JPH04360113A - Autofocusing camera - Google Patents

Abstract

PURPOSE:To execute photographing with a small release time lag in the case of an object in a moving state and photographing with high accuracy in the case of an object in a still state, and to switch a range-finding mode in accor dance with the moving speed of the object. CONSTITUTION:In this autofocusing camera, a signal in accordance with the moving speed of the object is outputted from a moving body detection part 16 in response to the operation previous to the releasing actions of switches SW1 and SW2, whether the moving speed is higher or lower than a specified value is decided by an arithmetic control circuit 17 in response to the operation instructing the releasing actions. When the decided result shows that the moving speed is low, a distance to the object is measured by a 1st range-finding part 14, and when the decided result shows that it is high, range-finding is performed by a 2nd range-finding part 15 which finishes range-finding in a shorter time than the 1st range-finding part 14. By selecting the range-finding part, the focusing of a photographing lens is accomplished.

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 applied to an automatic focusing (AF) device for a camera that drives a photographing lens to an in-focus position based on the output of a focus detection means. It is related to the focus camera.

0002

2. Description of the Related Art When photographing a subject moving in the direction of the optical axis of a camera, there is a method for preventing defocus caused by the movement of the subject that occurs during the release time lag, as disclosed in Japanese Patent Application Laid-open No. 63-111.
No. 59817. This is designed to perform a distance measuring operation a plurality of times in response to a first release signal, predict the position of the subject at the start of exposure, and then drive the photographing lens.

[0003] In addition to the camera field, Japanese Patent Laid-Open No. 1986-
No. 2,327,571 discloses a method of projecting infrared rays onto an object to be measured and detecting the moving speed of the object based on the reflected signal.

FIG. 10 shows an example of a conventional speed detection device disclosed in Japanese Patent Application Laid-Open No. 159817/1983. In the figure, 1 is a subject, and 2 is a distance measuring optical system. This 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 optical position detecting element (PSD) 6.

[0005] Furthermore, the light emitting element driving circuit 7 has the above-mentioned IRE.
D4 is projected onto the subject 1 through the projection lens 3. The reflected light is collected by the light receiving lens 5, guided to the PSD 6, and the distance calculation circuit 8 processes the signal currents I1 and I2 output according to the incident position of the reflected signal light, thereby calculating the distance to the subject. seek. Note that this distance measuring optical system 13 will be described later.

Further, the conventional speed detecting device operates the distance measuring device as described above at predetermined time intervals according to the timing circuit 9, and stores the respective distance measurement results in the distance data storage circuit 10. Then, within a predetermined time, subject 1
Velocity is detected by calculating how much the position has been displaced. JP-A No. 63-159817 is equipped with a dedicated function determining circuit 11 in order to also determine speed changes, a distance prediction calculation circuit 12 for predicting the subject distance at the time of photographing, and a distance prediction calculation circuit 12 for controlling them. Control circuit 1
This included 3rd prize.

[0007]

[Problem to be Solved by the Invention] However, it is difficult to determine the speed by operating the distance measuring device of a general camera in two times, unless the distance measurement error is almost negligible. This is true only when the distance measurement timings are far apart. For this reason, it was difficult to say that it was very realistic.

[0008] In other words, there are always errors in actual distance measurement, and when considering the photo opportunity,
Determining speed over a long period of time is an impossible technique, even considering the purpose of moving object distance measurement.

Furthermore, in so-called active AF, which projects light and measures distance according to the reflected light, the number of times the light is projected is generally increased in order to improve the accuracy of distance measurement, and the results are averaged. Attempts have been made. However, although increasing the number of times of light projection leads to improved accuracy, there is a problem in that the distance measurement time, that is, the time lag becomes longer.

[0010] This invention was made in view of the above-mentioned problem, and when measuring the distance of a moving object using a plurality of distance measurement data, even if the distance measurement accuracy is improved by increasing the number of times of light projection, The purpose of the present invention is to provide a more practical automatic focusing camera capable of handling moving objects, capable of high-speed processing without increasing time lag.

