JPH07253536A - Television image photographic device - Google Patents

Abstract

PURPOSE:To provide the excellent quality of picture whose aberrations including distortion aberration and the curvature of field are compensated while ensuring a working space for wiping out dust stuck to a monitor due to static electricity and a space for arranging a rotating filter in an optical path by composing the device of four lens groups of negative, positive, negative and positive lenses. CONSTITUTION:This device is composed, in order from the object side, of a first lens group composed of a negative meniscus lens whose convex surface confronts the object side, a second lens group composed of a positive lens whose curvature of a surface on the object side is larger than the curvature of a surface on the image side, a third lens group composed of biconcave lens, a fourth lens group whose curvature of a surface on the object side is smaller than the curvature of a surface on the image side and a brightness diaphragm arranged between the second lens group and the third lens group. When the device is utilized for the image photographic device of a monitoring television, by representing a distance from a display means to a projection optical system by L, the distance L satisfies the condition: (1) 1.5f<L<3f, where (f) is the focal distance of the whole optical system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system and an apparatus for recording information displayed on a television monitor on a film.

[0002]

2. Description of the Related Art In recent years, an endoscope system for displaying the inside of a body cavity or the like on a monitor TV or the like for observation has become widespread. Such a system allows a large number of people to observe an object at the same time, and by using image processing technology, it is possible to display only specific information of information included in an object image by making it stand out or erased. Since it can be used, it can be conveniently used for diagnosing a living body and various inspections, and its application may be further expanded in the future.

In such an endoscope television system, an image recording device for use in a conference presentation or the like is indispensable.

This image recording apparatus has, for example, a configuration as shown in FIG. In this figure, an endoscopic image is displayed on the color television monitor 15 by a television signal TV output from an endoscope system (not shown).
The image on the color television monitor 15 is used as an object and is formed on the color film 17 by the imaging lens 16. The image recording apparatus shown in this FIG.
Is separable from the main body 1, and the imaging lens 16 and the camera 18 are also separable. This camera 18 is prepared in two types for 16 mm and 35 mm depending on the film size. An opening / closing device 4 is attached to the side surface of the main body 1, and the opening / closing device 4 is opened to perform CR.
It has a structure that can wipe off dust and the like adhering to T15.

When a color monitor is used as a television monitor in the above-mentioned endoscope imaging apparatus, the size of the main body cannot be reduced due to the large size of the monitor, and the color monitor is used, resulting in high cost. Have Therefore, recently, a black and white television monitor 2 is used as a television monitor as shown in FIG. 23 (A), and red, green, and blue three-color filters 18, 19 are provided in a photographing optical path as shown in FIG. 23 (B). , 20 and a viewing color glass 21 are arranged, and a black-and-white image corresponding to each color is sequentially synchronized with the color filters 18, 19 and 20 to perform multiple photographing (hereinafter referred to as CIR method). Is becoming.

In the case of the apparatus shown in FIG. 23A, a lens system having a relatively long back focus is required as the taking lens 16 in order to use a normal 35 mm single lens reflex camera body for the camera. Therefore, the paraxial structure of the taking lens needs to be a retrofocus type lens system as shown in FIG.

There are various modifications to the retrofocus type. For example, as shown in FIG. 25, the front group of negative power is composed of two lenses, a positive lens and a negative lens, and the rear group of positive power is used. There is known a lens system of a type that includes a positive lens, a negative lens, a positive lens, and a positive lens. In a retrofocus type lens system having such a configuration,
When the lens closest to the object side is a positive lens, the entrance pupil is separated from the first surface of the lens system and the angle of view is narrowed. CI as described above
Since the object is a television monitor in the monitor photographing apparatus adopting the R method, when the height of the object is constant and the angle of view of the photographing lens is narrow, as shown in FIG.
The diameters of the rotary color filters 18, 19 and 20 must be made larger than those of the lens system having a wide angle of view shown in FIG.
Specifically, in the case of the lens system as shown in FIG. 25, the ray height h at the position 6 of the rotating color filter is h = 43.6.
In order to prevent the vignetting by the color filter, the color filter must be 43.7 or more. If the rotation color filter is composed of a square color filter having a diagonal length of 43.7,
As shown in FIG. 26A, the rotary color filter has a diameter of 192 or more. If the diameter of the rotary color filter becomes large as described above, the size of the entire apparatus becomes large, and a large torque is applied to the monitor for rotating the filter, and the motor becomes large, which is not preferable in terms of noise and durability.

For the above reasons, it is necessary to use the retrofocus type lens system in which the negative lens is preceded as the taking lens 16 to make the angle as wide as possible. Further, it is necessary to satisfactorily correct distortion.

On the other hand, as a conventional example of a lens system having a negative, positive, negative, positive paraxial structure, Japanese Patent Laid-Open No. 60-37514 discloses a first example.
Although there is a lens system shown as an example, it is not a lens system for a monitor photographing device but a camera lens.

[0010]

FIG. 29 shows the aberrations of the above conventional optical system during macro photography.
In other words, this aberration diagram shows that the focal length f of this optical system is 100 mm.
Distance from the first surface of the lens system to the object when normalized to
Is when L = 2.3f.

This conventional optical system is used as an ordinary camera lens. Therefore, in a region where the object point distance is about 100 times the focal length, the aberration condition is very good, but the object point distance is the focal point. In a macro shooting area of about 2 to 3 times the distance, the performance is extremely deteriorated as can be seen from FIG. 29, and therefore cannot be used as an optical system for a monitor shooting apparatus. The reason is that this optical system has β ₁ = 0.3 when the magnifications of the first, second, third, and fourth lens groups during macro photography are β ₁ , β ₂ , β ₃ , and β ₄ , respectively. ,
β ₂ = −2.7, β ₃ = −0.3, β ₄ = −2.4,
The fourth lens group has a large magnification, and aberration occurs in this lens group. That is, spherical aberration and coma are largely generated in the first lens group and the second lens group, and are large in the third lens group and the fourth lens group.
It does not occur much with the lens group. Astigmatism occurs in the first lens group and the second lens group, occurs in the opposite direction in the third lens group, and occurs again in the fourth lens group. However, when the F-number is the same and the back focus is almost the same, and the magnification of the fourth lens group is large, the light beam is sharply bent in the fourth lens group as shown in FIG. ), Spherical aberration and coma, which should not occur much, occur in the fourth lens group.

