JPH0625826B2 - Compact high-power zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement and development of the most popular four-group zoom system in the past. That is, in the conventional method, as shown in FIG. ₁ , the first lens group for focusing g ₁ , the second lens group for zooming g ₂ ,
The third lens group g ₃ for correction and the fourth lens group as a relay lens
Whether Osamu斂或to g ₁ consists lens group g _4, the g _2, g ₃ of the composite lens system Ahmet O Cal zoom system and zoom system of divergence, and the required focal length this was added g ₄ fixed However, it leads to image formation.

In order to simplify the explanation, a system having an afocal zoom system with g ₁ , g ₂ and g ₃ will be considered below.

It can be performed relatively easily Osamusa corrected by to have a direction of Osamusa canceling it g ₄ if by balancing the remaining Osamusa front Afuokaru system as advantages of conventional methods, also moved during zooming The groups g ₂ and g ₃ are very advantageous in processing and assembling. On the other hand, since the optical total length in the entire zoom range is invariable and the position of g _{2 where} the power is relatively strong changes greatly, the power arrangement of the lens group changes greatly over the entire range, which is particularly disadvantageous for correction of taste. .

As a compact method of this method, the power of g ₂ is strengthened to reduce the moving space for zooming, the telephoto ratio of g ₄ is increased, and the principal point position of each lens type is selected. It is generally used to avoid obstacles to the movement of lens groups, but these inevitably lead to an increase in the power of each lens, which leads to difficulty in correcting the difference. In any case, the conventional methods have limitations in downsizing, high magnification, and high functionality.

The present invention adds a new group to the conventional 4-group zoom system
As a group, the number of movable groups is increased to maintain the advantages of the conventional type, and the drawbacks are compensated.

That is, according to the present invention, the positive lens group G ₁ , the negative lens group G ₂ , the positive or negative lens group G ₃ , and the positive lens group G are sequentially arranged from the object side.
₄ , each lens unit of the negative lens unit G ₅ , and G ₁ , G ₃ , when zooming by changing the air space between each lens unit,
G ₄ and G ₅ are moved in the same direction, and the air gaps between G ₁ and G ₂ and G ₄ and G ₅ are D _1W and D _4W at the wide-angle end and D _1T and D _4T at the telephoto end, respectively. When the focal lengths of G ₁ , G ₂ , G ₄ , and G ₅ are F ₁ , F ₂ , F ₄ , and F ₅ , respectively i) D _1W <D _1T , F ₁ > -2F ₂ ii) D _4T <D _{The present} invention is characterized by being configured so that _4W , F ₄ <-F _5, and is intended to provide a compact high-power zoom lens.

The structure of the present invention will be described below with reference to the drawings.
5 and 5 show the constitution of the present invention. FIG. 3 shows the case where the lens group G ₃ is positive, FIG. 5 shows the case where the lens group G ₃ is negative, and FIG. 1 shows the 4 group constitution. FIG. 2 of the conventional method of FIG.
FIG. 4 is an explanatory diagram for tracing what kind of thinking process the present invention has evolved from the conventional method. The constitution of the present invention will be clarified by tracing the thinking process.

FIG. 1 shows an example of a conventional system consisting of four groups, in which a conventionally fixed relay lens g ₄ is divided into two groups, a positive lens group g ₄₁ and a negative lens group g ₄₂ , as shown in FIG. Split,
When zooming in the afocal group of the front group, at the same time, by changing the interval of g ₄₁ and g ₄₂ , the zoom lens is modified so as to constitute one variable power system. The relay lens system _g the overall focal length of _{4 f 4,} g _41, and the focal length respectively f ₄₁ of g _42, f ₄₂ and the principal point spacing of variable both the _{d 4} f ₄ = f ₄₁ × _{f 42 / (f 41 + f} 42 -d 4) (1) f 41 is positive, because f ₄₂ is a negative, the f ₄₁ -d ₄ <-f ₄₂ from the above equation in order to always positive and _{f 4} If d takes an excessive value of d ₄ , the configuration of the entire system becomes excessive, so that f ₄₁ <-f ₄₂ (2) is a condition.

