JPH0961697A - Method and device for detecting position of movement limit of lens and automatic focusing device using the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cost by restraining a lag in the case of detecting that a lens reaches a movement limit position without specially forming backlash between a motor and the moving part of an encoder. SOLUTION: The lens is driven and moved by a motor 21 actuated in response to a driving command including a rotating direction command. The encoder 23 is provided with a rotating plate 24 set to be interlocked with the rotary shaft 21a of the motor 21 without the backlash substantially, and outputs a rotating direction signal in accordance with the rotating direction of the plate 24. Whether or not the rotating direction of the plate 24 of the encoder 23 corresponds to the rotating direction of the motor 21 shown by the rotating direction command is decided based on the rotating direction signal. A situation that the lens reaches the movement limit position 13 detected by deciding that they do not correspond to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a movement of a lens, which is detected by a lens driven by a motor which operates in response to a drive command including a rotation direction command, to reach a movement limit position of the lens. The present invention relates to a limit position detecting method and device, and an autofocus device using the same.

[0002]

2. Description of the Related Art In recent years, in cameras and video cameras,
An autofocus device is used. Such an autofocus device is generally required to detect a focus state of a lens driven by a motor and move by a well-known detection unit and to bring the lens into a focus state based on the detection signal. The rotation direction and the rotation amount of the motor are calculated. Then, by an encoder having a rotary plate provided so as to interlock with the rotary shaft of the motor,
A rotation amount signal indicating the rotation amount of the rotating plate is obtained, and based on the rotation amount signal, the motor is controlled so that the rotation position of the motor becomes a target rotation position determined by the calculated rotation direction and rotation amount. Supply a drive command. As a result, the lens is moved to a predetermined position and an in-focus state is automatically obtained.

In such an autofocus device, the target rotational position may exceed the position corresponding to the movement limit position of the lens. In this case, if it is not detected that the lens has reached the movement limit position, the lens moves in that direction even though the lens has reached the movement limit position and the lens is physically immovable. The drive voltage continues to be applied to the motor in the direction.

Therefore, conventionally, when the lens reaches the movement limit position, the rotation of the motor mechanically stops,
As a result, the rotation of the rotary plate of the encoder is stopped, and as a result, a pulse signal cannot be obtained from the encoder, and when a drive command is given to the motor, a predetermined number of signals from the encoder are output within a predetermined time. Whether or not the pulse signal was obtained was determined, and by determining that the pulse signal was not obtained, it was detected that the lens reached the movement limit position.

In this case, when the rotary shaft of the motor and the rotary plate of the encoder are directly connected, when the lens reaches the movement limit position, the encoder does not move even though the lens does not move. The rotary plate vibrates due to the spring force of the spring element existing between the motor and the rotary plate of the encoder, and the pulse signal is continuously obtained from the encoder during the vibration. Therefore, even when the lens reaches the movement limit position, it cannot be detected that the lens reaches the movement limit position while the rotary plate of the encoder is vibrating, and overcurrent continues to flow to the motor during that time. Will end up. That is, the delay in detecting the arrival of the lens at the movement limit position becomes large.

Therefore, conventionally, a relatively large backlash is intentionally provided between the rotary shaft of the motor and the rotary plate of the encoder so that the rotary plate of the encoder vibrates when the lens reaches the movement limit position. I was trying to stop without doing it.

An example of such a conventional mechanism will be described with reference to FIG. FIG. 5 is a perspective view schematically showing the relationship between a conventional motor and encoder.

As shown in FIG. 5, the rotary shaft 1a of the motor 1
The gear 2 is fixed to the. A gear 3 is meshed with the gear 2, and a shaft 5 fixed to the gear 3 has a gear 5 fixed to a moving mechanism (not shown) for moving the lens. A transmission member 6 for forming a backlash is also fixed to the rotary shaft 1a of the motor 1. Transmission member 6
Has two engaging portions 6a arranged at a large interval in the rotation direction. In FIG. 5, reference numeral 7 denotes a backlash-forming passive member that is rotatably provided around the rotation axis of the motor 1, and the passive member 7 has two engaging members that are formed at large intervals in the rotation direction. It has a mating portion 7a, and is arranged so as to engage with the two engaging portions 6a at a distance. The rotary plate 9 of the encoder 8 is fixed to the passive member 7. A large number of slits 9a extending in the radial direction are formed on the rotary plate 9 at equal intervals in the circumferential direction. Further, the encoder 8 includes a light receiver / receiver 10 provided on the fixed side for irradiating the rotating plate 9 with light and receiving the reflected light, and a pulse signal corresponding to the rotation of the rotating plate 9 is received / received. 10 (in particular, its light receiving portion).

