JPH07199069A - Aspherical zoom lens and video camera - Google Patents

Abstract

PURPOSE:To obtain an about X10 zoom ratio and back focus which is long enough to insert a color separation optical system by using the aspherical lens for the zoom lens of the video camera. CONSTITUTION:On an object side, a 1st lens group 1 which consists of a concave, a convex, and a meniscus convex lens and is fixed is provided. A 2nd lens group 2 which consists of a meniscus concave, a biconcave, and a convex lens and is movable is provided, and a 3rd lens group 3 which consists of an aspherical single lens and is fixed is provided behind it. A 4 thmovable lens group 4 which includes a lens having at least one aspherical surface and consists of a cemented lens of two-element constitution and one convex lens is provided behind the 3rd lens group 3. The output light of the 4th lens group is spectrally diffracted by the color separation optical system 5 and formed images of respective wavelength bands of R, G, and B are made incident on plural image devices.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aspherical zoom lens having a high zoom ratio and a long back focus, and a video camera using the aspherical zoom lens, which is used in a three-plate video camera or the like. It is a thing.

[0002]

2. Description of the Related Art Recent video cameras are required to have high image quality as well as operability and mobility, and in response to this demand, image pickup devices having small size and high resolution are becoming mainstream.
Along with this, there is a strong demand for a high-power zoom lens that has a large aperture ratio, is small and lightweight, and has high performance. Further, it is desirable that the zoom lens keeps high performance and reduces the number of constituent lenses to reduce the price.

However, a high-power zoom lens generally requires not only a large lens diameter and a large overall lens length, but also a large number of lenses in order to achieve more severe aberration correction. For this reason, high-power zoom lenses are generally large, heavy and expensive, and are often unsuitable for consumer video cameras.

Next, an example of the conventional zoom lens for the above video camera will be described with reference to the drawings (for example, disclosed in Japanese Patent Application No. 5-135016). Figure 21
FIG. 3 is a configuration diagram of a conventional zoom lens for a video camera. In FIG. 21, the first lens group 21 is a condenser lens group, the second lens group 22 is a variable magnification lens group, the third lens group 23 is a condenser lens group, and the fourth lens group 24 is a focus lens. It is a lens group of the part. Further, behind the fourth lens group 24, a color separation optical system 25, a face plate 26 including a crystal filter and an image pickup device, and an image forming surface 27 are provided, respectively. Of the above lens groups, the third lens group 23
And the central convex lens of the fourth lens group 24 is an aspherical lens, and the other lenses are spherical lenses.

The operation of the zoom lens for a video camera thus configured will be described. The first lens group 21 fixed to the image plane 27 has an image forming action,
The lens group 22 moves on the optical axis to change the magnification and changes the focal length of the entire system. Third lens group 23, which is a fixed group
Collects the divergent light generated by the second lens group 22. The fourth lens group 24 moves on the optical axis and performs a focusing action. Further, the fourth lens group 24 eliminates the fluctuation of the image plane position caused by the movement of the second lens group 22 during zooming by the position movement of the fourth lens group 24 itself. Therefore, the image plane 27 is always held in a fixed position.

[0006]

However, as described above, in a zoom lens mainly composed of a spherical lens,
If a zoom ratio of about 10 times and a long back focus are to be ensured, it becomes difficult to correct aberrations in the entire zoom region and the entire imaging distance, which leaves a problem that a high quality image cannot be realized.

The present invention has been made in view of the above-mentioned problems of the prior art, and adopts an optimum aspherical surface shape for the first lens group or an optimum aspherical surface shape for the second lens group. By adopting, a high-performance aspherical zoom lens having a simple structure, a zoom ratio of about 10 times, and a long back focus into which a color separation optical system can be inserted is realized. It is an object to provide a video camera using a spherical zoom lens.

[0008]

According to a first aspect of the present invention, in order from the object side, a first lens group having a positive refractive power and fixed to an image plane, and an optical axis having a negative refractive power are provided. By moving the second lens group that has a zooming effect by moving up, the third lens group having a positive refractive power that is fixed to the image plane and has a light collecting effect, the movement of the second lens group, and the movement of the object An aspherical zoom lens including a fourth lens group having a positive refractive power, which moves on the optical axis so as to keep the fluctuating image surface at a constant position from the reference surface, the third lens group and the fourth lens group. And has an air space, the first lens group is configured to include a concave lens, a convex lens, and a meniscus convex lens in order from the object side, and the second lens group is configured to include a meniscus concave lens, a biconcave lens, and a convex lens. At least one surface of the three lens groups is aspherical The fourth lens group is configured to include a certain lens, and the fourth lens group is configured to include a lens having an aspherical surface shape of at least one surface, a cemented lens having two lenses, and one convex lens. is there.