On the other hand, if the back focal length is P ′ ₄ , then 1 / P ′ ₄ = 1 /
Since (f ₄₁ −d ₄ ) + 1 / f ₄₂ , it is necessary that at least f ₄₁ > d ₄ in order to make P ′ ₄ always positive. Regardless of this condition and the change of d ₄ from the equation (1), f
₄ > f ₄₁ .

Also, if the length from the focus position to G ₄₁ is shown by a function of f ₄ Since f ₄ > f _41, it is known that when f ₄ increases, d ₄ + P ′ ₄ also increases.

In equation (1), f ₄ increases as d ₄ decreases, so
Eventually, as d ₄ becomes smaller, d ₄ + P ′ ₄ becomes larger. This situation can be better understood by comparing the figures (a) and (b) in FIG. When the distance between g ₄₁ and g ₄₂ is reduced from the open position at the wide-angle end to the telephoto side, the focal length of g ₄ gradually increases during this time, but in order to fix the final focal position as a zoom lens, g ₄₁ will move to the object side. Then, g ₄₂ moves toward the object side with a movement amount larger than the movement of g ₄₁ , whereby the distance d ₄ can be gradually reduced. That is, one condition is that the distance between g ₄₁ and g ₄₂ is smaller at the telephoto end than at the wide-angle end.

Next, in this relay system g ₄ , g ₁ as shown in FIG.
It is considered that an afocal zoom system in which g ₂ , g ₃ are respectively composed of a positive lens group, a negative lens group, and a positive lens group is placed in front.

Correction During this time image magnification mainly of the second lens group g ₂ for zooming in the usual manner with a fixed g ₁ when so used in a range of -1 times the concave lens group moves significantly toward the image side The third lens group g ₃ also moves to the image side with a smaller moving amount. During this time, the magnification of the afocal zoom system increases. As shown in FIG. 2, when these two are combined and considered, when the magnification of the afocal zoom system is low, the relay lens g ₄
Has a short focal length, and when the afocal zoom system has a high magnification, the relay lens g ₄ has a long focal length, and as a whole system, a zoom lens system having a higher magnification ratio than the conventional one can be obtained as a synergistic effect of both. become.

Now, in FIG. 2, paraxial rays passing through the spaces g ₃ and g ₄₁ are parallel to the optical axis, so even if this distance is changed, the focal length of the entire system does not change and the focal position does not change. So g ₃ ,
Determine the position of g ₃ according to the movement of g ₄₁ so as to always keep the interval of g _{41 to} the minimum necessary, and slide the positions of g ₁ and g _{2 to} be occupied during zooming according to the position of g ₃ In the format of FIG. 3, g ₁ , g ₂ , g ₃ , g ₄₁ and g ₄₂ are replaced with G ₁ , G ₂ , G ₃ , G ₄ and G ₅ , respectively. This is one case of the constitution of the present invention, and shows the case where the lens group G ₃ is positive.

As you can see from Fig. 3, when the focal length is short (wide-angle end)
Has a short structure length and a long focal length (telephoto end), the structure length is long, and it is possible to compactly store the entire system.

According to the explanation so far, it is necessary to make this form co-movable in 5 groups, but by removing the constraint that the magnification of afocal system or g ₂ does not exceed -1 times, the whole system is one new zooming system. If we revisit, it is not necessary to move the horn group according to the above explanation. In the middle of the process of holding both ends or appropriate two points in the zooming process, the curvilinear movement should be in the range of 1 to 2 in consideration of the correction situation of the difference.
The mechanism can be simplified if the movements of the other groups are linearly proportional to each other. At that time, the magnification of G ₂ is −
Even if it exceeds 1 times, there is no positional problem.

