JP3194755B2 - Distance measuring device - 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 device for a camera.

[0002]

2. Description of the Related Art In the flow of camera automation, there has been a demand for the development of a focusing technique for a subject which is difficult to focus on a camera, particularly for a subject located outside the center of a screen or a moving subject.

Conventionally, such a subject has been designed to prevent out-of-focus. 1. Multi-AF technology for measuring a plurality of points in a screen; There is a moving object ranging technique for calculating the speed of a subject in accordance with a plurality of distance measurement results obtained by shifting the distance to thereby prevent a defocus due to a subject moving during a release time lag.

[0004]

However, the above-mentioned 2)
Both technologies have the disadvantage that the time required for ranging is longer,
For (1), as the number of ranging points increases, the time required for ranging increases, and for (2), as described above, it is necessary to shift the time and measure the distance many times. Is sacrificed. That is,
There was a problem in that simply combining these techniques did not provide sufficient photo opportunities.

The distance measuring apparatus of the present invention has been made in view of such a problem, and its object is to perform the above two time-consuming distance measuring techniques at the same time.
An object of the present invention is to provide a distance measuring device capable of reducing the time lag.

[0006]

In order to solve the above-mentioned problems, a distance measuring apparatus according to the present invention comprises a first light beam directed to a central portion of a photographing screen and a second light beam directed to a peripheral portion of the photographing screen. Respectively, a first light receiving element for receiving the reflected light of the first light flux from the subject, and a second light receiving element for receiving the reflected light of the second light flux from the subject. A distance measuring means for detecting and outputting, in a time division manner, a central distance measuring value at a central portion of the photographing screen and a peripheral distance measuring value at a peripheral portion from the light receiving position of the reflected light; Speed detecting means for obtaining the moving speed of the subject based on the output of the first light receiving element for receiving the first light beam continuously emitted, and output from the speed detecting means when the central distance measurement value is closer to a predetermined value. The moving object is predicted using the above moving speed, and the center distance measurement value is predetermined. ; And a distance determination means for determining the object distance based on the center distance value or near distance value outputted from said distance measuring means when more distant.

[0007]

According to the present invention, the distance measurement outputs of the central and peripheral objects are respectively integrated in a time-division manner to obtain voltages corresponding to the respective distances, and the central distance measurement output is positively and negatively parallel to this integration operation. To obtain a voltage corresponding to the moving speed. If the center distance value is equal to or smaller than a predetermined value, the moving object distance measurement output is selected. Otherwise, the closest distance value among the center, left, and right is selected.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in the present invention, it is assumed that when photographing a moving object, the photographer will put the moving object in the center of the screen including the object. Is assumed.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a center distance measuring means for measuring a distance to a subject located at the center of a picture screen, and 2 denotes a subject located at the left, right, or upper and lower points thereof. This is a peripheral distance measuring means for distance measurement. By sequentially turning on / off the switches (SW) 3 and 4, the outputs of the central distance measuring means 1 and the peripheral distance measuring means 2 are time-divisionally output to the first.
Input to the integration means 5.

The calculating means 6 sequentially reads the output of the first integrating means 5 and calculates the distance of each point.

On the other hand, while the above sequence is being performed, the output of the center distance measuring means 1 is input to the second integrating means 7 whose integration direction can be switched according to the output of the direction switching circuit 8, and the final The speed is detected from the output result of.

The above sequence is shown in FIG. 2. The distance measurement at the center, left, and right is sequentially performed, and during that time, speed detection is simultaneously performed.

The state of the speed detection is shown as an output of the second integration means 7. When the subject is approaching the camera, the integration result of the first half distance measurement result is large because the subject distance is long, and after switching the integration direction, the integration result of the second half distance measurement result is close to the subject distance. So it gets smaller,
The difference V ₀ is output in a relationship depending on the moving speed V of the subject.

When the center subject is stationary, V ₀ becomes 0, and the closest one of the center, left, and right distance measurement results l _C , l _L , and l _R may be selected as the main subject. .
This selection is made by the calculating means 6. Further, when the central subject is a moving object, the speed of the moving object is obtained from the calculation means 6 from V _0, and if a time lag t ₀ until the start of exposure is taken into account, from the formula of l = l _C −V · t ₀ , The operation of 1 is performed by the arithmetic means 6 so that the distance of 1 is in focus.

FIG. 3 is a diagram showing the configuration of a second embodiment of the present invention.

In this embodiment, an AF signal light from an infrared light emitting diode (hereinafter referred to as IRED) 11 is projected via a light projecting lens 12, and reflected light from the subject is reflected by a light receiving lens 13. Through the light position detecting element (hereinafter, referred to as
A known active triangulation method is used in which light is received by a PSD 14 and the distance is determined according to the incident position.

However, IRED11 and PSD14 are
It is divided into three parts to measure the distance to the left and right, as well as the center, and these are shown as S, L, and R, respectively.

That is, the AF light projected from the L of the IRED 11 is projected at a certain angle θ from the optical axis of the projection / reception lens and the photographic lens (not shown) as indicated by l _L1. Is done. If there is a subject at the light projection position, the light enters the light receiving lens 13 through an optical path of l _L2 .

