JPH01187511A - Rangefinding device for camera - Google Patents

Abstract

PURPOSE:To obtain a rapid and accurate rangefinding function by setting a photographic lens in a specified lens set position when a photoelectric output is obtained from a photodetector for a short distance warning. CONSTITUTION:An AF control circuit 21 and an AF table 28 to which the set position of the photographic lens 10 is let to correspond every rangefinding data inputted from the AF control circuit 21 are connected to a microcomputer 22. When the photoelectric output is obtained from the photodetector S6 for the short distance warning at the time of measuring the distance of i-th rangefinding zone, the photographic lens 10 is set on the specified lens set position set at the time of measuring the distance of the (i-1)-th rangefinding zone, for example, the lens set position which is the farthest in the (i-1)-th rangefinding zone. Thus, it can be prevented that rangefinding is disenabled or rangefinding is uselessly repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active type distance measuring device used in a camera.

[Conventional technology]

Active type distance measuring devices, which are often used in recent compact cameras, project a light beam for distance measurement toward the subject, and use a light receiving sensor to receive the reflected light from the subject. There is. The light-receiving sensor has multiple tiny light-receiving elements arranged in the baseline length direction, and by electrically identifying which of the light-receiving elements the reflected light from the subject has entered, it can measure the distance to the subject. You can get the distance signal.

By the way, in the conventional distance measuring device as mentioned above, in addition to the normal distance range from 1 m to infinity, for example, it is possible to measure a macro range from several tens of cm to 1 m while using a common light receiving sensor. Efforts have been made.

For this purpose, a first light emitting section for normal distance range measurement, which has a light emitting axis parallel to the optical axis of the photographic lens, and a first light emitting section for short range distance measurement, which is set on a different light emitting axis from this light emitting axis, are required. This is achieved by providing a second light projecting section for According to this, the distance measurement range can be substantially expanded without increasing the number of light receiving elements, which is very convenient.

In addition, when measuring distance in a macro range, the intensity of the reflected light from the subject generally increases, so in order to distinguish as accurately as possible whether or not light has entered the photodetector, it is necessary to monitor the photoelectric output from the photodetector. The reference voltage of the comparator is set high to evaluate the distance, and on the other hand, the reference voltage of the comparator is set low to be able to detect even weak reflected light from distant objects during normal distance measurement. It is advantageous to keep it.

[Problem that the invention seeks to solve]

However, as mentioned above, a common light receiving sensor is used for distance measurement in the macro range and the normal distance range, and the reference voltage of the comparator is increased during distance measurement in the macro range to evaluate the photoelectric output from the light receiving element. In such a configuration, a dead zone may appear particularly at the boundary between the macro range and the normal distance range.

In other words, if the reflected light from the subject cannot be detected during the first distance measurement in the macro range, it should be possible to detect the reflected light from the subject during the next distance measurement in the normal distance range. However, reflected light from the subject cannot be detected even from this normal distance range. As a result, problems arise in that the set position of the photographic lens is not determined and photographing becomes impossible, or useless distance measurement is repeated until a photoelectric output of a predetermined level or higher is obtained from the light receiving element.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and even when a subject is present at the boundary between a plurality of distance measurement zones, distance measurement may become impossible or measurement may be performed in vain. To provide a distance measuring device for a camera that does not repeat distance measurements.

[Means for solving problems]

In order to achieve the above object, the present invention divides the ranging range into N ranging zones, and a plurality of light receiving elements are arranged in the baseline length direction, and a light receiving element for short distance warning is also installed at a close position. The light-receiving sensor receives the reflected light from the subject in order from the near distance measuring zone, and
≦i≦N) When a photoelectric output is obtained from the short-distance warning light receiving element when measuring the distance in the distance measuring zone (+-
1) Set the photographing lens at a predetermined lens set position that is set when the distance measurement zone is measured, for example, at the farthest lens set position in the (i-1)th distance measurement zone. This is how it was done.