[0011]

[Means for Solving the Problems] That is, the present invention provides a first operating means that is operated prior to the release operation, and a speed at which a signal is output in accordance with the moving speed of the subject in accordance with the operation of the first operating means. a detection means, a second operation means for instructing the release operation, and whether the movement speed outputted by the speed detection means is higher or lower than a predetermined value according to the operation of the second operation means; a 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 measuring in a shorter time than the first distance measuring means and the determination means is that the speed is low, the first distance measuring means is selected, and the first distance measuring means is selected. As a result, if the speed is high, the camera further includes a selection means for selecting the second distance measurement means, and adjusts the focus of the photographic lens using the output of the distance measurement means selected by the selection means. Features.

0012

[Operation] In 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 a signal corresponding to the moving speed of the subject is output in response to the operation instructing the release operation. It is determined whether the speed is faster or slower than a predetermined value. If the result of the above judgment is that the speed is low, the distance to the subject is measured by the first distance measuring means, and if the result of the above judgment is that the speed is high, the distance to the subject is measured by the first distance measuring means.
Distance measurement is performed by a second distance measurement means that completes distance measurement in a shorter time than the distance measurement means. Focus adjustment of the photographing lens is performed by selecting this distance measuring means.

[0013]

[Embodiment] This invention has been developed based on the fact that even if distance measurement accuracy is improved by increasing the number of light projections, the time lag has a greater effect on a moving subject. The first ranging mode has a large number of flashes, and the number of flashes is small.
It has a second distance measurement mode with less time lag, and when the subject is a moving object, focusing is performed using the second distance measurement mode to solve the above-mentioned influence. First, the influence of this time lag will be explained with reference to FIG. 2.

FIG. 2(a) shows a photograph with a composition envisioned by the photographer of the camera. Here, if the time lag until shooting is long, the subject will move while distance measurement is being performed. For this reason, as shown in FIG. 5B, an out-of-focus photograph is created due to the operation of averaging objects with different compositions and at different distances from time to time.

Therefore, in the present invention, the photographer points the camera at the subject, waits with the release button pressed halfway in the state shown in FIG. 2(c), and then presses the release button in the state shown in FIG. 2(a). By performing the action of pressing , it is detected whether or not the subject is a moving object when the release button is pressed halfway. If it is a moving object, it will be photographed in the second distance measurement mode mentioned above, so the composition will be almost the same as in Figure 2(a), as shown in Figure 2(d), and it will be extremely out of focus. It is now possible to take photos that will not turn out.

Although the distance measurement accuracy is certainly lower than that obtained by averaging the distance measurements of a stationary object many times, the distance measurement accuracy of a moving object just before it is photographed is Since the focus is adjusted using the results, there is no possibility that the image will be significantly out of focus as in the photograph shown in FIG. 2(b). Next, embodiments of the invention will be described.

FIG. 1 is a block diagram schematically showing the basic configuration of the present invention. In the figure, for the sake of simplicity, the distance measuring means having the first distance measuring mode is represented as the first distance measuring section 14, and the distance measuring means having the second distance measuring mode is represented as the second distance measuring means. It is referred to as a distance measuring section 15. The moving object detection section 16 is a means for detecting whether or not a subject (not shown) is a moving object. 17.

Further, a switch SW1, which is closed when a release button (not shown) is pressed halfway, and a switch SW2, which is closed when the release button is pressed, are connected to the CPU 17, respectively.

Now, press the release button halfway and press switch S.
When W1 is closed, the moving object detection section 16 is activated and outputs whether or not the subject is a moving object. This moving body detection section 1
6, the CPU 17 selects the first distance measuring section 14.
It is determined whether to use the second distance measuring section 15 or the second distance measuring section 15. When the subject is stationary, the first distance measuring section 14 measures the distance with high precision, although there is a long time lag, and focuses based on the result. On the other hand, when the subject is considered to be a moving object, the second distance measuring section 15 performs distance measurement with a short time lag, and focuses based on the result.

Next, referring to FIG. 3, a known single-point distance measuring device using a PSD, which is the basic structure of the present invention, will be explained. The distance measuring optical system used in this distance measuring device is
This is also the basis of active AF.

When the infrared light emitting diode (IRED) 4 projects AF light onto the subject 1 via the projection 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 becomes a function of the subject distance l, as shown in Equation 1, based on the principle of triangulation.

[0022]

[Equation 1] Here, s is the distance between principal points (baseline length) of the light emitting and receiving lenses, f is the focal length of the light receiving lens 5, and P
SD6 is placed.

