JP3407539B2 - Variable magnification eccentric optical system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable power decentering optical system, and more particularly to a rear projection type projector, HMD (head mounted display), HUD (headu).
The present invention relates to a variable power decentering optical system used for p display) and the like.

[0002]

2. Description of the Related Art Conventionally, a rear projection type projector has used an oblique projection optical system for projecting an image so that an image surface is inclined with respect to an object surface. For an HMD or HUD, a decentered mirror is used. A projection optical system with a wide field of view is used. In these projection optical systems, several decentered coaxial optical systems are combined in order to cancel out the asymmetrical image distortion (so-called trapezoidal distortion) caused by the tilt of the image plane and the decentering mirror. That is, the trapezoidal distortion is prevented from occurring by using an axially asymmetric optical system including a plurality of coaxial optical systems whose optical axes (symmetry axes) do not match.

In the axially asymmetric decentered optical system as described above, a variable magnification function (for example, a zoom function) for changing the image magnification while keeping the image plane position constant (for example, to always form an image at the image projection plane position). ), It is necessary to prevent the trapezoidal distortion from occurring during zooming.

Japanese Patent Application Laid-Open No. 5-119395 proposes a projection type display device which performs zooming without causing trapezoidal distortion. This apparatus includes a first projection optical system that forms an intermediate image with trapezoidal distortion and a second projection optical system that converts the intermediate image into an image without trapezoidal distortion. Then, the image magnification is changed by moving the second projection optical system in the direction of the chief ray, and the first and second
By rotating the projection optical system, the trapezoidal distortion is corrected while the image plane position remains constant.

Further, Japanese Patent Laid-Open No. 6-324285 proposes a visual display device capable of changing the image magnification with a simple mechanism. A decentering optical system is used in this visual display device, and the variable power lens group forming a part of the decentering optical system is movable in the optical axis direction.
Then, by moving the variable power lens group in the optical axis direction so that the magnification of the variable power lens group becomes β or 1 / β,
It is configured to switch the image magnification.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As proposed in Japanese Patent Publication No. 5, a complicated mechanism is required to drive a projection optical system that makes a complicated movement. If the drive mechanism becomes complicated, the entire device becomes large, which is disadvantageous in cost. Further, according to the visual display device proposed in JP-A-6-324285, the image magnification is 2
Since the steps are switched, it is not possible to continuously change the magnification.

The present invention has been made in view of the above points, and an object thereof is to make it possible to continuously perform variable magnification with a simple mechanism, and to prevent the image from being trapezoidally distorted during variable magnification. It is to provide a double decentered optical system.

[0008]

In order to achieve the above object, the variable power decentering optical system of the first invention comprises at least three .
Each includes a coaxial optical system eccentric to each other, and, seen including a zoom optical system including a plurality of zoom group, object plane and the image plane and
Is a variable magnification decentering optical system in a relationship that is not substantially parallel to each other, and the image magnification is continuously changed while the image plane position is kept constant by moving at least two of the zoom groups in parallel. Characterize.

In the variable power decentering optical system of the second invention, in the configuration of the first invention, the zoom optical system is a coaxial optical system, and the parallel movement of the zoom group is the optical axis of the zoom optical system. It is characterized by being performed in the direction. In the variable power decentering optical system of a third aspect of the invention, in the configuration of the first aspect of the invention, the position of the intermediate image plane formed by the light beam immediately after the exit of the zoom optical system is substantially moved when the zoom group is moved in parallel. Characterized by not doing. A variable power decentering optical system of a fourth invention is characterized in that, in the configuration of the second invention, the zoom optical system is an afocal zoom optical system.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A variable power decentering optical system embodying the present invention will be described below with reference to the drawings. 1 and 7
It is a lens block diagram of 1st, 2nd embodiment in a wide end. FIG. 1 shows an XY section of the first embodiment, and FIG. 7 shows an XY section of the second embodiment. Each of the embodiments including the axially asymmetric optical system includes the first to third lens groups Gr1 to Gr3 that form coaxial optical systems independent of each other.
It is composed of Gr3. Therefore, the optical axes (that is, symmetry axes) AX1 to AX3 of the first to third lens groups Gr1 to Gr3
Is a disagreement. In each lens configuration diagram, the X axis and the Y axis are orthogonal to each other, and the XY plane is parallel to the paper surface.

2 and 8 show the optical paths of the first and second embodiments, respectively. In each optical path diagram, OS is an object surface corresponding to the display surface of the image display element, and IS is an image surface formed by each embodiment. In these drawings, [W] indicates the optical path of each embodiment at the wide end, [M] indicates the optical path of each embodiment at the middle (intermediate focal length state), and [T] ] Shows the optical path of each embodiment at the tele end.

