JP3149282B2 - Position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device,
In particular, for example, a device having an unstable power source such as a dry battery, such as a blade position detecting device in a still camera, or a position detecting device optimal for position detection in a device in which periodic inspection is not necessarily expected. Regarding improvement.

[0002]

2. Description of the Related Art Conventionally, the output of a sensor means is set to a predetermined threshold level (Threshold Level:
A method is known in which the position of the detected member is detected in comparison with a threshold value, and the position and timing of the detected member are controlled. For example, taking a shutter blade for a still camera as an example, generally, immediately after the shutter blade is released,
The running characteristics of the blades are not stable due to the influence of the camera attitude, etc., and a certain amount of approaching section is required to stabilize the running characteristics of the blades. After that, a pinhole is formed, and it is detected that the shutter blade has traveled just before forming the pinhole, and the exposure time and strobe tuning timing are controlled.

As a preferred example thereof, for example, a device using an optical switch such as a photo interrupter or a photo reflector in which a shutter blade opens and closes an optical path from a light emitting portion to a light receiving portion is widely used. FIG. 6 shows in principle an example of a blade position detecting device using a photoreflector. In the circuit shown, a reflector 3 is provided in an optical path from a light emitting diode 1 to a phototransistor 2 and the reflector 3 is interposed. For example, the tip of the shutter blade 4 is caused to travel in the
When the phototransistor 2 is turned on when the optical path is blocked and then opened again, the exposure control circuit 6 is triggered from the timing when the switching transistor 5 is turned on.

[0004]

However, the output of the light emitting diode, the reflectivity of the photoreflector, the sensitivity of the phototransistor and the like have individual differences. The adjustment at the time of shipment was performed by adjusting with 7 or the like. However, since the camera cannot force the user to perform regular inspections, such a method can be used when the performance of each component of the photoreflector changes due to aging of the camera. There was a problem that you can not. In addition, the camera has a problem that a constant voltage circuit is always required because the power source depends on a dry cell and the stability of the power source is extremely low.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is not affected by aging of components such as a photoreflector and does not require a constant voltage source. It is an object to provide a position detecting device.

[0006] In summary, the position detecting device of the present invention has a detecting section along the running operation of a detected member such as a shutter blade, and outputs an analog signal when the detecting section is activated and when it is not activated. Sensor means of varying quantity: output of said sensor means
Holding means for holding a comparison means output level of said sensor means generates a signal when the transition to the level during the operation from the non-operation time of the level of the detection unit based on the threshold level, the holding of the holding means Solution to release state
And a position detecting device comprising: a detecting unit that sequentially transitions the detecting unit to a first operating state, a non-operating state, and a second operating state when the detected member travels. And holding the output of the sensor means when the detection unit is in the first operating state.
The threshold value of the comparing means corresponds to the holding state of the holding means.
Set the first level and run one time
The releasing means releases the holding state each time a row is completed.
The sensor means comprises a light emitting unit and a light receiving unit as a preferred example, and an optical switch from the light emitting unit to the light receiving unit is opened and closed by the light shielding blade. And more preferably, the first
And the load condition in the second operation state is matched.

[0007]

According to the present invention, the output level of the detecting means is preliminarily read prior to the actual position detecting operation, and the threshold level of the comparing means corresponding to the output level of the sensor means at the time of the preliminary reading. It is not necessary to adjust the operating point according to the individual difference of the sensor means or to provide a constant voltage power supply circuit, and the performance of the sensor means may fluctuate due to aging. In addition, the threshold level can be automatically corrected for each shooting operation, and the load conditions at the time of preliminary reading and the actual reading are matched to avoid the effects of load fluctuation. Is done.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an aperture / shutter will be described in detail with reference to the drawings. FIG. 1 shows an example of a shutter mechanism to which the present invention is applied. A shutter blade 10 is swingably supported on a shaft 12 on a base plate 11 and is swingable on a shaft 13 on the back surface of the base plate 11. Pin 14 provided at the tip of opening / closing lever 14 supported by
“a” penetrates through the base plate 11 and engages with a slot 10 a formed in the shutter blade 10. Therefore, opening / closing lever 1
When the shutter 4 is rotated clockwise about the shaft 13, the shutter blade 10 is rotated while the slot 10a is engaged with the engaging pin 14a.
2 is turned clockwise to open an aperture 11 a formed in the center of the main plate 11.