The PSD 6 is a function of the incident position x of the AF signal light, and if the total signal photocurrent that outputs the two current signals I1 and I2 is IPφ, and the length of the PSD 6 is tp, then the equation 2 is obtained. , l can be found as shown in Equations 3 and 4.

[0024]

[Math 2]

[0025]

[Math 3]

[0026]

[Math 4]

Here, a is the PSD 6 from the point where a line connecting the emission center of the IRED 4 and the principal point of the light emitting lens 3 intersects the PSD 6 when a parallel line is extended from the principal point of the light receiving lens 5. This is the length to the end on the IRED4 side. In this way, the reciprocal of the subject distance is 1/
l is found.

By charging a capacitor (not shown) with a current signal proportional to I1 / (I1 + I2) of Equation 4 in synchronization with the repeated light emission of the IRED 4, the above-mentioned distance measurement results can be averaged. Processing can be easily configured using analog circuits.

[0029]Although it is generally easy to understand that moving object detection is performed by finding the amount of time change v of the object distance l, similar detection is also possible by finding the amount of time change of the reciprocal 1/l of the object distance l. It is.

FIG. 4 shows the above-mentioned first distance measurement mode and second distance measurement mode.
FIG. 2 is a block configuration diagram of a distance measuring device having three functions: distance measuring mode and moving object detection. In the figure, the PSD 6 is connected to preamplifiers 18 and 19 that absorb and amplify its output current with low input impedance. The outputs of these two preamplifiers 18 and 19 are input to the analog calculation circuit 20 for outputting a signal proportional to the reciprocal of the object distance l, as explained in Equation 4. And here, both outputs I1 and I2 of PSD6 are I1/(I
1 + I2). This analog calculation circuit 20 may use a known method of calculating the difference after logarithmic compression.

The output current of this analog arithmetic circuit 20 is:
The signal is integrated into a capacitor in the integrating circuit 21. The integration timing and direction of the integration circuit 21 are controlled in accordance with the outputs of the CPU 17 having a timing function and the direction switching circuit 22. Then, the last integration result of the predetermined sequence is sent to the CPU via the output terminal (data terminal) 23.
17.

[0032] The CPU 17 executes the IRE at a predetermined timing.
Through the D driver 24, the I
The RED 4 is driven a predetermined number of times, and the integral operation timing synchronized with the driving is inputted to the integrating circuit 21.

Further, the direction switching circuit 22 is connected to the CPU 1.
The direction of integration is switched according to the output control of step 7. According to the direction switching circuit 22, the integrating circuit 21 performs an integrating operation so that the output voltage is output from the reference level Vref in the GND direction (negative direction), and when performing an integrating operation so that the output voltage is output from the reference level Vref in the GND direction (negative direction)
It is assumed that there are two states when an integral operation is performed so that an output voltage is output from f in the radio wave voltage direction (positive direction).

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

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

FIG. 5(a) shows the IRED light emission and integration operation in the second distance measurement mode described above. In other words, here, the IRED 4 emits light only twice, and the accuracy improvement effect due to the integral operation cannot be expected much. However, the same figure (
It can be seen that, compared to distance measurement in the first distance measurement mode shown in b), the time lag is shorter as the number of times the IRED 4 emits light is smaller. The output is Va, and the CPU 17
is input.

FIG. 5(b) shows distance measurement in the first distance measurement mode. This is the same figure (a)
Compared to the IRED emission and the accompanying distance measurement results I1 /
(I1 + I2) is added six times in this example, so the CPU 17 divides this by 6 to average the distance measurement results, making it possible to obtain more reliable distance measurement results. Become. In other words, it is assumed that even if noise is superimposed on the results of one measurement, if it is random, the noise will be canceled out by averaging, and highly accurate distance measurement will be possible. The output in this case is input to the CPU 17 as Vb. FIG. 5(c) shows the waveforms of IRED driving and integration at the time of detecting the above-mentioned moving object.

