JPH1195084A - Focusing method for zoom lens device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently display the function of each movable lens group so as to be adjustable in a short time by shifting the correction quantity in a designed cam curve to form a cam curve for controlling first and second movable lens groups. SOLUTION: The position of a second movable lens group 5 in a telephotographic position in the second movable lens group 5 is made FT, the position of the second movable lens group 5 in a wide angle position is made FW, inclination in the designed telephotographic position of a graph line (designed cam curve) showing the position relation of first and second movable lens groups 3, 5 is made KT, and inclination in the designed large angle position is made KW. The correction quantity (Δz) of the movable lens group 3 is to be (Δz)= (fW-FW)-(FT-FW)}/(KW-KT), and the correction quantity Δf of the second movable lens group 5 is to be Δf=(fW-FW)+Km .Δz. These correction values Δz, Δf are shifted in the designed cam curve to form a cam curve (cam curve after correction) for controlling the first and second movable lens groups 3, 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a novel focus adjustment method for a zoom lens device. More specifically, the present invention relates to a technique of adjusting a focus shift of each manufactured product caused by a tolerance or an assembly error of parts in manufacturing the zoom lens apparatus, that is, a so-called flange back adjustment technique.

[0002]

2. Description of the Related Art For example, a four-unit zoom lens device a has four lens units of a first lens unit b, a second lens unit c, a third lens unit d, and a fourth lens unit e from the object side. And a solid-state imaging device (CCD) f as an imager is disposed behind the fourth lens group e (see FIG. 4).

[0003] Among the above lens groups, a second lens group c and a fourth lens group e are movable lens groups provided so as to be movable with respect to the lens barrel, and the second lens group c has a magnification. A variator (first movable lens group) for changing, and a fourth lens group e is a compensator (second movable lens group) for correcting the image point movement caused by the magnification change.

In such a zoom lens device a, data (map) indicating the design position of each of the variator c and the compensator e in the ideal lens system for focusing at each magnification from the wide-angle end to the telephoto end is obtained. In design, if the variator c and the compensator e are moved in accordance with the map, no defocus occurs during photographing.

FIG. 5 is a graph showing data at a certain subject distance calculated from the design values of the variator c and the compensator e of the ideal lens system, and shows the respective magnifications from the wide-angle end Zw to the telephoto end Zt. , The design positions which are the respective positions of the variator c and the compensator e which are focused on the design.

As can be seen from FIG. 5, when the zooming direction is one direction, the variator c moves in one direction,
No inflection point occurs on the movement locus. On the other hand, the compensator e once moves forward and then again
It moves rearward, and its movement locus has an inflection point. The inflection point is usually at the same magnification or slightly on the telephoto side, depending on the design of the lens system.

FIG. 6 is a graph showing a positional relationship between a variator c and a compensator e as an ideal lens system (design value cam curve). The vertical axis indicates the position of the compensator e and the horizontal axis. Shaft is variator c
And a maximum point appears near the telephoto end. The maximum point corresponds to the inflection point, and the inflection point is g.

However, when the zoom lens device a is manufactured, dimensional tolerances occur in each component of the zoom lens device a. When the variator c and the compensator e are moved according to the map, the respective dimensional tolerances, in particular, the position sensors (not shown) for detecting the positions of the variator c and the compensator e are omitted. Due to the mounting dimensional tolerance of the position with respect to the lens barrel, the positions of the variator c and the compensator e which are actually focused are different from the above-described design positions, and a defocus occurs at the time of photographing.

Therefore, in the zoom lens device a,
Usually, in the adjustment stage after manufacturing, the amount of defocus is detected for each product, and the correction amount calculated from the detected amount of deviation is stored in, for example, a memory of a control circuit of each product, and photographed. At times, defocus is prevented.
Note that such adjustment is performed for each manufactured product, and this is referred to as flange back adjustment.

The flange back adjustment in the above-described four-group lens type zoom lens apparatus a is usually performed as follows.

(1) The variator c and the compensator e are moved near the inflection point g of the design value cam curve.

