JPH01131507A - Optical device - Google Patents

Abstract

PURPOSE:To enable rapid focusing with high accuracy by detecting the out-of-focus quantity of a photographing system to be mounted and making prescribed computations by the utilization of the out-of-focus quantity and the various optical numerical values intrinsic to the photographing to determine the moving quantity of the focusing lens during photographing with good accuracy, then delivering the moving quantity to the photographing system. CONSTITUTION:The out-of-focus quantity from the intended imaging plane of the photographing system 1 is detected by a focus detecting means 2. The various optical numerical values intrinsic to the photographing system, for example, the reference coefft. S0 relating to the movement of the focusing lens and the proportional constant A relating to the function in the case of expressing the out-of-focus quantity as a function are stored in a memory part 3 provided in the photographing system 1. The moving coefft. Sd corresponding to the degree of sensitiveness at the time when the focusing lens is ought to be moved is determined from the reference coefft. S0 from the memory part 3 and the out-of-focus quantity DELTAd determined by the constant A and the focusing detecting means 2 and the quantity (x) to move the focusing lens is computed therefrom in a 1st computing means 4. The focusing lens is moved by the prescribed quantity in accordance with the result of this computation. The focusing lens is thereby moved to the prescribed position with the good accuracy with the smaller number of times.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical device, and in particular detects the day focus amount of a photographing system attached to the optical device and the so-called defocus amount, which is an amount equivalent to this amount. The present invention relates to an optical 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 defocus.

(Prior art) Conventionally, a focus detection device installed on the optical device side of the camera body detects out-of-focus stars in the photographing system attached to the optical device, and the output signal at this time is used to focus the photographing system. An automatic focusing device that performs focusing by moving a lens is disclosed in, for example, Japanese Patent Laid-Open No. 55-11275 and Japanese Patent Laid-Open No. 59-15.
This is proposed in Publication No. 1116 and the like.

Generally, 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 is nonlinear. For example, in an imaging system with a single focal length, the amount of defocus varies depending on the object distance and the position of the focusing lens on the optical axis, and in an imaging system with a variable magnification system, the amount of defocus varies depending on the zoom position, object distance, and the focusing lens. They differ depending on the position on the optical axis, etc.

This is because the imaging plane (the ratio of the movement/movement Δχ° of the device Δχ゛/Δχ, so-called sensitivity to the minute movement Δχ on the optical axis of the focusing lens differs depending on each element of the imaging system and the imaging conditions). It is for coming.

For example, in an imaging system with a single focal length, the amount of defocus is Δ
d, and if the entire lens system is moved to perform focusing, if the photographing system is moved by .DELTA.d, the focus will not be achieved. In particular, the focusing error at this time becomes larger as the object becomes closer.

In addition, in a photographing system in which the object-side lens group is a focusing lens, for example, a variable power system with a focal length of 11 f = 1 to f = 4, the amount of defocus is Δd, and the focusing lens at a focal length of f = 1 is used. Assume that the amount of movement is Δχ8. When zooming is performed and the focal length is set to f=4, the amount of movement Δχ7 of the focusing lens changes to approximately Δχ7=Δχw/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 zoom position of the variable power system.

Also, even if the amount of defocus is the same when the focusing lens group of the photographing system is in a position where it focuses on an object at infinity and when it is in a position where it focuses on a close object, The amount by which the focusing lens should be moved varies.

In addition, even if the amount of defocus is the same, the amount of movement of the focusing lens differs depending on the object distance. For the above reasons, even if the amount of out-of-focus of the photographing system is detected by the focus detection means, it is not possible to accurately detect the focus unless the amount of movement of the focusing lens is determined by taking into consideration various elements in the photographing system.

Conventionally, when the imaging system has a single focal length, the amount of defocus Δd
Alternatively, the focusing lens was simply moved by a corresponding amount.

In addition, when the photographing system has a variable magnification system, the amount of movement Δ of the focusing lens is determined by considering only the sensitivity S2 at the zoom position.
χ was calculated using the Δd/S2 formula. For this reason, there is a large error in the amount of movement of the focusing lens, making it difficult to move the focusing lens to the specified position in - times. I had to. 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 detects the amount of defocus of a photographing system attached to an optical device, and utilizes the amount of defocus and various optical values unique to the photographing system to obtain a predetermined value. By calculating the amount of movement of the focusing lens in the photographing system with high accuracy and sending the amount of movement to the photographing system, an optical device that can perform focusing quickly and with high precision is developed. For the purpose of providing.