According to the invention of claim 2 of the present application, the first lens unit having a positive refractive power and fixed to the image surface and the lens having a negative refractive power are moved on the optical axis in order from the object side. The second lens group having a zooming effect, the third lens group having a positive refractive power fixed to the image surface and having a light collecting effect, the movement of the second lens group, and the image plane that fluctuates due to the movement of the object are used as references. An aspherical zoom lens including a fourth lens unit having a positive refractive power, which moves on the optical axis so as to keep a constant position from the surface, and the third lens unit and the fourth lens unit have an air gap. Then
The first lens group includes, in order from the object side, a concave lens, a convex lens, a meniscus convex lens, and a lens having at least one aspherical surface, and the second lens group includes a meniscus concave lens, a biconcave lens, and a convex lens. The third lens group is configured to include a single lens having at least one aspherical surface, and the fourth lens group includes a lens having an aspherical shape of at least one surface, and a cemented lens having two lenses and one lens. It is characterized by including a convex lens.

According to the invention of claim 9 of the present application, the first lens unit having a positive refractive power and fixed to the image surface and the lens having a negative refractive power are moved on the optical axis in order from the object side. The second lens group having a zooming effect, the third lens group having a positive refractive power fixed to the image surface and having a light collecting effect, the movement of the second lens group, and the image plane that fluctuates due to the movement of the object are used as references. An aspherical zoom lens including a fourth lens unit having a positive refractive power, which moves on the optical axis so as to keep a constant position from the surface, and the third lens unit and the fourth lens unit have an air gap. Then
The first lens group includes, in order from the object side, a concave lens, a convex lens, and a meniscus convex lens, and the second lens group includes a meniscus concave lens, a biconcave lens, and a convex lens, and a lens having an aspherical shape of at least one surface. The lens group includes a lens having at least one aspherical surface, and the fourth lens group includes a lens having an aspherical shape including at least one surface, and a cemented lens having two lenses and one convex lens. It is characterized by that.

[0011]

According to the inventions of claims 1 to 6 and 9 to 13 of the present invention having such characteristics, the first lens group is a concave lens, a convex lens, and a meniscus convex lens, and has a positive refractive power to form an image. To work. The second lens group has a meniscus concave lens, a biconcave lens, and a convex lens, has a negative refracting power, and has a zooming effect by moving on the optical axis. The third lens group is composed of an aspherical single lens having a positive refractive power and having a convex surface facing the object side, and has a condensing function at a fixed position. The fourth lens group is composed of two cemented lenses in order from the object side, a convex lens having a convex surface facing the image side, and at least one aspherical surface is provided, so that it has a positive refractive power and is on the optical axis. Adjust the focus by moving.

According to the seventh, eighth or fourteenth and fifteenth aspects of the invention, by using the aspherical zoom lens in the video camera, it is possible to form an image plane on which the aberration is corrected well on the image pickup device. .

[0013]

The aspherical zoom lenses in the first to sixth embodiments of the present invention will be described in detail below with reference to the drawings and tables. FIG. 1 is a configuration diagram of an aspherical zoom lens according to first to fifth embodiments of the present invention. In the aspherical zoom lens in FIG. 1, a first lens group 1, a second lens group 2, a third lens group 3, and a fourth lens group are arranged from the object position toward the image position. And on the optical axis of each lens group,
A color separation optical system 5 and a face plate 6 are provided behind the lens group 4, and an image plane is formed on an image forming plane 7. The color separation optical system 5 is an optical system that separates the light emitted from the fourth lens group 4 into R, B, and G components. Further, the face plate 6 and the crystal filter, the image pickup device and its face plate are included.

Next, each lens group will be described. The first lens group 1 is composed of three lenses 1a, 1b and 1c and is a fixed group lens having a positive refractive power and having an image forming action. The lens 1a has a wall thickness d1 and a radius of curvature r of the object side surface.
1, an aspherical lens having a curvature radius r2 on the image side. The lens 1b is a spherical lens having a thickness d2, a radius of curvature r2 of the object side surface, and a radius of curvature r3 of the image side. The lens 1c has a thickness d4, a curvature radius r on the object side surface, and a curvature radius r on the image surface side.
5 is a meniscus lens. Lens 1b and lens 1c
The air gap d3 of is 0.

The second lens group 2 includes three lenses 2a and 2a.
b, 2c is a lens group which has a negative refracting power and has a zooming effect by moving on the optical axis. The lens 2a is a meniscus lens that is located behind the lens 1c by an air gap d5 that fluctuates and has a thickness d6, a radius of curvature r6 on the object side surface, and a radius r7 of curvature on the image side. Lens 2b
The object side surface of is a concave lens located on the optical axis at a portion separated from the lens 2a by the air space d7, and has a thickness d8, an object side surface curvature radius r8, and an image surface side curvature radius r9. The lens 2c is in close contact with the lens 2b and has a thickness d9 and a radius of curvature r of the object side surface.
9, a spherical lens having a curvature radius r10 on the image plane side.

