JP3164447B2 - Automatic focusing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera focus detection apparatus for adjusting the focus of a desired subject in a camera viewfinder frame.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a technique for detecting a gaze direction of a photographer looking through a finder and performing various operations of a camera based on the gaze information.

For example, Japanese Patent Application Laid-Open No. Hei 4-190177 discloses a technique in which a line-of-sight area of a predetermined range substantially coincident with the line-of-sight direction is displayed on a finder field-of-view frame, and the focus of an object in the field of view is detected. I have. This technology detects a line-of-sight direction in a viewfinder frame of a camera, displays a line-of-sight region in a predetermined range substantially coincident with the line-of-sight direction on the frame, and detects a focus of a subject in the line-of-sight region. It is. As described above, this technique has a feature in that focus detection is performed based on an output within a predetermined range in the viewing direction of the screen.

[0004]

However, according to the technique disclosed in Japanese Patent Laid-Open No. 4-190177, an index representing the direction of the line of sight is faithfully displayed in the viewfinder field frame according to the slight movement of the line of sight. However, the display gives the photographer discomfort.

Further, in the above-mentioned technique, since the focus is always focused on the position of the index, the lens is driven each time the position of the index is changed. It also leads to an increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to reduce power consumption and reduce power consumption by efficiently performing a finder display indicating the direction of a photographer's line of sight and driving a lens. An object of the present invention is to eliminate discomfort given to a person and to quickly and accurately focus on a desired subject.

[0007]

In order to achieve the above object, according to the present invention, the line of sight of a photographer in a viewfinder frame is provided.
Gaze detection means for repeatedly outputting a detection signal according to the direction,
A filter for calculating the moving average of the output signal of the line-of-sight detection means
Filter processing means, based on the output of the filter processing means.
The view frame that approximately matches the line of sight
Gaze direction display means for displaying in a frame, and the gaze detection means
The above gaze direction detected by is compared with the previous detection direction
And does not change more than a predetermined amount and is substantially constant for a predetermined time.
Selecting means for selecting a focus detection area when
Object in the focus detection area selected by the selection means
Focus detection means for performing focus detection;
Focusing means for adjusting the focus of the lens based on the force;
Provided is an automatic focusing device comprising:
It is.

[0008]

[0009]

That is, in the automatic focusing device according to the present invention, the line-of-sight
In the view direction of the photographer in the viewfinder frame
The corresponding detection signal is output repeatedly and sent to the filter processing means.
The moving average of the output signal of the line-of-sight detection means
The line-of-sight direction display means outputs the output of the filter processing means.
Based on the force, a field frame that substantially matches the line of sight
Is displayed in the frame of the gender field, and the line of sight is detected by the selection means.
The gaze direction detected by the means is the same as the previous detection direction.
In comparison, it does not change more than a predetermined amount and is substantially constant for a predetermined time.
The focus detection area is selected when the
The object in the focus detection area selected by the selection means
Focus detection is performed on the focus, and the focus
The focus of the lens is adjusted based on the output of the detecting means.
You.

[0010]

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing a configuration of an auto focussing (AF) camera to which a focus detection device of the present invention is applied.

As shown in FIG. 1, the line-of-sight direction detecting sensor 15 is connected to a CPU 18 via an A / D converter 17, and the CPU 18 is provided with a line-of-sight detection start switch SW3. Further, the CPU 18 controls the line-of-sight direction detecting sensor 1 via the sensor driver 16.
5 and is also connected to a liquid crystal display section 21 via a liquid crystal driver 20. And this CPU 18
Is also connected to the A / D converter 17 and the CPU 6.

Then, a photographing lens 1 and a focus detection optical system 2
Is connected to the CPU 6 via the A / D converter 5, and the CPU 6 is connected to the area image sensor 3 via the sensor driver 4. A /
It is also connected to the D converter 5. And this CP
U6 is connected to a liquid crystal display section 12 via a liquid crystal driver 11, and is also connected to a lens drive circuit 8 for controlling a motor 9 and an exposure control circuit 13. further,
The CPU 6 includes an information input unit 14 and a photointerrupter 1.
0, a lens ROM 7 is also connected. And this C
The PU 6 is provided with a camera operation start switch SW1 and a release switch SW2. And CPU
A timer 19 is built in 18.

In such a configuration, the area image sensor 3 photoelectrically converts an image formed by the focus detection optical system 2 into an electric signal, and a driver 4 drives and controls the area image sensor 3. Things. The A / D converter 5 converts the analog output from the area image sensor 3 into a digital signal and outputs the digital signal to the CPU 6. The CPU 6 controls the entire camera except for the line-of-sight direction detection. Based on the output of the area image sensor 3, calculation of a subject distance, display of an aperture value and shutter speed, and exposure control are performed.

Further, a lens ROM 7 is provided in the lens barrel, and stores various data necessary for focus detection such as an F number of the photographing lens 1 and a conversion coefficient for obtaining a defocus amount from an image shift amount. Is what you do. The lens driving circuit 8 moves the position of the photographing lens 1 by driving the motor 9 under the control of the CPU 6.

Normally, in the AF operation for detecting the subject distance and driving the photographing lens 1 based on the distance information, it is necessary to feed back the driving amount of the photographing lens 1 to the CPU 6. In this case, it is common to substitute the amount of movement of the photographing lens 1 by the number of rotations of the driving motor 9. Then, the photointerrupter 10 detects this rotation speed.

Further, the CPU 6 selects, from the photoelectric conversion output signal of the area image sensor 3, a signal in a predetermined area substantially coincident with the line of sight in the viewfinder frame, and defocuses the object in the predetermined area. , And averages the sensor output signals in the predetermined area to obtain an average luminance Bv, and performs an Apex operation together with information such as the film sensitivity Sv, shutter speed Tv, and aperture value Av input from the information input unit 14. , Shutter speed Tv and aperture value Av. The shutter speed Tv and the aperture value Av are displayed on the liquid crystal display 12 via the liquid crystal driver 11.

Further, a timer 19 built in the CPU 18 is for measuring an accurate time, and the line-of-sight direction detecting sensor 15 converts an image formed by the line-of-sight direction detecting optical system into an electric signal. It performs photoelectric conversion.
The sensor driver 16 drives the line-of-sight direction detection sensor 15. The analog output signal of the line-of-sight direction detection sensor 15 is converted into a digital signal by the A / D converter 17 and stored in the RAM in the CPU 18. Is done.

The CPU 18 controls the entire control for detecting the direction of the line of sight.
The visual line direction is calculated on the basis of the output signal, and the visual field frame is displayed in an area substantially coincident with the visual line direction in the viewfinder visual field frame. Then, this field frame is supplied to the liquid crystal display unit 21 via the liquid crystal driver 20, for example, as shown in FIG.
It is displayed as shown in (b). Next, FIG. 3 is an optical layout diagram showing the optical system of the embodiment in detail.

In FIG. 1, the focus detecting optical system 2 includes:
It comprises a half mirror 32 provided between the front group lens 31 and the rear group lens 34 of the photographing lens 1, a field lens 33, and a visual field transmission optical system 47 including a brightness stop, an optical axis tilt prism, and the like. The visual field transmission optical system 47
Is configured to divide a guided light beam into two by pupil division and form two images Ia and Ib on the area image sensor 3.

Then, a parallel light beam is formed from the infrared LED 42 via the lens 41, and the parallel light beam enters the eye 26 via the dichroic mirrors 40 and 39. And
The light reflected by the eye 26 is a dichroic mirror 39, 4
The image is captured by the sensor 44 via the lens 0 and the lens 43, and the line-of-sight direction is calculated.

As described above, the photographing lens 31 and the main mirror 3
5, the position of the gazing point observed by the photographer can be detected via the slot 36, the pentaprism 38, and the dichroic mirror 39. In the figure, 45 is a shutter and 46 is a film. Here, the principle of focus detection according to the present invention will be described. In the present embodiment, a phase difference method for obtaining a subject distance from an interval between two images Ia and Ib by pupil division is adopted. That is, the photographing lens 1
The light beam that has passed through the front lens group 31 and the half mirror 32 is divided by the visual field transmission optical system 47 and formed as images Ia and Ib on the area image sensor 3, respectively.

In this case, for example, at the time of focusing, FIG.
As shown in the figure, two images Ia and I
b is imaged at a predetermined interval fa. In contrast, when the camera is in focus and in front of the subject, the two images Ia and Ia are in focus as shown in FIG.
The interval fb of b becomes narrower than the interval at the time of mating. Furthermore, when the subject is in focus after the subject, FIG.
As shown in the figure, the interval fc between the two images Ia and Ib is wider than the interval fa at the time of focusing.

Therefore, the distance to the subject can be calculated by calculating the interval between these two images Ia and Ib. The above is the principle of focus detection by the phase difference method. Next, the principle of gaze direction detection is described in, for example, JP-A-2-5, JP-A-2-65834, or the IEICE technical report PRU88-73, PP17-.
24.

These methods detect the direction of the line of sight from the combination of the pupil of the eye and the corneal reflection image (first Purkinje image) or the combination of the iris and the corneal reflection image, and are attracting attention as a method of designating the point of regard. FIG. 4 shows an example of the output waveform of the corneal reflection image, pupil, and iris of the eye.

For example, FIG. 6 shows a corneal reflection image when the parallel light beam L is incident on the eye and the eye is looking at the center (solid line).
That is, it is a diagram showing a positional relationship between the first Purkinje image P and the first Purkinje image P ′ when the eye is looking in the direction of the angle θ (dotted line).

In the figure, virtual images P and P 'can be located at a distance of about r / 2 from the corneal surface, where r is the radius of curvature of the cornea. The movement of the eye is performed with the center C of the eyeball as the center of rotation. Then, when the eyeball rotates by θ _x , the center of the cornea moves from O to O ′, and the image of the parallel light beam moves laterally by ￣OCsin θ _x (1) and comes to the position of I ′. become. ￣OC is about 6 mm, so when θ = 5 °, the change is about 0.5
mm. Now, as shown in FIG. 4, assuming that the x coordinates of the pupil edge are x ₁ and x ₂ , the coordinates x of the center position C of the pupil are obtained.
_c is expressed as x _c = (x ₁ + x ₂ ) / 2 (2). Further, in the range rotation angle θ is small and the x coordinate of the position P of the first Purkinje image and x _p,

[0028]

(Equation 1) Holds.

Actually, x _c and x _p are obtained by performing image processing on the image as shown in FIG. 4 projected on the gaze direction detecting sensor 15 via the gaze detection optical system (magnification β). can get. By rewriting these x _c and x _p as x _c ′ and x _p ′,

[0030]

(Equation 2) Next, the rotation angle theta _y in the vertical direction can also be determined in exactly the same manner. If the θ _x and θ _y are known, the center coordinates (x, y) of the field frame that matches the line of sight in the viewfinder field can be obtained from the viewfinder optical system α magnification. Less than,
The operation of the focus detection device according to the present embodiment will be described with reference to the flowcharts of FIGS. 7 and 8 are flowcharts showing the operation of the CPU 18.

When the operation starts (step S100),
First, the CPU 18 causes the liquid crystal display unit 21 to display the AF visual field area at the center of the screen (step S101), and then determines whether or not the visual line detection has been started, specifically, the switch SW.
It is detected whether or not 3 has been pressed (step S102).

When the line-of-sight detection is started, the flags and constants to be used are initialized. That is, "0" is stored in FLAG1, "1" is stored in i, and "0" is stored in N (step S103). Subsequently, the output signal of the line-of-sight detection sensor 15 is A / D converted (step S104),
The digital data is stored in the RAM in the CPU 18 (step S105).

Subsequently, a timer counter built in the CPU 18 is used.
Resets the timer 19 and starts the timer counter at the same time.
(Step S106). And look at the above principle
Calculate the coordinates (x, y) of the direction and store x in the memoryx
Store y in (1) and Mepy (1) respectively
(Steps S107 and S108).

Subsequently, it is determined whether or not FLAG1 is "0" (step S109). This step S10
9, when FLAG1 is "0", the memories Mepx (1),
The contents of Mepy (1) are stored in memories Mepx (0), Mep
Transfer to y (0) (step S119), store "1" in FLAG1, and proceed to the next step S120 (step S115).

On the other hand, in step S109, F
When LAG1 is “1”, the calculated line-of-sight direction data (Mepx (1), Mepy (1)) is replaced with the previously calculated line-of-sight direction data (Mepx (0), Mepy (1)).
(0)), it is determined whether or not it has changed by a predetermined amount or more (step S110). That is, it is determined whether or not (Mepx (0) -α) ≦ (Mepx (1)) ≦ (Mepx (0) + α) (5), where α is a constant.

When the relationship of the above equation (5) holds, it is recognized that the line-of-sight direction in the left-right direction (hereinafter, referred to as x direction) has not changed. ) Is determined. Then, similarly to the above equation (5), when (Mepy (0) −α) ≦ (Mepy (1)) ≦ (Mepy (0) + α) (6), the gaze direction in the y direction also changes. It recognizes that it has not been done (step S116).

When it is recognized that the line-of-sight direction has not changed in both the x and y directions, the contents of the timer counter are determined (step S117). If the TIME is equal to or longer than the predetermined time t1, the CPU 6 is interrupted. The signal INT1 is transmitted (step S118). And
When receiving the interrupt signal INT1 from the CPU 18, the CPU 6 temporarily suspends the operation up to that point and branches to the interrupt routine INT1.

As shown in FIG. 10, when the interrupt routine "INT1" is entered (step S301), the interrupt by the interrupt signal INT1 is prohibited (step S302). This is because if the interrupt receiving state is left, the interrupt staff may overflow. Next, the gaze direction data (Mepx,
Mepy) is received and stored in the memory (step S
303).

Then, the interrupt prohibition of the INT1 is released (step S304), and the address of the interrupt staff is initialized (step S305).
Returning from 1 ", the operation of the main program is continued (step S306).

Now, returning to the main program, the CPU 18 sends the CPU 6 a line of sight direction data (Mep).
x (1), Mepy (1)). That is, CP
U6 receives the line-of-sight direction data only when the line-of-sight direction data does not change for a predetermined time t1 or more, and focuses on an object in the finder field frame that substantially matches the line-of-sight direction (step S119).

On the other hand, in the above S110 and S116,
When the gaze direction in the x and y directions is changing, the CPU 6
The interrupt signal INT2 is transmitted to the
1). When the CPU 6 receives the interrupt signal INT2 from the CPU 18, the CPU 6 branches to an interrupt routine "INT2".

As shown in FIG. 11, when an interrupt routine "INT2" is entered (step S401), first, IN
The interruption of T2 is prohibited (step S402). Then, after the lens driving is stopped (step S403), the inhibition of the interruption by the interruption signal INT2 is released (step S404). Subsequently, after the initialization of the interrupt stack is performed (step S405), the process returns from the interrupt routine to the main program. This prevents useless driving of the lens (step S40).
6).

When returning to the main program, the line-of-sight direction data (Mepx (1), Mepy (1)) are transferred to the memories Mepx (0), Mepy (0), respectively (step S112), and the timer 19 is set. At the same time as resetting again, the timer is started (step S11
3).

The reason why FLAG1 was checked in step S109 is that comparison with the previous data is necessary in steps S110 and S116, but there is no previous data at the beginning of the start of the CPU 18. The above is the operation for determining the AF field of view for driving the lens.

Here, the eyeballs are constantly moving slightly, and even if the user intends to look at a certain direction, the eyeball is sometimes unconsciously instantaneous or the line of sight changes greatly. If the display of the visual field frame is performed following the movement of the eyeball, the display is very flickering and is difficult to see.

Therefore, in step S120 and subsequent steps, the display of the visual field frame is made smooth and smooth by taking a time-moving average (a low-pass filter) in the visual line direction. That is, the program after step S120 is a program for determining the field coordinates for displaying the field frame of the AF field area.

In step S120, first, the content of the constant counter N is incremented. N is a counter for detecting how many times the gaze direction data has been updated since the gaze direction detection was started. That is, when performing the moving average calculation, a correct result cannot be obtained until the number of data (5 in this embodiment) necessary for performing the moving average calculation is obtained. At this time, the gaze direction data for the moving average calculation is updated. That is, Mepx is stored in the memory Mepx (i).
The contents of (i-1) are stored in Mepy (i) as Mepy (i-
Transfer the contents of 1) (i = 1 to 5) (step S12)
1 to S123). Subsequently, if the content of the counter N is not "5", the process returns to step S107, and if the content (N) of N is 5, the moving average

[0048]

(Equation 3)

Are calculated, and the memories Mdspx, M
dspy (Steps S124 and S12)
5). Since these Mdspx and Mdspy are the coordinates of the visual field frame indicating the visual line direction, the visual line direction display position is updated using these coordinates (step S126). Then, CPU
It is determined whether or not the flag signal FLAG2 connected to No. 6 is "1". When FLAG2 is normally released at "0", "1" is transmitted from CPU 6 (step S).
127).

If FLAG2 is "1" in this step S127, it is determined whether or not FLA3 is "1" (step S128). This FLAG3 is a CPU6
Is normally “0”, and when the exposure ends, CP
U6 sets FLAG3 to "0". If FLAG3 is "1" in step S128, the process returns to step S100 (step S129). Next, FIG. 9 is a flowchart showing the operation of the CPU 6.

When the operation starts (step S200),
It is determined whether or not the start switch SW1 is turned on (step S201). And the start switch S
If W1 is pressed, the line-of-sight direction data memory Mep
x and Mepy (which are line-of-sight direction data in the x and y directions, respectively) are initialized.

Here, the line-of-sight direction data (γ, 7) corresponding to the field frame at the center of the screen shown in FIG. 2A is stored in the memories Mepx and Mepy. Therefore, when the line-of-sight direction data is not transmitted from the CPU 18, the focus is set on the object in the visual field frame at the center position of the screen (step S2).
02).

Subsequently, A / D conversion of the output signal of the area image sensor 3 is performed (step S203). Then, the sensor output signal of the visual field determined by Mepx and Mepy is selected (step S204), and the average brightness BV of the sensor output signal is calculated (step S205). Further, the film sensitivity S input by the information input unit 14
Apex calculation (BV + SV = AV + TV) is performed using V, aperture value AV, and shutter speed TV (step S206).

Then, the shutter speed TV and the aperture value AV obtained by the apex calculation are displayed on the liquid crystal display 12 (step S207). Further, based on the above-described principle, a defocus amount for an object existing in the visual field region, that is, a defocus amount from a focus matching position is calculated using the sensor output signal of the visual field region determined by the above Mepx and Mepy ( Step S208).

Subsequently, the lens driving amount is calculated (step S209), and a signal is sent to the motor 9 to drive the lens by a predetermined amount (step S210). When the lens driving is completed, the state of the release switch SW2 is checked to determine whether or not the release has been performed. If the release switch SW2 is open, it is determined that the release has not been performed, the process returns to step S203, and the above program is repeated.

If the release switch SW2 is closed in step S212, "1" is output to FLAG2 connected to the CPU 18 and "0" is output to FLAG3 (step S213). Then, exposure control is performed (step S214). When the exposure control is completed (step S215), the FLAG 3 connected to the CPU 18 is controlled.
"1" and "0" to FLAG2 (step S
216). Thus, the process returns to step S203, and the same operation is repeated.

As described above in detail, in the focus detection device for a camera according to the present invention, in the focus detection device that focuses on the line of sight substantially coincident with the line of sight in the finder field of view, a field frame substantially coincident with the line of sight is set. Thus, the image can be stably displayed in the viewfinder frame without being affected by the slight movement of the line of sight.

Further, the lens drive for focusing on the object in the visual field frame substantially coincident with the above-mentioned line-of-sight direction can be smoothly performed without being influenced by fine movement of the line-of-sight or a large instantaneous change.

[0059]

According to the present invention, power consumption is reduced and discomfort given to an observer is eliminated by efficiently performing a finder display and a lens drive indicating the direction of the photographer's line of sight. A focus detection device for a camera that quickly and accurately focuses on a subject to be flashed can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of an AF camera to which a focus detection device of the present invention is applied.

FIGS. 2A and 2B are diagrams showing an example of a finder display. FIG.

FIG. 3 is an optical layout diagram illustrating in detail an optical system of a focus detection device according to the embodiment.

FIG. 4 illustrates an example of output waveforms of a corneal reflection image, a pupil, and an iris of an eye.

FIGS. 5A to 5C are diagrams for explaining the principle of focus detection.

FIG. 6 is a diagram showing a positional relationship where a first Purkinje image is formed.

FIG. 7 is a flowchart showing the operation of the CPU 18.

FIG. 8 is a flowchart showing the operation of the CPU 18.

FIG. 9 is a flowchart showing the operation of the CPU 6;

FIG. 10 is a flowchart showing an operation of an interrupt routine “INT1”;

FIG. 11 is a flowchart showing an operation of an interrupt routine “INT2”.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photographing lens 2 focus detection optical system 3 area image sensor 4 sensor driver 5 A / D converter 6 CPU 7 lens ROM 8 lens drive circuit 9 motor 10 ... Photointerrupter, 11 ... Liquid crystal driver, 12 ... Liquid crystal display, 13 ... Exposure control circuit, 1
4 ... information input unit, 15 ... gaze direction detection sensor, 16 ...
Sensor driver, 17 A / D converter, 18 CP
U, 19: timer, 20: liquid crystal driver, 21: liquid crystal display unit.

Continuation of the front page (56) References JP-A-4-335605 (JP, A) JP-A-4-156788 (JP, A) JP-A-2-170275 (JP, A) JP-A-60-238975 (JP) JP-A-60-112177 (JP, A) JP-A-1-256208 (JP, A) JP-A-2-27240 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB G02B 7/28-7/40 G03B 3/00-3/12 G03B 17/18-17/20

Claims (1)

(57) [Claims] 1. A gaze direction of a photographer in a viewfinder field frame.
A visual axis detecting means for repeatedly detecting signal output in response to, fill calculating the moving average of the output signal of said visual axis detecting means
A data processing unit, based on an output of said filtering means, said viewing direction
The view frame that approximately matches the view frame is displayed in the viewfinder view frame.
The line-of- sight display means and the line-of-sight direction detected by the line-of-sight
Does not change by more than a predetermined amount compared to the detection direction of
The focus detection area is selected when the
Selecting means and an object in the focus detection area selected by the selecting means.
Focus detection means for performing focus detection, and adjusting the focus of the lens based on the output of the focus detection means.
Focusing means for performing
Focus adjustment device.