JP2001350081A - Automatic focus adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic focus adjusting device by which high-speed and highly accurate focusing is always attained. SOLUTION: This automatic focus adjusting device is provided with first focusing means 15-18 to conduct focusing by performing range-finding calculation based on the integral quantity of a subject image signal obtained by photodetecting sensors 204a and 204b, arranged off the optical axis of image pickup optical systems 10 and 11 and second focusing means 12-17 to perform the focusing by calculating a focus evaluation value based on the subject image signal, obtained by an imaging device 12 provided on the optical axis of the image pickup optical systems 10 and 11, and the first focusing means is a multi- point focusing means, and plural multi-point focusing areas are arranged in the direction of parallax between the first focusing means and the image pickup optical system. Since the plural multi-point focusing areas are arranged along the direction of the parallax between the first focusing means and the image pickup optical system, the closest selection based on the multi-point range-finding of the first focusing means is conducted, so that the parallax is corrected automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device for an image pickup device such as a digital camera.

[0002]

2. Description of the Related Art Conventionally, a hill-climbing method (contrast method) and an auto-correlation method (phase difference method) are well known and widely used as methods of an automatic focusing device in an image pickup apparatus such as a digital camera. Hereinafter, these two types of automatic focusing devices will be described.

FIG. 13 is a block diagram of an automatic focus adjusting device based on a hill-climbing method. In FIG. 13, a light image from a subject (hereinafter, a subject image) is formed on an image sensor 22 by an imaging optical system including a photographing lens 20 and an aperture 21, and a video signal is generated by an image sensor controller 23. It is input to the video signal processing means 24. Shooting lens 2
A focusing lens having a variable lens position is included in 0.

As a configuration of the video signal processing means 24, there is generally a configuration as shown in FIG. The video signal is
Only high-frequency components are extracted by passing through a high-pass filter (HPF) 30, and amplitude detection is performed by a detection circuit 31. Next, the signal is converted into a digital signal by the A / D converter 32, and only the signal in the focusing area set near the center of the captured image is extracted by the gate circuit 33. To obtain the focus evaluation value of the current field.

At this time, the gate circuit 33 is controlled by the gate control circuit 34 based on the signal from the sync separation circuit 35 so as to extract only the signal in the focusing area.

As described above, the integration circuit 36 always outputs
The focus evaluation value for each field is output and supplied to the CPU 25.

The CPU 25 supplies a control signal for driving a focusing lens, which is a focus adjusting optical system in the taking lens 20, to the drive means 26 based on the focus evaluation value, and changes the focusing lens position. The position detecting means 27 detects the focusing lens position,
By feeding back to the PU 25, the CPU 25 can control the focusing lens to focus.

FIG. 15 is a diagram showing an example of a focus evaluation value. Generally, the focus evaluation value decreases as the defocus amount increases, with the focal point being the maximum value. That is,
A mountain shape is made as shown in FIG.

Returning to FIG. 13, the CPU 25 drives the lens 20 by a predetermined amount in a predetermined direction from the hill-climbing start position in FIG. 15 while obtaining the focus evaluation value from the video signal processing means 24. At this time, the driving of the lens 20 and the control of the position are performed using the driving unit 26 and the position detecting unit 27. CPU25
Repeatedly drives the lens 20 and checks the focus evaluation value. The lens passes the lens position where the focus evaluation value becomes the maximum value, stores the maximum value and the lens position in the storage means, and reverses the driving direction of the lens 20 when the focus evaluation value decreases by a predetermined amount from the stored maximum value. I do. Finally CPU25
Drives the lens 20 to the lens position where the focus evaluation value becomes the maximum value and stops it. Here, storage means for storing the maximum value of the focus evaluation value and the lens position at that time is not shown, but it may be configured to be included in the CPU 25,
25.

The above is the description of the hill-climbing automatic focusing device. Many hill-climbing methods have already been patented and are well-known, so further detailed description will be omitted.

Next, a description will be given of an automatic focus adjusting apparatus based on the autocorrelation method. FIG. 16 is a block diagram of an automatic focusing apparatus using the autocorrelation method.

In FIG. 16, a subject image is taken by a photographing lens 5.
An image is formed on an imaging element 52 by an imaging optical system composed of 0 and an aperture 51, a video signal is generated by an imaging element control unit 23, and input to a video signal processing unit 54. The taking lens 50 includes a focusing lens which is a focus adjusting optical system whose lens position is variable. Aperture 5
1 is such that the aperture state is switched between the time of focus adjustment and the time of photographing by the drive means 56 based on a command from the CPU 55, and the switched aperture state is changed each time.
The position detecting means 57 is notified. The drive means 56 has a function of driving the position of the focusing lens in the photographing lens 50 in addition to the drive of switching the aperture 51. The position detecting means 57 also has a function of detecting the position of the focusing lens and feeding back to the CPU 55, in addition to detecting the state of the diaphragm 51.

As shown in FIG. 17, the video signal processing means 54 includes the HPF 30 and the detection circuit 3 from the configuration shown in FIG.
1 and the integration circuit 36 are excluded, and the function is to extract and output all or a part of the video signal imaged by the image sensor 52. In FIG.
The video signal is converted into a digital signal by the A / D converter 32, and only the signal in the focusing area set near the center of the captured image is extracted by the gate circuit 33. The gate circuit 33 is controlled by a gate control circuit 34 based on the signal from the sync separation circuit 35 so as to extract only the signal in the focusing area. That is,
The gate circuit 33 extracts only a signal in the focusing area set near the center of the imaging screen during the focus adjustment operation, and outputs the signal to the CPU 55.