(2) The variator c is moved to detect a position where the defocus is minimized. Although the design is in a state of focus at the inflection point g (so-called jaspin), the focus is shifted for the above-described reason, and therefore, a position closest to the jaspin is detected.

(3) By moving the compensator e
A focus position, that is, a jaspin position is detected. Thereby, the actual inflection point g 'is detected.

(4) The compensator e is moved to the design telephoto end position h, and then the variator c is moved to detect the in-focus position, and the position is determined by the actual telephoto end h of the variator c and the compensator e. '.

(5) The compensator e is moved to the designed wide-angle end position i, and then the variator c is moved to detect the in-focus position, and the position is determined by the actual wide-angle end i of the variator c and the compensator e. '.

(6) The design value cam curve is translated in the direction of the vertical axis (the position of the compensator e) so that the inflection point g of the design value cam curve coincides with the actual inflection point g '.

(7) The design telephoto end position h is represented by the vertical axis (the position of the compensator e) and the horizontal axis (the position of the variator c).
And the design value cam curve is deformed so as to match the actual telephoto end h '.

(8) Design the wide-angle end position i with the vertical axis (position of compensator e) and horizontal axis (position of variator c)
And the design value curve is deformed so as to match the actual wide-angle end i ′.

The cam curve (corrected cam curve) obtained in this way is stored in a memory, for example, and the flange back adjustment is completed. For the zoom lens device a completed as the product, the variators c and The movement of the compensator e is controlled based on the corrected cam curve.

[0020]

However, as described above, in the focus adjustment method (flange back adjustment) of the conventional zoom lens apparatus, the design value cam curve (FIG. 6) is used.
Is shown by a solid line. ) Is corrected so that the three inflection points g, the design telephoto end h, and the design wide-angle end i coincide with the actual inflection point g ', the telephoto end h', and the wide-angle end i ', respectively. The cam curve (indicated by a broken line in FIG. 6) has a different shape from the design value cam curve, and there is a problem that the optimal amount of movement of each movable lens group differs optically.

That is, in designing the zoom lens device, each movable lens group is designed with a movement amount that can exhibit its function most. In other words, the zoom lens device cannot perform its function as designed.

In addition, the conventional flange back adjustment cannot be performed unless the inflection point g, the design telephoto end h, and the design wide-angle end i are detected, and there is a problem that it takes time. Was.

In view of the above, it is an object of the present invention to adjust the focus of the zoom lens apparatus so that the function of each movable lens group can be sufficiently exhibited and the adjustment can be performed in a short time.

[0024]

In order to solve the above-mentioned problems, the focus adjusting method of the zoom lens apparatus according to the present invention includes: (1) a first movable lens group calculated from a design value of an ideal lens system; After moving the first movable lens group to the design value telephoto end in, the second movable lens group is moved to measure the focal point (f _T ), and (2) the first movable lens calculated from the design value After moving the first movable lens group to the design value wide angle end of the lens group, the second movable lens group is moved to measure the focal point (f _W ), and (3) the second calculated from the design value The position of the second movable lens group at the telephoto position (designed telephoto position of the second movable lens group) in the movable lens group is denoted by F
_{Let T} be the position of the second movable lens group at a wide-angle position (design wide-angle position of the second movable lens group) in the second movable lens group calculated from the design value, and F _W be obtained from the design value. Let K _T be the inclination of a graph line (design value cam curve) representing the positional relationship between the first movable lens group and the second movable lens group at the design telephoto position and K _{W be the} inclination at the design wide-angle position. correction amount of the first movable lens (Δz) Δz = {(f T -f W) - (F T -F W)} / (K W -K T) correction amount of the second movable lens (Delta] f) Assuming that Δf = (f _W −F _W ) + K _W · Δz, the design value cam curve is corrected by these correction amounts Δz and Δz.
By shifting f, a cam curve (a corrected cam curve) for controlling the first movable lens group and the second movable lens group is formed.

Therefore, according to the focus adjusting method of the zoom lens apparatus of the present invention, it is possible to form the corrected cam curve without deforming the design value cam curve, whereby the function of each movable lens group can be sufficiently achieved. It is possible to exhibit the function as designed as a zoom lens device.