The third lens group 3 is composed of only one lens 3a and is an aspherical lens having a positive refractive power. Third
The lens group 3 is a fixed group lens that performs a light condensing function. The lens 3a is located behind the lens 2c by an air gap d10 that fluctuates, the wall thickness d11, the radius of curvature r11 of the object side surface,
It is a lens having a curvature radius r12 on the image plane side.

The fourth lens group 4 includes three lenses 4a and 4a.
The lens group b, 4c has a positive refracting power and adjusts the focus by moving on the optical axis. The fourth lens group 4 has a relatively large air gap d12 with the third lens group 3. The lens 4a has a wall thickness d13,
It is a spherical lens having a radius of curvature r13 on the object side and a radius of curvature r14 on the image side. The lens 4b is attached closely to the lens 4a, and has a thickness d14, a radius of curvature r14 of the object side surface,
It is an aspherical lens having a curvature radius r15 on the image side. The lens 4c is in contact with the lens 4b when the air distance d15 on the optical axis is 0, and is a spherical lens having a wall thickness d16, a curvature radius r16 on the object side surface, and a curvature radius r17 on the image surface side.

FIG. 2 shows a block diagram of such an aspherical zoom lens. Here, each lens is given the same reference numeral as in FIG. 1, and the lens configuration will be described. That is, the first lens group 1 is composed of spherical lenses 1a and 1b and a meniscus lens 1c having a positive refractive power in order from the object side. The second lens group 2 includes a lens having an aspherical shape of at least one surface,
Further, it is composed of a meniscus lens 2a having a negative refractive power and cemented lenses 2b and 2c. The third lens group 3 is composed of a lens 3a having at least one aspherical surface. Furthermore, the fourth
The lens group 4 includes lenses having at least one aspherical surface and has two lenses 4a and 4b, and
You may comprise by the convex lens 4c.

In order to make the zoom lens compact, it is necessary to increase the refractive power of each lens group. Now consider the following conditions. (1) f1 / fW (2) | f2 | / fW (3) f3 / fW (4) f4 / fW (5) BF / fW (6) d12 / f4 (7) r11 / f3 (8) | r13 | / F4 (9) | r17 | / f4 where fi: focal length of the i-th lens group (i = 1, 2,
3, 3, 4) fw: focal length of zoom lens at wide angle BF: distance from the last lens surface to the image plane 7 in air

The above condition (1), condition (2), condition (3) and condition (4) are conditional expressions for defining the refracting power of each lens group, and give a strong refracting power for realizing miniaturization. In addition, there is a range in which good aberration performance is satisfied by optimally setting the lens type and surface shape of each lens group.

On the other hand, making the third lens group 3 an aspherical lens having a convex surface facing the object side constitutes the third lens group with a single lens and has a large aperture with an F number of about 1.6. It is essential for correcting aberrations. Especially the third
The aspherical shape of the lens group 3 has a great effect on correction of spherical aberration. Further, the fourth lens group 4 is composed of a cemented lens having two lenses and one convex lens, and at least one of the surfaces has an aspherical shape, so that a long back focus BF can be realized and the number of lenses is as small as three. Therefore, it is indispensable for correcting on-axis and off-axis chromatic aberrations, correcting monochromatic off-axis aberrations, especially coma aberrations, and loosening tolerances in the assembly process. Here, each condition described above will be described in more detail.

The condition (1) is a condition relating to the refractive power of the first lens group 1. If the value of the expression (1) exceeds a certain lower limit, the refracting power of the first lens group 1 becomes too large, which makes it difficult to correct spherical aberration on the long focus side. Further, if the value of the expression (1) exceeds a certain upper limit, the lens length becomes large, and a compact zoom lens cannot be realized.

The condition (2) is a condition relating to the refractive power of the second lens group 2. When the value of the expression (2) deviates from a certain lower limit, the lens group can be made compact, but the Petzval sum of the entire system becomes largely negative, and the field curvature cannot be corrected only by selecting the glass material. On the other hand, if the value of the expression (2) exceeds a certain upper limit, the aberration correction is easy, but the variable power system becomes long and the overall system cannot be made compact.

The condition (3) relates to the refractive power of the third lens group 3. If the value of the expression (3) exceeds a certain lower limit, the refracting power of the third lens group 3 becomes too large, so that a back focus length in which the color separation optical system 5 can be inserted cannot be realized, and it becomes difficult to correct spherical aberration. Become. When the value of the expression (3) exceeds a certain upper limit, the first lens group 1, the second lens group 2,
Since the composite system of the third lens group 3 becomes a divergent system, the lens outer diameter of the fourth lens group 4 located thereafter cannot be reduced. Moreover, the Petzval sum of the entire system cannot be reduced.

