JPS60156028A - Auto-focusing device - Google Patents

Abstract

PURPOSE:To make the operation processing for correction of a defocus signal unnecessary by starting to count a lens movement extent signal from an average position of a lens which is in course of storage of electric charge and comparing the extent of movement of the lens with a defocus quantity. CONSTITUTION:Counting of lens movement pulses is started at a time t2, when a photographic lens 1 reaches an average position Z2 of the photographic lens 1 in electric charge storage periods (t1-t3), without correcting a defocus signal (d) corresponding to said average position Z2 generated at a time t4, and an extent P of movement of the lens after the time t2 and the defocus signal (d) are compared with each other to control the photographic lens 1. A storage time control means 5 monitors an average quantity of electric charge of an image sensor to command termination of storage (t1-t4). Pulse counting of a lens movement extent detecting means 9a is started at the time t2 when the quantity of electric charge is 1/2 of a prescribed value, and electric charge is transferred to a means 9b at the time t4, and the next cycle is started from the time t4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an automatic focusing device for a TTL camera.

(Background of the invention) ! f.

Conventionally, silence detection is performed through a photographic lens to obtain a defocus signal corresponding to the amount of deviation of the photographic lens from the in-focus position (hereinafter referred to as defocus amount), and the photographic lens is moved in the focusing direction by moving the photographic lens. An automatic focusing device is known that feeds back a lens movement amount signal indicating the amount of defocus, compares it with the defocus signal, and stops driving the photographing lens when the two match, and brings the photographic lens to the in-focus point.

In such an automatic focusing device, a charge-accumulating dust image sensor such as C is used as a focus detection image sensor.
When using an OD or when a microcomputer or the like is used to perform calculation processing to obtain a defocus signal, the photographic lens may not be connected during the charge accumulation time of the charge storage type image sensor or during the calculation processing time. When the lens is being driven, it is necessary to correct the defocus signal by taking into account errors caused by the movement of the photographic lens, as disclosed in Japanese Patent Laid-Open No. 56-78823.

壬 The reason why such correction is necessary will be explained in detail below.

A case in which no correction is performed will be described in detail.

FIG. 1 is an operational diagram for explaining this, in which the vertical axis represents the lens position or defocus signal, and the horizontal axis represents time. Assume that charge accumulation in the focus detection image sensor starts at time t1. The position of the photographing lens at this time t is zl, and the in-focus position is zs<'=o)
Therefore, the photographing lens is driven along the solid line in the direction of the in-focus position. Time t.

At , the charge accumulation of the focus detection image sensor ends. After this time t, preliminary calculations (hereinafter collectively referred to as calculation processing) for transferring the image sensor output and obtaining a defocus signal are performed, and the calculation processing ends at time t4.

On the other hand, the photographing lens was at position z8 at time t1, but was driven during the accumulation time and moved to position zsK at time t3.
It is also driven during the calculation processing time and moves to position z4 at time ζ.

At time t4, a defocus signal is output, and from this point onwards, the driving of the photographing lens is controlled by this defocus signal and the lens movement amount signal from this point on. But at time t.

The defocus signal output to is the average position z of the photographing lens during the accumulation time of the charge accumulation type image sensor.
Since it is a defocus signal corresponding to 2, if this defocus signal is used as is, the focus position Z, (=O
), at time point 14 when there is a deviation amount of z4, it is recognized that there is a deviation amount of z2. As a result, this deviation amount is 2. When the photographic lens is driven to zero, the photographic lens moves to the true focus position 2. 2. Gara 2. The lens was driven to the position z6 (=Z4 Zz'), which was shifted by a certain amount, and the focusing operation was not accurate. Then, since the lens is driven to the wrong in-focus position again, the primary focus detection is driven in the opposite direction from this position z6, causing problems such as hunting in the vicinity of the in-focus position z. Therefore, as mentioned above, it is necessary to correct the defocus signal.

As a means to solve this problem, it is known to correct the defocus signal z2 at time t4 by (Z, -Z,) as disclosed in Japanese Patent Application Laid-Open No. 56-78823 as mentioned above. . By adding such a correction, the corrected defocus signal will be corrected at time t.
This represents the defocus amount z4 of the photographing lens at the true focus position 2.4. The lens will be stopped at exactly 2. It becomes possible to drive the

FIG. 2 is a block diagram of the above-mentioned conventional automatic focusing device that applies correction for (Z, -Z,), in which 1 is a photographing lens, 2 is
3 is a main mirror, 3 is a sub-mirror, 4 is a charge accumulation type image sensor, 5 is an accumulation time control means for the charge accumulation type image sensor, 6 is an arithmetic processing means for calculating a defocus signal d, and 7 is an orcus signal d. 8 is a driving means for the photographing lens l; 9 is a lens movement amount detection means for detecting the movement amount of the photographing lens 1 and generating a lens movement amount signal P;
Reference numeral 10 denotes a lens drive control means for receiving the corrected defocus signal d' and the lens movement amount signal P and controlling the lens drive means 8; 11 generates a pulse for each unit movement amount of the photographing lens 1 fixed at Fjr; This is lens movement pulse generating means.

The operation of the conventional automatic focusing device shown in FIG. 2 is as follows.

Passes through the photographic lens 1 and main mirror 2, and then passes through the sub mirror 3.
An image of the focus detection light beam reflected by the charge accumulation type image sensor 4 is formed on the charge accumulation type image sensor 4. The charge accumulation type image sensor 4 starts photoelectric conversion charge accumulation under the control of the accumulation time control means 5 (t,).

The accumulation time control means 5 monitors the average amount of charge in the charge storage section of the charge storage image sensor 4, detects that the average amount of charge has reached a predetermined value, and at that point, the storage time control means 5 detects that the average amount of charge has reached a predetermined value. command to end storage (
t3). When the charge accumulation type image sensor 4 finishes the accumulation (t), it sends the image sensor output i corresponding to the image formed on the image sensor to the arithmetic processing means 6,
The arithmetic processing means 6 obtains a defocus signal d from K by arithmetic processing the image sensor output i.

The lens movement pulse generation means 11 is configured to generate a pulse every time the photographing lens 1 moves by a predetermined unit movement amount in the optical axis direction, and the lens movement amount detection means 9 is configured to generate a pulse when the arithmetic processing means 6 defocuses. At the time when the signal is generated, that is, at the end of the calculation process t4, the count up to that point is cleared,
Counting of pulses corresponding to the movement of the lens l is newly started, and the movement amount of the photographic lens l from this point, that is, the unit movement (pulse count number x unit) is output as a lens movement amount signal P.

The defocus signal correction means 7 uses the defocus signal d
At the same time, the accumulation time control means 5 receives a signal indicating the start and end of accumulation, and the arithmetic processing means 6 receives a timing t4 at which the arithmetic processing ends, and the lens movement amount detection means 9 determines the lens movement. Receive the amount signal P and determine the amount of lens movement (21 to z3) during the accumulation time (11 to ts)
, lens movement amount (Zs
~Z, ) and use this to calculate (1, ~ts
), the defocus signal d corresponding to the average position z2 of the photographic lens at time t is expressed as the defocus signal d corresponding to the average position z2 of the photographic lens at
The lens drive control means 10 receives the corrected defocus signal d' and the lens movement amount signal P, and the lens drive control means 8
A control signal is output to drive the lens in the direction corresponding to the sign of the defocus signal d' corrected for (When the number of pulses x unit movement amount n reaches the amount of deviation corresponding to the defocus signal d'i/C, a control signal is output to the lens driving means 8 to stop driving the lens. Lens driving The means 8 drives the photographic lens element to the in-focus position [ZS] based on the above control signal.

Kt at the same time while driving the photographing lens 1 as described above.
Automatic focusing is performed using a defocus signal corrected through load accumulation and arithmetic processing.

However, the conventional automatic focusing device as described above has the disadvantage that the defocus signal correction means 7 must perform arithmetic processing to correct the defocus signal d, making the configuration complicated. .

(Objective of the Invention) An object of the present invention is to solve these drawbacks and provide an automatic focusing device that can perform automatic focusing operation with a simpler configuration.

(Summary of the Invention) The present invention starts counting the lens movement amount signal P, that is, the pulse, from the time t2 when the photographing lens l reaches the average position z2 of the photographing lens during the charge accumulation time (it~ta), The technical point is to eliminate the need for arithmetic processing for correcting the defocus signal d by comparing this lens movement iP with the defocus amount d generated at time t4.

(Example) The operating principle of the automatic focusing device according to the present invention will be explained using FIG.

In FIG. 1, conventionally, the defocus signal d corresponding to the average position z2 of the photographing lens 1 during charge accumulation (11 to ts) generated at time t4 is changed to the defocus signal d corresponding to the position z4 of the photographing lens 1 at time t4. The focus signal d' is corrected, and the lens movement pulses of the photographing lens 1 are counted from time t4. Therefore, the lens movement amount signal P from time t4 onward is compared with the corrected defocus signal d', and the lens movement pulse of the photographing lens 1 is corrected. However, in the present invention,
During the charge accumulation time (1, ~ts) without correcting the defocus signal d corresponding to the average position z2 of the photographing lens 1 during the charge accumulation time t, ~t, which occurred at time t4.
Counting of the lens movement pulses of the taking lens 1 starts from time t2 when the taking lens 1 reaches the average position z2 of the taking lens 1, and therefore the taking lens movement amount 2 after time t2 and the uncorrected defocus signal d are By comparison, the drive of the photographing lens 1 is controlled.

Further, the time point t2 when the photographing lens 1 reaches the average position Z of the photographing lens 1 from t1 to t during the charge accumulation time is determined, for example, as follows.

The accumulation time control means 5 is a charge accumulation type image sensor 4.
The average charge amount of the charge storage unit (not shown) is monitored, and the charge storage of the charge storage type image sensor 4 is terminated at the time t when the average charge amount reaches a predetermined value. If the driving speed is approximately constant, the time t when the average charge amount reaches a value of % of the predetermined value is the average position of the photographing lens 1 during the charge accumulation time (1° to ts), so the photographing lens This is considered to be the point when l has reached. Therefore, the point in time when the average charge amount of the image sensor 4 reaches % of the predetermined value is the average position 2. The time point t2 can be set as the time when .

FIG. 3 is a block diagram of an embodiment of an automatic focusing device according to the present invention, in which the same numbers as in FIG. 2 are used. 1 is the same as each means in FIG. Omit.

In Fig. 3, 9a is a lens moving pulse generator JQII.
The first one counts the lens movement pulses output from the
The lens movement amount detection means 9b is a second lens movement amount detection means that also counts the lens movement pulses from the lens movement pulse generation means 11.

Next, the operation of the automatic focusing device shown in FIG. 3 will be explained.

Passes through the photographic lens 1 and main mirror 2, and then passes through the sub mirror 3.
A subject image is formed on the charge accumulation type image sensor 4 by the focus detection light beam reflected by the charge accumulation type image sensor 4 . The charge accumulation type image sensor 4 starts photoelectric conversion charge accumulation under the control of the accumulation time control means 5 (tl). Accumulation time control means 5
is a charge accumulation part (not shown) of the charge accumulation type image sensor 4
By monitoring the average charge amount of υ, it is detected that the average charge amount has reached a predetermined value, and at that point, the charge storage type image sensor 4 is commanded to end the storage (t4).
. When the charge accumulation type image sensor 4 finishes accumulation (t
4) Sends the image sensor output i corresponding to the image formed on the image sensor "4" to the arithmetic processing means 6,
The arithmetic processing means 6 obtains a defocus signal d by arithmetic processing the image sensor output i. Note that the arithmetic processing means 6 of this embodiment performs arithmetic processing on the image sensor output i to determine the image forming plane of the photographing lens 1 and the light receiving surface of the image sensor 4 (the light receiving surface and the film surface (not shown) are at a conjugate position. In order to reduce the amount of deviation between the camera and the camera (which is placed on the film) and to make the amount of deviation between the camera and the camera zero (in other words, in order for the photographic lens 1 to form the subject image on the film surface), Photography lens 1
A signal representing how much the object must be moved is output as a defocus signal d. That is, the defocus signal d output by the arithmetic processing means 6 corresponds to the amount of lens movement.

On the other hand, the lens movement pulse generating means 11 is configured to generate one pulse each time the photographing lens 1 moves by a predetermined amount of movement in the optical axis direction.

Further, the accumulation time control means 5 controls the average charge amount of the charge accumulation section of the charge accumulation type image sensor 4 to be a percentage of the predetermined value.
It is detected that the pulse count has been reached, and at that time point t2, a pulse count start control signal is issued to the first lens movement amount detection means 9a. The first lens movement amount detection means 9a receives the lens movement pulse from the lens movement pulse generation means 11 and the pulse count start control signal from the control means 5, and receives the pulse count start control signal from the control means 5 at time t.
, the value counted at 1 is reset and pulse counting is started again.

Next, the arithmetic processing means 6 generates a transfer command signal to the first lens movement amount detecting means 9a at time t4 after completing the arithmetic processing and outputting the defocus signal d.

The lens movement amount detection means 9a of the camera 1 receives the transfer command signal and transfers the count contents in its case to the second lens movement amount detection means 9b at time t4.

The second lens movement amount detection means 9b has the count content of the first lens movement amount detection means 9a set at time t4, and also receives a lens movement pulse from the lens movement pulse generation means 11 and further adds a count. By doing the above, the second lens movement amount detection means 9b always receives a signal corresponding to the lens movement amount from time point 1t. Output.

The lens drive control means 10 receives the photographing lens movement amount signal P' and the defocus signal d outputted from the second lens movement amount detection means 9b from the time t2, and compares them to determine that they are in a predetermined relationship. (for example, when the two match), a control signal is output to the lens driving means 8 in the same manner as explained in FIG.

The lens driving means 8 receives the above control signal and drives the photographing lens 1 to the in-focus position.

Thereafter, new charge accumulation in the image sensor 4 is started again from time t4 (corresponding to 1 m), and when the accumulation is finished (corresponding to ts), the defocus amount d is calculated by the calculation processing means 6, and the defocus amount d is calculated by the calculation processing means 6. The operation is finished (1+
The focus detection operation described above is periodically repeated. And t.

The output d of the arithmetic processing means 6 and the output of the second lens movement amount detection means 9b at the time? Based on this, the lens drive control means 10 drives the lens 1 from the arithmetic processing end time t4 to the next arithmetic processing end time 1 (corresponding to 1+).

The first lens movement amount detecting means 9a starts counting new pulses every time the time point corresponding to t comes, and starts counting new pulses every time the time point corresponding to t4 comes, due to the periodically repeated focus detection operation. The contents are transferred to the second lens movement amount detection means 9b.

That is, the first lens movement amount detection means 9a performs counting only from the time corresponding to t2 to the time corresponding to t4. 'Also, the second lens movement amount detection means 9b further adds a pulse count to the transferred count value from the time corresponding to t4, and adds the pulse count to the next calculation end time (corresponding to ta).
Count on the box. Then, at the end of this calculation (t4
), the count value up to that point is reset and a new count value transferred from the detection means 9a is set.

However, if the in-focus state is obtained by the end of a certain calculation, that is, the photographic lens 1 is at the in-focus position 2. Needless to say, if the detection means Pb is positioned at (Pd), the detection means Pb does not count from then on.

In FIG. 4, the photographic lens 1 is moved to the in-focus position Z? according to the defocus signal. (=0), while the charge accumulation for obtaining the next new defocus signal starts from time tf, and during the charge accumulation time, the photographing lens 1 moves to the in-focus position tZ? at time t. It is a figure explaining operation of the above-mentioned example when it reaches.

In FIG. 4, charge accumulation in the charge accumulation type image sensor 4 starts at time t: and ends at time t;, and the subsequent arithmetic processing for obtaining a defocus signal ends at time t'4.

In this case, the defocus signal that is output at time t'4 is different from the one shown in FIG. bl, bow) (z4 in FIG. 4) differs from the position of the taking lens at time t≦, which is half of the accumulation time (t Hull et al.).

Therefore, the lens movement amount signal P' from time t4 and time t'
Comparing the defocus signal d at 4, the photographing lens 1
Even if you drive the lens, it is not possible to reach the focused point accurately.

Next, an example of improvement for solving the above-mentioned inconvenience will be described. This improvement is obtained by adding the circuit shown in FIG. 5 to the additional embodiment shown in FIG.

In FIG. 5, the control stop circuit 12 receives signals from the accumulation time control means 5 and the lens drive control means 10, and during the charge accumulation time (t, L-1i), the control stop circuit 12 enters the in-focus state 2. If a focused state is obtained during the charge accumulation time, a signal is sent to the arithmetic processing means 6, and the output of the means 6 is forcibly set to zero (d=o). do.

At the same time, a signal is also sent to the control means 5 to clear the charges accumulated in the image sensor 4 at this point and cause the image sensor 4 to start accumulating new charges again. The rest of the structure of this improved example is exactly the same as the embodiment shown in FIG. Therefore, when the storage time of the image sensor 4 ends (t4), if the lens drive has already ended before the end of this storage time, the lens drive control means 10 controls the detection of the data that is to occur at time t; The focus signal is set to zero only this time, and a control signal is issued to the lens driving means 8 to stop driving the lens.

In fact, the completion of lens driving during the charge accumulation time (t~ts) means that the photographing lens has reached at least the in-focus position for the previous defocus signal, so the defocus signal is There is no major inconvenience if you just ignore it.

Note that at time t when the end of lens driving is detected during the charge accumulation time (1; -ti), the entire automatic focusing device shown in FIG. It may be configured to start accumulation.

By doing the above, the time from time t7 to time td in FIG. 4 is not wasted time, so it can be expected that responsiveness will be improved.

Further, in the embodiment shown in FIG. 3, the accumulation time control means 5 monitors the average amount of charge in the charge accumulation section of the charge accumulation type image sensor 4, and ends charge accumulation when the value reaches a predetermined value. , %K rx of its predetermined value; E+″″1″
t' V y X$9/' A/ x (D h')
7htPm.

let That is, it was stated that detection of the amount of lens movement is started. However, the present invention is not limited thereto; for example, the accumulation time control means 5 monitors the peak value of the amount of charge in each charge accumulation section of the charge accumulation type image sensor 4, and starts charge accumulation when the peak value reaches a predetermined value. % of its predetermined value
The configuration may be such that the detection of the lens movement amount starts from the point in time when the amount of lens movement is reached. Alternatively, the accumulation time of the charge accumulation unit image sensor 4 may be controlled in some other manner so that a signal for starting detection of the lens movement amount may be generated at an intermediate point in the accumulation time.

In this way, the present invention starts detecting the amount of lens movement from approximately the middle of the charge accumulation time.

(Effects of the Invention) As described above, according to the present invention, automatic focusing can be performed with a simple configuration and accurate focusing operation without special calculation processing for correcting a defocus signal. It becomes possible to realize a focusing device. Furthermore, since no special calculation is required to correct the defocus signal, an automatic focusing device with high responsiveness can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the operation of an automatic focusing device, FIG. 2 is a block diagram of a conventional automatic focusing device, and FIG. 3 is a block diagram of an automatic focusing device showing an embodiment of the present invention. FIG. 4 is a diagram explaining the operation of the automatic focusing device near the in-focus point, and FIG. 5 is a block diagram showing an improved example of the embodiment of FIG. 3. (Explanation of symbols of main parts) 1...Photographing lens, 2...Main mirror, 3...
Submirror, 4... Charge accumulation type image sensor, 5.
... Accumulation time control means, 6... Arithmetic processing means, 7...
- Defocus signal correction means, 8... Lens drive means, 9... Lens movement amount detection means, lO... Lens drive control means, 11... Lens movement pulse generation means, 9
a...first lens movement amount detection means, 9b...second
means for detecting the amount of lens movement. Applicant Nihon Kogaku Kogyo Co., Ltd. Agent Escort Takao Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 == Luck 1 2

Claims (1)

[Scope of Claims] 1) A charge accumulation type image sensor that photoelectrically converts a subject image; Accumulation time control means for controlling charge accumulation time of the charge accumulation type image sensor; A sub-arithmetic processing means for computing the output and calculating the defocus amount from the in-focus position of the photographing lens; Lens movement pulse generation means for generating pulses in accordance with the movement of the photographic lens; Output of the lens movement pulse generation means. a lens-shifting detection means for counting pulses and detecting the amount of movement of the photographing lens; and a lens driving means for driving the photographing lens; controlling the driving of the lens driving means according to the defocus amount and the lens movement amount; In an automatic focusing device comprising: a lens drive control means; the accumulation time control means generates a first timing signal at approximately the middle of the charge accumulation time; and the arithmetic processing means terminates the operation. The lens movement amount detection means is configured to generate a second timing signal at the time when the defocus signal is generated, and the lens movement amount detection means includes a first lens movement amount detection means and a second lens movement amount detection means. The first lens movement amount detecting means starts counting the -lens movement pulses from the time when the first timing signal is generated, and when the second timing signal is generated, the first lens movement amount detecting means starts counting the lens movement pulses from the time when the first timing signal is generated.
At the same time as transferring the count contents of the lens movement amount detection means to the second lens movement amount detection means, the second lens movement amount detection means further updates the count contents by omitting the lens movement pulse. The lens drive control means (k) compares the amount of movement of the taking lens corresponding to the lens movement pulse count contents of the defocus signal and the second lens movement amount detection means, and controls the amount of movement of the lens. An automatic focusing device, characterized in that it is configured to control a drive means.