Reference numeral 15 denotes a photoreflector having a light emitting diode 15a as a light emitting portion and a phototransistor 15b as a light receiving portion.
5 is mounted on the front side of the shutter blade 10 with the light-emitting surface of the light-emitting diode 15a and the light-receiving surface of the phototransistor 15b facing the ground plate 11, although the mounting method is not shown in the drawing. A reflector 11b having a high reflectance is formed at the emission point by, for example, vapor deposition. When the reflectance of the base plate 11 itself is high, the base plate 11 itself can be used as a reflector without performing vapor deposition or the like.

A light-shielding blade piece 10b for opening and closing an optical path from the light-emitting diode 15a to the phototransistor 15b is integrally formed at the tip of the shutter blade 10. In this embodiment, the light-shielding blade piece 10b is in an initial state. Then, the optical path from the light emitting diode 15a to the phototransistor 15b is opened, and when the shutter blade 10 performs an opening operation (clockwise rotation about the axis 12), the optical path from the light emitting diode 15a to the phototransistor 15b is blocked. The blade 10 is formed so as to open an optical path from the light emitting diode 15a to the phototransistor 15b immediately before forming a pinhole. In this embodiment, when the shutter blade is at the initial position, the light emitting diode 15 is turned off.
a is pre-emitted, and the threshold level is set according to the output of the phototransistor 15b at the time of the pre-emission. Although only the shutter blade 10 is shown in the drawing, the shutter blade which is basically symmetrical to the shutter blade 10 is pivotally supported on a shaft 16, and the shutter blade not shown in FIG. The aperture 11a is opened by turning left around the axis 16.

FIG. 2 is a circuit diagram according to a first embodiment of the present invention, wherein 10b, 11b, 15a, and 15b denote the above-described light-shielding blade pieces 10b, reflectors 11b, light-emitting diodes 15a, and phototransistors. 15b, the phototransistor 15 illuminated from the light emitting diode 15a
The voltage generated in the resistor 20 by the photocurrent flowing from the phototransistor 15b by the light incident on b is applied to the positive-phase input of the comparator 21. The feature of the present embodiment is that the capacitor 2 corresponding to the photocurrent flowing from the phototransistor 15b during the pre-emission described above.
2 is charged, and the threshold level applied to the negative phase input of the comparator 21 is controlled in accordance with the charging level of the capacitor 22.

More specifically, an output of a voltage follower 23 having a control input is applied to a terminal point of the capacitor 22, and the voltage follower 23 is connected to a CPU 24.
Is turned on when the control signal S1 is applied to the H level, the terminal level of the resistor 20 is applied to the capacitor 22 , and the capacitor 22 is charged to the terminal level of the resistor 20 .

The charge level of the capacitor 22 is applied to a series circuit of resistors 26 and 27 via a voltage follower 25, and the level divided by about 1/2 by the resistors 26 and 27 is input to the negative phase input of the comparator 21. Have been added.
28 is a switching transistor for discharging the capacitor 22, and the transistor 28 is a CPU.
When the control signal S2 applied from 24 becomes H level, it becomes conductive and discharges the electric charge accumulated in the capacitor 22.

Next, the operation of this embodiment will be described with reference to the above items. First, in the initial state, the shutter mechanism is in the state shown in FIG. 1, and the aperture 11a is the shutter blade 1
It is shielded by a shutter blade (not shown) pivotally supported by the shaft 0 and the shaft 16, and the light-shielding blade piece 10b opens an optical path from the light emitting diode 15a to the phototransistor 15b.

In this state, a drive pulse is supplied to a step motor (not shown), and when the step motor rotates by a predetermined number of steps, an unlocking member (not shown) releases the opening / closing lever 14, and the opening / closing lever 14 moves rightward about the shaft 13. Turning. In this embodiment, as a feature point, the pre-light emission operation of the light emitting diode 15a is performed in a time region after the supply of the drive pulse to the step motor is started and before the opening / closing lever 14 is released.