The condition (4) is a condition relating to the refractive power of the fourth lens group 4. If the value of the expression (4) deviates from a certain lower limit, the screen comprehensive range becomes narrower, and it is necessary to increase the lens diameter of the first lens group 1 to obtain a desired range, so that it is not possible to realize the reduction in size and weight. If the value of the equation (4) exceeds a certain upper limit, it is easy to correct the aberration, but the fourth
The amount of movement of the lens group 4 becomes large, so that not only the entire system cannot be made compact, but also it becomes difficult to correct the unbalance of off-axis aberrations at the time of short-distance photography and at the time of long-distance photography.

Condition (5) is a conditional expression regarding the back focus length. If the value of the expression (5) exceeds a certain lower limit, it is impossible to insert the color separation optical system 5 having a length sufficient for color separation. If the value of equation (5) exceeds a certain upper limit, it cannot be made compact.

The condition (6) is a conditional expression regarding the air gap between the third lens group 3 and the fourth lens group 4. If the value of expression (6) exceeds a certain lower limit, the off-axis ray height becomes small, and it becomes difficult to correct lateral chromatic aberration only by selecting a glass material. In addition, the amount of movement of the fourth lens group 4 at the time of close-up shooting is restricted, and a sufficient close-up shooting distance cannot be realized. If the value of equation (6) exceeds a certain upper limit, it is difficult to make the entire system compact. In order to secure a sufficient amount of light around the screen, the fourth lens group 4
The outer diameter of the lens cannot be reduced.

The condition (7) relates to the radius of curvature of the object side surface of the aspherical lens forming the third lens group 3.
By introducing an aspherical surface to either one or both of the object side surface and the image side surface and setting the shape optimally, various aberrations can be well corrected despite the single lens. However, if the value of expression (7) exceeds a certain lower limit, it becomes difficult to correct spherical aberration, and if the value of expression (7) deviates from a certain upper limit, it is difficult to correct coma aberration for off-axis rays below the principal ray. Becomes

The condition (8) relates to the radius of curvature of the object side surface of the concave lens forming the fourth lens unit 4.
If the value of expression (8) deviates from the lower limit, the angle of incidence on these surfaces becomes large, and it becomes difficult to correct coma aberration for off-axis rays below the principal ray, and the value of expression (8) If the upper limit is exceeded, the refractive power of the concave lens cannot be increased, and a sufficient back focus cannot be obtained.

The condition (9) is 2 in the fourth lens group 4.
It relates to the radius of curvature of the image side surface of the convex lens located on the image side among the convex lenses. If the value of the equation (9) deviates from a certain lower limit, the exit angle from these surfaces becomes large,
It becomes difficult to correct coma aberration for off-axis rays above the principal ray and distortion aberration on the wide-angle side. On the other hand, if the value of the expression (9) exceeds a certain upper limit, the refractive power of the intermediate convex lens becomes large, so that the back focus having a sufficient length cannot be obtained.

Table 1 shows specific numerical examples of the aspherical zoom lens of the first embodiment.

[Table 1] In Table 1, the number in the first column is the number indicating the lens group,
The number j in the second column is the radius of curvature rj (j of each lens shown in FIG.
= 1 to 20) and is the j-th surface. In the subsequent columns, r is the radius of curvature of each lens surface, d is the wall thickness of each lens or the air gap between the lenses, n is the refractive index for each lens on the d line, and ν is the Abbe number for each lens on the d line. is there.

The aspherical shape is defined by the following equation.

[Equation 1] Here, Z: distance from the aspherical vertex of the point on the aspherical surface at a height Y from the optical axis Y: height from the optical axis C: curvature of the aspherical vertex (= 1 / r) D, E, F, G: Aspherical coefficient K: Conic constant

The first surface, the eleventh surface, the twelfth surface, the fifteenth surface
The surface is an aspherical surface, and the aspherical surface coefficient is shown in Table 2 below.

[Table 2] In Table 2, the first row shows the radii of curvature r1, r11, r1.
The numbers of the lens surfaces of the lenses 1a, 3a and 4b having 2, r15 are shown.

Next, Table 3 shows a case in which the object point is set to infinity by zooming the aspherical zoom lens of this embodiment. In Table 3, when the aspherical zoom lens is set at the wide-angle end, standard, and the telephoto end, the focal length at the wide-angle end of the entire lens system is f, and the F number at the telephoto end is F / NO. The value of d is calculated by simulation.

[Table 3]

Table 4 shows the case where the object point is measured from the tip of the lens by zooming and the aspherical zoom lens is aligned with a position of 2 m. The numerical values in Table 4 are displayed in the same format as in Table 3.

[Table 4]

Similarly, Table 5 shows a case where the aspherical zoom lens is adjusted to a position of 1 m measured from the lens tip end by zooming.

[Table 5]

In Tables 3 to 5 above, the air distance d12 at the standard position is smaller than the other distances, and it is the zoom position where the fourth lens group 4 comes closest to the third lens group 3 at each object point position.

