JPH0518089B2 - - Google Patents

Description

[Detailed description of the invention]

"Technical field" The present invention moves the entire zoom lens provided in the optical path from the document surface to the photoreceptor, and changes the distance between its constituent lens groups, thereby increasing the copying magnification while keeping the distance between the object and image constant. The present invention relates to an optical adjustment method for a variable magnification copying apparatus that changes the magnification. "Prior Art and its Problems" Copying apparatuses capable of variable magnification are required to be capable of copying from enlargement to reduction based on the same size, and to be low-cost. For this reason, zoom lens magnification changers that are easy to assemble and adjust are now being adopted from single lens magnification changers that are complicated to assemble and adjust and are expensive. In terms of optical design, this zoom lens magnification changer is
The basic characteristic is that the distance between objects and images does not change even if the magnification is changed. However, since manufacturing errors are unavoidable in lenses, focal errors, that is, deviations in focus position and errors in magnification, occur. Therefore, as the magnification changes, the object-to-image distance inevitably changes, resulting in uneven focus positions, and this error must be removed by some means. In JP-A-57-189109 and JP-A-58-219514, the object-to-image distance is adjusted to return to the initial design value, but since there is little freedom in adjustment, the magnification range is from 1.0x to Narrow at 0.64x. Also, the zoom lens
In order to facilitate adjustment, three groups of symmetrical lenses are used, which results in a large number of lenses and a complex configuration. Furthermore, since a symmetrical lens is adjusted asymmetrically, aberrations may increase. ``Object of the Invention'' The present invention solves these problems with variable magnification copying devices using a zoom lens, and easily corrects the unevenness of the focus position due to a change in magnification even if there is a manufacturing error in the zoom lens. The object is to obtain an adjustable optical adjustment device. Furthermore, the present invention
To provide a device that can easily adjust the distance between objects and images after aligning the focus positions. Further, the present invention further includes:
Similarly, another object of the present invention is to provide a device that can also adjust errors in magnification due to lens manufacturing errors. "Summary of the Invention" The present invention provides that in a variable magnification copying apparatus using a zoom lens, it is not possible to eliminate the deviation of the focus position due to a change in magnification, that is, the unevenness of the focus position, simply by adjusting the object-to-image distance. Based on this recognition, we have developed a method that can eliminate the uneven focus position. That is, the present invention is based on the knowledge that in a zoom lens consisting of a plurality of lens groups, the focus position at at least two magnifications can be aligned by adjusting the reference setting position of any one of the constituent lens groups. The first step is to adjust the reference setting position of at least one component lens group of the zoom lens to align the focus position at multiple magnifications, and the first step is to adjust the reference setting position of at least one constituent lens group of the zoom lens, and the first step is to move a part of the optical member to adjust the object image. The present invention is characterized by comprising a second step of adjusting the distance between the two and moving the focus position toward the photoreceptor surface. According to such an optical adjustment method, the distance between the constituent lens groups is uniformly shifted from the initial position over the range of magnification, the focus position at multiple magnifications is aligned,
Furthermore, by moving a part of the optical member to adjust the distance between objects and images, the focus position during variable magnification copying can be made constant to the extent that there is no practical problem. "Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. FIG. 3 shows an example of a slit exposure type copying apparatus to which the present invention is applied, in which an original O placed on an original platen glass 1 is illuminated by an illumination lamp unit 2 movably provided on the lower surface of the glass 1. It is irradiated in a slit shape, and the reflected light enters an imaging zoom lens (projection lens) 6 via a first mirror 3, a second mirror 4, and a third mirror 5, which travel together with the lamp 2. The second and third mirrors 4 and 5 move together at half the speed of the first mirror 3. The light exiting the zoom lens 6 is reflected by a reflecting mirror 7 and then projected onto the surface of a photosensitive drum 8 in the form of a slit. The latent image formed on the photosensitive drum 8 is transferred and developed by well-known means to become a copy. To change the copying magnification, the zoom lens 6 may be moved to the position indicated by 6a for enlargement and to the position indicated by 6b for reduction, and the spacing between the constituent lens groups may be changed. If the optical members such as the zoom lens 6 are manufactured according to the optical design, the distance between the document surface and the surface of the photoreceptor drum 8, that is, the object-to-image distance remains constant, and the focus position does not change. FIGS. 1 and 2 show an embodiment of a variable magnification copying apparatus according to a modified invention, which is applied to a variable magnification copying apparatus having the basic structure described above. First, FIG. 1 shows an embodiment of a zoom lens 6 which is a feature of the present invention, and this lens consists of two groups, a front lens group F and a rear lens group R. The front group lens F is fixed to the front group lens frame 11, and the rear group lens R is fixed to the rear group lens frame 12, respectively, by well-known means. These two lens frames 11,
12 is a coaxial hole 14 of the same diameter of a single movable lens barrel 13
The front group lens frame 11 is fixed to the movable lens barrel 13 in the final assembled state, and the rear group lens frame 12 is supported so as to be movable in the axial direction with respect to the movable lens barrel 13. Both are moving lens barrels 13
can be moved axially within the Rear group lens frame 12
has an interlocking pin 15 projecting in the radial direction,
This interlocking pin 15 passes through the play hole 16 of the movable lens barrel,
The lens frame 12 is fitted into the linear guide groove 18 of the slide plate 17 that fixes the movable lens barrel 13 to restrict the rotation of the lens frame 12 and to only allow movement in the optical axis direction.
