JPH05227465A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To provide an automatic focusing device whose focusing time is short, and is capable of the predictive AF of a moving body, and further, does not give a photographer an unpleasant feeling during focusing operation. CONSTITUTION:Focus signal detectors 41p, 41q for extracting only a prescribed frequency band out of a picture signal, and detecting plural focus signals corresponding to focusing degrees at plural positions of different optical path differences from the extracted signal, and a focusing controller 43 to judge the focusing state based on of plural focus signals from these detectors 41p, 41q, and simultaneously, detect a focusing position are provided. Then, a drive circuit 40 to change the relative position of image pickup elements 39p, 39q and a photographing optical system is controlled by this output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device used for a single-lens reflex camera, an electronic camera or the like.

[0002]

2. Description of the Related Art As a conventionally known automatic focusing device, a predetermined frequency component is extracted from an image signal obtained from an image sensor, and a photographing optical system is moved to a position where the extracted frequency component is maximum. There is a so-called hill-climbing method in which the focus is adjusted accordingly.

The automatic focusing device to which the hill climbing method is applied can be miniaturized because no dedicated optical component for focus adjustment is required, and a highly accurate focusing can be achieved without depending on the pattern of the copy. It has the advantage that it can be burnt. An automatic focusing device using the mountain climbing method is, for example, NH
K Technical Report, 1965, Volume 17, No. 1 through Volume 86
No. (P21 to P37).

By calculating an in-focus position by interpolation calculation from a plurality of frequency component values near the in-focus position,
The present applicant has already applied for automatic focusing for improving the focusing speed and the focusing accuracy in the mountain climbing method (Japanese Patent Application No. 1-319473). Further, in order to perform the focus adjustment with higher accuracy, a method of optimally setting the interpolation interval of the interpolation calculation from parameters such as the F number of the photographing optical system, the focal length, and the frequency band of the frequency component to be extracted is also applied. It has already been filed by a person (Japanese Patent Application No. 02-10987).
No. 6).

An outline of such an automatic focusing device is shown in FIG.
Will be described. In FIG. 19, the subject image captured by the photographing optical system 1 is formed on the light receiving surface of the CCD two-dimensional image pickup device 2. The electric charge accumulated by the formed subject image is read out as an image signal by a read-out signal given from the drive circuit 3 at predetermined time intervals,
The pass frequency bands are S1 and S via the amplifier 4, respectively.
2, S3, S4 (S1 <S2 <S3 <S4) bandpass filters (hereinafter referred to as BPFs) 5a to 5d.
Entered in. A gate circuit 8a is provided for each BPF 5a-5d.
.About.8d, detectors 9a to 9d consisting of a squarer, A / D converters 10a to 10d, and digital integrating circuits 11a to 11d are connected in series, respectively. Each gate circuit 8a-8
A distance measuring area designating circuit 21 is connected to d and has a function of extracting only an image signal of an area to be focused. The digital integrator circuits 11a to 11d are composed of an adder 12 and a latch circuit 13 and have a frequency component V of each frequency band.
1, V2, V3, V4 are output. Here, since each frequency component is a signal indicating the degree of focusing, it is hereinafter referred to as a focus signal.

The microprocessor 22 uses the focus signals V1 to V4 sent for each field to perform focus adjustment control based on interpolation calculation. Here, the interpolation calculation is performed by the following equation using the maximum value of the focus signal and the three points on both sides thereof as shown in FIG. When P0 ≧ P2 Xf = X1-L / 2 · {(P0-P2) / (P1-P2)} (1) When P0 <P2 Xf = X1 + L / 2 · {(P2-P0) / (P1 -P0)} (1) '

Here, Xf represents a focus position, and L represents an interpolation interval. A curve formed by this focus signal will be referred to as a focus signal curve. Then, the interpolation interval L can be optimally set from parameters such as the F number of the photographing optical system, the focal length, and the frequency band of the frequency component to be extracted, so that high-speed and high-precision focusing adjustment can be performed. The contrast method by interpolation calculation using such three points
This is called point interpolation. Further, this application also describes a focus position calculation method using two points that sandwich the focus position as shown in FIG. As shown in FIG. 21B, this is the contrast ratio R (= Vp
/ Vq) and the interval 1 between the two points, a method of obtaining the defocus amount D by referring to a table in which the defocus amount is stored in advance is called two-point interpolation. Here, dFZP is a parameter of the optical system, and dFZP = 1.22 · F / s (2) Here, F is the F number of the photographing optical system s is the center frequency of the BPF.