When the mechanism shown in FIG. 5 is adopted, when the motor 1 is operated and the rotary shaft 1a rotates, the gears 2,
The lenses 3 and 5 rotate, whereby the lens is moved via the moving mechanism (not shown). At this time, the engaging portion 6a of the transmission member 6 contacts the passive member 7a, and the rotary plate 9 of the encoder 8 rotates as the motor 1 rotates. Then, when the lens reaches the movement limit position, the gears 5, 3, 2 stop via the movement mechanism, and the rotation of the motor 1 mechanically stops. At this time, the transmission member 6 reciprocally vibrates in the rotation direction due to the spring force of the rotating shaft 1a and the like. However, since the backlash is formed between the transmission member 6 and the passive member 7, the vibration of the transmission member 6 is not transmitted to the passive member 7, and the passive member 7 mechanically stops the rotation of the motor 1. At this time, it stops without vibrating, and accordingly, the rotary plate 9 of the encoder 8 stops without vibrating. Therefore, when the drive command is given to the motor 1, the encoder 8
If it is determined that the lens has reached the movement limit position by determining whether or not a predetermined number of pulse signals have been obtained from it, it is detected that the lens has reached the movement limit position. It takes a long time to do so, and the problem that overcurrent continues to flow to the motor does not occur.

[0010]

However, in the above-mentioned conventional method for detecting the arrival of the lens at the movement limit position (lens movement limit position detection method), as described above, the lens movement limit position is detected. In order to prevent the arrival detection delay, it is necessary to form a relatively large backlash between the motor 1 and the rotary plate 9 of the encoder 8.
Since the passive member 7 is required, the cost increase cannot be avoided.

The present invention has been made in view of such circumstances, and it is possible to detect the arrival of the lens at the movement limit position without forming a backlash between the motor and the moving portion of the encoder. An object of the present invention is to provide a lens movement limit position detection method and device, which can reduce delay and cost reduction, and an autofocus device using the same.

[0012]

In order to solve the above problems, the lens movement limit position detecting method according to the first aspect of the present invention is driven by a motor which operates in response to a drive command including a rotational direction command. Is a lens movement limit position detecting method for detecting that a lens that moves by moving reaches a movement limit position of the lens, and is provided so as to be interlocked with a rotation axis of the motor substantially without backlash. An encoder that has a moving section and outputs a traveling direction signal according to a traveling direction of the moving section is used, and the traveling direction of the moving section of the encoder is indicated by the rotation direction command based on the traveling direction signal. It is determined whether or not the lens has reached the movement limit position by determining whether or not it corresponds to the rotation direction of 1. and determining that they do not correspond to each other.

In the lens movement limit position detecting device according to the second aspect of the present invention, the lens which is driven by the motor which operates in response to the drive command including the rotation direction command to move is set to the lens movement limit position. A lens movement limit position detecting device for detecting arrival, which has a moving part provided so as to be interlocked with a rotating shaft of the motor substantially without backlash, and is adapted to a traveling direction of the moving part. An encoder for outputting a traveling direction signal, and based on the traveling direction signal, it is determined whether or not the traveling direction of the moving portion of the encoder corresponds to the rotation direction of the motor indicated by the rotation direction command. And a determination unit that generates a detection output when the above does not correspond.

An autofocus device according to a third aspect of the present invention shows a motor that operates in response to a drive command including a rotation direction command, a lens that is driven and moved by the motor, and a focus state by the lens. A focus state detection unit that outputs a focus state detection signal, and a moving unit that is provided so as to interlock with the rotation shaft of the motor substantially without backlash, and a progress amount signal that indicates a progress amount of the moving unit. And an encoder that outputs a traveling direction signal indicating a traveling direction of the moving unit, and a rotation direction and a rotation amount of the motor required to bring the lens into a focused state, based on the focus state detection signal. The rotation position of the motor is determined by the rotation direction and the rotation amount calculated by the calculation unit based on the calculation unit and the progress amount signal. Means for supplying the drive command to the motor so as to be at the target rotation position, and based on the traveling direction signal, the traveling direction of the moving portion of the encoder is the rotation direction of the motor indicated by the rotation direction command. The drive command when it is determined that the traveling direction of the moving portion of the encoder does not correspond to the rotation direction of the motor indicated by the rotation direction command And a means for stopping the rotation direction or inverting the rotation direction command.