On the other hand, a radial interlocking plate 20 is fixed to the front part of the front group lens frame 11 and the protruding part from the movable lens barrel 13. An optical axis direction position adjustment screw 21 is supported on the interlocking plate 20 while maintaining axial integrity (allowing only rotation), and the tip of this adjustment screw 21 is screwed into the end surface of the movable lens barrel 13. are combined. 22
is a set screw for fixing the front group lens frame 11 to the movable lens barrel 13. Therefore, according to the zoom lens 6 having the above configuration, when the screwing position of the adjusting screw 21 is adjusted with the set screw 22 loosened, the front group lens frame 11 moves in the optical axis direction via the interlocking plate 20. Therefore, the reference setting position in the optical axis direction can be easily and reliably adjusted. The zoom lens 6 is fixed on a slide plate 17 of a variable magnification copying machine, the entirety of which is shown in FIG. The slide plate 17 is supported by a guide rod 27 on the base plate 26 so as to be able to reciprocate. The guide rod 27 is fixed to both ends of a cam plate 28 fixed on the base plate 26, and guides the front group lens F and the rear group lens R of the zoom lens 6 in the direction of the optical axis F. On the cam plate 28, there are pulleys 2 at both ends.
9 and 29 also have a stepping motor 3 at the upper end.
0 and a wire pulley 32 rotationally driven via its pinion 31 are supported, respectively.
The wire rope 33 wound between the pulley 29 and the wire pulley 32 has one end fixedly tied to the slide plate 17 and the other end elastically tied to the slide plate 17 via a tension spring 34. There is. A cam lever 36 is pivotally mounted on the slide plate 17 by a pin 35. The cam lever 36 is approximately L-shaped, and has a long groove 37 in which the interlocking pin 15 is fitted in one arm 36a on the zoom lens 6 side, and a cam follower 38 in the arm 36b on the cam plate 28 side. ing. The cam follower 38 is biased by a spring means (not shown), such as a torsion spring wound around the pin 35, so as to always come into contact with a cam surface 39 formed on the cam plate 28. Cam surface 3
Reference numeral 9 is a rear lens group R whose shape is set so as to give a desired movement locus by a synthetic movement with the slide plate 17. Note that the slide plate 17 has a cam lever 36.
A light-shielding/slit member 40 is attached to the opposite end to enable position adjustment in the optical axis direction. This light shielding/slit member 40 is connected to the U of the photo interrupter 41 fixed to the base plate 26.
The light passes through the character-shaped portion, and depending on whether or not this light shielding/slit member 40 blocks light from the photo interrupter 41, an enlarged region or a reduced region is detected. The same magnification position is set as the position where the light shielding/slit member 40 starts shielding the photo interrupter 41, that is, the position where the output of the photo interrupter 41 changes significantly. This light-shielding/slit member 40 is attached to the slide plate 17 through a long hole 42 in the optical axis direction, and therefore, the set screw 4
By loosening 3 and adjusting the position, the same magnification position can be shifted. In the variable magnification copying apparatus having the above configuration, when the stepping motor 30 is driven, the slide plate 17 is moved through the wire pulley 32, the pulley 29 and the wire rope 33, that is, the front group lens F and the rear group lens R.
The entire zoom lens 6 consisting of moves in the optical axis F direction, and the cam surface 39 and cam follower
8, cam lever 36, interlocking groove 37, interlocking pin 15
The rear group lens R moves relative to the front group lens F via the rear group lens frame 12. As a result, the copying magnification changes without changing the object-image distance. The above is an operation when the zoom lens 6 is configured according to the optical design, but in reality, as described above, the focus position changes due to optical manufacturing errors as the zoom is changed. Figure 4 is for explaining this change in focus position, and shows the copying magnification.
1.00x, 1.42x, and 0.64x are taken. In the figure, mF is the movement trajectory of the front group lens F, mR is the movement trajectory of the rear group lens R, and I is the document surface in optical design (focus surface: the focus position on the document side relative to the photoconductor surface). shows. If the optical components are manufactured as designed, the document surface I should be in focus at all magnifications, but if there is a manufacturing error, the focus position will change as shown by curve C. In response to this change in focus position, an adjustment method has conventionally been used in which the initial positions of the mirrors 4 and 5 (FIG. 3) are adjusted. This adjustment method is equivalent to moving the focal plane I by a distance A to become I'. However, with this adjustment method, there still remains a focus error of distance a on the 0.64x side and distance b on the 1.42x side. On the other hand, in the present invention, the initial position (reference setting position) of the front lens group F is set at a distance c as shown in FIG.
The relationship with the rear lens group R is maintained after adjustment, and the lens is moved along the movement trajectory mF'. This adjustment can be made by rotating the adjustment screw 21 shown in FIG. 1, as described above. And like this, the front group lens F
When the initial position (reference setting position) is adjusted, the focus position change curve shown by curve C in FIG. 4 becomes flat as the focus position change curve D shown in FIG. In other words, the adjustment amount c of the initial position of the front group lens F is set so that the change curve of the focus position is flattened. Even if the initial position of the front lens group F is adjusted in this way, the distance between the front lens group F and the rear lens group R will uniformly deviate from the initial value over the zoom range, which will have a negative effect on focus. will not be given. Once the focus position is flattened during zooming in this way, the distance between the object and image can be adjusted by moving a part of the optical member. That is, for example, as in the conventional adjustment method, mirrors 4 and 5 (third
(Fig.) by distance B and set the new focus plane.
I'', it is possible to achieve a good focus condition for each copying magnification. This is established by adjusting the initial position of the lens. The values written in Figures 4 and 5 correspond to 0.57% of the focal length for the zoom lens with the configuration shown in Figure 6 and the data in the table below. This figure specifically shows the amount of change in the focus position when an error occurs.