The present invention is a retrofocus type optical system in which the angle of view is as wide as possible with respect to the focal length, and a working space and a space for arranging a rotary filter in the optical path are secured to wipe off dust adhering to the monitor due to static electricity. At the same time, it is an object of the present invention to provide an optical system for a CIR-type monitor image-taking apparatus with good image quality in which various aberrations including distortion and field curvature are corrected.

[0013]

A projection optical system for a monitor photographing apparatus according to the present invention comprises, in order from the object side, a first lens group consisting of a negative meniscus lens having a convex surface directed toward the object side;
The second lens group consisting of a positive lens whose object-side surface has a curvature larger than that of the image-side surface, the third lens group consisting of biconcave lenses, and the object-side surface whose curvature is smaller than that of the image-side surface. A fourth lens group including a positive lens, a second lens group, and a third lens group.
The optical system includes an aperture stop arranged between lens groups.

The projection optical system of the present invention is used in the image taking apparatus of the present invention for taking an image on a monitor television. The photographing apparatus of the present invention includes a display unit for displaying a television image, a unit provided in front of the display unit for holding the projection optical system, and a projection optical system attached to the projection optical system. And a camera having a built-in film for receiving the image, and the distance L satisfies the following condition (1), where L is the distance from the display means to the projection optical system. (1) 1.5f <L <3f where f is the focal length of the entire optical system.

In the condition (1), the value of L is the lower limit of 1.5.
If the size becomes smaller than f, the work space for wiping off dust and the space for arranging the rotary color filter in the optical path become insufficient. Further, the above-mentioned space where the value of L exceeds the upper limit of 3f becomes unnecessarily large, the size of the entire apparatus becomes large, and the angle of view where the focal length f of the optical system is extended becomes narrow and the rotary color filter becomes large.

When the value of L is within the range of the condition (1), in order to make the angle of view as wide as possible without increasing the focal length,
The entrance pupil position may be set as close to the first surface of the lens system as possible, and for that purpose, the lens closest to the object side of the taking lens may be a negative lens.

Table 1 below shows the third-order aberration coefficients of the lens system disclosed in JP-A-60-37514.

Table 1 Surface number Spherical aberration Coma aberration 1 -0.01103 0.04272 2 0.23950 0.03831 3 -0.26851 0.29648 4 -0.00021 -0.00742 5 0.00000 0.00000 6 0.01762 0.09064 7 0.24561 -0.80495 8 -0.11362 0.50029 9 -0.12855 -0.14984 Total -0.01918 0.00622 Total 0.13267 -0.04304 Surface number Astigmatism Distortion 1-0.01838 0.08748 2 0.00068 0.00665 3 -0.03638 0.05350 4 -0.02979 -0.22956 5 0.00000 0.00000 6 0.05180 0.17822 7 0.29312 -0.42034 8 -0.24476 0.42163 9 -0.01941 -0.04608 Total -0.00311 0.05150 Total 0.02152 -0.35621 Surface number Petzval 1 -0.04941 2 0.12408 3 -0.10897 4 0.01073 5 0.00000 6 0.05214 7 0.09165 8 -0.04251 9 -0.09918 Total -0.02148 Total 0.14856 The above values are the values considering the magnification of each lens group. But,
The amount of spherical aberration generated in the third lens group and the fourth lens group is large, and cannot be canceled in total.

In a retrofocus type paraxial lens system as shown in FIG. 24 (A), the negative lens group G ₁ of the front lens group has a function of converting an object point into an imaginary object point. It can be considered that the object point is imaged by the positive lens group G ₂ . Therefore, the lens group G ₂ needs to independently correct aberration for the imaginary object point converted by the lens group G _1. Therefore, as shown in FIG. 24 (B), the lens group G ₂ is a positive lens L ₂ , The negative lens L ₃ and the positive lens L ₄ must be divided into a triplet type paraxial structure. At this time, unless consideration is given to mounting a rear converter or the like, it is not necessary to use a behind diaphragm, and aberration correction can be made advantageous by that amount. Therefore, the diaphragm position AS can be set to the lens L ₂ and the lens L ₃ . It is preferable to install it between them. When the diaphragm position is set as described above, the power balance with respect to the diaphragm is improved, which is advantageous for correction of distortion aberration, and the symmetry with respect to the diaphragm is improved, which is advantageous for correction of coma aberration and astigmatic difference.

In the above-described paraxial lens system, the negative first lens unit L ₁ is used for converting the object distance, and therefore it is preferable that this lens unit alone be used for aberration correction. Therefore, the first lens unit L ₁
It is necessary to suppress the occurrence of distortion and spherical aberration as much as possible by using a meniscus lens using a low-dispersion glass material or a configuration including this meniscus lens. The second lens group L ₂ of MataTadashi, negative third lens group L _3, as a whole a positive three lens group in the fourth lens group L ₄ since an ideal triplet type, second, It is desirable to use glass materials having low dispersion, high dispersion, and low dispersion for the third and fourth lens groups, respectively. In addition, the diaphragm has a second lens unit L ₂ and a third lens unit L ₃ in consideration of power balance due to symmetry and distortion.
It is better to place it in between. Since the second lens unit L ₂ largely affects the occurrence of spherical aberration, it is desirable to make it aplanatic as much as possible, and the curvature of the object side surface is larger than that of the image side surface. The third lens unit L ₃ is a biconcave lens for correcting Petzval sum and astigmatism. Spherical aberration and coma are almost corrected by the first lens unit L ₁ to the third lens unit L _3, but astigmatism that cannot be completely corrected is corrected by the object side surface of the fourth lens unit L _4. There is a need. The correction amount of astigmatism is not very large, large angle of the principal ray is incident on the object-side surface of the fourth lens group L _4, near the surface on the object side of the fourth lens group L ₄ in a planar shape It can be corrected by setting. The fourth here
The image side surface of the lens unit L ₄ needs to be set so that the center of the spherical surface and the exit pupil position are substantially at the same position so that the coma aberration is not overcorrected. Therefore, as described above, the curvature of the object-side surface of the fourth lens unit L ₄ is made smaller than the curvature of the image-side surface.

