JPH06121212A - Camera - Google Patents

Abstract

PURPOSE:To provide a camera in which highly accurate zoom tracking control is attained by an inexpensive device without need of a tracking curve data requiring a large memory capacity. CONSTITUTION:When a control signal for telescopic and wide use zoom switches 12, 13 is inputted to a zoom lens driving section 8 in the zooming operation, the driving section 8 drives a zoom lens 2 based on the control signal. Simultaneously the control signal is also inputted to a zoom tracking control circuit 7 by which zoom tracking control is implemented and a focus lens 4 is extended up to a proper position corresponding to the zoom position. A memory 15 stores each of arithmetic operation equation data used for obtaining a proper extended position for zoom tracking control and control is implemented by reading the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera, and more particularly, to a camera for performing a so-called zoom tracking operation, in which a focus lens is moved to an appropriate position for focusing during zooming operation of a zoom lens.

[0002]

2. Description of the Related Art Conventionally, in many video cameras and the like, the zoom tracking operation is performed during the zooming operation of the zoom lens. FIG. 6 is a diagram showing a change in the focus lens position, which is a proper focus position with respect to the zoom lens position in the zoom tracking operation. In the tracking operation, for each zoom lens position, the focus lens is moved along the curve of FIG.
It is carried out by moving.

FIG. 7 is a diagram showing a conceptual diagram of a general photographing optical system such as the above video camera, in which a subject image of a subject 50 is formed on an image pickup surface of a CCD 52 via a taking lens 51. It shall be. As shown in the figure, the taking lens 51, the front focus position FF, and the rear focus position FB
Is defined as f, and the distance between the image pickup surface of the CCD 52 and the rear focus position FB is defined as D. Further, when the subject distance between the subject 50 and the front focus position FF is L, the relationship of L × D = −f ² (...) (1) is established in this optical system. It should be noted that the subject distance L in the above formula (1) is usually represented by the distance from the lens tip, and the value of L + f should be used originally, but the focal length f is generally about 50 mm. Yes, because it can be ignored for the general subject distance L, the value L for the value L + f
Is used instead.

FIG. 8 is a diagram showing a part of a zoom tracking curve in the above-mentioned optical system, and shows a change of the focusing position of the focusing lens with respect to the focal length. Then, the focal lengths f1 and f2 of the taking lens 51 are
Focusing positions at positions P0 and Q0 for the subject distance ∞ (infinity), positions P1 and Q1 for the subject distance L11, and positions P2 and Q2 for the subject distance L12.
And Further, the focus lens extension amounts with reference to the focusing position P0 at the object distance ∞ at the focal length f1 are D11 and D12. Further, the focusing position Q0 at the object distance ∞ at the focal length f2
D2 is the focus lens extension amount when
1 and D22.

When the above-mentioned formula (1) is applied to each of the above positions, L11 × D11 = −f1 ² ………… (2) L12 × D12 = −f1 ² ……………… … (3) L11 × D21 = −f2 ² ……………… (4) L12 × D22 = −f2 ² ……………… (5) From equations (2) and (3), L11 × D11 = L12 × D12 ············································································ (4), (5) from the equation. Further, since the expressions (6) and (7) are established, D22 / D12 = D21 / D11 ... (8)

Since the above equation (8) is established, a tracking curve for the distance ∞ which is the reference object distance,
In addition, a value of a ratio D21 / D11 of the focus lens extension amount D21 at a predetermined subject distance, for example, the reference lens focal length f2 at L11 to the focus lens extension amount D11 at another focal length f1 (hereinafter, this focus The ratio of the lens moving-out amount is referred to as a moving-out ratio), and a zoom tracking curve as shown in FIG. 6 indicating the necessary moving-out position of each zoom lens is obtained. It is possible to extend the focus lens to the proper focus position during zoom operation.

As a zoom tracking control system using the zoom tracking curve shown in FIG. 6, various systems have been conventionally proposed. For example, "NATIONAL TECHNIC
AL REPORT "(VOL. 37 NO.3 JUN. 1991, P338-344)
The zoom tracking method for the zoom lens of the video camera, described in, reads the table of the zoom tracking curve stored in the memory and interpolates the table to calculate the appropriate amount of movement of the focus lens and perform tracking. is there.