At this time, the CPU 55 obtains a video signal while driving the diaphragm 51 using the driving means 56 and the position detecting means 57.

On the basis of the video signal from the video signal processing means 54, the CPU 55 performs an autocorrelation operation to detect the focus state of the image pickup optical system, and controls the image pickup optical system to focus.

The diaphragm 51 is insertable into and removable from the optical path of the image pickup optical system, and has a shape as shown in FIG.
It comprises a zone having an opening a having a large opening diameter and two zones having openings b and c having a small opening diameter. These three zones are configured to be inserted one by one into the luminous flux from the photographing lens 50 by the aperture switching drive motor in the drive means 56. The zone having the aperture a is used for imaging after focusing, and the zones having the apertures b and c are used in the time series during the auto-correlation type focusing.
And the aperture c are switched to form pupils at different positions of the imaging optical system. That is, two video signals are acquired by switching between the opening b and the opening c of the diaphragm 51, the CPU 55 performs autocorrelation calculation, detects the focus state of the imaging optical system, and attempts to focus. . FIG.
(A), (b), and (c) show the in-focus state, the front focus state, and the rear focus state, respectively.
The difference (phase difference) between the image formation positions of two video signals obtained in time series formed on the surface of the image sensor 52 while switching between the image signals c and c is obtained by an autocorrelation operation, and the imaging optical system is brought into a focused state. If there is or not, and if the camera is not in focus, the amount of focus shift and the direction of shift are estimated.

Since the autocorrelation operation is known, its description is omitted. The above is the description of the auto-focusing apparatus using the autocorrelation method. Since many auto-correlation methods have already been applied for patents, their detailed description is omitted.

Although the hill-climbing system and the auto-correlation system automatic focus adjustment device have been described as well-known prior arts, the following prior arts are also known.

For example, there is a combined automatic focusing apparatus described in Japanese Patent Application Laid-Open No. Hei 7-154668. The gist of the invention is to realize a high-precision and high-speed automatic focus adjusting device including two types of automatic focus adjusting means of a hill-climbing method and an auto-correlation method. Although the autocorrelation method described above and the autocorrelation method described in Japanese Patent Application Laid-Open No. 7-154668 have some differences in detail, they are substantially the same.

Japanese Patent Application Laid-Open No. Hei 7-154668 discloses a known infrared active method (a distance sensor (PSD) determines the incident angle of infrared light reflected from a subject by projecting infrared light from a camera. Focusing)
There is also described an automatic focus adjustment device in which is combined with a hill-climbing method.

[0021]

However, the above-mentioned prior art automatic focusing devices using the hill-climbing method, the automatic focusing devices using the autocorrelation method, and the combined automatic focusing devices have the following disadvantages. .

First, the automatic focus adjusting device of the hill-climbing method obtains a focus evaluation value for each field while driving the focusing lens, and performs a focusing operation. Therefore, it takes time to focus.

Next, in the auto-focusing apparatus using the auto-correlation method, the in-focus position can be obtained by calculation from the video signal of one field. Cannot be obtained by calculation. Therefore, after driving the lens once, the autocorrelation calculation is performed again for confirmation, and the lens position is set within a predetermined error from the in-focus position.

On the other hand, the compound automatic focusing apparatus described in Japanese Patent Application Laid-Open No. 7-154668 has the following problems.

The autocorrelation method has the following problems in addition to the above-mentioned disadvantages. That is, when the position of the focusing lens is significantly away from the focus position and only a very blurred video signal is obtained, the focus position cannot be obtained by calculation. In other words, even in the autocorrelation method which is set to high speed, scanning driving of the focusing lens is required depending on the case, and it cannot be said that high speed is always used. Therefore, there is a problem that the speed is not always high even for the composite type.

The hill-climbing method and the auto-correlation method both belong to the same passive method in terms of the broader concept, and have low luminance and low contrast (hereinafter referred to as low contrast).
Is not good at the subject (shooting scene).

As a countermeasure against low luminance and low contrast, a method using auxiliary light and pattern irradiation using auxiliary light are known, but the effect of the countermeasure is not complete.

Therefore, there is a subject which is not good at focusing in the composite type of the hill-climbing method and the auto-correlation method.

Further, the autocorrelation method requires a stop member that can be inserted into and removed from the optical path of the imaging optical system, but this is considered to be problematic. (In the description of Japanese Patent Application Laid-Open No. Hei 7-154668, there is a description that the device is suitable for downsizing even in the case of a composite device, but this is questionable.) That is, an imaging device such as a digital camera. The dominant factor that determines the size of is the imaging optical system. Including an insertable detachable diaphragm member in the imaging optical system should increase the size to some extent. In addition, the insertion of a removable member increases restrictions on the optical design, and the difficulty of the optical design is increased in a difficult direction.

As described above, the composite type automatic focusing apparatus cannot always be said to be high speed, there are cases where a subject that is not good at it can not be focused, and the optical design is not always suitable for miniaturization. There is a drawback that it does.

Finally, the combined type of the infrared active system and the hill-climbing system has the following disadvantages.

The infrared active method generally irradiates a circular spot-shaped infrared beam toward a subject, but it is a discrete beam irradiation due to physical reasons of the light emitting and receiving elements. Therefore, the beam may deviate from the subject,
In the case of deviation, the subject distance is set to infinity, and if focusing is performed thereafter by the hill-climbing method, the maximum value of the focus evaluation value cannot be found by the hill-climbing method. Or it takes time to focus. In the meantime, the composite type of the infrared active method and the hill-climbing method is disclosed in Japanese Patent Application Laid-Open No. Hei 7-154668, which hinders miniaturization because light-emitting and light-receiving means are required. Since the composite type of the autocorrelation method is not necessarily suitable for miniaturization, it can be said that the existence of the light projecting / receiving means is not necessarily a disadvantage of the composite type.

As described above, the conventional automatic focusing apparatus cannot always be said to be fast. In addition, there is a case where the subject is not good and there is no focus. Further, when one of the methods has an erroneous side distance, there is a problem that focusing is not performed or it takes time to focus.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an automatic focusing device which can always perform focusing at high speed and with high accuracy.

[0035]

According to the present invention, there is provided at least a pair of integral light receiving sensors for receiving a subject image,
A stationary light elimination circuit provided for each pixel of the integration type light receiving sensor, auxiliary light means for illuminating the object, and an object image signal from the integration type light receiving sensor,
Integrating means capable of switching an integration mode between an active mode and a passive mode by turning on / off the stationary light removing circuit; and controlling integration operation of the integration means.
An integration control means capable of performing control for selectively switching between an active mode and a passive mode, performing a distance measurement operation based on an integration amount of a subject image signal obtained by the integration means, and First focus adjusting means for adjusting the focus by driving the system, an image sensor for imaging a subject on the optical axis of the imaging optical system, and extracting a subject image signal from a predetermined area of the image sensor A focus evaluation means for calculating a focus evaluation value, and a second focus adjustment means for performing focus adjustment by detecting a maximum value of the focus evaluation value while driving the focus adjustment optical system. The first focus adjusting means is arranged outside the optical axis of the imaging optical system, and
A multi-point focus adjustment unit, wherein a plurality of multi-point focus adjustment regions are arranged along a parallax direction between the first focus adjustment unit and the imaging optical system.

In the present invention, the first focus adjusting means is arranged outside the optical axis of the image pickup optical system and is a multi-point focus adjusting means, and the plurality of multi-point focus adjusting areas are the first focus adjusting means. Since the means and the imaging optical system are arranged along the parallax direction, parallax correction is automatically performed by performing closest selection based on multipoint ranging of the first focus adjustment means. In other words, it is possible to eliminate the influence of parallax caused by the first focus adjustment unit disposed outside the optical axis of the imaging optical system.

[0037]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of an automatic focusing apparatus according to an embodiment of the present invention. In the present embodiment, the above-mentioned hill-climbing automatic focus adjustment (hereinafter also referred to as contrast AF) means and a hybrid type A described later are used.
A composite type automatic focusing apparatus using F means will be described. The hybrid AF means corresponds to the first focus adjusting means, and the hill-climbing AF means corresponds to the second focus adjusting means.

The hill-climbing AF in the apparatus shown in FIG.
The means (second focus adjusting means) includes a photographing lens 10 including a focusing lens, an aperture 11, and an image sensor 12
, Image sensor control means 13, video signal processing means 14
, A CPU 15 as a control unit, a focusing lens driving unit 16, and a focusing lens position detecting unit 17. The taking lens 10 and the aperture 11 constitute an imaging optical system. Shooting lens 10
A focusing lens having a variable lens position is included therein as a focusing optical system.

A subject image is formed on an image pickup device 12 by an image pickup optical system composed of a photographing lens 10 and an aperture 11.
A video signal is generated by the image sensor control means 13,
It is input to the video signal processing means 14.

The video signal processing means 14 has the same configuration as that shown in FIG. In the video signal processing means 14,
Only the signal in the focusing area set near the center of the captured image is extracted, the extracted video signal is integrated for each field, and the focus evaluation value of the current field is obtained. The obtained focus evaluation value for each field is stored in the CPU2.
5.

On the other hand, the hybrid AF means (first focus adjusting means) shown in FIG.
Hybrid type distance measuring means 18 and auxiliary light means 19
, A CPU 15 as a control unit, a focusing lens driving unit 16, and a focusing lens position detecting unit 17.

Here, the hybrid type distance measuring means 18
Will be described briefly. The hybrid system is a combination of the passive system and the active system, and the passive system is a known technology. The active method is slightly different from a known distance sensor (PSD) and an infrared active method using an infrared light emitter (IRED). Instead of the PSD, a passive line sensor (a line sensor is used as a light receiving sensor). Japanese Patent Application No. 9-318553 and Japanese Patent Application No. Hei 11-33
No. 4546), a new sensor having a stationary light removing circuit for removing the stationary light for each pixel is used, and the subject is illuminated by the auxiliary light means 19 while removing the stationary light. Then, a distance measurement operation is performed based on the integration amount of the image signal of the object illuminated by the auxiliary light to obtain the object distance. In the passive method, a distance measurement calculation is performed by disabling the stationary light removal function in the active method to obtain a subject distance. In other words, the hybrid method
The passive operation is performed when the stationary light removing function is disabled, and the active operation is performed when the stationary light removing function is enabled.

The hybrid system has an advantage that the active system and the passive system can be switched by setting the valid / invalid (on / off) of the steady light removing circuit, and the distance can be measured in an advantageous manner according to the situation of the subject. There is.

A hybrid type automatic focusing apparatus is disclosed in the specification of Japanese Patent Application No. 11-139682, and a stationary light removing circuit is disclosed in Japanese Patent Application No. 10-336.
No. 921. The details of the ranging device provided with the hybrid ranging device and the auxiliary light device described above will be described later.

The CPU 15 calculates the lens drive amount based on the result of distance measurement in the hybrid system, generates a control signal for driving the focusing lens, and supplies the control signal to the drive means 16, whereby the focusing lens position can be variably controlled. A control signal for driving the focusing lens is generated based on the focus evaluation value obtained by the other hill-climbing distance measurement, and the control signal is supplied to the driving unit 16.
It is possible to variably control the focusing lens position. The position detecting means 17 detects the focusing lens position and feeds it back to the CPU 15 so that the CPU 15 can control the focusing lens to focus.

Referring now to FIG. 2, the details of the distance measuring apparatus provided with the hybrid type distance measuring means and auxiliary light means described with reference to FIG. 1 will be described. FIG. 2 shows a hybrid type distance measuring device. This ranging device
Preliminary distance measurement (active operation) is performed by projecting light to the entire sensor field of view, and a main integration (passive operation) distance measurement area is set near the position where the maximum integral value is obtained in the pre-range measurement, for example, and correlation is performed. An arithmetic operation is performed, and a distance measurement result is obtained by selecting the closest distance.

In FIG. 2, at a predetermined position of the distance measuring device,
Light receiving lenses 201a and 201b for condensing the subject light and the reflected light from the subject due to the auxiliary light are provided.

Further, the light receiving lenses 201a, 201
A housing 202 is provided to secure and divide the optical path b, and to prevent unnecessary outside light from entering the optical path. For the above-mentioned purpose, the housing 202 is usually formed of a material having excellent light-shielding properties in a dark color such as black. The housing 20
As for 2, other than those formed of the above-mentioned materials, those having a slanted line inside the housing so as not to cause irregular reflection of light inside, and those subjected to embossing processing are used. Of course you can.

In the figure, reference numeral 203 denotes an autofocus integrated circuit (hereinafter, AFIC). Hereinafter, the AFI
The configuration of C203 will be described.

Inside the AFIC 203, there is provided an aggregate of light receiving elements 204a and 204b constituting at least a pair of integral light receiving sensors for receiving light collected by the light receiving lenses 201a and 201b and performing photoelectric conversion. ing. Further, a photocurrent integration unit 205 is provided as integration means for integrating the photocurrent photoelectrically converted by the light receiving elements 204a and 204b for each element.

Further, the light receiving elements 204a, 204b
Of the photoelectric currents that have been photoelectrically converted for each time,
A stationary light removing unit 206 as a stationary light removing unit for removing is provided. Further, a reset unit 207 for resetting each unit inside the AFIC 203 is provided.

Reference numeral 208 in the figure designates an arbitrary area in the photocurrent integrator 205, detects the maximum integration amount of the photocurrent in the set area, and temporarily samples the maximum integration amount. It is a monitor signal detection range setting and monitor signal output unit for holding and outputting a monitor signal for controlling the integration of the photocurrent. In addition, the AFIC 203 also includes an integration result of the photocurrent integration unit 205. A storage unit 209 for storing and holding a plurality of integral amounts, and an output unit 10 for outputting the monitor signal detection range setting and the contents of the monitor signal output unit 208 and the storage unit 209 to the outside are also provided.

The output section 10 may of course have a built-in amplifying means for amplifying a signal therein. It should be noted that, based on the external control signal, A
The control section 211 plays a role of controlling the inside of the FIC 203, and power is supplied to each section from a bias section 212, which is a collection of voltage sources, current sources, and the like.

On the other hand, there are also provided a light projecting light source 214 as auxiliary light means for irradiating the subject with light, and a light projecting lens 201c for condensing the light projected from the light projecting light source 214. The driving of the light projecting light source 214 is controlled by the driver unit 215.

The CPU 15 controls various operations of the camera other than the control of the distance measuring device. This CPU
If the 15 functions are limited to those related to distance measuring devices,
Mainly information acquisition and ranging calculation of the subject. Note that the functions related to distance measurement, such as obtaining information of a photographed object and distance measurement calculation, do not necessarily belong to the CPU 15 and may be built in the AFIC 203.

In addition to the configuration described above, although not shown in FIG. 2, EEPRO is a nonvolatile memory for storing data necessary for distance measurement, for example, adjustment data.
M and the like can be built in the AFIC 203.

Hereinafter, referring to the flowchart of FIG.
The operation of the distance measuring apparatus shown in FIG. 2 will be described in detail. In the following description, the description will proceed with reference to the configuration in FIG.

First, the CPU 15 performs the initial setting of the distance measuring device (step S31). That is, first, the CPU 15 itself performs a preparation operation for starting distance measurement, and after the completion of the preparation, enters a distance measurement operation. When the CPU 15 sends a control signal to the control unit 211, the control unit 211
. With this activation, the reset unit 207
The photocurrent integrator 205, the steady light remover 206, the monitor signal detection range setting and monitor signal output unit 8, and the storage unit 9 are reset.

Subsequently, the CPU 15 executes a pre-integration (step S32). That is, the CPU 15 sends a signal for operating the steady light removing unit 206 and a signal for setting the monitor signal detection range to the control unit 211. Upon receiving this signal, the control unit 211 enables the steady light removing unit 206 and further sets a monitor signal detection range. Next, the CPU 15 sends the light emitting unit 2 to the driver unit 215.
A signal for causing the light emitting section 14 to emit light is sent, and the light emitting section 14 is caused to emit light. Subsequently, the CPU 15 outputs a signal for starting photocurrent integration to the control unit 211. Upon receiving this signal, the control unit 211 causes the photocurrent integration unit 205
Is started. Then, after executing the predetermined operation, the CPU 15 sends a signal for terminating the photocurrent integration to the control unit 211, and terminates the photocurrent integration. The pre-integration at this time is an active mode. The control unit 211 controls the integration operation of the photocurrent integration unit 205 as the integration means. In addition to controlling the start / stop of the integration operation, switching of the amplification factor of the photocurrent or switching of the integration capacity is performed. To set / switch the sensor sensitivity of the light receiving elements (photoelectric conversion elements) 204a and 204b, set / switch the integration time, or perform pre-ranging (active operation) with steady light removal enabled and book with disabled steady light removal It is possible to perform control for selectively switching between integration (passive operation).

Next, the maximum integration amount and its position on the sensor are detected (step S33). That is, the CPU 15
After completion of the integration, the storage unit 209 stores all the integration amounts of the plurality of light receiving elements (photoelectric conversion elements) integrated by the photocurrent integration unit 205. The integration amount stored in the storage unit 209 is an image signal due to reflection of a light beam emitted from the light projection light source 214 on the subject. This is an image signal from which the stationary light component has been removed. The CPU 15 acquires this image signal via the output unit 210. When acquiring the image signal, the CPU 15 detects the maximum integral value and the position of the maximum integral value on the sensor.

Subsequently, the CPU 15 determines in step S3
The maximum integration value detected in step 3 is compared with a predetermined value (step S34). Here, when the maximum integration value is larger than the predetermined value, it is determined that it is estimated that the light beam emitted from the projection light source 14 is reflected by the main subject, and the process proceeds to step S35 described later. On the other hand, when the maximum integration value is smaller than the predetermined value, the main subject is located at a distance where the light emitted from the light projecting light source 14 does not reach, or the reflectance of the main subject is extremely low. It is determined that the main subject position cannot be estimated, and step S36 is performed.
Move to

In step S35, the CPU 15 sets a distance measurement area in a predetermined area centered on the point of the maximum integration amount. That is, in the scene shown in FIG. 4, sensor data is obtained by pre-integration (see FIGS. 5A and 5B), and a distance measurement area is set based on the pre-integration (FIGS. 5C and 5C). d)), the subject distance is obtained from the integration result and the set distance measurement area.

In step S36, the CPU 15 sets the distance measurement area in a predetermined area (default position) prepared in advance. For example, in the scene shown in FIG. 6, the pre-integration cannot estimate the required object position (see FIG. 7 (a),
(B)). In this case, the distance measurement area may be set at the default position. That is, as shown in FIGS. 7C and 7D, the distance measurement areas may be overlapped, or a plurality of distance measurement areas may be set without overlapping.

Subsequently, the CPU 15 performs the main integration (step S37). That is, the CPU 15
The internal reset unit 207 is activated to reset various means inside the AFIC 203. In this integration, the stationary light removal unit 2
06 is invalidated. Then, the monitor signal detection range is set, and the light emission of the light emitting light source 214 is controlled to be turned on / off as necessary, and integration is started. After the predetermined operation is performed, the integration is terminated. This integration is a passive mode.

Subsequently, the CPU 15 executes the correlation calculation and the closest selection (step S38). That is, the CPU 15
When the main integration in the passive mode is terminated, the integration amount for each photoelectric conversion element, which is the image signal of the subject, is stored in the storage unit 2.
09 is stored. Subsequently, the output unit 210 outputs and acquires an image signal of the subject. At this time, the CPU 15
May acquire all the image signals of the subject, but it is more efficient to acquire the image signal of only the ranging area set in step S35 or S36.

The CPU 15 performs a correlation operation (phase difference detection) for each ranging area based on the acquired image signal of the subject, and obtains a phase difference of the subject image for each ranging area. Such a phase difference corresponds to the distance of the subject. Then, the closest distance is selected from a plurality of object distances obtained from a plurality of distance measurement areas, and the closest object distance is set as a final distance measurement result.

After the above processing, the CPU 15 executes the AFIC
Performing post-processing including an operation of turning off the power of the power supply 203;
Thus, a series of distance measuring operations is completed (step S3).
9).

In the prior art, when a very wide range is measured by a one-dimensional or two-dimensional sensor, the number of distance measurement areas to be set is very large, and complicated calculations such as correlation calculations are performed. It must be repeated a very large number of times, requiring a long time and a large time lag, or an expensive CPU must be used to increase the speed.

On the other hand, according to the operation of the flowchart of FIG. 3 described above, while the projection light source 214 is turned on,
In the active mode with the steady light removal unit 206 enabled,
A predetermined short-time pre-integration is performed to project light from the subject 21
The position of the main subject can be estimated by acquiring the distribution of the reflected light (integrated image signal) of the light beam emitted by the light source 4.

Therefore, in the operation of the flowchart of FIG. 3, the minimum distance measurement area necessary for detecting the estimated distance of the main subject with high accuracy can be set. There is no need to perform unnecessary calculations in. In other words, a fast and expensive CPU
This eliminates the need for using a time stamp, thereby reducing the time lag.

Next, the schematic operation of FIG. 1 will be described with reference to the flowchart of FIG. When the photographer presses a release switch (not shown) at the time of photographing, the CPU 15 detects this and starts a focus adjustment operation.

In the focus adjusting operation, as shown in step S80 of FIG. 8, first, the subject distance is measured by the hybrid type distance measuring means 18. This distance measuring operation is as described in FIG.

Next, in step S81, the driving amount of the focusing lens in the photographing lens 10 in FIG. 1 from the current position to the in-focus position is calculated. As for the current position of the focusing lens, the result of the previous driving is stored and held by the CPU 15. The CPU 15 calculates and calculates the driving direction and the driving amount up to the in-focus position.

In step S82, the driving amount of the focusing lens is corrected. The reason for correcting this lens drive amount is that the present invention measures the distance in the hybrid format, performs high-speed lens drive, and finally adjusts the focus with high precision by the hill-climbing method, so the first lens drive is before the focal point. It is necessary to stop. The correction amount is determined in consideration of the current focal length of the imaging optical system, the environmental temperature, and if necessary, the dimensional variation of components, the assembly accuracy, and the like. The CPU 15 also calculates and controls this correction amount.

In step S83, the focusing lens is actually driven. The driving of the focusing lens is
This is performed using the driving unit 16 and the position detecting unit 17 under the control of the CPU 15. Stop the focusing lens just before the focal point.

Then, in step S84, the focus is adjusted with high accuracy by the hill-climbing method.

As a result of the operation shown in FIG. 8, high-speed and high-precision focus adjustment can be realized. The focus adjustment of the hill-climbing method is performed by the image pickup device 12, the image pickup device control means 13, the video signal processing means 14, and the CPU 15, and the details are the same as those described in the related art.

The above description of FIG. 8 will be described with reference to FIG. 9 in terms of the movement of the focusing lens.

FIG. 9 is a diagram showing the relationship between the focusing lens position and the focus evaluation value. The horizontal axis represents the focusing lens position and the vertical axis represents the focus evaluation value.

In the present invention, the focus evaluation values are actually scanned at points D to E, but it is assumed that the focus evaluation values from ∞ to the closest are known.

In FIG. 9, when the focal point is point B and the current position of the focusing lens is point A, the estimated focusing point C is obtained as a result of distance measurement by the hybrid type distance measuring means 18. The driving target of the focusing lens is changed (corrected) by a first predetermined amount up to a point D before the estimated focal point C,
The focusing lens is driven from point A to point D. Here, the first predetermined amount obtained by correcting the point C to the point D is a predetermined lens driving amount, and takes into account the optical characteristics such as the focal length of the imaging optical system, the environmental temperature, the assembly accuracy, and the like. A variable that is determined (as a parameter).

Next, the focusing lens is scanned and driven from the point D to the point B while obtaining the focus evaluation value from the point E to the point E. Points B to E are where the focus evaluation value has decreased by the second predetermined amount in the focus evaluation value.

When scan driving is performed from point D to point E, the focal point B
Is obtained, the driving direction is turned back at the point E, the focusing lens is driven to the focal point B, and the focus adjustment operation ends.

Here, the second predetermined amount is an amount necessary for detecting the focal point B which is the peak value of the focus evaluation value, and takes into account the focal length of the imaging optical system, the environmental temperature, and the like. I can decide. Further, if necessary, the dimensional accuracy, characteristics, and assembly accuracy of the component may be considered in determining the second predetermined amount.

The above description of FIG. 8 and FIG. 9 is the operation for the general subject in the embodiment of FIG.

Next, the operation in the case of a special subject in the embodiment of FIG. 1 will be described. This will be described with reference to the flowchart of FIG. 10, the movement of the focusing lens of FIG. 11, and if necessary, FIG.

Since the distance measuring means 18 of the hybrid system hardly has a poor subject, the estimated focal point C can be obtained in most scenes in FIG. Next, when aiming at the focal point B by the hill-climbing method, one type of approach is not enough because the focus evaluation value curves are various. A processing method capable of coping with such a variety of focus evaluation value curves is the processing of the flowchart in FIG. The points of the processing method in FIG. 10 are (1) changing the direction of lens drive as necessary (see step S108), and (2) extending scan drive for mountain climbing (see step S118).
Here, when the former lens driving direction is changed, the correction of the backlash of the gear train is an important technique, which is also performed in the present embodiment, but the description of the technique is omitted because it is publicly known.

In step S100 of FIG. 10, the subject distance is measured by the hybrid type distance measuring means 18. A supplementary description of the hybrid type distance measuring means 18 will be given. As described above, the hybrid type distance measuring unit 18 can be switched between the active type and the passive type as necessary, and can be considered as a distance measuring unit having almost no subject at all. If you dare to mention your weak subject,
It's about "Lowcon landscape" or "dark landscape".

In step S101, it is determined that distance measurement is impossible. The inability to measure the distance is determined by a low contrast determination or a known reliability determination. Regarding low contrast and reliability judgment,
It is described in Japanese Patent Application No. 11-334546. At this time, the distance measurement becomes impossible because the "low contrast scenery" and the "dark scenery" indicate that both the active method and the passive method in the distance measuring means 18 indicate that the distance measurement is impossible by the low contrast determination or the reliability determination. Is determined.

If the distance cannot be measured in step S101, the process jumps to step S121 to drive the lens to a distant view photographing lens position. This lens position is a lens position for photographing a distant view including infinity (∞) or infinity within the depth of field. If the distance cannot be measured in S101, the lens is driven in step S102. The lens driving has already been described with reference to FIG. 9, but the same applies to the case of FIG. 11, with the point A at the initial position (current position) of the lens as the starting point and the first point from the estimated focal point C before the focal point B. Point D with quantitative correction
Drive the lens to The above description is for the case where the subject is a low contrast. However, FIG. 11 shows a case where the lens position is driven from the closest side to the side of ∞.

Here, FIG. 11 will be supplementarily described. The focus evaluation value curve indicated by a dotted line including the points C ′ and D ′ is a case of a normal subject, and a special subject such as a low-contrast subject is a focus evaluation value curve indicated by a solid line. In the case of a normal subject, the estimated focal point obtained by the hybrid type distance measuring means 18 is the point C ′. After the lens is driven from the current lens position A 'to the point D' before the point C ', the focus is adjusted by the hill-climbing method.

In step S103, a focus evaluation value is obtained. In step S104, the focus evaluation value and the predetermined value C0
Is determined. Here, when the focus evaluation value is smaller than C0, it is determined that the subject is low contrast.
However, since the distance measurement means 18 of the hybrid system can measure the distance even in the low-contrast subject in the active mode, the process jumps to step S122 to move the focusing lens to the lens position corresponding to the estimated focusing position obtained from the result of the distance measurement of the hybrid system. Drive. Referring to FIG. 11, the focusing lens is driven from point D to point C (estimated in-focus position).

In step S104, the focus evaluation value is set to a predetermined value C.
If it is larger than 0, the process moves to step S105 and executes lens driving. The focus adjustment of the hill-climbing method has started from step S105. That is, the lens driving is a scan driving that drives the focusing lens by a predetermined amount while acquiring the focus evaluation value.

In step S106, a focus evaluation value is obtained. In step S107, it is determined whether the focus evaluation value has decreased from the previous time. If it has decreased, step S1
At 08, the driving direction of the lens is changed. Step S107
And S108 determine whether the lens drive is correct,
This corresponds to driving direction correcting means for correcting the driving direction.

In step S109, the upper limit value LDmax of the number of times of lens driving is set to a variable i.

In step S110, the lens drive execution extension flag (f-enchyou) is cleared.

At step S111, lens drive is executed.
In step S112, a focus evaluation value is obtained. Step S
At 113, it is determined whether or not the focus evaluation value is a peak. If the focus evaluation value is determined to be a peak, the lens position at that time is stored.

In step S114, it is determined whether the peak evaluation value has decreased by a second predetermined amount from the peak value.

If the peak is reduced by the second predetermined amount from the peak in step S114, the peak has been detected normally, and the process jumps to step S123 to move the focusing lens to the position of the focus evaluation value peak obtained by the hill-climbing method. Drive.

Here, the scanning operation of the hill-climbing method will be described with reference to FIG. 9. Scan driving is started from point D, the peak of point B is detected, and from point B to point E at which the focus evaluation value decreases by a second predetermined amount. Continue scanning drive. After moving the focusing lens to the point E, the focusing lens is driven to the focal point of the point B. At this time, since the driving direction of the focusing lens changes, it is necessary to consider the backlash of the gear train that is the lens driving means, and the present embodiment also corrects the backlash amount. The method of correcting the backlash amount is well-known, and a detailed description thereof will be omitted.

Returning to FIG. 10, if the second predetermined amount has not decreased from the peak in step S114, the process proceeds to step S114.
Proceed to 115. In S115, the variable i that is the remaining number of times of lens driving is decremented.

Subsequently, in step S116, i is 0.
Is determined. If i is not 0, the process returns to step S111 because lens driving is continued.

As described above, steps S111 to S116
Constitutes a loop, but can deviate from the loop processing in the following cases (1) and (2). That is, (1) if the focus evaluation value decreases by the second predetermined amount after the peak of the focus evaluation value is detected, and normal peak detection can be performed (Yes in S114), (2) the maximum number of executions of the lens driving When the lens drive is executed by (LDmax) (when i = 0 in S116), the processing is outside the above loop processing. Therefore, the above loop processing is repeated until the above condition (1) or (2) is satisfied. That is, the hill-climbing scan driving is repeated.

If i = 0 in step S116, the flow advances to step S117. In step S117, it is determined whether or not the execution extension flag (f-enchyou) is 0 or 1. The process of step S117 does not pass if the peak of the focus evaluation value is normally detected in the normal subject.
That is, when the process goes through step S117, the peak of the focus evaluation value has not been detected yet. S11
If the execution extension flag (f-enchyou) is 1 in step 7, the scan drive of the lens drive is extended (step S1).
18) Since the focus evaluation value peak could not be detected despite the execution of step 18), the process jumps to step S120 to drive the focusing lens to a predetermined lens position (normal focus position) determined in advance. It is conceivable that the normal focus position is changed in consideration of the focal length of the taking lens 10, the brightness of the subject, the taking mode of the camera, and the like.

At S117, the execution extension flag (f-ench)
If you) is 0, the lens drive has been performed the maximum number of times (LDmax) but the peak has not been normally detected, and the lens drive has not been extended (S118). Work to extend the drive scan drive. The maximum number of executions (LDmax) corresponds to a first predetermined lens drive amount.

In step S118, the number of extensions (LDplus) of execution of lens driving is set to a variable i. The number of execution extensions (LDplus) corresponds to a second predetermined lens drive amount. In step S119, the execution extension flag (f-
Set 1 to (enhyou). Then, the process jumps to step S111 and proceeds to steps S111 to S111.
The loop processing of step 116 is executed an extended number of times.

As described above, according to the embodiment shown in FIG. 10, it is possible to adjust the focus of any object at high speed and with high accuracy.

In the automatic focusing device shown in FIG. 1, a hybrid type distance measuring means of outside light type and TTL (Through Th
e Lens) type mountain climbing distance measuring means. FIG. 12 shows an example of the appearance of an electronic camera having the automatic focusing apparatus according to the embodiment.

FIG. 12A is a view of the camera body, and shows the positional relationship between the image pickup optical systems (10, 11) and the external light type hybrid distance measuring means 18. When the external light type hybrid distance measuring means 18 is employed,
Since the distance measuring means 18 is arranged outside the optical axis of the imaging optical system (10, 11), parallax (parallax) with respect to the imaging optical system poses a problem. In the embodiment of the present invention, the following measures are taken. ing.