More specifically, after a drive pulse is supplied to the stepping motor, a drive current is supplied to the light emitting diode 15a prior to the opening / closing release of the opening / closing lever 14, and the control signal S1 is at the H level, and the control signal S1 is at the H level. The L level is led to S2.

During the pre-emission operation, the light-shielding blade piece 10b opens the optical path from the light emitting diode 15a to the phototransistor 15b, so that the light emitted from the light emitting diode 15a is reflected by the reflector 11b and enters the phototransistor 15b. And the phototransistor 15
A voltage corresponding to the current flowing through b is generated as a terminal voltage of the resistor 20.

At this time, since the voltage follower 23 is enabled by the control signal S1 of H level,
The voltage follower 23 outputs the terminal voltage of the resistor 20, and the transistor 22 is cut off by the L level control signal S2, so that the capacitor 22 outputs the voltage of the voltage follower 23 (ie, the terminal level of the resistor 20). Charged up to. And the capacitor 22
Is connected to a resistor 2 via a voltage follower 25.
6 and 27, and about 1 by resistors 26 and 27.
The level divided into / 2 is applied as a threshold level to the negative phase input of the comparator 21.

Thereafter, when the opening / closing lever 14 is released, the shutter blade 10 turns clockwise around the shaft 12 while the slot 20a is engaged with the pin 14a to open the aperture 11a. At this time, during the clockwise rotation of the shutter blade 10, the light-shielding blade piece 10b is turned on by the light emitting diode 15 before the shutter blade 10 actually forms a pinhole.
a to block the optical path from the phototransistor 15b to the phototransistor 15b,
Further, just before the shutter blade 1 actually forms a pinhole, the light-shielding blade piece 10b opens the optical path from the light emitting diode 15a to the phototransistor 15b again.

First, if the light-shielding blade piece 10b blocks the optical path from the light emitting diode 15a to the phototransistor 15b during the clockwise rotation of the shutter blade 10, no photocurrent flows from the phototransistor 15b to the resistor 20, so that the terminal of the resistor 20 The voltage substantially drops to the ground level, and the positive-phase input level of the comparator 21 becomes sufficiently lower than the negative-phase input level of the comparator 21. Therefore,
The output of the comparator 21 becomes L level.

Thereafter, when the shutter blade 10 further turns clockwise and the light-shielding blade piece 10b reopens the optical path from the light emitting diode 15a to the phototransistor 15b immediately before forming a pinhole, light is transmitted from the phototransistor 15b to the resistor 20. A current flows, and the photocurrent causes the resistance 20
Is applied to the in-phase input of the comparator 21. On the other hand, the level of the negative-phase input of the comparator 21 is a level obtained by dividing the charge level of the capacitor 22 by about 1/2 by the resistors 26 and 27, and the charge level of the capacitor 22 during pre-emission is as described above. Of the resistor 20 is stored. In addition, in this embodiment, the pre-emission operation is performed in a state in which the drive pulse is supplied to the step motor serving as a load, so that the phototransistor 15b is used between the pre-emission operation and the actual detection operation.
Of the comparator 21 are substantially the same.
Of the positive-phase input level of the capacitor 22 is about 1
Therefore, the output of the comparator 21 is inverted from the L level to the H level.

The CPU24 performs control of exposure control and flash synchronization timing the timing of output of the comparator 21 is inverted to the H level as starting point. And
After one photographing operation is completed, the control signal S2 goes to the H level to turn on the transistor 28 , thereby discharging the charge stored in the capacitor 22.

Next, FIG. 3 shows an embodiment in which the present invention is processed by software instead of the above-described analog circuit, and FIG. 4 is a flowchart thereof. Elements common to those in the embodiment of FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. The terminal voltage VL generated in the resistor 20 by the photocurrent flowing through the phototransistor 15b is omitted.
Are converted into digital values by an analog-digital conversion circuit 29 and input to the CPU 31 via the interface 30.

As a specific operation, a drive pulse is supplied to a step motor (not shown), the light emitting diode 15a is pre-emitted, and the terminal voltage VL of the resistor 20 at that time is converted into a digital value and sampled. After storing the value obtained by multiplying the value by about 1/2 as the reference voltage Vref, the opening / closing lever 14 is released to open the shutter blade 10. After the opening operation of the shutter blade 10, the terminal voltage VL of the resistor 20 is monitored, and at the timing when the terminal voltage VL exceeds the above-described reference voltage Vref, the shutter blade 1 is opened.
It is determined that 0 has reached the desired position, and the subsequent exposure control sequence is executed.