[Operation] According to the above configuration, in the process of dividing the distance measurement range into a plurality of distance measurement scenes and sequentially measuring the distances in these scenes, the distance measurement of the (i-1)th distance measurement zone is performed. If a photoelectric output is not obtained from the light receiving sensor at this point, and when distance measurement is performed for the next Nth ranging zone, the light receiving sensor will detect that there is a subject closer to the Nth ranging zone. When a short-distance warning appears, the shooting lens is set at a predetermined position included in the (+-1)th distance measurement zone, and the shooting lens can be quickly set without repeating distance measurement. Now you can set the focus position.

An embodiment of the present invention in which the distance measurement range is divided into two (N=2), a macro range and a normal range, will be described below with reference to the drawings.

[Embodiment] Fig. 2 schematically shows an active type ranging system, in which a light projecting section 2 includes a discharge tube 3 that emits near-infrared light. discharge tube 3
4. A slit plate that shapes the light from the 4. It consists of a light projecting lens 5. Further, the light receiving section 7 includes a light receiving lens 8. It is composed of a light receiving sensor 9 and a light receiving sensor 9. The optical axes 5a and 8a of the light projecting lens 5 and the light receiving lens 8 are parallel to the optical axis 10a of the photographing lens 10, and are separated by the base line length. As will be described in detail later, the light receiving sensor 9 is formed by arranging small horizontally long rectangular light receiving elements 81 to S6 in the baseline length direction.

When a slit light is emitted from the light projector 2 toward the subject, a portion of the light is reflected by the close subject 12, and the reflected light 12a enters the light receiving element S3 through the light receiving lens 8. Furthermore, when a part of the slit light is reflected from the middle-distance object 13 or the long-distance object 14, the reflected light 1
3a and 14a are each light receiving elements S2. It comes to be incident on Sl. Therefore, the distance to the subject can be determined by detecting which light receiving element of the light receiving sensor 9 receives the reflected light from the subject. Note that if a slit light is used as the light beam for distance measurement in this way, the light beam for distance measurement will be irradiated even when the main subject is off the center of the shooting screen, so that the main subject will be illuminated with the light beam for distance measurement. This eliminates the need for troublesome operations such as aiming operations and reframing after distance measurement, but distance measurement can also be performed by projecting spot light instead of slit light.

Figure 3 shows an optical system in which an infrared light emitting diode 15 (hereinafter referred to as IRED 15) is added to the above-mentioned distance measuring system, and the same light receiving sensor 9 is used, but the distance measuring function at short distances is further improved. This is what is shown. The light projection optical axis 15a of the IRED 15 is tilted toward the light receiving sensor 9 by an angle θ with respect to the optical axis 5a of the light projection lens 5, and emits a light beam in a spot pattern toward the subject. According to this, it becomes possible for the light receiving sensor 9 to receive reflected light from a subject at a closer distance than the close range that can be detected by the slit light from the light projecting section 2.

FIG. 4 shows the correspondence of the set position of the photographing lens 10 with respect to the subject distance range, where N1-N1° represents the set position in the normal range determined when distance measurement is performed using the slit light from the light projecting unit 2. n1 to n5 represent the set positions of the macro range determined when distance measurement is performed using the spotlight from the IRED 15. These set positions n1 to n,,
N, ~N1G is the subject distance! , ~ff115 is set as the optimum focusing distance, but if the diameter of the minimum circle of confusion that can be considered to be in focus is, for example, 0.025 mm, then the photographing lens 1
When considering a depth of field of 0, approximately! It is possible to continuously focus on a subject distance range from , to infinity.

Discharge tube for distance measurement described above 3. Light receiving sensor 9゜I RE
D15 is used with the circuit shown in FIG.

The discharge tube 3 for distance measurement is the discharge tube 1 for illuminating the subject during shooting.
The operation of the IRED 15 and the IRED 15 are controlled by a strobe drive circuit 18, and the IRED 15 is controlled by an IRED drive circuit 19. Light receiving element 31 forming the light receiving sensor 9
~S6 is connected to the signal processing circuit 20, and the light receiving element 31~
The photoelectric output from each S6 is converted into a signal by a signal processing circuit 20. The signal processing circuit 20 includes an AF control circuit 2.
1 is connected and AF! IJ control circuit 2 child circuit 2 processing circuit 2
The signal output from 0 is converted into ranging data and input to the microcomputer 22. In addition, as will be described in detail later, AF! From the II control circuit 21, the discharge tube 3. A signal for lighting the IRED 15 is output.