(Means for Solving the Problems) An optical device is provided with a removable replacement photographing system, and the optical device includes focus detection means for detecting the amount of defocus of the photographing system attached to the optical device. , receives a proportionality constant for the function when the reference coefficient related to focusing and the amount of defocus sent out from the photographing system is expressed as a function, and calculates the value of the photographing system from the reference coefficient, the proportionality constant, and the amount of defocus. and calculation means for determining the amount of movement of the focusing lens and sending a signal related to the amount of movement to the photographing system.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1 is a block diagram when an imaging system is attached to an optical device according to an embodiment of the present invention. In the figure, 10 is an optical device. Reference numeral 1 denotes a photographing system, which consists of an imaging system with a single focal length, a variable magnification system, etc., and has a focusing lens. Reference numeral 2 denotes a focus detecting means which detects the amount of day focus from the expected imaging plane of the photographing system 1 or the amount of out-of-focus which is an amount equivalent thereto.

Reference numeral 3 denotes a storage unit provided in the photographing system 1, which stores optical values specific to the photographing system, such as a reference coefficient 50 regarding the movement of the focusing lens and a proportionality constant ( (hereinafter also referred to as a "constant") A is stored. 4 is a first calculating means, which is a reference coefficient S from the storage section 3; and the constant A and the defocus amount Δ determined by the focus detection means 2.
d, a movement coefficient Sd corresponding to the sensitivity when the focusing lens should be moved is determined, and from this the amount χ by which the focusing lens should be moved is calculated. Reference numeral 5 denotes a driving means, which moves the black-focusing lens by a predetermined amount based on the calculation result obtained by the first calculation means 4.

The focus detection means 2, the first calculation means 4, and the determination means 6, which will be described later, are housed in the optical device 10.

Generally, the amount of movement of the focusing lens relative to the amount of defocus varies depending on the object distance 9, the initial position of the focusing lens on the optical axis, the zoom position, etc.

For example, even if the object distance is the same, the amount of defocus Δd obtained by the focus detection means differs depending on the position of the focusing lens on the optical axis.

For example, as shown in Fig. 2, when the object distance is 121 and the imaging system 2
Assume that the No. 1 focusing lens 22 is located χ2□ away from the position to be focused. At this time, the amount of defocus Δd2+ obtained by the focus detection means and the amount of movement χ2 of the focusing lens. The relationship is as shown in Figure (C). Here, the defocus slip Δd2+ corresponds to the area surrounded by a2+, a22+ 823, and a24.

On the other hand, if the focusing lens is located χ2□ away from the position to be focused as shown in FIG.
Corresponds to the area surrounded by a24. In addition, the same figure (8)
, (13), P2O is the planned imaging plane, and 20 is the object. As described above, in a general photographing system, the amount of defocus Δd and the amount of movement χ of the focusing lens have a nonlinear relationship.

Therefore, in this embodiment, when determining the amount of movement of the focusing lens from the amount of defocus, a nonlinear movement coefficient Sd is defined as the nonlinearity between the amount of defocus and the amount of movement of the focusing lens, and this and the amount of movement of the focusing lens are It is characterized in that the amount of movement of the focusing lens can be determined with good accuracy from the amount Δd.

Next, the operation of this embodiment will be described first with respect to the case where the photographing system that is attached to and detached from the optical device consists of an imaging system with a single focal length.

As shown in FIG. 1, the focus detection means 2 first detects the amount of out-of-focus Δd of the photographing system. Then, when the determination means 6 determines that the amount of defocus Δd is within the allowable range of the photographing system, shooting such as release is performed, and when the amount of defocus Δd is outside the permissible range, the amount of defocus Δd is manually input to the first calculation means 4.

Further, based on the signal from the discriminating means 6, a reference coefficient S specific to the imaging system is stored from the storage unit 3 of the imaging system 1. When the amount of defocus is expressed as a function, a proportionality constant A corresponding to the function is input to the first calculation means. Here, the reference coefficient 30 and the constant A have one fixed value when the imaging system has a single focal length.

The first calculation means 4 calculates the reference coefficient S. , constant A, and the movement coefficient Sd when moving the focusing lens using the amount of defocus Δd, using the function f(Δd) of the amount of defocus Δd, 5d=So+A x f(Δd) --- −
--(1) is required.

And (Movement coefficient Sd calculated by the equation 1 and defocus force Δ
The amount of movement χ of the focusing lens is determined from d as χ=Δd/Sd (2). The focusing lens is moved by the driving means 5 in accordance with the output value from the first calculation means 4.

On the other hand, in conventional automatic focusing devices, as shown in FIG. Assume that the amount of deviation is Δd31. Then, the photographing system was moved by Δd31 as shown in FIG. In this case, the amount of movement of the imaging system is too large, and the object 3
0 is a point P31 that is deviated from the planned imaging plane P3Q by Δd32
image is formed.

For this reason, it was necessary to perform focus detection again.