In case of having the above numerical values, equation (1)-
The value of the equation (9) is obtained, and the result is shown in Table 6.

[Table 6]

Next, the aspherical zoom lens according to the second embodiment of the present invention will be described. The structure of the aspherical zoom lens of the second example is similar to that shown in FIG.
Aspherical lenses 3a and 4b are used, and the values of the radius of curvature r, the wall thickness, and the air gap d of each lens forming each lens group are changed and evaluated. These values are shown in Table 7 in the same format as Table 1.

[Table 7]

The third surface, the eleventh surface, the twelfth surface, and the fifteenth surface
The surfaces are aspherical surfaces, and their aspherical coefficients are shown in Table 8 in the same format as Table 2.

[Table 8]

Next, Table 9 shows a case where the object point is measured from the tip of the lens and aligned at a distance of 2 m as an example of a variable air gap by zooming of the aspherical zoom lens of this embodiment.

[Table 9]

In case of having such a numerical value, equation (1)-
The value of the equation (9) is obtained, and the result is shown in Table 10.

[Table 10]

Next, an aspherical zoom lens according to the third embodiment of the present invention will be described. The structure of the aspherical zoom lens of the third example is also similar to that shown in FIG.
Aspherical lenses 3a and 4b are used, and the values of the radius of curvature r, the wall thickness, and the air gap d of each lens forming each lens group are changed and evaluated. These values are displayed in Table 11.

[Table 11]

The fourth surface, the eleventh surface, the twelfth surface, the fifteenth surface
The surface is an aspherical surface, and the aspherical surface coefficients are shown in Table 12.

[Table 12]

Next, as an example of a variable air gap by zooming the aspherical zoom lens of the present embodiment, a case where an object point is measured at a position of 2 m from the tip of the lens and aligned is shown in Table 13.
Shown in.

[Table 13]

In case of having such a numerical value, equation (1)-
The value of the equation (9) is obtained, and the result is shown in Table 14.

[Table 14]

Next, an aspherical zoom lens according to the fourth embodiment of the present invention will be described. The structure of the aspherical zoom lens of the fourth embodiment is similar to that shown in FIG.
Aspherical lenses 1b, 3a, and 4b were used, and the values of the radius of curvature r, the wall thickness, and the air gap d of each lens constituting each lens group were changed and evaluated. These values are shown in Table 15.

[Table 15]

The first surface, the third surface, the eleventh surface, the twelfth surface
The surface and the 15th surface are aspherical surfaces, and the aspherical surface coefficients are shown in Table 16.

[Table 16]

Next, as an example of a variable air gap by zooming of the aspherical zoom lens of the present embodiment, a case where the object point is measured from the tip of the lens and the position is set at 2 m is shown in Table 17.
Shown in.

[Table 17]

In case of having such a numerical value, equation (1)-
The value of the equation (9) is obtained, and the result is shown in Table 18.

[Table 18]

Next, the aspherical lens of the fifth embodiment of the present invention will be described. The structure of the aspherical lens of the fourth embodiment is also the same as that shown in FIG. 1, and the lenses 3a and 4b are aspherical lenses, respectively, and the radius of curvature r, the wall thickness, and the air of each lens constituting each lens group are equal to each other. The value of the interval d was changed and evaluated. These values are displayed in Table 19.

[Table 19]

The eleventh surface, the twelfth surface, and the fifteenth surface are aspherical surfaces, and the aspherical surface coefficients are shown in Table 20.

[Table 20]

Next, as an example of a variable air gap by zooming of the aspherical zoom lens of the present embodiment, a case where an object point is measured at a position of 2 m from the tip of the lens and aligned is shown in Table 21.
Shown in.

[Table 21]

In case of having such a numerical value, equation (1)-
The value of the equation (9) is obtained, and the result is shown in Table 22.

[Table 22]

Finally, an aspherical lens according to the sixth embodiment of the present invention will be described. The structure of the aspherical lens of the sixth embodiment is similar to that shown in FIG. 2, and the lenses 2b, 3a, 4b are
Were used as aspherical lenses, and the values of the radius of curvature r, the wall thickness, and the air gap d of each lens constituting each lens group were changed and evaluated. These values are shown in Table 23.

[Table 23]

The eighth, eleventh, twelfth, and fifteenth surfaces
The surface is an aspherical surface, and the aspherical surface coefficients are shown in Table 24.

[Table 24]

Next, as an example of a variable air gap by zooming of the aspherical zoom lens of this embodiment, a case where an object point is measured from the front end of the lens and a position of 2 m is aligned is shown in Table 25.
Shown in.

[Table 25]

In case of having such a numerical value, equation (1)-
The value of the equation (9) is obtained, and the result is shown in Table 26.