According to the first to third aspects, the lens is driven by the motor to move, and the moving part of the encoder is provided so as to interlock with the rotary shaft of the motor substantially without backlash. Therefore, a spring element exists between the motor and the moving part of the encoder and between the motor and the lens because the transmission member or mechanism therebetween has finite rigidity. Therefore, when the lens reaches the movement limit position, the moving portion of the encoder vibrates due to the spring element. That is, the moving part of the encoder sequentially reverses the traveling direction, and the amplitude thereof gradually decreases. In the conventional case described above, it is possible to detect that the lens has reached the movement limit position only after the vibration of the moving portion of the encoder has stopped. On the other hand, in the first to third aspects,
The encoder detects the traveling direction of the moving part of the encoder, and the determining means determines whether or not this traveling direction corresponds to the rotation direction of the motor indicated by the rotation direction command to the motor, and determines that the two do not correspond. Detects that the lens has reached the movement limit position. Therefore, the arrival of the lens at the movement limit position is detected at the initial stage of the vibration of the moving portion of the encoder. Therefore, according to the first to third aspects, even when the backlash is not substantially formed between the moving portion of the encoder and the motor, the detection of the lens reaching the movement limit position is detected. Delay is reduced.

According to the first to third aspects, since the backlash is not substantially formed between the moving portion of the encoder and the motor, the transmission member 6 and the passive member 7 in FIG. No special member for forming the backlash is required, and the cost can be reduced accordingly.

In the third aspect, an autofocus device is constructed by using the first or second aspect,
When the arrival of the lens at the movement limit position is detected, the drive command to the motor is stopped or the rotation command to the motor is reversed. Therefore, according to the third aspect, it is possible to prevent the situation where the overcurrent continues to flow to the motor.

[0018]

DETAILED DESCRIPTION OF THE INVENTION An autofocus device according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing an autofocus device according to this embodiment. FIG. 2 is a schematic perspective view specifically showing the relationship between the motor 21 and the encoder 23 in the present embodiment. FIG. 3 is a conceptual diagram showing the relationship between the motor 21, the lens 22 and the encoder 23 in the present embodiment. FIG. 4 is a flowchart showing an example of the operation of the control unit 41 in this embodiment.

As shown in FIG. 1, the autofocus device according to the present embodiment has a motor 21, a lens 22 driven by the motor 21 to move, and a rotary shaft 2 of the motor.
1a has a rotary plate 24 as a moving part provided so as to interlock substantially without backlash.
And an encoder 23 that outputs a rotation amount signal that indicates the rotation amount (that is, the amount of progress) and a rotation direction signal that indicates the rotation direction (that is, the direction of travel) of the rotary plate 24.

In the present embodiment, as shown in FIG. 2, the gear 27 is fixed to the rotary shaft 21a of the motor 21.
A gear 28 is meshed with the gear 27, and a shaft 29 fixed to the gear 3 is provided with a gear 30 that is transmitted to a moving mechanism (not shown) that moves the lens 22 (moves in the left-right direction in FIG. 3). It is fixed. The rotary plate 24 of the encoder 23 is directly connected to the rotary shaft 21a of the motor 21. However, the rotary plate 24 is the rotary shaft 21a of the motor.
It suffices if they are provided so as to interlock with each other substantially without backlash, and a transmission member may be interposed between the rotary shaft 21a of the motor and the rotary plate 24. For example, if the rotary plate 24
It may be fixed at 9.