In each lens configuration diagram, ri (i = 1,2,3, ...) is the radius of curvature of the i-th surface counted from the object surface OS (FIG. 1, FIG. 7) side, and P1 to P3 is an eccentricity reference position of each lens group Gr1-Gr3. The surface apex of the first surface of the second lens group Gr2 is located apart from the eccentricity reference position P2 located on the optical axis AX2 by an axial distance D2, and the first lens group Gr1 and the third lens group Gr3. The surface vertices of the respective first surfaces are located at the eccentricity reference positions P1 and P3, respectively. And first to
The third lens groups Gr1 to Gr3 include eccentricity reference positions P1 to P3.
They are arranged at positions rotated clockwise around the X-Y plane along the X-Y plane. θ1 to θ3 respectively indicate tilt angles formed by the optical axes AX1 to AX3 with respect to the X axis in the XY plane.

Further, in each optical path diagram, PO is the center position of the object plane OS, and PI is the center position of the image plane IS. Object O
The image of S is projected such that the image plane IS is inclined with respect to the object plane OS. θO and θI are the object surface OS on the XY plane,
The tilt angles formed by the image plane IS with respect to the Y axis are shown.

In the first embodiment, the first lens group Gr1
And a second lens group Gr2 including a diaphragm S and a third lens group Gr3, and each of the lens groups Gr1 to Gr3.
Has an eccentricity with respect to the X axis by an inclination angle θ1 to θ3. The second lens group Gr2 includes the first zoom group GrA.
And a second zoom group GrB including the aperture S,
This is a two-group zoom optical system having a positive configuration. Zooming Figure 2
As shown in, the negative first zoom group GrA and the positive second zoom group GrB are moved in parallel in the optical axis AX2 direction at different moving speeds.

In the second embodiment, the first lens group Gr1 is used.
And a second lens group Gr2 including a diaphragm S and a third lens group Gr3, and each of the lens groups Gr1 to Gr3.
Has an eccentricity with respect to the X axis by an inclination angle θ1 to θ3. The second lens group Gr2 includes the first zoom group GrA.
And a second zoom group GrB including the stop S and a third zoom group GrC, which is a negative-positive-negative three-group afocal zoom optical system. As for zooming, as shown in FIG. 8, the negative first zoom group GrA and the positive second zoom group GrB are used.
Are performed by moving in parallel in the optical axis AX2 direction at different moving speeds.

As described above, the variable power decentering optical system according to the first and second embodiments includes at least one decentered coaxial optical system, and is a zoom optical system including a plurality of zoom groups. The system is included. The feature of these embodiments is that the image magnification (that is, the projection magnification) is continuously changed while the image plane IS position is kept constant by moving the first and second zoom groups GrA and GrB in parallel. It is in.

As described above, the first and second zoom groups Gr are arranged so that the image magnification continuously changes while the image plane IS position is constant.
By moving A and GrB in parallel, it is possible to prevent trapezoidal distortion from occurring in the image during zooming. Further, since zooming is performed by the parallel movement of the first and second zoom groups GrA and GrB, the first and second zoom groups G
No complicated mechanism is required for driving rA and GrB. That is,
A drive mechanism for causing the first and second zoom groups GrA, GrB to perform complicated movements including rotational movement is unnecessary. Since zooming can be performed by such a simple mechanism, the overall size of the device can be reduced and the cost can be reduced.

As described above, in the first and second embodiments, the second lens group Gr2 forming the zoom optical system is the coaxial optical system, and the first and second zoom groups GrA and GrB are the same. The parallel movement is performed in the optical axis AX2 direction. As described above, in the variable power decentering optical system, it is desirable that the zoom optical system is a coaxial optical system, and the parallel movement of the zoom group is performed in the optical axis direction of the zoom optical system. According to this configuration,
Since the zoom optical system (second lens group Gr2) can be configured in the same manner as a normal coaxial zoom optical system, no special technique is required for the lens barrel or the moving mechanism for zooming. Therefore, there are advantages that the lens barrel and the moving mechanism for zooming become simple and the cost is reduced.

In the first and second embodiments, the first and second embodiments
During the parallel movement of the zoom groups GrA and GrB (that is, during zooming), the position of the intermediate image plane formed by the luminous flux immediately after the emission of the second lens group Gr2 does not substantially move. As described above, in the variable magnification decentering optical system, the position of the intermediate image plane formed by the light beam immediately after the zoom optical system exits does not move (within the allowable aberration range) during the parallel movement of the zoom group. It is desirable to do. According to this configuration, the variation of the final image plane IS projected by the subsequent fixed lens group (third lens group Gr3) due to zooming is suppressed, so that aberration correction is facilitated.

