JPH02154215A - Anamorphic variable power optical system - Google Patents

Abstract

PURPOSE:To obtain the anamorphic variable power optical system for a copying machine capable of anamorphic image formation over a wide power range by varying the relative distance of the two-group anamorphic lens system and the relative distance between a copying lens system and the anamorphic lens group. CONSTITUTION:When a main projection lens system I is at an optional power position, the main projection lens I and the lens 2 of the anamorphic lens system II for varying the power in a slit axis direction are arranged at an interval l1, the lenses 2 and 3 at an interval l2, and the lens 4 and a photo-sensitive body 4 at an interval S3 according to set power. Then only the power in a slit width direction is varied by selecting the intervals l1 and l2 properly and image formation is performed while the projection power in a slit length direction is still the set power of the main projection lens system 1. Consequently, the aspect ratio of an image can be varied over the wide power range and the anamorphic variable power optical system for the copying machine is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an anamorphic variable magnification optical system for a copying machine that can obtain good images over a wide magnification range.

[Prior Art] Conventionally, in an optical system for a copying machine capable of anamorphic magnification,
There are methods that shift the scanning speed of the document and peripheral speed of the photoconductor, and methods that use optical correction using a cylindrical lens (anamorphic magnification is fixed), but both methods have a limited magnification range. Therefore, the scope of application is narrow.

Furthermore, in recent years, digital copying machines have begun to appear, which are equipped with various editing functions in addition to the conventional variable magnification function. One of these image editing functions is the anamorphic scaling function, which is a function that changes the aspect ratio of the image.
Conventional analog copying machines have either been unable to achieve this, or have been unable to do anything other than disrupt the balance between the scanning speed of the document and the circumferential speed of the photoreceptor, resulting in slight distortion of the image.

[Invention or Problem to be Solved] Is there an anamorphic magnification function as one of the image editing functions of the above-mentioned digital copying machine? This is simply a function to change the aspect ratio of the image, and it is different from the conventional analog type copying machine. The only thing that I can do is either not be able to achieve this with a copying machine, or to the extent that it upsets the balance between the scanning speed of the original and the circumferential speed of the photoreceptor and slightly distorts the image. In addition, among the analog cylindrical lenses, the distance between the lens placed on the image side and the image plane is maintained, and the main lens is anamorphic.
The only way to change B to ri is to widen the anamorphic times 4A range.

This invention was made in view of these points, and it is possible to perform anamorphic imaging in a wide magnification range.
(The purpose is to provide an anamorphic variable magnification optical system for close-up copying.

[Means for Solving the Problems] This lens is composed of, in order from the object side, a cylindrical lens group with a negative power formed by at least one lens, and at least one lens. In a slit scanning type copying optical system that uses an anamorphic optical system consisting of a cylindrical lens group with positive power together with a compound lens system, the relative distances of the two groups of anamorphic lens systems and the copying lens system are This is an anamorphic variable magnification optical system characterized by continuously varying the aspect ratio of a copied image while maintaining a good image by changing the relative distance to the anamorphic lens group.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings. 1st
The figure is a side view showing the configuration of a scanning optical system of a copying machine to which the anamorphic optical system of the present invention is applied. The image of the original on the transparent original storage table 4 is illuminated by the illumination device 229, and the scanning mirrors 5, 6. 7, and is configured to form an image on the photoreceptor tram 4 via a projection lens A, a bending mirror 8, and an anamorphic lens system (2).

As shown in Fig. 2, the anamorphic variable magnification optical system is composed of a main projection lens system I and an anamorphic lens system ■, and Fig. 2 (A) shows a cross section IX1.
2nd [:, J(B) is a sectional view in the longitudinal direction of the slit. The main projection lens I is constructed of a lens system symmetrical with respect to the aperture S, and Table 1 shows the lens specifications.

(Margin below) Chapter 1 Table Side No.

νd! 46.027 6.50 1.776 :17.90 91.043 6.50 1.701 10.11 :I6.499 4.70 55.807 4.80 1.617 54.00 84.544 3.00 3.00 -84.544 4.80 1.617 54.00 -55.807 4.70 -36.499 6.50 1.701 30.11 -91.043 6.50 1.776 37.90 - 46.027 4-Foot Temperature In Table 1, r is the radius of curvature of the lens surface from the original side, d is the distance on the axis, n, 1, and υ,
are the refractive index and Abbe number of the glass material at the d-line.

