JPS62201308A - distance measuring device - Google Patents

Abstract

PURPOSE:To speed up the selection of the presence position of an object and the arithmetic of distance information by automatically switching to projecting means which projects light on the peripheral region of the object unless the level of reflected light from the central part fails to reach a specified value in the 1st integrating operation. CONSTITUTION:Light emitting elements IRs, and IRw1 and IRw2 project light upon the center part Obs and peripheral parts Ob1 and Ob2 on the reflecting surface Ob of the object respectively and light receiving elements SPC1 and SPC2 which are arranged at an interval of specific base line length (l) receive reflected light from them. When the center part Obs on the object reflecting surface Ob is at finite distance, the distance is measured by the element IRs and a camera is put in focus on according to the distance. When the center part Obs is at extremely long distance, on the other hand, the level of its reflected light is low and the rise level of an integrator output is small, so that it is judged that the distance of the center part Obs to the object is infinite. For the purpose, the elements IRw1 and IRw2 for the peripheral parts Ob1 and Ob2 are switched to perform rise integration and fall integration again, and thus the distance of the peripheral parts Ob1 and Ob2 to the object is measured, so that the camera is put in focus based on the distance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an active distance detection device that projects a distance measurement object with light and detects the object distance from the light receiving position where the reflected light is received by a light receiving element. The present invention relates to a distance measuring device that can be switched.

With conventional cameras equipped with automatic focus adjustment devices, the distance measuring part of the subject is located in the center of the viewfinder field of view, so the photographer must compose the shot so that the subject is placed in the center of the shooting screen. I had to. Another drawback is that when shooting multiple people side by side or when placing the main subject at the edge of the screen, the 411 distance part of the subject disappears into the background, making it impossible to focus on the main subject. occurred.

On the other hand, if the subject you want to photograph is
There is a way to recompose and take a picture after taking X11 distance with all parts covered, but this method uses the camera's automatic point 4.
It is very difficult for photographers who do not fully understand the j adjustment mechanism to operate it, and its operation is troublesome.

To solve this problem, multiple parts of the shooting screen can be
There is a method that determines the focus of the camera by evaluating the distance data obtained from the distance measurement, but this method requires multiple signal processing circuits to measure the distance on multiple parts of both sides, and vice versa. When the processing circuit is shared, there is a drawback that distance measurement has to be carried out on multiple parts of the screen in a time-division manner, which increases the distance measurement time.

Furthermore, as shown in the specification of Japanese Patent Application No. 152297/1989 filed by the present applicant, the distance measuring field is divided into two, a narrow field of view and a wide field of view, and it is possible to determine whether the distance measurement information in the narrow field is infinite or not. Detects,
A distance measurement device that can automatically select distance measurement information on the distance measurement field side has been proposed. This method has the disadvantage that it takes a long time to output the distance signal because the distance information is calculated twice to produce the All+distance result.

The present invention has been made in order to solve the L-stated problem, and includes a plurality of light projecting means for projecting light onto the central and peripheral parts of the photographic field of view, and a light receiving means that receives reflected light from the projected light. When calculating the subject distance by integrating the output twice,
If the level of the light reflected from the central part does not reach a predetermined value in the first integral operation, the light projecting means is automatically switched to a side that projects light to the peripheral part of the subject, and the first integral action is performed again. By calculating the distance information using the camera, it is possible to determine in a short time whether the object within the photographic field of view is in the center or in the periphery, thereby shortening the calculation of the object distance information. be.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a diagram for explaining the principle of the distance measuring device of the present invention.
FIG. 2 is a plan view of the light receiving element shown in FIG.

In FIGS. 1 and 2, IRED is a light projecting element that emits linear infrared light to objects Obl, 0 through a projecting lens Ll.
b2h4. : Project. L2 is the object O to be distanced
Two light receiving elements 5PCI that receive the reflected light from bl and Ob2 at a predetermined distance (hereinafter referred to as base line length) from the light emitting axis.

This is a light receiving lens that forms an image on 5PC2. Light receiving element S
The image RI formed by the reflected light from the objects PC1 and PC2 moves continuously along the direction (hereinafter) perpendicular to the light projection axis (line length direction) Ql depending on the distance from the object. Here, the structure of the light receiving elements 5PCI and 5PC2 is the second one.
Since the model is as shown in the figure, the output of the element corresponds to a change in the distance to the object to be measured, and if the output of one of the light receiving elements increases, the output of the other light receiving element decreases. Light receiving element 5PC
I, 5If the outputs of PC2 are A and B, respectively, (A
+B) normalized by e.g. A/(AlB)
The signal indicates the position of the distance-measuring object, and an autofocus device is realized by controlling the movement jt (lens extension) of the photographing lens using the output of the device.