Further, the cam curve after correction can be formed only by detecting the two points at the telephoto end and the wide-angle end, and the adjustment time can be reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the focus adjusting method (flange back adjustment) of the zoom lens apparatus according to the present invention will be described below with reference to the embodiments shown in the accompanying drawings.

FIG. 1 schematically shows a four-group zoom lens apparatus 1, in which a first lens group 2, a second lens group 3, a third lens group 4, and a fourth lens group 5 from the object side. A solid-state imaging device (CCD) 6 as an imager is provided behind the fourth lens group 5.

The second lens group 3 and the fourth lens group 5 are provided so as to be movable with respect to the lens barrel.
Variator (first lens group) for changing the magnification
Movable lens group), and a compensator (second lens group) for correcting movement of an image point caused by zooming by the fourth lens group 5.
Movable lens group).

FIG. 2 is a graph showing data at a certain subject distance calculated from design values of the variator 3 and the compensator 5 of the ideal lens system.
For each magnification from w to the telephoto end Zt, a design position which is the position of the variator 3 and the compensator 5 that are focused on design is shown.

As can be seen from FIG. 2, when the zooming direction is one direction, the compensator 5 of the zoom lens device 1 sets the movement range within a range where no inflection point occurs on the movement locus. Have been.

FIG. 3 is a graph showing the positional relationship between the variator 3 and the compensator 5. The vertical axis indicates the position of the compensator 5 and the horizontal axis indicates the position of the variator 3. Indicates an ideal lens system (design value cam curve f (z)), and a broken line indicates a corrected one (corrected cam curve F (z)).

The flange back adjustment in the zoom lens device 1 is performed as follows.

[0034] (1) after moving the variator 3 to the design value telephoto end Z _T in the variator 3 is calculated from the design value of the ideal lens system, measuring the focus f _T by moving the compensator 5.

(2) After moving the variator 3 to the design value wide-angle end Z _W of the variator 3 calculated from the design value, the compensator 5 is moved to measure the focal point f _W. (3) The position of the second movable lens group at the telephoto position in the second movable lens group calculated from the design value (the design telephoto position of the second movable lens group) is F _T, and the position is calculated from the design value. The position of the second movable lens group at a wide-angle position (design wide-angle position of the second movable lens group) in the second movable lens group is F _W, and the first position obtained from the design value is F _W.
The inclination in the design telephoto position of the movable lens group and the second graph line representing the positional relationship between the movable lens group (design value cam curve) and K _T, the slope of the design wide angle position as K _W, first of Correction amount of movable lens group (Δz) Δz = {(f _T −f _W ) − (F _T −F _W )} / (K _W −K _T ) Correction amount of second movable lens group (Δf) Δf = Assuming that (f _W -F _W ) + K _W · Δz, the above-described design value cam curve is used as the correction amount Δz, Δ
By shifting f, a cam curve (corrected cam curve) for controlling the first movable lens group and the second movable lens group is formed.

The correction amounts Δz and Δf are calculated as follows.

First, the actual cam curve (corrected cam curve) is a function F (z), and the design value cam curve is a function f (z).
And

The telephoto end F _T and the wide-angle end F _W, which are observation points, are expressed as F _T = F (Z _T ) = f (Z _T + Δz) −Δf Equation (1) F _W = F (Z _W ) = f (Z _W + Δz) −Δf Equation (2) By drawing each side of Equations (1) and (2) and expanding to the first order, F _T −F _W = f (Z _T + Δz) −f (Z _W + Δz) ) = F (Z _T ) + f ′ (Z _T ) Δz−f (Z _W ) + f ′ (Z _W ) Δz = f _T −f _W + (K _T −K _W ) Δz When solving for Δz, Δz = ｛ _{(f T -f W) - (} F T -F W)} / (K W -K T) equation (2) extending to a first order, and solving for _{Δf, F W = f (Z} W) + f '(Z _W ) Δz-Δf Therefore, Δf = (f _W -F _W ) + K _W · Δz where Δz: shift amount of the variator 3 (correction amount) Δf: shift amount of the compensator 5 (correction amount) F _T : Design of telephoto end of compensator 5 Location F _W: design in the wide-angle end of the compensator 5 f _T: If the telephoto end of the compensator 5 focus position f _W: if the wide-angle end of the compensator 5 focus position Z _T: Design the telephoto end of the variator 3 Z _W: The design position of the variator 3 at the wide-angle end K _T : the inclination of the design telephoto end K _W : the inclination of the design wide-angle end The variator 3 is formed based on the corrected cam curve formed by shifting the correction amount Δz and Δf. The compensator 5 is controlled.