When the position of the intermediate image plane formed by the luminous flux immediately after the second lens group Gr2 is emitted during zooming is set so as not to move substantially as described above,
The configuration is such that the trapezoidal distortion is corrected near the area with the largest image magnification {that is, near the wide end (shortest focal length) [W] area where the size of the image differs from that of the object) (that is, paraxial It is desirable to configure so that trapezoidal distortion does not occur). According to this structure, the projection angle of view becomes narrow in a region having a small image magnification (that is, the telephoto end [T] region).
Trapezoidal distortion, which is a problem in decentered optical systems, becomes inconspicuous in the entire zoom range. Therefore, restrictions on optical design are reduced.

As described above, the second lens group Gr2 forming the zoom optical system is formed of the coaxial optical system, and the second lens group Gr2 is formed.
In a configuration in which the position of the intermediate image plane formed by the light flux immediately after the two exits does not move substantially during zooming, the image formed on the intermediate image plane on the front side of the second lens group Gr2 (described later based on FIG. 13). In order to correct the trapezoidal distortion of the image, it is desirable that the optical axis AX2 of the second lens group Gr2 passes through the vanishing point of. The vanishing point of the image is a point at which the image magnification becomes infinitely small due to the trapezoidal distortion, and when the side edges of the trapezoid are extended in the plane on the image plane IS where the trapezoidal distortion occurs. Defined at the point of intersection. The state where there is no trapezoidal distortion is considered to be a state in which the height of the vanishing point on the object surface OS is infinite. Therefore, in a decentered optical system including a plurality of coaxial optical systems, the vanishing point of the image may be formed on the final image plane IS at infinite image height.
For that purpose, the vanishing point of the image relayed by the previous coaxial optical system may be located on the front focal plane of the final coaxial optical system.

A more preferable optical arrangement in which the trapezoidal distortion does not change due to zooming will be described with reference to FIG. I1 is an intermediate image plane of the object plane OS formed by the first lens group Gr1, and this intermediate image plane I1 is determined by the Scheimpflug condition. I2 is an image plane of the intermediate image plane I1 formed by the second lens group Gr2. VP1 is the vanishing point of the image on the intermediate image plane I1,
The magnification on the intermediate image plane I1 becomes infinitely small at this vanishing point VP1. VP2 is the vanishing point of the image on the intermediate image plane I2 (that is, the image of the vanishing point VP1), and the magnification on the intermediate image plane I2 becomes infinitesimally small at this vanishing point VP2. F1 ′ is the rear focal point of the first lens group Gr1, and f1 is the focal length of the first lens group Gr1. F3 is the third lens group Gr
3 is the front focal point, and f3 is the focal length of the third lens group Gr3.

The image surface of the object surface OS is formed as the intermediate image surface I1 by the first lens group Gr1. Intermediate image plane I1
Is re-imaged as an intermediate image plane I2 by the second lens group Gr2 which is a coaxial zoom lens. Optical axis AX2
Is perpendicular to the intermediate image plane I1, the intermediate image plane I2
Is also perpendicular to the optical axis AX2. Further, since the second lens group Gr2 is a zoom lens (zoom whose conjugate length does not change), the intermediate image plane I2 does not move during zooming. Then, the intermediate image plane I2 is re-imaged as the final image plane IS by the third lens group Gr3.

The second lens group Gr2 is composed of the first lens group Gr2.
It is arranged such that the optical axis AX2 passes through the vanishing point VP1 of the image located on the rear focal plane 1 (position of the focal point F1 ′). Therefore, at the optical axis AX2 passing position on the intermediate image plane I2,
The vanishing point VP2 of the image will be formed. Also, the third
The lens group Gr3 is arranged such that the vanishing point VP2 of the image is located on the front focal plane (position of the focus F3). As described above, since the intermediate image plane I2 does not move during zooming, the vanishing point VP2 of the image is always the third lens group Gr3.
Will be located on the front focal plane. Then, during zooming, the vanishing point VP2 of the image is constantly re-imaged at the final image plane IS position with an infinite image height. This means that the trapezoidal distortion-corrected final image plane IS is formed over the entire zoom range.

If the optical axis AX2 passes through the vanishing point VP1 of the image formed on the intermediate image plane I1 as described above, even if the image magnification of the intermediate image plane I2 varies during zooming, The position of the vanishing point VP2 on the optical axis AX2 does not change. Therefore, the trapezoidal distortion can be favorably corrected over the entire zoom range without affecting the subsequent correction of the trapezoidal distortion by the third lens group Gr3.

