JPS59224806A - Focusing controller - Google Patents

Abstract

PURPOSE:To reduce the difference in lens focusing response speed between a long- and a short-focus side by obtaining focal length information, iris information, etc., on an image pickup device from a sensor output, and controlling the extent of lens driving in focusing according to the pieces of information. CONSTITUTION:When the correlation in a correlator 9 is completed, a signal dx indicating the extent of focusing on a subject is sent from the correlator 9 and stored in a memory 13-1. At this time, a focus lens system for a lens 1 is driven according to the extent of focusing. Then, the correlation output dx after the focus lens system is driven by some extent is stored in the memory 13-1 as well as before. At this time, the last stored contents of the memory 13-1 are transferred to a memory 13-2 through a gate 13-10. The absolute value of the difference between the contents of those two memories 13-1 and 13-2 is calculated by a subtracter 13-3, and when the value is smaller than the set value ''E'' of a comparator 13-6, a counter 13-7 counts up by one in response to a clock pulse from an oscillator 13-11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focusing control device, that is, a device that automatically controls focusing of an imaging optical system without depending on the optical system.

FIG. 1 shows an example of an automatic focusing device based on the prior art. A light ray 2A id from the subject swirls through one end of the lens 1, passes through a small reflecting mirror 4C, and forms an image on one end 3A of a one-dimensional solid-state image sensor (hereinafter referred to as sensor) 3 made of a CCD or the like. This image will be called the A image. Here, the sensor is an electric element that converts a spatial image into an electrical video signal. Ray 2BH passing through the other end 1B of lens 1.

The image is formed on the other end 3B of the sensor 3 via the small reflecting mirror 4D.

This image will be called the B image.

The sensor 3 is arranged at a position optically equivalent to the imaging surface 12. When the lens 1 is extended forward from the correct focusing position, the K ye path changes as shown by the dotted line in FIG. is the direction in which the two images approach each other when the lens 1 is pushed forward, and is the direction in which the two images move away from each other when the lens 1 is pulled back.

Therefore, the distance d between the two images (image A and image B) is detected.

By controlling the lens position so that the interval matches the value at the time of correct focusing, the lens 1 can be maintained at the correct focusing position. When the sensor 3 is driven by the drive circuit 7, the optical images (A image, B image) of the sensor 31- are converted into a time-series electric video signal. The generated video signal is converted by a binarizer 51 and a distributor 6 into two binarized video signals. This is obtained from the image A, and is called the binary video signal A.The other one is obtained from the B image, which is also focused on 3B, and is called the binary video signal B. Both signal lines are called 8A.
and 8B, and then manually inputted to the correlator 9.

A signal dX related to the distance d between the H, A and B images is obtained from the correlator 9. This signal is input to the lens control device 10. The lens control device 10H controls the lens drive unit 11 so that the signal of the distance between the two images (l=−) matches the value at the time of correct focusing. The structure of the correlator 9 is described in detail in Japanese Patent Application No. 133656/1988 entitled "Automatic Focusing Device". Also, JP-A-56-101111 and JP-A-57-. A similar technique is also described in Publication No. 19884, so a detailed explanation of the 11 works will be omitted.

Next, the lens control device 10 will be explained. The one shown in FIG. 2 is an example of a lens control device 10 according to the prior art. The lens control device 10 includes an arithmetic unit 10A that calculates the lens driving direction and a driving finger based on the output from the correlator 9, and a motor drive circuit 10B that drives the motor of the lens driving unit 11 based on the calculation result. The motor drive circuit JOB can be easily constructed using well-known conventional techniques.

The explanation will be omitted here, and the arithmetic unit +OA will be explained.

Each time the correlator 9 completes detection, it sends a detection completion pulse to the up/down counter 10-N. Output dXO of correlator 9
-1 is supplied to the set terminal S of the up/down counter 10-M. The comparator 10-9 outputs the output dX from the correlator 9 and the preset reference value "F" at the time of focusing.
Compare and judge whether it is "larger - 1,""smaller," or "equal." QSC] 0-H is a low frequency oscillator, and ant game
)] up/down counter 10-] through 0-12
'4 Supply F clock pulse.