The control of the variator 3 and the compensator 5 is performed by adding the correction amount Δz to the data indicating the design position of each of the variator 3 and the compensator 5 in the ideal lens system for focusing at each magnification from the wide angle end to the telephoto end. , Δf are stored in a memory, and this is used as a map.

The flange back adjustment is performed on the design value cam curve at a certain object distance, and the calculated correction amounts Δz and Δf of the variator 3 and the compensator 5 are used to correct the design value cam curve at another arbitrary object distance. Amount. This is because, when the variator 3 and the compensator 5 are moved on the basis of the design value cam curve, the focus is shifted mainly due to the arrangement of the position sensors for mainly detecting the positions of the variator 3 and the compensator 5. This is due to the mounting dimensional tolerance of the position, and if the actual mounting position of each position sensor is different from the designed position, it will appear as a common deviation in each of the design value cam curves at a plurality of arbitrary object distances. .

According to the focus adjustment method (flyback adjustment method) of the zoom lens apparatus according to the present invention,
Since the corrected cam curve is formed by moving the design value cam curve in parallel, the corrected cam curve is not deformed, and the respective moving amounts of the variator 3 and the compensator 5 from the telephoto end to the wide-angle end are equal to the design moving amount. It will not change.

In the four-unit zoom lens apparatus, the variator 3 is a first movable lens group described in the claims, the compensator 5 is a second movable lens group, and the variator 3 is a design telephoto end or a design wide-angle end. after fixing go to, by moving the compensator 5, each of the focus position f _T, because the measure f _W, each focus position f _T, the detection of f _W can facilitate .

That is, as can be seen from the inclination of the graph line in FIG. 6, the displacement of the variator 3 and the compensator 5 at the design telephoto end and the design wide-angle end is larger in the variator 3 and, therefore, the in-focus position is detected. This is because it is easier to detect the focal point by moving the compensator 5 after fixing the variator 3 first.

The present invention is not limited to this. The compensator may be fixed at the designed telephoto end and the designed wide-angle end first, and then the focus position where the variator is moved may be detected.

In the embodiment shown in the drawings, the present invention is applied to a focus adjustment method of a zoom lens device of a video camera. However, the present invention is not limited to this, and is applicable to a zoom lens device of a still camera. The present invention can also be applied to a focus adjustment method.

Further, in the above embodiment, the description has been given of the case where the present invention is applied to the four-unit zoom lens device.
Of course, the present invention can be applied to a group zoom lens device.

[0047]

As is apparent from the above description, according to the first aspect of the present invention, (1) the telephoto end in the first movable lens group calculated from the design value of the ideal lens system. (Design telephoto end of first movable lens group)
After moving the movable lens group, the second movable lens group is moved to measure the focal point (f _T ), and (2) the wide-angle end (the first angle) of the first movable lens group calculated from the design value After moving the first movable lens group to the design value of the movable lens group (the wide-angle end), the second movable lens group is moved to focus (f _W ).
And (3) the position of the second movable lens group at the telephoto position (designed telephoto position of the second movable lens group) in the second movable lens group calculated from the design value is set as F _T , The position of the second movable lens group at a wide-angle position in the second movable lens group calculated from the value (design wide-angle position of the second movable lens group) is F _W, and the first value obtained from the design value is F _W.
The inclination in the design telephoto position of the movable lens group and the second graph line representing the positional relationship between the movable lens group (design value cam curve) and K _T, the slope of the design wide angle position as K _W, first of Correction amount of movable lens group (Δz) Δz = {(f _T −f _W ) − (F _T −F _W )} / (K _W −K _T ) Correction amount of second movable lens group (Δf) Δf = Assuming that (f _W -F _W ) + K _W · Δz, the above-described design value cam curve is used as the correction amount Δz, Δ
Since the cam curve (the corrected cam curve) for controlling the first movable lens group and the second movable lens group by shifting f is formed, the corrected cam curve is formed without deforming the design value cam curve. As a result, it is possible to secure a movement amount capable of sufficiently exerting the function of each movable lens group, and it is possible to exhibit a function as designed as a zoom lens device.