The zoom tracking method based on the above table interpolation will be described in detail. FIG. 9 shows the reference object distance L1 of the zoom tracking curve of FIG.
(= ∞) and the subject distance L2, and further, a tracking curve extracted and shown for a subject distance L3 that interpolates between the distances L1 and L2. The focus lens positions for the subject distances L1, L2 at the zooming position Za are A1, A2, and the focus lens positions for the subject distances L1, L2 at the zooming position Zb are B.
1 and B2. Then, the feeding amounts at the positions A2 and B2 are set to values Db and Dd as shown in the figure. It is assumed that these data are stored in the memory.

Now, it is assumed that the zoom lens is at the position Za and the focus lens is located at the position A3 on the tracking curve of the object distance L3. The position A3 is the focus lens position A1 with respect to the zoom position Za.
It can be relatively defined from the above-mentioned amount of extension Db due to A2 and the amount of extension Da due to the focus lens positions A1 and A3. Therefore, it is assumed that the zoom lens position changes to Zb. Subject distance L1 at the zoom position Zb,
The focus lens positions B1 and B2 of L2 and the amount of extension Dd between two points are obtained from the memory information. The tracking curve of the subject distance L3 is the above-mentioned extension ratio Da /
If the transition is made to hold Db, the position B1
The relative position B3 from the
Is required.

The calculation by the table interpolation is premised on that a certain tracking curve is interpolated at a constant ratio with respect to the two tracking curves sandwiching it. Therefore, it is necessary to set the number of tracking curves to be stored in the memory so as to maintain the accuracy of interpolation.
As an example, a video camera has been proposed that stores eight tracking curves as data. As a proposal other than this video camera, "MITSUBISHI ELE
The camera proposed in "CTRIC ADVANCE" (DEC. 1991, P32-33) stores 12 tracking curves as data.

[0011]

However, the above equation (8), which indicates that the payout ratio is constant, is established more closely to a subject whose incident light on the focus lens is parallel light. Since it holds only for the range,
The farther the incident light on the focus lens is from the parallel distance, the less the payout ratio becomes constant. For example,
As shown in the payout ratio of Table 1 described later, the focal length is 5.
The amount of change greatly changes based on the payout ratio of 15 mm, and the amount of change also changes depending on the subject distance.
In addition, according to the simulation of the lens having the tracking curve shown in FIG. 6, a maximum deviation of 200 μm in the feeding position occurred. It should be noted that with this lens, if there is a deviation of 30 μm, defocusing is felt. In addition, even under a condition in which it is relatively difficult to feel out-of-focus, such as during zooming, only a deviation of 50 μm is actually allowable.

Therefore, the above-mentioned "NATIONAL TECHNICAL REP"
ORT ”(VOL. 37 NO.3 JUN. 1991, P338 to 344) zoom tracking system, in order to satisfy the above conditions, for example, 10 tracking curve data are stored in a memory. Assuming that it has a focal length of 64 steps and the focus lens position is represented by 8-bit data, it requires 64 bytes x 10 lines = 640 bytes, and a large-capacity memory is required for a general video camera. Will be.

Further, in a video camera having a zoom ratio of 10 times or more, which is considered to be the mainstream in the future, it is necessary to increase the number of steps from 64 steps to 256 steps (8 bits) in terms of accuracy, and a memory capacity of 2 is required. You will need a 5K byte product. Such a memory capacity is not practical for a consumer video camera.

The present invention has been made in order to solve the above-mentioned problems, and even if the accuracy of zoom tracking is emphasized, it is not necessary to increase the memory capacity, and the device has a simple structure. An object is to provide a camera capable of performing zoom tracking control.

[0015]

According to one camera of the present invention, when the zoom lens is in the first position corresponding to a predetermined reference zoom magnification, the proper position of the focus lens corresponding to the subject distance is set. A reference extension amount of the focus lens, which is represented as an interval between both positions of the focus lens corresponding to the reference subject distance and an appropriate position, is defined as a first extension amount, and the zoom lens has a second extension different from the first position. When it is in the position, the amount of extension of the focus lens, which is represented as the distance between the proper position of the focus lens corresponding to the subject distance and the proper position of the focus lens corresponding to the reference subject distance, When the feed amount is defined, the value of the feed ratio expressed as the ratio of both the first feed amount and the second feed amount is First predetermined to a second feed amount of
A value obtained by multiplying a value obtained by multiplying a first constant, which is one of the numerical values of the group, by a second value, which is one of the numerical values of the second group.
By a feed-out ratio calculating means for calculating the feed-out ratio as a reference value, and a feed-out ratio calculated by the feed-out ratio calculating means as a reference feed-out amount. A feeding amount calculation means for calculating, a first group numerical data holding means for holding the numerical value data of the first group, and a second group numerical data for holding the numerical value data of the second group A holding means and a reference zoom tracking curve data holding means for holding data representing a zoom tracking curve which is a locus of an appropriate position of the focus lens corresponding to a reference subject distance when moving in a predetermined range of the zoom lens. It is characterized by having.

