JP2757592B2 - Camera system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera system suitable for a television camera, a video camera, and a photographic camera for 35 mm film, and more particularly to a plurality of lens groups which can move independently during zooming and focusing. The present invention relates to a camera system having a rear focus type zoom lens.

[0002]

2. Description of the Related Art Conventionally, a zoom lens used in a television camera, a video camera, a photographic camera, or the like employs a so-called rear focus type in which a lens group other than the first group on the object side is moved to perform focusing. Various proposals have been made.

In general, a rear focus type zoom lens has a smaller effective diameter of the first lens group than a zoom lens which moves and focuses the first lens group, so that the entire lens system can be easily miniaturized, and close-up photography can be performed. In particular, extremely close-up photographing is facilitated, and since the relatively small and light lens group is moved, the driving force of the lens group is small, so that quick focusing can be performed.

FIG. 9 shows a partial lens group 55 or a whole lens group 5 of a relay lens 53 behind a conventional variable power system.
FIG. 3 is an optical schematic diagram of a so-called rear focus type zoom lens in which focusing is performed by moving the zoom lens 3.

FIG. 9 shows a lens group 51 and a lens group 54.
(R) is fixed, and the lens group 52 (V) as a variator changes its position in the optical axis direction by adjusting the focal length. Also, a part of the lens group 55 (RR
The lens (lens) has both the role of correcting the image plane fluctuation at the time of zooming and the role of focusing.

FIG. 10 shows the position of the lens group 52 (V) on the horizontal axis, that is, the zoom position, and the vertical axis on the optical axis when the lens group 55 (RR lens) focuses on the zoom lens of FIG. It is explanatory drawing at the time of taking a position.

In the lens configuration shown in FIG. 9, it is necessary to change the position of the lens group 55 (RR lens) on the optical axis both when the subject distance changes and when the focal length (zoom position) of the zoom lens changes. .

[0008] Such a rear focus type zoom lens is proposed in, for example, Japanese Patent Publication No. 52-15226. In this publication, the position on the optical axis of the zooming lens group and the focusing lens group which also has a function as a compensator when zooming is performed is detected by the detecting means. Next, the position on the optical axis of the focusing lens group that is in focus is calculated by the calculating means from the position information of both lens groups at this time. A zoom lens has been proposed in which a focus lens group is driven and controlled by a motor or the like based on the calculation result.

In Japanese Patent Application Laid-Open No. 60-143309, the positions of the variator lens group and the compensator lens group having a focusing function on the optical axis are stored in the storage means in relation to the position of the variator lens group. . Then, a zoom lens has been proposed in which the position of the compensator lens group is read out from the storage means in accordance with the position of the variator lens group, and the driving of the compensator lens group is controlled.

[0010]

In general, in a rear focus type zoom lens, the position on the optical axis of a focusing lens group is variously changed due to zooming even if the object distance is constant as shown in FIG. Come. For this reason, it is important to drive and control the focusing lens group and the focusing lens group on the optical axis with high precision along with the magnification change.

In a high definition television camera or the like that requires particularly high optical performance, it is important to drive and control the position of each lens group on the optical axis with high accuracy.

However, in general, it is difficult to control the driving of each lens group at a predetermined position on the optical axis with good accuracy mechanically and electrically. In many cases, a control error occurs, and the image forming position becomes poor. There is a problem that the optical performance is reduced due to displacement.

According to the present invention, the position on the optical axis of each lens group is stored in advance in the memory means based on the focal length setting means, the object distance setting means, or the setting value input from both setting means. It is calculated by using the position information on the object distance, and the imaging position error generated from the difference between the obtained value and the position on the optical axis of each lens group after actually driving each lens group is calculated. It is an object of the present invention to provide a camera system capable of always obtaining a good image on an image forming plane by moving and correcting one appropriately selected lens group for each zoom position.