FIG. 3 is a schematic diagram of a distance measuring device applied to the present invention. In FIG. , IRW2 are light-emitting elements for projecting light onto the peripheral parts ob1 and Ob2 on the reflective surface ob of the object, and from the reflective surfaces Obs, Obl, Ob2 to c7
) Each reflected light passes through the light receiving lens L2 to the light receiving element 5PCI.
, 5 When the light is received by PC2, ]-reflecting surfaces Obl, Ob
The reflected light from 2 is received by the light-receiving element described above via reflection mirrors M1 and M2.

Next, a control circuit of the present invention using the configuration shown in FIG. 3 will be explained with reference to FIG. 4.

In FIG. 4, PU is a power supply circuit, C0NT is a logic circuit that controls signals, and IRS is a light projecting element that projects light onto a subject at the center of the photographic field of view.

IRwl and IRw2 are light projecting elements that project light onto the subject in the peripheral part of the photographic field of view, and DRs and DRl.

DR2 is a drive circuit for the light projecting element, and receives signals I RED s and I RED from the logic circuit C0NT.
Controlled by n. Ls is a release button of the camera. 5PCI and 5PC2 are the light receiving elements shown in FIGS. 1 to 3, and AI is a high input impedance amplifier that converts the output current of the light receiving elements 5PCI and 5PC2 into voltage, and is composed of resistors R1, R2, R3 and capacitor C1. This is a filter that suppresses the DC suppressor section using a negative feedback circuit. ASl is an analog switch that is turned on and off by signal Sl.

Capacitor C2 and resistor R4 are a bypass filter, resistors R5 and R6, amplifier A2 is a preamplifier that amplifies the output of the bypass filter, amplifier A3 and resistor R7,
R8 has a gain of 11 times and constitutes an inverter that inverts the output signal of the preamplifier A2.

MINT amplifier A4. An integrator, AS2. AS3゜AS4 are each No. 43 S2
．． S3. Analog switch R9, which is turned on and off by S4, is a resistor connected to the inverting input terminal of integrator A4. CPl, CF2 are comparators, R11°R1
2, R13 is a voltage dividing resistor that supplies the base voltage to each of the comparators CPI and CP2, and is connected in series with W. One end of resistor R11 is grounded, and one end of resistor R13 is connected to a 1-volt power supply. be done.

Next, the operation of the distance measuring device in the E-class configuration will be explained using the timing charts of FIGS. 1 to 3 and FIGS. 5 and 6.

In FIG. 5, first, at time 10, when the release button LS of the camera is pressed, the signal S4 output from the logic circuit C0NT becomes high level, and the analog 5WAS4 is turned on. As a result, amplifier A4 → comparator C
A closed circuit consisting of P2→analog 5WAS4→resistance RIO-resistance R9 is formed. At this time, for example, amplifier A
When the potential at the output terminal of the analog AS4. Since the capacitor C3 is charged via the resistors RIO and R9, the voltage at the output terminal of the amplifier A4 gradually drops in accordance with the charging voltage of the capacitor C3, and after a predetermined time, the potential at the inverting input terminal of the amplifier A4 and the voltage at the comparator CP2 are lowered. When the potential at the output end becomes the same potential, the capacitor C3 stops charging operation.

On the other hand, the potential at the output terminal of amplifier A4 is
When the potential of the inverting input terminal of the amplifier A4 is lower than the potential of the inverting input terminal of the amplifier A4, the charge of the capacitor C3 is discharged by the operation opposite to the above, and when the potential of the inverting input terminal of the amplifier A4 and the output terminal of the comparator CP2 become the same potential, the capacitor C3 is discharged. stops and enters a stable state.

By the above operation 1-, the Miller integrator iNT consisting of the capacitor C3 and the amplifier A4 is initialized during the period of 1 time to-t2.

Next, during the period from time t1 to time t2, the signal iREDS repeats high and low levels to cause the IRS to pre-emit light, and the light emitting element reaches a thermal equilibrium state IE.

Then, at time t2, the analog switch AS4 opens, the closed circuit consisting of the amplifier A4, the comparator cP2, the analog switch AS4, the resistor R10, and the resistor R9 opens, and the mirror integrator INT starts an integration operation. Note that at this point, the signal Sl from the logic circuit C0NT
is at a low level and the analog switch AS1 is OFF, so only the light receiving element 5PC2 is connected to the input terminal of the amplifier A1.