According to another camera of the present invention, a value of a payout ratio expressed as a ratio of both the first payout amount and the second payout amount is compared with a predetermined group of numerical values. There is a linear correspondence relationship between the extension ratio calculation means for calculating as a value multiplied by the correction coefficient, and the correction coefficient with the second extension amount of the focus lens and the second position of the zoom lens. Correction coefficient calculation means for calculating as a value, numerical data holding means for holding the group of numerical value data, and correction of the focus lens corresponding to the reference subject distance when the zoom lens moves within a predetermined range And a reference zoom tracking curve data holding means for holding data representing a zoom tracking curve which is a locus of a position.

[0017]

In one camera of the present invention, the target extension amount of the focus lens is obtained by the first extension amount and the extension ratio obtained by the extension ratio calculating means, and the focus lens is driven to the target position. Then, the zoom tracking operation is performed.

In another camera of the present invention, the target extension amount of the focus lens is a first extension amount and an extension ratio calculated based on the correction coefficient obtained by the correction coefficient calculation means. Then, the focus lens is driven to the target position to perform the zoom tracking operation.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the essential parts of a video camera according to the first embodiment of the present invention. The main configuration of this camera is a first lens group that is a fixed lens group that constitutes an inner focus type zoom lens, a zoom lens that is a second lens group for zooming, and a third lens group 3 that is a fixed lens group. , A focus lens 4 of the fourth lens group, a CCD 5 for converting an image of the subject 20 into an electric signal, a video circuit 6 for converting an image pickup signal of the CCD 5 into a video signal and outputting the video signal to a recording circuit (not shown), Also, the zoom switches 12 and 13 for instructing the zoom operation in the wide direction, and the zoom switch detection for processing the signals of the zoom switches 12 and 13 and outputting the signals to the zoom lens drive unit 8 or the zoom tracking control circuit 7 described later. The reference zoom tracking curve data is composed of the circuit 14 and the ROM, and corresponds to the subject distance ∞ (infinity) which is the reference subject distance. Data holding means, and, first and second storing first group for obtaining the feed ratio, the VAL1, VAL2 or the like as a value of the second group
The memory 15 including a group numerical data holding means, the zoom tracking control circuit 7 for performing zoom tracking control based on the signals from the zoom switches 12 and 13, and the zoom lens 2 based on the signal from the zoom switch. The zoom lens drive unit 8 to be driven, the zoom encoder 9 that detects the amount of movement of the zoom lens 2 and inputs the signal to the zoom tracking control circuit 7, the zoom tracking control circuit 7, and the AF control circuit. 1
A focus lens drive unit 11 that is a drive unit that drives the focus lens 4 based on the output of 0, and a focus lens drive unit 11 that includes a stepping motor, and a focus circuit that indicates the degree of focus included in the video signal from the video circuit 6. The detection information, for example, the contrast information in the hill climbing focusing method is extracted, and the A of the focus lens is fed to the focus lens driving unit 11.
The AF control circuit 10 outputs an F (auto focus) control signal.

The above zoom tracking control circuit 7
Has a built-in feed ratio calculation means and feed amount calculation means, which will be described later. In addition, the focus lens 4
Since the drive unit 11 is composed of a stepping motor, it is not necessary to detect the moving position of (1), so that the encoder for the focus lens is unnecessary.

