JP3021985B2 - Anamorphic converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anamorphic converter, and more particularly to a anamorphic converter which is removably mounted on an image plane side of a main photographic system (master lens) to record and / or record images with various aspect ratios of a photographic screen. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anamorphic converter suitable for a video camera, a photographic camera, or the like that projects an image with various aspect ratios.

[0002]

2. Description of the Related Art Conventionally, there is a converter which is detachably mounted on the front (object side) or rear side (image side) of a main photographing system so as to record an image while changing the aspect ratio (aspect ratio) of a photographing screen. Various proposals have been made.

[0003] In recent years, in the field of video cameras, an image having a normal aspect ratio of 3: 4 has been widened by using a converter so as to have an aspect ratio of 9:16 using a converter so that a recorded image can be viewed. The system is used.

As a method of appreciating an image with an aspect ratio of 9:16, there is a method of using a converter that has an aspect ratio of 9:16 when observing an image photographed by a camera having an aspect ratio of 3: 4, and an aspect ratio at the time of photographing and appreciating. There is a method using an optical member having a ratio of 9:16.

In Japanese Patent Application Laid-Open No. Hei 2-13916, an aspect ratio of 3: 4 to 9: A conversion lens has been proposed in which the image is converted to 16 to obtain a horizontally long image.

In this publication, an afocal converter composed of a cylindrical lens is used as a conversion lens. The afocal converter is attached to the front of the camera so that the direction of curvature of the afocal converter is aligned with the horizontal direction of the screen. At the time of reproduction, the horizontal direction is 1.33.
It has doubled. As a result, an image converted from an aspect ratio of 3: 4 to an aspect ratio of 9:16 is obtained.

[0007] In addition, as shown in FIG. 9, a converter A comprising a cylindrical lens having a refractive power in the vertical direction behind (image surface side) the main photographing system (master lens) ML.
C is attached. FIG. 9A is a horizontal direction, and FIG.
Indicates the vertical direction. In the figure, the captured image is recorded at 1.33 times in the vertical direction and recorded, and at the time of reproduction, it is 1.33 times in the vertical direction using a converter. As a result, an image converted from an aspect ratio of 3: 4 to an aspect ratio of 9:16 is obtained.

[0008]

Problems to be Solved by the Invention
In the method proposed in Japanese Patent Application Laid-Open Publication No. H10-157, (1-a) there is a problem that the entire lens system becomes large because an anamorphic converter is mounted in front of the main photographing system.

(1-b) A focusing mechanism is required in the anamorphic converter, which increases the size of the entire apparatus and makes focusing operation difficult.

For example, when the anamorphic converter is mounted on a video camera having an auto focus (AF) function, the anamorphic converter must be manually focused unless a focusing unit for the main photographing system and a special interlocking mechanism are provided.

In addition, since blurring occurs only in the horizontal direction with an anamorphic lens, when combined with a TV signal autofocus mechanism, the autofocus mechanism is a method of detecting blur only in the horizontal direction (scanning line direction). There is a problem that the autofocus mechanism cannot distinguish whether the blur is caused by the anamorphic converter or the blur caused by the blur.

Further, the method shown in FIG. 9 has a problem that the converter cannot be applied unless the main photographing system has a sufficient back focus since the converter is mounted on the image plane side of the main photographing system.

According to the present invention, by appropriately setting the lens configuration, even a main photographing system (master lens) having a relatively short back focus can be easily and detachably mounted on the image plane side thereof. While miniaturizing the entire device,
Recording with arbitrary changes in the horizontal and vertical imaging magnifications,
An object of the present invention is to provide an anamorphic converter which can easily obtain an image having a desired aspect ratio and does not require a focusing mechanism.

[0014]

An anamorphic converter according to the present invention is an anamorphic converter which is mounted on an image plane side of a main photographing system and changes an aspect ratio of a photographing screen. The anamorphic converter uses the anamorphic converter as a reference based on the photographing screen. Has a positive refractive power in the horizontal direction, has a negative refractive power in the vertical direction, and has a positive refractive power in the horizontal direction and a first group of negative refractive power both in the horizontal and vertical directions in order from the object side. And a second group of negative refractive power in the vertical direction, and the horizontal and vertical focal lengths of the first group are f _1x and f _1y , respectively, and the horizontal and vertical directions of the second group are F _2x and f _2y
And when

(Equation 2) It is characterized by satisfying certain conditions.

[0015]

1 and 2 show numerical embodiments 1 and 2, respectively, of the present invention.
It is a lens sectional view of. 1 and 2, (A) shows a horizontal cross section (cross section in the horizontal direction) and (B) shows a vertical cross section (cross section in the vertical direction) based on the photographing screen. FIG. 3 is a lens cross-sectional view at the wide angle end of a main imaging system (master lens) ML to which the anamorphic converter AC of the present invention is attached.

Anamorphic converter A of the present embodiment
C has two lens groups, a first group L1 and a second group L2,
As a whole, it has a positive refractive power in the horizontal direction and a negative refractive power in the vertical direction. G in the figure is a glass block such as a face plate and a filter.

The first lens unit L1 has a negative refractive power in both the horizontal and vertical directions, and the second lens unit L2 has a positive refractive power in the horizontal direction and a negative refractive power in the vertical direction. are doing.

In this embodiment, the first unit is of a so-called retrofocus type having a negative refractive power and the second unit having a positive refractive power in order to lower the imaging magnification in the horizontal direction and to ensure a sufficient back focus. . In the vertical direction, both the first and second units have weak negative refractive power in order to secure sufficient back focus while increasing the imaging magnification.

In the first numerical embodiment shown in FIG. 1, the first lens unit L1 and the second lens unit
Each of the lenses constituting the group L2 is constituted by a toric lens (a lens having a lens surface having a different refractive power (curvature) between the horizontal direction and the vertical direction).

In the numerical embodiment 2 shown in FIG. 2, the first unit L1 comprises a spherical lens and a toric lens, and the second unit L2 comprises a toric lens.

It is preferable that the anamorphic converter be constructed so as to form an image at the same magnification in the horizontal direction. However, in order to do so, it is necessary to use an afocal system in the horizontal direction. It is becoming.

Therefore, in this embodiment, in order to obtain a lens configuration that is as close as possible to the same-magnification image and has a sufficiently long back focus, the lens has a positive refractive power as a whole in the horizontal direction. The vertical direction has a negative refractive power so that the focal length is 1.33 times the horizontal direction.

In this embodiment, when the anamorphic converter AC is mounted on the image plane side of the main photographing system ML, the horizontal imaging magnification βH is 1.92 times and the vertical imaging magnification βV
Are formed to be 1.44 times larger.

At this time, the ratio between the horizontal and vertical imaging magnifications βH and βV is βV / βH = 0.75.
As a result, image compression in the horizontal direction is performed, and the aspect ratio is 3:
The magnification is changed from 4 to an aspect ratio of 9:16 to obtain a horizontally long image.

In the present invention, it is necessary to secure a predetermined back focus when mounted on the image plane side of the main photographing system and to change the horizontal and vertical image forming magnifications while maintaining good optical performance. The anamorphic converter has a first group of negative refractive power in the horizontal and vertical directions and a second group of positive refractive power in the horizontal direction and negative refractive power in the vertical direction in order from the object side.
When the first group has horizontal and vertical focal lengths of f _1x and f _1y , respectively, and the second group has horizontal and vertical focal lengths of f _2x and f _2y , respectively.

It is preferable that the above-mentioned conditional expressions (1) and (2) are satisfied.

Conditional expression (1) relates to the ratio of the refractive power of the first and second units in the horizontal direction, and conditional expression (2) relates to the ratio of the refractive power of the first and second units in the vertical direction. This is mainly for ensuring a predetermined back focus while reducing the size of the entire lens system.

If the negative refractive power of the first lens unit in the horizontal direction exceeds the upper limit value of the conditional expression (1) and becomes too weak as compared with the positive refractive power of the second lens unit in the horizontal direction, a predetermined back focus is obtained. It becomes difficult.

If the negative refractive power of the first lens unit in the horizontal direction exceeds the lower limit and becomes too strong as compared with the positive refractive power of the second lens unit in the horizontal direction, the back focus is sufficiently ensured, but the second lens unit is not moved. The spread of the luminous flux from one group becomes large, and the entire lens system becomes large. Also, the telecentricity on the image plane side is lost, which is not good.

If the negative refractive power of the first lens unit in the vertical direction exceeds the upper limit of conditional expression (2) and becomes too weak in comparison with the negative refractive power of the second lens unit in the vertical direction, a predetermined back focus is secured. It becomes difficult to do.

If the negative refractive power of the first lens unit in the vertical direction exceeds the lower limit value of the conditional expression (2), on the contrary, the first lens unit becomes too strong in comparison with the negative refractive power of the second unit in the vertical direction. This is not good because the spread of the light beam from the group becomes large and the entire lens system becomes large.

In the present embodiment, as a lens having a different refractive power between the horizontal direction and the vertical direction, a toric lens having different curvatures in two orthogonal directions can be applied in addition to a cylindrical lens. A combination of a spherical lens and a toric lens, a combination of a spherical lens and a cylindrical lens, or the like can be applied as the first and second groups having different refractive powers in the horizontal direction and the vertical direction.

In the present invention, in order to maintain good optical performance when the anamorphic converter is mounted on the main photographing system, the first group has a negative lens, a positive lens, and a negative lens in both the horizontal and vertical directions. The two groups have a positive lens and a positive lens in the horizontal direction, and a positive lens and a negative lens in the vertical direction.

Next, numerical examples in the horizontal and vertical directions when the anamorphic converter of the present invention is mounted on a main photographing system (zoom lens) will be described.

In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, and Di is the i-th lens surface from the object side.
The second lens thickness, the air gap, and Ni and νi are the refractive index and Abbe number of the glass of the ith lens in order from the object side.

R1 to R28 are main photographing systems (all are composed of spherical lenses), and R29 to R38 are anamorphic converters. R39 and R40 are glass blocks such as a face plate and a filter.

Main photographing system F = 1 to 14.25 FNO = 1: 1.45 to 2.15 2ω = 54.2 ° to 4.2 ° R 1 = 17.394 D 1 = 0.361 N 1 = 1.80518 ν 1 = 25.4 R 2 = 7.157 D 2 = 1.325 N 2 = 1.60311 ν 2 = 60.7 R 3 = -25.937 D 3 = 0.024 R 4 = 6.813 D 4 = 0.674 N 3 = 1.63854 ν 3 = 55.4 R 5 = 21.918 D 5 = Variable R 6 = 14.264 D 6 = 0.156 N 4 = 1.83400 ν 4 = 37.2 R 7 = 2.089 D 7 = 0.580 R 8 = -2.457 D 8 = 0.132 N 5 = 1.71300 ν 5 = 53.8 R 9 = 2.458 D 9 = 0.481 N 6 = 1.84666 ν 6 = 23.9 R10 =- 19.947 D10 = Variable R11 = -4.989 D11 = 0.156 N 7 = 1.72000 ν 7 = 50.3 R12 = 4.991 D12 = 0.313 N 8 = 1.80518 ν 8 = 25.4 R13 = 73.111 D13 = Variable R14 = 317.376 D14 = 0.530 N 9 = 1.60311 ν 9 = 60.7 R15 = -3.402 D15 = Variable R16 = (Aperture) D16 = 0.241 R17 = 4.202 D17 = 0.638 N10 = 1.60311 ν10 = 60.7 R18 = -9.339 D18 = 0.181 R19 = -4.013 D19 = 0.180 N11 = 1.84666 ν11 = 23.9 R20 = 43.043 D20 = 0.018 R21 = 3.321 D21 = 0.650 N12 = 1.60311 ν12 = 60.7 R22 = -20.502 D22 = 2.289 R23 = -46.664 D23 = 0.108 N13 = 1.83400 ν13 = 37.2 R24 = 1.975 D24 = 0.136 R25 = 7.694 D25 = 0.265 N14 = 1.60311 ν14 = 60.7 R26 = -3.830 D26 = 0.0 18 R27 = 1.991 D27 = 0.421 N15 = 1.54814 ν15 = 45.8 R28 = -14.556

[0038]