The optical system for photographing with a monitor of the present invention preferably satisfies the following condition (2). (2) 1.6 <| f _G1 / f _G2 | <2.5 where f _G1 is the focal length of the first lens group, and f _G2 is the composition of the second lens group, the third lens group, and the fourth lens group. The focal length.

The color monitor cannot be made very small because of the production of the shadow mask (mask for separating the RGB phosphors on the monitor light emitting surface), but the monochrome monitor can be made small. However, the film is standard 3
Since a 5 mm film is used, it is desired that the above-mentioned taking lens has a large magnification. In order to realize an optical system having such a large magnification, the focal length may be lengthened or the object distance may be shortened. However, if the focal length is increased, the angle of view becomes narrower as described above, and the rotary color filter becomes larger, so it is necessary to shorten the object distance.

However, the retrofocus type optical system has a feature that the position of the principal point moves toward the image plane side. Therefore, when an attempt is made to shorten the object distance and increase the magnification, from the monitor to the first surface of the optical system. Therefore, it becomes impossible to secure a working space for wiping off dust adhering to the monitor due to static electricity of the monitor and a space for arranging the rotary color filter in the optical path.

In order to secure this distance L sufficiently, the front focal position f _F of the optical system should be as close to the object side as possible with respect to the actual distance L. Therefore, even though it is a retrofocus type optical system, the ratio of the negative power of the front group and the positive power of the rear group of the retrofocus type optical system is set to an appropriate value so that the principal point position is brought to the object side as much as possible. Must be specified.

This condition can be defined by the ratio of the negative power of the front group of the retrofocus type optical system to the positive power of the rear group. Because the position of the principal point is determined by the focal length ratio and the principal point interval. However, by satisfying the condition (1), the condition of the size of the monitor photographing device is almost determined, and thereby the principal point interval between the front group and the rear group is also determined. Therefore, the greatest degree of freedom is the focal length of each group.

For the above reason, the optical system of the present invention preferably satisfies the condition (2). When the lower limit of 1.6 of the condition (2) is exceeded and the ratio of the focal lengths of the front lens group G ₁ and the rear lens group G ₂ decreases, the principal point position shifts to the image side, and the dust adhering to the monitor due to static electricity is wiped off. It becomes impossible to secure a working space for taking the space and a space for arranging the rotary color filter in the optical path. Also, the upper limit of 2.
If the ratio of the focal lengths of the front lens group G ₁ and the rear lens group G ₂ is increased beyond 5, the back focus becomes short. Under this condition (2), the optical system of the present invention is clearly different from the optical system shown in FIG.

In the optical system of the present invention, the lens group L ₁ of the front group G ₁ is formed into a meniscus shape in order to suppress the occurrence of spherical aberration as described above, but this alone makes the lens group L ₁ independent. I can not correct it.

In such an optical system, the state of occurrence of aberration in each lens group is as follows. That is, spherical aberration is largely generated in the first lens unit L ₁ and the second lens unit L ₂ , and is not so much generated in the third lens unit L ₃ and the fourth lens unit L ₄ . Further, coma is largely generated in the first lens unit L ₁ and the second lens unit L _2, and is not so much generated in the third lens unit L ₃ and the fourth lens unit L ₄ . Furthermore, the astigmatism is the first
It is generated in the lens unit L ₁ and the second lens unit L ₂ , is largely generated in the opposite direction in the third lens unit L ₃ , and is generated in the fourth lens unit. Therefore, in order to satisfactorily correct the aberration of the entire system,
The fourth lens unit L ₄ may be mainly corrected for astigmatism that could not be corrected by the first lens unit L ₁ to the third lens unit L ₃ , so that spherical aberration and coma aberration do not occur. do it.

Further, the total magnification of the optical system is determined from the beginning, and the magnification of the first lens unit L ₁ is almost determined in order to secure a space so that dust can be wiped off.
Further magnification of the third lens group L ₃ is believed to be determined because it is desirable to set in the vicinity of -1 for the most compact arrangement of the optical system. Therefore, in order to reduce the magnification of the fourth lens group L ₄ as much as possible, the magnification of the second lens group L ₂ may be reduced, and the magnifications β ₁ and β ₂ of the lens groups on the object side of the diaphragm may be set to be small. . Specifically, it is preferable that the values of β ₁ and β ₂ satisfy the following condition (3). (3) | β ₁ · β ₂ | <0.4 At this time, the distance L from the first surface of the optical system to the object satisfies the above condition (1).

In condition (3), if | β ₁ · β ₂ | becomes smaller than the condition, the occurrence of spherical aberration cannot be suppressed.

This condition can also be defined by the focal length f _{4 of} the fourth lens unit L ₄ . That is, it is preferable to satisfy the following condition (4). (4) 0.3 <f ₄ /f<0.72 where f ₄ is the focal length of the entire optical system.

In the condition (4), when the lower limit of 0.3 is not reached, the power of the fourth lens unit L ₄ becomes strong and the magnification of the fourth lens unit becomes large, so that it becomes impossible to suppress the occurrence of spherical aberration. When the upper limit of 0.72 is exceeded, the magnification of the fourth lens unit L ₄ becomes too small, and the second lens unit L 4
Since ₂ magnification increases the focal length of the second lens group L ₂ is short, it can not be correct the spherical aberration generated in the second lens group L _2.

