JP2780461B2 - Imaging device having trimming imaging mechanism - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographing apparatus having a trimming photographing mechanism. (1st mode) and trimming shooting (second mode for a shooting range narrower than the shooting range of the first mode) in images having at least two modes. The present invention relates to a photographing apparatus having a trimming photographing mechanism having a simple configuration with an F-number of 3 or less and a large aperture ratio that can easily obtain the same.

(Prior Art) Conventionally, one of a normal photographing mode and a trimming photographing mode is switched by a switching mechanism, and the photographing mode and the range to be trimmed at this time are recognized both from outside the camera and within the viewfinder field of view. A photographing apparatus having a trimming photographing mechanism for photographing has been proposed in, for example, JP-A-62-52541.

Further, Japanese Patent Application Laid-Open No. 54-26721 proposes a photographic device (camera) capable of writing so-called trimming information for recording image information indicating a stretch range set at the time of photographing on a film.

In general, a photographing lens such as a photographic camera and a video camera is aberration-corrected so as to obtain a well-balanced optical performance over the entire screen.

As a tendency of aberration correction in a normal photographing lens, the best image plane position showing the curvature of field falls in the direction of undercorrection (minus) from the center (optical axis) of the photographing range toward the periphery of the screen, and then overcorrection ( It is designed so that it returns to the (plus) side and is located on the slightly overcorrected (plus) side at the periphery of the screen.

As a result, an image of good image quality that is balanced over the entire screen is obtained. Then, when a normal entire screen is stretched, a good image (photograph) with almost no concern about deterioration in image quality is obtained.

(Problems to be Solved by the Invention) Trimming is performed on an image photographed using this kind of photographing lens, and an image in a photographing range (trimming range) narrower than a normal photographing range is targeted. May be stretched and burned.

At this time, among the images in the trimming range, the best image plane position is greatly inclined to the minus side in the most peripheral part of the screen,
The optical performance at the peripheral portion of the screen is greatly reduced as compared with the central portion. For this reason, there is a problem that the balance of the image quality of the entire trimming screen is greatly lost.

That is, when an image is obtained by extending a trimming range in which the aberration correction is insufficiently corrected over the entire screen, the image quality is significantly deteriorated, resulting in a very unsightly image (photograph).

The present invention solves the above-mentioned problems by appropriately setting the lens configuration of the photographing lens and adjusting the lens group interval between the two lens groups constituting the photographing lens at the time of trimming photographing. In addition, a good image (photograph) can be obtained in any of the trimming shootings when performing various shootings in a range narrower than the shooting range in the normal shooting, and a trimming shooting mechanism having an F number of 3 or less and a large aperture ratio. It is an object of the present invention to provide an imaging device having

(Means for Solving the Problems) A photographing apparatus having a trimming photographing mechanism according to the present invention includes: a first mode in which a first photographing range is set and photographed among photographing ranges photographed by a photographing optical system; And at least two modes of a second mode for setting and photographing a second photographing range smaller than the first photographing range,
The photographing optical system includes two lens groups of a first lens group and a second lens group in this order from the object side. The first lens group includes a positive lens having a positive refractive power and a negative lens having a negative refractive power.
The second lens group includes a cemented lens in which a positive lens having a positive refractive power and a negative lens having a negative refractive power are bonded to each other. When switching between the first and second lens groups, the distance between the first lens group and the second lens group is relatively changed, and the first lens group and the photographing optical system in the first mode are changed. When the focal lengths are f1 and fA, respectively, | f1 / fA | ≧ 2 (1) is satisfied.

(Example) FIG. 1 is a lens cross-sectional view of Numerical Example 1 of a photographic lens according to the present invention, which will be described later.

In FIG. 1, reference numeral 10 denotes a photographing optical system (also referred to as a photographing lens), which is a positive lens 1 having a positive refractive power in order from the object side.
And a negative lens 2 having a negative refractive power.
It comprises a total of four lenses, a lens group A and a second lens group B comprising a cemented lens in which a positive lens 3 having a positive refractive power and a negative lens 4 having a negative refractive power are laminated. 5
Denotes a stop, which is disposed behind the second lens unit B.
Reference numeral 6 denotes a film, which is arranged on the image plane.

FIG. 2 is a diagram of various aberrations during normal photographing (first mode) of the photographing lens of FIG.