Next, the zooming operation in the camera of the present embodiment configured as described above is executed based on the operation signal of the zoom switches 12 and 13 for tele and wide. That is, when the signal is input to the zoom lens drive unit 8, the drive unit 8 drives the zoom lens 2 based on the operation signal. When the zoom encoder 9 detects that the zoom lens 2 has reached the wide or tele end, the drive unit 8 stops its driving operation. At the same time, the operation signals of the zoom switches 12 and 13 are also input to the zoom tracking control circuit 7 to perform the tracking control described later, and the focus lens 4 is extended to an appropriate position corresponding to the zoom position. Then, the zoom tracking control circuit 7
The zoom lens position information ZO from the zoom encoder 9 and the focus lens position information FO from the focus lens driving unit 11 are always taken in. In addition,
In the present embodiment, the third lens group is fixed,
The focus lens 4 may be moved so as to assist in accordance with the function of the zoom lens 2.

The focusing operation of the focus lens 4 itself is executed by the AF control circuit 10 according to the focus detection information extracted from the video signal. That is, AF
The focus position of the focus lens 4 is calculated by the control circuit 10 based on the focus detection information, and the focus lens 4 is driven to the focus position via the focus lens drive unit 11.

Next, the zoom tracking control of the camera of this embodiment will be described. FIG. 2 is a diagram showing an example of a zoom tracking curve with respect to a reference subject distance ∞ and a certain subject distance L0. In this tracking curve, when the zoom lens 2 is at the reference wide-end position W that is the first position, the amount of extension of the focus lens 4 from the extension position corresponding to ∞ distance is the reference amount of extension as the first amount of extension. Let be Dk. Then, the zoom lens 2 is at the second zoom position Z, which is the second position.
The amount of extension of the focus lens 4 from the extension position corresponding to the distance ∞ when it changes from O1 to ZOn is defined as the second extension amount D1 to Dn. It should be noted that the positions FO1 to FOn indicate the extended positions of the focus lens 4 when the zoom tracking drive is performed.

Therefore, the above-mentioned respective feeding amounts D1 to Dn,
Feeding ratio Dk / D, which is the ratio with reference feeding amount Dk
When n is measured, for example, the data shown in Table 1 is obtained. This Table 1 shows a change in the value Dk / Dn at each focal length for each subject distance, with a focal length of 5.15 mm at the wide end position.

[0025]

[Table 1] The value of the extension ratio Dk / Dn in Table 1 changes depending on each focal length and the subject distance, but is 1 for the reciprocal of the subject distance (diopter).
It is the next function. Since the feed amount Dk from the feed position corresponding to the above ∞ distance is proportional to the diopter from the above equation (1), the value of the feed ratio Dk / Dn can be approximated by a linear expression for the feed amount Dn. It is possible. That is, the value of the extension ratio Dk / Dn is VAL1 which is the numerical data of the first group and changes with each focal length.
And using VAL2 which is the numerical data of the second group, Dk / Dn = VAL1 × Dn + VAL2 ....
It can be shown in the form of (9). VAL1 and VAL2 are values that change depending on the zoom lens position, that is, the focal length, and the above equation (9) is given in Table 2 below for each focal length.
Given as shown in.

[0026]

[Table 2] In the camera of this embodiment, the memory 15 has the V
The memory 15 includes AL1 as first group numerical data corresponding to each zoom lens position, and VAL2 as second group numerical data corresponding to each zoom lens position.
To store. Then, at the time of zoom tracking control, the numerical data VAL1 and VAL2 at the corresponding zoom lens position are read out, and the value of the feeding ratio Dk / Dn is obtained by the arithmetic expression of the expression (9).

Further, in the camera of this embodiment, the extended position data ∞DATA (ZO) of the proper focus lens 4 which is the reference zoom tracking curve data at each zoom lens position ZO1 to ZOn at the reference object distance ∞.
n) is also stored in the memory 15.

When zoom tracking control is performed, the value Dk0 / Dn0, which is the extension ratio in the initial operation, is calculated from Dn0 which is the extension amount in the initial operation and the values VAL1 and VAL2 stored in the memory 15. Ask for. Further, the feeding ratio Dk / Dn0 and the feeding amount Dn0
From the above, the reference extension amount Dk in the initial state is obtained. Subsequently, when the zoom lens position is changed, the payout ratio Dk / Dn for the changed zoom lens position ZOn is obtained from the numerical data VAL1 and VAL2, and the target is calculated from the value of the payout ratio and the reference payout amount Dk. Then, the extension amount Dn of the focus lens is calculated. Then, the feed-out position data ∞DATA (ZOn) stored in the memory 15 is added to the feed-out amount Dn to calculate the target proper focus position of the focus lens 4, and the data signal is focused. Lens drive unit 1
Output to 1, and the zoom tracking operation ends.