Further, it is preferable that the following condition (5) is satisfied. (5) | β ₁ | <| β ₂ | <| β ₃ | <| β ₄ | The optical system of the present invention has one more negative lens than the triplet, and Petzval sum is different from that of the triplet.
That is, in the normal triplet type, in order to reduce the Petzval sum to 0, the ray height of the negative lens is made as low as possible and the power is strengthened. However, the optical system of the present invention has one negative lens more than the triplet type. Therefore, it is advantageous in correcting Petzval sum. Therefore, it is not necessary to forcibly determine the power of the negative lens in order to correct the field curvature, and the third lens unit L ₃ has a magnification of about −1 in order to make the entire length of the optical system compact. It is possible to decide the power. Refractive index of the first lens group L ₁ is may be selected refractive index to match the power of the third lens group, the first lens group L ₁ ~ fourth lens group L
_{Since this} is the lens with the lowest height of marginal ray in ₄ , it is desirable to make the refractive index as small as possible. Therefore, the refractive index n ₁ of the first lens unit L ₁ satisfies the following condition (6)
It is desirable to satisfy. (6) n ₁ <1.52 If this condition (6) is not satisfied, field curvature will occur in the positive direction, making it impossible to achieve the flatness of the image surface necessary for a monitor photographing device.

Since the optical system of the present invention has more negative lenses than the triplet type, coma is likely to occur in the positive direction, and the best image surface tends to curve in the positive direction, so that the field curvature changes in the positive direction. It is not preferable because it occurs.

In the optical system of the present invention, aberration is generated unless the focal lengths of the first to fourth lens groups are set so that the magnification is as shown in the condition (5). Therefore, it is desirable that the focal length f _{1 of} the first lens unit L ₁ satisfies the following condition (7). (7) −2 <f ₁ /f<−0.6 The condition (7) defines a paraxial condition for correcting spherical aberration. That is, since the object point by the first lens group L ₁ is converted to the proximity object point, the object distance by the first focal length of the lens group L ₁ to the second lens group L ₂ and subsequent lens groups (lens system) change.

If the upper limit of -0.6 to condition (7) is exceeded, the first
When the lens unit L ₁ has a large power, the NA of the light beam incident on the second lens unit L ₂ becomes large. Therefore the first
You can not suppress the occurrence of spherical aberration even varying the focal length and the first lens group in the second lens group L ₂ and the distance between the second lens group in accordance with the focal length of the lens group L _1. If the lower limit of -2 is exceeded and the power of the first lens unit L ₁ becomes weak, the negative power of the front lens unit necessary as a retrofocus type becomes weak and the necessary back focus cannot be secured, and the radius of curvature difference of the meniscus lens cannot be secured. Becomes smaller and the shape becomes difficult to manufacture.

In the present invention, the second lens unit L ₂ and the third lens unit
It is desirable that the focal length f _2, f ₃ of the lens group L ₃ satisfies the following condition (8). (8) −0.22 <f ₂ · f ₃ / f ² <−0.14 Condition (8) is a condition for correcting coma and astigmatism. The optical system of the present invention is advantageous in correcting Petzval's sum because it has many negative lenses as compared with the triplet type as described above, but coma aberration, particularly coma aberration in the sagittal direction, is likely to occur in the positive direction, so that the best image can be obtained. The surface easily bends in the positive direction. Therefore, it becomes difficult to maintain the flatness of the image plane, which is necessary for a monitor photographing device. Therefore, a condition for correcting the sagittal coma aberration is required. In the case of the type of the optical system of the present invention, the coma aberration and the astigmatic difference are canceled by the second lens unit L ₂ and the third lens unit L ₃ . Thus, for aberration correction, f ₂ ,
f ₃ changes so that f ₂ / f ₃ = constant. However, when f ₂ and f ₃ are simultaneously reduced, the negative power becomes strong in the entire system, so that sagittal coma easily occurs.
Further, when f ₂ and f ₃ become large at the same time, the coma aberration is satisfactorily corrected, but the astigmatism cannot be completely corrected by the first lens unit L ₁ to the third lens unit L ₃ , so this residual astigmatism The aberration must be corrected more than necessary by the fourth lens group. Therefore, spherical aberration and sagittal coma are further increased. For the above reasons, it is preferable to satisfy the above condition (8) in order to correct coma and astigmatism.

[0038] When f _2, f ₃ beyond -0.22 for a lower limit in the condition (8) is greater than not be sufficiently corrected astigmatism, also f ₂ exceeds the -0.14 upper limit, f ₃ When becomes smaller, sagittal coma occurs and the best image plane is curved.

In the optical system of the present invention, the following condition (9)
It is preferable to satisfy (9) −0.1 <r ₄₂ / r ₄₁ <0.5 where r ₄₁ and r ₄₂ are the radii of curvature of the object-side surface and the image-side surface of the fourth lens unit L ₄ , respectively.

The condition (9) is a condition for correcting the residual astigmatic difference that could not be corrected by the first lens group to the third lens group so that spherical aberration and coma aberration are not overcorrected. .

[0041] As described above, since the surface on the image side of the fourth lens group L ₄ are not generate astigmatism, the amount of astigmatism and sagittal coma by bending of the object-side surface of the fourth lens group L ₄ Is decided. Since the value of r ₄₂ is almost constant,
The value of r ₄₁ may be defined as a relative value to r ₄₂ . In the condition (9), when the upper limit of 0.5 is exceeded and r ₄₁ becomes a positive meniscus shape, the negative power due to the object side surface of the fourth lens unit L ₄ becomes strong, and sagittal coma cannot be corrected.
When the lower limit of −0.1 is exceeded and the fourth lens unit L ₄ has a biconvex shape, spherical aberration is undercorrected.

[0042]

Embodiments of the optical system used in the monitor photographing apparatus of the present invention
Here is an example: Example 1 f = 100, F number 7.0 r₁ = 60.4095 d₁ = 7.0198 n₁ = 1.51728 ν₁ = 69.56 r₂ = 31.0921 d₂ = 13.1362 r₃ = 41.8256 d₃ = 7.0198 n₂ = 1.88300 ν₂ = 40.78 r_Four = -309.2320 d_Four = 3.4353 r_Five = ∞ (aperture) d_Five = 4.2678 r₆ = -73.4453 d₆ = 4.6799 n₃ = 1.80518 ν₃ = 25.43 r₇ = 46.6113 d₇ = 11.8757 r₈ = 6968.6747 d₈ = 9.3598 n_Four = 1.75500 ν_Four = 52.33 r₉ = -44.3830 L = 231.65, L / f = 2.317, f_G1= -134.861, f_G2
= 69.079, ｜ f_G1/ F_G2｜ = 1.95, β₁= 0.36047, β₂=
−0.80425, β₃= -1.21677, β_Four= −1.58462, ｜ β₁・
β₂｜ = 0.29, f₁= -134.861 f₂= 42.119, f₃= -34.809, f_Four= 58.447, f_Four/ F =
0.584, f₁/ F = -1.34861, f₃・ F₂/ F²= -0.14
7, r₄₂/ R₄₁= -0.0063689