In this embodiment, the aberration correction of the photographing lens 10 at the time of the normal photographing is balanced over the entire effective screen of the film 6 (photographing angle of view 2ω = 62 °) as shown in the aberration diagram of FIG. It is well corrected.

As a result, a good image (photograph) that is well-balanced over the entire effective screen area of the film 6 during normal shooting is obtained.

Next, in the second mode, which targets a shooting range a narrower than the first mode, that is, when shooting is performed by specifying a trimming range a (shooting view angle 2ω = 33.4 °) as shown in FIG.
It is assumed that switching to the trimming shooting is performed in the state of the aberration correction shown in FIG.

At this time, the outermost peripheral portion of the screen in the trimming range a (ω = 16.7
As shown in FIG. 2, the field curvature in ゜) is in the state of the least correction (corresponding to the arrangement at the most protruding part of the aberration curve).

For this reason, if the narrow trimming range a is stretched to the same size as the normal photographing range and printed by automatic developing and printing, an image (photograph) with extremely deteriorated image quality results. Therefore, in this embodiment, (a) in general, the target shooting angle of view is different from that of normal shooting during trimming shooting, and it is not necessary to consider aberration correction over the entire angle of view. Things to consider.

(B) Further, in consideration of the enlargement magnification within this trimming photographing range, it is desirable to perform aberration correction better than at the time of normal photographing.

In consideration of the above points, when performing trimming photographing, the distance between the first lens group A and the second lens group B constituting the photographing optical system 10 is relatively changed, for example, by widening. (In the present embodiment, the distance between the first and second lens groups A and B before and after the change of the lens group interval (at the time of normal shooting) and after (at the time of trimming shooting) is changed as shown in Numerical Example 1 described later. (It is expanded from 1.47 to 2.0 and 0.53), so that aberration correction is performed in the best balance within the trimming shooting range. This gives an image (photograph) of good image quality within the trimming shooting range
Have gained.

FIG. 3 is an aberration diagram showing a state in which various aberrations are corrected for the inside of the trimming shooting range at the time of trimming shooting at this time.

As shown in FIG. 2, at the same angle of view (half angle of view ω = 31 °) at the outermost periphery of the screen as in the normal shooting shown in FIG.
The field curvature (the average value of the meridional image plane M and the sagittal image plane S) is largely overcorrected. In this state, for example, it is assumed that the photographing screen is trimmed to half (area ratio 1/4) and the photographing view angle is set to ω = 16.7 °. Then, the outermost part of the screen at the time of trimming shooting (ω = 16.7
The field curvature of ゜) is for normal shooting (half angle of view ω = 31 °)
Better than. Also, each of the distortion and the chromatic aberration of magnification is better as shown in FIG.

Among them, especially the chromatic aberration of magnification is exaggerated by the trimming similarly to the curvature of field, but since the aberration is more properly corrected in the trimming range than in the range at the time of normal shooting, it is good even when the screen is greatly extended. Image quality is obtained.

In this embodiment, in order to prevent the focus from shifting when the distance between the first lens unit A and the second lens unit B is changed, the light beam emitted from the first lens unit A is substantially afocal light. It is desirable to configure a photographing optical system.

Further, in this embodiment, in order to obtain an image of good image quality during trimming photographing, when the focal length f1 of the first lens unit A and the focal length of the photographing optical system during normal photographing are fA | f1 / fA | ≧ 2 It is preferable to satisfy the following condition.

Conditional expression (1) relates to the ratio of the focal length of the first lens unit A to the focal length of the photographing optical system during normal photographing. When trimming photographing is performed by enlarging the lens group interval, the fluctuation of spherical aberration increases, and the amount of change in back focus also increases, which is not good.

In the present embodiment, if the amount of change in the back focus is sufficiently small, it is possible to move only the first lens unit A with respect to the film surface (imaging surface) and change the lens unit interval during trimming photographing. Various aberrations can be corrected with good balance within the trimming photographing range. According to this, the mechanism can be greatly simplified.

Thus, in the present embodiment, as described above, 4
The photographing optical system is composed of two lenses, and during trimming photographing, the most preferable aberration correction is performed within the trimming photographing range by relatively changing the lens group interval between the first lens group A and the second lens group B. As a result, a pseudo telephoto effect by trimming shooting can be obtained with excellent performance at very low cost, and an image pickup apparatus having a trimming shooting mechanism with a large aperture ratio of F number 3 or less has been achieved.