In this embodiment, the defocus meter Δ obtained from the focus detection means 2
d is corrected using a reference coefficient 50 corresponding to the sensitivity of the photographing system and a constant A, and then the amount of movement of the focusing lens is determined. For example, in this embodiment, the function f(Δd) is expressed as a quadratic equation in equation (1), and 5d=s, + A−Δd2・, −
- Find the transfer coefficient Sd using the formula (3),
The movement amount χ of the focusing lens is calculated from the movement coefficient Sd and the defocus amount Δd using equation (2). Note that the reference coefficient S in equation (3). is, for example, the sensitivity of the imaging system at the reference distance object.

In this way, instead of the amount of defocus Δd, by moving the focusing lens by the value χ calculated using the 2-in formula, it is possible to move the focusing lens to a predetermined position with more precision than before. There is.

Next, an embodiment in which the photographing system has a variable magnification system will be described. When the photographing system has a variable magnification system, compared to the case of a single focal length imaging system, the above-mentioned reference coefficient So and constant A are different for each zoom position. There is.

Fig. 4 shows the block diagram of Fig. 1 in particular detail for the case where the imaging system has a variable magnification system, and the same elements as in Fig. 1 are given the same reference numerals. be. In FIG. 4, reference numeral 41 denotes a zoom position detection means provided on the photographing system 1 or the camera body side, which detects the zoom position of the photographing system 1. That is, when the zoom range of the variable power system is divided into a plurality of parts, it is detected which position from the telephoto end, for example, the zoom position of the variable power system that is performing focus detection corresponds to as a reference. Reference numeral 42 denotes a second calculation means provided in the photographing system 1 or a part of the first calculation means 4, and is used to obtain a reference coefficient S corresponding to the sensitivity specific to the zoom position. For example, if the variable power system is at the first zoom position from the telephoto end and the reference sensitivity coefficient, which is the sensitivity to the movement of the focusing lens at the telephoto end, is Sho, then the reference coefficient at the zoom position is Sz. I'm looking for it as.

In equation (4), at the telephoto end, I=1 and 52=SZO, where Sz is the sensitivity at the telephoto end.

In this embodiment, if the storage capacity of the storage unit 3 is sufficient, the reference coefficient S2 for each zoom position obtained by equation (4) may be stored, and in this case, the second calculation means is unnecessary. becomes.

After determining the reference coefficient S2 at the zoom position where focus detection was performed in Fig. 4, the movement coefficient SZd of the focusing lens is determined.
The first calculation means 4 uses f(Δdz) which is a function of the defocus amount Δd2 to calculate Sz,=S,l+A−f(Δ
d,,) ・・・・・・・・・ Required from (5).

Then, the movement amount χ2 of the focusing lens is Δd2 χ ”SZd ・・・・・・・・・・・・・・・・・・(
6) I want more.

Generally, the amount of defocus of a photographing system with a variable magnification system is Δd8I,
The amount of movement of the focusing lens at this time is χ5
Also, the reference coefficient corresponding to the sensitivity of the focusing lens is S
When St is assumed, the functions of each of these elements are as shown in FIG. 5(A).

As shown in the figure, the amount of defocus ΔaS+ detected is the white line A
The area surrounded by x, i.e. point a5°, asl.

a! 2+853, and the defocus amount ΔdSt at this time is nonlinear with the amount χlft to be moved for focusing the focusing lens.

SXO on the right side of the figure is a value unique to the photographing system, and corresponds to the sensitivity of the focusing lens near the focusing position at a - constant zoom position, object distance, etc.

In addition, Sz is the sensitivity considering only the zoom position in the shooting state where focus detection is performed, and in reality, in shooting systems with many variable magnification systems, Sz ξ SXO... 7)
It can be approximated as

Therefore, in the following explanation, for the sake of simplicity, it will be explained as 82 to SXO.

SSI is the zoom position and object distance during focus detection.

The sensitivity is dependent on the position of the focusing lens on the optical axis. In the figure, for example, when the detected amount of defocus is Δd5□, the amount of movement of the focusing lens for focusing is χ-2. Here, Δd52 is point a. +a
This corresponds to the area surrounded by S4+ aSS+ a 83. In this way, the movement amount χ for focusing of the focusing lens and the defocus amount Δd are nonlinear. Therefore, in order to determine the movement amount χ2 from the defocus amount Δd2, it is important to determine the equation of the curve AX. However, the equation of the curve AX is unique to the imaging system and changes variously depending on the above-mentioned imaging conditions, so it is very difficult to specify it uniquely.

For this reason, in conventional automatic focusing devices, the amount of defocus is Δ
When d5□, as shown in FIG. 5(A), using the sensitivity S2 near the in-focus point at the zoom position where focus detection was performed, calculate the moving amount χ2 of the focusing lens by χ2=Δds+/Sz
I was looking for it as. Therefore, as shown in the same figure (B), the movement amount χ2 is Δχ=ΔS/S, where ΔS is the area surrounded by the points a53°a ff16+a62, that is, the figure (
The movement was excessive by Δχ shown in B). As a result, it was necessary to detect the amount of defocus again and repeat the process.