Example 2 f = 100, F number 6.9 r₁ = 55.2546 d₁ = 7.0746 n₁ = 1.51728 ν₁ = 69.56 r₂ = 31.2277 d₂ = 13.3470 r₃ = 42.4782 d₃ = 7.0746 n₂ = 1.88300 ν₂ = 40.78 r_Four = -391.7651 d_Four = 3.5458 r_Five = ∞ (aperture) d_Five = 4.3945 r₆ = -82.7200 d₆ = 4.7164 n₃ = 1.80518 ν₃ = 25.43 r₇ = 46.9327 d₇ = 11.9535 r₈ = 3078.0832 d₈ = 9.4328 n_Four = 1.75500 ν_Four = 52.33 r₉= -46.5179 L = 233.463, L / f = 2.335, f_G1= -154,322,
f_G2= 70.777, | f_G1/ F_G2｜ ＝ 2.18, β₁= 0.305
6, β₂= -0.76332, β₃= -1.3294, β_Four= -1.4248,
│β₁・ Β₂| = 0.298, f₁= -154.322 f₂= 43.735, f₃= -36.595, f_Four= 60.775, f_Four/ F
= 0.608, f₁/F=-1.54322, f₃・ F₂/ F²= -0.16
004823, r₄₂/ R₄₁= -0.0151126

Example 3 f = 100, F number 7.0 r₁ = 67.9729 d₁ = 7.0044 n₁ = 1.51633 ν₁ = 64.15 r₂ = 32.6353 d₂ = 13.2753 r₃ = 41.8013 d₃ = 7.0044 n₂ = 1.88300 ν₂ = 40.78 r_Four = -382.2351 d_Four = 3.5256 r_Five = ∞ (aperture) d_Five = 4.3584 r₆ = -73.4322 d₆ = 4.6696 n₃ = 1.80518 ν₃ = 25.43 r₇ = 47.5027 d₇ = 6.3257 r₈ = 634.4000 d₈ = 19.3789 n_Four = 1.77250 ν_Four = 49.66 r₉ = -47.0507 L = 231.15, L / f = 2.312, f_G1= -130.379, f
_G2= 68.842, | f_G1/ F_G2｜ = 1.89, β₁= 0.35353,
β₂= -0.85415, β₃= -1.11034, β_Four= -1.66244, |
β₁・ Β₂| = 0.302, f₁= -130.379 f₂= 43.006, f₃= -35.216, f_Four= 57.413, f_Four/ F =
0.574, f₁/F=-1.3038, f₃・ F₂/ F²= -0.151,
r₄₂/ R₄₁= -0.07417

Example 4 f = 100, F number 7.0 r₁ = 61.3275 d₁ = 7.0067 n₁ = 1.51633 ν₁ = 64.15 r₂ = 31.6797 d₂ = 13.2194 r₃ = 42.2249 d₃ = 7.0067 n₂ = 1.88300 ν₂ = 40.78 r_Four = -442.5308 d_Four = 3.5267 r_Five = ∞ (aperture) d_Five = 4.3675 r₆ = -79.9865 d₆ = 4.6712 n₃ = 1.80518 ν₃ = 25.43 r₇ = 45.9104 d₇ = 6.2126 r₈ = ∞ d₈ = 3.0362 n_Four = 1.72000 ν_Four = 50.25 r₉ = 46.8330 d₉= 16.3490 n_Five = 1.77250 ν_Five = 49.66 r_Ten= -46.8330 L = 228.9, L / f = 2.29, f_G1= -138.024, f
_G2= 69.671, | f_G1/ F_G2｜ = 1.98, β₁= 0.36581,
β₂= -0.84922, β₃= -1.08946, β_Four= -1.64882, |
β₁・ Β₂| = 0.311, f₁= -138.024 f₂= 43.952, f₃= -35.638, f_Four= 57.322, f_Four/ F =
0.5732, f₁/F=-1.38024,f₃・ F₂/ F²= -0.156
627, r₄₂/ R₄₁= 0

Example 5 f = 100, F number 7.0 r₁ = 62.1620 d₁ = 7.0715 n₁ = 1.51633 ν₁ = 64.15 r₂ = 31.1840 d₂ = 13.348 r₃ = 41.5397 d₃ = 7.0800 n₂ = 1.88300 ν₂ = 40.78 r_Four = -385.1733 d_Four = 3.5612 r_Five = ∞ (aperture) d_Five = 4.4251 r₆ = -79.9517 d₆ = 4.7143 n₃ = 1.80518 ν₃ = 25.43 r₇ = 44.6898 d₇ = 6.2538 r₈ = ∞ d₈ = 3.0643 n_Four = 1.72000 ν_Four = 50.25 r₉= 46.9086 d₉= 16.5001 n_Five = 1.77250 ν_Five = 49.66 r_Ten= -46.9086 L = 231, L / f = 2.31, f_G1= -131.407, f_G2=
68.812, | f_G1/ F_G2｜ = 1.91, β₁= 0.35473, β₂
= -0.84548, β₃= -1.13251, β_Four= -1.64042, | β₁
・ Β₂| = 0.3, f₁= -131.407 f₂= 42.797, f₃= -35.012, f_Four= 32.9, f_Four/ F = 0.3
29, f₁/F=-1.31407, f₃・ F₂/ F²= -0.14984
085, r₄₂/ R₄₁= 0

