JPH07230031A - Position detector - Google Patents

Abstract

PURPOSE:To instantaneously and accurately detect a lens position by eliminating unnecessary work regardless of motor driving operation or manually driving operation. CONSTITUTION:A potentiometer 4 detects the absolute position of a lens 1 with a contact 4a linked with the lens 1, and generates output consecutively changing in accordance with the position change of the lens 1. A photointerruptor 11 generates a pulse signal in accordance with the moving amount of the lens 1. CPU 6 corrects the output of the potentiometer 4 by means of the output of the photointerruptor 11 and improves linearlity on the output of the potentiometer 4. The CPU 6 sends the corrected output of the potentiometer 4 to the other system 2 a value expressing the position of the lens 1.

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 for outputting the absolute lens position of a camera lens.

[0002]

2. Description of the Related Art Conventionally, in the technical field of cameras, for example, it has been desired to detect the position of a camera lens with high precision, and various techniques for that purpose have been developed and proposed. For example, as shown in FIG.
Japanese Patent Publication No. 10 discloses a technique in which a potentiometer that interlocks with a lens is provided and the lens position is detected by the output voltage of the potentiometer.

Further, as shown in FIG.
Japanese Patent Laid-Open No. 1-292608 discloses a technique in which an encoder that generates a pulse signal corresponding to a lens driving amount is provided, and the lens position is output by adding or subtracting the pulse number of the pulse signal generated by the movement from the initial position.

[0004]

However, according to the technique disclosed in Japanese Patent Publication No. 41-21710, the linearity of the potentiometer is limited to about ± 2% at the time of mass production, and is limited to ± 1% or less. It becomes sorting,
The cost will increase significantly.

In view of the above point, if the cost is suppressed, the accuracy will be about 1/50 of the whole area. Therefore, there is a problem that the accuracy is not improved even if the resolution of the A / D converter is increased. I will end up.

Further, according to the technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 61-292608, 1/10 of the entire area can be easily
Although the detection can be performed with a high resolution of 00 or more, when the motor is disconnected and the manual operation is performed, the circuit is always energized even if the photo interrupter and the slit are interlocked with each other, so that the battery is often consumed.

Further, when the lens is attached or detached, it is necessary to reset the integrated value at the initial position without fail, which gives the user an unpleasant feeling. The present invention has been made in view of the above problems, and an object of the present invention is to detect a lens position instantaneously with high accuracy without performing unnecessary operation regardless of motor drive / manual manual operation. .

[0008]

In order to achieve the above object, the position detecting device according to the first aspect of the present invention corresponds to the absolute position of the lens and continuously changes according to the position change of the lens. And a second encoder for generating a pulse signal according to the amount of movement of the lens.
The output of the encoder and the first encoder is the second
Correction means for correcting the output of the encoder to improve linearity in the output of the first encoder; and output means for outputting the output of the first encoder corrected by the correction means as a value indicating the position of the lens. It is characterized by including.

The position detecting device according to the second aspect is an analog encoder for outputting an output corresponding to the absolute position of the lens as an analog signal, and a pulse signal according to the moving amount of the lens, which is provided in parallel with the analog encoder. Correcting means for correcting the output of the digital encoder and the output of the analog encoder to improve the linearity in the output of the analog encoder, and the output of the analog encoder corrected by the correcting means. Is output as a value indicating the position of the lens.

Further, in the position detecting method according to the third aspect, the linearity of the analog value corresponding to the absolute position of the lens is improved by using the digital value corresponding to the moving amount of the lens, and the corrected analog value is obtained. The value is output as a value indicating the position of the lens.

[0011]

That is, in the position detecting device according to the first aspect of the present invention, the first encoder generates an output corresponding to the absolute position of the lens and continuously changing according to the position change of the lens. Then, the second encoder generates a pulse signal according to the movement amount of the lens. Further, the correction means corrects the output of the first encoder by the output of the second encoder, and improves the linearity in the output of the first encoder. Then, the output means outputs the output of the first encoder corrected by the correction means as a value indicating the position of the lens.

In the position detecting device according to the second aspect, the analog encoder outputs the output corresponding to the absolute position of the lens as an analog signal. Then, the digital encoder is provided alongside the analog encoder and generates a pulse signal according to the amount of movement of the lens. Further, the correction means corrects the output of the analog encoder by the output of the digital encoder, and improves the linearity in the output of the analog encoder. Also,
The output means outputs the output of the analog encoder corrected by the correction means as a value indicating the position of the lens.