The angle of incidence of l _L2 has an inclination depending on the subject distance with respect to the direction connecting the principal points of the light emitting and receiving lenses (base length direction). Therefore, the position of the signal light spot incident on the PSD 14 depends on the subject distance.
The position is different in the base line length direction of the PSD 14.

That is, by detecting the incident position of the signal light on the PSD 14, the subject distance can be obtained.

The PSD 14 is an element that outputs the light incident position in the form of two output currents. When the signal light is incident on the center of the PSD 14 in the longitudinal direction (vertical direction in the drawing), the PSD 14
The ratio of the two current signals of D14 is 1: 1. Also, PS
When the signal light is incident on a point internally divided in the length direction of D14 at 3: 1, the current signal ratio becomes 3: 1.

In this embodiment, the calculation of this ratio is performed using a known compression / expansion circuit in analog circuit technology. FIG. 4 shows a specific configuration example of the compression / decompression circuit.

First, assuming that currents obtained by amplifying the two signals of the PSD 14 are I ₁ and I ₂ , the compression diodes 40 and 4 are used.
1 are: V ₁ = V _T · ln (I ₁ / I _S ), V ₂ = V _T · ln
(I ₂ / I _S ).

Here, I _S : reverse saturation current of the diode, V _T : thermal voltage, and _VA and V _{B in} the figure after passing through the buffers 42 and 43.
Differences, since the emitter of the transistor 44 and 45 is _{common, V 1 -V 2 = V T} · ln (I 1 / I 2) = V B -V A = V T · ln and (I _OUT / I _X) of Become.

Therefore, I ₁ / I ₂ = I _OUT / I _X ∴I _X = I _OUT (I ₂ / I ₁ ) On the other hand, from I _OUT + I _X = Iφ, I _OUT + I _OUT (I ₂ / I ₁ ) = Iφ I _OUT ｛(I ₁ + I ₂ ) / I ₁ ｝ = Iφ ＩI _OUT = Iφ · I ₁ / (I ₁ + I ₂ ) where Iφ is the current flowing from the current source 46 and _IX is the diode 47, the I _{OU T} is the current flowing in the collector of the transistor 45.

[0028] Here, I ₁ + I ₂ is proportional to the total photocurrent entering the PSD 14, I _{OU T} is not related to the reflectance of the subject, the current signal depending only on the object distance.

The compression, decompression and integration circuits from the compression circuits 19, 20, 21 and 22 of FIG. 3 to the expansion and integration circuits 29 and 30 via the buffers 23, 24, 25, 26, 27 and 28 are as follows. With this configuration, the current source 46 in FIG. 4 is turned on / off in synchronization with the light emission of the IRED 11.
By charging I _OUT to the integration C52, an integration effect can be obtained.

FIG. 5 is a timing chart for explaining the light emission and integration operation of the IRED 11.

In the figure, the IRED 11 S emits light 12 times, and as shown in the figure, from the 41 st light emission to the 80 th light emission, the IRED 11 L emits from the 81 st light emission,
Until the 120th light emission, the IRED 11 R emits light at the same time. Further, as described above, the object of the present invention is to simultaneously perform the multi-AF for preventing the focus of a photograph from being out of focus and the operation AF for following a moving subject, so that it is synchronized with the above-mentioned IRED11 L and IRED11 R. Then, distance measurement is performed on the screen, left and right, respectively. R and L emission are 4
This is performed 0 times at a time, in order to improve the accuracy by integrating the result by an integrating circuit and performing an averaging process. The center distance measurement is performed by the first 40 light emission of the IRED 11. In addition, moving object ranging is a technique for determining the amount of change in the position of a subject, and therefore requires higher precision than ordinary ranging. Therefore, in this embodiment, 12
The number of times of light emission of 0 enhances the effect of averaging, and as described above, when the moving object is detected over a long period of time, the amount of change in the position of the subject is large, and the detection is easy. In this configuration, the direction of the integration operation in the first half and the latter half of the continuous emission of 120 times of the IRED 11 S is changed to obtain the speed information from the final output of the integration result, thereby improving the accuracy of moving object ranging.

Returning to FIG. 3, the operation of each component will be described sequentially.
After the expansion and integration circuits 29 and 31 are initialized,
The IRED 11 S emits light via the driver 35. The light beam of the IRED 11 S is projected on the subject as l _S1 via the lens 12, and the reflected light is incident on the PSD 14 S via the light receiving lens 13 via the path of l _S2 . As described above, the position of the reflected signal light on the PSD 14 is a function of the position of the subject, and the distance measurement is performed by calculating the ratio of the output of the PSD 14.

The two output signals of the PSD 14 S are amplified by preamplifiers 15 and 16, and are compressed by compression circuits 19 and 2.
After being compressed by 0, it is input to the expansion / integration circuits 29 and 31 via the buffers 23, 24, 25 and 26.

First, as shown in the timing chart of FIG. 5, since the distance measurement at the center is performed, the decoder 34 turns off the buffers 27 and 28 and turns off the buffers 23, 24, 25 and 26 by the instruction of the CPU 106. Activate the buffer.