The anamorphic lens II is composed of two lenses 2.3 each having a cylindrical surface having power in the slit width direction. Both sides of the lens 2 are composed of cylindrical surfaces that have power in the slit width direction, and the lens 3 has a cylindrical surface that has power in the slit width direction on the document surface side, and a cylindrical surface that has power in the slit width direction on the surface on the photoreceptor side. It is composed of cylindrical surfaces. Table 2 shows the lens specifications of this anamorphic lens system.

Table 2 0 5.50 1.19112
50.000 0 Standing 2 1:I 29.663 0 1:1.00 1.49+14
0 + 77j, :#7 57.4 57.4 These main projection lens system I and anamorphic lens system I change the magnification in the slit width direction when the main projection lens system is at an arbitrary magnification position. The lens 2゜3 of the anamorphic lens system II is connected to the main projection lens element and the fifull@f of the lens 2 as shown in No. 21A (A).
,, Distance between lens 2 and lens 3! 12. They are arranged at a distance S3 between the lens 3 and the photoreceptor (image surface) 4 in accordance with the set magnification. Then, by appropriately selecting the 32 sentences in the 7th section, only the magnification in the width direction of the slit is changed, and the projection magnification in the longitudinal direction of the slit remains the same as the magnification set by the main projection lens system engineer. It is.

This state will be further explained using the paraxial system shown in FIG. Main projection lens system that is twice the width of the slit*m! The product of the magnification m1 determined by the anamorphic lens [■] and the magnification m2 determined by
. The scanning speed υ of the original when it is bound is υ = η. ... (1) m, m.

You can coo with it. A good anamorphic variable magnification image can be obtained on the photoreceptor 4 by scanning the original so as to satisfy the above formula (1).

Next, an example of setting such a lens position will be shown.

Here, a case is shown in which the main projection lens system I is at the same magnification position.

Magnification in slit width direction m = 0.6 m = 0.9 M, = 266.11 sentences, = 294.983 sentences, = 3
7.29 Sentence, = 11.53 Distance S between the original surface and the 1st surface, = 407.28 5. = 407.28 Also, if the main projection lens system moves from the same magnification position due to a change in magnification, , while controlling the distance from the anamorphic lens system ■ to the photoreceptor 4 in the same way as when the main projection lens system ■ was at the same magnification position, the lens 2.3 of the anamorphic lens system H
By moving , it is possible to perform good anamorphic magnification.

Next, in order to explain the anamorphic variable magnification system of the present invention in more detail, paraxial analysis will be performed.

In FIG. 3, which is a paraxial power distribution diagram, the power of the main projection lens system I is set as f r + the power of the lens 2.3 of the anamorphic lens system H is set as 9', , y, and the object point of each lens and Let the distance to the image point be Si, Si′(i
=1.2.3) Also, the distance between lenses 2 and 3 of the main projection lens system ■ and the anamorphic optical system H is d, respectively.
,, d2, S+ S+ S x = S I-d + ... ■S,
S.

S3 = S2 - d.

2) An image forming system can be obtained using each lens as shown in S, 3. Next, the above <
,B)~(0) Solving equation for S3' yields S.

S:1 + 9'y! +82SPt 1 in 8292 S,', 'f' 2-A 'j' I, Ico =
8! /1, and further let r+-x, then S,--2
Therefore, when the anamorphic magnification is changed by moving the lenses 2 and 3 of the anamorphic optical system 11, assuming that the conjugate length of the entire system does not change, use S3'' in equation (2) below.

d+ +ct2+s=-2... Satisfying the condition (3), this is the solution for the paraxial power arrangement of the imaging system.

As in this example, an anamorphic lens system consisting of two groups of cylindrical lenses 2.3 with arbitrary power
The relative positions of the main projection lens system l and the main projection lens system l are expressed as (2) above,
By changing the expression (3) so as to satisfy the equation, it is possible to construct an anamorphic variable magnification optical system that can continuously vary the anamorphic magnification while maintaining the conjugate length of the entire system and obtain good imaging.