Next, during the period from time t2 to t3, the analog switch AS2
is when the light emitting element IRS is ON.

Also, the analog switch AS3 turns off the light emitting element IRS.
so that they are each turned on at the time of .

Control signal S2. Controlled by S3, 0N with opposite phases to each other
-Turn off. When the analog switch AS2 is ON, the light from the light emitting device IR5 reflected by the object is integrated by the mirror integrator INT as an output voltage corresponding to the intensity of incidence on the light receiving element 5PC2. Furthermore, when the analog switch AS3 is ON, the light emitting element IR5 is OFF, so the output corresponding to external light other than the signal light is integrated by the integrator INT as an inverted signal from the amplifier A3, canceling the influence of external light. be done.

In this way, the capacitor C3 is charged for a certain period (TA) from t2 to t3, and its terminal voltage has the waveform iNT shown in FIG.
As shown in , the level increases depending on the amount of light incident on the light receiving element 5PC2.

At this time, if the object at the center of the screen onto which the light projecting element IRS projects light is at a finite distance, the integrator output iNT increases, although it also depends on the reflectance of the object. On the other hand, when the subject is extremely far away, L'A and the output of the integral Ag i N T become extremely small.

The voltage level for determining whether the distance of the subject is infinite or finite is determined by resistors R11, RL2. If set by R13 and inputted to the inverting input terminal of the comparator CPI, the output of the comparator CPI will be outputted as a low level signal S5 when the integrator output iNT exceeds the previous level.

By latching this low level signal S5 at time L3, it is determined whether the subject at the center is at a finite distance.

Now, when the object at the center of the screen is at a finite distance, the light projecting element IR5 sends a signal S during the period from time t2 to t3.
5 changes from high level to low level as described above. Then, at time t3, by changing the signal S1 from low level to high level and turning on the analog 5WIO, the light receiving elements 5PC1 and 5P are connected to the input terminal of the amplifier A1.
Connect C2 in parallel. As a result, both light receiving elements are switched to receive light, and at the same time, the analog switch AS2
．． It opens with the AS3 signals S2 and S3, interrupts the integration operation of the mirror integrator, and prevents the input to the integrator due to the transient fluctuation of the intensifier A2 caused by the switching operation of the light receiving elements 5PC1 and 5PC2. .

Further, from time t4, when the light emitting element IRS is ON, the analog switch AS3 is ON, and conversely, the light emitting element IR5 is OFF.
t2 so that the analog switch AS2 is ON when F.
Integration is started at a timing that is 180° out of phase with the period from ~t3.

1. Therefore, a voltage having a polarity opposite to that of the period t2 to t3 is applied to the inverting input terminal of the amplifier A4 of the Miller integrator, and the output of the integrator gradually decreases after time E4.

When the output iNT of the integrator falls below the threshold value of the comparator CP2, the output terminal of the comparator CP2 is inverted from low level to high level, and the signal S6 provides a ranging completion signal to the logic circuit C0NT.

Below 1 - The time of L rising integration from time t2 to t3 from water level 1t is TA, the time of falling integration from t4 to the completion of the above distance measurement is TA, the value of output voltage Jli of light receiving element 5PC2 is A, 5
Assuming that the output current value of the PCI is B, the charging voltage of the capacitor c3 during 1.up-integration and the drop voltage of the capacitor during down-integration hold as is clear from the waveform iNT. ■- From formula (2), when the integration time TA is constant, the subject distance can be determined by measuring the other integration time TA+B and the ratio A/A+B of the output current value from one photodetector. .

In this way, when the object at the center of the screen is at a finite distance, the distance to the object at the center of the screen is measured by the above-described operation, and the camera focuses based on this distance measurement information and takes a picture.

However, if the distance of the subject at the center of the screen is infinite, the light emitted from the light emitting element IR5 will pass through to the background because the subject is not at the center of the screen even though it is nearby. There may be many cases where it gets lost. This case will be explained using FIG. 6.

When the subject at the center of the screen is extremely far away, the level of its reflected light is small, and the integrator output iN at time t3
T's rise level is small. Therefore, at time L3, the output of the comparator CPI remains at a high level, and the distance to the subject at the center of the screen is determined to be infinite.

In such cases, the subject below often depends on the periphery of the screen. Inadvertently, the light projecting elements are switched to the light projecting elements IRwl and IRw2 that project light to the periphery of the screen, and the 1-up integration and down integration described in 11 is performed again.