On the other hand, in this example, since the value SXO in the vertical direction in the figure can approximate the sensitivity of only the zoom position in many imaging systems, the coordinates of the vertical axis in FIG. , that is, the sensitivity S2 is obtained, for example, from equation (4). Next, as a result of examining various imaging systems, we found that the curve AX can be well approximated by a quadratic function as shown in the same figure (C) when the amount of defocus Δd2 is plotted on the horizontal axis.
When the amount of defocus is expressed as a function, the curve AX is obtained as a proportionality constant for the function from Ax=AXΔd22+S, """ (s). From this, point a5° in FIG. 5(A).

a51. From Δd51, which corresponds to the area SSZ surrounded by aS2+a53, a value corresponding to the horizontal axis, that is, a value SZd corresponding to the vertical axis when calculating the movement amount χ2 of the focusing lens,
In other words, the movement coefficient SZd corresponding to the sensitivity of the focusing lens is 5zd=Sz + (AX −sz )/3 −−−−
-- (9). And (8), (9)
The transfer coefficient SZd is determined from the formula.

Then, from this, the movement amount χ2 of the focusing lens is calculated from the defocus amount Δd51 as χ2=Δd g +/S za ・・・・・・・・・・・・
...(11) is obtained. As a result, the area SSZ corresponding to the amount of movement of the focusing lens is 5SZ=SzdXX
It becomes z. The area SSZ and the area corresponding to the defocus amount Δd51 obtained from the focus detection means are shown in FIG. 5(A).

As is clear from (D), SSZ ~ ΔdSt. From this, originally, the amount of movement χS□ to be moved and the amount of movement χ2 calculated by calculation are χ51 and χ2. Therefore, according to this embodiment, it is possible to move the focusing lens to a predetermined position with high precision in one operation.

In this embodiment, the constant A in equation (10) is stored, for example, in the storage unit 3 of the imaging system 1 for each zoom position, and is read out together with the reference sensitivity SZO by the zoom position detection means. There is.

In this way, in this embodiment, as in the conventional case, out of focus ■Δd2
Instead of directly determining the amount of movement of the focusing lens from the reference coefficient 32 corresponding to the sensitivity depending on the photographing system, first, when the amount of defocus Δd2 and the amount of defocus are expressed as a function, a proportionality constant for the function is calculated. From the reference coefficient Sz only at A and the zoom position, the movement coefficient S is calculated from equation (5) or equation (10).
Zd is determined, and from this movement coefficient SZd and the amount of defocus Δd2, the first calculation means uses equation (11) to determine the amount of movement χ2 of the focusing lens, thereby performing automatic focusing with high precision.

In this embodiment, the polynomial used to calculate the movement coefficient SZd may be determined using a function other than a quadratic function, for example, a cubic function or higher, depending on the characteristics of the imaging system.

In addition, we calculated the case where the shooting system has a variable magnification system.
The reference coefficient 82 in equation (4) may be determined using another equation depending on the characteristics of each imaging system.

(Effects of the Invention) According to the present invention, the amount of movement of the focusing lens is accurately determined by performing predetermined calculations using the amount of defocus of the attached photographing system and the inherent sensitivity of the photographing system. Therefore, it is possible to achieve a highly accurate optical device that can move the focusing lens to a predetermined position fewer times than with conventional methods.

[Brief explanation of the drawing]

Fig. 1 is a block diagram when an imaging system is attached to an optical device according to an embodiment of the present invention, the second cause is shown, Fig. 3 is an explanatory diagram regarding defocus -1 and movement of the focusing lens, Fig. 4 5 is a block diagram when an imaging system having a variable magnification system is attached to an optical device according to an embodiment of the present invention, and FIG. 5 shows the relationship between the amount of defocus and the amount of movement of the focusing lens in FIG. 4. FIG. In the figure, 10 is an optical device, 1 is a photographing system, 2 is a focus detection means, 3 is a storage section, 4 is a first calculation section, 5 is a driving means, and 6 is a discrimination means. Patent applicant Canon Co., Ltd. Figure 2, Day 5

Claims (1)

[Claims] The optical device is an optical device to which a replacement photographing system can be attached and detached, and the optical device includes a focus detection means for detecting the amount of defocus of the photographing system attached to the optical device, and a focus detecting means for detecting the amount of defocus of the photographing system attached to the optical device, and When the reference coefficient regarding focus and the amount of defocus are expressed as a function, receive a proportionality constant for the function, and calculate the amount of movement of the focusing lens of the photographing system from the reference coefficient, the proportionality constant, and the amount of defocus. 1. An optical device having a focus detection device, comprising: arithmetic means for sending a signal related to the amount of movement to the imaging system.