[0014]

SUMMARY OF THE INVENTION A camera system according to the present invention performs zooming by moving a zooming unit including a plurality of lens units on an optical axis, and at least a part of the lens units of the zooming unit. In a camera system having a zoom lens configured to perform focusing by moving a focusing unit including on the optical axis, a focal length setting unit for inputting focal length information;
Object distance setting means for inputting object distance information; detecting means for detecting the focal distance information or / and the object distance information; and detecting the focal distance information and the object distance information based on a detection signal from the detecting means. Calculating means for selecting corresponding position information from a memory unit in which position information on the optical axis of each lens group is recorded, and calculating the position on the optical axis of each lens group using the position information; A lens position control means for driving the drive unit based on the signal from the lens unit to move each lens group, a value from the position detection unit for detecting the position of each lens group on the optical axis, and a value obtained by the arithmetic means Position error calculating means for calculating a difference between the position error calculating means, a selecting means for selecting a lens group for correcting an image forming position error based on a signal from the calculating means, and an image forming position using an output signal from the position error calculating means. Select to correct errors Correction value calculating means for calculating the position on the optical axis of the lens group selected in the step, wherein the lens position control means drives the driving unit based on an output signal from the correction value calculating means, and It is characterized in that the lens group is moved on the optical axis.

[0015]

FIG. 1 is a schematic view of a main part of a camera system according to a first embodiment of the present invention. In the figure, SL denotes a zoom lens body (also referred to as a zoom lens), and CA denotes a camera body. The zoom lens SL has three lens groups 8a, 8b, 8c. At the time of zooming and focusing, at least two of the three lens groups 8a to 8c move independently or in a fixed relationship on the optical axis.

Reference numerals 10a to 10c denote position detectors, which detect the positions of the lens groups 8a to 8c on the optical axis and input the position information to position error calculating means 11a, 11b, 11c. The position error calculating means 11a, 11b, 11c calculates the position of each lens group on the optical axis calculated by the calculating means 6 and the actual position of each lens group on the optical axis detected by the position detecting units 10a, 10b, 10c. The difference (position error) is calculated and input to the correction value calculating means 12.

Reference numerals 9a to 9c denote lens driving units which drive the respective lens groups 8a to 8c based on driving signals from lens position control means 7a to 7c. The position information on the optical axis of each lens group obtained by the arithmetic unit 6 is input to the lens position control units 7a to 7c.

Reference numeral 13 denotes a selecting unit, which selects a lens group for which an image forming position error is to be corrected based on a signal from the calculating unit 6,
The most preferable lens group is also selected from the plurality of lens groups 8a to 8c at the zoom position.

In this embodiment, as a selection criterion of a lens group selected by the selection means 13, for example, at the zoom position where the lens is moved during focusing and an imaging position error is to be corrected, the sensitivity is the smallest among the lens groups. The lens group is selected based on a signal from the calculating means 6.

The current zoom position is obtained based on the position information from the other position detectors 10a to 10c, and the information from the memory unit 4 in which the sensitivity is recorded for each zoom position is used. A lens group with low sensitivity may be selected.

Numeral 12 is a correction value calculating means, which is a selecting means for correcting an imaging position error caused by a position error of the lens groups 8a, 8b, 8c using output signals from the position error calculating means 11a, 11b, 11c. The position on the optical axis of the lens group selected in 13 is calculated, and the calculated result is input to the lens position control means.

In the figure, the lens group 8b is
Alternatively, the case where the lens group 8c is selected and the lens group 8b or the lens group 8c is moved to correct the imaging position error has been described, but the correction may be performed using another lens group 8a. 2
The correction may be performed by selecting one lens group and moving it at a fixed ratio.

Reference numeral 1 denotes a focal length setting means, which inputs zoom position information (focal length information) of the zoom lens SL by a zoom operation. Reference numeral 2 denotes an object distance setting unit which inputs object distance information (focus information). Reference numeral 3 denotes a detector, which includes a focal length setting unit 1 and an object distance setting unit 2
CPU 6 as input means for detecting input information from
Is being entered. Reference numeral 4 denotes a memory unit, which comprises a ROM or the like. The memory unit 4 stores the position on the optical axis of each of the lens groups 8a to 8c with respect to the zoom position and the object distance of the zoom lens as C.
Coefficients (position coefficients) for calculation by the PU 6 are stored.