In FIG. 13, the intermediate image planes I1 and I2 are represented as real images for ease of explanation. However, even when a virtual image is relayed as an intermediate image plane, trapezoidal distortion is corrected by the same optical arrangement. It is clear that this will be done. If the configuration is such that a virtual image is relayed, the total lens length is shortened, which is more preferable. Further, the basic optical configuration shown in FIG. 13 is based on the intermediate image planes I1 and I2; the second lens group Gr2; the vanishing points VP1 and V.
Since the arrangement is P2, if this optical arrangement is satisfied, even if the first and third lens groups Gr1 and Gr3 are composed of a plurality of decentered lens groups, the trapezoidal distortion is corrected in the entire zoom range. It is clear that

In the second embodiment, the second lens group Gr
2 is an afocal system. As described above, in the decentered variable power optical system, it is desirable to use an afocal zoom optical system as the zoom optical system. In this case, the fixed lens group (first lens group Gr1) located closer to the object surface OS than the afocal system has a large magnification (preferably 100 times or more), and located closer to the image plane IS than the afocal system. Fixed lens group (3rd lens group Gr3) has a small reduction magnification
It is more desirable to have a configuration having (preferably 0.01 times or less).

Here, the principle of trapezoidal distortion correction by the afocal system will be described with reference to FIG. FIG. 14 schematically shows the basic structure of an afocal system applicable to the present invention. The afocal system includes a lens unit LA and a lens unit LB. fA is the focal length of the lens unit LA, fB is the focal length of the lens unit LB, A
X is the optical axis of the afocal system. Further, IN is an intermediate image plane (in this case, a virtual image) determined by the Scheimpflug condition, and VP is a vanishing point of the image on the intermediate image plane IN. At this vanishing point VP, the image magnification on the intermediate image plane IN becomes infinitely small due to the trapezoidal distortion.

The vanishing point VP of the image is located at the intersection of the back focal plane of the lens unit LA and the intermediate image plane IN. Further, the rear focal position of the lens group LA and the front focal position of the lens group LB are coincident with each other. Therefore, the vanishing point VP of the image is automatically located on the front focal plane of the lens unit LB. Therefore, the vanishing point VP of the image is expanded again to the infinite image height by the lens group LB, so that the trapezoidal distortion of the image is corrected.

If the afocal system is used, as shown in FIG. 14, even if the object surface OS, the intermediate image surface IN and the image surface IS are not perpendicular to the optical axis AX of the afocal system, the image surface IS
There is no trapezoidal distortion. Further, as described above, a fixed lens group having a large magnification on the front side of the afocal system.
If the (first lens group Gr1) is arranged, substantially parallel light beams are incident on the afocal system. That is, the intermediate image planes formed before and after the afocal system are located at an almost infinite distance with respect to the afocal system. Therefore, even if the afocal system is decentered in order to rotate the final image plane IS, substantially parallel light beams are emitted from the afocal system. As mentioned above, a fixed lens group having a small reduction magnification on the rear side of the afocal system.
If the (third lens group Gr3) is arranged, the substantially parallel light flux does not change before and after the eccentricity of the afocal system and is incident on the fixed lens group on the rear side. Therefore, it becomes possible to correct coma aberration with a small number of lenses (for example,
It becomes possible to reduce the number of lenses in the fixed lens group located before and after the afocal system).

By the way, generally, in a decentered optical system, light passes through a portion of the decentered lens group that is away from the optical axis. Therefore, there is a problem that the lens diameter tends to increase. In order to solve this problem in the variable power decentering optical system, it is desirable to provide an aperture in the zoom group that moves for variable power. Generally, a zoom optical system includes a plurality of zoom groups that move for zooming, and these zoom groups are greatly separated on the wide side or the tele side. If there is an aperture in the moving zoom group, the off-axis light beam (that is, the light beam away from the center of the screen) does not move too far from the optical axis of the zoom group, so the lens diameter of the zoom group moving for zooming. There is no need to increase. In the first and second embodiments, since the stop S is provided in the second zoom group GrB, the lens diameter of the second zoom group GrB is small.