Example 6 f = 100, F number 7.0 r₁ = 50.9102 d₁ = 6.9319 n₁ = 1.51633 ν₁ = 64.15 r₂ = 24.7419 d₂ = 10.7570 r₃ = 43.3770 d₃ = 6.9402 n₂ = 1.76200 ν₂ = 40.10 r_Four = -149.7907 d_Four = 3.3858 r_Five = ∞ (aperture) d_Five = 4.5316 r₆ = -147.7122 d₆ = 4.6213 n₃ = 1.84666 ν₃ = 23.78 r₇ = 50.8191 d₇ = 5.8207 r₈ = -87.5912 d₈ = 3.0038 n_Four = 1.57501 ν_Four = 41.49 r₉ = 92.8188 d₉ = 16.1745 n_Five = 1.77250 ν_Five = 49.66 r_Ten= -40.0356 L = 228.8, L / f = 2.288, f_G1= -102.468, f
_G2= 64.355, | f_G1/ F_G2| = 1.59, β₁= 0.3, β₂
= -1.3284, β₃= -0.933, β_Four= -1.4765, | β₁・ Β
₂| = 0.4, f₁= -102.468 f₂= 44.839, f₃= -44.187, f_Four= 62.881, f_Four/ F =
0.629, f₁/F=-1.02468, f₃・ F₂/ F²= −0.
19813, r₄₂/ R₄₁= 0.4571 where r₁ , R₂ , Is the radius of curvature of each lens surface, d
₁ , D₂ , ... is the thickness of each lens and the lens interval, n
₁ , N₂ , ... is the refractive index of each lens, ν₁ , Ν₂ ・ ・ ・
Is the Abbe number of each lens. IH is the image height, 2ω is the image
It is a horn.

The optical system of the present invention is used for photographing on a monitor, and the curvature of the monitor must be taken into consideration. However, since the curvature of the monitor is very small, there is not much influence in practice.

Further, the optical system requires a space for placing the shutter, but in each embodiment, the shutter is placed at the most image side position of the lens system. This shutter is not shown.

In Examples 1 to 3, Examples 1 to 3 have the configurations shown in FIGS. 1 to 3, respectively, and have a first lens group L ₁ , a second lens group L ₂ , a third lens group L ₃ and a fourth lens group L ₃ . Each lens unit L ₄ is composed of a single lens, and is composed of the minimum necessary number of lenses.

In addition, Example 4 and Example 5 are as shown in FIGS. 4 and 5, and the second lens unit L ₂ , the third lens unit L ₃ , and the fourth lens unit L ₄ are not of triplet type, It is advantageous to correct the astigmatic difference by setting the four lens unit L ₄ to a tesser type by combining a negative lens having a low refractive index and low dispersion and a positive lens having a high refractive index and low dispersion. In this case, it is desirable that the fourth lens group satisfy the following condition (10). (10) 0 <n ₄₂ −n ₄₁ <0.2 where n ₄₁ is the refractive index of the negative lens on the object side of the fourth lens group, and n ₄₂ is the refractive index of the positive lens on the image side of the fourth lens group. .

In order to sufficiently bring out the effect of the tesser type, it is preferable to make the difference in the refractive index of the fourth lens group large. However, when the upper limit of 0.2 of the condition (10) is exceeded, the curvature of the joint surface becomes small and the tesser type effect cannot be sufficiently obtained. Also, the curvature of the concave surface on the object side becomes large,
Sagittal coma occurs.

The sixth embodiment has a configuration as shown in FIG.
The fourth lens group is a doublet in which a positive lens made of a glass material having a low refractive index and low dispersion and a negative lens made of a glass material having a high refractive index and high dispersion are cemented to correct lateral chromatic aberration.

Table 2 below shows the aberration coefficients of the optical system of Example 4 described above.

Table 2 Surface Number Spherical Aberration Coma Aberration 1 -0.01811 0.05516 2 0.17123 -0.11846 3 -0.18243 0.35548 4 -0.02218 -0.15280 5 0.00000 0.00000 6 0.06046 0.24505 7 0.11100 -0.48632 8 -0.01037 0.10604 9 -0.01306 0.04983 10 -0.10369- 0.04534 Total -0.00716 0.00865 Total 0.05015 -0.06060 Surface number Astigmatism Distortion 1-0.01866 0.07939 2 0.00911 -0.02868 3 -0.07697 0.12736 4 -0.11697 -0.29474 5 0.00000 0.00000 6 0.11037 0.22994 7 0.23675 -0.49795 8 -0.12051 0.41084 9 -0.02113 0.03189 10 -0.00220 -0.01487 Total -0.00021 0.04317 Total 0.00150 -0.30235 Face Number Petzval 1 -0.05955 2 0.11528 3 -0.11911 4 -0.01136 5 0.00000 6 0.05981 7 0.10420 8 0.00000 9 -0.00394 10 -0.09981 Total -0.01449 Total 0.10147 This Example The third-order aberration coefficient of No. 4 is described in JP-A-60-375.
No. 14, which is the aberration coefficient of the conventional lens system, is 3 as shown in Table 1.
As can be seen from comparison with the following aberration coefficient, it is found that the optical system of the example has the aberration corrected well.

The optical system shown in FIGS. 13 to 15 is an optical system having a structure different from those of the above-described first to sixth embodiments, and is an optical system when a film having a small photographing size is used. These optical systems can also be used as the optical system in the monitor photographing apparatus of the present invention. The data of this optical system are as follows, and the aberrations thereof are as shown in FIGS. Example 1 f = 100, IH = 35.1, effective F number = 7, object distance = 430 r ₁ = 296.4949 d ₁ = 13.1671 n ₁ = 1.74077 ν ₁ = 27.79 r ₂ = -296.4949 d ₂ = 1.3167 r ₃ = 88.9146 d ₃ = 10.5732 n ₂ = 1.72916 ν ₂ ＝ 54.68 r ₄ ＝ 28.2641 d ₄ ＝ 40.7971 r ₅ ＝ ∞ (aperture) d ₅ ＝ 38.5134 r ₆ ＝ -177.3863 d ₆ ＝ 13.1671 n ₃ ＝ 1.57099 ν ₃ ＝ 50.80 r _{7 = -57.8169 d 7 = 2.0387 r 8} = 193.6530 d 8 = 7.0225 n 4 = 1.75520 ν 4 = 27.51 r 9 = 62.8871 d 9 = 21.9452 n 5 = 1.51633 ν 5 = 64.15 r 10 = -125.2203