Next, a case where G ₃ is a negative lens group will be described.
As shown in FIG. 4, a negative lens group g ₃₁ and a positive lens group g ₃₂ are added to the lens group g ₃ of the three-group zoom afocal system consisting of the positive lens group, the negative lens group, and the positive lens group in FIG. Split into. If g ₃₁ and g ₃₂ are moved together, it will be exactly the same as the above-mentioned form, but without doing so, it is possible to change the interval between them, and instead g ₃₂ moves exactly the same as g _41. To configure. G ₁ and Figure 3 and when the focal length becomes long as well structural length if so likewise use g ₂ -1 times or less in the case of the aforementioned extends protrudes toward the object side.
Also, since g ₃₂ and g ₄₁ move exactly the same, this is the fifth
As shown in the figure, they are integrated into G ₄ , G ₃₁ is G ₃ , and G ₄₂ is G.
_If we rewrite it as _5, we can think of a new 5 group form here. This is the configuration when G ₃ of the present invention is a negative lens group. Also in this case, as in the previous case, it is not necessary to faithfully protect the movement of the front afocal system and the movement of the rear second group zoom in the middle of zooming. For example, for the advance of G ₁ , G
It is also possible to fix ₂ , and the mechanism is simplified if one or two groups are moved curvilinearly and the other groups are moved proportionally to each other. At this time, the separated g ₃₁ is effective even if the focal length is large.

In the zoom lens system of the present invention shown in FIGS. 3 and 5, the concept is to add a zoom relay system composed of two groups of a front positive lens group and a rear negative lens group to the zoom afocal system of three groups. However, the entire front afore-aural system is moved in accordance with the movement of the front positive lens of the relay lens, and then the whole is reconfigured. As a result, the positive lens group G ₁ , the negative lens group G ₂ , the positive or negative lens group G _{3, the} positive lens group G ₄ , and the negative lens group G ₅ are formed, and when zooming from the wide-angle side to the telephoto side. It moves to each group object side except G ₂ , and the moving amount of G ₁ and G ₅ is larger than the moving amount of G ₃ and G ₄ , that is, D _1W <D _1T , D _4T <D
A new zoom system constructed under the condition of _4W was obtained. It is not new to make the relay lens itself into a zoom lens, but in the past, since the moving space of the normal zoom lens arranged in the front and the moving space of the zoom lens inside the relay lens were independently taken, The overall length of the structure is long, and the structure is complicated and large. In the present invention, the relay zoom system is formed by two groups, and the entire front normal zoom lens system is moved in accordance with the movement of the lens group on the front side.
By satisfying the condition of F ₄ <−F _{5 in which} the formula (2) is replaced in the case of the present invention, it is possible to provide an excellent zoom system with a relatively simple structure as a whole because the increase of the structure length is suppressed.

It should be noted that when zooming from the wide-angle side to the telephoto side, G ₂ has a removed shape, but as described above, G ₂ corresponds to a zoom lens for an afar zoom-from -1x or beyond. To make it usable, set the focal length of G ₁ to F ₁ ,
If the focal length of G ₂ is F ₂ , then F ₁ > −2F ₂ is a condition.

The zoom lens system of the present invention has the following advantages over the conventional system.

i) Since the relay lens itself has a variable magnification effect, the power load of G ₂ can be reduced as compared with the conventional method of the same magnification ratio, or the movement amount of G ₂ is small, so that the zoom lens has high performance or is compact. It is advantageous to Further, if the power burden and the movement amount are the same, naturally a higher magnification can be achieved.

ii) In the conventional method, since the first lens group of the positive lens exists apart at the telephoto end, a pincushion type test procedure is likely to occur. If this is supplemented by another lens, the barrel type test procedure at the wide angle end. Will remain. However, in this system, the fifth lens group of the negative lens at the rearmost portion is present separately at the wide-angle end, so that a pincushion type test situation similar to that at the telephoto end is likely to occur. Therefore, it is necessary to consider so as to suppress the generation of the bobbin-shaped test procedure as a whole. After all, it will be advantageous for the correction of the test point, which is the maximum separation point of the zoom lens.