With the above construction, as shown in FIG. 3, the rotary shaft 21a, the gears 27, 28 and 30, the shaft 29, and the moving mechanism between the motor 21 and the lens 22 have finite rigidity. Therefore, the spring element 31 is present. Further, since the rotary shaft 21a has a finite rigidity between the motor 21 and the rotary plate 24 of the encoder 23,
The spring element 32 will be present. In addition, 3 in FIG.
Reference numeral 3 shows one movement limit position of the lens 22 by the movement mechanism. Although not shown in FIG. 3, the other movement limit position also exists on the left side in FIG.

Therefore, the lens 22 moves to the movement limit position 3
When it reaches 3, the rotary plate 24 of the encoder 23 vibrates due to the spring force of the spring elements 31 and 32, and the rotation direction of the rotary plate 24 is sequentially reversed according to the vibration, and its amplitude gradually decreases. .

As shown in FIG. 2, a large number of radially extending slits 9a are formed on the rotary plate 24 of the encoder 23 at equal intervals in the circumferential direction. Further, in the present embodiment, the encoder 23 is provided on the fixed side that irradiates the rotating plate 24 with light and receives the reflected light.
It is equipped with two light receivers / receivers 25, 26. Light receiver / receiver 25,
26 are arranged so that their detection positions differ from each other by a phase angle of 90 °, and pulse signals corresponding to the rotation of the rotary plate 24 are different in phase from the light receivers / receivers 25 and 26 (in particular, their light receiving portions) by 90 °. can get. Therefore, a rotation amount signal indicating the rotation amount of the rotary plate 24 can be obtained by counting the number of pulses of the pulse signal from the light emitting / receiving device 25 or the light receiving / emitting device 26, and the pulse signal from the light receiving / emitting device 25 can be obtained. A rotation direction signal indicating the rotation direction of the rotary plate 24 can be obtained from the phase difference of the pulse signals from the light receiver / receiver 26. In the present embodiment, although not shown in the drawing, the encoder 23 also has a pulse processing circuit that processes the pulse signals from the light receivers / receivers 25 and 26 to obtain the rotation amount signal and the rotation direction signal. There is. Although a rotary encoder is used as the encoder 23 in the present embodiment, a linear encoder or the like may be used.

Further, the autofocus device according to the present embodiment, as shown in FIG. 1, has a well-known focus detection section 40 for outputting a focus state detection signal indicating the focus state of the lens 22, and an autofocus from the outside. In response to the start command, the focus detection unit 40
Focus state detection signal from encoder and encoder 23
A drive command including a rotation direction command is output based on the rotation amount signal and the rotation direction signal from the control unit 41 for realizing the autofocus operation, and the motor 21 according to the drive command from the control unit 41. And a motor drive circuit 42 for operating the motor 21 by applying a drive voltage thereto.

The control section 41 is constructed by using, for example, a microcomputer, and as will be apparent from the following description, the lens 22 is brought into the focused state based on the focus state detection signal from the focus state detection section 40. The rotation position of the motor 21 is calculated on the basis of the function as a calculation means for calculating the rotation direction and the rotation amount of the motor 21 (step S5 in FIG. 4) and the rotation amount from the encoder 23. The function as means for supplying a drive command including a rotation direction command to the drive circuit 42 so that the target rotation position is determined by the rotation direction and the rotation amount (steps S6 and S10 in FIG. 4), and the encoder 23 Based on the rotation amount signal, it is determined whether the rotation direction of the rotary plate 24 of the encoder 23 corresponds to the rotation direction of the motor 21 indicated by the rotation direction command. Functions as a constant determining means (FIG. 4
Step S13) and the rotary plate 24 of the encoder 23
When it is determined that the rotation direction of the motor does not correspond to the rotation direction of the motor 21 indicated by the rotation direction command, the function as means for inverting the rotation direction command (step S in FIG. 4).
16) and bear.

Next, regarding an example of the operation of the control unit 41,
A specific description will be given with reference to the flowchart shown in FIG.

When the control section 41 receives an autofocus start command from the outside, the control section 41 starts its operation. First, in step S1.
A predetermined register (not shown) A incorporated in the control unit 1 by
Is initialized to 0. Next, the control unit 41 performs step S
At 2, the encoder 23 is initialized. Specifically, in step S2, the pulse count value of the pulse processing circuit of the encoder 23 is set to zero.