Example 2 f = 100, IH = 35.1, effective F number = 7, object distance = 415 r ₁ = 351.5433 d ₁ = 12.7156 n ₁ = 1.76182 ν ₁ = 26.55 r ₂ = -351.5433 d ₂ = 1.2716 r _{3 = 131.5047 d 3 = 10.2107 n} 2 = 1.69680 ν 2 = 55.52 r 4 = 36.7944 d 4 = 87.5743 r 5 = ∞ ( _{stop) d 5 = 24.1542 r 6 =} -206.2035 d 6 = 12.7156 n 3 = 1.72916 ν 3 = 54.68 r ₇ = -82.6076 d ₇ = 1.9688 r ₈ = 179.4486 d ₈ = 6.7817 n ₄ = 1.76182 v ₄ = 26.55 r ₉ = 71.5848 d ₉ = 21.1927 n ₅ = 1.51633 v ₅ = 64.15 r ₁₀ = -162.8466

Example 3 f = 100, IH = 35.1, effective F number = 7, object distance = 397 r ₁ = 363.8031 d ₁ = 12.1453 n ₁ = 1.76182 ν ₁ = 26.55 r ₂ = -363.8031 d ₂ = 1.2145 r _{3 = 111.1291 d 3 = 9.7567 n} 2 = 1.77250 ν 2 = 49.66 r 4 = 37.8851 d 4 = 109.3073 r 5 = ∞ ( _{stop) d 5 = 4.0484 r 6 =} -284.3245 d 6 = 12.1453 n 3 = 1.72916 ν 3 = 54.68 of _{r 7 = -83.8306 d 7 = 9.3114} r 8 = 156.1394 d 8 = 6.4775 n 4 = 1.78472 ν 4 = 25.68 r 9 = 67.5438 d 9 = 20.2421 n 5 = 1.51633 ν 5 = 64.15 r 10 = -232.1242 present invention FIG. 19 shows a specific configuration of the image observation apparatus including the projection optical system. In this figure, reference numeral 1 is a housing (main body) of the image display device, and C is provided inside.
RT2 is provided, and an opening 3 is provided on the front wall surface of the CRT2. An opening / closing window 4 is provided above the CRT 2. A rotary filter plate 6 to which a plurality of filters 5 and 5 ′ are attached is provided between the CRT 2 and the opening 3. The rotary filter plate 6 is fixed to the rotary shaft 7, and teeth are provided on the outer peripheral portion. Reference numeral 8 is a motor, and a gear 10 is attached to a rotating shaft 9 thereof. The gear 10 meshes with the teeth on the outer peripheral portion of the rotary filter plate 6, and the rotary filter 6 is rotated as the motor rotates.
The plate rotates about the axis of rotation 7. Reference numeral 11 denotes a photographing adapter having a photographing lens built therein, which can be attached to and detached from the housing 1 by a mount portion 12 provided in the opening 3 of the housing 1. The camera 13 is attached to the other end of the shooting adapter.
Is attached.

With this arrangement, as the rotary filter 6 rotates, the filters 5 and 5'are sequentially positioned on the optical path from the CRT 2 to the taking lens, and the light emitted from the image displayed on the CRT 2 passes through each filter 5. An image is formed on the recording means such as the film 14 of the camera 13 by the taking lens.

With this structure, dust can be wiped off by opening the open / close window and inserting a hand or a jig. Further, since the rotary color filter 6 is arranged at a position extremely close to the optical system, the rotary color filter can be downsized, and it is also advantageous when wiping off dust. Also, the adapter 11 including the projection optical system is attachable to and detachable from the main body 1 via the mount portion 12, but as shown in FIG. 20A, the first lens of the projection optical system (most object side The first surface of the lens 15 is inside the mount surface 12,
As shown in FIG. 20B, the adapter 11 and the camera 13
With the camera body still up, the lens will not hit even on a desk or the like. In this case, as shown in FIG. 20 (C), a frame 16 for preventing the lens from hitting may be provided separately from the mount.

The opening / closing window 4 of the main body 1 may not be provided. In particular, in order to prevent radio wave noise from the outside, it is desirable to eliminate the opening / closing window 4 to improve the electric insulation. The structure for this is shown in FIG.

In FIG. 21, the main body 1 is made of metal to prevent radio noise. Reference numeral 17 is a sealing member for preventing dust from adhering to the screen of the CRT 2. The sealing member 17 is composed of a tubular portion 18 and an expanded portion 19 at the end thereof, and the tubular portion is attached so as to cover the screen of the CRT 2. A rotary filter and a gear 9 are built in the extension part 19, and the rotation shaft of the motor 8 penetrates the wall surface of the extension part and is attached to the gear 9. Sealing member 17
The length of the glass plate 18 is slightly shorter than the distance to the opening 3 of the main body 2, and the glass plate 18 has an opening on the end face on the opening 3 side.
Is attached. The glass plate 18 is coated with an antistatic coating such as a transparent conductive film. Other configurations are the same as those in FIG.

With this structure, since the portions other than the opening 3 are electromagnetically shielded, the adverse effects of radio noise can be reduced. Further, since the glass plate 18 is close to the opening 3, it is possible to easily remove dust and the like.

The sealing member 17 may extend up to the opening 3. In this case, the glass plate may be attached to the opening of the main body instead of the sealing member. The image pickup apparatus of the present invention is configured as described above, and the ray height at the color filter position is h = 3 while ensuring a predetermined magnification.
When a rotary color filter with a square color filter of 7.46 and a diagonal of 37.5 is formed, the diameter of the rotary color filter becomes at least 168 as shown in FIG. 26 (A), which is sufficiently smaller than the conventional one. Therefore, the size of the entire device can be reduced, and the torque of the motor for rotating the rotary color filter can be reduced.

It is considered that the present invention described above constitutes not only the invention described in each of the claims but also the configurations of the following items.