[Table] As can be seen from this example, when the focus position changes as shown in focus change curve C in Figure 4, mirrors 4 and 5 are adjusted by 4.746mm to achieve focus at the same magnification.
Even if it were moved, this adjustment would still leave errors of -1.417mm and +2.171mm at 1.42x and 0.64x, respectively. However, as shown in Figure 5, if the initial position of the front lens group F is moved by a distance of +0.674mm, the amount of focus movement at 1.42x, 1.00x, and 0.64x will be +2.180mm, +2.343mm, +, respectively.
Aligns with 2.180mm. Therefore, after that mirror 4, 5
By moving and adjusting the distance by an amount equivalent to the object-image distance + 2.262mm, the change in focus position will be ± from the same magnification in a wide copying magnification range of 1.42x to 0.64x.
It can be set to a sufficiently small value of within 0.082 mm. Furthermore, in the embodiment shown in FIG. 2, the light shielding/slit member 40 that cooperates with the photo interrupter 41 to determine the movement start point of the entire zoom lens system can be adjusted in movement with respect to the slide plate 17 on which the zoom lens 6 is mounted. , there is an advantage that the magnification can be adjusted independently of the focus position adjustment described above. In other words, even if good properties are obtained in which the amount of focus movement during zooming is sufficiently small as described above, the principal point position of the lens system will change due to manufacturing errors in the lens system, and the magnification will change from the initial setting magnification. However, as in the embodiment, by making it possible to adjust the position of the light shielding/slit member 40 that determines the movement start point of the zoom lens system, the magnification as initially set can be adjusted independently of the adjustment of the focus position. It is possible to obtain The "magnification error before adjustment" in the following table is calculated by adjusting the front lens group F by +0.674mm from the initial value in the above example.
Furthermore, the magnification error after changing the object-image distance of mirrors 4 and 5 by an amount equivalent to +2.262 mm is shown. The ``adjusted magnification error'' is obtained by adjusting the magnification error at 1.00x to 0% by adjusting the position of the light shielding/slit member 40 as described above. By adjusting the position of the light shielding/slit member 40 in this way, it is possible to adjust the magnification error after focus adjustment to a sufficiently small value.