[0008]

However, since the prior art uses the image signal at one position near the image plane, it has the following drawbacks. Here, the image forming plane refers to a plane perpendicular to the optical axis of the image of the subject to be imaged. (1) When the focus adjustment is started, the defocus direction may not be known and the photographing optical system may be driven in the direction opposite to the direction of the focus position, which increases the focus time. (2) Even if the photographic optical system is in focus at the time of starting focus adjustment, it is necessary to defocus once, and the focus time also becomes long.

(3) When the pass band of the BPF is narrow, the velocity of the moving object can be detected in principle by the three-point interpolation as disclosed in the prior art, but in reality, the influence of the noise of the focus signal is exerted. It is necessary to widen the pass band in order to reduce the number of exposures, and it is difficult to perform focus adjustment (moving object prediction AF) in which the speed of the moving object is obtained and a time lag until exposure is taken into consideration. In the case of a moving object, the focus signal curve is greatly deviated from the shape stored in the table in the two-point interpolation, so that it is not possible to detect the moving object speed or let the focus position be determined.

(4) Since the photographic optical system once passes the in-focus position and then returns to the in-focus position (referred to as an overshoot operation), the photographer may feel uncomfortable in the in-focus adjustment operation. ..

As described above, according to the conventional technique, 1 near the image plane is formed.
Since the image signal at the position is used, the photographing optical system may be driven in a useless direction, and the focusing speed is not necessarily high. Further, the moving object predictive AF is difficult and sometimes the focus adjusting operation is uncomfortable.

The automatic focusing apparatus according to the present invention has been made in view of such a problem, and its purpose is to enable a moving object predictive AF with a short focusing time, and further to perform a focus adjusting operation. An object of the present invention is to provide an automatic focusing device which does not cause discomfort to a photographer.

[0013]

In order to solve the above-mentioned problems, an automatic focusing apparatus according to the present invention picks up an image formed by a photographing optical system at a plurality of positions having different optical path differences. One or a plurality of image pickup devices, a driving unit that changes the relative position of the image pickup devices and the photographing optical system along the optical axis direction, and the charge accumulated in the one or a plurality of image pickup devices as an image signal. One or more image reading means for reading, a bandpass filter for passing only a predetermined frequency band from the image signal read by the reading means, and an output signal of the bandpass filter have different optical path differences. Focus signal detection means for detecting a plurality of focus signal values according to the degree of focus at a plurality of positions, and a focus state from a plurality of focus signal values read from the focus signal detection means. And focus state determination means for determining the focus position detected from the plurality of focus signals values read from the focus signal detecting means comprises a focusing position control means for controlling the drive means.

[0014]

That is, in the present invention, only a predetermined frequency band is extracted from the image signal, and from this signal, a plurality of focus signal values are detected according to the degree of focus at a plurality of positions having different optical path differences. The focus state is determined from the focus signal value, the focus position is detected, and the drive means for changing the relative position between the image sensor and the photographing optical system along the optical axis direction is controlled.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic concept of the present invention will be described with reference to the drawings.

The present invention is characterized in that video signals at a plurality of positions near the image plane at the same time are used and three-point interpolation and two-point interpolation are simultaneously used. That is, as shown in FIG. 2, the image pickup device P for distance measurement is placed at a position equivalent to the position where the exposure surface E (the film surface in a single-lens reflex camera, the light receiving surface of the image pickup device in an electronic camera) is held at an equal distance u from the exposure face. And Q are placed. In this figure, I is the image plane of the target object, H1 is the first principal surface of the photographing optical system, H2 is the second principal surface of the photographing optical system, and dO is the distance from the first principal surface to the object (object distance). , DI is the distance from the second principal surface H2 to the image forming surface I (referred to as the image forming distance), and dE is the second principal surface H2.
To exposure surface E (called exposure distance), dP
Is the distance from the second principal surface H2 to the equivalent surface of the image sensor P, dQ
Is the distance from the second principal surface H2 to the image sensor Q equivalent surface.

Now, the difference between the focus signals of the image pickup devices P and Q changes according to the position of the image pickup device as shown in FIG. Here, Vp is the focus signal of the image sensor P, Vq is the focus signal of the image sensor Q, and the vertical axis represents the difference Vd (= Vp−Vq) between the focus signals. From this figure, it is understood that Vd = 0 when the photographing optical system is at the focus position, Vd> 0 when the photographing optical system is in the front focus, and Vd <0 when the projection optical system is in the rear focus. That is, by using the image signals at two positions near the image plane, it is possible to know whether or not the photographing optical system is in focus, and if it is not in focus, which is the defocus direction. The drawbacks (1) and (2) of are solved.

Next, the focus adjusting operation under such a structure will be described with reference to FIG. In FIG. 4, the horizontal axis represents time and the vertical axis represents the distance from the second main surface. dI, dE,
Since dP and dQ are respectively expressed as a function of time, dI (t), dE (t), dP (t), dQ (t)
Rewrite as. The change in each distance from time t0 is shown. There is a one-to-one relationship between the position X of the photographing optical system and the exposure distance dE, and dE = h {X} (3)

It is assumed that Then, XI that satisfies h {XI} = dI is the in-focus position. Further, the focus signal value of the image sensor P is Vp (t), and the focus signal value of the image sensor Q is Vq (t).
And When focus adjustment starts in FIG. 4, the image pickup element equivalent plane P crosses the image formation plane at time t2, and therefore Vp (t
_{The in-} focus position can be obtained by using three points of ₀ ), Vp (t ₁ ) and Vp (t ₂ ). As shown in FIG. 5A, the imaging distance dI (t _p ) is the same as in the equation (1), and when Vp (t ₀ ) ≧ Vp (t ₂ ), dI (t _p ) = dP (t ₁ ) -Ld / 2 · {Vp (t ₀ ) -Vp (t ₂ )} / {Vp (t ₁ ) -Vp (t ₂ )} (4) Further, Vp (t ₀ ) ≦ Vp (t ₂ ). ), DI (t _p ) = dP (t ₁ ) + Ld / 2 · {Vp (t ₂ ) −Vp (t ₀ )} / {Vp (t ₁ ) −Vp (t ₀ )} (4) ’ Here, t _p represents the time when the equivalent surface of the image sensor P becomes equal to the imaging distance, and Ld represents the imaging distance interval of the image. Then, the focus position XI (t _p) is represented by _{XI (t p) = h '} {dI (t p)} (3)'. h ′ {} is an inverse function of h {}. Further, as shown in FIG. 5B, t _p is Vp (t ₀ ) ≧ Vp (t ₂ ), then t _p = t1−Lt / 2 · {Vp (t ₀ ) −Vp (t ₂ ). _{} / {Vp (t 1)} - Vp (t 2)} ... (5) Further, Vp (t ₀₎ <for _{Vp (t 2), t p} = t1 + Lt / 2 · {Vp (t 2) -Vp (T ₀ )} / {Vp (t ₁ ) −Vp (t ₀ )} (5) ′. Here, Lt represents the imaging time interval of the image.

Further, at time t ₂ , the image forming plane is sandwiched between the image pickup element P equivalent surface and the image pickup element Q equivalent surface. Therefore,
The focus signals Vp (t ₂ ) and Vq are calculated by the two-point interpolation method.
(T ₂₎ focusing at time T _2, the position XI (t ₂₎ is determined. Since the images at the same time are used, the focus position can be correctly determined without the shape change of the focus signal curve as described in the defect (3) of the conventional technique. Then, the velocity M of the object can be obtained by the following equation. _{M = {XI (t 2)} -XI (t p)} / (t 2 -t p) ... (6)

FIG. 4 shows the case where the object is stationary, and M =
When the time becomes 0, the driving of the photographing optical system 1 is stopped at time tg, and the focus adjustment is completed. The star indicates the time and position where the photographing optical system 1 has stopped, and the thick line of dE indicates the change of dE due to the operation of the photographing optical system 1. Thus, at time tg, the exposure surface coincides with the image formation surface for the first time, so that the overshooting operation of the in-focus position can be eliminated, and the drawback (4) of the prior art is eliminated. However, an excessive movement may occur, which will be described in detail in the embodiment. Further, the speed of the moving body can be obtained from the equation (6), and in the case of FIG. 6, it is possible to predict the movement of the object from the speed M to the actual exposure time and perform focus adjustment (moving body predictive AF). , The drawback (3) of the prior art is solved. Further, unlike the prior art, there is no requirement that the BPE has a narrow band in order to obtain the speed of the moving body, and the speed detection accuracy can be improved. The first embodiment of the present invention will be described below.

In FIG. 7, 30 is a camera body, 1 is a photographing optical system, 31 is a diaphragm for limiting the amount of light, 33 is a film surface corresponding to an exposure surface, and 32 is a mirror, which is used by the photographing optical system during film exposure. It moves to guide the light flux to the film surface 33. At the time of distance measurement, the light flux from the mirror 32 is guided to the focus adjustment circuit 36 via the half mirror 35 and also to the finder 34. Reference numeral 16 is a motor for driving the photographing optical system in the optical axis direction, and the focus adjustment circuit 3
It is controlled by a control signal from 6. Further, the position X of the photographing optical system 1, the focal length f, and the F of the diaphragm 31.
The number F is input to the focus adjustment circuit.

The focus adjusting circuit 36 has a structure as shown in FIG. The light flux from the half mirror 35 enters the image sensor 39p via the half mirror 37 and the image sensor 39q via the mirror 38. Reference numeral 42 denotes a reduction optical system that captures an image formed in the size of the film surface 33 by the image sensor 39.
It has a reducing action for forming an image with a size of p, 39q. Further, the image pickup devices 39p and 39q are provided on the film surface 33.
Are located on the equivalent plane sandwiched at equal distances u and are controlled by the image pickup element drive circuit 40.
The image signal obtained by the image pickup device is amplified by the preamplifiers 4p and 4q and then input to the focus signal detectors 41p and 41q, and the focus signals Vp and Vq are output, respectively. The focus signal detector has a structure as shown in FIGS. 8 (a) and 8 (b). In the example shown in FIG. 8A, after the image signal is input to the BPF 5, only the signal at the image position designated by the distance measurement area designating circuit 21 is extracted by the gate circuit 8 and the detector 9 including a squarer is used. , A / D converter 10 and digital integration circuit 11 extract a focus signal having a predetermined spatial frequency. The digital integration circuit 11 is composed of an adder 12 and a latch circuit 13. In the example shown in FIG. 8B, first, after being converted into a digital signal by the A / D converter,
A predetermined spatial frequency component is extracted by the digital BPF, and the mean square value and mean value of the signal at the image position designated by the distance measuring area designation circuit 21 are calculated by the mean square value detection circuit 46 and the mean value detection circuit 47. Each requested,
The variance value shown in the following equation is obtained as the focus signal by the variance detection circuit. σ = (M2−M1 · M1) / (M1 · M1) (7) where M2: root mean square, M1: mean

Since this σ is a variance, it is not affected by a change in bias, and is also not affected by a change in gain because it is normalized by an average value. Therefore, even if there is a flicker or a sudden change in illumination light, it can be used as an accurate focus signal.

The focus signal Vp output from the focus signal detector 41p and the focus signal Vq output from the focus signal detector 41q are both input to the focus controller 43, and control signals for driving the photographing optical system 1 are provided. Output to the motor 16. The focus controller 43 is configured in detail as shown in FIG. 5
0 is a focus state detector, 51 is a three-point interpolator, (4)
The focus position and the time thereof are output to the motor control circuit 53 by the calculation based on the formula and the formula (5). Reference numeral 52 is a two-point interpolator, which has a structure as shown in FIG. 21B, and outputs the focus position to the motor control circuit 53. Reference numeral 54 is a photographing optical system parameter detection circuit, which is based on the equation (2).
Calculate FZP. Reference numeral 55 denotes a position detector, which determines an exposure distance dE from the position X of the photographing optical system 1 based on the equation (3), and calculates dP (= dE-u) and dQ (= dE + u) by a three-point interpolator 51, Output to the two-point interpolator 52. A motor control circuit 53 outputs a motor control signal to the motor 16.

Next, the operation of this embodiment having the above configuration will be described. First, when focus adjustment is started, exposure amount information (not shown) gives exposure amount information to the image pickup device drive circuit, the integration times of the image pickup devices 39p and 39q are set, and reading of image signals is started. It is assumed that this time is t ₀ and the subsequent read times are t ₁ , t ₂ , t ₃ .... Focus signals Vp (t ₀ ) and Vq (t ₀ ) of the read image signal are input to the focus state detector 50 by the preamplifier 4 and the focus signal detector 41. Focus state detector 50
Then, when | Vp (t ₀ ) −Vq (t ₀ ) | ≦ ε, the focus state is obtained. When Vp (t ₀ ) −Vq (t ₀ )> ε, the front focus state is Vp (t ₀ ) −Vq (t _{When 0} ) <ε, it is judged to be the rear pin state. Here, ε is an appropriate constant.

In the in-focus state, the focus signal difference is calculated again at time t ₁ , and again | Vp (t ₁ ) −Vq (t ₁ ).
When | ≦ ε, the focus adjustment operation is finished at that point. When | Vp (t ₁ ) −Vq (t ₁ ) | ≦ ε does not hold, Vp (t ₀ ) and Vq (t ₀ ) are obtained by two-point interpolation.
From the focus position XI (t ₀ ) at time t ₀ to Vp
(T ₁ ), focus position XI at time t ₁ from Vq (t ₁ ).
(T ₁ ) is calculated, M = {XI (t ₁ ) −XI (t ₀ )} / (t ₁ −t ₀ ) ... (8) The speed M is obtained from the formula, and the focus position is determined by the time lag until exposure. Predicts the moving distance, drives the photographing optical system 1 to that position, and finishes the focus adjustment.

When not in focus, the motor control circuit 53
The image pickup distance interval of the image is calculated from the image pickup optical system parameter dFZP and the focal length f, the motor drive speed is set to obtain this distance, and the image pickup optical system 1 is driven in the direction in which the exposure surface approaches the image formation surface. Start. Vp (t ₀ )> Vq
In the case of (t ₀ ), focus adjustment is performed according to the algorithm shown in FIG. That is, the focus signals Vp (t ₁ ) and Vp (t ₀ ) obtained at time t ₁ are compared (step S
1), time t if Vp (t ₁ )> Vp (t ₀ ).
Assuming that the focus position is very close at ₀ and t ₁ , Vp (t
_0), Vq (t ₀₎ If at time t ₀ from the focal position XI (t
₀ ) is calculated from Vp (t ₁ ) and Vq (t ₁ ) to obtain a focus position XI (t ₁ ) at time t ₁ (step S2), and M = {XI (t ₁ ) −XI (t ₀ ). } / (t ₁ -t ₀₎

From the equation, the speed M is obtained, the distance at which the in-focus position moves due to the time lag until exposure is predicted, the photographing optical system 1 is driven to that position, and the in-focus adjustment ends (step S).
3). When Vp (t ₁ )> Vp (t ₀ ), Vp (t
_{When n + 1} ) <Vp (t _n ) (step S4),
The three points of Vp (t _{n + 1} ), Vp (t _n ), and Vp (t _{n + 1} ) are used to perform the three-point interpolation as shown in the equations (4) and (5), and the focus position is obtained. XI (t _p ) and its time t _p are obtained (step S5). Then, Vp (t _{n + 1} ) and Vq (t
_{n + 1} 2-point or Vp (t _n)) of using the smaller two points of difference between the two points of Vq (t _n), performs a two-point interpolation focus position XI (t _{n +} 1) ( or XI (t _n), and obtains the time t _{n + 1} (or t _n) (step S6), M = {XI ( t n + 1) -XI (t p)} / (t n + 1 - t _p) ... (10)

From the equation, the speed M is obtained, the distance at which the in-focus position moves during the time lag until exposure is predicted, the photographing optical system 1 is driven to that position, and the in-focus adjustment ends (step S).
7). The same applies to the case of Vp (t ₀ ) <Vq (t ₀ ).

As described above, by using the three-point interpolation and the two-point interpolation together, the speed of the moving body can be accurately detected, and the focus adjustment can be performed in consideration of the time lag until the exposure.
Further, by using the image signals at two positions near the image plane at the same time, it is possible to know the focus state at the start of focusing and eliminate unnecessary driving of the photographing optical system. Further, it is possible to reduce the amount of overshooting of the in-focus position of the photographing optical system, and it is possible to reduce the discomfort of the photographer. Although the optical path difference between the image pickup device 39p and the image pickup device 39q is constant in this embodiment, the optical path difference may be changed appropriately depending on the focal length of the photographing optical system 1, the F number, and the like.

The focus adjusting circuit 36 uses only one image pickup device as shown in FIG. 11, and forms a light beam from the half mirror 37 on one half of the image pickup device surface and a light beam from the mirror 38 on the other half. You can In this figure, 61 is a selector for separating the image signals. Further, the half mirror 37 and the mirror 38 may be configured by using prisms. Further, instead of using the half mirror 37, the optical path length adjusting means 62 arranged immediately before the image pickup element may be used as shown in FIG. This optical path length adjusting means 62 is shown in FIG.
A member having a different optical path difference for each line as shown in (b),
At this time, the selector 61 functions to switch the signal for each field. Further, the optical path length adjusting means 62 may be configured by using liquid crystal or the like, and the optical path difference may be changed for each pixel.

Further, the two-point interpolation calculation uses two points sandwiching the in-focus position, but Japanese Patent Application No. 01-317 already filed by the present applicant.
By using the method described in No. 738, it is not always necessary to use two points that sandwich the in-focus position. The second embodiment of the present invention will be described below.

In FIGS. 4 and 6, the exposure surface did not coincide with the image forming surface before focusing, but in the case of FIG. 13 (a), an image is formed once with the exposure surface at time tg '. The surfaces are aligned, defocused, and focused again at time tg. This overshooting operation makes the photographer feel uncomfortable. Therefore, an embodiment in which the exposure surface and the imaging surface do not coincide with each other before focusing will be described below. It should be noted that members having the same functions as those in the previous embodiment are designated by the same reference numerals.

FIG. 14 shows a block diagram of the second embodiment of the present invention. The difference from the first embodiment is that the reduction optical system 42 of the focus adjustment circuit 36 is driven in the optical axis direction. Reference numeral 65 is its drive circuit.

Next, the operation of this embodiment will be described with reference to FIG.
(B), It demonstrates using FIG. First, when the focus adjustment is started, the integration time of the image sensor is set as in the first embodiment, and the focus state is detected. At this time, the position of the reduction optical system is adjusted so that the exposure surface becomes the center position of the image pickup element equivalent surfaces P and Q. If it is not in the in-focus state, the reduction optical system 42 is first driven in the direction of approaching the in-focus position (time t ₀ ). The photographing optical system 1 is not driven yet. Then, the drive of the photographing optical system 1 is started and the drive of the reduction optical system is stopped after the exposure surface is out of the region between the image pickup element equivalent surface P and the image pickup element equivalent surface Q (time t _E ). Then, as in the above embodiment, Vp (t ₁ ), Vp
3-point interpolation using (t ₂ ), Vp (t ₃ ), Vp
The in-focus position is detected by two-point interpolation using (t ₃ ) and Vq (t ₃ ), the in-focus position and the speed of the moving body are detected at time t ₃ , and the photographing optical system 1 considers the time lag until exposure. On the other hand, the reduction optical system 42 is driven at a high speed so that the exposure surface returns to the center position (initial position) of the image pickup element equivalent surfaces P and Q, and the focus adjustment is completed.

In this way, the photographing optical system 1 and the reduction optical system 42
It is possible to reliably prevent the photographer from feeling uncomfortable because the exposure surface and the image formation surface do not coincide with each other before focusing.

Although the reduction optical system itself is driven in this embodiment, the relative positional relationship between the exposure surface and the image pickup element surfaces P and Q is obtained by inserting a glass plate or using a liquid crystal, for example. May be changed. Of course, the image sensor itself may be driven. Further, Vp (t ₁ ), Vp (t ₂ ),
Three-point interpolation using Vp (t ₃ ) and Vq (t ₂ ), Vq
The in-focus position and the moving body speed can also be obtained from three-point interpolation using (t ₃ ) and Vq (t ₄ ). The third embodiment of the present invention will be described below.

Next, 3 at the same time near the image plane
An embodiment using the video signal at the position will be described. It should be noted that members having the same functions as those in the previous embodiment are designated by the same reference numerals.

FIG. 16 shows a block diagram of this embodiment. The difference from the first embodiment is that the half mirror 66, the image sensor 39r,
A preamplifier 4r and a focus signal detector 41r are provided. The half mirror 37 reflects 1/3 of the incident light, and the half mirror 66 reflects 1/2 of the incident light. The image pickup element equivalent surface R is at a position equivalent to the exposure surface, and is located at the center of the image pickup element equivalent surfaces P and Q. Now, with such a configuration, it is possible to detect the in-focus position by three-point interpolation with one image pickup. However, the detectable range is limited to the distance shown in FIG. Here, the horizontal axis is the distance from the second main surface, and the vertical axis is the focus signal value. Image sensor P,
If Q and R are located at dP, dQ, and dE, respectively, the range of dI at which the focus position can be detected is X1 or more and X2 or less. Here, X1 = (de + dp) / 2 = de−u / 2 (11) X2 = (de + dq) / 2 = de + u / 2 If all positions of the photographing optical system are X1 <dI <X2 (12)

If, then the focus position can be known without moving the photographing optical system at all, and the speed of the object can be known by two image pickups. If the expression (12) is not satisfied at all positions of the photographing optical system, it is necessary to drive the photographing optical system to this focus position detectable range.

Next, the operation in such a case will be described with reference to FIG.
Will be explained. In this figure, the shaded area indicates the focus position detectable range. First, when the focus adjustment is started, the integration time of the image sensor is set as in the first embodiment, and the focus state is detected. When it is not in the focused state, the driving of the photographing optical system 1 is started in the direction of approaching the focused position (time t ₀ ). Then, at time t ₁ , the focus signal Vp
(T ₁ ), Vq (t ₁ ), and Vr (t ₁ ) are used for three-point interpolation, and focus signals Vp (t ₂ ), V are obtained at time t ₂ .
Three-point interpolation using q (t ₂ ) and Vr (t ₂ ) is performed to detect the in-focus position and the speed of the object, and the in-focus adjustment is completed (time tg). In this way, 3 near the image plane at the same time
Focus adjustment can be performed by using the video signal at the position.

Although three image pickup devices are used in this embodiment, one image pickup device may be used to form images at three different positions. Also, two-point interpolation using two points of Vp and Vr, Vr and Vq, and Vp and Vq may be used together. Further, the image pickup elements P and R, and the image pickup element R are formed by using an appropriate optical path length changing means.
The optical path lengths of Q and Q may be changed. Further, a driving means for the reduction optical system may be provided and driven independently of the photographing optical system as in the second embodiment.

[0044]

As described above, according to the present invention, by using the image signals at a plurality of different positions near the image forming surface which are imaged at the same time, the focusing state can be known, and the photographic optical system is not used at the start of focusing. The drive can be eliminated. Further, by using the three-point interpolation method and the two-point interpolation method together, the in-focus position of the object at a plurality of times can be detected, and the moving object predictive AF becomes possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a focus adjustment circuit showing a first embodiment of an automatic focusing device according to the present invention.

FIG. 2 is a layout diagram of a photographing optical system and an image sensor for explaining the basic concept of the present invention.

FIG. 3 is a diagram showing how the difference between the focus signals of the image pickup devices P and Q changes depending on the position of the image pickup device.

FIG. 4 is a diagram showing a relationship between time, a second main surface, and a moving body speed for explaining a focus adjusting operation of the present invention.

5A is a diagram showing a relationship between time and a focus signal of the image sensor P, and FIG. 5B is a diagram showing a relationship between an imaging distance and a focus signal of the image sensor P.

FIG. 6 is a diagram showing the relationship between time, second main surface, and moving body speed for explaining another focus adjusting operation of the present invention.

FIG. 7 is a diagram showing a configuration of a camera body to which a focus adjustment circuit of the present invention is applied.

8A and 8B are block diagrams showing the configuration of a focus signal detection circuit.

FIG. 9 is a block diagram showing the configuration of a focusing controller.

FIG. 10 is a flowchart showing a focusing adjustment algorithm.
To.

FIG. 11 is a diagram showing another circuit configuration example of a focus adjustment circuit.

FIG. 12 (a) is a diagram showing an optical path length adjusting means arranged immediately before an image sensor, and FIG. 12 (b) is a diagram showing a structure of the optical path length adjusting means.

13 (a) and 13 (b) are diagrams showing the relationship between time, distance from the second main surface, and moving body velocity for explaining the second embodiment of the present invention.

FIG. 14 is a circuit configuration diagram for implementing a second embodiment of the present invention.

FIG. 15 is a diagram for explaining the independent drive of the photographing optical system and the reduction optical system.

FIG. 16 is a circuit configuration diagram for implementing a third embodiment of the present invention.

FIG. 17 is a diagram showing a detection range in the third embodiment of the present invention.

FIG. 18 is a diagram for explaining the third embodiment of the present invention.

FIG. 19 is a diagram showing a configuration of a conventional automatic focusing device.

20 is a diagram for explaining an interpolation calculation of the automatic focusing device in FIG.

21A is a diagram for explaining a focusing position calculation method using two points sandwiching the focusing position; FIG.
(B) is a figure which shows the circuit structure.

[Explanation of symbols]

4p, 4q ... Preamplifier, 36 ... Focus adjustment circuit, 37 ...
Half mirror, 38 ... Miller, 39p, 39q ... Image sensor, 40 ... Image sensor drive circuit, 41p, 41q ... Focus signal detector, 42 ... Reduction optical system, 43 ... Focus controller.

Claims (5)

[Claims] 1. An image pickup device for picking up an image formed by a photographing optical system at a plurality of positions having different optical path differences, and a relative position between the image pickup device and the photographing optical system. Driving means for changing along the axial direction, one or a plurality of image reading means for reading the electric charges accumulated in the one or a plurality of image pickup elements as an image signal, and the image signal read by the reading means A bandpass filter that passes only a predetermined frequency band, and a focus for detecting multiple focus signal values according to the degree of focus at multiple positions with different optical path differences from the output signal of this bandpass filter. Signal detecting means, focusing state determining means for determining a focusing state from a plurality of focus signal values read from the focus signal detecting means, and read from the focus signal detecting means. Focusing position control means for controlling the position of the photographing optical system by detecting the focusing position at a plurality of times by controlling the driving means from a plurality of focus signal values stored in the automatic focusing function. Focusing device. 2. An image formed by a photographing optical system is different from
One or multiple images taken at multiple positions with different optical path differences
The number of image sensors and the relative positions of the image sensors and the photographing optical system in the optical axis direction.
And a second drive unit for changing the optical path difference of the image formed on the image pickup device.
And an image of the electric charge accumulated in the one or more image pickup devices.
One or more image reading means for reading as a signal
And a predetermined frequency from the image signal read by this reading means.
A bandpass filter that passes only the wavenumber band and a different optical path from the output signal of this bandpass filter
Multiple focus signals depending on the degree of focus at multiple positions with different differences
Signal for detecting focus signal and a plurality of focus signals read from the focus signal detecting means
Focus state determination means for determining the focus state from the value, and a plurality of focus signals read from the focus signal detection means
Controlling the first and second driving means from a value,
Controls the position of the shooting optical system by detecting the in-focus position at the time
An automatic focusing apparatus comprising: 3. The in-focus position control means has a first in-focus position detection means for obtaining an in-focus position from the focus signal values of three image signals imaged at different times, and 2 having different optical path differences. 3. The automatic focusing device according to claim 1, further comprising a second focusing position detecting unit that obtains a focusing position from focus signal values of two image signals captured at two positions at the same time. Focusing device. 4. The in-focus position control means includes an in-focus position detection means for obtaining an in-focus position from focus signal values of three image signals imaged at the same time at three positions having different optical path differences. The automatic focusing device according to claim 1, further comprising: 5. The focus signal detecting means comprises means for normalizing a variance value of the output signal of the bandpass filter with an average value of the output signal of the bandpass filter. The automatic focusing device described in a few items.