriately correct the optical path length caused by the manufacturing error of the lens used in the optical system even at an arbitrary magnification, and as a result, It is possible to obtain high-quality output.

Further, since the optical path length adjusting means is achieved by a simple mechanical structure using a cam mechanism, it is possible to reduce cost and size. Therefore, the image forming apparatus itself can be reduced in cost and size.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a copying machine according to an embodiment of the present invention.

FIG. 2 is a plan view showing the configuration of the optical path length adjusting device according to the first embodiment of the present invention.

FIG. 3 shows a magnification and an optical path length difference (ΔT) according to the first embodiment.
It is a figure which shows the relationship with C).

FIG. 4 is a diagram showing a configuration of an optical path length adjusting device according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing an example of another eccentric cam in the second embodiment.

FIG. 6 is a plan view showing the configuration of an optical path length adjusting device according to a third embodiment of the present invention.

FIG. 7 is a plan view showing the configuration of an optical path length adjusting device according to a fourth embodiment of the present invention.

FIG. 8 is a side view showing a configuration of an optical path length adjusting device in a conventional copying machine.

FIG. 9 is a diagram showing a relationship between a magnification and an optical path length difference in a conventional optical path length adjusting device.

FIG. 10 is a diagram showing a relationship between a magnification and an optical path length difference in a conventional optical path length adjusting device.

[Explanation of symbols]

1 Platen glass 4 Imaging lens 5 Optical path length adjustment mirror stand 7 photoconductor 8 Optical path length adjustment device 20, 30, 39, 40, 50 Eccentric cam 24, 31, 41, 42 Cam followers 23, 27 slide groove 22,26 retaining screw 28 springs

Continuation of front page (56) Reference JP 62-106447 (JP, A) JP 61-80140 (JP, A) JP 52-151217 (JP, A) JP 2-210374 (JP , A) JP-A-63-179346 (JP, A) JP-A-59-125720 (JP, A) Actually open flat 2-10535 (JP, U) Actually open 62-69235 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03B 27/34-27/40 F16H 51/00-55/30 F16H 19/00-37/16 F16H 49/00

Claims (2)

(57) [Claims] 1. An optical system for forming an image of reflected light from an optical scanning target and an optical path for adjusting the optical path length of the reflected light by changing the position of the optical system according to the magnification of the image. In an image forming apparatus that has a length adjusting unit and forms an image based on the formed image, the optical path length adjusting unit includes a driving member, and a driven member that is displaced according to rotation of the driving member. And a correction mechanism for changing the relative distance between the rotation shaft of the driving member and the driven member, wherein the driving member has a similar cross-sectional shape perpendicular to its axis,
The correction mechanism is formed so that the similarity ratio changes continuously in the axial direction, the correction mechanism is capable of moving the driven member in the axial direction of the driving member, and the driven member is connected to the optical system. An image forming apparatus characterized by the above. 2. An optical system for forming an image of reflected light from an optical scanning target and an optical path for adjusting the optical path length of the reflected light by changing the position of the optical system according to the magnification of the image. In an image forming apparatus having a length adjusting means for forming an image based on the formed image, the optical path length adjusting means includes a driving member formed of an eccentric cam connected to a driving source, and a driving member of the driving member. A driven member having a first driven member that is displaced according to rotation and that is driven by the driving member when the magnification is increased, and a second driven member that is driven by the driving member when the magnification is reduced; A correction mechanism for changing the relative distance between the rotary shaft of the member and the driven member, wherein the correction mechanism corrects the relative distance between the rotary shaft of the eccentric cam and the cam receiving portion of the driven member at the same magnification. Possible and first driven member The relative distance between the second driven member is possible correction, the image forming apparatus, characterized in that the driven member is connected to the optical system.