That is, the hybrid type distance measuring means 18 is used as a multi (multi-point) distance measuring means to have a multi-point distance measuring area position.

FIG. 12B shows a multi-field (multi-point) distance measuring area visual field with respect to the image capturing visual field. As a multi (multi-point) arrangement, one ranging area is provided at the center of the imaging field of view, and the other ranging areas are imaging optical systems (10, 11).
And the hybrid type distance measuring means 18 are displaced in the same direction as the parallax direction. In other words, a plurality of distance measuring points are set in a range along the direction in which parallax occurs. The multi-ranging means automatically obtains an effect close to parallax correction by selecting the closest distance based on each of the multi (multi-point) ranging area data. The external light type hybrid distance measuring means
When the light receiving sensor is a line sensor, the light receiving sensor is arranged so that parallax does not occur in the direction perpendicular to the line direction.

By using such a hybrid multi-ranging means, it is possible to adjust the focus comfortably without having to pay particular attention to parallax.

[0113]

As described above, according to the present invention, it is possible to provide an automatic focus adjusting device capable of always performing high-speed and high-precision focus adjustment regardless of the state of a camera regardless of a subject without a weak subject. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an automatic focusing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a distance measuring apparatus provided with a hybrid distance measuring means and an auxiliary light means in FIG. 1;

FIG. 3 is a flowchart illustrating an automatic focus adjustment operation of the distance measuring apparatus in FIG. 2;

FIG. 4 is a diagram showing an example of a shooting scene.

FIG. 5 is a view showing sensor data and a distance measurement area corresponding to the shooting scene of FIG. 4;

FIG. 6 is a diagram illustrating an example of a shooting scene.

FIG. 7 is a view showing sensor data and a distance measurement area corresponding to the shooting scene of FIG. 6;

FIG. 8 is a flowchart for explaining a schematic automatic focusing operation of the embodiment of FIG. 1;

FIG. 9 is a diagram showing a relationship between a focusing lens position and a focus evaluation value in the case of a normal subject.

FIG. 10 is a flowchart illustrating an automatic focus adjustment operation including a case of a special subject.

FIG. 11 is a diagram illustrating a relationship between a focusing lens position and a focus evaluation value in the case of a low contrast subject.

FIG. 12 is a view showing an example of an external appearance of an electronic camera having the automatic focusing apparatus according to the embodiment.

FIG. 13 is a block diagram of an automatic focus adjustment device using a hill-climbing method.

FIG. 14 is a block diagram illustrating a configuration of a video signal processing unit in FIG. 13;

FIG. 15 is a diagram showing a relationship between a focusing lens position and a focus evaluation value in a focusing operation in a hill-climbing method.

FIG. 16 is a block diagram of an automatic focusing apparatus using an autocorrelation method.

FIG. 17 is a block diagram illustrating a configuration of a video signal processing unit in FIG. 16;

FIG. 18 is a perspective view showing the stop in FIG. 16;

FIG. 19 is a diagram showing a state of focusing, a front focus state, and a rear focus state in the case where an image is formed on an image sensor using the diaphragm of FIG. 18;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Photographing lens 11 ... Aperture 12 ... Image sensor 13 ... Image sensor control means 14 ... Video signal processing means (including focus evaluation means) 15 ... CPU 16 ... Drive means 17 ... Position detecting means 18 ... Hybrid type distance measuring means 19 ... Auxiliary light means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/225 G02B 7/11 N 5/232 D // H04N 101: 00 G03B 3/00 A F term ( Reference) 2F065 AA02 AA06 BB29 DD03 DD06 FF09 FF10 FF24 GG21 JJ02 JJ25 QQ21 QQ29 QQ32 QQ34 2F112 AA08 BA05 BA06 CA02 CA12 DA21 DA26 FA03 FA21 FA29 FA33 FA45 2H011 AA03 BA05 BA14 BA31 BB04 BB05 CB04 BB04 BB04 BB04 ABB03 BB04 BB04 CD19 CE06 CE08 CE14 DA02 DA03 DA07 DA17 DA37 FA48 5C022 AA13 AB15 AB22 AB24 AB29 AB30 AC31 AC42 AC54 AC69 AC74 AC78

Claims (1)

[Claims] 1. An at least one pair of integral type light receiving sensors for receiving a subject image, a stationary light removing circuit provided for each pixel of the integral type light receiving sensor, and auxiliary light means for illuminating the subject. Integrating the subject image signal from the integrating type light receiving sensor.
An integration means capable of switching an integration mode between an active mode and a passive mode when turned off, and an integration control for controlling an integration operation of the integration means and capable of performing a control for selectively switching between an active mode and a passive mode Means for performing distance measurement based on the amount of integration of the subject image signal obtained by the integration means, and driving the focus adjustment optical system to perform focus adjustment; An image sensor for imaging a subject on the optical axis of the system, and a focus evaluation unit that extracts a subject image signal from a predetermined region of the image sensor and calculates a focus evaluation value;
Second focus adjustment means for performing focus adjustment by detecting the maximum value of the focus evaluation value while driving the focus adjustment optical system;
Wherein the first focus adjustment means is arranged outside the optical axis of the imaging optical system and is a multi-point focus adjustment means, and a plurality of multi-point focus adjustment areas are provided with the first focus adjustment means and the imaging means. An automatic focusing device which is arranged along the direction of parallax with an optical system.