Further, the corrected cam curve can be formed only by detecting the two points at the telephoto end and the wide-angle end, and the adjustment time can be reduced.

It should be noted that the specific shapes and structures of the respective parts shown in the above embodiments are merely examples of the embodiment of the present invention, and the technical scope of the present invention is not limited thereto. Should not be interpreted restrictively.

[Brief description of the drawings]

FIG. 1 together with FIGS. 2 and 3 show an embodiment of a focus adjustment method for a zoom lens device according to the present invention, which is a schematic diagram of a zoom lens device.

FIG. 2 is a graph showing design movement trajectories of a first movable lens group and a second movable lens group.

FIG. 3 is a graph showing a relationship between respective movement trajectories of a first movable lens group and a second movable lens group.

FIG. 4 is a schematic view of a conventional zoom lens device.

FIG. 5 is a graph showing a design movement locus of a first movable lens group and a second movable lens group in a conventional zoom lens device.

FIG. 6 is a graph showing a relationship between respective movement trajectories of a first movable lens group and a second movable lens group in a conventional zoom lens device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Zoom lens apparatus, 3 ... 1st movable lens group (variator), 5 ... 2nd movable lens group (compensator), (DELTA) z ... Shift amount (correction amount) of 1st movable lens group, (DELTA) f ... Shift amount (correction amount) of the second movable lens group, F _T ... The design position of the second movable lens group at the telephoto end,
F _W … design position of the second movable lens group at the wide-angle end, f _T …
Focusing position at the telephoto end of the second movable lens group, f _W ... Focusing position at the wide-angle end of the second movable lens group, K _T … inclination at the design telephoto end, K _W … inclination at the design wide-angle end

Claims (1)

[Claims] 1. It has at least two movable lens groups,
A zoom lens device in which each movable lens group moves individually in one unique direction during zooming in one direction for the same subject distance, and (1) a first lens calculated from a design value of an ideal lens system. After moving the first movable lens group to the telephoto end of the movable lens group (hereinafter referred to as “designed telephoto end of the first movable lens group”), the second movable lens group is moved to focus. (F _T ) is measured, and (2) the first movable lens at the wide-angle end (hereinafter, referred to as “designed wide-angle end of the first movable lens group”) in the first movable lens group calculated from the design value. After moving the lens group, the second movable lens group is moved to measure the focal point (f _W ). (3) The telephoto position (hereinafter referred to as “the Designed telephoto position of movable lens group No. 2). And of the position of the movable lens group and F _T, the wide angle position in the second movable lens group to be calculated from the design value (hereinafter, "second design wide angle position of the movable lens group" hereinafter.) The second movable in The position of the lens group is set to F _W, and a graph line (hereinafter, referred to as a graph) representing the positional relationship between the first movable lens group and the second movable lens group obtained from design values.
It is called “design value cam curve”. ) Is K _{T at} the design telephoto position, and K _W is the inclination at the design wide-angle position.
As, the correction amount of the first movable lens group (Δz) Δz = {(f T -f W) - (F T -F W)} / (K W -K T) correction amount of the second movable lens group (Δf) Assuming that Δf = (f _W −F _W ) + K _W · Δz, the above-described design value cam curve is corrected by these correction amounts Δz, Δ
A focus adjustment of a zoom lens apparatus characterized by forming a cam curve (hereinafter, referred to as a "corrected cam curve") for controlling the first movable lens group and the second movable lens group by shifting f. Method.