Further, in the position detecting method according to the third aspect, the linearity of the analog value corresponding to the absolute position of the lens is improved by using the digital value corresponding to the moving amount of the lens, and the corrected analog value is obtained. The value is output as a value indicating the position of the lens.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a position detection device according to a first embodiment of the present invention. In FIG. 1, the lens 1 is held by a moving lens frame 2, and the lens 1 and the moving lens frame 2 are integrated and are movable in the optical axis direction of incident subject light. And the fixed frame 3
Are provided with stoppers 3a and 3b, and the protrusion provided on the movable lens frame 2 contacts the stoppers 3a and 3b to limit the movable range of the movable lens frame 2.

One end of the potentiometer 4 is connected to the power supply Vcc via the switching transistor Tr1 and the other end is grounded to GND. Then, the contact 4 a that moves integrally with the movable lens frame 2 slides on the potentiometer 4. The contact 4 a is connected to the CPU 6 via the A / D converter 5.

Further, the CPU 6 is connected to the base of the switching transistor Tr1 via a protection resistor R2, and the connecting end of the resistor R2 and the base of the switching transistor Tr1 is a pull-up resistor R1.
It is also connected to the emitter of the switching transistor Tr1 via.

Further, the CPU 6 further includes the CPU 6
It is also connected to a motor driver 8 which receives a command from the motor 9 to drive and control the motor 9, and the motor driver 8 is connected to the motor 9. A slit plate 10 is fixed to the shaft 9a of the motor 9, and when the motor 9 rotates, the slit plate 10 also rotates integrally.

The rotation of the slit plate 10 is detected by the photo interrupter 11, and the photo interrupter 1 is detected.
The analog signal from 1 is converted into a digital signal by the signal processing circuit and output to the CPU 6. That is, when the slit plate 10 rotates, the light flux of the photo interrupter 11 is intermittently shielded, and an impulse signal proportional to the rotation amount is generated as an output of the processing circuit 12.

The shaft 9a of the motor 9 is mechanically coupled to the movable lens frame 2 by a mechanical transmission mechanism (not shown). Further, the EEPROM 7 stores in advance the cumulative number of pulses corresponding to the output of the A / D converter 5.

As described above, in the first embodiment, the photo interrupter 11 generates an output corresponding to the absolute position of the lens 1 and continuously changing according to the position change of the lens 1. The potentiometer 4 generates a pulse signal according to the amount of movement of the lens 1. The CPU 6 corrects the output of the photo interrupter 11 with the output of the potentiometer 4 to improve the linearity of the output of the photo interrupter 11. Then, the CPU 6 outputs the corrected output of the photo interrupter 11 to another system as a value indicating the position of the lens 1.

The stored values in the EEPROM 7 will be described in detail below. FIG. 2 is a diagram showing the relationship between the output of the potentiometer and the lens position. In the first embodiment, the integrated pulse value is approximately 1000 pulses in the entire range due to the nature of the configuration of the slits, gears, etc., and is extremely accurately proportional to the lens movement amount, and should be regarded as approximately the same as the lens position. Since it can be done, it is also written on the lens position.

In FIG. 2, the broken line 11 indicates the target value of the potentiometer, and the solid line 12 indicates the actual value. Considering, for example, the case where the potentiometer output is V0, the lens position becomes S0 in view of the target value, and it deviates from the actual lens position S0 '.

Therefore, the value P0 corresponding to the lens position V0 is stored in the EEPROM 7, and the pulse integrated value P0 corresponding to the correct position S0 'is obtained by referring to the value. Next, FIG. 3 is a diagram showing a state of the table stored in the EEPROM 7.

As shown in the figure, since the A / D converter 5 has, for example, 8 bits, an output from 0 to 255 can be obtained, but since there is a table for all the numerical values,
The corresponding pulse integrated value is obtained as an output.

Hereinafter, referring to the flowchart of FIG.
The method of creating the table shown in FIG. 3 will be described in detail. First, when an initial adjustment instruction is given from the outside, the initial adjustment mode starts (step S101), and the CPU
6 turns on the motor 9 in the retracting direction (step S1)
02). Then, the CPU 6 monitors the pulse generated from the processing circuit 12, and when the pulse disappears for a certain period of time, the CPU 9 considers that it has contacted the stopper 3b and stops the motor 9 (step S104). It is monitored (step S103).

After the motor 9 is stopped, the CPU 6 resets the register for counting the integrated pulse (step S
105), and this time, the motor is turned on in the feeding direction (step S106). At this time, since the CPU 6 covers the time lag of the following processing, the motor 9 is driven at a low speed by duty driving.

Next, when a pulse is generated (step S10)
7) At the same time, the CPU 6 increments the integrated count register (step S108), and at the same time operates the A / D converter 5 to fetch the value (step S10).
9), A / D conversion value and pulse integrated value are set as a CPU 6
It is stored in a RAM (not shown) in the inside (step S110).