3- Up/down counter 10-14[, up/down terminal U/D [Logic level °']" is input, the amplifier counts; when the logic level "0°" is input, the clock input terminal counts down. C[This is performed in synchronization with the applied clock pulse. Also, when the pulse input terminal PK logic level "]" is input manually from the correlator 9.

Set the states of counters 0-14 to the contents of the binary signal applied to terminal S. Maru-IJ Kusu 10-15
When the up/down counter 10-1.4 reaches the preset value °'F''' (corresponding to the value of dx at the time of focus).

It outputs the logic level °゛0°°. AND gate 10-12 is matrix 10-15 and 08CIO-
11 and calculates the AND of the outputs of up/down counter 10.
-14 reaches the set value "F°', inputting the clock pulse to terminal C is prohibited. Inverter 10-17
inverts the outputs of matrices 10-15. Also, IQ-16 is the output (logic level '°1°°
) and the signals from matrices 10-15. Inverter 10-18, Antogame)
10-19-4- is the output of or game 1-10-16 and the comparator 10-
9, the logical product of the outputs of the judgment signals 1 "large" and "small" is taken.

Next, the operation will be explained. Detection output content of correlator 9 d
If X is smaller than the set value F (the value of dX at the time of focus), the judgment signal of the comparator 10-9 is connected to the terminal U/D of the up/down counter]0-14, and the logic level is output from the output terminal of the comparator 10-9 "l" is output and the up/down counter 1.
0-14 [Goes into up count state. At the same time, the value of dX is set from the terminal S of the up/down counter 10-14 by the detection completion pulse.

Then, O outputs a clock pulse with a frequency f set as described later according to the moving speed of the main lens 1 (Fig.
By 8C10-11, the output power F of counter 10-]4 is counted up by the value of 1 (Lx-Fl)
'[Time to reach, comparator 1O-9)ll
The motor drive circuit +OB operates and drives the main lens 1 according to the J constant signal JJ. and counter 10-14
When the output of matrix 10-15 becomes F, the output of matrix 10-15 becomes logic level ゛°0''.
Through 12, the clock pulse input to terminal C increases to 11, and the output of inverter 10-17 becomes logic level ``1'', and OR game 1-10-16
A logic level "1" is output through the inverter 1t)-18, ant game 1, 10 to 19, and the comparator O-9 determines whether the judgment signal is "small" or the logic level is "0".
“Next.”

This generates an instruction signal to the motor drive circuit 10B to stop driving the lens, and the main lens 1 stops.

Here, the amount of lens movement is expressed by lens movement speed (constant) x lens driving time (ldX-FIx]/f). Therefore, by setting the clock frequency f to an appropriate frequency value in consideration of the lens movement speed,
Adjust the amount of lens movement.

Next, when the output contents d and
Logic level "0" is input to terminal U/D of O-1/I.

The counter TO-1,1 becomes a down count of 4 dogs.

Then, the value of dx at this time is set in the counter 10-14K. Then, complete the prescribed down count.

7- The output of the counter 10-14 becomes the set value F, and the output of the matrix 1015 becomes the logic level ゛0'', so the clock pulse that was being input through the anti-game 1-10-12 stops, and at the same time, the inverter ]0
-17 output becomes logic level "1゛°.

Logic level ゛°1 through or game 1-]0-]6
" is output, which becomes a lens drive stop instruction signal to the motor drive circuit 10B, and the main lens 1 is stopped.

Jr., the prior art #i mentioned above has the following drawbacks. 4-
In the prior art described above, the amount of drive W of the lens 10 to the in-focus position is proportional to the deviation x-dx-F of the distance d between the two images on the portions 3A and 3B of the sensor 3 from a certain reference value. . That is, by the constant of proportionality ay.

W-αX ・・・・・・・・・・・・・・・・・・
(1).

By the way, generally speaking, when the subject is at infinity, when the subject approaches the front focal point of the lens to a distance of L, the image point will be at a distance of 1ll'lI given by the following equation (Euton's equation). Move by Z.

z-J2/■.

8- Here, fI-1l is the focal distance of the lens. As is clear from this equation, the smaller the focal length f of the lens, the less the image point moves when the subject moves a certain distance W. If the movement of the image point is small, the change x in the distance d between the two images of the sensor 3[- will also be small, and therefore the drive amount W given by equation (1) will also be small.

This causes the following problems. That is, when a conventional autofocus number setting is applied to a variable focal length lens such as a zoom lens, the amount of lens drive changes as the focal length of the lens changes.

The lens is driven at high speed on the long focal length side, and at low speed on the short focal length side. Therefore, the problem arises that either the operation becomes unstable on the high speed side or the response speed becomes slow on the low speed side. In zoom lenses, focusing is usually accomplished by moving the focus lens. Therefore, the amount of movement of the image point when the focus lens is driven with a constant kick is:

Long focal length ■1 Larger on the far side, smaller on the short focal length side.

The present invention is intended to solve the above-mentioned problems. That is, -9- of the imaging device from the sensor output.

Information corresponding to focal length information, iris information, etc. is obtained, and the amount of lens drive during focusing is controlled according to this information. For example, when a conventional TTL automatic focusing device is applied to a variable focal length lens such as a zoom lens, information corresponding to the focal length is obtained from the sensor output, and this information is used to adjust the lens drive amount. An object of the present invention is to reduce the difference in lens focusing response speed between the long focal length side and the short focal length side by adjusting .

FIG. 3 shows a configuration diagram of an embodiment of the present invention. 13 is a focal length detector, which detects the focal length of the variable magnification lens system (not shown), that is, the position of the zoom ring, based on a signal from the correlator 9 that corresponds to the distance between the two images on the sensor 3. is calculated and the information is sent to the lens control device 10. Lens control system @10
controls the lens drive amount based on this information.

That is, the value of the proportionality constant a in the above-mentioned equation ( ) is changed depending on the position of the zoom ring.

The rest of the configuration and operation of FIG. 3 are the same as those of the prior art shown in FIG. 1, so their explanation will be omitted.

10- FIG. 4 shows a specific configuration diagram of an embodiment of the focal length detector 13 of the present invention. Once the correlation by the correlator 9 of FIG. Diagram memo lJ] 3-+[Manualized. Also, at this time, the contents stored in memo 1J13-1 are passed through game 1-13-10 and stored in memo IJ13-1.
Moved to 2. Game) 1.3-10 is the oscillator 13-1
1 opens and closes at a constant cycle, so the contents of the memory 13-2 are not updated at a cycle faster than the oscillation frequency of the 1 oscillator 13-11. The output signal X of the memo January 3-1 and the output signal Y of the memo IJ] 3-2 are input to the subtracter 13-3. Subtractor 13-3 U, output C=lX-Yl representing the absolute value of the difference between the two input signals X and Y;

It generates an output when X>Y.

Output C from subtractor 13-3 is input to comparator 13-6. The comparator 13-6 compares the preset reference value E with the input signal C, and when C<E, the output terminal becomes high level, and the clock pulse of the oscillator 13-11 is at the gate 13. -12 to the binary counter 13-7.

On the other hand, the output of the subtracter 13-3 is input to the memo 1JI3-4. At the same time, the contents previously stored in memo January 3-4 are moved to memory 3-5. Memory 13-4. The outputs of Memo January 3-5 become the inputs of exclusive OR (EX-OR) game 1.3-8, respectively. The output of the EX-OR gate 13-8 becomes the input power of the counter 13-7 via one of the logical sum (OR) gates 13-9. Further, a lens drive stop signal in the lens control device 10, that is, a signal indicating that the subject is in focus, is used to reset the counter 13-7 via the other input of the OR game 13-9.

The operation will be explained.

When the correlation in the correlator 9 is completed, the signal dX indicating the degree of focus on the subject from the correlator 9 is sent to the memo January 3
−1 [stored. Also, at this time, the focus lens system of the lens 1 is driven depending on the degree of focus.

Next, the correlation output dX after the focus lens system is driven by a certain amount is stored in the memo January 3-1 as in the previous case. At this time, the contents stored on Nimemo 11-January 3-1 are K1-13-1.
0 to the memory 13-2. The subtracter 13 calculates the absolute value of the difference between the contents of these two memories 13-1 and 13-2.
-3, and its value is the set value “E” of the comparator 13-6.
``When the value is smaller than ``, the counter 13-7 counts up by one by the clock pulse of the one-shot four-axis unit 13-11.

When the focus lens system is moved by a certain distance.

When the corresponding movement of the image point is small (subtractor 13
-3 output IX-Y1 is small), the counter 13-
7 is counting. Counter 13-7 has a set number 1. For example, when counting 10, counter 13-7
A signal is output from 7, and it can be seen that the focal length of the variable magnification lens system of lens 1 is in a small state. In addition, even when the focus condition approaches the in-focus state, the focus distance remains constant.
The movement of the image point relative to the movement of the lens system is reduced. In order to distinguish between this state and a state where the movement of the image point is small because the focal length is small, a counter 13 is provided.

In other words, when the image point continues to move for a long time (10 clock pulses in the example), it determines that the focal length is small and sends a signal to increase the amount of lens drive. From the counter 13-7 to the lens control device 10
It outputs to . On the other hand, if the amount of movement of the image is small because it is close to the in-focus state, the amount of lens movement up to the first in-focus position is also small and the in-focus state is reached in a short time. In such a case, there is no need to increase the amount of lens drive. At this time, a signal indicating the 1-in-focus state is input to the cent terminal of the counter 13-7 via the OR gate 13-9, as will be described later.

the result.

Counter 3-7 is set and no signal for increasing the drive amount is output from counter 13-7.

As a result of the above sequence, the lens drive amount is increased by the lens control device 10, and when the lens 1 reaches the in-focus state, the lens 1 is stopped by the control according to the prior art described above, and at the same time, the counter 13-7 is set. .

Furthermore, because the amount of lens drive has been increased, the lens 1 may pass through the focal point without stopping.

In this case, the D output from the subtracter 13-3 shows a value opposite to that before passing through the focused point. If the D output before passing through the in-focus point is at logic level ``1'', it will be 'o'' after passing through the in-focus point, and if the D output before passing through the in-focus point is at logic level ``0'', after passing through the in-focus point it will be 'o'. It becomes 1°.

Immediately after passing the in-focus point, the value of D immediately after passing the in-focus point is stored in memory edict-4, and the value of D in the previous state, that is, 9, is stored in the memo January 3-5. The previous value of D is stored. As a result, EX-OR Age-13-8
The output of is at a logic level of 0.1° and resets the counter 13-7 via the OR gate 13-9.

Therefore, once lens 1 passes through the focal point.

The amount of lens drive becomes small, and it is possible to reach a focused state without causing hunting.

The output of the counter 13-7 in the focal length detector 13 is:

The signal is sent to the lens control device 10 to control the amount of lens drive. A specific example thereof is shown in FIG. In this embodiment, a case will be described in which the output from the focal length detector 13 is used to control the amount of current supplied from the power source to the lens drive motor.

Connection brush emitter of transistor Tr2 and emitter of transistor Tr3, base of transistor Tr2 and base of transistor Tr3, emitter of transistor Tr4 and emitter of transistor Tr5, transistor Tr
4 and the base of transistor Tr5, the collector of transistor Tr2 and the collector of transistor Tr4,
The collector of the transistor Tr3 and the collector of the transistor Tr5 are connected.

Further, the collectors of the transistor Tr2 and the transistor Tr4 are connected to the power supply 10-1. transistor T
The collectors of r3 and transistor Tr5 are grounded via a resistor R, and are also connected to the collector of transistor Trl. The emitter of the transistor Trl is grounded, and the output of the focal length detector 13 is input to the base. The output from the motor drive amount calculator 10A as explained in FIG. 3 is input to the bases of the transistors Tr2 and Tr3 and the bases of the transistors Tr4 and Tr5.

This output is "1" when the lens is extended, and "1" when the lens is retracted.
and 0°" terminal outputs are reversed.

Also, when one focus is on, both outputs are I'' or both are 15
− becomes °′0″′.

In such a configuration, when the signal from the focal length detector 13 is 000, the transistor Tr If is cut off, and the motor driving current flows through the resistor R. However, the signal from the focal length detector 13 is '1'.

This is because the transistor Trl is in a conductive state when .

The motor drive current is passed through the transistor Tr without passing through the resistor R.
flows to ground via l. Therefore, when the focal length detector 13 outputs a signal of 1°.

That is, when a signal indicating that the amount of image movement is small because the focal length is small is output, the motor drive current increases and the amount of drive of the lens drive section 11 increases.

Note that the transistor Tr2. Tr3, Tr4,
Since the circuit operation of Tr5 is a general well-known circuit, its explanation will be omitted.

Further, since the motor drive amount calculator 10A is the same as that of the prior art, a description thereof will be omitted.

As described above, when the focal length f is short, the amount of change in x (-dX-F) in equation (1) becomes small as described above. However, in the present invention, the current for driving the motor 16 increases as described above, that is, the value of a in equation (1) increases, and the value of the lens drive amount W, which is the product of a and It will be bigger than if it were due to technology. Conversely, when the focal length f is long, the amount of change in x (= dx - F) in equation (1) above increases, but the motor drive current decreases (1).
The value of a in the equation becomes smaller. As a result, the value of the lens drive amount W becomes smaller than in the case of the prior art.

That is, according to the present invention, the width of change in the lens driving amount W due to a change in the focal length 81 is smaller than in the case of the prior art.

In the above embodiment, as a means for determining the in-focus state on the imaging plane of the imaging lens, a means for detecting the separation distance of two lines using a correlator was used. In addition to this method, a contrast method is also known as a method for determining the in-focus state.

In the contrast method.

Image sensors are placed optically in front and behind the correct focal plane, and the sharpness (contrast) of the image at these two positions is compared, and the lens position is controlled so that the two are equal. In this method.

Contrast of output video signals of two sensors) KA and KB
The difference KA -KB is 1dX-Fl in the above example
corresponds to Therefore, the present invention can also be applied to contrast methods.

To simplify this operation, a case where the subject is a point light source will be described. The contrast for general objects depends on the diameter of the circle of confusion of the image produced by a single point light source.

That is, as the diameter of the circle of confusion increases, the contrast decreases.

When a point light source object is imaged, if the distance Z from the image side focal point to the image point is constant, then the focal length of the lens is f.

If the diameter of the exit pupil (iris) is D, the diameter of the circle of confusion of the image is proportional to D/f.

Namely.

(diameter of the circle of confusion of the image)” (M)・z= (D/f)−(f'
A) = (D-f)/L. (The length L is the distance from the focal point on the point light source side to the point light source.)

In other words, the inner diameter of image confusion depends on the diameter of the exit pupil and the focal length of the lens. Therefore, in an automatic focusing device using the contrast method, when the focal length is constant, Klri, and the diameter of the exit pupil changes, a change occurs that corresponds to the change in the driving amount due to the change in the focal length in the above embodiment. When the diameter of the exit pupil is large, the diameter of the ζh random circle of the image becomes large for a unit distance movement of the lens, and as a result, the lens is driven at high speed. When the diameter of the exit pupil is small, the diameter of the circle of confusion of the image becomes small with respect to the movement of the unit back of the lens, and the lens is driven at a low speed.

Even in such a case, if the two aspects of the present invention are used, changes in the amount of lens drive due to the size of the exit pupil can be reduced.

As explained above, according to the present invention, various information of the imaging device is obtained from the sensor output, and the lens driving amount is controlled based on this information.2 For example, a variable focal length lens can be used in a TTL automatic focusing device. Even if the lens drive amount changes due to a change in the focal length of the lens, the amount of change in the lens driving amount is reduced compared to the case with the prior art. As a result, even on the long focal length side, the lens operates stably without being driven at high speed. Furthermore, even on the short focal length side, the lens is not driven at low speed and the response time is not slow.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional automatic focusing device, FIG. 2 is a block diagram of a lens control device 10, and FIG. 3 is a block diagram showing an example of a focusing control device of the present invention. FIG. 4 is a block diagram showing an example of the focal length detector 13 of the present invention, and FIG. 5 is a block diagram showing an example of the lens control device of the present invention. 1: Imaging lens, 3: Image sensor, 5: Binarizer,
6° divider, 7: drive circuit, 9: correlator. 10: Lens control device, 11: Lens drive unit, 13: Focal length detector. Figure 1

Claims (1)

[Scope of Claims] An imaging lens, means for determining a focusing state on an imaging plane of the imaging lens, and means for controlling a focusing state on the imaging plane of the imaging lens based on the determination result. In a focusing control device consisting of: The focusing state determining means includes means for mutually comparing focusing states at different times with a time difference set in advance,
A focusing control device comprising means for controlling the driving amount of the imaging lens by the focusing state controlling means based on the output signal of the comparing means.