【table 1】 Anamorphic converter Numerical example 1 Synthetic focal length Horizontal direction: 1.4 to 20.7 Vertical direction 1.9 to 27.4 (Horizontal direction) (Vertical direction) D28 = 0.45 * R29 = 64.878 R29 = -14.235 D29 = 0.11 N16 = 1.60311 ν16 = 60.7 * R30 = 1.307 R30 = 0.811 D30 = 0.24 * R31 = -2.275 R31 = 1.600 D31 = 0.36 N17 = 1.59270 ν17 = 35.3 * R32 = -1.123 R32 = -1.214 D32 = 0.12 * R33 = -1.055 R33 = -1.551 D33 = 0.24 N18 = 1.80610 ν18 = 41.0 * R34 = -8.901 R34 = -3.711 D34 = 0.11 * R35 = 64.688 R35 = -1.218 D35 = 0.45 N19 = 1.51633 ν19 = 64.2 * R36 = -2.181 R36 = -0.944 D36 = 0.02 * R37 = 3.232 R37 = -1.996 D37 = 0.36 N20 = 1.71300 ν20 = 53.8 * R38 = -4.153 R38 = -8.002 D38 = 0.48 R39 = ∞ D39 = 0.72 N21 = 1.51633 ν21 = 64.2 R40 = ∞ * Toric surface | f _1x / f _2x | = 0.66 | f _1y / f _2y | = 1.17 Numerical example 2 Synthetic focal length Horizontal direction: 1.4 to 20.7 Vertical direction 1.9 to 27.4 (Horizontal direction) (Vertical direction) R29 = -25.503 D29 = 0.11 N16 = 1.60311 ν16 = 60.7 R30 = 0.801 D30 = 0.24 * R31 = 3.551 R31 = 1.688 D31 = 0.36 N17 = 1.59270 ν17 = 35.3 * R32 = -2.751 R32 = -1.212 D32 = 0.12 R33 = -1.574 D33 = 0.24 N18 = 1.80610 ν18 = 41.0 R34 = -3.390 D34 = 0.11 * R35 = -62.680 R35 =- 1.132 D35 = 0.45 N19 = 1.51633 ν19 = 64.2 * R36 = -1.098 R36 = -0.923 D36 = 0.02 * R37 = -168.812 R37 = -1.988 D37 = 0.36 N20 = 1.71300 ν20 = 53.8 * R38 = 99.891 R38 = -8.101 D38 = R39 = ∞ D39 = 0.72 N21 = 1.51633 ν21 = 64.2 R40 = ∞ * Toric surface | f _1x / f _2x | = 0.71 | f _1y / f _2y | = 1.85

[0039]

As described above, according to the present invention, as described above, by appropriately setting the lens configuration, even if the main photographing system (master lens) has a relatively short back focus, its image plane side It can be easily and detachably attached to the camera, recording while changing the horizontal and vertical imaging magnifications arbitrarily while reducing the size of the entire device, and an image having a desired aspect ratio can be easily obtained. Moreover, an anamorphic converter that does not require a focusing mechanism can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 3 is a lens sectional view of a main photographing system to which the anamorphic converter of the present invention is attached.

FIG. 4 is an aberration diagram in a horizontal direction and a vertical direction at a wide-angle end when the anamorphic converter according to Numerical Example 1 of the present invention is mounted on a main imaging system.

FIG. 5 is an aberration diagram in a horizontal direction and a vertical direction at a telephoto end when the anamorphic converter according to Numerical Example 1 of the present invention is mounted on a main photographing system.

FIG. 6 is an aberration diagram in a horizontal direction and a vertical direction at a wide-angle end when an anamorphic converter according to Numerical Example 2 of the present invention is mounted on a main imaging system.

FIG. 7 is a diagram showing aberrations in the horizontal and vertical directions at the telephoto end when the anamorphic converter according to Numerical Example 2 of the present invention is attached to the main photographing system.

8 is an aberration diagram of the main photographing system in FIG.

FIG. 9 is an explanatory view when an anamorphic lens is attached to the image plane side of a conventional main photographing system.

[Explanation of symbols]

 AC anamorphic converter L1 First group L2 Second group G Glass block ML Main imaging system d d-line g g-line ΔS Sagittal image plane ΔM Meridional image plane

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (3)

(57) [Claims] 1. An anamorphic converter mounted on an image plane side of a main photographing system and changing an aspect ratio of a photographing screen, wherein the anamorphic converter has a positive refractive power in a horizontal direction with respect to the photographing screen. Has a negative refractive power in the vertical direction , and in the horizontal and vertical directions from the object side
First group of negative refractive power in both directions and positive refraction in horizontal direction
Force, having a second group of negative refractive power in the vertical direction,
The horizontal and vertical focal lengths are respectively f _1x and f _1y ,
Let the horizontal and vertical focal lengths of the two groups be f _2x and f _2y respectively.
And [Equation 1] Features and be a luer Namo Scientific converter that satisfies the following condition. Wherein <br/> anamorphic converter of claim 1, wherein the anamorphic converter has a toric lens. 3. anamorphic converter of claim 1, wherein the anamorphic converter has a toric lens and a spherical lens.