In the first and second embodiments, the first and second zoom groups GrA and GrB for zoom movement are located adjacent to each other. In this way, it is desirable that the plurality of zoom groups that move for zooming be adjacent zoom groups. In a zoom group that moves for zooming, the height and direction of light passing therethrough are likely to change significantly with zooming.
In general, the larger the zoom group interval, the greater the difference in height and direction of light passing through the zoom groups. Therefore, when the zoom groups that move for zooming are separated from each other, the light passing height in at least one zoom group tends to be high, and further, the fluctuation thereof becomes large due to the zoom movement. As a result, it becomes necessary to increase the lens diameter in order to pass an off-axis light beam, and it becomes difficult to suppress aberration fluctuations due to zooming. If the adjacent zoom groups are configured to move for zooming, such a problem is less likely to occur, so that it is possible to reduce the lens diameter and suppress aberration fluctuations due to zooming.

As described above, in the first embodiment, the second lens group Gr2 is composed of two groups, negative and positive,
In the second embodiment, the second lens group Gr2 is composed of three negative, positive and negative groups. As described above, it is desirable that the zoom optical system include at least one positive power zoom group and at least one negative power zoom group as the zoom group that moves for zooming.

As described above, in the variable magnification decentering optical system for oblique projection provided with the zoom optical system, it is necessary to make the intermediate image plane positions before and after the zoom optical system substantially unchanged during zooming. Yes (see FIG. 13). However, if all the zoom groups that move due to zooming have positive power, each zoom group can only converge the light rays, so a real image must be formed in the zoom optical system in order to use divergent light. Will not happen. When a real image is formed in the zoom optical system, when trying to obtain a sufficient change in magnification,
The zoom optical system becomes large. On the contrary, when all the zoom groups that move for zooming have negative power, each zoom group can only diverge the light beam,
It becomes difficult to obtain a sufficient change in magnification. Further, if the zoom optical system is configured by only the positive or negative zoom group, the positive or negative power is predominant in the zoom optical system as a whole, and it is difficult to correct the field curvature. .

If the zoom optical system includes at least one zoom group having positive and negative powers as a zoom group that moves for zooming, the above-mentioned problems are less likely to occur. Therefore, even if it is compact, a sufficient change in magnification can be obtained, and the curvature of field can be easily corrected.

Although each embodiment has been described as an enlarged projection system for projecting an image on a screen, the present invention is a reduction projection system (for example, a photographing system for projecting an image on a film, a CC system).
It is also applicable to an image input system for projecting an image on D or the like). That is, in each of the embodiments, the image plane IS is changed to the object plane O.
Even when the object surface OS is replaced with the image surface IS for S, the zoom function can be realized with the same configuration.

[0037]

EXAMPLES The configuration of a variable power decentering optical system embodying the present invention will be described more specifically below with reference to construction data and the like. Examples 1 and 2 given here as examples
Are examples corresponding to the above-described first and second embodiments (FIG. 1, FIG. 2; FIG. 7, FIG. 8), respectively. And
In the construction data of each example, ri (i =
(1,2,3, ...) is the radius of curvature of the i-th surface counted from the object surface OS side, and di (i = 1,2,3, ...) is the i-th surface counted from the object surface OS side. Shows the axial distance between the axes, and Ni (i = 1,2,3, ...) is the refractive index (Nd) of the i-th lens from the object surface OS side with respect to the d-line.
Is shown.

The position in the construction of each embodiment is represented by an absolute coordinate system (X, Y, Z), and as shown in each lens configuration diagram, the X axis and the Y axis are orthogonal to each other (the XY plane). Is parallel to the paper surface), and the Z axis is taken in the direction perpendicular to the X axis and the Y axis. As described above, each lens group G
r1 to Gr3 form a coaxial optical system independent of each other, and form an axially asymmetric optical system in a state where the lens groups Gr1 to Gr3 are decentered from each other.

The eccentricity reference position P1 corresponds to the first lens group Gr1.
Is the surface apex of the first surface (the surface having the radius of curvature r1). Optical axis AX2
The eccentricity reference position P2 located above is the second lens group Gr2.
Is located away from the surface apex of the first surface (the surface having the radius of curvature r7) by the axial distance D2. The eccentricity reference position P3 is the apex of the first surface (the surface having the radius of curvature r22 in the first embodiment, the surface having the radius of curvature r28 in the second embodiment) of the third lens group Gr3. Then, the coordinates (X, Y, Z) of the eccentricity reference position P1 = (X1, Y1, Z1) and the coordinates (X, Y, Z) of the eccentricity reference position P2 = (X2, Y2, Z2). Yes, the coordinates (X, Y, Z) of the eccentricity reference position P3 = (X3, Y3, Z3). Further, the optical axes AX1 to AX3 of the first to third lens groups Gr1 to Gr3
The inclination angles θ1 to θ3 (°) are rotation angles about the Z axis (clockwise is positive) about the eccentricity reference positions P1 to P3 with respect to the X axis.