FIG. 2 shows the coefficient (a) stored in the memory unit 4._{i, j}  
 , B_{i, j} , C_{i, j}FIG. As shown in the figure
Each lens group when the focal length and object distance are taken as variables
In order to calculate the position on the optical axis based on the formula described later,
The focal length (magnification position) is plotted on the x-axis and the object distance is plotted on the y-axis.
Is shown. Then, divide each of them into multiple areas,
A coefficient is stored for each area. 5 contains a program
ROM.

The CPU 6 selects the focal length information and the object distance information from the detecting means 3 and predetermined coefficients from the memory unit 4, and uses these values to determine the positions of the lens groups 8a to 8c on the optical axis in the program 5. Is calculated based on The calculation results are input to lens position control means 7a to 7c. The lens position control means 7a to 7c include driving units 9a to 9c.
9c is driven to move each of the lens groups 8a to 8c on the optical axis.

At this time, as described above, each lens group 8a,
The positions on the optical axis of 8b and 8c are determined by the position detection units 10a and 10c.
b, 10c, the position error calculating means 11a, 11
b, 11c. Position error calculating means 11a,
In 11b and 11c, the difference from the value input from the calculating means 6 is calculated, and the result is input to the correction value calculating means 12, respectively. The correction value calculating means 12 obtains an imaging position error based on these values using the paraxial refractive power arrangement and sensitivity of each lens group, and selects the correcting means 13 to correct the imaging position error.
The position on the optical axis of the lens group (the lens group 8b or the lens group 8c in the present embodiment) selected in (1) is calculated using, for example, sensitivity or the like, and the signal is calculated by the lens position control means (7b or 7c). Is being entered.

The lens position control means (7b or 7c) is driven by the drive unit (9b,
The lens group (8b, 8c) is moved on the optical axis by 9c). As a result, based on the input information from the focal length setting means 1 and the object distance setting means 2, the driving of each of the lens groups 8a to 8c constituting the zoom lens is controlled with high precision, and a good image is obtained.

FIG. 3 is a schematic diagram showing the position on the optical axis of one lens group constituting the zoom lens SL which moves at the time of focusing, with respect to the variable magnification position (focal length) and the object distance.

In the figure, the magnification position (focal length) is plotted on the x-axis.
The object distance is shown on the y-axis, and the position on the optical axis of the lens group is shown on the z-axis. That is, the z-axis direction corresponds to the optical axis direction of the zoom lens. INF indicates infinity, MOD indicates a close distance, WIDE indicates a wide angle end, and TELE indicates a telephoto end.

As shown in the figure, in the zoom lens according to the present invention, the position (z) on the optical axis of the lens group changes non-linearly depending on the zoom position (x) and the object distance (y). Moves on one curved surface. One curved surface Sz is represented by an approximated curved surface, and the coefficients at this time are recorded in the memory unit 4 as position coefficients a, b, and c.

In this embodiment, the approximate curved surface Sz may be treated as an approximate plane for simplicity. At this time, the position Z on the optical axis of the lens group can be treated as one point on a plane Sz where the focal length is x, the object distance is y, and the coefficients are a, b, and c: Z = ax + by + c ‥ (1) That is, it may be handled as a position plane (Sz) corresponding to the values x and y.

Here, x is inputted from the focal length setting means 1 and y is inputted from the object distance setting means 2 in FIG.
b and c correspond to the values x and y, as shown in FIG.
Is selected from one area stored in. The CPU 6 calculates the position (z) on the optical axis of the lens group within the plane area Sz, for example, by using the above values to calculate the equation (1).

Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

FIG. 4 shows a case where the zoom operation is performed by the focal length setting means 1 as an example, but the same applies to the focus operation.

The focal length information input from the focal length setting means 1 by the zoom operation, that is, the target zoom position f _0.
Is detected by the detecting means 3. And the current zoom position f _i
When the target zoom position f ₀ has not been reached as compared with f _{i + 1} = f _i + Δf, one step Δf from the current zoom position f _i
Advance the zoom position only. The position P1 on the optical axis of the first moving lens group 8a at the zoom position fi _{+ 1} is stored in the memory unit 4.
Is calculated by the calculating means 6 based on the value stored in the. Similarly, positions P2 and P3 on the optical axis of the second moving lens group 8b and the third moving lens group 8c are obtained. The position of the moving lens group is uniquely determined by two variables, the zoom position f and the focus position F.

For example, as shown in FIG. 3, each lens group 8a
8c are curved surfaces as shown in FIGS. From these curved surfaces, the positions P1, P on the optical axis of each of the moving lens groups 8a to 8c.
2 and P3 are obtained by using the above-described equation (1).

Next, the positions P1, P2, P of each moving lens group
3 is read into each of the lens position control means 7a to 7c.

Next, the driving units are driven by the respective lens position control means 7a to 7c to drive the respective moving lens groups. At this time, a position servo generally used widely is used. Usually, when a position servo is performed, a certain amount of position error may occur.

If a position error occurs in the control, even if the command values P1, P2, and P3 are correctly output from the arithmetic means 6, an error occurs in the image forming position of the zoom lens, and a focus shift occurs.

Therefore, in the present embodiment, the imaging position error generated by the control position error of each lens group moved is corrected by one lens group selected by the selecting means 13.

At this time, the selecting means 13 moves at the time of focusing, and at the zoom position at that time, the lens group having the smallest sensitivity is selected as the lens group for correction.

For example, the sensitivity of each lens group to the image forming position at each zoom position is stored in the memory unit 4,
The lens group with the small sensitivity at that time is selected.

Then, the correction value calculating means 12 calculates a correction amount ΔP when correcting with the selected lens group.

Now, assume that the sensitivities of the first, second and third lens groups at certain zoom positions are α1, α2 and α3, respectively, and the correction amounts are ΔP1, ΔP2 and ΔP3, respectively. When the selecting unit 13 selects, for example, the second lens group, the correction amount ΔP2 is

[0045]

(Equation 1) Becomes

When the third lens group is selected, the correction amount ΔP3 is

[0047]

(Equation 2) Becomes

In this embodiment, the correction may be made by selecting both the second and third lens units and moving both the second and third lens units at a fixed ratio.

Then, the correction amount ΔP is less than a certain value,
For example, when the error becomes equal to or less than the allowable imaging position error, the correction ends.

In this embodiment, as a method of applying the correction, as shown in the flowchart of FIG. 8, the correction amount of the imaging position error after each lens group is moved is calculated by the correction amount calculating means, and then the correction is immediately performed. Instead, the correction may be made by adding the data at the time of driving in the next step.

Thus, the operation of one step is completed, and the process returns to the beginning to check whether or not the target zoom position f ₀ has been reached, and the above operation is repeated until the target zoom position is reached.

As described above, in the present embodiment, an image forming position error caused by a control position error of each moving lens group is corrected by an appropriate lens group corresponding to a zoom position at that time, so that a focus movement caused by zooming is achieved. It is possible to suppress as much as possible. Further, this embodiment can be achieved only by adding the selection means and the correction value calculation means in terms of configuration, so that the control system is not complicated and the size and weight are reduced.

[0053]

According to the present invention, the position on the optical axis of each lens group is stored in the memory means in advance based on the setting values input from the focal length setting means, the object distance setting means or both setting means as described above. It is calculated by using the position information on the focal length and the object distance, and the difference between the value obtained at this time and the position on the optical axis of each lens group after actually driving each lens group is calculated. Reduce the generated imaging position error
By moving and correcting one lens group appropriately selected for each camera position, it is possible to achieve a camera system capable of always obtaining a good image on the image forming plane.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a memory unit in FIG. 1;

FIG. 3 is an explanatory diagram showing positions on the optical axis of a lens group with respect to an object distance and a focal length.

FIG. 4 is a flowchart of the first embodiment.

FIG. 5 is an explanatory diagram showing a position on the optical axis of a lens group 8a according to the first embodiment.

FIG. 6 is an explanatory diagram showing a position on the optical axis of a lens group 8b according to the first embodiment.