In the above description, a photoreflector is used as an example of the sensor means, and the present invention is applied to the detection of pinholes in shutter blades. However, other than this, an optical switch such as a transmission type photointerrupter may be used. Of course, sensor means other than optical switches can be used.
The present invention can be widely applied as long as the sensor means is such that the analog amount of the output changes between when the detection point is activated and when it is not activated, and even if the detected member is a member other than the shutter blade. No problem. For example, FIG. 5 shows an example in which a transmission type photo interrupter 32 is used to detect that a gear 33 such as a motor pinion has reached a predetermined rotation angle. In such a case, it can be applied as it is.

[0026]

As described above, according to the present invention, the output level of the detection means is preliminarily read prior to the actual position detection operation, and the output level of the sensor means is preliminarily read. As a result, the threshold level of the comparison means is set, so that it is not necessary to adjust the operating point in accordance with the individual difference of the sensor means, and to provide a constant voltage power supply circuit. Even if there is a fluctuation in the performance, the threshold level is automatically corrected for each detection operation, so that the detection operation can be performed without being affected by aging. Moreover, when the load conditions are matched between the pre-light emission and the detection, as in the above-described embodiment, it is also possible to substantially avoid the effect of the power supply level drop due to the load fluctuation.

[Brief description of the drawings]

FIG. 1 is a plan view of a position detection device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example in which the present invention is configured by an analog circuit.

FIG. 3 is a block diagram showing an example of a case where the present invention is processed by software.

FIG. 4 is a flowchart of the embodiment shown in FIG. 3;

FIG. 5 is a perspective view showing another application example of the present invention.

FIG. 6 is a circuit diagram of a conventional device of this type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Shutter blade 10b Light-shielding blade piece 15 Photoreflector 15a Light emitting diode 15b Phototransistor 21 Comparator 22 Capacitor 23 Voltage follower 24 CPU 25 Voltage follower 26, 27 Resistance 29 Analog-digital conversion circuit 30 Interface 31 CPU

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01D 3/00 G01B 11/00-11/30

Claims (4)

(57) [Claims] 1. A sensor having a detection unit along a travel line of a member to be detected, wherein an analog amount of an output changes between when the detection unit operates and when the detection unit does not operate. Holding means for holding ; comparing means for generating a signal when an output level of the sensor means shifts from a non-operating level of the detecting section to a working level with reference to a threshold level; and a holding state of the holding means. Release means for releasing
And forming, in the detected member, a portion that sequentially transitions the detection unit to a first operating state, a non-operating state, and a second operating state when the detected member travels, Corresponding to the holding state of the holding means for holding the output of the sensor means when in the operating state ,
Setting a threshold level of the comparing means, and
Each time one traveling change is completed, the release means
A position detecting device configured to release the holding state . 2. A sensor having a detecting section along a traveling operation line of a blade member for opening and closing an optical path from a subject to an image plane, wherein an analog amount of output changes between when the detecting section is activated and when it is not activated. Means, holding means for holding the output of the sensor means, and a comparison for generating a signal when the output level of the sensor means transitions from a non-operating level to an operating level of the detector with reference to a threshold level. Means for releasing the holding state of the holding means.
And the detecting portion of the first operating state, during running of the blade member
A portion that sequentially transitions to a non-operating state and a second operating state is formed on the blade member, and a holding state of the holding unit that holds an output of the sensor unit when the detecting unit is in the first operating state Corresponding to
Setting a threshold level of the comparing means, and
Each time one traveling change is completed, the release means
A position detecting device configured to release the holding state . 3. The position detecting device according to claim 1, wherein the detected member is operated in accordance with the second operating condition in the first operating state. 4. The position detecting device according to claim 1, wherein the sensor means includes a light emitting unit and a light receiving unit, and an optical path from the light emitting unit to the light receiving unit is determined by the detected member. A position detecting device comprising an optical switch that is opened and closed.