Between times t3 and t5, the analog switch AS4 is closed and the integrator MINT is initialized as described above.
4 to t5, the light emitting elements IRw1 and IRw2 perform the preliminary light emission, and from time t5 to t6, J:m! From time t6 to time t7, integration is interrupted and downward integration is performed from time t7.

After that, the distance of the object around the screen is measured in the same way,
This is used as distance information to focus the photographic lens and take a photograph.

In this embodiment, when the subject at the center of the screen is at infinity, the distance to the subject at the periphery of the screen is used as distance measurement information, but if the subject at the periphery of the screen is also at infinity, distance measurement is performed again for the subject at the center of the screen. You can do it like this.

In addition, although the light emitting elements are divided into two groups, one at the center of the screen and the other at the periphery, it is also possible to further divide the photographing surfaces into three or more groups and perform distance measurement with priority.

FIGS. 7 and 8 are circuit diagrams illustrating the configuration of the light receiving section when a PSD is applied as the light receiving element in the embodiment of FIG. 4.

In FIG. 7, OP is an operational amplifier corresponding to amplifier A1 shown in FIG. 4, FC is resistors R2, R3, and capacitor 0.
A negative feedback network corresponding to the first grade, PSD is a semiconductor device detector, a and b are signal electrodes of the detector, and C is a support electrode. SWA and SWB are switches that are controlled to open and close during the ranging sequence, and semiconductor switches, mechanical switches, or the like are used as the switches 31 and the like. Vrefl.

Vref2 each indicates an X quasi-potential.

In FIG. 7, when the switch SWA is opened and the switch SWB is closed, a fundamental potential Vref1 is applied to the signal electrode.

When a bias voltage is applied to one signal electrode, the semiconductor device detector PSD generates a signal current (as shown in FIG. Corresponds to the output A of 5PC2 in the example. Also, when the switch SWA is closed and SWB is opened, one electrode of the semiconductor device detector PSD is opened, so the total light reception output (A from electrode a) is
The sum of the output and the B output from the current S) is output from electrode a, and as a result, 5PCI and 5PC in the embodiment of FIG.
The sum of the outputs of 2 and 3 A+B is obtained.

FIG. 8 is a circuit diagram showing a modification of the embodiment in FIG. 7, and the same components as in the embodiment in FIG. 7 are denoted by the same symbols as 8 and 1. In FIG. 8, the switch SWA in FIG. 7 is omitted, and a switch SWC is provided which is complementary to the switch SWB.
The difference from the embodiment shown in FIG. 1O is that the switch SWC is closed to obtain an output A, and then the switch SWC is opened to obtain an output A+B.

As described in detail above, according to the present invention, when the subject is in the center of the screen, a photograph is taken with the subject in focus like a conventional autofocus camera, and when the subject is in the center of the screen. To automatically switch the distance measurement part to the periphery of the screen, without the need for troublesome operations to focus on the subject, even if the distance measurement information for the center part is at infinity. This makes it easy to accurately focus on the subject you want to photograph.

Furthermore, by determining the integral operation for the subject to be photographed only by the L-increase integral, the distance measurement time for the automatic focus adjustment section operation is shortened, so that it is possible to speed up photographing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing the structure of the light receiving element of the light receiving section in FIG. 1, FIG. 3 is a diagram showing an embodiment used in the present invention, FIGS. 4 and 5 , FIG. 6 is a circuit diagram showing an embodiment of the invention and a timing chart, and FIG. 7 is a diagram showing a timing chart.
8 are circuit diagrams showing other embodiments of the light receiving section shown in FIG. 4. In fig.

Claims (1)

[Scope of Claims] A first light projecting means for projecting light onto a subject at the center within the field of view, and a second light projecting means for projecting light onto a subject at the periphery within the field of view. light receiving means arranged at a baseline length apart from each other and receiving reflected light from the subject by the light projection;
The light-receiving means is a plurality of light-receiving elements or a single light-receiving element that changes output according to the incident angle of the reflected light, and when calculating the distance to the object based on the plurality of outputs of the light-receiving element, A first signal for increasing and storing an output obtained earlier among the outputs of the light receiving element outputted in time series in response to a switching means that sequentially switches the outputs of the light receiving element, and an output obtained later. In the distance measuring device that obtains object distance information by calculating a second signal that performs downward integration of Distance information is calculated by outputting the second signal from the light projecting means, and if the first signal is less than a predetermined value, the signal is canceled and the first light projecting means is output from the second light projecting means. A distance measuring device characterized in that distance information is obtained by switching to optical means.