FIG. 7 is an explanatory diagram showing a position on the optical axis of a lens group 8c according to the first embodiment.

FIG. 8 is another flowchart of the first embodiment.

FIG. 9 is a schematic view of a conventional rear focus type zoom lens.

FIG. 10 is an explanatory diagram showing a position on the optical axis of a focus lens group of the zoom lens of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Focal length setting means 2 Object distance setting means 3 Detecting means 4 Memory unit 6 Calculation means 7a, 7b, 7c Lens position control means 8a, 8b, 8c Lens groups 9a, 9b, 9c Drive units 10a, 10b, 10c Position detecting units 11a, 11b, 11c Position error calculating means 12 Correction value calculating means 13 Selecting means

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takutetsu Kobayashi 53, Imaiue-cho, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Within the Canon Inc. (72) Inventor Takashi Omuro 53-Imaiue-cho, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Canon Inc.Kosugi Business Office (72) Setsuo Yoshida 53 Imaiue-cho, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Canon Inc. (56) References JP-A-3-123331 (JP, A) JP-A-3-105304 (JP, A) JP-A-63-220208 (JP, A) JP-A-60-53907 (JP, A) JP-A-60-143309 (JP, A) JP-A-52-15226 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7/08 G02B 7/10

Claims (4)

(57) [Claims] 1. A zooming unit comprising a plurality of lens groups is moved on an optical axis to perform zooming, and a focusing unit including at least a part of lens units of the zooming unit is moved on an optical axis to focus. A focal length setting means for inputting focal length information, an object distance setting means for inputting object distance information, and detecting the focal length information and / or the object distance information. Detecting means and, based on the detection signal from the detecting means, for the focal length information and the object distance information, select the corresponding position information from the memory unit in which the position information on the optical axis of each lens group is recorded, Calculating means for calculating the position of each lens group on the optical axis using the position information; lens position controlling means for driving a driving unit based on a signal from the calculating means to move each lens group; Position error calculating means for calculating a difference between a value from a position detecting unit for detecting the position of the lens group on the optical axis and a value obtained by the calculating means, and correcting an imaging position error based on a signal from the calculating means. Selecting means for selecting a lens group to be corrected, and a correction value for calculating a position on the optical axis of the lens group selected by the selecting means for correcting an imaging position error using an output signal from the position error calculating means. A camera system having a calculation unit, wherein the lens position control unit drives the drive unit to move the lens group on the optical axis based on an output signal from the correction value calculation unit. . 2. The selecting means moves during focusing among the plurality of lens groups, and selects the lens group with the lowest sensitivity at the zoom position in the focal length information detected by the detecting means. 2. The method according to claim 1, wherein
Camera system. 3. A variable magnification unit including a plurality of lens groups is moved on the optical axis to perform magnification, and a focusing unit including at least a part of the lens units of the magnification unit is moved on the optical axis to perform focusing. In a camera system having a zoom lens, the focal length information is input from the focal length setting means and / or the object distance information is input from the object distance setting means, and the focal length information and / or the object distance information is detected by the detecting means. And, based on the detection signal from the detection means, the arithmetic means selects focal position information and object distance information, and selects corresponding position information from the memory unit in which the position information of each lens group is recorded. Using the position information, the position of each lens group on the optical axis is calculated, and the lens position control means drives the drive unit based on a signal from the calculation means to move each lens group. The position on the optical axis of each lens group is detected by the position detecting unit, and the difference between the value detected by the position detecting unit and the value obtained by the calculating unit is obtained by the position error calculating unit. A lens group for which the imaging position error is to be corrected by the selection unit based on the signal of (i), and the selection unit for correcting the imaging position error by the correction value calculation unit using the value from the position error calculation unit. The position of the selected lens group on the optical axis is obtained, and based on the output signal from the correction value calculating means, the lens position control means drives the drive unit to move the lens group on the optical axis. Characterized camera system. 4. The method according to claim 1, wherein the selecting unit moves at the time of focusing from among the plurality of lens units, and selects a lens unit having the lowest sensitivity at a zoom position in the focal length information detected by the detecting unit. 4. The camera system according to claim 3, wherein: