JPS63304233A - Automatic focusing device for camera - Google Patents

Abstract

PURPOSE:To smoothly drive a photographing lens to a focusing point without unstable actions such as hunting, etc., by detecting the accurate position of the focusing point even in case of driving the photographing lens during the charge accumulating time of an image sensor. CONSTITUTION:When the photographing lens 13 moves while accumulating the charges of the charge accumulation type image sensor 15, the moving position of the photographing lens 12 and what is called defocusing in the position are continuously detected. A functional information generating means 21 generates the functional information between defocusing and the movement quantity of the photographing lens 12 and a recording means reads and stores the functional information of the functional information generating means 21 at both points of the charge accumulating start point and completion point of the charge accumulation type image sensor 15. And the moving direction and movement quantity of the photographing lens to the focusing position are computed from the functional information at both points and the position of the photographing lens 12 at present. Thus, the photographing lens can be surely located in the focusing point.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an automatic focusing device for a camera that moves a photographic lens during a focus detection operation to start a focusing operation.

``Prior Art'' Conventional automatic focus adjustment devices for cameras use a charge storage Mli type image sensor to receive the light flux passing through the photographic lens, and use its output to perform focus detection processing to detect defocusing of the photographic lens. A focus detection device is known.

Furthermore, an automatic focus adjustment device is known that converts the defocus detected based on the relationship between the movement of the photographing lens +jJl and the defocus, and drives the photographic lens by that amount to focus. There is.

Furthermore, there is a known technology that temporally overlaps the focus detection operation (image sensor charge accumulation, arithmetic processing) and the focusing operation (driving the photographic lens) to improve the responsiveness of the automatic focus adjustment operation. ing.

``Problems to be Solved by the Invention'' However, in such conventional automatic focusing devices for cameras, the relationship between the amount of movement of the photographic lens and defocus varies depending on the position of the photographic lens, and the relationship between focus detection operation and focusing differs depending on the position of the photographic lens. Since the photographing lens is moved during the focus detection operation and overlaps with the operation in time, the relationship between the amount of movement of the photographing lens at the position of the photographic lens and defocus at the time determined as the result of the focus detection calculation is If you convert the detected defocus into the driving amount of the photographing lens and drive it, it may go too far or not enough.
There was an F1 issue.

The problem will be explained in detail.

As shown in FIG. 4, consider a case where the photographing lens 12 is moved along the optical axis O1 while performing a focus detection operation, that is, while performing a charge storage operation of a charge storage type image sensor.

The lens position t at the midpoint of the charge Ti accumulation time of the charge accumulation type IIi image sensor is defined as zl, and the lens position at the time when charge accumulation is finished γ and the output of the image sensor is processed to find the defocus dl is Z2. shall be.

Conventionally, when the defocus di is determined at a lens position of 2 tzt, the lens movement amount △2 to the in-focus point is determined as follows. was required.

In other words, the defocus d1 is set to the lens position 1. The relationship between defocus d and lens movement amount △2 (function ΔZ-[
2(d)), it is converted into a lens movement amount Δ2 as shown in equation (1).

ΔZ −rz(dD
-(1) Next, defocus di is lens position 2t2
．． This is the defocus at (the midpoint of the charge accumulation time), and the current lens position is z2, so the difference between them is Z, -Z,
is corrected as shown in equation (2) to find the lens movement amount Δz2 from the lens position aiz to the in-focus point.

△L −ΔZ −(Zg−Zl) −f2(di)−(Z, −Zl) −(
2) If the photographic lens is driven from the lens movement amount Δz obtained in (2) and the straddle lens position W1't and stopped, the in-focus point will be reached.

However, when converting the defocus di to the lens movement amount ΔZ, the relationship between the defocus d at the lens position z2 and the lens movement amount Z in equation (1) (function ΔZ−
f2(d)).

Originally, the defocus di is the defocus at the lens position 21z, so the relationship between the defocus d at the lens position 21z and the lens movement amount (function Δ2-f l
(d)) is used to move the lens as shown in
It is necessary to convert it to Δz.

Δz −n(aD
=.(3) In this case, if the amount of lens movement from the lens position 2tzt to the in-focus point is ΔZ1, then ΔZ can be found by equation (4).

△Z, -ΔZ -(2,-2,) -rl(dl)-(z*-zl) -C4)
Therefore, the accurate lens movement amount △2 from the lens position Z2 to the in-focus point determined by equation (4). An error E as shown in equation (5) occurs between the amount of lens movement Z2 and the lens movement amount Z2 determined by equation (2) in the conventional method.

E −ΔZI−ΔZ2 − fl(dl)−f2(d2) ・・
・(5) For normal photographic lenses, the relationship between defocus d and lens movement gJ and ΔZ is approximately the same for all photographic lenses from close range (■), and the error E obtained by equation (5) is Lens movement amount Δz which can be ignored and found by formula (2)
There was no problem because the focal point could be reached by moving the photographing lens by 2 from the lens position 2122.

However, in a photographic lens having a macro area, the relationship between the defocus d and the lens movement amount ΔZ changes significantly in the macro area, and the error E obtained by equation 5) cannot be ignored.

In addition, in the macro area, if the subject is dark and the charge storage time of the 81-type image sensor becomes long,
During this time, the amount of movement of the photographing lens driven also increases.

That is, in FIG. 4, the gap between the lens position a z r and the lens position 2 tzt also increases, and the
The difference between
4 shows the functional relationship between the defocus d and the lens movement amount ΔZ at a lens position of 2ZZ, .

If f2(d), then the defocus di is l■
If there is
Therefore, in such a case, the lens shift determined by equation (2)! ll amount Δ2. There was a problem in that when the photographing lens was driven from the take lens position ZR, the focal point was moved too far by 0.5 mm.

"Means for Solving the Problems" What is the gist of the present invention to achieve these objects?

In an automatic focus adjustment device of a camera that moves a photographing lens (12) during a focus detection operation to start a focusing operation.

An image sensor (15) with a charge storage 1affi that receives the light flux that has passed through the photographing lens (12) of the camera, and an image sensor (15) that receives the output of the image sensor (15) and receives the light flux that has passed through the photographic lens (12) of the camera.
); and a defocus detection means for detecting defocus of an image forming plane with respect to a predetermined image forming plane.

lens position detection means for detecting the position of the photographic lens (
20), and function information generating means (21) for generating functional information indicating a functional relationship between defocus and the amount of shift S of the photographing lens (12) in accordance with the output of the lens position detecting means (20).
) and the function information at both the start and end points of the charge 8m of the image sensor (15), or the charge Mllill time and a predetermined time during the charge accumulation time. and storage means for reading and storing the function information generated by the generation means (21).

a drive calculation means for determining the drive direction and drive of the photographing lens (12) based on the defocus detected by the defocus detection means and the function information stored in the storage means; and the drive calculation means receiving the output of the photographing lens (12)
and a drive control means (18) for controlling the drive of the camera.

"Operation" When the photographic lens is moving while the charge accumulation type image sensor is accumulating the charge, the movement position of the photographic lens and the so-called defocus at that position are constantly detected, and the lens position detection signal and the Based on the focus detection signal, the function information generation means defocuses and moves the photographic lens! The recording means generates function information between the charge accumulation start time and the end time of the charge accumulation type image sensor, or the charge accumulation start time and the charge i amount.
The function information of the function information generating means at either a predetermined time point or both time points during the waiting time is read and stored.

Using the function information at both points in time and the current position of the photographing lens, the direction and amount of movement of the photographing lens to the in-focus position can be calculated, and based on this, the photographing lens can be reliably positioned at the in-focus point, making it possible to avoid overshooting. Unsatisfied inquiries can be resolved.

"Example" Hereinafter, one embodiment of the present invention will be described based on the drawings.

1 to 4 show a first embodiment of the present invention.

As shown in FIG. 1, inside the camera body 1O, t! Shadow lens 12. A main mirror 13 and a sub-mirror 14 are provided.

An image sensor 15 is provided at a position where the reflected light from the sub-mirror 14 is incident, and the image sensor 15 is connected to a central processing unit 21 (CPU) 16.

The central processing unit fil (cpu) 6 includes an encoder 17 that generates pulses as the photographing lens 12 moves.
is connected. The central processing unit (CPU) l6 has a motor 19 for driving the photographic lens based on the drive signal.
A drive control means 18 is connected thereto.

Furthermore, a function information generation means 21 is connected to the central processing unit (CPII) l6.
1 is connected to lens position detection means 20.

A display means 22 is connected to the central processing unit (CPU) 16.

Next, the effect will be explained.

The image sensor 15 performs photoelectric conversion on a subject image formed by a light flux that passes through the photographing lens 12 and the main mirror 13 and is reflected by the submirror 14 for a charge accumulation time according to the brightness of the image, and outputs the data to the central processing unit 6. do. The charge accumulation time of the image sensor 15 is determined by the central processing unit gi16.
It is controlled by a central processing unit that sends control signals such as start and end of charge accumulation. l16 outputs to the image sensor-5.

The lens position detecting means 20 detects the position of the photographing lens 12 and provides information on position 212 degrees to the function information generating means 21. The function information generating means 21 generates the obtained lens position and information Z.
. The relationship between the defocus d and the lens shift amount Δ2 in , that is, the function information ΔZ −f, (d) is generated.

As shown in FIG. 4, the lens position 212. ．． In Z, the function information generating means 21 generates ΔZ-f, (d), ΔZ-
Each function of f*(d) is generated.

The following can be considered as specific data of the function information.

(1) The function ΔZ −fll(d) is the −order number ΔZ m
If it can be approximated by alIX d, the coefficient 87 may be generated as data.

(2) If the function ΔZ −fn(d) can be approximated by the polynomial equation 6, a set of coefficients (a, (m)) may be generated as data.

By the way, the central processing unit W116 controls the charge accumulation time of the image sensor 15 as described above, and at the midpoint of the charge accumulation time, the function information Δ is output from the function information generation means 21.
The receiver takes and memorizes Z −f, (d).

At the same time, it starts counting pulses from the encoder 17 and starts monitoring the amount of lens movement.

Central processing after finishing charge accumulation? The C position 16 receives the subject image data from the image sensor 15 and performs a predetermined focus detection calculation process on the data to determine the defocus d (defocus amount and defocus direction).
seek.

Is it central processing when the defocus d is determined? ti16 finishes counting the pulses from the encoder 17, and determines the lens movement a fiZ s from the midpoint of the charge accumulation time.

Of course, if the photographing lens is not driven during the charge accumulation time, the lens shift 491 N Z s becomes O.

In addition, the function information ΔZ −f, (d) allows the defocus d
is converted into lens movement amount Δ2, and further lens movement MZs
As shown in equation (6), the amount of movement Δ2 of the photographic lens is obtained by subtracting
Convert to

ΔZ −f, (d) −Z, −(6
) Lens shift obtained by equation (6)! ll@Δ2 is the amount of lens movement from the photographing lens position to the in-focus point at the time when the lens movement amount Δ2 is calculated. Therefore, lens movement amount Δ2
By controlling the display means 22 according to the sign and absolute value of , information such as front focus, rear focus, and focus can be displayed.

Further, the central processing unit 2116 inputs the lens movement amount Δ2 to the drive control means 18 as drive amount data. The drive control means 18 rotates the motor 9 forward or reverse based on the sign of the drive amount data Δz, , and drives the photographing lens 12 in the direction of the in-focus point.At the same time, the encoder 17 monitors the amount of movement of the photographing lens 12 and drives it. When the photographing lens 12 moves by the absolute value of the quantity data ΔZo, the motor 9 is stopped and the photographing lens 12 reaches the focal point.

The central processing unit 16 sends drive amount data Δ to the drive control means 18.
Immediately after the charge is applied, charge accumulation for the next image sensor starts. Therefore, it is quite conceivable that the photographic lens 12 may be moving even during the charge accumulation time.

Next, a program flowchart of the central processing type 2t16 will be explained.

As shown in FIG. 2, when the process starts in step S1, the charge accumulation time T of the image sensor 15, which initializes various sequences in step S2, is also set to an initial value.

In step S3, charge accumulation in the image sensor 15 is started.

In step S4, when the charge accumulation time T reaches 1/2, the function f(d) is read from the function information generating means 21. Further, pulse counting from the encoder 17 is started, and detection of the moving amount Z of the photographing lens 12 is started.

In step S5, when the charge accumulation time from step S3 reaches T, charge accumulation in the image sensor 15 is terminated.

In step S6, data from the image sensor 15 is read, and in step S7, a predetermined focus detection calculation is performed on the read data to obtain defocus d.

Next, in step S8, the reading of the lens movement amount z1 from step S4 is finished, and the lens drive amount ΔZ·'(d)−Z is determined according to equation 6).

The data of the lens drive amount Δ2 obtained in step S9 is sent to the drive control means 18, and the sign of Δ2 is
The display contents of the display means 22 are updated based on the absolute value.

In step SIO, the next charge accumulation time T of the image sensor 15 is determined.

For example, the maximum value of the data obtained from the image sensor 15 is ■■ax, the target value is ip + the current charge accumulation time T
. If the charge accumulation time of the 9th time is Tn, then T11. l is found.

Tn+1-7nx (lp/Imax)
-(7) Next, the process returns to step S3, and one automatic focus adjustment sequence is completed. By repeating such an operation, the photographing lens 12 is automatically guided to the in-focus point.

Note that in the above sequence, step 38. S9゜S
The time required for IO is almost negligible and can be ignored.

Next, an operation time chart of the automatic focus adjustment device of the camera will be explained.

In FIG. 3, the vertical axis represents the position 2 of the photographing lens 12, and the horizontal axis represents the time E.

Time T3. It is assumed that the photographing lens 12 is being driven toward the in-focus point at the lens position 21z1.

At time T1, charge accumulation in the image sensor 15 is started.

At time T, which is the midpoint of the charge accumulation time T, the central processing type 2116 generates the function ΔZ =
At the same time as reading f, 1(d), the encoder 17 starts pulse counting and starts monitoring the lens movement amount z5. Therefore, the lens movement eiz represents the amount of lens relative movement of the photographing lens 12 from the digit 2J Z l at time T1.

Next, at time T4, which is the charge accumulation time T after time T3.
At , the charge accumulation of the image sensor 15 is completed, and the defocus d is determined by performing focus detection calculation processing on the data from the image sensor 15 over the processing time from time T4 to time T2.

At time T2, the lens movement r by the encoder 17
After finishing the monitoring of
The lens driving amount ΔZ −f(d
)−Z, is obtained. The lens movement m lk Z I is the relative movement between the lens positions 2txt and 21* amount z, -zauzl.

The lens movement *iΔ2 determined at time T is sent to the drive control means 18, and from this point on, a new drive control based on the lens movement amount Δ2 is started, and at the same time at time T.
2, the next charge accumulation of the image sensor 15 starts.

With the above configuration and the 911 operation, the lens movement amount Δ2 from the lens position zt to the in-focus point at time T2 can be accurately determined from the defocus d determined at time T2.

That is, the defocus d found at time T2 is the defocus at the midpoint time TI of the charge accumulation time T+lens position zI, and therefore at the lens position piz+. Using the defocus lens shift*i function f(d), the lens drive is first converted from the lens position z1 to the in-focus point, and then the lens has already moved between time T1 and time To, = z. , -z, so by correcting it by that amount, the lens position a
Accurate lens movement amount ΔZ from lz to the focal point =
f(d) Zs can be found.

In the first embodiment, the function f(d) is read at the midpoint of the charge accumulation time and monitoring of the lens movement amount Z's is started, but if the subject is very bright and the charge accumulation time is extremely short, In this case, the charge accumulation time can be ignored with respect to the focus detection calculation processing time, so the function f(d) is read before or after the charge accumulation of the image sensor 15 is started or the lens movement ff1zs is started to be monitored. You may.

Furthermore, although the function f(d) was read from the function information generating means 21 at the midpoint of the charge accumulation time, only a control signal for fixing the output of the function information generating means 21 was generated at this point, and the charge accumulation The function f(d) may be configured to be read after completion.

In the first embodiment, the charge accumulation time of the image sensor 15 was controlled by the central processing unit 16. That is, the central processing unit 16 is the image sensor 1
The next charge accumulation time of the image sensor 15 is controlled so that the average value of the data or the maximum value of 4N becomes a predetermined value by reading out the data of No. 5.

As described above, since the charge accumulation time is controlled by a feedback system with a delay, responsiveness may deteriorate when the subject is dark or when the brightness of the light source is fluctuating.

5 to 7 show a second embodiment of the present invention.

In the configuration of the automatic focus adjustment mum of the camera according to the second embodiment, parts having the same functions as those according to the first embodiment will be described with the same reference numerals.

The difference between the first embodiment and the second embodiment is that a sensor control means 23 is newly added, and the other parts are completely the same, so the explanation will be omitted, and only the parts related to the sensor control means 23 will be explained.

The image sensor 15 and the sensor 1tll11 means 23 are connected, and the sensor control means 23 and the central processing type 21
I16 is connected.

The central processing unit 16 is configured to send an activation signal to the sensor control means 23 in order to start the accumulation of the image sensor 15.

The image sensor 15 is configured to be capable of non-destructively reading a monitor output corresponding to the amount of charge accumulated in each photoelectric conversion element or the sum of the amount of charge accumulated in all photoelectric conversion elements.

The sensor control means 23 is configured to start comparing whether or not the monitor output has reached a predetermined value at the same time as the start of charge accumulation.

Next, the monitor output comparison operation of the sensor control means 23 will be explained.

In FIG. 7, the vertical axis corresponds to the monitor output (charge amount), and the horizontal axis corresponds to the spatial arrangement of the photoelectric conversion elements. The waveform can be considered to correspond to the intensity distribution of the subject image.

FIG. 7(A) shows that the maximum output value wax of each photoelectric conversion element monitor is 1/2 of the predetermined value M, or the average value aV obtained by dividing the sum of the monitor outputs of all photoelectric conversion elements by the number of elements is the predetermined value. A
The waveform of the monitor output at the point when it reaches l/2 of
The waveform shown in FIG. 7(A) is shown in FIG. At this point, the sensor control means 23 sends a timing signal indicating that the middle point of the accumulation time has been reached to the central processing type gl16.
Send to.

When the central processing type 2116 receives this timing signal, it reads the function f(d) from the function information generating means 21, simultaneously starts counting pulses from the encoder 17, and starts monitoring the lens movement amount z8.

FIG. 7(B) shows the monitor output at the time when the maximum value ■ax reaches a predetermined value M or the average value aV reaches a predetermined value A over time from the above-mentioned point in time (see FIG. 7(A)). Waveform (hereinafter referred to as “
7(B). At this point, the sensor control means 23 terminates the charge Jl of the image sensor 15 and at the same time sends a timing signal to the central processing unit 16 to notify that the charge accumulation has been terminated.

The central processing unit 16 receives this timing signal and starts reading data from the image sensor 15. The operation after reading the image sensor data is the same as that according to the first embodiment.

If T is the time from the start of charge accumulation until the waveform shown in FIG. 7(B) is obtained, that is, the charge accumulation time, then the time shown in FIG.
The time it takes to obtain the waveform A) is ``/2.''

Next, a program flowchart of the central processing bag 2116 will be explained.

In FIG. 6, when starting in step Sl, the sensor control means 23 is started in step S2, and the charge on the image sensor 15 is determined? Start 1 product.

In step S3, wait for a timing signal indicating the midpoint of the charge accumulation time to be input from the sensor control means 23,
When this timing signal is received, the function information generating means 2
Read the function f(d) from 1.

At the same time, pulse counting from the encoder 17 is started, and monitoring of the lens movement amount zs is started.

In step S4, a timing signal indicating the end of charge accumulation is waited for from the sensor control means 23, and when this signal is received, the process moves to step S5 and data from the image sensor 15 is read.

From step S6 to step S8, step S7
to step S9 (see FIG. 2), and will therefore be omitted.

When step S8 is completed, the process returns to step S2 to start the next sequence.

In the second embodiment, since the charge accumulation time of the image sensor 15 is controlled in real time by the sensor control means 23, the responsiveness of the automatic focusing device is improved, and defocusing is performed at the midpoint of the charge accumulation time. Since it is possible to read the function f(d) of the lens movement amount, unstable operation does not occur in lens driving.

In the first and second embodiments, the central processing bag 2116 reads the function "(d)" from the function information generating means 21 at the midpoint of the charge accumulation time of the image sensor 15. The timing of reading is not limited to the midpoint of the charge accumulation time.

Generally, when T is the charge accumulation time, the function f(d) may be read at a time Tdvk shown by equation (8) from the charge accumulation start time of the image sensor.

Td - α × T ... (8) However, 0≦α≦1 For example, without considering that the obtained defocus d is a defocus at a position that is equal to the lens position during the charge accumulation time, When considering the defocusing of the lens position as weighted with a larger weight given to the lens position closer to the focal point, the coefficient α in equation (8) can be taken as 112<α≦1.

Further, the coefficient α may be made a function of the charge accumulation time, or may be made variable according to the driving speed of the lens or a change in the lens driving speed.

FIG. 8 shows a third embodiment of the invention.

The automatic focus adjustment device for a camera according to the third embodiment is configured such that the sensor control means 23 does not generate a timing signal indicating the midpoint of the charge accumulation time, and only that point is
This is different from the second embodiment, and the other configurations are completely the same as the second embodiment. Further, only the operation of the central processing unit 16 according to the third embodiment is different from that according to the second embodiment, and only the different parts will be explained, and the explanation of other configurations and operations will be omitted.

A program flowchart of the central processing bag 2116 according to the third embodiment will be explained.

In FIG. 8, when the process starts at step St, the function r+(d) is read from the function information generating means 21 at step S2.

At the same time, the pulses from the encoder 17 are started to be counted, and the lens movement amount Zs is started to be read.

In addition, the sensor control means 23 is activated, and the image sensor 1
5 starts charge accumulation.

In step S3, waits for a timing signal for the end of charge accumulation from the sensor control means 23, and when this signal is received, the function rt(ct) at this point is read from the function information generation means 21. At the same time, monitoring of the lens movement itz by pulse counting the encoder 17 is finished, and the lens movement @) WkZ s during the charge accumulation time of the image sensor 15 is stored. At the same time, monitoring of lens movement IkZt from the point in time when charge accumulation ends is started.

In step S4, data from the image sensor 15 is received.

In step S5, the receiver performs a predetermined focus detection calculation on the image sensor data to obtain defocus d.

In step S6, the monitoring of the lens movement ff1za is finished, and the lens movement amount 2a from the time when charge accumulation ends to the time when the defocus d is determined is determined.

Next, the defocus d is converted into a lens movement amount ΔZ based on equation (9).

ΔZ = (rl(d)"fx(d))/2-(Zy"Z
g/2) ”” (9) The first term on the right side of equation (9) (
fl(d)eft(d))/2 is the function r+(d) at the start of charge accumulation and the function r at the end of charge accumulation.
*From (d), the function at the midpoint of the charge accumulation time is calculated by averaging.

The second term (Zt''Zs/2) on the right side of equation (9) is the amount of lens movement Z during the charge accumulation time, which is 18 times the amount of lens movement during the calculation time from the end of charge accumulation until the defocus d is found. This is the sum of the lens movement amount za, which corresponds to the lens movement amount from the midpoint of the charge accumulation time to the time when defocus d is determined.

Therefore, the lens movement amount Δ2 from the lens position at the time when the defocus d is determined to the in-focus point can be determined using equation (9).

In step S7, the determined lens movement amount Δ2 is sent to the drive control means 18, and the drive control means 18 starts drive control based on the received lens movement amount ΔZ. Also, based on the sign and absolute value of the lens movement amount Δ2, the display means 2
2 is updated.

Next, the process returns to step S2 again, and by repeating a loop of 0 or more in which charge accumulation control is performed for a new image sensor, the photographing lens 12 is guided to the in-focus point.

In the third embodiment, even if the sensor IT control means 23 (see FIG. 5) is configured such that it cannot output a timing signal at the midpoint of the charge accumulation time, it is possible to obtain an accurate lens movement amount Δ2. Has characteristics.

In the third embodiment, the charge accumulation time of the image sensor 15 was controlled by the sensor control means 23, but as in the first embodiment, the charge accumulation time of the image sensor 15 is controlled by the output data of the previous image sensor. Even if the central processing type 316 is controlled based on this, the same processing as in the third embodiment can be performed.

Further, in the third embodiment, the lens movement amount Δ2 was calculated using the equation (9), but the lens movement amount Δ2 can generally be calculated by introducing the coefficient β as shown in the equation (lO).

ΔZ ”(1-β) X fl(d)◆βX fx(d
)−(Zt” (1−β)Zs)・−(10) However, 0≦β≦1 For example, do not consider that the obtained defocus d is the defocus at the average position of the lens during the charge accumulation time. to 1
When considering defocusing at a weighted average lens position in which a larger weight is given to a lens position closer to the in-focus point, the coefficient β in equation (10) can be taken as 112<β≦1.

Further, the coefficient β may be a coefficient of charge accumulation time, or may be made variable according to the lens drive speed or changes in the lens drive speed.

9 to 11 show a fourth embodiment of the present invention.

In the first to third embodiments, the lens movement amount ΔZ was calculated from the defocus d based on the assumption that the photographing lens 12 was driven at a constant speed during the charge accumulation time of the image sensor 15. Therefore, if the photographing lens reaches the target lens position (focus point) and stops during the charge accumulation time, the above assumption is broken and there is a risk of malfunction in the first lens drive control.

The automatic focus adjustment device for a camera according to the fourth embodiment improves the problems associated with the first to third embodiments. Good lens drive control can be performed even if lens drive ends during the charge accumulation time.

As shown in FIG. 9, in the configuration of the fourth embodiment, the first
Components having the same configuration as those in the embodiments to the third embodiment will be described using the same reference numerals.

The differences between the camera autofocus j1 section device according to the fourth embodiment and those according to the first to third embodiments are as follows: The Il control means 18 generates a drive end timing signal to the central processing unit 116, and since the other parts are completely the same, the explanation will be omitted, and only the parts that are characteristic of the fourth embodiment will be explained. .

A program flowchart of the central processing type JIL16 according to the fourth embodiment will be explained.

In FIG. 1O, when the process starts at step S1, the function rt(d) at the lens position at the charge accumulation start point is read from the function information generating means 21 at step S2.

At the same time, pulse counting from the encoder 17 is started, and monitoring of the lens movement 111 z m is started. Also, a timer inside the central processing unit is activated and starts measuring the time T from the charge accumulation start point. Further, the drive end flag is set to 0, the sensor control means 23 is activated, and charge accumulation in the image sensor 15 is started.

Next, in step S3, it is tested whether the drive end flag has become 0, and if it is 0, the process advances to step S4.

In step S4, a test is made to see if a drive end timing signal is generated from the drive control means 18, and if not generated, the process proceeds to step S6.

In step S6, if the timing signal for ending accumulation is generated from the sensor control means 23 or if the test signal is not generated, the process returns to step S3 and the loop is repeated again.

For example, if we consider a case where a timing signal for ending driving is generated during the charge accumulation time, the above loop is repeated, and when the timing signal for ending driving is generated in step S4, the process moves to step S5.

In step S5, the time Ta from the time when charge accumulation is started to the time when the drive end timing signal is generated.
, and set the drive end graph to 1 in step S6.
Proceed to.

In step S6, if charge accumulation has not been completed, the process returns to step S3. Since the drive end graph is 1, the process returns to step S6.

Thereafter, the above-described loop is repeated until the charge accumulation is completed, at which point the loop is exited and the process proceeds to step S7.

In step S7, the function -ft(d) at the lens position at the end of charge accumulation is read by the function information generating means 21. At the same time, pulse counting from the encoder 17 is finished, and the lens is moved during the charge accumulation time! LLZI is memorized, pulse counting is started anew, and monitoring of lens movement 1zT from the end of charge accumulation is started.

Furthermore, the time measurement from the start of charge accumulation is finished, and the charge Jta time Tb is stored.

