JPS62215219A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To find the quantity of movement of a focusing lens accurately and speedily and to perform high-accuracy focusing operation by performing specific arithmetic operation by utilizing the quantity of defocusing of a photography system, the displacement position of the photography system, and various characteristic optical numerals that the photography system has. CONSTITUTION:The photography system 1 has a power variation system 12 and the focusing lens 11 and a focus detecting means 2 detects the quantity of defocusing from the expected image formation plane of the photography system 1 or a quantity equivalent to it. A storage part 3 provided in the photography system 1 is stored with various optical numerals characteristic to the photography system, e.g. two reference coefficients delta and N concerning the movement of the focusing lens. A power variation position detecting means 6 detects one of power variation areas which are divided having different ratios between the wide-angle and telephoto sides of the entire power variation range and an arithmetic means 4 calculates the expected quantity chi of movement of the focusing lens from the reference coefficients from the storage part 3, the quantity (d) of defocusing found by the focus detecting means 2, and a power variation signal from the power variation position detecting means 6. A driving means 5 drives the focusing lens 11 by a specific quantity on the basis of the arithmetic result obtained by the arithmetic means 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an automatic focusing device, and in particular detects the amount of defocus of a photographing system or the amount of out-of-focus corresponding to this, and detects the amount of out-of-focus. The present invention relates to an automatic focusing device suitable for photographic cameras, video cameras, etc., which performs focusing by moving a focusing lens of a photographing system according to the amount of movement.

(Prior art) Conventionally, the amount of out-of-focus of the photographing system is detected by a focus detection means provided on the camera body side, and the output signal at this time is used to move the focusing lens of the photographing system to adjust the focus. Automatic focusing devices have been proposed in, for example, Japanese Patent Laid-Open Nos. 55-11275 and 1982-1511.16.

In general, the relationship between the amount of defocus of the photographing system and the amount of movement of the focusing lens to be moved during focusing differs depending on the zoom position in a photographing system having a variable magnification system.

This is because the ratio Δχ'/Δχ of the movement amount Δχ' of the imaging plane position to the minute movement amount Δχ on the optical axis of the focusing lens, the so-called sensitivity, differs depending on each element of the imaging system and the imaging conditions. It is.

For example, the object-side lens group is a focusing lens. For example, in a photographing system having a variable magnification system with a focal length f=1 to f=4, it is assumed that the amount of defocus is Δd and the amount of movement of the focusing lens in the focal path 11f=1 is Δχ0. When zooming is performed to set the focal length to f=4, the amount of movement Δχa of the focusing lens changes to approximately Δχ7=Δχo/42. In this way, even if the amount of defocus is the same, the amount of movement of the focusing lens differs depending on the zooming position of the zooming system.

Conventionally, when the photographing system has a variable magnification system, the variable magnification position is detected, and each variable magnification position stored in a storage section provided in a part of the photographic system is determined from the variable magnification position at this time. Sensitivity S for each
2 was selected and the amount of movement Δχ of the focusing lens was calculated using the 66782 formula. For this purpose, the storage section of the imaging system is required to have an element with a large storage capacity.

However, since storage capacity is limited, if you have to divide the entire magnification range and set the sensitivity for each area in a high-zoom ratio imaging system, it is necessary to change the division pitch of the magnification range. I had to make it rough. For this reason, in an imaging system with a high zoom ratio, there is a large error in the amount of movement of the focusing lens in each zoom range, and it is difficult to move the focusing lens to a predetermined position in - times, and focus detection is repeated. The focusing lens had to be sequentially moved to a predetermined position. For this reason, there are drawbacks such as a long focusing time, making it difficult to take quick pictures, and making it difficult to perform focusing with high precision.

(Problems to be Solved by the Invention) The present invention utilizes the amount of defocus of the photographing system, the variable magnification position of the photographing system, and the unique optical word value of the photographing system, and performs a predetermined calculation. To provide an automatic focusing device capable of accurately determining the amount of movement of a focusing lens and performing focusing quickly and with high precision.

(Means for solving the problem) Focus detection means for detecting the amount of out-of-focus of a photographing system having a variable magnification system, and dividing the variable magnification system into a plurality of areas at different ratios on the wide-angle side and the telephoto side. a magnification change position detecting means for detecting a magnification change area; a storage section provided in a part of the photographing system for storing a unique constant related to focusing; and an amount of out-of-focus from the focus detection means; , a calculation means for calculating a drive signal for moving the focusing lens of the photographing system using a unique constant from the storage section and a variable power signal from the variable power position detection means; and a driving means for driving the focusing lens based on a driving signal.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1 is a block diagram of an automatic focusing device according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a photographing system, which includes a variable magnification system 12 and a focusing lens 11. 2 is a focus detection means, which is a photographing system 1
The amount of defocus from the expected imaging plane or the amount of out-of-focus that is an amount equivalent to this is detected. 3 is a storage section provided in the imaging system 1, which stores the optical word value unique to the imaging system;
For example, two reference coefficients δ regarding the movement of the focusing lens,
N is memorized. Reference numeral 6 denotes a magnification change position detecting means for detecting one magnification change area of a magnification change area that is divided into a plurality of areas at different ratios on the wide-angle side and the telephoto side of the entire magnification change range.

4 is a calculation means which calculates the amount χ by which the focusing lens should be moved based on the reference coefficient etc. from the storage section 3, the defocus amount d obtained by the focus detection means 2, and the magnification change signal from the magnification change position detection means 6. It calculates and outputs a drive signal. Reference numeral 5 denotes a driving means, which drives the focusing lens 11 by a predetermined amount based on the calculation result obtained by the calculation means 4.

Generally, the amount of movement of the focusing lens relative to the amount of defocus varies depending on the magnification position of the variable power system even if the amount of defocus is the same.

In this embodiment, since the storage unit 3 has a limited storage capacity, the wi sensitivity for each variable magnification area is not stored as in the conventional case, but only two unique coefficients δ and N unique to the imaging system are stored. I am remembering it.

Here, for example, δ is a value corresponding to an allowable amount of out-of-focus at the telephoto end of the photographing system, and N is a value that depends on a zoom ratio larger than the number of divisions of the entire zoom range by the zoom system.

This simplifies the storage section.

Furthermore, when dividing the entire zooming range, it is divided into a plurality of areas so that the ratios differ between the wide-angle side and the telephoto side. For example, fT is the focal length of the entire system at the telephoto end, and fl is the average focal length of the i-th variable magnification area counting from the telephoto end.
, where N is a unique constant stored in the storage unit (where i=1.N).

FIG. 2 is an explanatory diagram of an embodiment in which the magnification change range according to the present invention is divided into eight regions using a gray code. In the figure, the left side is the telephoto side, and the right side is the wide-angle side.

In this embodiment, in contrast to the conventional uniform division, as is clear from the figure, the division is done densely on the telephoto side and sparsely on the wide-angle side.

This reduces the difference in sensitivity within each variable magnification region and improves the detection accuracy of the focusing lens drive signal. Furthermore, in this embodiment, the number of divisions can be increased up to the detection capability of the variable magnification position detection means, so it is possible to improve the detection accuracy of the drive signal.

In this embodiment, when the calculation means calculates the drive signal related to the movement of the focusing lens from the defocus amount d, the The drive signal P is calculated from the formula, where i is the multiplication area and P is the drive signal related to the movement of the focusing lens.

When i=1, that is, at the telephoto end, the drive signal P is P=d/δ
・・・・・・・・・・・・・・・・・・(3)

In this embodiment, when P=1, the amount of extension of the focusing lens that moves the image point by a value δ on the planned imaging plane is determined in advance, and this value is set as the minimum pitch for the extension. The focusing lens is extended with accuracy within the defocus tolerance.

Note that δ may be configured to be variable within the S shadow system.

Next, this embodiment will be explained using specific numerical values.

For example, assume that the photographing system has a focal pressure of 1 [tf=1 to 2 and a variable power ratio of 2]. At this time, the unique coefficients δ and N of the storage section of the photographing system are each stored in advance as δ=0.05°N=32. Further, the variable magnification range is set to 1=25, and is divided into 24 areas.

The focal length f of the i-th area counting from the telephoto side is (1
) can be obtained from the formula. Here, 1=25 is the wide-angle end.

Now, let the amount of defocus d obtained from the focus detection means be d=0.
5, the movement signal P of the focusing lens becomes when f=1 from equation (2). That is, even if the amount of defocus is the same, a movement signal P that depends on (fT/f, )2 is obtained, which is four times more edgy at the wide-angle end than at the telephoto end.

In addition, it can be obtained from equation (2) in the same manner as described above at intermediate magnification positions.

Further, when the zoom ratio is 3, i=1 to 29, and when the zoom ratio is 4, i=] to 31, so that the zoom range can be divided appropriately. Further, the constant N is not limited to 32, and may be any number.

In this embodiment, even if the number of divisions changes depending on the shooting system, it can be handled by dividing into fewer parts when the magnification change stroke is short and low, and by dividing it into many parts when the magnification change stroke is long and high. The minimum pitch for division can be reduced.

(Effects of the Invention) According to the present invention, a drive signal related to the movement of the focusing lens is generated by performing a predetermined calculation using the amount of defocus of the photographing system, the variable magnification position signal, and the reference coefficient inherent in the photographing system. can be determined with high accuracy, it is possible to achieve a highly sophisticated automatic focusing device that can move the focusing lens to a predetermined position fewer times than with conventional methods.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an automatic focusing device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of an embodiment of a gray code for dividing a magnification range according to the present invention. In the figure, 1 is the shooting system, 2
1 is a focus detection means, 3 is a storage section, 4 is a calculation means, 5 is a drive means, 6 is a variable magnification position detection means, 11 is a focusing lens, 1
2 is a variable magnification system.

Claims (3)

[Claims] (1) A focus detection means for detecting the amount of defocus of a photographing system having a variable magnification system, and a variable magnification area that is divided into a plurality of areas at different ratios on the wide-angle side and the telephoto side of the variable magnification system. A variable magnification position detecting means for detecting a region, a storage section provided in a part of the photographing system and storing unique constants related to focusing, and an amount of out-of-focus from the focus detecting means, and a unique constant from the storage section. and a calculation means for calculating a drive signal for moving the focusing lens of the photographing system using the constant and the magnification signal from the magnification change position detection means; 1. An automatic focusing device comprising: a driving means for driving a lens. (2) The i-th variable magnification area counted from the telephoto end of the plurality of variable magnification areas detected by the variable magnification position detecting means is i, the unique constant stored in the storage unit is δ, N, When the amount of defocus detected by the focus detection means is d, and the drive signal related to the movement of the focusing lens is P, the calculation means uses the following formula: P=(d/δ)×(N/N+1-i) The automatic focusing device according to claim 1, further comprising an arithmetic circuit for calculating the drive signal P. (3) The variable magnification area of the photographing system is stored in the storage unit, where f_T is the focal length of the entire system at the telephoto end, and f_i is the average focal length of the i-th variable magnification area counting from the telephoto end. When the unique constant is N, f_i^2=f_T
2. The automatic focusing device according to claim 1, wherein the automatic focusing device is divided into 2[1-(i-1)/N] (where i=1, N).