JPH01178916A - Photography system with image deflecting method - Google Patents

Abstract

PURPOSE:To correct the blur of a photographed image while compensating variation in power chromatic aberration excellently by setting the lens constitution of a 1st lens group arranged on an object side about a variable vertical angle prism and a 2nd lens group arranged on an image plane side and the constitution of the variable vertical angle prism properly. CONSTITUTION:The photography system has an image deflecting means which deflects the photographed image by varying the vertical angle of the variable vertical angle prism, and respective lens groups and the variable vertical angle prism are constituted which meet requirements shown by expressions I and II, where T1 and T2 are the coefficients of power chromatic aberrations of 1st and 2nd lens groups and Np and Np' are refractive indexes of the variable vertical angle prism to reference wavelength and 2nd wavelength when the focal length of the whole system is normalize into '1'. Consequently, the generation of an eccentric power chromatic aberration is reduced, and the blur of colors at the time of eccentric driving is reduced to obtain an image of high quality with high contrast.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a photographing system having an image deflecting means, and in particular, a variable apex prism having a variable apex angle is provided in the lens system, and the variable apex angle The present invention relates to a photographing system having an image deflecting means suitable for a photographic camera, a video camera, etc., in which a photographed image is deflected by a prism to correct image blur caused by vibration or the like.

(Conventional technology) When photographing from the ring of a moving vehicle, vibrations are transmitted to the photographing system.
The photographed image becomes blurred. Conventionally, various imaging systems have been proposed that have image deflection means that corrects the image blurring by arranging a plane parallel plate or a variable apex angle prism in the optical system.

For example, Japanese Patent Publication No. 56/21133 proposes an imaging system that uses a variable apex angle prism to correct image blur. In this publication, a liquid or a transparent elastic body is sealed between two parallel plane glasses, and the angle formed by the two plane parallel plates is made variable to correct image blur.

In addition, the same publication proposes an imaging system in which image blur is corrected by varying the angle formed by opposing planes by sliding a plano-convex lens and a plano-concave lens with curvature between spherical surfaces.

Generally, when a variable apex prism is placed in front of or inside a lens system to correct image blur, if the apex angle of the variable apex prism reaches a certain angle, the chromatic dispersion of the prism will cause the image to change. Eccentric lateral chromatic aberration occurs along with deflection.

This effect is shown in FIG. P is a variable apex angle prism, and when the apex angle is changed as shown in FIG. 10(A), the g-line is deflected more than the d-line. Therefore, if a variable apex angle is attached to the master lens M as shown in FIG. 10(B), decentering lateral chromatic aberration will occur if an attempt is made to deflect an image.

This decentered chromatic aberration of magnification occurs over the entire screen from the center to the periphery with a substantially concave amount and in the same direction, causing a decrease in contrast and color blurring. In this way, eccentric chromatic aberration of magnification, unlike normal chromatic aberration of magnification, occurs also at the center of the screen of the main subject, and is therefore a major cause of deterioration in image quality.

In contrast, U.S. Patent No. 3514192 and Japanese Patent Publication No. 57
Publication No. 7416 proposes an imaging system that uses two variable apex angle prisms with different dispersions and drives them while maintaining a constant angular ratio to satisfy the achromatic condition, thereby reducing the occurrence of eccentric lateral chromatic aberration. There is.

However, this method requires two variable apex angle prisms, increases the thickness of the deflection element, and tends to require a relatively complex structure for driving the two prisms while maintaining a constant angular ratio. .

In addition, in Japanese Patent Application Laid-open No. 61-223819, a cemented lens with almost zero refractive power is provided at the rear of the imaging system in addition to the variable apex angle prism, and the optical axis is aligned in synchronization with the movement of the variable apex angle prism. We are proposing an imaging system that corrects eccentric lateral chromatic aberration using a variable apex angle prism method by eccentrically driving the lens in the vertical direction.