Next, in chip S8, it is tested whether the drive end flag is 0 or not. Since the drive is ended during the charge accumulation time, the drive end flag is set to l, so the process advances to step SlO.

At step 310, data from the image sensor 15 is read.

In step Stt, a predetermined focus detection calculation process is performed on the read image sensor data to obtain defocus d.

In step S12, pulse counting from the encoder 17 is finished, and the lens movement MZT from the time when charge accumulation ends to the time when defocus d is found is determined. In this case, the lens movement amount Zt is O since the lens driving is completed before the charge accumulation is completed.

In step S12, the defocus d, the function r+(d) ·, rt(d) and the lens movement amount Zs
, Zt and times Ta and Tb, the lens movement amount Δ2 is determined from the lens position at the time when the defocus d is determined to the in-focus point using equation (11).

△z-(t-y)rt(x)+yr*(x)-(zt
+(t-y)Zs)D In equation (11), the coefficient γ is the value that the average position of the lens during the charge accumulation time is within the range between the lens position at the start of charge accumulation and the lens position at the end of charge accumulation. This ratio was determined assuming that the lens is driven at a constant speed and that the drive is stopped quickly.

For example, if the lens is driven throughout the entire charge accumulation time, the coefficient γ becomes 172 (11
) formula coincides with the (lO) formula. Further, the coefficient γ may be further corrected in consideration of charge accumulation time, driving speed, etc.

In step S13, the display means 22 is updated based on Z to the lens movement lh amount determined by equation (11), and the lens movement amount ΔZ is sent to the drive control means 18 to perform new lens drive control. and step S
Return to step 3 and start the next sequence.

The above loop is repeated until the lens is guided to the focal point.

The above explanation has been made on the assumption that the lens drive ends during the charge accumulation time, but if the lens drive does not end during the charge accumulation time, step S5 is not executed, and instead, a drive end flag is set in step S8. Since is 0, step S9 is executed and the time Ta is made equal to the charge accumulation time Tb. Therefore, in equation (11), the coefficient γ is '/2
Therefore, equation (11) is the same as equation (10).

Next, an operation time chart of the automatic focus adjustment device according to the fourth embodiment will be explained.

As shown in FIG. 11, the vertical axis represents lens position Hz, and the horizontal axis represents time. It is assumed that the lens position is at z3 and the lens is being driven at charge J product start time T3. At time 0 T3, the function r+(d) is fixedly stored, and at the same time, monitoring of the lens movement fiLz is started, and measurement of 1 hour T is performed. Start.

When lens driving ends at time T, one hour Ta is stored.

When charge accumulation ends at time T, function f2(d
) is fixedly stored, and at the same time, the monitoring of the lens movement amount Zs is ended, and a new monitoring of the lens movement amount z1 is started. Also, the measurement of the time T is finished and the charge accumulation time Tb is stored.

At time T2, defocus d is determined by equation (11), and new drive control is started.

In the fourth embodiment, even if lens driving ends during the charge accumulation time, lens driving control can be performed without malfunction.

In the third and fourth embodiments, the function f(d)
is read at the start and end points of charge accumulation, and the relationship between the defocus d and the lens movement amount Δ2 at the average lens position during the charge accumulation time is determined by interpolation. If the central processing unit 2116 has high functionality and can frequently read and store the function f(d) from the function information generating means 21 during the charge accumulation time, the following configuration may be used.

The central processing unit 16 reads out and stores the function f(d) at regular intervals during the charge accumulation time, and simultaneously stores the lens movement amount 2 from the start of charge accumulation to the time when the function f(d) is read out. .

It is assumed that the function -f(d) and the lens movement amount 2 can be stored N times during the charge accumulation time. If the n-th function is ゎ(d) and the n-th lens movement amount is 2°, then (1
The lens movement amount Δ2 from the lens position at the time when the defocus d is determined to the in-focus point can also be determined as in 2).

According to equation (12), even if the lens drive speed fluctuates during the charge accumulation time, by setting the readout period of the function "(d) shorter than the fluctuation time, the lens movement rate will be △
Z can be determined accurately.

In the first to fourth embodiments, the description has been given on the assumption that the function f(d) that converts the defocus d into the lens movement amount Δ2 differs depending on the lens position.

Information that differs depending on the position of the photographic lens includes optical data such as the F number and various aberrations.

Normally, correction is added to the defocus d or the lens movement amount Δ2 determined according to these optical data.

For example, if the spectral characteristics of the photographic optical system and the spectral characteristics of the focus detection optical system are different, it is necessary to offset the determined defocus d by an amount multiplied by a predetermined coefficient for the amount of chromatic aberration of the photographic optical system. .

Therefore, if the above optical data differs depending on the position of the photographing lens, the obtained defocus d or lens shift! ! I
Is it necessary to make a correction to the amount Δ2 based on optical data at the average position of the lens during the charge accumulation time?

FIG. 12 shows a fifth embodiment of the invention.

The camera autofocus igtgB device according to the fifth embodiment takes the above matters into consideration and applies the optical data generating means 24 that outputs optical data according to the lens position to that according to the fourth embodiment.

The difference in the operation of the camera automatic focus adjustment device according to the fifth embodiment from that according to the fourth embodiment is that the central processing unit W116 according to the fourth embodiment generates the function ΔZ from the function information generating means 21.
The difference is that optical data 0 can be read at the same time when -f(d) is read, and the operations of other parts are exactly the same.

Function fl(d) at the start of charge accumulation a, optical data D
, the function rt(d) at the start of charge accumulation, and the optical data Dt, then the functions r, (d) and fffi(d) can be expressed as /Z by the optical data D, , Do as shown in Equation (13). Just correct it.

△
(d+g(Dt))+h(at)−(1
3) In equation (13), the functions g(D) and h(o) are functions for determining the correction amount from the optical data D.

In the fifth example, the lens movement amount ΔZ is calculated by adding the function r+(d) in equation (11) to r l(d
+g(D I )) +11 (o l) and by substituting L (d0g(Dz))◆h(Dt) into the function rt(d).

In the fifth embodiment, the optical data generating means 24 is
Although the embodiment is shown as being applied to the embodiment, it may also be applied to the first to third embodiments.

In that case, it is assumed that the optical data D is read at the same time as the function f(d) is read.

For example, when applied to the first embodiment, equation (6) is changed to (
An accurate lens movement amount Δ2 can be obtained by transforming the equation as shown in equation 15).

Δ Z −f, (d+g(D,))+h(D,)
-(14) In the fifth embodiment, even when the lens is driven during the charge accumulation time, it is possible to not only accurately convert the function f(d) of the defocus d and the lens moving field Δ2, but also to correct various aberrations. It also has the feature that it can be performed accurately.

"Effect of the invention" Automatic focus of the camera according to the invention:! According to the R-node device,
Even when the photographic lens is driven during the charge accumulation time of the image sensor, the accurate position of the focal point can be detected, so the photographic lens can be smoothly driven to the focal point without unstable operation such as hunting. can do.

[Brief explanation of drawings]

1 to 4 show a first embodiment of the present invention, in which FIG. 1 is a configuration diagram of an automatic focus adjustment device of a camera, FIG. 2 is a program flow chart of the central processing unit, and FIG. Operation time chart, Figure 4 is an explanatory diagram of the relationship between defocus at the lens position and lens movement amount, Figures 5-
FIG. 7 shows a second embodiment of the present invention, and FIG. 5 shows the camera's 0 almost focus J11t! The configuration diagram of the i device, FIG. 6 is a program flowchart of the central processing unit, FIGS. 7 (^) and (B) are diagrams explaining the operation of the sensor control means, and FIG. Program flowchart of the central processing unit of the automatic focus adjustment device of the camera, FIG.
Fig. 11 shows a fourth embodiment of the present invention, Fig. 9 is a configuration diagram of the autofocus J1 device of the camera, Fig. 1O is a program flow chart of the central processing unit, and Fig. 11 is an operation time chart. , FIG. 12 is a configuration diagram of an automatic focus adjustment device for a camera according to a fifth embodiment of the present invention. i o--Camera body l 2--Photographing lens 13--Main mirror 14--Sub mirror 15--Image sensor 16--Central processing unit 17--Encoder 1 B--Drive control Means 19...Motor 20 for driving the photographing lens...Lens position detection means 21-...Function information generation means 22-...Display means 2
3...Sensor control means Whistle 1 figure storage fi〆Hji"h t % 61su charge 1 watch the same 1 gu" 1 b chant i3 electric charge figure 7 figure q figure Len Z Device Z Fig. 11 Fig. 12

Claims (1)

[Scope of Claims] An automatic focus adjustment device for a camera that starts a focusing operation by moving a photographing lens during a focus detection operation, comprising: a charge accumulation type image sensor that receives a light beam passing through a photographing lens of the camera; Defocus detection means receives an output from an image sensor and detects defocus of an imaging plane by the photographing lens with respect to a planned imaging plane; Lens position detection means detects the position of the photographic lens; Lens position detection means function information generating means for generating functional information indicating a functional relationship between defocus and the amount of movement of the photographing lens according to the output of the image sensor; and both the start and end points of charge accumulation in the image sensor; Alternatively, storage means reads and stores the function information generated by the function information generation means at one of the charge accumulation start time and a predetermined time during the charge accumulation time; and the defocus detection. drive calculation means for determining the drive direction and drive amount of the photographing lens based on the defocus detected by the means and the function information stored in the storage means; An automatic focus adjustment device for a camera, comprising: drive control means for controlling the drive of the camera.