JPH0215216A - Automatic focusing camera - Google Patents

Abstract

PURPOSE:To offer an automatic focusing device which is not affected by the change with the lapse of time in a capacitor and its temperature characteristic by examining the offset of a system by a counted number during a lighting-out period and comparing the offset with the counted value during lighting period. CONSTITUTION:When a range-finding mode is a continuous mode, a lighting control means 28 repeatedly controls a light emitting element 12 to turn on it by a prescribed number of times during a prescribed period. This lighting makes light irradiating an object 15 into reflected light, which is made incident on a bisected light receiving element 19. A differential amplifier 24 takes the difference between the outputs of the light receiving element 19 on sides A and B, and a direction discriminating circuit 25 generates an output only when a photographing lens is a pin-ahead condition (A>B). After the lighting period, a lighting-out period of the same length exists, and a counting means 29 counts output signals from the direction discriminating circuit 25 during lighting-on/off periods. When the counted value during the lighting period is larger than that (offset value) during the lighting-out period, that is judged to be the pin-ahead condition, and a lens driving motor 33 is driven toward a focusing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a so-called active type automatic focusing device having a light projecting section and a light receiving section.

(Prior Art) As is well known, an active type automatic focus adjustment device emits a distance measuring beam from a light emitter to a subject, receives reflected light from the subject at a light receiver, and then Distance measurement is performed based on the incident position of the reflected light relative to the subject, and the photographing lens is moved in the focusing direction based on the results. In such an automatic focus adjustment device, the light receiving section has a light receiving element divided into two areas, A and B, for example. This two-divided light-receiving element is configured so that the magnitude relationship of the output signal is reversed between the front pin and the rear pin. For example, in the case of front pin, A>B,
In the case of a rear pin, the configuration is such that A<B.

As automatic focusing devices using such a two-split light receiving element, those shown in Japanese Patent Application Laid-Open No. 59-220708 and Japanese Utility Model Application No. 61-27107 are known.

The former detects and integrates the received light output signals of the A side and B side in synchronization with the light emission timing, calculates the difference and sum of these integral values, and calculates the time required for these differences and sums to reach the set value. It determines whether it is in focus or out of focus depending on the

In the latter case, the difference component between the A side and the B side is held in synchronization with the light emission timing of the light projector, and the value is compared with two types of thresholds for front pin determination and rear pin determination. The up/down counter is made to count up or down depending on the determination result, and the amount of deviation to the in-focus point is detected as the count value of the up/down counter.

(Problems to be Solved by the Invention) In the conventional device described above, an integrating circuit or a sample bold circuit is used to obtain a focal position shift direction signal from the light reception signal of the two-split light receiving element.

However, such a circuit requires a capacitor,
It was not possible to obtain sufficiently satisfactory performance due to the influence of changes over time and temperature characteristics.

In addition, in the former case, in order to detect whether it is at infinity,
Many circuits were used, such as a -1-8 signal circuit, and a complex circuit was constructed using operational amplifiers and the like.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic focus adjustment device that is not affected by changes over time or temperature characteristics of a capacitor and can be configured with a simple circuit.

[Structure of the invention]

(Means for Solving Problem i!1) The automatic focus adjustment device according to claim 1 of the present invention includes a light projecting section that projects a distance measuring light beam toward a subject, and a light projecting section that projects a distance measuring light beam toward a subject, and a light projecting section that is linked to the operation of a photographing lens. The light receiving portion is displaced and has a light receiving output signal that is different between the front pin state and the rear pin state. Also,
A direction determining circuit is provided that generates an output signal only when the light receiving output signal of the light receiving section is in a predetermined signal state, and lighting control means is provided for repeatedly lighting the light projecting section a predetermined number of times during a fixed lighting period. There is. Further, during the lighting period, the output signal of the direction determining circuit is counted, and during the turning off period of the same length as the lighting period, the output signal of the direction determining circuit is counted at a timing equal to the number of lighting times. A counting means is provided, and an operating direction determining means is provided which compares the number of currants during the lighting period with the counting means during the non-lighting period and determines the operating direction of the photographing lens in accordance with the comparison result. The lens drive motor is provided with a lens drive motor whose operation is controlled in the direction determined by the operation direction determining means.