This operation is repeated until the pulse disappears (step S111), and when the pulse disappears for a certain time, the CPU 6 stops the motor 9 (step S11).
2). Next, the CPU 6 reads the stored value in the RAM again, calculates the pulse integrated value corresponding to the A / D converted value as the median value of the pulse integrated values, and the A / D converted value 0 from the address 0 to the address 255 of the EEPROM 7 is calculated. The pulse integrated value corresponding to ~ 255 is written (steps S113 and S114).

For example, as shown in FIG. 5, 512 to 519 correspond to the A / D converted value "129". In such a case, the median value "516" is selected and the EEP is selected.
Write to ROM7. In this way, this sequence is completed (step S115).

When the CPU 6 requires the lens position, or when requested by another system, the normally-off switching transistor Tr1 is turned on to set A
After A / D conversion by the / D converter 5, EEP
The integrated pulse number corresponding to the A / D converted value is read out from the ROM 7 and used by itself, or is further converted to another numerical value such as a numerical value or distance information when the lens is a focus lens and output to another system.

According to the first embodiment described above, A /
The integrated pulse value corresponding to all D converted values is stored in the EEPROM 7.
Therefore, the lens position can be output accurately and at high speed. Further, since the lens is driven at a low speed at the time of adjustment, there is no problem that the processing is not in time.

Next, a lens position detecting device according to the second embodiment of the present invention will be described. The above-mentioned first embodiment is A
The corresponding pulse integration number is E for all the / D converted values.
Although stored in the EPROM 7, the second embodiment is characterized in that the pulse integrated value is stored only for a predetermined A / D value.

FIG. 6 is a diagram showing a method of calculating the pulse integration number in the second embodiment. The figure is an enlarged view between the points qm1 and qm2 shown in FIG. When the potentiometer outputs VO, the pulse integrated value corresponding to this value is not stored. Instead, the values corresponding to the points qm1 and qm2 sandwiching this are stored. Generally, the resistance of the potentiometer has a high linearity at a close point, and there is no problem even if it is regarded as a straight line. In this case, interpolation is performed with a straight line. Therefore, it can be calculated by the following equation.

[0034]

[Equation 1]

Next, FIG. 7 is a diagram showing an example of numerical values when 9 sets of data sets of A / D values and pulse integrated values are stored when the A / D converter is 8 bits. This may be substituted into the above formula. Regarding the initial adjustment, writing to the RAM may be performed only when the A / D value is 9 points.

As described above, according to the second embodiment, it is possible to use a RAM or an EEPROM having a small storage capacity, and it is possible to reduce the size and cost of each memory. Also, the output accuracy of the lens position can be made close to that of the first embodiment.

In the above first and second embodiments, the absolute position encoder may be another sensor such as PSD other than the potentiometer, and the pulse encoder may be other than the photo interrupter such as a magnetic sensor such as a ferromagnetic film resistance element. But it's okay.

The output indicating the lens position may also be of another type such as the subject distance other than the pulse number, the reciprocal thereof, and the emitted light amount of the variable light emission strobe. Further, if the lens is a variator of a zoom lens, the focal length or the like may be used.

The mounting position of the pulse encoder is not the shaft of the motor, but an intermediate gear or the moving lens frame 2.
Good choice. Then, during the cumulative pulse count, it is possible to add or subtract the gear backlash pulse to obtain a more accurate value.

Furthermore, the pulse integration number corresponding to the A / D converted value may be the maximum value or the minimum value instead of the median value.
It is also possible to set the maximum value and the minimum value only when the D conversion value is maximum or minimum (both ends).

As described in detail above, in the lens position detecting device of the present invention, the absolute position of the lens can be instantaneously detected with high accuracy without the need to reset the initial position of the lens during use or to always energize, and the cost can be suppressed. You can

According to the embodiment of the present invention described in detail above, the following constitution can be obtained. That is, (1) a first encoder that generates an output that corresponds to the absolute position of the lens and that continuously changes according to the position change of the lens; and a second encoder that generates a pulse signal according to the amount of movement of the lens. An encoder, a storage unit that stores the pulse integrated amount from one end of the movable range of the lens by the second encoder corresponding to the position of the lens where the first encoder shows a predetermined value, and the output of the first encoder. Output means for detecting and outputting a pulse integrated amount by the second encoder or a value corresponding to the integrated amount as a value indicating the position of the lens by referring to the stored value of the storage means. . (2) In (1) above, the first encoder is a potentiometer. (3) In (1) above, the stored value of the storage means is
It is an intermediate value of a plurality of integrated amounts corresponding to the predetermined value of the first encoder. (4) In the above (1), further move the lens within the movable range 2
It has stopper means for stopping at one end face. (5) In the above (1), the outputs of the first encoder and the second encoder are stored in the storage means in a corresponding state by the following procedure.

(A) The lens is moved from one end to the other end of the movable range, (b) the output pulse of the second encoder is integrated while counting the output of the first encoder, and (c) The accumulated pulses of the second encoder corresponding to the output of the first encoder are sequentially stored, and (d)
When the lens reaches the other end, the movement of the lens is stopped. (6) In the above (5), the moving speed is slower than during use during storage operation in the storage means. (7) In (1) above, the set of numerical values stored in the storage means is a plurality of discrete point values, and the output means corresponds to the first encoder value sandwiching the output value of the first encoder. The integrated pulse amount of the second encoder is referred to, and the integrated pulse amount obtained by interpolating the value of the first encoder is output as a value indicating the position of the lens. (8) An analog encoder that outputs an output corresponding to the absolute position of the lens as an analog signal, a digital encoder that is installed in parallel with the analog encoder and that generates a pulse signal according to the movement amount of the lens, and an output of the analog encoder Is corrected by the output of the digital encoder to improve the linearity in the output of the analog encoder, and the output of the analog encoder corrected by the correction unit is output as a value indicating the position of the lens. Means for informing the initial position of the lens, and the initial position of the lens in the digital encoder corresponding to the position of the lens at which the analog encoder shows a predetermined value. Storage means for storing the pulse integrated amount from the position The a, is converted to a pulse integrated amount the output of the analog encoder with reference to the stored value of the storage means.

[0044]

As described above, according to the present invention, it is possible to provide a position detecting device capable of instantaneously detecting the lens position with high accuracy without performing unnecessary operation regardless of motor driving / manual manual operation. .

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a position detection device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an output of the potentiometer and a lens position according to the first embodiment.

FIG. 3 is a diagram showing a state of a table stored in an EEPROM 7 according to the first embodiment.

4 is a flowchart showing a method of creating the table shown in FIG.

FIG. 5 is a table showing a pulse integrated value corresponding to an A / D converted value and an EEPROM write value corresponding to both values.

FIG. 6 is a diagram for explaining a method of calculating a pulse integration number in the second embodiment.

FIG. 7: When the A / D converter is 8 bits, 9 sets of A
It is a figure which shows the numerical example at the time of storing the data set of / D value and pulse integrated value.

FIG. 8 is a diagram showing a configuration of a position detection device according to a conventional technique.

FIG. 9 is a diagram showing a configuration of a position detection device according to a conventional technique.

[Explanation of symbols]

1 ... Lens, 2 ... Lens frame, 3 ... Fixed frame, 4 ... Potentiometer, 5 ... A / D converter, 6 ... CPU, 7 ... E
EPROM, 8 ... Motor driver, 9 ... Motor, 10 ...
Slit plate, 11 ... Photo interrupter, 12 ... Processing circuit.

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[Procedure amendment]

[Submission date] November 1, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

As described above, in the first embodiment, the potentiometer
The rheometer 4 corresponds to the absolute position of the lens 1 and generates an output that continuously changes according to the position change of the lens 1. The photo interrupter 11 generates a pulse signal according to the amount of movement of the lens 1. CPU6 the above potentiometer
The output of Shometa 4 corrected by the output of the photo interrupter 11, to improve the linearity at the output of the potentiometer 4. Then, the CPU 6 outputs the corrected output of the potentiometer 4 to another system as a value indicating the position of the lens 1.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03B 3/10 13/34 G03B 3/10

Claims (3)

[Claims] 1. A first encoder for generating an output corresponding to an absolute position of a lens and continuously changing in accordance with a change in the position of the lens, and a second encoder for generating a pulse signal in accordance with a moving amount of the lens. An encoder, a correction unit that corrects the output of the first encoder by the output of the second encoder, and improves linearity in the output of the first encoder; and an output of the first encoder that is corrected by the correction unit. An output unit that outputs a value indicating the position of the lens, the position detecting device. 2. An analog encoder that outputs an output corresponding to the absolute position of the lens as an analog signal, a digital encoder that is provided in parallel with the analog encoder and that generates a pulse signal according to the movement amount of the lens, and the analog encoder. Is corrected by the output of the digital encoder to improve the linearity in the output of the analog encoder, and the output of the analog encoder corrected by the correction means is output as a value indicating the position of the lens. A position detecting device comprising: an output unit. 3. The linearity of an analog value corresponding to the absolute position of the lens is improved by using a digital value corresponding to the movement amount of the lens, and the corrected analog value is output as a value indicating the position of the lens. A position detecting method comprising: