JP3001289B2 - Auto focus camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing camera, and more particularly to an automatic focusing camera (AF) for driving a photographing lens to a focusing position based on an output of a focus detecting means. It relates to a focus camera.

[0002]

2. Description of the Related Art When photographing a subject moving in the direction of the optical axis of a camera, a method for preventing a defocus due to the movement of the subject during a release time lag is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-1.
No. 59817. In this method, a distance measurement operation is performed a plurality of times in response to a first release signal, a position of a subject at the start of exposure is predicted, and a photographing lens is driven.

[0003] In addition to the field of cameras,
Japanese Patent No. 2327571 discloses a method of projecting infrared light on an object to be measured and detecting a moving speed of the object to be measured based on a reflected signal.

FIG. 10 shows an example of a conventional speed detector disclosed in Japanese Patent Application Laid-Open No. 63-159817. In FIG. 1, reference numeral 1 denotes a subject, and 2 denotes an optical system for distance measurement. The distance measuring optical system 2 includes a light projecting lens 3, an infrared light emitting diode (IRED) 4, a light receiving lens 5, and a light position detecting element (PSD) 6.

The light emitting element driving circuit 7 is provided with the IRE.
D4 is projected on the subject 1 through the projection lens 3. The reflected light is condensed by the light receiving lens 5, guided to the PSD 6, and the signal currents I ₁ and I ₂ output in accordance with the incident position of the reflected signal light are processed by the distance calculation circuit 8 to reach the object. Find the distance of The distance measuring optical system 13 will be described later.

Further, in the conventional speed detecting device, the above-described distance measuring device is operated at predetermined time intervals according to the timing circuit 9, and each distance measuring result is stored in the distance data storage circuit 10. Then, within a predetermined time, the subject 1
The speed is detected by calculating how much the position has been displaced. In Japanese Patent Application Laid-Open No. 63-159817, a dedicated function determination circuit 11 is provided to determine a change in speed, and a distance prediction operation circuit 12 for predicting a subject distance at the time of photographing, and controlling them. Control circuit 1
3 and so on.

[0007]

However, it is difficult to obtain the speed by operating the distance measuring device of a general camera twice in time. This is not true unless the distance measurement timing is far apart. For this reason, it was not very realistic.

[0008] That is, an error always accompanies the actual distance measurement. Considering a photo opportunity,
Obtaining the speed over a long period of time is a technique that cannot be achieved even in light of the purpose of moving object ranging.

Further, in a so-called active AF in which light is projected and the distance is measured in accordance with the reflected light, generally, the number of light projections is increased in order to increase the distance measuring accuracy, and the result is averaged. Attempts have been made. However, while increasing the number of light projections leads to an improvement in accuracy, there is a problem in that the distance measurement time, that is, the time lag is increased.

The present invention has been made in view of the above problems, and when moving object distance measurement is performed using a plurality of distance measurement data, even if the number of light projections is increased to improve the distance measurement accuracy, the moving object is not moved. It is an object of the present invention to provide a more practical automatic focusing camera that can perform high-speed processing on a subject without increasing the time lag and that is compatible with moving objects.

[0011]

That is, according to the present invention, there is provided a first operation means operated prior to a release operation, and a speed for outputting a signal corresponding to a moving speed of a subject in response to the operation of the first operation means. Detecting means, second operating means for instructing the release operation, and whether the moving speed outputted by the speed detecting means is higher or lower than a predetermined value in response to the operation of the second operating means. Determining means for determining the distance, and first distance measuring means for measuring the distance to the subject,
If the result of the determination by the second distance measuring means that completes the distance measurement in a shorter time than the first distance measuring means and the determination result by the determination means, the first distance measurement means is selected. As a result, when the speed is high, a selecting means for selecting the second distance measuring means is provided, and the focus of the photographing lens is adjusted using the output of the distance measuring means selected by the selecting means. Features.

[0012]

According to the automatic focusing camera of the present invention, a signal corresponding to the moving speed of the subject is output in response to an operation prior to the release operation, and the moving speed is adjusted in response to the operation for instructing the release operation. Is higher or lower than a predetermined value. If the result of the determination is that the speed is low, the distance to the subject is measured by the first distance measuring means. If the result of the determination is that the speed is high, the first distance is measured.
The distance is measured by the second distance measuring means which completes the distance measurement in a shorter time than the distance measuring means. The focus of the photographing lens is adjusted by selecting the distance measuring means.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made in view of the fact that the time lag has a greater effect on a moving subject even if the distance measurement accuracy is improved by increasing the number of light projections. The first distance measurement mode with many
A second distance measurement mode having a small time lag is provided, and when the subject is a moving object, focusing is performed by the second distance measurement mode to solve the above-described effect.
First, the effect of the time lag will be described with reference to FIG.

FIG. 2A shows a photograph of a composition assumed by a photographer of the camera. Here, if the time lag until shooting is long, the subject moves during the distance measurement. For this reason, as shown in FIG. 2B, an out-of-focus photograph can be obtained due to the operation of averaging subjects having different compositions and different distances every moment.

Therefore, in the present invention, the camera is pointed at the subject, and in a state shown in FIG. 2C, the release button is half-pressed to stand by, and in a state shown in FIG. Is pressed to detect whether or not the subject is a moving object in the half-pressed state of the release button.
In the case of a moving object, the photographing is performed in the above-described second ranging mode. Therefore, as shown in FIG. 2D, the composition is almost the same as that of FIG. This makes it possible to take pictures that do not become difficult.

Here, the distance measurement accuracy is inferior to that obtained by improving the reliability by averaging the distance of a stationary object many times, but the distance measurement of a moving subject immediately before shooting is performed. Since focusing is performed using the result, there is no case where the subject is not significantly focused as shown in the photograph shown in FIG. Next, an embodiment of the present invention will be described.

FIG. 1 is a block diagram schematically showing a basic configuration of the present invention. In the figure, for simplicity, the distance measuring means having the first distance measuring mode is represented as a first distance measuring unit 14, and the distance measuring means having the second distance measuring mode is represented as a second distance measuring means. The distance measuring unit 15 is used. The moving body detecting section 16 is a means for detecting whether or not a subject (not shown) is a moving body. The first distance measuring section 14, the second distance measuring section 15, and the moving body detecting section 16 include an arithmetic control circuit (CPU). 17.

A switch SW1 which is closed by half-pressing a release button (not shown) and a switch SW2 which is closed by pressing a release button are connected to the CPU 17, respectively.

Now, press the release button halfway to switch S
When W1 is closed, the moving body detection unit 16 operates to output whether or not the subject is a moving body. This moving body detection unit 1
6 according to the output result of the first distance measuring section 14
It is determined whether or not to use the second distance measuring unit 15. When the subject is stationary, the first distance measuring unit 14 measures the distance with a long time lag but with high accuracy, and performs focusing according to the result. On the other hand, when the subject is considered to be a moving object, the second distance measuring unit 15 performs distance measurement with a short time lag, and performs focusing according to the result.

Next, with reference to FIG. 3, a known one-point distance measuring device using a PSD, which is the basis of the configuration of the present invention, will be described. The optical system for distance measurement used in this distance measuring device is:
This is the basis of the active AF.

When an infrared light emitting diode (IRED) 4 projects AF light to the subject 1 via the light projecting lens 3,
The light receiving lens 5 collects the reflected light of the AF light on the subject and forms an image on the PSD 6. At this time, the incident position x of the reflected light is a function of the subject distance 1 as shown in Expression 1 based on the principle of triangulation.

[0022]

(Equation 1) Here, s is the distance (base line length) between the principal points of the light projecting and receiving lens, f is the focal length of the light receiving lens 5, and P
SD6 is arranged.

The PSD 6 is a function of the incident position x of the AF signal light. The total signal light current for outputting the _two current signals I ₁ and I ₂ is I _P φ, and the length of the PSD 6 is t _p.
Then, l is obtained as shown in Expressions 2, 3, and 4.

[0024]

(Equation 2)

[0025]

(Equation 3)

[0026]

(Equation 4)

Here, a is a distance between a line connecting the emission center of the IRED 4 and the principal point of the light projecting lens 3 and a point at which a parallel line extends from the principal point of the light receiving lens 5 and intersects the PSD 6. Is the length up to the end on the IRED4 side. As described above, the reciprocal of the subject distance 1
/ L is required.

The current signal proportional to I ₁ / (I ₁ + I ₂ ) of Equation 4 is charged in a capacitor (not shown) in synchronization with the light emission of the IRED 4 that is repeatedly emitted, thereby obtaining the above-described distance measurement result. Can be simply configured by an analog circuit.

For detecting a moving object, it is generally easy to find the time variation v of the subject distance l. However, the same detection is possible even if the time variation of the reciprocal 1 / l of the subject distance l is obtained. It is.