In this method, two optical elements located far apart must be driven in precise synchronization, making the control structure complicated, increasing the size of the device, increasing the number of moving parts in the optical system, and adding the need for a cemented lens. There were problems such as the influence of tilt.

In addition, Japanese Patent Publication No. 56-40805 proposes a photographing system that corrects image blur by forming a prism with a substantially variable apex angle using a rotational sliding system of plano-convex and plano-concave lenses. are doing.

However, although this method can reduce the occurrence of eccentric lateral chromatic aberration, the variable apex angle prism tends to become relatively large.

(Problems to be Solved by the Invention) The present invention includes a variable apex prism with a variable apex angle arranged in a lens system, and when correcting blur in a photographed image, the variable apex prism is placed closer to the object side than the variable apex prism. By appropriately setting the lens configurations of the first lens group and the second lens group located on the image plane side, and the configuration of the variable apex prism, it is possible to satisfactorily correct the optical performance of the entire screen, especially fluctuations in lateral chromatic aberration. It is an object of the present invention to provide a photographing system having an image deflecting means capable of correcting blur in a photographed image.

(Means for solving the problem) A fixed first lens group, a variable apex angle prism whose apex angle is variable, and a fixed second lens group are arranged in order from the object side, and the apex angle of the variable apex angle prism is fixed. In a photographing system having an image deflecting means configured to deflect a photographed image by changing the chromatic aberration coefficient of magnification of the first lens group and the second lens group when the focal length of the entire system is normalized to 1. each TI
.

T2, the refractive index of the variable apex prism for the reference wavelength and the second wavelength is NP and NP', respectively, and δN P= I N
When P NP ' I -0,012< T2
- (δNP) / (NP-1) < 0.01
2...-(1) The following conditions must be satisfied.

(Example) Figures 1, 2, and 3 are numerical examples 1.2 of the present invention.
FIG. 3 is a cross-sectional view of the lens of No. 3. In the same figure, the work is the fixed first
The lens group P is a variable apex angle prism having a variable apex angle, and constitutes a part of the image deflection means. 3 is a fixed second lens group.

In this embodiment, the blur of the captured image is corrected by changing the prism apex angle of the variable apex angle prism P. The first of these. In the embodiment shown in FIG. 2, a transparent silicone rubber is sealed between two glass plates to constitute a variable apex angle prism, and the apex angle is changed by being driven by an actuator to correct image blur.

In this embodiment, the light beam exiting the first lens group is approximately afocal. When the axial ray of light incident on the variable apex prism is close to afocal, that is, when the focal length of the entire system is fT, the inclination α of the axial paraxial ray is approximately 1α.
If it is small enough to satisfy the condition l<0.3<fa, the occurrence of decentered comatic aberration, decentered astigmatism, and decentered curvature of field in the variable apex angle prism will be smaller than in the case where it is not an afocal light beam. If the spherical aberration, coma aberration, and astigmatism of the partial system of the second lens group are corrected to a small value, the occurrence of decentered comatic aberration, decentered astigmatism, and decentered curvature of field can be reduced in principle, and the second lens group The number of constituent lenses can be reduced.

Furthermore, if the variable apex angle prism is constructed by sealing transparent silicone rubber between two glass plates as in this example,
It has the advantage of being able to create a variable apex angle prism with a small thickness.

In the embodiment shown in FIG. 3, a variable apex prism is formed by a plano-convex lens and a plano-concave lens whose opposing lens surfaces have the same radius of curvature, and the angle formed by the opposing planes is adjusted by sliding the opposing lens surfaces against each other. It is made variable and the apex angle is essentially changed.

In the present invention, in the above configuration, by setting the lens configurations of the first lens group and the second lens group and the configuration of the variable apex prism as described above, it is possible to take pictures while maintaining good optical performance of the entire screen. Corrects image blur.

Figure 7 shows that any one lens surface ν in the lens system has an angle ε
An explanatory diagram of the decentering aberration coefficient when V eccentricity is applied. Fig. 8 shows a case where the apex angle of the variable apex angle prism is not changed in the imaging system according to the present invention, and Fig. 9 shows a case where the apex angle of the variable apex angle prism is changed. FIG.

Of these, FIG. 8 shows the optical paths of the on-axis light beam and the off-axis light beam at two wavelengths, the d-line as the reference wavelength and the g-line as the second wavelength. Further, FIG. 9 shows a state in which the optical path of the axial light beam at two wavelengths, d-line and g-line, is deflected by ΔY when the apex angle of the variable apex angle prism is changed by 6.

First, decentering aberration in this example will be explained using FIG. 7. Regarding eccentric aberration when the υ-th lens surface ν in the lens system is tilted by an angle ε9 as shown in Fig. 7, see "Setting third-order eccentric aberration and tolerance, 1975, Lens Design Seminar, chapter 7; Ozeki". It has been stated. According to this, the decentered lateral chromatic aberration Δ(ΔY) is Δ(ΔY) = -cosφV ”TV・εν・fT/
α′〒v=hv (Nv-NV)(Σe+IT
−(π/h)9 Σe+IL) −NV−LV/ (h
-q) It can be expressed as V. Here, the aberration coefficient and paraxial amount are values when the focal length of the entire system is normalized to 1, fT is the focal length of the entire system, and TV is the eccentric magnification chromatic aberration coefficient when the V-th lens surface υ is tilted. It is.

Next, apply this formula to a variable apex angle prism, transform it, and organize it. If the prism surface is represented by a subscript P, and the fixed lens group after the variable apex prism, that is, the second lens group is represented by a subscript 2, then Δ (ΔY) = −cosφ2・ε2・fT・((N
Pl) (hpL2-hpT2)"hp(δNP))
/ becomes αe′. Here, NP is the reference wavelength for the variable apex prism, for example, the refractive index of the d-line, (δNp)
is the second wavelength of the variable apex prism, for example, when the refractive index of the g-line is N2, the difference in the refractive index of the reference wavelength d-line is 1NP-
It is N2I. In order to prevent decentering lateral chromatic aberration, Δ
Since it is necessary that (Δy)=o (NPl) (hPL2-hPT2) +hp(δN
P) The condition for phantom 0 is the coefficient L2 and T of the second lens group.
2 should be satisfied. In this equation, both the axial chromatic aberration and the lateral chromatic aberration of the second lens group are related,
When a variable apex angle prism is provided inside the lens as in the present invention, it is often considered to be near the aperture, and in that case, hP will be a small value and the lateral chromatic aberration of the second lens group will be smaller than the correction of eccentric lateral chromatic aberration. becomes dominant. Therefore, in general, the chromatic aberration of the second lens group may be corrected so as to satisfy the condition T2Lr(δNP)/(NP-1).

Since the right side of this equation is a positive value, if the chromatic aberration of magnification of the second lens group is corrected so as to be significantly under-produced, the occurrence of eccentric chromatic aberration of magnification can be reduced. In fact, if the coefficient T2 satisfies the above-mentioned conditional expression, the occurrence of decentered lateral chromatic aberration can be minimized to the extent that there is no negative effect. If the lower limit of conditional expression (1) is exceeded, the eccentric chromatic aberration of magnification is insufficiently corrected, and if the upper limit is exceeded, the eccentric chromatic aberration of magnification is overcorrected, and the eccentric chromatic aberration of magnification is moved in the opposite direction to that when no correction is made. Occur.

Furthermore, in order to correct the lateral chromatic aberration in the reference state, T
If 1 is the lateral chromatic aberration coefficient of the first lens group, then I −1,3<−<−0,7・・・・・・−<
It is preferable that conditional expression 2) be satisfied. This causes the lateral chromatic aberration of the first lens group to occur in the opposite direction to that of the second lens group,
This means making a well-balanced correction.

When the lower limit of conditional expression (2) is exceeded, lateral chromatic aberration of magnification remains in the over direction in the reference state, and when the upper limit of conditional expression (2) is exceeded, lateral chromatic aberration remains in the under direction in the reference state, The chromatic aberration of magnification is large, making it impossible to obtain satisfactory image quality.

In addition, in the above formula, the coefficient of magnification chromatic aberration T1 of each lens surface is calculated according to Matsugen's "Lens Design Method J (', 81 Kyoritsu Shuppansha). If the focal length of the entire system is normalized to 1, The lateral chromatic aberration Δ(Δy) of the system can be expressed as follows.

Next, the lateral chromatic aberration coefficient due to the variable apex angle prism will be explained using FIGS. 8 and 9.

In a variable apex angle prism with a wedge angle ε, the g-line ray is refracted more than the d-line, so lateral chromatic aberration due to the variable apex prism (this is also decentered lateral chromatic aberration) Δ(ΔY)P is Δ(ΔY) P a: ta
n(Δω)Δω gradient-6·(NPl) (NP is the refractive index of the prism) and occurs in the over direction in proportion to the deflection angle of the variable apex prism. On the other hand, lateral chromatic aberration is proportional to the angle of view. In the eccentric state where the apex angle is changed, the angle of view when the light beam is incident on the second lens group corresponds to the deflection angle of the light beam passing through the variable apex angle prism.

Corrects lateral chromatic aberration by causing it to occur in the second lens group,
At this time, lateral chromatic aberration Δ(ΔY) occurring in the second lens group
Assuming that 2 is the lateral chromatic aberration coefficient of the second lens group T2, Δ(ΔY) 2 CCT2tan (Δω), which is a value proportional to the angle of view, is generated.

In this example, the lateral chromatic aberration coefficient T2 of the second lens group is selected to be a positive value, that is, the second lens group corrects the lateral chromatic aberration so as to generate an undervalue, thereby reducing the lateral chromatic aberration generated in the variable apex prism. The entire system corrects eccentric lateral chromatic aberration in a well-balanced manner.

The principal ray of off-axis light also has a larger angle of incidence on the second lens group in the decentered state than in the reference state on the same side as the deflection direction.
The under magnification chromatic aberration generated in the second lens group becomes large. This corrects excessive chromatic aberration of magnification that occurs with the variable apex prism.

Additionally, in this example, the first lens group corrects chromatic aberrations such as excessive chromatic aberration of magnification, and the second lens group corrects chromatic aberrations such as under-occurring chromatic aberrations of magnification. It corrects lateral chromatic aberration in a well-balanced manner.

In a photographing system in which a variable apex angle prism is provided between two fixed lens groups as in this embodiment, the deflection ΔY of the image on the image plane due to the variable apex angle prism is such that the image of the first lens group is the variable apex angle prism. The beam is deflected by ΔY and then relayed by the second lens group at an imaging magnification β2. That is, Δy 1 =S-jan ((NP-1)
"ep)ΔY=(ΔYl)・β2=S−β2−jan((NP−1)・ep).

Here, S is the distance from the variable apex prism to the imaging plane of the first lens group. Similarly, the deflection ΔY' of the image at the second wavelength is ΔY'=S'β2' 4an ((NP' -]
)'gp) From this, eccentric lateral chromatic aberration Δ(ΔY)=Δ
The condition for Y"-ΔY to be 0 is S'β2'/(S・β2) = tan ((NP-1)"6p)/ja
n ((NP-1)6p)phantom(NP-])/(NP
'-1).

When the chromatic aberration of the first lens group is small, s'=s, so it can be approximated as β2'/β2phantom (NP-1)/(NP'-1). From now on, the imaging magnification of each wavelength of the second lens group may be designed to be inversely proportional to (NP 1) of each wavelength of the variable apex angle prism.

In this embodiment, when the first lens group is not afocal,
That is, when the focal lengths of the entire first lens group are respectively f, , f, and when lfIl<20f, the imaging magnifications β2 and β2
' is set so as to satisfy . . . -(3), thereby minimizing the occurrence of eccentric lateral chromatic aberration to the extent that it has no effect.