The microcomputer 22 includes the strobe drive circuit 18. In addition to the AF control circuit 21, the program shutter 23
A shutter drive circuit 24 for controlling opening and closing of the shutter drive circuit 24. A photometry circuit 25 that measures the subject brightness, a motor control circuit 27 that drives the motor 26, and an AF child table 8 that associates the set position of the photographing lens 10 with each distance measurement data input from the AF control circuit 21 are connected. There is.

The signal processing circuit 20 has a circuit configuration as shown in FIG. 5, and each photocurrent signal from the light receiving elements S1 to S6 is converted into a voltage signal by a first-stage operational amplifier to which a reference voltage V31 is applied. be done. This voltage signal also includes a DC component, that is, a photoelectric signal caused by external light such as sunlight, but since a capacitor for cutting low frequency components is connected to the output terminal of each first-stage operational amplifier, the reference voltage Only signal components that do not include DC components are input to the operational amplifier at the next stage of VS2. The photoelectric output amplified by the next-stage operational amplifier at a constant amplification factor is
Two comparators 31a, 31b, 32a, 32b, --- are provided for each of the light receiving elements 81 to S5.
135a and 35b, and the photoelectric output from the light receiving element S6 is input to the comparator 36a.

A comparator 31a to which the same photoelectric output is input.

31b, 32a, 32b, ・--135a, 35b
are respectively supplied with a reference voltage V by a voltage divider 38.
111+Vnb is given. The level of this reference voltage is set to ■, llI>■o, so the photoelectric output output from each of the light receiving elements and amplified to a constant ratio by the first and second stage operational amplifiers has two types of standards: high and low. It is compared with the voltage V n@+Vnb. Then, the photoelectric output is the reference voltage V nm or the reference voltage Vnb
If it is above, a high level signal (H signal) is sent to each comparator 31a, 31b, 32a,
Appears at the output ends of 32b, . . . , 35a, 35b. In this way, the photoelectric output from each light-receiving element is set to two types of reference voltages, high and low. By comparing with a comparator given 8°■o, two series of binarized signal outputs Af
i,, A7, can be obtained.

Such two series of signal outputs A. , A, and b, it becomes possible to measure the distance without being affected by the strength of the reflected light from the subject.

That is, as shown in FIG. 6(A), when a high-intensity reflected light pattern 40 from the subject enters the light receiving element S4 among the light receiving elements 31 to S6 arranged in the baseline length direction, this original The reflected light pattern 40 is often accompanied by a concentric hollow 41, and adjacent light receiving elements 33.
35 as well, a photoelectric output appears as shown in FIG. 3(B). Moreover, even if the halo 41 is small,
When strong reflected light from a subject enters the light receiving element S4, the adjacent light receiving elements S3. S
5, a certain ratio of photoelectric output often appears.

In such a case, if there is only one comparator connected to each of the light receiving elements 83 to S5 and its reference voltage is . H signal) is output from each comparator, and the light receiving element S3. It is erroneously detected that the reflected light from the object is also incident on S5. On the other hand, when the reference voltage of the comparator is set to ■8, the intensity of the reflected light from the subject is weak, and the light receiving element S to which this reflected light is incident
When only a photoelectric output of the level shown by the dashed line from 4 can be obtained, it is impossible to detect the incidence of reflected light from any of the comparators.

Such a problem is caused by the reference voltage □ in Figure 6 (A).
, ■ The reference voltage corresponding to 1 is applied to each comparator 3.
1a, 31b, 32a, 32b.

. . , 35a, 35b as V n &+ V,, b, and the signal output A7 as described in detail later.
This problem can be solved by evaluating both 3° Anb and determining the set position of the photographing lens 10. Furthermore, in this embodiment, this reference voltage ■. a+ Vnb is set to V6. ＞V5a＞V4〉・・〉■18
, and V 5b > V 4b 〉...〉■1. It is set as follows. This was decided in consideration of the fact that - during boat fishing, the intensity of reflected light from a distant object is lower than that from a close object. According to this, even if the amplification factors of the first and second stage operational amplifiers are kept constant, a good detection function can be obtained for reflected light from a subject with average reflectance such as human skin. be able to.

Note that during distance measurement in the macro range, the reflected light from the subject is strong, so the comparators 31a and 3 whose reference voltage is higher
2a, . . . , 36a to perform distance measurement without being affected by noise, and when measuring distance in the normal range, the comparator 31b whose reference voltage is lower,
The signal output Anb from 32b, . . . , 35b is also used in conjunction with the signal output A 11 B.

The comparators 31a, 31b, 32a, 32b, .
..., the signal output AI of the H signal or L signal appearing at the output terminal of 36a! l+ AIb+ A2B+ ...A
6 a is input to the A F @ control circuit 21 . AF
The control circuit 21 is configured as shown in FIG.
, , , , A, b are D-flip-flop circuits FF, , FF provided corresponding to each comparator.
It is input to the clock terminal of nb (hereinafter simply referred to as FF, FF, b) via an AND gate.

This AF control circuit 21 includes the above-mentioned FFfi, FFn.
In addition to b, there is a reset pulse generation circuit 43 which outputs a reset pulse after a certain period of time after applying the power supply vcc. A counter 45 that counts clock pulses supplied from the microcomputer 22. A shift register 48 receives signals from the decoder 46°FFn, FFfib, which outputs control pulses for performing a distance measurement sequence according to the count value of the counter 45, and outputs the signals as distance measurement data.
etc.

FIG. 8 shows the circuit configuration of the strobe drive circuit 18. This strobe drive circuit 18 includes a distance measuring discharge tube 3,
It controls the operation of both the discharge tube 17 for photographing and the discharge tube 17 for illuminating the subject with auxiliary illumination light during photographing. Capacitor C,,C2
is for supplying luminous energy to each of the discharge tubes 17.3, and is charged via the booster circuit 49. A switch device 50 is connected in series to one capacitor C1. This switch device 50 is a microcontroller.
□It turns on when an H signal is input from the computer 22 to the terminal T6, and turns off when an L signal is input. Note that if the semiconductor switch shown in FIG. 9 is used as the switch device 50, it becomes unnecessary to apply an H signal to the terminal T6 when charging the capacitor C0. Also,
Each terminal T+ and T2 provided in the strobe drive circuit 18
, T3. T4 and T5 are the oscillation start signal input terminal 1 of the booster circuit 46, the charge completion signal output terminal of the capacitor C2, the light emission trigger signal input terminal of the photographing discharge tube 17, and the distance measurement discharge tube 3, respectively. Used as a light emission trigger signal input terminal.

The operation of the distance measuring device configured as described above is as follows. For example, when the power switch is turned on by opening the lens cover, the booster circuit 49 shown in FIG. 7 is activated and the capacitors C1 and C2 are charged. The preparation for photographing is completed by inputting the charge completion signal of the capacitor C3 to the microcomputer 22.

When the power switch of the distance measuring device is turned on at the beginning of the pressing operation of the shutter button (not shown), the power supply VCc is applied to the AF control circuit 21. After waiting for the stabilization of the power supply vcc, a reset pulse is output from the reset pulse generation circuit 43 shown in FIG.
OFF for opening/closing control. The signal is set, an H signal appears at the subterminal, and the AND gate 44 is opened. Further, at the same time, the counter 45 is reset.

The microcomputer 22 outputs a clock pulse to the AF control circuit 21 after a delay of 100 msec from turning on the power switch of the range finder.

During this 100 msec delay, each comparator 31a, 31b, 32a of the signal processing circuit 20.

Reference voltage ■ given to 32b, . . . , 35a, 35b, 36a. B+ Vnb is stabilized, etc.

A clock pulse from the microcomputer 22 is supplied to a counter 45 through an AND gate 44. A decoder 46 is connected to the counter 45.
controls the distance measurement sequence in accordance with the clock pulse count value of the counter 45.

The decoder 46 first includes FFs for latching the signal outputs A B @, A I, b from the signal processing circuit 20;
,.

A reset pulse 51g4 is output to FF, , b. Thereafter, the decoder 46 outputs a first trigger signal to the I RED drive circuit 19. As a result, the I RED 15 lights up for a predetermined period of time, projects near-infrared light onto the subject, and the distance to the subject is determined! Distance measurement in a macro range of 5 or less is started. A predetermined time after the first trigger signal is output, the decoder 46 outputs a read pulse having a pulse width of a predetermined time.

During distance measurement in this macro range, this read pulse is input to one terminal of an AND gate connected to each clock terminal of FF-.

A comparator 31 is connected to the other terminal of the AND gate.
Since the output terminals of comparators 31a, 32a, . . . , 36a are connected, after the read pulse is supplied, the corresponding FF na is set.

That is, if the subject exists within the macro range, an H signal will appear at one of the output terminals of the comparators 31a, 32a, . . . , 36a, so the corresponding FFs, . Ru. Note that the low reference voltage V
. No read pulse is supplied to the clock terminal of FFfib which latches the output from the comparator which is given, and therefore the signal output Anb causes the FF nb
is never set.

When a certain period of time has elapsed after the read pulse was output, the decoder 46 outputs r0N10 of the shift register 48.
An H signal is output to the FF J terminal by 51g2. Further, this H signal causes the AND gate 55 to be in an open state. Therefore, the clock pulse input to the rCK terminal of the shift register 48 via the AND gate 44 is
5 and is supplied to the microcomputer 22 as a ranging clock pulse.

When a clock pulse is supplied to the rcKj terminal with an H signal input to the rON10FFj terminal of the shift register 48, this clock pulse sequentially transfers the data stored in each bit position of the shift register 48 to the next bit position. Acts as a shift pulse to move the The shift register 48, which stores the Q terminal output from FF, for each bit position, outputs a signal A, , 8.
is transferred to the microcomputer 22 as ranging data that maintains the bit position arrangement in the shift register 48.

That is, among the signal outputs Aa, only Aaa is an H signal and FF4. If only "roooloo" is set, the distance measurement data "roooloo" is transferred to the microcomputer 22.

Note that if a read pulse is also supplied to FFnb while the H signal 51g1 from the decoder 46 is input to the D8 terminal of the shift register 48, the signal output Afib from the comparator 31b, 32b, etc. whose reference voltage is lower
can be latched, but in the macro range, the intensity of reflected light from the subject is strong, and therefore electrical noise such as halo 41 and crosstalk is likely to be included as shown in Figure 6, so the high It is sufficient to use only the signal output Afi8 obtained as a result of the comparison with the reference voltage.

After a predetermined number of shift pulses are input to the shift registers 4 and 8, an H signal 5 is sent from the decoder 46 to the input terminal of the Nant gate 56, indicating completion of distance measurement in the macro range.
1g6 is supplied. Since the H signal from the OR gate 52 is given to the other side of the Nant gate 56, when the H signal is output from the decoder 46, the Nant gate 56
An L signal appears at the output terminal of. When this L signal is input as an H signal to the clock terminal of FFo through the AND gate 57° inverter 58, FFO is set and the AND gate 44 is closed. As a result, the clock pulse is cut off, the counter 45 also stops counting, and the distance measurement sequence for the macro range is completed.

Once distance measurement data is obtained by distance measurement in the macro range, the first
As shown in the flowchart of FIG. 0, the microcomputer 22 determines the lens set position from the ranging data obtained by the signal output A I'la. For example, if the distance measurement data corresponding to the order of the comparators 31a, 32a, . . . , 36a is "001000J", "n3" in FIG. 4 is determined as the lens set position. Note that during distance measurement in the macro range, the subject is irradiated with a spot-shaped light beam, so the light receiving elements 31 to S6
The reflected light does not enter three of the light receiving elements (the reflected light enters up to two light receiving elements at most. Therefore, by prioritizing the photoelectric output from the light receiving elements on the near side,
Lens set positions can be easily correlated from distance measurement data.

Note that the light receiving element S6 is used as a light receiving element for short distance warning, and when the distance measurement data is [000001J, it means that the subject is closer than the closest distance at which the photographing lens IO can be set. In the case of a child, a short distance warning is displayed in the viewfinder, for example. In this case, it is necessary to change the subject distance and perform distance measurement again in the macro range.

By the way, as a result of distance measurement in the macro range, the H signal was not included in the signal outputs A, , a, and FF, .

If none of the above is set, the OR gate 52
Since the H signal is not output from the Nant gate 56, the output of the Nant gate 56 becomes the H signal and the FF is not set. Therefore, the distance measurement clock pulse is not supplied to the microcomputer 22, and data transfer of the shift register 48 is not performed. In this case, distance measurement is continued in the normal range.

During distance measurement in the normal range, an H signal is supplied from the microcomputer 22 to the terminal T2 of the strobe drive circuit 18, and the operation of the booster circuit 49 is prohibited. After that, a reset pulse 51g4 from the decoder 46 causes the FF,
1. , FF1. b are reset, and a second trigger signal is sent from the decoder 46 to the strobe drive circuit 18.
It is input to terminal T5 of. As a result, the electric charge stored in the capacitor C2 causes the discharge tube 3 to emit light. After the second trigger signal is output, when the clock pulses for a certain period of time are counted by the counter 45, the decoder 46
A read pulse 51g5 having a predetermined pulse width is output from. When measuring distance in the normal range, unlike when measuring in the macro range, the reading pulses are FF, ..., F.
Since the signals are supplied to the respective AND gates connected to the clock terminals of Ff and b, both signal outputs A, , A7, based on the reflected light from the subject are FF, FF, FF, b.
latched to.

When distance measurement is performed in the normal range and any of FF, ..., FF, b is set, an H signal appears at the output terminal of the OR gate 52, and an H signal is sent from the decoder 46 to the r0N10FFJ terminal of the shift register 48. 51g2 is output. This H signal causes the clock pulse to pass through the AND gate 55 and be supplied to the microcomputer 22 as a ranging clock pulse. Note that the shift register 48 outputs signals A, , 1 . A, .
You can decide whether it is a signal or not.

As in the case of distance measurement in the macro range, r of the shift register 48
By inputting an H signal to the 0N10FF J terminal and supplying a clock pulse to the rCKJ terminal, the shift register 48 outputs the first distance measurement data by the signal output A□ and the second distance measurement data by the signal output Afib. It is transferred to the computer 22. After a predetermined number of shift pulses are input to the shift register 48 in this way,
An L signal 51g7 indicating that the ranging sequence is completed is supplied from the decoder 46 to the input terminal of the AND gate 57.

As a result, an L signal appears at the output terminal of the AND gate 57, and this is input as an H signal to the clock terminal of F F o via the inverter 58 . Then, the AND gate 44 is closed by setting the FF, and the distance measurement sequence is completed.

By distance measurement in the normal range, for example, r as the first distance measurement data.
olloooo” (FFz,, FF3m are set)
, ro 111 o as the second distance measurement data.

(FF2., FF3b, FF4. are set), the microcomputer 22 controls the AF child table 8.
The first one is based on the respective distance measurement data. Determine the second lens set position. As shown in the AF element table 8 in FIG. 11, when determining the lens set position in the normal range, the subject brightness information (EV value) detected by the photometry circuit 25 is also referred to.

Now, if it is "EV 15 J", the first
The distance measurement data is sent to the light receiving element S2. Since this means that the reflected light is incident on S3, 1N7'' is obtained as the second lens set position using the AF element table 8 in FIG. Furthermore, regarding the second distance measurement data, when light is incident on three or more light receiving elements, two on the short distance side, that is, S3.
Since the signal from S4 is prioritized, 'NsJ is obtained as the second lens set position. In this case, since the second lens set position is two or more steps closer to the second lens set position, the final lens set position is determined as "N." Of course, by increasing the data in the AF element table 8, the lens set position can be determined not only by prioritizing only the two closest light receiving elements as described above, but also by considering the output from other light receiving elements. You can also do it like this.

By the way, as a result of distance measurement in the macro range, the signal output A
A, does not contain "1", and when distance measurement is continued in the normal range, the first distance measurement data is roooooolJ,
That is, the reflected light from the subject may enter only the short-distance warning light receiving element S6, and only the FF6s may be in the set state. Originally, the first distance measurement data in the normal range was roo
oool" means that the reflected light from the subject cannot be detected even though any of the light receiving elements should be able to detect the reflected light from the subject during distance measurement in the macro range. This is because when measuring distance in the macro range, the light receiving element S
This is due to the fact that the photoelectric outputs of 1 to S6 are detected based on the high reference voltage (2).

Figure 12 shows the subject when measuring in the macro range.
It shows the photoelectric output of the light receiving elements S1 to S6 when approaching from 0 cm. When these photoelectric outputs are evaluated based on a low reference voltage Vnb, for example, 6
The reflected light from the subject at a distance of 0 cm is reflected by the light receiving element 8.
1 to S4, but if this is evaluated based on the high reference voltage ■,,a, it will be detected only by the light receiving element S2, and accurate distance measurement will be possible. It becomes like this. However, by increasing the reference voltage in this way, it is possible to
The distance range Δ2 of ~80 cm becomes a dead zone. This distance range Δl belongs to the macro range that cannot be covered during distance measurement in the normal range, and the reflected light from the subject at this position is detected by the light receiving element S6 for short distance warning during distance measurement in the normal range. It will be detected.

In such a situation, when rlJ is not included in the signal output An during distance measurement in the macro range and a short distance warning is obtained when distance measurement is continued in the normal range, the first
As shown in the flowchart of FIG.
”. By performing this processing, the lens set position is always determined when distance measurement in the normal range is performed. Therefore, inconveniences such as distance measurement becoming impossible or having to measure distance from the macro range again as a result of performing distance measurement from the macro range to the normal range can be solved.

When the lens set position in the macro range or normal range is determined as described above, the number of driving pulses corresponding to this lens set position is sent to the microcomputer 22.
is output to the motor drive circuit 27, and the photographing lens 10 is moved. When the movement of the photographic lens 10 is completed, the shutter button is automatically unlocked and photographing can be performed. Then, by further pressing the shutter button, an actuation signal is sent from the microcomputer 22 to the shutter drive circuit 24, and the program shutter 23 opens and closes with an aperture diameter corresponding to the EV value to take a picture.

Incidentally, the aforementioned AF element table 8 also stores control data for the built-in strobe 17 that provides auxiliary illumination to the subject, that is, light emission timing data for the built-in strobe 17, as shown surrounded by a broken line. When the lens set position is determined by the data surrounded by the broken line in the AF element table 8, the microcomputer 22 drives the shutter until the aperture diameter of the program shutter 23 reaches the aperture diameter memorized in the AF element table 8. When the actuation pulse is output to the circuit 24, the microcomputer 22 outputs a trigger pulse to the terminal T4 of the strobe drive circuit 18. As a result, the discharge tube 17 emits light when the program shutter 23 has an aperture diameter corresponding to the subject distance.

In addition, when distance measurement data is obtained by performing distance measurement in the macro range, as shown in the flowchart in Fig. 13, distance measurement is completed by just emitting light from I RED 15, and capacitor C2 is The charged charge is stored as is. In this case, an L signal is output from the microcomputer 22 to the terminal T6 of the strobe drive circuit 18, so that the switch device 50 connected in series to the capacitor C3 is turned off. Therefore, when photographing in a macro range and subject brightness is low and strobe photography is performed, the trigger signal input to the terminal T4 of the strobe drive circuit 18 causes the discharge tube 17 to emit light due to the charge in the capacitor C2, which is stored in the capacitor C1. The added charge is preserved as is.

In this case, the capacitance of capacitor C2 is smaller than the capacitance of capacitor CI, and the amount of light emitted from discharge tube 17 is also smaller.
By correspondingly increasing the opening diameter of the program shutter 23, the timing of light emission from the discharge tube 17 can be determined accurately. Of course, when distance measurement data is obtained through distance measurement in the normal range, terminal T
Since the H signal is applied to , and the switch device 50 is turned on, the discharge tube 17 is discharged by the capacitor C1, and normal strobe photography is performed.

Above, the distance measurement range is divided into two, the macro range and the normal range,
Although an embodiment has been described in which ranging is performed sequentially from a macro range to a normal range, the present invention can also be applied to a case where the ranging range is divided into three or more ranging zones. Further, the reference voltage of the comparator for evaluating the photoelectric output of the light receiving element is not necessarily limited to two types, high and low, as in the above embodiment. That is,
Even if one type of reference voltage is determined, the distance range that is the boundary between the divided ranging zones is
Since the photoelectric output from the light-receiving element tends to be unstable, the present invention is also effective in avoiding this.

〔Effect of the invention〕

As described above, in the distance measuring device of the present invention, in the process of measuring distances in the divided ranging zones in order from the short distance side, a short distance warning is obtained when measuring the distance in the i-th ranging zone. When detected, the position of the photographing lens is determined based on the specific lens set position to be detected in the (i-1)th distance measurement zone. Therefore, even if there is a subject in the boundary area of the divided distance measurement zones, and the detection of its reflected light tends to be unstable, the set position of the photographic lens is determined immediately when the i-th distance measurement is performed. This allows for quick and accurate distance measurement.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of a distance measuring device according to the present invention. FIG. 2 is a schematic diagram showing an example of a distance measuring system in a normal range used in the present invention. FIG. 3 is a schematic diagram of the distance measuring optical system of the present invention including a macro range. FIG. 4 is an explanatory diagram of the lens set position. FIG. 5 is a circuit diagram showing an example of a signal processing circuit. FIGS. 6A and 6B are explanatory diagrams showing a light incident pattern on a light receiving element and a photoelectric output from the light receiving element, respectively. FIG. 7 is a circuit diagram showing an example of an AF control circuit. FIG. 8 is a circuit diagram showing an example of a circuit diagram device showing the configuration of a strobe drive circuit. FIG. 10 is a flowchart showing processing during bald distance measurement. FIG. 11 is a conceptual diagram showing an example of an AF child table. FIG. 12 is an explanatory diagram showing the photoelectric output from the light receiving element in the macro range. FIG. 13 is a flowchart showing processing during strobe photography. 2... Light projecting section 3... Discharge tube (for distance measurement) 7... Light receiving section 9... Light receiving sensors 81 to S6... Light receiving element 10... Photographing lens 15... IRED 17... Discharge Tubes (for photography) 31a, 31b, ..., 36a--Comparator 3
8... Voltage divider FF,..., FFnb... D-flip-flop circuit. 7 (Aisanbu)

Claims (3)

[Claims] (1) The distance measurement range is divided into N distance measurement zones, and the light receiving sensor has multiple light receiving elements arranged in the baseline length direction and a light receiving element for short distance warning at the close position, which detects the distance from the subject. In a camera distance measuring device that receives reflected light in order from a near distance measuring zone, when the i-th (2≦i≦N) distance measuring zone is measured, the short distance warning light receiving element When a photoelectric output is obtained from the camera, the photographing lens is set at a predetermined lens setting position that is set when the (i-1)th distance measurement zone is measured. distance measuring device. (2) The camera according to claim 1, wherein the predetermined lens set position is the farthest lens set position set in the (i-1)th distance measurement zone. distance measuring device. (3) The above-mentioned N is 2, and when measuring the distance in the first distance measurement zone, a spot-shaped distance measurement light beam is projected toward the subject,
3. The distance measuring device for a camera according to claim 2, wherein a slit-shaped distance measuring light beam is projected toward the subject during distance measuring in the second distance measuring zone.