FIG. 4 shows the first ranging mode and the second ranging mode.
FIG. 2 is a block diagram of a distance measuring apparatus having three functions of a distance measuring mode and moving object detection. Referring to FIG. 1, PSDs 6 are connected to preamplifiers 18 and 19 for absorbing and amplifying the output current with low input impedance. This 2
The outputs of the two preamplifiers 18 and 19 are input to an analog arithmetic circuit 20 for outputting a signal proportional to the reciprocal of the subject distance l, as described in Expression 4. And
Here, both outputs I ₁ and I ₂ of PSD ₆ are I ₁ / (I ₁ +
I ₂ ). The analog arithmetic circuit 20 may use a known method of performing an arithmetic operation for taking a difference after logarithmic compression.

The output current of the analog operation circuit 20 is
It is integrated by the capacitor in the integration circuit 21. The integration timing of the integration circuit 21 is controlled in accordance with the CPU 17 having a timing function and the output of the direction switching circuit 22. Then, the final integration result of the predetermined sequence is output to the CPU via an output terminal (data terminal) 23.
Enter 17.

The CPU 17 executes IRE at a predetermined timing.
Through the D driver 24, the I
The RED 4 is driven a predetermined number of times, and the integration operation timing synchronized therewith is input to the integration circuit 21.

The direction switching circuit 22 includes a CPU 1
According to the output control of No. 7, the integration direction is switched. The integrating circuit 21 operates in accordance with the direction switching circuit 22,
The case where the integration operation is performed so that the output voltage is output from the reference level Vref in the GND direction (negative direction), and the case where the integration operation is performed so that the output voltage is output in the radio wave voltage direction (positive direction) from Vref. It has two states:

That is, by changing the integration direction between the first half and the second half of the continuous emission of the IRED 4, it is possible to determine whether or not the subject is a moving object based on the finally obtained voltage output. This is the motion detection operation.

As described above, SW1 and SW2 are a first release switch which is closed by pressing the release button halfway, and a second release switch which is closed by pressing the release button. How the light emission of the IRED and the above-described integration operation are controlled by the circuit having the above configuration will be described with reference to FIG.

FIG. 5A shows the IRED emission and the integration operation in the above-described second distance measurement mode. That is, here, the IRED 4 emits light only twice, and the effect of improving accuracy by the integration operation cannot be expected much. However, as compared with the distance measurement in the first distance measurement mode shown in FIG. 3B, it can be seen that the time lag can be shortened as the number of times of emission of the IRED 4 is smaller. Output as V _a, CPU17
Is input to

FIG. 5B shows the state of distance measurement in the first distance measurement mode. This is shown in FIG.
Compared to IRED emission and the resulting distance measurement I ₁ /
Since (I ₁ + I ₂ ) is added six times in this example, the CPU 17 divides the result by 6 to average the distance measurement results, thereby obtaining a more reliable distance measurement result. It becomes possible. In other words, it is assumed that even if noise is superimposed on the result of one time, if the noise is random, the noise is canceled out by averaging and high-accuracy distance measurement becomes possible. The output of this case, CP as V _b
It is input to U17. FIG. 5C shows the waveforms of the IRED drive and integration at the time of the above-described moving object detection.

The IRED 4 continuously emits light at equal intervals, and when the direction of the integration is switched by the direction switching circuit 22 at the time when the light emission has been completed by half of the total number of times of light emission, an integrated waveform having a form as shown in FIG. Becomes If the subject is moving and the reciprocal 1 / l of the distance l to the subject is changing every moment, the integral voltage in the forward direction and the integral voltage in the reverse direction are different,
The output _Vc is output as shown in FIG. Here, if the subject is stationary, V _c = 0, and if the subject passes through the same distance, the higher the speed, the higher the V _c . FIG.
FIG. 5 is a more specific circuit configuration diagram of the distance measuring device shown in FIG. 4.

Reference numerals 25 and 26 in the preamplifiers 18 and 19 amplify the output current of the PSD 6, and the amplified current is supplied to the compression diodes 27 and 28.
Flow into Then, the resulting compressed voltage difference is input to the differential operation circuit composed of the transistors 31 and 32 and the constant current source 33 via the buffers 29 and 30.
This differential operation circuit corresponds to the analog operation circuit 20 that performs the operation shown in Expression 4. Assuming that the results of amplifying the two output currents of the PSD 6 are I ₁ and I ₂ , respectively, FIG.
The relations of Equations 5 and 6 are established by the symbols shown therein.

[0040]

(Equation 5)

[0041]

(Equation 6) Here I _s, the compression diodes 27, 28 and transistors 31 and 32, a reverse saturation current, V _T represents the thermal voltage. Further, since the current value of the constant current source 33 is Iφ, there is a relationship represented by Expression 7.

[0042]

(Equation 7) Therefore, Expression 8 is established from Expression 5 and Expression 6.

[0043]

(Equation 8) Therefore, _Ia is the output of the analog operation circuit 20 shown in FIG.

A circuit for integrating this output to the integrating capacitor 34 in the integrating circuit 21 so that the level of the data terminal 23 changes in the positive direction is a current mirror circuit composed of transistors 36 and 37. is there. When the switch SW1 is turned on and the switch SW2 is turned off, the above-described integration is performed. When integrating _Ia into the integrating capacitor 34 so that the level of the data terminal 23 changes in the negative direction, the CPU 17 controls the two integrated signals so that the switch SW1 is turned off and the switch SW2 is turned on. I do.

The reset circuit 38 determines the level via the integration of the integrating capacitor 34 based on the reset signal output from the CPU 17. The CPU 17 also controls the light emission of the IRED 4 via the driver transistor 39. That is, when the IRED 4 is caused to emit light, the integral signal is controlled in synchronization therewith, and the switch SW1 or SW2 is turned on, so that the proportionality to the reciprocal 1 / l of the subject distance is obtained as shown in Equations 8 and 4 and Equation 9. Current I
_a is poured into the integration capacitor 34 and integrated.

[0046]

(Equation 9) Here, assuming that the capacity of the integrating capacitor 34 is C _INT , one integration time is t _INT , and the number of integrations is n, the integration voltage V
_INT is as shown in _Expression 10.

[0047]

(Equation 10) For example, as shown in FIG. 5C, when a moving object is detected, the direction is switched by the direction switching circuit 22 every three integrations, and therefore, Expression 11 is obtained.

[0048]

[Equation 11] Here, I _a1 and I _a2 are I _a corresponding to the average distance of the subject in the first half and the second half of the integration. Next, the operation of the automatic focusing camera of the present invention will be described with reference to the flowchart of FIG.

In FIG. 7, first, in step S1,
It is determined whether the first release switch SW1 has been turned on. Here, the first release switch S
The distance measurement sequence does not start until W1 is turned on. However, in another embodiment, the SW1 may be at a timing prior to the release operation, and may be substituted by detecting the photographer's face with a photo reflector or the like and detecting the state of holding the camera. You may. It is also possible to provide a pressure-sensitive switch on the grip of the camera and use it as a substitute.

In step S1, when the first release switch SW1 is closed, the process proceeds to step S2, in which the CPU 17 sets the moving body mode and starts the moving body detecting operation. This moving object detection subroutine will be described later. As a result, V _c is, A / D to built CPU17
The data is input to the CPU 17 by the conversion circuit.

Next, the process proceeds to step S3, and waits for an input of a second release switch SW2 to be closed by the release operation. In step S3, until the second release switch SW2 is closed, motion detection operation is repeated by the control of the CPU 17, V _c is successively updated.

[0052] When the second release switch SW2 is closed in step S3, the process proceeds to step S4, the absolute value of the moving object detection result V _c with a predetermined voltage value V _x is compared. That is, if V _x or less, it is determined that it is moved measure unchanged the subject being almost stationary, the process proceeds to step S5.

In step S5, as shown in FIG. 5 (b), the first ranging mode in which the time lag is longer than that of the second ranging mode but a highly accurate ranging operation is selected, and in step S6, Distance measurement based on the first distance measurement mode is performed. The distance measurement subroutine will be described later.

Next, in step S7, the output result V _b
Thus, the focusing distance 1 is obtained, and the focusing operation is performed in step S8. Thereafter, step S9
Then, the exposure operation is started, and the distance measuring operation and photographing of the automatic focusing camera according to the present invention are completed.

On the other hand, in the step S4, if the moving object detection result V _c is V _x or more, assuming that the mobile measure a subject can not be ignored, the process proceeds to step S10. Then, in step S10, as shown in FIG. 5A, the second ranging mode having a shorter time lag but less accurate than the first ranging mode is selected. Thus, in step S11, a distance measurement operation based on the second distance measurement mode is performed. Then, at step S12, the output result V _a, focusing distance l is determined, step S8 described above, and ends the operation proceeds to step S9. FIG.
This is a subroutine representing an operation of moving object detection.

In step A1, the first release switch SW1 and the second release switch SW2 are turned off, and the integrating capacitor is initialized. Next, in step A2, the number of times of light emission of the IRED is reset. Then, in step A3, the IRED emits light and the first release switch SW1 is turned on.
Then, in step A4, the number of times of emission of the IRED is added, and in step A5, the number of times of emission is determined. In step A5, the process proceeds to step A6 until n = 3, that is, when the above-described integration in the positive direction is performed three times.

In step A6, similarly to step A3, the IRED emits light and the second release switch SW2 is turned on. Then, the number of times of light emission is added in step A7, and the number of times of light emission is determined in step A8.

Here, if the number of times of light emission is six, that is, if the number of times of light emission in the negative direction is three, the process proceeds to step A9, and as shown in FIG. The result _Vc is output from the output terminal 23 to the CPU 1 as data.
7 is input. Next, the ranging operation in the ranging mode 1 and the ranging mode 2 will be described with reference to the subroutine of FIG.

In step B1, the first release switch SW1 and the second release switch SW2 are turned off, and the integrating capacitor is initialized. Next, in step B2, the number of times of light emission of the IRED is reset. Thereafter, in step A3, only the second release switch SW2 is turned on in synchronization with the emission of the IRED. Then, in step A4, the number of times of emission of the IRED is added, and in step A5, the distance measurement mode is determined.

In step B5, in the case of the first ranging mode in which ranging is completed with a long time lag, step B
6 and six IREDs are performed in steps B3 to B6.
Is emitted, and the distance measurement ends. On the other hand, step B
In the case of the second ranging mode in which the ranging is completed with a shorter time lag in Step 5, the process proceeds to Step B7, and Steps B3 to B3 are performed.
Light emission of the IRED is performed twice by B5 and step B7, and the distance measurement is completed.

[0061] Then, in either case, in step B8, as shown in FIGS. 5 (a) or (b), the output V _a, V _b is input from the data terminal 23 to the CPU 17. This can be expressed by the same formula as V _INT shown in Expression 10. Therefore, the CPU 17
Are known n, t _INT , C _INT , Iφ, a, s, f, t
_{From p} , the reciprocal 1 / l of the subject distance l can be calculated. Note that the above-described sequence and calculation are performed by the CPU 17.

[0062]

As described above, according to the present invention, when moving object distance measurement is performed using a plurality of distance measurement data, even if the number of light projections is increased to improve the distance measurement accuracy, the moving object distance can be improved. For the subject, high-speed processing is possible without a long time lag,
A more practical autofocus camera that supports moving objects can be provided, so even for moving subjects that are not good at conventional autofocus cameras, the composition and focus Can be taken, and a still subject can be photographed with better focus.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a basic configuration of an automatic focusing camera of the present invention.

FIG. 2 is a diagram showing a composition in a state in which a subject is moving so that a photographer of the camera takes a picture.

FIG. 3 is a diagram showing a known one-point distance measuring device using a PSD, which is a basic configuration of the automatic focusing camera of the present invention.

FIG. 4 is a block diagram of a distance measuring apparatus having three functions of a first distance measuring mode, a second distance measuring mode, and moving object detection.

5A is a timing chart of an IRED emission and integration operation in a second ranging mode, FIG. 5B is a timing chart of an IRED emission and integration operation in a first ranging mode, and FIG. 6 is a timing chart of IRED light emission, direction switching, and integration at the time.

6 is a more specific circuit configuration diagram of the distance measuring device of FIG. 4;

FIG. 7 is a flowchart illustrating the operation of the automatic focusing camera of the present invention.

FIG. 8 is a subroutine showing an operation of moving object detection.

FIG. 9 is a subroutine for explaining a ranging operation in a ranging mode 1 and a ranging mode 2;

FIG. 10 is a block diagram showing an example of a conventional speed detecting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Subject, 2 ... Distance measuring optical system, 3 ... Projection lens, 4 ...
Infrared light emitting diode (IRED), 5 ... light receiving lens, 6
... Optical position detection element (PSD),.
... second distance measuring section, 16 ... moving object detecting section, 17 ... arithmetic control circuit (CPU), 18, 19 ... preamplifier, 20 ... analog arithmetic circuit, 21 ... integrating circuit, 22 ... direction switching circuit, 23
... output terminal (data terminal), 24 ... IRED driver.

Claims (1)

(57) [Claims] A first operation performed prior to a release operation;
Operating means, speed detecting means for outputting a signal corresponding to the moving speed of the subject in response to operation of the first operating means, second operating means for instructing the release operation, and operation of the second operating means A determining means for determining whether the moving speed outputted by the speed detecting means is higher or lower than a predetermined value; a first distance measuring means for measuring a distance to a subject; If the result of the determination by the second distance measuring means that completes the distance measurement in a shorter time than the distance measuring means and the determination result by the determination means is low, the first distance measurement means is selected. , The second
An automatic focusing camera, comprising: a selection unit for selecting a distance measuring unit, wherein the output of the distance measuring unit selected by the selection unit is used to adjust the focus of the photographing lens.