The automatic focus adjustment device according to claim 2 of the present invention operates for a period of time until the photographic lens starts operating via the transmission system when the lens drive motor is reversed, and operates the lens drive motor at a preset first speed. and a second speed setting means that operates after the elapse of the time period and operates the lens drive motor at a second speed that is set lower than the first speed. be.

(Function) In the present invention, the offset of the system is checked by the number of clicks during the light-off period, and by comparing this offset with the count number during the light-on period, it is determined whether it is the front focus, the rear focus, or the infinite distance. The photographic lens is moved in the direction of focus. Therefore, there is no need to use an integrating circuit or a sample bold circuit as in the past, and the circuit configuration becomes simple. I can do it.

Further, in the invention of claim 2, when the lens drive motor is reversed, the photographing lens is operated at the first speed for a time until it substantially reverses and starts to be displaced via the transmission system, and after this time has elapsed, the photographic lens is operated at the first speed. By operating at speed 2, it is possible to reduce the play that exists in the transmission system and reduce the time when the taking lens remains stopped despite the start of the lens drive motor, that is, the time when it does not contribute to focusing operation. .

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral d3 denotes a light projecting unit, which includes a light emitting element 12 using infrared light L[D, etc., and its lighting drive circuit 13;
A distance measuring light beam 16a is projected toward the subject 15 through the projection lens 14.

Reference numeral 18 denotes a light-receiving section, which includes a two-part light-receiving element 1 consisting of A and B.
9, and receives the reflected light 16b from the subject 15 via the light receiving lens 20. This two-split light receiving element 19 is connected to the light emitting element 12 in conjunction with the operation of a photographing lens (not shown).
It is configured to be displaced along the direction of separation from the main body (in the vertical direction in the drawing). In a so-called front-focus state in which the focusing point
It is incident on the A part of the divided light receiving element 19, and the focus point X
In the so-called rear focus state where the subject 15 is located behind the subject 15 (to the left in the figure), the reflected light 16b from the subject 15 hits the B portion of the two-split light receiving element 19. ) j t 8 J: It is composed of sea urchins.

A base IIIi pressure V ref is applied to the common cathode of the two-split light receiving element 19 . The anode of each of the 7j1 is connected to an operational amplifier (
OP+ (hereinafter abbreviated as operational amplifier).

Connected to the input terminal of OR3. This I-V converter 22.23 converts each output of the two-divided light receiving element 19 into a current-to-voltage, and converts the output signals B+Vref and -A4-yrer.
get.

24 is a differential amplifier, which includes an operational amplifier OP3 and a feedback resistor R1.
Consists of etc. One input terminal of the operational amplifier OPa is connected to the output terminal of the one IV converter 22]-Bl-
Vref is input via resistor R2. In addition, the other I-V converter 23 is connected to the + input terminal of the operational amplifier OPa.
The output -A + V ref of is inputted via resistor R3. Note that this -(- input terminal is connected to the electric circuits to which the reference voltage V ref is applied via the resistor R4.

Therefore, from the output terminal of the differential amplifier 24 configured in this manner, a voltage t$ V ref is added based on the difference component -(Δ-B) of the inputs and is output. This output −(
Δ-B)+V ref becomes the final output from the light receiving section 18.

25 is a comparator consisting of an operational amplifier OP4, and its negative input terminal is connected to the output terminal of the differential amplifier 24 via a capacitor C. Further, a reference voltage V ref is input to the + input terminal via a resistor R5. na d3
, the - input terminal is also connected to the electric path to which this reference voltage V ref is applied via a resistor R6. [Once, this - input terminal had -(△-[3) 10V re
f is input, and as a result, -(A-8)<
An output signal is generated only when the condition O is satisfied, that is, only when A>B. In other words, this comparator 25 determines the polarity (that is, direction) of the output J-(A-B) of the light receiving section 18, and therefore, this comparator 25 is hereinafter referred to as a direction determining circuit.