The extension / integration circuit 29 is for left, right, and center distance measurement, and 31 is for moving object detection.

Therefore, after the IRED 11 S emits light 40 times, the center distance measurement result is output to the output terminal 30. The CPU 106 converts the result into an analog-to-digital (A / D) signal, reads the result, and reads the center distance measurement result. Ends. Also, IRED11 S
From the 41st light emission, the reset circuit 36 initializes the expansion / integration circuit 29 again, and the light emission of the IRED 11L starts. At this time, the decoder 34 turns off the buffers 23 and 25 and puts the buffers 24, 26, 27 and 28 into an operating state, so that the outputs of the PSDs 14 L and R are
And compressed by the compression circuits 21 and 22.

Since the IRED 11 R does not actually emit light, the subject on the left side of the screen is measured by the output of the PSD 14 L.

When the IRED 11L emits light 40 times, the distance measurement result on the left side of the output terminal 30 is input to the CPU 106 in the same manner as in the center distance measurement. During this time, IRED1
1S continues to emit light, and the extension / integration circuit 31 keeps integrating the moving object distance measurement result. However, IRED11
When the 60th light emission of S is completed, the direction switching circuit 3
The output of 3 and the CHANGE signal are inverted to change the direction of integration.

More specifically, the switching of SWs 48 and 51 in FIG. 4 is performed. When the CHANGE signal is L, SW5
1 turns on and the integral C52 flows out of I _OUT ,
The output 55 is integrated in a lower direction. Next, CHAN
When the GE signal becomes H, SW51 is turned off and 48 is turned on.
Then, through the current mirror circuits 49 and 50, the integration C52
Is integrated in the positive direction.

Next, after the integration circuit 29 is initialized, the IR
The emission of ED11R is started.
11S continues to emit light, and the integration operation for the operation distance measurement is continuously performed according to the distance measurement results of the central IRED 11 and PSD 14.

The decoder 34 has buffers 24, 26, 2
7 and 28 are selected, and the distance measurement result on the right side is output to the output terminal 30.

When the light emission of the IRED 11 S is completed 120 times, the light emission of the IRED 11 R is also stopped.
6 reads the distance measurement result on the right side from the output terminal 30,
The moving object distance measurement result of the center subject is subsequently read from the output terminal 32.

[0043] Since the moving object distance measurement result V ₀ which this embodiment is a function of the distance and speed, the center of the distance measurement results l _c and V _0, the object distance l _P in the exposure timing is determined.

Table 1 shows the distance measuring points,
The IRED 11 and the buffer used in the case of left, right, and center are shown.

[0045]

[Table 1] FIG. 6 shows an example of a flowchart for determining the distance for focusing after the distance measurement is completed.

After the distance measuring operation described with reference to FIG.
PU106 determines whether the center of the distance measurement results l _C is far or closer than the predetermined distance l _a. If the distance is longer than _a certain distance la, it is not necessary to reflect the moving object distance measurement result due to the depth of the subject of the photographing lens, and it is highly likely that the hollow phenomenon has occurred.

Then, at that time, the left and right distance measuring distances l _L ,
Focusing is performed with the closest one of l _R as the main subject. Further, l _C is the Motion measurement result V ₀ at l _a以近, if within a certain range, so as to focus to l _C since no particular correction of the moving body is required. And
l _C only when l _C is closer to l _R and V ₀ is greater than V _R
, V ₀ and the release time lag t _0, a distance prediction calculation at the time of exposure is performed, and focusing is performed on that distance.

[0048]

As described in detail above, according to the present invention,
Even if the subject is not located at the center of the screen or even if it is a moving object, it is possible to provide a distance measuring device that does not become out of focus and has a short time lag and is strong against a photo opportunity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a distance measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a time chart showing a sequence for executing the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a distance measuring apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a specific configuration of a compression / expansion circuit.

FIG. 5 is a timing chart for explaining IRED light emission and integration operation.

FIG. 6 is a flowchart for determining a distance at which focusing is to be performed after distance measurement is completed.

[Explanation of symbols]

1. Central distance measuring means, 2. Peripheral distance measuring means, 3. Switch,
4 switch, 5 first integration means, 6 arithmetic means, 7
Second integration means, 8 ... direction switching circuit.

Claims (1)

(57) [Claims] 1. A light projecting means for projecting a first light beam toward a central portion of a photographing screen and a second light beam toward a peripheral portion of the photographing screen, respectively, and reflected light of the first light beam from the subject. And a second light receiving element for receiving reflected light of the second light flux from the subject, and a central ranging value at a central portion of the shooting screen from a light receiving position of the reflected light. A distance measuring means for detecting and outputting a peripheral distance measurement value of the peripheral part in a time-division manner; and a subject based on an output of a first light receiving element for receiving a first light beam continuously emitted during operation of the distance measuring means. Speed detecting means for determining the moving speed of the moving object; and a moving object prediction using the moving speed output from the speed detecting means when the center distance value is closer than a predetermined value. When the distance is far, the center ranging value output from the ranging means is also Ku distance measuring apparatus characterized by comprising a distance determining means for determining the object distance on the basis of the peripheral distance measurement value.