If the upper limit of conditional expression (3) is exceeded, eccentric chromatic aberration of magnification will be insufficiently corrected, and if the lower limit is exceeded, eccentric lateral chromatic aberration will be overcorrected, and eccentric lateral chromatic aberration will occur in the opposite direction to that when no correction is made. It's not good because it does.

Also, when the light beam exiting the first lens group is afocal, especially when lfI 1>2Of, if the focal length of the second lens group is f2, then ΔY=f2-tan ((NP-1)・6p)
It is expressed as Similarly, for the second wavelength, ΔY' =
It is expressed as f2'·tan ((NP' −1)·6P). From this, eccentric magnification chromatic aberration Δ(ΔY) = ΔY
The condition for '-ΔY to be 0 is f2 '/ f2 = jan ((NP-1)・εp) / jan
((NP-1)6p)Illusion(NP-i)/(NP
'-+).

The focal length of each wavelength of the second lens group may be set to be inversely proportional to (NP-1) of each wavelength of the variable apex angle prism. This also means that chromatic aberration of magnification is under-produced in the second lens group to correct eccentric chromatic aberration of magnification produced by the variable apex angle prism.

In this example, the focal length f2 of the reference wavelength of the second lens group and the focal length Mt2 of the second wavelength are set so as to satisfy the following conditional expressions, and the occurrence of eccentric chromatic aberration of magnification is reduced to 539. .

If the upper limit of conditional expression (4) is exceeded, the eccentric chromatic aberration of magnification is insufficiently corrected, and if the lower limit is exceeded, the eccentric chromatic aberration of magnification is overcorrected, and the eccentric chromatic aberration of magnification is moved in the opposite direction to that when no correction is made. It's not good because it happens.

In this example, if the imaging system is a photographic lens, it is preferable to select the d-line as the reference wavelength and the g-line as the second wavelength, but it is also possible to select light with a wavelength longer than the d-line as the second wavelength. good.

In other optical devices, it is preferable to select the reference wavelength as the dominant wavelength of the optical device, and select the second wavelength as light with the shortest wavelength used.

In this embodiment, the first. Although the second lens group is fixed with respect to decentering drive, it may include a lens group that moves in the optical axis direction, such as a focus lens group or a variable magnification lens group.

In this embodiment, in order to further correct the chromatic aberration of magnification, it is preferable to generate the chromatic aberration of magnification in the under direction in the second lens group, and for this purpose, the second lens group is configured as follows. It's good.

That is, the second lens group is divided from the object side into two lens groups, the 2A lens group and the 2B lens group, with the largest air gap in the lens groups as a boundary, and each lens constituting the 2B lens group is The refractive power is φ2Bi, and the Atsbe number of the material is 2B.
i, the equivalent Atsube number is V2B, and when V2B < 40...
...-(5) must be satisfied.

If conditional expression (5) is exceeded and the equivalent Abbe number V2B becomes large, the refractive power of the second B lens group must be increased, and as a result, coma and astigmatism will occur in large quantities. do not have.

In each of the above embodiments, the surfaces on both sides of the variable apex angle prism need not be completely flat, but may have a gentle curvature.

The photographing system in this embodiment can also be applied to optical equipment such as a shift lens and an auto level.

Next, numerical examples of the present invention will be shown. In numerical examples R
i is the radius of curvature of the i-th lens surface in order from the object side, D
i is the i-th lens thickness and air distance from the object side, Ni
and νi are the refractive index and Abbe number of the glass of the i-th lens, respectively, in order from the object side.

For comparative reference, various aberration diagrams when the variable apex angle prism of Numerical Example 1 is placed on the object side of the first lens group (Fig. 11) are shown in Fig. 12 (A) and (B). .