The IRED 4 emits light continuously at equal intervals, and when the direction switching circuit 22 switches the direction of integration after half of the total number of times the light is emitted, an integrated waveform as shown in FIG. becomes. If the object is moving and the reciprocal 1/l of the distance l to the object changes every moment, the integrated voltage in the forward direction and the integrated voltage in the reverse direction will be different.
An output Vc is output as shown in the figure. Here, if the subject is stationary, Vc = 0, and if the subject passes the same distance, the faster the speed is, the greater Vc is. FIG. 6 is a more specific circuit configuration diagram of the distance measuring device shown in FIG. 4.

25 and 26 shown in the preamplifiers 18 and 19 amplify the output current of the PSD 6, and this amplified current flows into compression diodes 27 and 28. The compressed voltage difference resulting from this is inputted via buffers 29 and 30 to a differential arithmetic circuit composed of transistors 31 and 32 and a constant current source 33. This differential arithmetic circuit corresponds to the analog arithmetic circuit 20 that performs the arithmetic operation shown in Equation 4. If the results of amplifying the two output currents of the PSD 6 are I1 and I2, respectively, the relationships shown in Equation 5 and Equation 6 are established using the symbols shown in FIG.

[0040]

[Math 5]

[0041]

[Equation 6] Here, Is is the reverse saturation current of the compression diodes 27, 28 and transistors 31 and 32, and VT
represents the thermal voltage. Also, constant current source 3
Since the current value of 3 is Iφ, there is the relationship shown in Equation 7.

[0042]

[Math 7] Therefore, from equations 5 and 6, equation 8 holds true.

[0043]

[Equation 8] Therefore, Ia becomes the output of the analog arithmetic circuit 20 shown in FIG.

A circuit for integrating this output into 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. be. Then, the above-mentioned integration is performed by turning on the switch SW1 and turning off the switch SW2. Also, the integrating capacitor 3 is set so that the level of the data terminal 23 changes in the negative direction.
When integrating Ia into 4, the CPU 17 controls the two integral signals so that the switch SW1 is turned off and the switch SW2 is turned on.

The reset circuit 38 determines the integration level of the integrating capacitor 34 based on the reset signal output from the CPU 17. The CPU 17 also controls the IRED 4 to emit light via the driver transistor 39. In other words, when making IRED4 emit light, by controlling the integral signal in synchronization with it and turning on switch SW1 or SW2, the light is proportional to the reciprocal of the subject distance, 1/l, as shown in Equation 8 and Equation 9 from Equation 4. current Ia
is injected into the integrating capacitor 34 and integrated.

[0046]

[Equation 9] Here, the capacitance of the integrating capacitor 34 is CINT, 1
Assuming that the time of integration is tINT and the number of times of integration is n, the integrated voltage VINT is as shown in Equation 10.

[0047]

For example, as shown in FIG. 5C, when detecting a moving object, the direction is switched by the direction switching circuit 22 every three integrations, so the equation 11 is obtained.

[0048]

[Formula 11] Here, Ia1 and Ia2 are Ia corresponding to the average distance of the object 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 explained with reference to the flowchart of FIG.

In FIG. 7, first, in step S1,
It is determined whether the first release switch SW1 is turned on. Here, first release switch S
The ranging sequence does not start until W1 is turned on. However, in other embodiments, SW1 may be set at any timing prior to the release operation, and may be substituted by detecting the photographer's face with a photo reflector or the like to detect the state in which the camera is held. You can. It is also possible to add a pressure-sensitive switch to the camera grip and use it instead.

In step S1, when the first release switch SW1 is closed, the process proceeds to step S2, where the CPU 17 sets the moving object mode and starts a moving object detection operation. This moving object detection subroutine will be described later. As a result, Vc is
The signal is input to the CPU 17 by the D conversion circuit.

Next, the process advances to step S3 and waits for an input to the second release switch SW2, which is closed by the release operation. In this step S3, the motion detection operation is repeated under the control of the CPU 17 until the second release switch SW2 is closed, and Vc is updated one after another.

When the second release switch SW2 is closed in step S3, the process proceeds to step S4, where the absolute value of the moving object detection result Vc is compared with a predetermined voltage value Vx. In other words, if it is less than Vx, it is determined that the movement measure is the same as that of an almost stationary subject, and step S5
Proceed to.

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

Next, in step S7, the output result Vb
From this, the focusing distance l is determined, and step S8
Focusing operation is performed at . After this, step S
At step 9, the exposure operation begins, and the distance measuring operation and photographing of the automatic focusing camera according to the present invention are completed.