[Table 26]

In the aspherical zoom lenses of the first to sixth examples designed as described above, five aberrations which are the object of the characteristic evaluation of the lens system will be described. 3 to 20 are explanatory diagrams showing aberrations of an aspherical Sume lens, in each of which (a) is spherical aberration, (b) is astigmatism, (c) is distortion, and (d) is axial chromatic aberration. , (E) are graphs showing lateral chromatic aberration.

In each figure (a), the horizontal axis shows the aberration (mm) from the ideal image plane, and the vertical axis shows the pupil height of the axial ray by the F number. The solid curve is the characteristic for the d line, and the dotted line shows the sine condition. The sine condition means that when spherical aberration is removed from a set of conjugate points on the axis of the optical system, a small area perpendicular to the axis passing through these conjugate points is imaged without aberration. Is a necessary condition of.

In each figure (b), W on the vertical axis is the intersection angle between the optical axis of the object point and the central axis of the lens. The solid curve shows sagittal field curvature, and the dotted curve shows meridional field curvature. Further, in (c), the horizontal axis represents the distortion rate when the rectangular object is distorted into a barrel shape or a bobbin.
In (d) and (e), the solid curve is the d-line, the dotted curve is the F-line, and the broken line (there is a figure overlapping with the solid line) is the chromatic aberration with respect to the C-line.

FIGS. 3, 4, and 5 are aberration charts at the wide-angle end, standard, and telephoto end of the aspherical zoom lens of the first embodiment shown in Table 1, respectively. Similarly, FIG. 6, FIG. 7, and FIG.
6A and 6B are aberration diagrams of the aspherical zoom lens of Example 2 shown in Table 7, respectively. FIGS. 9, 10 and 11 are aberration diagrams of the aspherical zoom lens of Example 3 shown in Table 11. Further, FIGS. 12, 13 and 14 are aberration diagrams of the aspherical zoom lens of the fourth example shown in Table 15, respectively. 15, 16 and 17 are aberration diagrams of the aspherical zoom lens of the fifth example shown in Table 19, respectively. And FIG. 18, FIG.
20 is an aberration diagram of the aspherical zoom lens of Example 6 shown in Table 23, respectively.

Judging from these FIGS. 3 to 20, it can be seen that the aspherical zoom lenses of the respective examples have good optical performance. Further, since the back focus BF of these aspherical zoom lenses is set to be long, a space for installing the color separation optical system 5 between the fourth lens group 4 and the image plane 7 as shown in FIG. 1 or 2. It is possible to provide a three-plate type color separation optical system 5 which is sufficiently large, is composed of a prism, and is larger than a single plate type. And CCD
A three-panel type with excellent performance by integrally providing a mechanism section for inputting a pixel signal output from an image pickup device such as an image pickup device to a signal processing circuit to record a video signal on a recording medium and a viewfinder for monitoring an image pickup field of view. Video camera can be realized.

[0064]

As described above, according to the inventions of claims 1 to 6 or 9 to 13, the F number is about 1.6, the zoom ratio is about 10 times, and the back focus is long. A high-performance aspherical zoom lens can be realized, and the total number of lenses that make up each lens group can be realized with a small number of 10. Thus, a compact, lightweight and high-performance zoom lens can be obtained. .

Further, according to the invention of claims 7 and 8 or 14 and 15, by using this aspherical zoom lens, it is possible to realize a compact, lightweight and high performance three-plate type video camera.

[Brief description of drawings]

FIG. 1 is a lens arrangement diagram showing a configuration of an aspherical zoom lens according to first to fifth examples of the present invention.

FIG. 2 is a lens arrangement diagram showing a configuration of an aspherical zoom lens according to Example 6 of the present invention.

FIG. 3 is an aberration diagram at a wide-angle end of the aspherical zoom lens of Example 1.

FIG. 4 is an aberration diagram at a standard point of the aspherical zoom lens of Example 1.

FIG. 5 is an aberration diagram at a telephoto end of the aspherical zoom lens according to the first example.

FIG. 6 is an aberration diagram at a wide-angle end of an aspherical zoom lens according to a second example.

FIG. 7 is an aberration diagram at a standard point of the aspherical zoom lens of Example 2.

FIG. 8 is an aberration diagram at a telephoto end of an aspherical zoom lens according to a second example.

FIG. 9 is an aberration diagram at a wide-angle end of an aspherical zoom lens according to Example 3.

FIG. 10 is an aberration diagram at a standard point of the aspherical zoom lens according to the third example.

FIG. 11 is an aberration diagram at a telephoto end of an aspherical zoom lens according to a third example.

FIG. 12 is an aberration diagram at a wide-angle end of an aspherical zoom lens according to Example 4.

FIG. 13 is an aberration diagram at a standard point of the aspherical zoom lens of Example 4.

FIG. 14 is an aberration diagram at a telephoto end of an aspherical zoom lens according to a fourth example.

FIG. 15 is an aberration diagram at a wide-angle end of an aspherical zoom lens according to Example 5.

FIG. 16 is an aberration diagram at a standard point of the aspherical zoom lens of Example 5.