[Table] ``Effects of the Invention'' As described above, according to the present invention, in the first step, the reference set position of the lens groups of the zoom lens is changed by a minute amount from the optical design value. By uniformly shifting the interval from the initial position over the range of magnification, it is possible to align the change curves of the focus position at a plurality of magnifications so that they become flatter. After the focus position is flattened during zooming in this way, a second step is performed to
By moving a part of the optical member, for example, a mirror, the distance between the object and image can be adjusted, and the focus position during variable magnification copying can be made constant to the extent that there is no problem in practical use.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the variable-reduction copying apparatus of the present invention, in which FIG. 1 is a sectional view taken along the line - in FIG. 2, FIG. 2 is an overall plan view, and FIG. 4 is a side view showing an example of the general configuration of a variable-magnification copying device, FIG. 4 is a graph showing how the focus position changes with zooming and the conventional adjustment method, and FIG. 5 is a graph showing the focus position adjustment according to the present invention. A graph showing how the focus position changes after that, and FIG. 6 is a lens configuration diagram showing a specific example of the zoom lens used in the present invention. F...Front group lens, R...Rear group lens, 1...
Document table, 4, 5...mirror, 6...zoom lens, 8...photosensitive drum, 11...front group lens frame, 12...rear group lens frame, 13...movable lens barrel,
17...Slide plate, 20...Interlocking plate, 2
DESCRIPTION OF SYMBOLS 1... Optical axis direction position adjustment screw, 27... Guide rod, 40... Light shielding/slit member, 41... Photo interrupter.

Claims (1)

[Claims] 1. A zoom lens consisting of one or more optical members and a plurality of lens groups is disposed in the optical path from the document surface to the photoconductor, and the zoom lens as a whole is moved at the same time. In a variable magnification copying device that changes the copying magnification while keeping the object-to-image distance constant by changing the spacing between the lens groups, adjusting a reference setting position of at least one constituent lens group of the zoom lens; a first step of aligning focus positions at a plurality of magnifications; and a second step of adjusting a distance between objects and images by moving a part of the optical member, and moving the focus position toward the photoreceptor surface. An optical adjustment method for a variable magnification copying device, characterized in that: 2. The optical adjustment method for a variable magnification copying apparatus according to claim 1, wherein the optical member for adjusting the object-image distance is a mirror disposed between the document surface and the photoreceptor. 3. An optical adjustment method for a variable magnification copying apparatus according to claim 1, wherein the starting point of movement of a slide plate that supports the entire zoom lens system is adjustable. 4 In claim 3, the slide plate is provided with a light shielding/slit member movable and adjustable in the optical axis direction, and the fixed base plate is provided with a light shielding/slit member that cooperates with the light shielding/slit member to adjust its movement starting point. A method for optical adjustment of a variable magnification copying machine, which is provided with a photointerrupter for determining. 5. In claim 1, the zoom lens has a front group lens and a rear group lens, and the front group lens is the above-mentioned component lens whose reference setting position in the optical axis direction is to be adjusted. Optical adjustment method for a variable magnification copying device.