Next, control for performing trimming photographing in this embodiment will be described with reference to the block diagram of FIG.

In the figure, reference numeral 41 denotes a trimming range setting member which allows a photographer to set and operate a plurality of trimming shooting ranges. The trimming shooting range in a finder formed of, for example, a liquid crystal or the like changes in accordance with the operation of the setting member 41. .

The determined trimming photographing range is converted into an electric signal, and the information is stored in the storage device 42. Then, the trimming information recording device 43 prints on the film 6 using optical means based on the information stored in the storage device 42 based on a predetermined standard.

Further, before photographing, the control circuit 44 performs aberration correction in the trimming photographing range based on the information on the trimming photographing range stored in the storage device 42. That is, the first lens unit A is moved in the direction in which the distance between the two lens units A and B increases as indicated by the arrow shown in FIG. In this way, control for performing trimming photographing is performed.

The first lens group A can be moved in conjunction with the trimming range setting member 41.

In addition, FIG. 3 shows a case where only the first lens group A is moved as an aberration correction within the trimming range when performing the trimming photographing.
Alternatively, the first lens group A and the second lens group B may be moved together to change the distance between the lens groups, for example, to increase the distance.

The aperture 5 may be moved integrally with any one of the first lens group A and the second lens group B, or may be independently formed. Also, as the diaphragm, either a middle diaphragm type disposed between the two lens groups A and B, or a diaphragm type disposed behind the second lens group B as shown in the first embodiment may be employed. good.

In this embodiment, the cemented lenses forming the second lens group are a positive lens and a negative lens in this order from the object side.

FIG. 5 is a lens sectional view of a numerical example 2 of the taking lens according to the present invention, which will be described later.

FIG. 6 is a diagram showing various aberrations of the photographing lens of the present invention in a numerical example 2 at the time of normal photographing, and FIG.

Also in this embodiment, the first lens unit A and the second lens unit B are used at the time of trimming photographing as in the first embodiment.
By changing the distance between the lens groups in the direction in which they are relatively widened, various aberrations such as curvature of field are corrected in a well-balanced manner within the trimming range. Can be.

In each embodiment, during normal shooting (first mode)
And the two modes of trimming shooting (second mode) have been described. However, the image forming range (shooting range) is smaller than that of the second mode. May be specified.

In the above embodiment, an example in which a single lens is used is described. However, the imaging optical system may be configured with a zoom lens. If the distance between the first lens group A and the second lens group B is relatively appropriately changed, favorable trimming photography can be performed as described above.

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

(Effects of the Invention) According to the present invention, in the photographing optical system, the distance between the two lens groups of the first lens group and the second lens group, each of which includes a predetermined lens, is relatively changed during trimming photographing. It is possible to perform well-balanced correction of various aberrations within the trimming shooting range, for example, various aberrations such as curvature of field, to obtain a high quality image over the entire screen. An imaging device having a ratio trimming imaging mechanism can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 5 each show a numerical example of a photographing lens according to the present invention.
1 and 2 are cross-sectional views of lenses, and FIGS. 2 and 6 are various aberration diagrams during normal photographing of Numerical Examples 1 and 2 of the photographing lens according to the present invention.
3, FIG. 7 shows a numerical example 1 of the taking lens according to the present invention,
FIG. 4 is a diagram of various aberrations during trimming shooting, and FIG. 4 is a block diagram when performing trimming shooting according to the present invention. In the figure, A is the first lens group, B is the second lens group, 10 is a photographing optical system, 1, 3 is a positive lens, 2, 4 is a negative lens, 5 is an aperture, 6
Is a film.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03B 17/12 G02B 15/15

Claims (1)

(57) [Claims] 1. A first mode for setting and photographing a first photographing range among photographing ranges photographed by a photographing optical system and a second photographing range smaller than the first photographing range. The imaging optical system includes at least two modes of a first lens group and a second lens group in order from the object side, and the first lens group Is composed of two lenses, a positive lens having a positive refractive power and a negative lens having a negative refractive power, and the second lens group is formed by bonding a positive lens having a positive refractive power and a negative lens having a negative refractive power. When switching between the first mode and the second mode, the distance between the first lens group and the second lens group is relatively changed. One lens group and the focus of the photographing optical system in the first mode. Distance each f1, fA and the time | f1 / fA | had trimming photographing mechanism which satisfies the ≧ 2 condition: photographing apparatus.