However, in such an optical system, if the angle of view used by the anamorphic optical system is large, the off-axis performance often deteriorates.In such cases, in order to improve the performance, it is necessary to increase the slit length. It is desirable that the surface having curvature in the f direction be a non-cylindrical surface.

Hereinafter, a design example thereof is shown in Table 3. Since the main projection lens system l is the same as in the above example, only the configuration of the anamorphic lens system is shown.

3rd surface No. r r” d nd
ya-81.982 5.50! , 491 57.4 150, :169 Cross 2 1200.000 11.0 1.49t 57.414 -40
．． 928 0 However, +rln' is the principal radius of curvature of the aspherical surface, and has the aspherical coefficient shown below.

Take the X axis in the direction of the optical axis, and the Y and Z axes in the direction perpendicular to this.
When the radius of curvature of the surface vertex is C8, the surface shape can be expressed by a general formula for an aspherical shape. And as a design example here, A,=-0,278754x 10-'A,=
0.4588733xlO-'A,,=-0. 286
2762xlO-13AA = 0.274628
3xlO-17A,. = 0. 1318189x
In this way, by changing the surface that aligns the image plane in the longitudinal direction of the slit from a cylindrical surface to an aspherical surface, the aberration characteristics at the peripheral viewing angles can be improved even when the two viewing angles are wide. , good imaging performance can be obtained.The lens shape at this time is shown in Figure 5 (A).
Shown in (B).

6(A) and (B) are the above-mentioned FIG. 2(A).

(B) shows an aberration curve diagram when an aspherical surface is not used;

An aberration curve diagram when the aspherical surface shown in (B) is used is shown. As can be seen from these figures, an anamorphic variable magnification optical system using an aspherical surface can significantly improve astigmatism at the outermost angle, resulting in extremely excellent image surface properties.

[Effects of the Invention] As explained above, the anamorphic variable magnification optical system of FJJ can change the aspect ratio of an image over a wide magnification range. Further, even if the anamorphic lens system is inserted into or removed from the copying imaging system, the conjugate length does not change, and it can be used as an optional function. Furthermore, since the conjugate length of the entire system does not change when changing the anamorphic magnification, a special conjugate correction mechanism is not required, and the configuration of the variable magnification system is simplified.

Furthermore, by making the surface having power in the longitudinal direction of the slit of the anamorphic lens system aspherical, an anamorphic variable magnification optical system that can obtain a good image up to the periphery of the screen even when the angle of view is large can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the anamorphic variable magnification optical system of the present invention applied to a scanning copying machine, and Figures 2 (A) and (B)
FIG. 2 is a sectional view in the slit width direction and the slit longitudinal direction showing the lens configuration of the anamorphic variable magnification optical system of the present invention. Figure 3 is a paraxial power distribution diagram of the lens system shown in Figure 2 above, Figure 4 is a graph showing the movement locus of the anamorphic lens system, and Figures 5 (A) and (B) are FIG. 3 is a cross-sectional view in the slit width direction and the slit longitudinal direction showing the lens configuration of an anamorphic variable magnification optical system using an aspheric surface. 6(A) and (B) are the above-mentioned FIG. 2(A). (B) is an aberration curve diagram of the anamorphic lens system. FIGS. 7(A) and (B) are the same as FIG. 5(A) above. It is an aberration curve diagram of the anamorphic lens system shown in (B). Copying lens system Anamorphic lens system Cylindrical lens Photoconductor Patent applicant Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A cylindrical lens group with negative power consisting of at least one lens in order from the object side;
In a slit-scanning copying optical system that uses an anamorphic optical system consisting of a cylindrical lens group with positive power consisting of two lenses together with a copying lens system, An anamorphic variable magnification optical system characterized in that the aspect ratio of a copied image can be continuously varied while maintaining a good image by changing the relative distance between the anamorphic lens system and the anamorphic lens group. 2. The imaging magnification determined by the copying lens system is m_1, and the magnification determined by the anamorphic lens group is m_1.
_2 and the circumferential speed of the photoreceptor is υ_0, the document scanning speed is υ while satisfying the following relationship: ▲ There are mathematical formulas, chemical formulas, tables, etc. Variable magnification optical system. 3. The anamorphic variable magnification optical system according to claim 1, wherein the cylindrical surface having a curvature in the longitudinal direction of the slit in the anamorphic lens system has an aspherical shape.