FIG. 17 is an aberration diagram at a telephoto end of an aspherical zoom lens according to a fifth example.

FIG. 18 is an aberration diagram at a wide-angle end of an aspherical zoom lens according to Example 6.

FIG. 19 is an aberration diagram at a standard point of the aspherical zoom lens according to the sixth example.

FIG. 20 is an aberration diagram at a telephoto end of an aspherical zoom lens according to a sixth example.

FIG. 21 is a lens arrangement diagram showing a configuration of a conventional zoom lens.

[Explanation of symbols]

 1 1st lens group 1a-1c, 2a-2c, 3a, 4a-4c lens 2 2nd lens group 3 3rd lens group 4 4th lens group 5 color separation optical system 6 face plate 7 imaging surface

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[Procedure amendment]

[Submission date] April 4, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 7

[Correction method] Change

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[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 8

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 14

[Correction method] Change

[Correction content]

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 15

[Correction method] Change

[Correction content]

Claims (15)

[Claims] 1. A first lens unit having a positive refracting power and fixed to an image plane in order from the object side, and a second lens unit having a negative refracting power and having a zooming effect by moving on the optical axis. A lens group, a third lens group having a positive refractive power which is fixed to the image surface and has a light-collecting action, and an image surface which changes due to movement of the second lens group and movement of an object are set at a fixed position from the reference plane. A fourth lens group having a positive refractive power, which moves on the optical axis so as to keep it;
An aspherical zoom lens including: the third lens group and the fourth lens group having an air gap, and the first lens group includes a concave lens, a convex lens, and a meniscus convex lens in order from the object side. The second lens group is configured to include a meniscus concave lens, a biconcave lens, and a convex lens, the third lens group is configured to include a lens having at least one aspherical surface, and the fourth lens group is An aspherical zoom lens comprising a lens having an aspherical shape of at least one surface, and a cemented lens having two lenses and one convex lens. 2. A first lens unit having a positive refracting power and fixed with respect to an image plane in order from the object side, and a second lens unit having a negative refracting power and having a zooming effect by moving on the optical axis. A lens group, a third lens group having a positive refractive power which is fixed to the image surface and has a light-collecting action, and an image surface which changes due to movement of the second lens group and movement of an object are set at a fixed position from the reference plane. A fourth lens group having a positive refractive power, which moves on the optical axis so as to keep it;
An aspherical zoom lens including: the third lens group and the fourth lens group having an air gap, and the first lens group includes a concave lens, a convex lens, and a meniscus convex lens in order from the object side, and at least 1 The second lens group includes a meniscus concave lens, a biconcave lens, and a convex lens, and the third lens group includes a single lens having at least one aspheric surface. And the fourth lens group includes a lens having an aspherical surface having at least one surface, a cemented lens having two lenses, and a convex lens, and the aspherical zoom lens. 3. The aspherical zoom lens according to claim 1, wherein the third lens group is an aspherical single lens having a positive refractive power and a convex surface facing the object side. 4. The fourth lens group, in order from the object side,
3. The aspherical zoom lens according to claim 1, wherein the aspherical zoom lens is composed of a cemented lens having two lenses and a convex lens having a convex surface facing the image side, and at least one surface has an aspherical shape. 5. fW is the focal length at the wide-angle end, fi
(I = 1, 2, 3, 4) is the focal length of the i-th lens group, B
F is the distance from the last lens surface to the image plane in air, d12 is the air distance between the third lens group and the fourth lens group, r11 is the radius of curvature of the object side surface of the convex lens forming the third lens group, When r13 is the radius of curvature of the surface of the cemented lens closest to the object that constitutes the fourth lens group and r17 is the radius of curvature of the image side surface of the convex lens that constitutes the fourth lens group, (1) 3.0 <f1 / fW <8.0 (2) 0.5 <| f2 | / fW <1.6 (3) 2.0 <f3 / fW <7.0 (4) 2.0 <f4 / fW <5.0 ( 5) 1.5 <BF / fW <5.0 (6) 0.02 <d12 / f4 <1.0 (7) 0.3 <r11 / f3 <1.5 (8) 0.3 <| r13 | / F4 <3.0 (9) 0.3 <| r17 | / f4 <1.5 are satisfied, respectively. The aspherical zoom lens described. 6. fW is the focal length at the wide-angle end, fi
(I = 1, 2, 3, 4) is the focal length of the i-th lens group, B