(1) A projection optical system according to claim 5 or 6, wherein the first lens group is not a single lens but the refractive index n ₁ satisfies the following condition (6). (6) n ₁ <1.52 (2) The optical system according to any one of claims 1, 2, 3, 4, 5 or 6 or (1) above, wherein the focal point of the first lens group is A projection optical system that satisfies the following condition (7), where f _{1 is} the distance of f ₁ and f is the focal length of the entire optical system. (7) −2 <f ₁ /f<−0.6 (3) Claims 1, 2, 3, 4, 5 or 6 or any one of the above (1) or (2) In the optical system, the focal lengths of the second lens group and the third lens group are f
A projection optical system that satisfies the following condition (8), where f is the focal length of ₁ , f ₂ and the entire optical system. (8) −0.22 <f ₂ · f ₃ /f<−0.14 (4) Claims 1, 2, 3, 4, 5 or 6 or (1), (2) or (3) above. In the optical system described in any of the above items, when the radii of curvature of the object side surface and the image side surface of the fourth lens group are r ₄₁ and r ₄₂ , respectively, a projection that satisfies the following condition (9) Optical system. (9) -0.1 <r ₄₂ / r ₄₁ <0.5 (5) Claims 1, 2, 3, 4, 5 or 6 or (1), (2), (3) or (4) above. A projection optical system according to any one of the items (1) and (2), which satisfies the following condition (10). (10) 0 <n ₄₂ −n ₄₁ <0.2 (6) Claims 2, 3, 4, 5 or 6 or (1), (2), (3), (4) or (5) above. In the optical system described in any one of the paragraphs (1) to (7), a projection optical system in which a plurality of filters having different transmission wavelength regions from each other are selectively inserted and removed between the display means and the projection optical system. .

[0067]

INDUSTRIAL APPLICABILITY The projection optical system of the present invention and the television image pickup apparatus equipped with this projection optical system are retrofocus type optical systems, and thereby the angle of view is made extremely wide with respect to the focal length. A space for wiping off dust adhering to the lens and a space for arranging the rotary color filter in the optical path are secured, and aberrations including distortion and field curvature are improved, enabling the monitor screen to be shot with good image quality. did.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical system according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the optical system of the present invention.

FIG. 3 is a sectional view of a third embodiment of the optical system of the present invention.

FIG. 4 is a sectional view of Example 4 of the optical system of the present invention.

FIG. 5 is a sectional view of Example 5 of the optical system of the present invention.

FIG. 6 is a sectional view of a sixth embodiment of the optical system of the present invention.

FIG. 7 is an aberration curve diagram of Example 1 above.

FIG. 8 is an aberration curve diagram of Example 2 described above.

FIG. 9 is an aberration curve diagram of Example 3 described above.

FIG. 10 is an aberration curve diagram of Example 4 above.

FIG. 11 is an aberration curve diagram for Example 5 above.

FIG. 12 is an aberration curve diagram for Example 6 above.

FIG. 13 is a cross-sectional view of Example 1 of an optical system that can be used in the device of the present invention.

FIG. 14 is a cross-sectional view of Example 2 of an optical system that can be used in the device of the present invention.

FIG. 15 is a cross-sectional view of Example 3 of an optical system that can be used in the device of the present invention.

16 is an aberration curve diagram of Example 1 above. FIG.

FIG. 17 is an aberration curve diagram of Example 2 above.

FIG. 18 is an aberration curve diagram of Example 3 above.

FIG. 19 is a diagram showing a configuration of a television image capturing device of the present invention.

FIG. 20 is a diagram showing a configuration of an optical system mount attached to the image capturing apparatus.

FIG. 21 is a diagram showing another configuration of the image capturing apparatus of the present invention.

FIG. 22 is a diagram showing a configuration of a conventional image capturing device.

FIG. 23 is a diagram showing a configuration of an image capturing device using a rotary color filter.

FIG. 24 is a diagram showing a paraxial arrangement of a photographing retrofocus type photographing optical system.

FIG. 25 is a diagram showing an example of a conventional retrofocus type optical system.

26 is a diagram showing the configuration of a rotary color filter arranged in the optical system of FIG.

FIG. 27 is a diagram showing the relationship between the angle of view of the image capturing optical system and the filter size of the rotary color filter.

FIG. 28 is a diagram showing a paraxial structure of a conventional retrofocus type optical system including four lens groups.

FIG. 29 is an aberration curve diagram of a conventional optical system during macro photography.

[Explanation of symbols]

 1 Housing 2 CRT 4 Opening / Closing Window 6 Rotating Color Filter 11 Photographic Adapter 13 Camera

Claims (6)

[Claims] 1. A first lens unit comprising, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side, and a positive lens having a curvature of the object side surface larger than that of the image side surface. Two lens groups, a third lens group including a biconcave lens, a fourth lens group including a positive lens in which a curvature of an object side surface is smaller than a curvature of an image side surface, the second lens group and the third lens A projection optical system having an aperture stop arranged between the lens group and the group. 2. A television image projection device comprising the projection optical system according to claim 1, comprising display means for displaying a television image.
Projection from the display means includes a means for holding the projection lens in front of the display means, and a camera having a film attached to the image side of the projection optical system for receiving an image formed by the projection optical system. A television image capturing device satisfying the following condition (1), where L is the distance to the optical system and f is the focal length of the projection optical system. (1) 1.5f <L <3f 3. The projection optical system according to claim 1, wherein the projection optical system satisfies the following condition (2). (2) 1.6 <| f _G1 / f _G2 | <2.5 where f _G1 is the focal length of the first lens group, and f _G2 is the combined focal length of the second, third, and fourth lens groups. is there. 4. The projection optical system according to claim 3, wherein the projection optical system satisfies the following condition (4). (4) 0.3 <f ₄ /f<0.72 where f ₄ is the focal length of the fourth lens group. 5. The projection optical system according to claim 1, wherein the following conditions (1) and (3) are satisfied. (1) 1.5f <L <3f (3) | β ₁ · β ₂ | <0.4 where L is the distance from the display means to the projection optical system,
f is the focal length of the projection optical system, β ₁ and β ₂ are the first, respectively
It is a magnification of the lens group and the second lens group. 6. The method according to claim 4, wherein the following condition (5) is satisfied.
Projection optics. (5) | β ₁ | <| β ₂ | <| β ₃ | <| β ₄ | However, β ₁ , β ₂ , β ₃ and β ₄ are respectively the first lens group,
It is the magnification of the second lens group, the third lens group, and the fourth lens group.