Next, the zoom tracking operation of the camera of this embodiment will be described in more detail with reference to the zoom processing flowchart of FIG. Zoom switch 12,
Alternatively, when 13 is pressed and the zoom process is started, first, in steps S11 and S12, the data of the initial focus lens position FO1 and the initial zoom lens position ZO1 is taken into the zoom tracking control circuit 7.

At step S13, the amount of extension ∞DATA (ZO1) at the initial focus lens position FO1 and the reference subject distance (∞) stored in the memory 15 is set.
Then, the amount of extension D1 is obtained from
AL1 and VAL2 are read out, and the feed ratio Dk / D1 with respect to the feed amount D1 is obtained based on the above equation (9). Then, in step S15, the reference extension amount Dk for the initial state is calculated. The zoom lens position corresponding to this reference extension amount Dk is the wide end W.

In step S16, the moving zoom lens position ZO2 when the zoom lens 2 is moved by operating the zoom switches 12 and 13 is input. continue,
In step S17, the values VAL1 and VAL2 corresponding to the zoom lens position ZO2 are read out, and the feed ratio Dk with respect to the feed amount D2 at the current zoom position ZO2.
/ D2 is calculated. However, as the feed amount D1 on the left side of the arithmetic expression of this step, originally the feed amount D2 must be used, but since the value D2 is undetermined at this time, the feed amount D1 is used here. Further, as will be described later, when the zoom drive is continued to update the zoom position and the process is repeated, the extension amount Dn-1 at the zoom position obtained immediately before is used. In the case of the present camera, the error for this is divided into 64 steps from the wide end position W to the tele end position T, so even if the immediately preceding value is used in this way, a large error does not occur.

In step S18, the zoom lens position ZO2 is calculated from the above-mentioned extension ratio Dk / D2 and the reference extension amount Dk in the initial state obtained in step S15.
The target feed amount D2 corresponding to is calculated. Further, in step S19, the target focus lens position FO
2 to the above-mentioned target extension amount D2 and the zoom lens position Z
Extending amount ∞DAT for the reference object distance ∞ at O2
It is calculated by adding A (ZO2). And step S2
At 0, the data of the target focus lens position FO2 is output to the focus lens drive unit 7.

In step S21, whether the zoom switches 12 and 13 are pressed to update the zoom position is confirmed by the change in the output value of the zoom encoder 9. Then, if the switch is not operated and the zoom position is not updated, this routine is ended as it is. If it is updated, the process returns to step S16, and the target focus lens movement position for the updated next zoom lens position ZOn. The operation of FOn is executed. However, the suffix 1 or 2 shown in steps S16 to S20 is incremented each time the process is repeated.

As described above, in the video camera of this embodiment, the focus lens position data corresponding to each zoom lens position ZOn at the reference subject distance (∞) is the storage data necessary for zoom tracking. Some ∞DATA (ZOn) and each zoom lens position Z
Data group VAL1 and data group VAL2 corresponding to On
In comparison with the conventional method of interpolating the zoom tracking curve to obtain the extension amount, the memory 1
The storage capacity of 5 is reduced, and more accurate zoom tracking can be performed.

In the camera of the present embodiment, the zoom lens position corresponding to the reference extension amount Dk for obtaining the extension ratio is the wide end W, but a different zoom position may be designated as this position. Furthermore, the focus lens 4
Although the data of the subject distance ∞ is adopted as the reference of the feeding position, the tracking curve at another subject distance can also be applied as the reference data of the feeding position.

Next, a video camera according to the second embodiment of the present invention will be described. The camera of this embodiment is different from that of the first embodiment in the method for obtaining the target extension amount in the zoom tracking control, and the basic configuration of the camera is different from that of the first embodiment. Absent. However, the memory 15A shown in FIG. 1 is used as the tracking control memory. The memory 15A stores focus lens position data (∞DATA, which will be described later) corresponding to each zoom lens position at the reference subject distance (∞).
(ZOn), a group of numerical values (KHDATA (ZOn)), which will be described later, indicating the payout ratio corresponding to each zoom lens position at a predetermined subject distance, and an arithmetic expression, which will be described later, regarding the correction coefficient hn are stored. As the zoom tracking control circuit, the zoom tracking control circuit 7A shown in FIG. 1 is also used, and the circuit 7A incorporates a feed-out ratio calculating means and a correction coefficient calculating means, which will be described later.

Here, the payout ratio Dk / Dn shown in Table 1 above.
With respect to the above, when the change in the feed-out ratio based on the value of the feed-out ratio at the distance of 1 m, which is the predetermined subject distance, is obtained, the values shown in Table 3 are obtained.

[0038]

[Table 3] Each value in Table 3 above corresponds to the correction coefficient hn. For example, when a payout ratio at a subject distance of 1.7 m at a focal length of 25.45 mm is to be obtained, Table 3 shows that 0.973 as the correction coefficient h
Is required. On the other hand, the standard focal length is 25.45 m
Table 1 shows the extension ratio when the subject distance is 1 m in m.
Therefore, 4.87 × 10 ^-2 is required. By multiplying the payout ratio 4.87 × 10 ^-2 by 0.973 of the correction coefficient h, an accurate payout ratio under the above conditions can be obtained.

Then, in the tracking control of the camera of this embodiment, the following linear expression, Dk / Dn = hn.times.KHDATA (ZOn), is used as an arithmetic expression for obtaining the payout ratio Dk / Dn ....
……… (10) shall be applied. Here, hn is a correction coefficient which is a coefficient having a linear correspondence relationship between the focus lens extension amount Dn which is the second extension amount and the zoom lens position ZOn which is the second position. Also, KHDATA
(ZOn) is a zoom lens position ZOn at a predetermined subject distance described later, for example, at a subject distance of 1 m in Table 1.
Is a group of numerical values showing the delivery ratio Dk / Dn corresponding to.

As a linear expression for satisfying the value of each correction coefficient hn in Table 3, hn = α × Dn + β ………………………………
... (11) is used. However, the coefficient values α and β are both values corresponding to the zoom lens position. In particular, the value β can be approximated by the following equation. That is, β = 1.396-0.02837 × ZOn ………………
… (12) The following Table 4 shows the arithmetic expression of the correction coefficient hn of the above equation (11) in correspondence with each zoom lens position.

[0041]

[Table 4] As can be seen from Table 3 above, when the focal length is 17 mm or less, the value of the correction coefficient hn does not change so much and can be approximated to the value 1. Further, when the focal length is 25.45 mm or more, the value of the coefficient α in Expression (11) can be approximated to 0.07.

Therefore, in the camera of this embodiment, when the movement amount of the zoom lens 2 corresponding to the intermediate position between the focal lengths of 17 mm and 25.45 mm is set to 15 mm and the distance is less than that, the value of the correction coefficient hn is set to 1. Fixed to. Also, the movement amount is 15 mm
In the above case, the value of the coefficient α is set to 0.07, the coefficient β is set to the value of the above expression (12), and the following correction coefficient hn expression is applied. That is, hn = 0.07.times.Dn + 1.396-0.02837.times.ZOn (13), and the payout ratio is calculated by the equation (13).

In the camera of this embodiment, the data stored in the memory 15A for tracking control is as follows.
As shown in FIG. 1, ∞DATA (ZOn) which is focus lens position data corresponding to each zoom lens position ZOn at the reference subject distance (∞) and, for example, each zoom lens position ZOn at a subject distance of 1 m shown in Table 1. KH which is a group of numerical values showing the delivery ratio Dk / Dn corresponding to
Calculation formula (13) of DATA (ZOn) and the correction coefficient hn
Etc. are stored. Then, an appropriate extension position of the focus lens 4 at the time of zoom tracking control is obtained based on each of the above data stored in the memory 15A.

Next, the zoom tracking processing operation of the camera of this embodiment will be described in detail with reference to the zoom processing flowcharts of FIGS. It should be noted that a part of the same processing as the processing of the first embodiment is included. As shown in FIG. 4, the zoom switch 12 or 13 is pressed to start the zoom process, but the processes in steps S31 to S33 are the same as those in the first embodiment.

In step S34, the zoom lens 2
Is detected by the zoom encoder 9, and it is checked whether the value is 15 mm or more indicating the boundary position. If the amount of movement is less than 15 mm, the process jumps to step S37, the correction coefficient hn is fixed to the value 1, and the value corresponds to the moving zoom lens position ZO1.
The above-mentioned value KHDATA (ZO1) read from A is set as it is as the feeding ratio Dk / D1 and the process proceeds to step S38 which will be described later. If the amount of movement is 15 mm or more, the process proceeds to step S35 to perform the calculation based on the equation (13) to obtain the correction coefficient h1. Further, in step S36, the correction coefficient h1 and the memory 15A are
The feeding ratio Dk / D1 in the initial state is obtained from the value KHDATA (ZO1) read from Then, the process proceeds to step S38.

In step S38, the reference feed-out amount Dk in the initial state is obtained from the feed-out ratio Dk / D1 obtained in the above process and the feed-out amount D1. continue,
In step S39 shown in FIG. 5, the moving zoom lens position ZO2 is input as in the case of the first embodiment. In step S40, it is checked whether the movement amount of the zoom lens 2 is 15 mm or more. If the amount of movement is less than 15 mm, jump to step S43 and set the correction coefficient hn to 1
Is a value corresponding to the moving zoom lens position ZO2 and is the value KH read from the memory 15A.
DATA (ZO2) is set as it is as the feeding ratio Dk / D2, and the process proceeds to step S44. If the amount of movement is 15 mm or more, the process proceeds to step S41 to perform the calculation based on the equation (13) to obtain the correction coefficient h2. In this case, the delivery amount Dn in the equation (13)
However, the amount of extension D2 should be applied, but since it is undetermined at this time, the amount of extension at the immediately preceding zoom lens position, in this case, the value D1 is used to calculate the correction coefficient h2. The problem of accuracy with respect to this point is the same as in the case of the first embodiment described above.

Further, in step S42, the correction coefficient h2
And the value read from the memory 15A KHDATA (ZO
2) and the payout ratio Dk / D2. Then, the process proceeds to step S44 and subsequent steps, but these processes are performed by the first
In the same processing as that of the embodiment, when the target focus lens position FO2 and the zoom position are updated, data such as FOn is output to the focus lens driving unit 11, and the focus lens 2 is It is driven to the target proper position.

As described above, also in the video camera of the present embodiment, more accurate zoom tracking operation can be performed within a relatively small memory capacity range, as in the camera of the first embodiment. That is, ∞DAT which is focus lens position data at the reference subject distance (∞)
Only A (ZOn), KHDATA (ZOn), which is a group of numerical values showing the extension ratio Dk / Dn corresponding to each zoom lens position ZOn at a subject distance of 1 m, and the arithmetic expression (13) of the correction coefficient hn are stored in the memory 15A It is possible to perform highly accurate tracking control simply by storing in the memory.

Also in the camera of this embodiment, the zoom lens position corresponding to the reference extension amount Dk for obtaining the extension ratio is the wide end W, but another zoom position may be designated. Further, although the data of the subject distance ∞ is adopted as the reference of the extending position, the present invention is not limited to this, and the reference data at other subject distances may be applied, as in the case of the first embodiment. . Further, a group of numerical values KHDATA (ZOn) showing the above-mentioned payout ratio Dk / Dn
The subject distance is not limited to 1 m and may be data at another position.

The present embodiment and the first embodiment have been applied to a video camera, but of course the gist of the present invention is zoom tracking of other still video cameras and cameras for silver halide films. It can also be applied to control.

[0051]

As described above, according to the camera of the present invention, the required amount of extension of the focus lens in the zoom tracking operation is set to one reference tracking curve data and the focus corresponding to the reference focal length on a predetermined subject distance. Lens extension amount and extension ratio at each focal length,
Alternatively, since the determination is made by applying the correction coefficient or the like, unlike the conventional data-interpolation type zoom tracking control of a camera, tracking curve data with a large memory capacity is not required, and high-speed calculation is also possible. In addition, the zoom tracking control with high accuracy becomes possible with an inexpensive device, which has many remarkable effects.

[Brief description of drawings]

FIG. 1 is a main block configuration diagram of a video camera according to a first embodiment of the present invention.

2 is a diagram showing an example of a zoom tracking curve applied to zoom tracking processing of the video camera shown in FIG. 1;

FIG. 3 is a flowchart of zoom processing of the video camera shown in FIG.