F is the distance from the last lens surface to the image plane in air, d12 is the air distance between the third lens group and the fourth lens group, r11 is the radius of curvature of the object side surface of the convex lens forming the third lens group, When r13 is the radius of curvature of the surface of the cemented lens closest to the object that constitutes the fourth lens group and r17 is the radius of curvature of the image side surface of the convex lens that constitutes the fourth lens group, (1) 5.5 <f1 / fW <6.3 (2) 1.0 <| f2 | / fW <1.2 (3) 5.3 <f3 / fW <6.2 (4) 3.0 <f4 / fW <3.3 ( 5) 3.2 <BF / fW <4.2 (6) 0.1 <d12 / f4 <0.4 (7) 0.5 <r11 / f3 <0.9 (8) 1.1 <| r13 | / F4 <2.4 (9) 0.6 <| r17 | / f4 <0.8 is satisfied, respectively. The aspherical zoom lens shown. 7. The aspherical zoom lens according to claim 5, a color separation optical system for splitting the output light of the aspherical zoom lens into a single color, and a pixel signal for each single color image split by the color separation optical system. A video camera, comprising: a plurality of image pickup devices each of which is converted into a video camera. 8. The aspherical zoom lens according to claim 6, a color separation optical system that separates the output light of the aspherical zoom lens into a single color, and a pixel signal that represents each single color image separated by the color separation optical system. A video camera, comprising: a plurality of image pickup devices each of which is converted into a video camera. 9. A first lens unit having a positive refracting power and fixed with respect to an image surface in order from the object side, and a second lens unit having a negative refracting power and having a zooming action by moving on the optical axis. A lens group, a third lens group having a positive refractive power which is fixed to the image surface and has a light-collecting action, and an image surface which changes due to movement of the second lens group and movement of an object are set at a fixed position from the reference plane. A fourth lens group having a positive refractive power, which moves on the optical axis so as to keep it;
In the aspherical zoom lens including, the third lens group and the fourth lens group have an air gap, the first lens group includes a concave lens and a convex lens and a meniscus convex lens in order from the object side, The second lens group includes a meniscus concave lens, a biconcave lens and a convex lens, and a lens having at least one aspherical surface, and the third lens group includes a lens having at least one aspherical surface. An aspherical zoom lens, wherein the lens group includes at least one lens having an aspherical shape, a cemented lens having two lenses, and one convex lens. 10. The aspherical zoom lens according to claim 9, wherein the third lens group is an aspherical single lens having a positive refractive power and a convex surface facing the object side. 11. The fourth lens group is composed of, in order from the object side, a cemented lens having two lenses and a convex lens having a convex surface directed toward the image side, and at least one surface has an aspherical shape. The aspherical zoom lens according to claim 9. 12. fW is the focal length at the wide-angle end, fi
(I = 1, 2, 3, 4) is the focal length of the i-th lens group, B
F is the distance from the last lens surface to the image plane in air, d12 is the air distance between the third lens group and the fourth lens group, r11 is the radius of curvature of the object side surface of the convex lens forming the third lens group, When r13 is the radius of curvature of the surface of the cemented lens closest to the object that constitutes the fourth lens group and r17 is the radius of curvature of the image side surface of the convex lens that constitutes the fourth lens group, (1) 3.0 <f1 / fW <8.0 (2) 0.5 <| f2 | / fW <1.6 (3) 2.0 <f3 / fW <7.0 (4) 2.0 <f4 / fW <5.0 ( 5) 1.5 <BF / fW <5.0 (6) 0.02 <d12 / f4 <1.0 (7) 0.3 <r11 / f3 <1.5 (8) 0.3 <| r13 | / F4 <3.0 (9) 0.3 <| r17 | / f4 <1.5, respectively. 10. Aspherical zoom lens. 13. fW is the focal length at the wide-angle end, fi
(I = 1, 2, 3, 4) is the focal length of the i-th lens group, B
F is the distance from the last lens surface to the image plane in air, d12 is the air distance between the third lens group and the fourth lens group, r11 is the radius of curvature of the object side surface of the convex lens forming the third lens group, When r13 is the radius of curvature of the surface of the cemented lens closest to the object that constitutes the fourth lens group and r17 is the radius of curvature of the image side surface of the convex lens that constitutes the fourth lens group, (1) 5.5 <f1 / fW <6.3 (2) 1.0 <| f2 | / fW <1.2 (3) 5.3 <f3 / fW <6.2 (4) 3.0 <f4 / fW <3.3 ( 5) 3.2 <BF / fW <4.2 (6) 0.1 <d12 / f4 <0.4 (7) 0.5 <r11 / f3 <0.9 (8) 1.1 <| r13 | / F4 <2.4 (9) 0.6 <| r17 | / f4 <0.8 is satisfied, respectively. Spherical zoom lens. 14. The aspherical zoom lens according to claim 12, a color separation optical system for splitting the output light of the aspherical zoom lens into a single color, and a pixel signal for each single color image split by the color separation optical system. A video camera, comprising: a plurality of image pickup devices each of which is converted into a video camera. 15. The aspherical zoom lens according to claim 13, a color separation optical system that separates the output light of the aspherical zoom lens into a single color, and a pixel signal that represents each single color image separated by the color separation optical system. A video camera, comprising: a plurality of image pickup devices each of which is converted into a video camera.