Coordinates (X, Y, Z) = (X of center position PO of object surface OS
O, YO, ZO), and the coordinates (X, Y,
Z) = (XI, YI, ZI). The inclination angle θO (°) of the object surface OS and the inclination angle θI (°) of the image surface IS are rotation angles around the Z axis about the center positions PO and PI with respect to the Y axis (clockwise is positive). Is.

The object surface OS corresponds to the display surface of the image display element or the like. When the size is the z-axis in the same direction as the Z-axis and the y-axis is in the direction perpendicular to the z-axis and parallel to the object OS, the center position PO of the object OS is It is represented by coordinates (y, z) with the origin as. The maximum coordinate in the y-axis direction of the image display element on the object surface OS is ymax, and the minimum coordinate in the y-axis direction of the image display element on the object surface OS is ymin. Further, the maximum coordinate in the z-axis direction of the image display element on the object surface OS is zmax, and the minimum coordinate in the z-axis direction of the image display element on the object surface OS is set.
zmin

In the construction data of each embodiment, the image magnification β _z (Z-axis direction), which varies with the movement of the first and second zoom groups GrA and GrB; the axial upper surface distance D2, d12,
The data regarding d21 are shown in correspondence with the focal length states [W], [M], and [T] in the optical path diagrams of the respective examples. That is, in each embodiment, the data at the wide end [W] is appended with [W], the data at the middle [M] is appended with [M], and the data at the tele end [T] is added. It is indicated by adding [T] at the end of.

<Example 1><Object surface OS (14 mm square)> PO ... XO = -85.171 YO = 0.000 ZO = 0.000 θO = 13.473 ymax = 7, ymin = -7 zmax = 7, zmin = -7 <Gr1 〉 P1 ... X1 = -30.000 Y1 = -1.145 Z1 = 0.000 θ1 = 12.888 [Radius of curvature] [Axis upper surface spacing] [Refractive index] r1 = 30.329 d1 = 7.125 N1 = 1.70000 r2 = 514.864 d2 = 6.000 r3 = -28.207 d3 = 2.085 N2 = 1.57800 r4 = 39.206 d4 = 3.000 r5 = 210.110 d5 = 4.973 N3 = 1.70800 r6 = -29.961 <Gr2> P2 ... X2 = -5.000 Y2 = -5.635 Z2 = 0.000 θ2 = 4.257 D2 = 5.000 [W] 〜 5.924 [M] ~ 0.572 [T] [Radius of curvature] [Spacing between shafts] [Refractive index] r7 = 43.616 d7 = 1.400 N4 = 1.67003 r8 = 16.000 d8 = 6.100 r9 = -89.833 d9 = 1.200 N5 = 1.74400 r10 = 90.321 d10 = 1.100 r11 = 29.006 d11 = 3.200 N6 = 1.70055 r12 = 125.790 d12 = 2.000 [W] to 11.348 [M] to 24.232 [T] r13 = ∞ (aperture S, aperture radius = 4) d13 = 1.000 r14 = 34.146 d14 = 2.400 N7 = 1.69100 r15 = -65.639 d15 = 0.150 r16 = 16.183 d16 = 3.500 N8 = 1.62280 r17 = 34.134 d17 = 2.300 r18 = -117.051 d18 = 4.000 N9 = 1.80518 r19 = 15.140 d19 = 2.100 r20 = 151. 683 d20 = 2.000 N10 = 1.63980 r21 = -24.783 <Gr3> P3 ... X3 = 52.407 Y3 = -11.444 Z3 = 0.000 θ3 = 3.438 [curvature radius] [axis upper surface interval] [refractive index] r22 = -36.414 d22 = 2.500 N11 = 1.70055 r23 = -16.628 d23 = 0.700 r24 = -21.501 d24 = 1.000 N12 = 1.74400 r25 = 7981.674 d25 = 5.000 r26 = -12.826 d26 = 1.000 N13 = 1.67003 r27 = -21.275 <image surface IS> PI… XI = 612.449 YI = 1.536 ZI = 0.000 θI = 8.821 β _z = -16.06 [W] ~ -11.67 [M] ~ -8.48 [T]