FIG. 4 is a part of a flowchart of a zoom process of the video camera according to the second embodiment of the present invention.

FIG. 5 is a part of a flowchart of zoom processing of the video camera in FIG.

FIG. 6 is an example of a zoom tracking curve applied to zoom tracking control of a conventional video camera.

FIG. 7 is a diagram showing an optical system of a conventional video camera.

FIG. 8 is a diagram showing a method of obtaining a focus lens extension amount in zoom tracking control of a conventional video camera.

FIG. 9 is a diagram showing a method of obtaining a focus lens extension amount in zoom tracking control using a data interpolation method of a conventional video camera.

[Explanation of symbols]

2 …………………… Zoom lens 4 …………………… Focus lens 7 …………………… Zoom tracking control circuit (extend ratio calculation means, extension amount calculation means) 15 ……… ............ Memory (numerical data holding means for the first group, numerical data holding means for the second group, reference zoom tracking curve data holding means) 7A …………………… Zoom tracking control circuit (extending ratio calculation means) , Correction coefficient calculation means) 15A ............... memory (numerical data holding means, reference zoom tracking curve data holding means) W ... ……………………………… wide end position (first Position) ZO2 to ZOn ………………… Zoom lens position (second
Position) FO2 to FOn …………… (appropriate position of the focus lens) Dk …………………………………… Reference focus amount of the focus lens (first extension amount) D1 to Dn… …………………… Focus lens extension amount (second extension amount) Dk / Dn …………………… (extend ratio) VAL1 …………………… (First group Value) VAL2 …………………… (second group value) ∞DATA (ZOn) ………… (reference zoom tracking curve data) h1, h2, hn …………… (correction coefficient) KHDATA (ZOn) ... (A group of numerical data)

Claims (2)

[Claims] 1. A proper position of a focus lens corresponding to the subject distance and a proper position of the focus lens corresponding to the reference subject distance when the zoom lens is at a first position corresponding to a predetermined reference zoom magnification. The reference extension amount of the focus lens, which is represented as the interval between the two positions, is defined as the first extension amount, and corresponds to the subject distance when the zoom lens is in the second position different from the first position. When the amount of extension of the focus lens, which is represented by the distance between the appropriate position of the focus lens and the appropriate position of the focus lens corresponding to the reference subject distance, is the second extension amount, the first extension amount is The value of the feed-out ratio, which is expressed as the ratio of both the feed-out amount and the second feed-out amount, is set to the second feed-out amount by a predetermined numerical value of the first group. A feed-out ratio calculation means for calculating as a value obtained by multiplying a value obtained by multiplying a first constant which is one of the two by a second constant which is one of the numerical values of the predetermined second group, A feed-out amount calculation means for calculating a required feed-out amount of the focus lens by a first feed-out amount which is the reference feed-out amount and a feed-out ratio calculated by the feed-out ratio calculation means, and a numerical value of the first group. First group numerical data holding means for holding data, second group numerical data holding means for holding numerical value data of the second group, and a reference subject when moving within a predetermined range of the zoom lens. A reference zoom tracking curve data holding means for holding data representing a zoom tracking curve which is a trajectory of an appropriate position of the focus lens corresponding to the distance, A camera characterized by having. 2. A proper position of the focus lens corresponding to the subject distance and a proper position of the focus lens corresponding to the reference subject distance when the zoom lens is at the first position corresponding to a predetermined reference zoom magnification. The reference extension amount of the focus lens, which is represented as the interval between the two positions, is defined as the first extension amount, and corresponds to the subject distance when the zoom lens is in the second position different from the first position. When the amount of extension of the focus lens, which is represented by the distance between the appropriate position of the focus lens and the appropriate position of the focus lens corresponding to the reference subject distance, is the second extension amount, the first extension amount is The value of the payout ratio, which is expressed as the ratio of both the payout amount and the second payout amount, is multiplied by the correction coefficient for a predetermined group of numerical values. And a correction ratio calculating means for calculating the correction coefficient as a value having a linear correspondence relationship between the second extension amount of the focus lens and the second position of the zoom lens. Correction coefficient calculation means, numerical data holding means for holding the group of numerical value data, and a locus of the correction position of the focus lens corresponding to the reference subject distance when the zoom lens moves within a predetermined range. A camera comprising a reference zoom tracking curve data holding means for holding data representing a zoom tracking curve.