On the other hand, in step S4, if the moving object detection result Vc is equal to or greater than Vx, it is assumed that the movement measure of the object cannot be ignored, and the process proceeds to step S10. Then, in step S10, as shown in FIG. 5A, a second ranging mode is selected which sacrifices accuracy compared to the first ranging mode but has a shorter time lag. Thereby, in step S11, a distance measurement operation based on the second distance measurement mode is performed. Next, in step S12, the output result Va
Accordingly, the focusing distance l is determined, and the process proceeds to steps S8 and S9 described above, and the operation ends. FIG. 8 is a subroutine showing the motion detection operation.

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

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

Here, if the number of times of light emission is 6, that is, the number of times of light emission in the negative direction has been performed 3 times, the process advances to step A9, and as shown in FIG. 5(c), the output shown by equation 11 is The result Vc is sent as data from the output terminal 23 to the CPU.
17. Next, distance measurement operations in distance measurement mode 1 and distance measurement mode 2 will be described with reference to the subroutine of FIG.

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

In this step B5, in the case of the first ranging mode in which ranging is completed with a long time lag, step B5 is selected.
Proceed to step 6 and perform IRED 6 times by steps B3 to B6.
The light is emitted and distance measurement is completed. On the other hand, step B
In step 5, in the case of the second ranging mode in which ranging is completed with a shorter time lag, the process proceeds to step B7, and steps B3 to
The IRED emits light twice in steps B5 and B7, and distance measurement is completed.

In either case, in step B8, the output results Va and Vb are input to the CPU 17 from the data terminal 23, as shown in FIG. 5(a) or (b). This can be expressed by the same formula as VINT shown in Equation 10. Therefore, C.P.
U17 is the known n, tINT, CINT, Iφ,
The reciprocal 1/l of the subject distance l can be calculated from a, s, f, and tp. Note that the above-described sequences and calculations are performed by the CPU 17.

[0062]

As described above, according to the present invention, when measuring a moving object using a plurality of distance measurement data, even if the distance measurement accuracy is improved by increasing the number of light projections, High-speed processing is possible for the subject without long time lag,
We are able to provide a more practical autofocus camera that is compatible with moving objects, so even when shooting moving subjects, which conventional autofocus cameras are not good at, it is possible to achieve the desired composition and good focus. It is also possible to take pictures of stationary subjects with even better focus.

[Brief explanation of drawings]

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

FIG. 2 is a diagram showing a composition in which a subject is moving to be photographed by a photographer using a camera.

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

FIG. 4 is a block configuration diagram of a ranging device having three functions: a first ranging mode, a second ranging mode, and moving object detection.

[Figure 5] (a) is a timing chart of IRED light emission and integral operation in the second distance measurement mode, (b) is a timing chart of IRED light emission and integral operation in the first distance measurement mode, (c) is motion detection 2 is a timing chart of IRED light emission, direction switching, and integration.

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

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

FIG. 8 is a subroutine representing a motion detection operation.

FIG. 9 is a subroutine for explaining distance measurement operations in distance measurement mode 1 and distance measurement mode 2;

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

[Explanation of symbols]

1...Subject, 2...Distance measuring optical system, 3...Light projection lens, 4...
Infrared light emitting diode (IRED), 5... Light receiving lens, 6
... Optical position detection element (PSD), 14 ... First distance measuring section, 15
...Second distance measuring section, 16...Moving object detection section, 17...Arithmetic control circuit (CPU), 18, 19...Preamplifier, 20...Analog arithmetic circuit, 21...Integrator circuit, 22...Direction switching circuit, 23
...Output terminal (data terminal), 24...IRED driver.

Claims (1)

[Claims] 1. A first operation means operated prior to a release operation, a speed detection means for outputting a signal corresponding to a moving speed of a subject in response to the operation of the first operation means, and a speed detection means for instructing the release operation. a second operating means for controlling the subject; a first distance measuring means that measures the distance of The first distance measuring means is selected, and if the result of the above judgment is that it is high speed, the second distance measuring means is selected.
What is claimed is: 1. An automatic focusing camera comprising: selection means for selecting a distance measurement means; and the output of the distance measurement means selected by the selection means is used to adjust the focus of a photographic lens.