Example 2 <Object surface OS (6 mm square)> PO ... XO = -85.171 YO = 0.000 ZO = 0.000 θO = 5.618 ymax = 3, ymin = -3 zmax = 3, zmin = -3 <Gr1 > P1 ... X1 = -30.000 Y1 = -2.704 Z1 = 0.000 θ1 = 5.648 [Radius of curvature] [Axis top surface interval] [Refractive index] r1 = 29.122 d1 = 7.125 N1 = 1.70000 r2 = 259.634 d2 = 6.000 r3 = -34.045 d3 = 2.085 N2 = 1.57800 r4 = 30.563 d4 = 3.000 r5 = 87.859 d5 = 4.973 N3 = 1.70800 r6 = -35.272 <Gr2> P2 ... X2 = -5.000 Y2 = -1.139 Z2 = 0.000 θ2 = 6.217 D2 = 5.000 [W] 〜 5.924 [M] ~ 0.572 [T] [Radius of curvature] [Spacing between shafts] [Refractive index] r7 = 43.616 d7 = 1.400 N4 = 1.67003 r8 = 16.000 d8 = 6.100 r9 = -89.833 d9 = 1.200 N5 = 1.74400 r10 = 90.321 d10 = 1.100 r11 = 29.006 d11 = 3.200 N6 = 1.70055 r12 = 125.790 d12 = 2.000 [W] to 11.294 [M] to 24.104 [T] r13 = ∞ (aperture S, aperture radius = 4) d13 = 1.000 r14 = 32.893 d14 = 2.400 N7 = 1.69100 r15 = -68.245 d15 = 0.150 r16 = 16.011 d16 = 3.500 N8 = 1.62280 r17 = 34.207 d17 = 2.300 r18 = -108.225 d18 = 4.000 N9 = 1.80518 r19 = 15.185 d19 = 2.100 r20 = 161.817 d20 = 2.000 N10 = 1.63980 r21 = -25.266 d21 = 27.572 [W] to 17.353 [M] to 9.896 [T] r22 = -50.100 d22 = 1.600 N11 = 1.70
055 r23 = -15.475 d23 = 0.550 r24 = -28.090 d24 = 0.600 N12 = 1.74
400 r25 = 48.182 d25 = 3.050 r26 = -10.229 d26 = 0.700 N13 = 1.67
003 r27 = −22.325 <Gr3> P3 ... X3 = 72.000 Y3 = -9.595 Z3 = 0.000 θ3 = 5.526 [curvature radius] [axis upper surface interval] [refractive index] r28 = 58.991 d28 = 6.630 N14 = 1.70800 r29 = -60.294 d29 = 4.000 r30 = -18.319 d30 = 2.780 N15 = 1.57800 r31 = -79.557 d31 = 8.000 r32 = -38.309 d32 = 9.500 N16 = 1.70000 r33 = -41.221 <Image plane IS> PI ... XI = 471.844 YI =- 0.402 ZI = 0.000 θI = 6.000 β _z = -15.65 [W] 〜-11.40 [M] 〜-8.28 [T]

The imaging characteristics of the first embodiment are shown in FIGS. 3 to 5 for the wide end [W], the middle [M], and the tele end [T] shown in FIG.
Are shown in the spot diagram (0.5 mm scale). Further, the imaging characteristics of Example 2 are shown in the spot diagrams (0.5 mm scale) of FIGS. 9 to 11 for the wide end [W], the middle [M], and the tele end [T] shown in FIG. 8, respectively. . The values of Y and Z attached to each spot diagram are Y and Z of the position of the image forming center of gravity on the image plane IS.
Coordinates.

Next, the distortion of each embodiment will be described. The z'axis is taken in the same direction as the Z axis and is perpendicular to the z'axis, and
The y'axis is taken in the direction parallel to the image plane IS. y'-
The distortion (that is, the actual image) of Embodiments 1 and 2 on the image plane IS viewed in the direction perpendicular to the z ′ plane is represented by the wide end [W], the middle [M], and the tele end [T] ( 2 and 8) are shown by solid lines in FIGS. 6 and 12. The broken lines in FIGS. 6 and 12 represent ideal images without distortion.

If the y'axis and the z'axis are taken as described above, the image height is the image plane IS with the center position PI of the image plane IS as the origin.
It is represented by the upper coordinates (y ', z'). Therefore, the height coordinate (y, z)
= (a, b) and the coordinate of the ideal image height corresponding to (y ', z') = (a ', b'), the actual image height coordinate on the image plane IS is (a '+ dy ', b'
+ dz ') (here, + dy': distortion generated in the y'axis direction, + dz ': distortion generated in the z'axis direction). Since the ideal image height is represented by the distance from the center position PI of the image plane IS to the coordinates (a ', b'), the ideal image height R is calculated by the formula: R = (a ' ² + b' ² ).
^{Expressed as 1/2} . Therefore, the strain curvature in the y'axis direction is defined by dy '/ R, and the strain curvature in the z axis direction is defined by dz' / R. The strain curvatures dy '/ R and dz' / R of Examples 1 and 2 were measured at wide end [W], middle
[M] and tele end [T] (FIGS. 2 and 8) are shown in Table 1 and Table 2, respectively. Here, since the ideal image point is defined by the image magnification β _z in the z′-axis direction (that is, the Z-axis direction), the coordinates of the ideal image height are (a ′, b ′) = (β _z · a, β _z・ b).