Numerical Example I F-: 100 FNo-l: 2.8 2ω
-8,25° Numerical Example 2 F-300FNo=1+2.8 2ω-8,25
゜Numerical Example 3! -300FNo-I: 2.8 2ω・8.25
(Effects of the Invention) According to the present invention, by configuring each lens group and the variable apex angle prism as described above, the problem that occurred when using the variable apex angle prism method without providing a special mechanism can be solved. The occurrence of eccentric lateral chromatic aberration can be corrected to a small extent,
It is possible to achieve a photographing system having an image deflecting means that can obtain a high-quality image with little color blurring and high contrast when eccentrically driven, and further corrects the lateral chromatic aberration of magnification to a small value in a reference state.

[Brief explanation of the drawing]

1st. Second. FIG. 3 shows numerical examples 1, 2, and 2 of the present invention, respectively.
3. Lens sectional view of No. 3, No. 4. Fifth. 6 is a numerical example of the present invention, various aberration diagrams in 1 and 2.3, FIG. 7 is an explanatory diagram of eccentric aberration coefficients in the present invention, and 8. FIG. 9 is an explanatory diagram of the lateral chromatic aberration coefficients in the present invention. Figure 10(A). (B) is an explanatory diagram of a conventional variable apex angle prism, No. 11. Figure 12 shows the first variable apex angle prism in Numerical Example 1.
FIG. 4 is a cross-sectional view of the lens and an aberration diagram when the lens group is placed on the object side. In the aberration diagram, (A) shows the object distance of 915 m, and (B) shows the lateral aberration when the image is deflected by ΔY = 1 mm. In the figure, ■ is the first lens group, ■! is the second lens group, P is a variable apex angle prism, ΔM is a meridional image surface, and ΔS is a sagittal image surface. 1 y Figure 2 I PII Y5 3 Figure 4 7 (A) 夷 5 Figure (A) F/2.8 1! , l:4. +2'
tJ: 4.12°, 4=4,129th
5 Figure (B) Figure 6 (A) F/2. Is (AJ: 4.12'
Q: 4. +2° ω: 4.128th
6 Kasumi ([13) Fig. 7 Fig. 8 Fig. 9 RO work ρ ■ No. 10 (2) (A) Bi r4 Fig. 11 Change to 7°'I SW within the variable term 12 Kasumi (A)

Claims (1)

[Scope of Claims] (1) In order from the object side, there is a fixed first lens group, a variable apex angle prism whose apex angle is variable, and a fixed second lens group, and the apex angle of the variable apex prism is In a photographing system having an image deflecting means that deflects a photographed image by changing the focal length of the entire system, the lateral chromatic aberration coefficient of the first lens group and the second lens group is δ
When NP=|N_P-N_P'|, -0.012<T_2-(δNP)/(N_P-1)<
0.012-1.3<T_1/T_2<-0.7 A photographing system having an image deflecting means is characterized in that it satisfies the following condition. (2) The focal length f_1 of the first lens group is |f_1|
When ≦20f, when the imaging magnifications of the second lens group for the reference wavelength and the second wavelength are β_2 and β_2′, respectively, 0.985<(β_2′)・(N_P′−1)/{(β
_2)·(N_P-1)}<1.015. An imaging system having an image deflecting means according to claim 1, wherein the image deflecting means satisfies the following condition. (3) The focal length f_1 of the first lens group is |f_1|
>20f, and when the focal lengths of the second lens group for the reference wavelength and the second wavelength are f_2 and f_2', respectively, 0.985<(f_2')・(N_P'-1)/{(f
_2)·(N_P-1)}<1.015. An imaging system having an image deflecting means according to claim 1, wherein the image deflecting means satisfies the following condition. (4) The second lens group is divided from the object side into two lens groups, a 2A lens group and a 2B lens group, with the largest air gap among the lens groups as a boundary, and each lens group constituting the 2B lens group The refractive power of the lens is φ2Bi, and the Abbe number of the material is ν.
2Bi, the equivalent Abbe number is V2B, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ The image according to claim 2 or 3, which satisfies the condition that V2B<40 Photographing system with deflection means.