In iii) the wide-angle end relay lens is the distance from G ₄ from the normal lens so the O connexion telephoto lens configuration in the interval of the positive lens group and the negative lens group is opened to the focal plane is reduced, further Afuokaru system itself When the image magnification is low, the total length becomes short. Therefore, at the wide-angle end, the overall length of the entire system becomes extremely short, which is advantageous for compactification when stored.

iv) Placing a minus lens group at the rear of the zoom lens does not need to increase the diameter of G ₁ because the position of the entrance pupil for the same exit pupil is closer to the object side and closer to G ₁ compared to the case without it. Become. This is not only effective for bi- netting, but also it is possible to prevent deterioration of the peripheral image of the screen due to the chief ray passing through the helicopter part of G ₁ . In the present invention, not only the structure length at the wide-angle end is short, but also the minus lens group is placed at the rear part so that the entrance pupil is close to G ₁ , and the above-mentioned advantages are effectively utilized. There is.

Examples of the present invention will be described below.

P ′ _W and P ′ _T are the back focus at the wide-angle end and the telephoto end, D _1W and D _1T are the air gaps at the wide-angle end and the telephoto end of the first and second groups, and L _W and L _T are the wide-angle end and the telephoto end, respectively. The total length from the edge focus to the front edge of the lens system. D _4W and D _4T are the air distances at the wide-angle end and the telephoto end of the fourth and fifth groups.

In the first and second embodiments, the third lens unit is a negative lens system, and the third embodiment is a third lens system.
The group is an example of a positive lens system.

L _W = 140.40 for F = 72 at the wide-angle end of Example 1,
L _W = 162.30 for F = 86 at the wide-angle end of Example 2,
L _W = 132.65 with respect to F = 61.36 at the wide-angle end of Example 3.

It is known that it is compact at the wide-angle end.

The difference curves for each example are shown in FIGS. 6, 8 and 1.
It is shown in Figure 0 and shows excellent performance.

Example 1 Focal length 72.1 to 114.9 to 204.2 F number 3.6 to 4.1 to 4.6 Example 2 Focal length 86.0 to 137.2 to 243.5 F number 4.4 to 5.0 to 5.6 Example 3 Focal length 58.4 to 77.4 to 110.4 F number 2.05 to 2.30 to 2.56

[Brief description of drawings]

1 (a) and 1 (b) are diagrams showing the configuration of a conventional four-group zoom type lens system, and FIGS. 3 (a) and 3 (b) and FIGS. 5 (a) and 5 (b) are the present invention. Showing the structure of FIG. 2, FIG. 2 (a), (b) and FIG. 4 (a), (b)
Is an explanatory diagram showing the thought process of the present invention.
(A) shows the lens arrangement at the wide-angle end, and (B) shows the lens arrangement at the telephoto end.
FIGS. 6, 8, and 10 are aberration diagrams of Examples 1, 2, and 3, respectively, and (a) of FIGS. 7, 9, and 11 are Example 1, respectively.
2 and 3 are configuration diagrams, and (B) in FIGS. 7, 9, and 11 are diagrams for explaining the movements of the lens positions at the wide-angle end and the telephoto end in Embodiments 1, 2, and 3, respectively. G ₁ ...... First lens group, G ₂ ...... Second lens group G ₃ ...... Third lens group, G ₄ ...... Fourth lens group G ₅ ...... Fifth lens group D _1W , D _2W , D _3W , D _4W …… Air gap at wide angle end D _1T , D _2T , D _3T , D _4T …… Air gap at telephoto end

Claims (1)

[Claims] 1. A lens group consisting of a positive lens group G ₁ , a negative lens group G ₂ , a positive or negative lens group G ₃ , a positive lens group G ₄ , and a negative lens group G ₅ in this order from the object side. G ₁ , G ₃ , G ₄ , G when zooming by changing the air gap between the groups
₅ in the same direction so that the air gaps between G ₁ and G ₂ and G ₄ and G ₅ are D _1W and D _{4W respectively} at the wide-angle end, and D _1T and D _4T at the telephoto end, and G ₁ and G _When the focal lengths of ₂ , G ₄ and G ₅ are F ₁ , F ₂ , F ₄ and F ₅ , respectively i) D _1W <D _1T , F ₁ > -2F ₂ ii) D _4T <D _4W and F ₄ Compact high-power zoom lens characterized by being configured to be <-F ₅ .