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

As described above, according to the first to fourth aspects of the present invention, the parallel movement of at least two zoom groups causes the image magnification to continuously change while the image plane position remains constant. No trapezoidal distortion occurs in the image, and zooming can be performed with a simple mechanism. Since the mechanism for driving the zoom group can be simplified, it is possible to achieve compactness and cost reduction of the entire device.

According to the second aspect of the present invention, since it is possible to perform zooming by using a normal coaxial zoom optical system, the structure of the lens barrel and the moving mechanism for zooming can be simplified and the cost can be reduced. Can be realized. According to the third aspect, the fluctuation of the final image plane due to zooming is suppressed, so that aberration correction becomes easy. According to the fourth aspect, since the afocal system is used as the zoom optical system, coma aberration and the like can be corrected with a small number of lenses.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens configuration at a wide end according to a first embodiment (Example 1).

FIG. 2 is an optical path diagram in each focal length state of the first embodiment (Example 1).

FIG. 3 is a spot diagram at the wide end in Example 1.

FIG. 4 is a middle spot diagram in Example 1.

FIG. 5 is a spot diagram at the tele end in the first embodiment.

FIG. 6 is a diagram showing distortion in each focal length state in the first embodiment.

FIG. 7 is a diagram showing a lens configuration at a wide end according to a second embodiment (Example 2).

FIG. 8 is an optical path diagram in each focal length state of the second embodiment (Example 2).

9 is a spot diagram at the wide end in Example 2. FIG.

FIG. 10 is a middle spot diagram in Example 2.

11 is a spot diagram at the tele end in Embodiment 2. FIG.

FIG. 12 is a diagram showing distortion in each focal length state in the second embodiment.

FIG. 13 is an optical configuration diagram for explaining a desirable optical arrangement in which a variation in trapezoidal distortion due to zooming does not occur.

FIG. 14 is an optical configuration diagram for explaining the principle of trapezoidal distortion correction by an afocal system.

[Explanation of symbols]

Gr1 ... First lens group Gr2 ... Second lens group (zoom optical system, afocal zoom optical system) GrA ... First zoom group GrB ... Second zoom group GrC ... Third zoom group Gr3 ... Third lens group AX1 ... Optical axis of 1 lens group (symmetry axis) AX2 ... Optical axis of 2nd lens group (symmetry axis) AX3 ... Optical axis of 2nd lens group (symmetry axis) P1 ... Eccentric reference position of 1st lens group (first P2 of the first surface of the lens group) P2 ... Eccentricity reference position of the second lens group P3 ... Eccentricity reference position of the third lens group (surface apex of the first surface of the third lens group) S ... Aperture OS ... Object surface IS ... Image surface θ1 ... Inclination angle θ1 of first lens group ... Inclination angle θ2 of second lens group ... Inclination angle θO of third lens group ... Inclination angle θI of object surface ... Inclination angle I1 of image surface ... Intermediate Image plane I2 ... Intermediate image plane IN ... Intermediate image plane

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-119283 (JP, A) JP-A-4-70806 (JP, A) JP-A-60-184222 (JP, A) JP-A-61-1 59306 (JP, A) JP 58-62611 (JP, A) JP 3-141309 (JP, A) JP 4-243207 (JP, A) JP 6-27372 (JP, A) JP-A-7-333561 (JP, A) JP-A-7-311407 (JP, A) JP-A-3-58042 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 15/00 G02B 13/00 G02B 27/64

Claims (4)

(57) [Claims] 1. A comprises at least three coaxial optical system eccentric to each other, and, seen including a zoom optical system including a plurality of zoom group, and object plane and the image plane is parallel optically substantially
A variable magnification decentering optical system having a non- existent relationship, characterized in that the image magnification is continuously changed while the image plane position is kept constant by moving at least two zoom groups in parallel. Core optics. 2. The variable magnification eccentricity according to claim 1, wherein the zoom optical system is a coaxial optical system, and the parallel movement of the zoom group is performed in the optical axis direction of the zoom optical system. Optical system. 3. The variable eccentricity according to claim 1, wherein the position of the intermediate image plane formed by the light beam immediately after the exit of the zoom optical system does not substantially move during the parallel movement of the zoom group. Optical system. 4. The variable power decentering optical system according to claim 2, wherein the zoom optical system is an afocal zoom optical system.