Reference numeral 27 is Cl) U for overall control, and as shown in the figure, there is a lighting control means 28, a ring 1-means 29, and an operation direction determining means 3.
Has 0. The means for achieving each of these functions will be explained below.

The lighting control means 28 includes a light emitting element 1 such as an infrared LFD.
2 is repeatedly turned on a predetermined number of times through a lighting drive circuit 13 during a lighting period of a predetermined length.

In measuring the distance to the subject 15, in this embodiment, three distance measurement modes shown in FIG. 5 are used: continuous mode, interval mode, and high-speed continuous mode. Details of each of these distance measurement modes will be described later, but in continuous mode, the lighting period of the scheduled length, for example, approximately 40
During m5, the light emitting element 12 is repeatedly turned on 255 times, and then the same length of the unlit period (in this case, about 40 m5) is maintained, and then the on period starts again, so that the on period and the unlit period are continuous. is repeated. Further, the interval mode has the same lighting period and lighting period as described above, but these are repeated at intervals of, for example, about 700 m5. Further, in the high-speed continuous mode, the lighting period and the lighting-off period are each about 4 mS, which is about 10% of the above-mentioned time, and the number of lighting times in the lighting period is also 24.

The lighting control means 28 performs lighting control on the light emitting element 12 in order to maintain the lighting period, the lighting period, and the number of lighting times in each distance measurement mode described above at predetermined values. Note that the light emitting element 12 has a thickness of approximately 158μ as shown in FIG.
The light is controlled to turn on for about 52 μs every 2 seconds.

The counting means 29 has a lighting-on counting function 29a and a lighting-off counting function 29b, as shown in the figure. The lighting time count function 29a counts the lighting period (approximately 4011
During step 13), the pulse-like output signal generated from the direction discrimination circuit 25 is counted. The light-off count function 29b is
During the light-off period (approximately 40 m5), the output of the direction determination circuit 25 is counted at the same timing as the number of times the light is repeatedly turned on (255 times).

The operating direction determining means 30 compares the count number during the lighting period and the count number during the off period, determines the operating direction of the photographing lens (not shown) according to the comparison result, and
Or output a motion command in the Near direction.

The Far or Near direction operation command is given to the motor drive circuit 32 to drive the lens drive motor 33 in the Far or Near direction.

Next, the basic distance measuring operation in the present invention will be explained.

When the distance measurement mode is continuous mode, the light emitting element 12 is illuminated with 25
The lighting is controlled repeatedly five times. Due to this lighting, the distance measuring light beam 16a is projected toward the subject 15, and this subject 15
The reflected light 16b is incident on the two-split light receiving element 19.

At this time, the photographic lens is "front focused" as shown in Figure 1.
state, the reflected light 16b is A of the two-split light receiving element 19.
incident on the side. A sub-output and B of this light-receiving element 19
After the sub-output is subjected to current-to-voltage conversion by the IV converters 22 and 23, the differential amplifier 24 converts the difference component -(A
-B) is extracted and a reference voltage V ref is added. This becomes the output signal of the light receiving section 18. The direction discrimination circuit 25 determines that the output signal of the light receiving section 18 is -(A-B).
It produces an output only if <O, ie only if A>8.

The relationship between the output signal count and the focus state corresponding to the count value will be explained below with reference to FIG.

Here, in the case of a complete "front pin", as mentioned above, about 40
If 255 lights are emitted by the light emitting element 12 during 1IIS, the output of the direction determining circuit 25 will be 255 times.
times rHJ. That is, 255 pulse signals are output and counted by the counting means 29 of the CPU 27.

On the other hand, in the case of "slightly forward pin", due to the influence of disturbance noise and circuit noise components, when looking at individual pulses, A
The case <B may occur.

In the case of A<B, the output of the direction determining circuit 25 is not rHJ but "L", so that the counting means 29 does not perform counting. That is, in this case, out of 255 shots, the number of shots such as 190 or 200 is the count number during the lighting period (hereinafter this will be expressed as (A>B)).

Next, after the above lighting period, during a lighting off period of the same length (approximately 40 m5), the CPU 27 uses the counting means 29 to count the output of the direction determining circuit 25 at the same timing as the number of lighting times (255 times).

Here, even if the light emitting element 12 is off, disturbance noise due to external light, electrical noise, etc., and characteristics of the ranging system (for example,
(e.g., the frequency of appearance is higher at time 0), etc.), the A side and B side of the light receiving element 19 are almost always unbalanced if observed instantaneously. The counting means 29 counts how many pulses there are in this unbalanced state where A>B. Normally, A>B for a certain period of time (255 pulses), but if the inputs on the A side and B side are completely random, the count value will be close to 128+j. The actual count value also varies around 128 phrases. That is, the value of this callan 1 represents the offset 1~ of the system.

Therefore, the value of the turn 1 during this light-off period is expressed as an [offset] below.

Therefore, if the count value (A>B) is larger than the [offset], and the difference is the preset value, that is, the dead band (hereinafter referred to as CD) as the dead band of the system.
If the number of pulses (for example, 30 pulses, which is approximately 10% of the total count value) is expressed as (A
>B)-(Offset)>(DB), it is determined that it is a "front pin".

If the subject 15 is at an infinite distance (3), reflected light from the subject 15 cannot be detected even if the light emitting element 12 emits light. Therefore, even though it is a lighting period, it is in the same state as a lighting-off period, and the count value (A>8) is about 128. On the other hand, the power runt value (A-fuse) during the lights-out period is also 1
It is about 28, and the difference from (A>B) is almost zero. Therefore, the absolute value of these differences is the dead band (DB)
If it is within the range, it can be determined as (3). Note that the same applies when focusing, and it is impossible to distinguish between ■ and in-focus using this method.

In the case of "rear focus", the reflected light 16b from the subject 15 is incident on the B side of the light receiving element 19, so complete "rear focus" is achieved.
In this case, the output of the direction discrimination circuit 25 is always rLJ, and the count value of the CPU 27 during the lighting period (
A>B) becomes zero for 255 times of light emission. Therefore, 12 is the Karan 1-value [offset] of the lights-out period.
It will be less than 8. In other words, [offset) - (A>B
)> (DB), it can be determined as [rear pin].

The basic distance measurement operation described above is the same in interval mode.

In the high-speed continuous mode, the light emitting element 12 is turned on at 24 ms during a lighting period of 4 ms, which is about 10% of the lighting period and the lighting period in the continuous mode and the interval mode.
The light emitting element 12 is turned on repeatedly, and the light emitting element 12 is kept in a non-emitting state for the next 4 ms. Then, during each of these periods, the output signal of the direction determining circuit 25 is counted, and by comparing these count value data, the approximate direction is determined using the same method as described above. However, in this case, dead band (DB) is not used.

Next, the operation will be explained according to the flowcharts of FIGS. 3 and 4.

After starting, perform distance measurement (step ■).

Distance measurement is performed as shown in the detailed flow enclosed by broken lines. First, it is determined whether the distance measurement mode is the interval mode (step no.
Activate the 0m5 interval timer (step ■■). Normally, it is not an interval mode but a continuous mode, so when the judgment is No, the light emitting element 12 is immediately made to emit light 255 times for 4Qms, and during the lighting period (
> Count the output of B (step ■). Return this number from 1 to [△>8]. Next, the light emitting element 12 is
At the same timing as the 5th occurrence, the output j of A>B that falls in the light-off period is run from 1 to 1 (step ■■).

This count value is set as [offset].

Next, both the above count values (A>B) and [Offseller 1-]
It is determined whether the absolute value of the difference is within the dead band (DB) of the system (step 2). If the result is YES, as shown in FIG. 2, it is tentatively determined as ■, and a check (step ■) is performed to check whether or not the focus is in focus. (2) The check will be described later with reference to FIG.

On the other hand, if it is determined that it is not within (DB), F
Since it is either "front pin" or "rear pin", the judgment is made (step ■). As a result, if [△>8)-(offsera 1~)>(DB), it is in the [front focus] state as shown in Fig. 2, so the direction of operation of the photographic lens is set to Fa.
Step ■). Also, (A>B)-(
Offset) > (DB) (If it is, the "rear focus" state is reached, so set the operating direction of the photographic lens to Near from Sera 1~ (Step ■).Next, move the photographic lens in the direction set by these Sera 1. In order to operate the lens drive motor 33 shown in FIG.
). This small feed refers to an operation in which the motor 33 is turned on for about 24 m5 and then turned off for about 80118 predetermined times as shown on the left side of FIG. 7.

After the above-mentioned short feed, distance measurement (step ■) is performed again. This distance measurement is the same as step ■, and step (ED
~ ■ Execute j. It is determined whether the absolute value of the difference between the result (A>8) and (offset) is within (DB) (step ■), and if it is outside (DB), it is determined whether a direction reversal has occurred ( step 0). As a result of these determinations, if the lens falls within [DB] or if a direction reversal occurs, it means that the small feed has brought the optimum focus state or a state fairly close to the focus position. In this case, since focus is recognized on the screen, the photographic lens may normally be stopped as it is. However, in order to obtain continuous images like a video camera, the focusing operation must be continued, and endless loop control is required. Therefore, taking these points into consideration, if the distance measurement mode is within (DB) (YES in step ■>, or YES in step O to cause a direction reversal), switch the distance measurement mode to interval mode (step ■). ). In this way, by setting the camera to interval mode, there are intervals between the distance measurement operations when the camera is in focus or very close to focus, which stabilizes the screen, saves power, and improves durability. .

After setting the interval mode (step [phase]), the camera goes through the AF mode (step ■), returns to distance measurement in step ■, and thereafter performs distance measurement in the interval mode.

On the other hand, if the distance measured after the small feed described above (step ■) is not within (DB) and there is no direction reversal, the number of small feeds is determined (step 0), and if it is within 3 times, the small feed is repeated (step 0). Repeat step ■) and subsequent operations.

In this way, small feed and distance measurement are repeated, and the number of times is 3.
When the number of times is exceeded, the number of times is determined to perform minute feeding (step 2). That is, if the number of minute feeds is 8 or less, minute feed is executed (step ■). This minute feeding refers to repeating the operation of turning on the lens drive motor 33 shown in FIG. 1 for about 121113 seconds and then turning it off for about 80 minutes as shown on the right side of FIG. 7 for a predetermined number of times.

After the minute feed, distance measurement is performed again (step 2), and it is determined whether the minute feed brings the object into focus or close to focus (step 2).

If the result of this judgment is YES, set the interval mode (step [phase]) to maintain this in-focus state or a state close to in-focus, and then perform distance measurement in step (2) via the AF mode (step (2)). Return to step. On the other hand, if the judgment (step ■0) after the above distance measurement (step ■) is No, the number of minute feeds will be judged again (step [shares]), and if it is within 8 times, the minute feed (step ■)
After that, repeat the operation after distance measurement (step ■).

When the number of micro-feeds exceeds 8, the lens drive motor 33 is continuously fed (step -) and distance measurement in high-speed continuous mode (step -) is performed thereafter. This continuous feeding is performed according to a preset continuous operation time. Therefore,
Steps to determine whether this continuous operation time has been reached■
), if it has not been reached, determine whether there is a direction reversal (
Step @). If there is no direction reversal, distance measurement in high-speed continuous mode (state block ■) continues. If a direction reversal occurs, the lens drive motor 33 is brought to an emergency stop (step 0). Thereafter, the distance measurement mode is switched to the continuous mode, and the process returns to the distance measurement in step (2) via the AF mode (step 0).

On the other hand, when the continuous feed by the lens drive motor 33 does not cause a direction reversal, and the continuous operation time is reached, the continuous feed is switched back to small feed (step 0) as determined in step (2). In this manner, if a direction reversal occurs, the process returns to the distance measurement in step (2) via the AF mode (step (2)) in the same manner as described above.

Next, with reference to FIG. 4, a description will be given of the 2 check (step 2) when it is determined that the range is within (DB) in the determination after distance measurement in step 2 (step 2).

In other words, as shown in Fig. 2, the above-mentioned determination that the value is within (1) +3) does not indicate ■, but the same holds true for focusing. Do it like this.

First, the operating direction of the photographic lens is set to Far (step 2). Then, minute feed (step ■) is performed in the set direction, and distance measurement (step) is then performed. This distance measurement is also the same as step ■, and step (
Execute D~■.

In this case, if the lens is in focus, repeating the minute feed described above several times will result in a state other than (DB), that is, a state of front focus or rear focus. Therefore, after distance measurement (step ■), it is determined whether it is outside the (DB) and it is also detected whether the state outside the (DB) has been detected three times in a row (step ■).
. If it is not detected 3 times in a row, determine whether the number of minute feeds has reached the scheduled number (19 times in the example shown) (Step ■); if it is less than 19 times, return to Step ■;
Repeat the operation after minute feed.

If the outside of (DB) is detected 3 times in a row by distance measurement after micro-feeding (step ■), it means that the in-focus state has slightly gone out of focus, and (5) is not the case. judge. As a result, it is treated as out-of-focus (step ■), and the process returns to step ■ shown in FIG. Then, it is determined whether the focus is from the front or the back, and the object is moved slightly in the corresponding direction, and the focus is immediately brought into focus (step 2 or 2).

On the other hand, even if the minute feed is performed 19 times, if outside (DB) does not occur 3 times in a row, the lens drive motor 33 is continuously operated in the Far direction (step @>), and distance measurement (step ■) is performed. .This distance measurement is also the same as step ■, and steps ■D-■ are executed.Also, the motor 33 is
In order to prevent continuous rotation in the ar direction, continuous operation is limited to a preset time. Therefore, it is determined whether it is within the set time (step @), and if it is within the time, the result of the distance measurement is determined, and it is detected whether (DB) is outside three times in a row (step 0). If outside (DB) does not occur three times in a row, repeat the operations from the distance measurement (step @) onward.

By repeating this distance measurement (step @), when outside (DB) is detected three times in a row and I is detected, lens drive motor 3
3 is stopped (step 0), and the distance measurement mode is set to the continuous mode (step @). After going through the AF mode (step 0), the process returns to step 3 in FIG. 3 and distance measurement is performed again.

On the other hand, when the motor 33 is operated for the set time and it is determined that the time has elapsed, in step @), the motor 3
Stop 3 (step @). In other words, the lens is in an infinite distance state and in focus with the object 15 located at an infinite distance position, so the interval mode is set (step 0). After this, distance measurement (step @) is performed in interval mode, and when outside (DB) is detected 3 times in a row, (
Step ■) Set to continuous mode Step 0), Δ
After going through F mode (step ■), return to step ■ and perform distance measurement again.

By performing distance measurement using such an endless loop and controlling the driving of the photographing lens based on the distance measurement, an optimal focusing state can always be obtained even when continuous images are obtained as in a video camera.

In this way, the light receiving section 18 that receives the reflected light 16b from the subject 15 accompanying the light projection of the light projecting section 11 has the two-split light receiving element 19, and the polarity of the received light output signal is reversed between the front focus and the rear focus. A direction discriminating circuit 25 is installed to extract a signal in a preset direction from this light receiving horn signal. The direction determining circuit 25 counts the pulse output output from the direction determining circuit 25 during the lighting period, and also counts the pulse output from the direction determining circuit 25 during the lighting period, and also counts the pulse output from the direction determining circuit 25 at a timing equal to the number of times of repeated lighting during the unlit period of the same length following the lighting period. Count the output of 25, compare the count value [△>B) in the lighting period with the count value [offset] in the non-lighting period,
Since the photographic lens is moved in the focusing direction according to the comparison result, there is no need to use an integrating circuit or sample-hold circuit as in the past, which simplifies the circuit configuration, and also improves the aging and temperature characteristics of the capacitor. Accurate focus adjustment can be performed without being affected by

Furthermore, the photographic lens is driven by the lens drive motor 33 shown in FIG. If it is reversed, it will take time for the lens to start moving in a predetermined direction even though the motor 33 has started due to the play. Therefore,
When controlling the lens drive motor 33, the previous rotation direction is memorized, and if the current rotation direction is different from the previous rotation direction, the time until the lens substantially changes to the reverse direction when the motor 33 is started, The motor 33 is configured to have a high rotational speed. That is, a first speed setting means is provided, which is set to a speed faster than the normal displacement speed of the photographing lens, and a second speed setting means is set to a speed corresponding to the above-mentioned normal lens displacement speed. At the time of reversal, the first speed setting means is operated to operate the motor 33 at high speed for the time from the start of the motor 33 to the time when the lens substantially starts to be displaced (predetermined set value);
Thereafter, the second speed setting means may be operated to operate the motor 33 at a low normal lens displacement speed.

In this way, it is possible to reduce the time during which play in the transmission system does not contribute to the focusing operation.

Although the actual 711fIA described above was explained using the triangulation method, it is also a so-called TTL method in which the light receiving lens also serves as the photographing lens.
It can also be applied to devices using this method.

〔Effect of the invention〕

As described above, according to the present invention, the circuit configuration for distance measurement is simplified, and the distance measurement characteristics are not affected by the aging or temperature characteristics of the capacitor unlike in the past, allowing accurate focus adjustment. can be done.

Further, according to the second aspect of the invention, it is possible to reduce the time when the photographing lens remains stopped despite the start of the lens drive motor due to the play existing in the transmission system, and the time during which it does not contribute to the focusing operation. can.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an automatic focus adjustment device according to the present invention, FIG. 2 is an explanatory diagram for explaining the distance measuring operation of the device shown in FIG. 1, and FIGS. 3 and 4 1 is a flowchart for explaining the operation of the device shown in FIG. 1, FIG. 5 is an explanatory diagram of the ranging mode in the device shown in FIG. 1, and FIG. FIG. 7 is a time chart illustrating the small feed state and minute feed state of the lens drive motor shown in FIG. 1. 11... Light projecting section, 15... Subject, 16a... Distance measuring light beam, 16b... Reflected light, 18... Light receiving section, 25...
Direction determination circuit, 28.. Lighting control means, 29.. Counting means, 30.. Operation direction determining means, 33.. Lens drive motor. ≧

Claims (2)

[Claims] (1) A light emitter that emits a distance-measuring beam toward the subject, and a light receiver that is displaced in conjunction with the operation of the photographic lens and that receives different light output signals depending on its front focus state and rear focus state. , a direction determining circuit that generates an output signal only when the light receiving output signal of the light receiving section is in a predetermined signal state; a lighting control means that repeatedly lights the light projecting section a predetermined number of times during a certain lighting period; and the lighting. Counting means for counting the output signal of the direction determining circuit during a period, and counting the output signal of the direction determining circuit at a timing equal to the number of times of lighting during a non-lighting period having a length equal to the lighting period; Operating direction determining means for comparing the count number during the lighting period and the count number during the off period and determining the operating direction of the photographing lens according to the comparison result; and the direction determined by the operating direction determining means. An automatic focus adjustment device comprising: a lens drive motor whose operation is controlled; and an automatic focus adjustment device. (2) a first speed setting means that operates for a period of time until the photographic lens starts operating via a transmission system when the lens drive motor is reversed, and operates the lens drive motor at a preset first speed; 2. The automatic camera according to claim 1, further comprising: second speed setting means that is activated after a lapse of time and operates the lens drive motor at a second speed that is set lower than the first speed. Focusing device.