Thereafter, the control unit 41, in step S3,
The focus state detection signal from the focus state detection unit 40 is fetched, and in step S4, it is determined whether or not it is in the defocus state based on the focus state detection signal.
If it is determined in step S4 that the focus state is not the defocus state, that is, the focus state, the control unit 41 ends the focus operation. In this case, the lens 22 has been in the focus position from the beginning.

On the other hand, if it is determined in step S4 that the lens 22 is in the defocused state, then in step S5, based on the focus state detection signal fetched in step S3, the motor required to bring the lens 22 into the focused state is selected. A rotation amount (drive command amount) and a rotation direction (drive command direction) are calculated.

Next, in step S6, the control section 41 applies a drive voltage to the motor 21 via the drive circuit 42 so that the motor 21 rotates in the drive command direction. That is, the control unit 41 gives the drive circuit 42 a drive command including a rotation direction command for rotating the drive circuit 42 in the drive command direction. The application of the drive voltage to the motor 21 is continued until step S8 described later.

Next, in step S7, it is determined whether or not a predetermined number of the pulse signals are obtained from the encoder 23 within a predetermined time after step S6, that is, the motor 21 starts to rotate after applying the drive voltage to the motor 21. Or not. In this step S7, when the lens 22 is at one of the movement limit positions from the beginning, depending on the focus state at the time of step S3, the drive command direction calculated in step S5 is set to the direction to move beyond the movement limit position. This is because it may be shown. However, if such a situation cannot occur, step S7 may be deleted and the process may move from step S6 to step S9.

In step S7, the encoder 2
If it is determined from 3 that the predetermined number of pulse signals have not been obtained, the control unit 41 sets the applied voltage of the motor 21 to zero via the motor drive circuit 42 in step S8, and ends the autofocus operation. In this case, it means that the focus state could not be set.
A signal indicating that fact may be output, and this signal may be used to display the fact on a display not shown.

On the other hand, when a predetermined number of the pulse signals are obtained from the encoder 23 within the predetermined time, the control unit 41
In step S9, the rotation amount signal from the encoder 23 is fetched, and in step S10, it is determined whether or not the motor rotation amount signal fetched in step S9 matches the drive command amount calculated in step S5. If they match,
Since the lens 22 has moved to the position where the lens 22 is in the focus state, the control unit 41 sets the voltage applied to the motor 21 to zero in step S8, and ends the autofocus operation. Thereby, the focus state is obtained. On the other hand, if it is determined in step S10 that they do not match,
Move to step S11.

In step S11, the control unit 41
It is determined whether or not the rotation direction determination suspension period started in step S17 described later is in progress. If it is during the motor rotation direction determination suspension period, the process returns to step S9. If it is not during the motor rotation direction determination suspension period, the control unit 41 controls step S1.
In step 2, the rotation direction signal from the encoder 23 is fetched and the process proceeds to step S13.

In step S13, the control section 41 determines whether the rotation direction of the rotary plate 24 of the encoder 23 matches the rotation direction of the motor 21 indicated by the drive command direction, based on the rotation direction signal fetched in step S12. It is determined whether or not the lens 22 has reached the movement limit position. As described above, when the lens 22 reaches the movement limit position, the encoder 23 is activated by the spring elements 31 and 32.
Since the rotating plate 24 of FIG. 3 vibrates and the rotating direction of the rotating plate 24 is sequentially reversed, it is determined in step S13 that they do not match each other. The arrival will be detected. Therefore, the delay in detecting the arrival of the lens 22 at the movement limit position is small.

If it is determined in step S13 that they do not match (that is, if it is determined that the lens 22 has not reached the movement limit position), the process returns to step S9 and the above-described processing is repeated. On the other hand, if it is determined that they match in step S13 (that is, if it is determined that the lens 22 has reached the movement limit position), the process proceeds to step S14.

In step S14, the control unit 41 sets the content of register A, which was set to 0 in step S1, by 1 to the new content of register A. Since the content of the register A is updated to the content obtained by adding 1 in step S14 after step S13, the lens 2
2 indicates the number of times 2 has reached the movement limit position (= the number of reversals of the motor 22-1).

Next, in step S15, the control section 41
It is determined whether the content of the register A has reached a predetermined set value. This set value determines the number of times of reversal of the motor 22 (set value -1 = number of times of reversal), and can be set to an arbitrary value of 1 or more. When it is determined in step S15 that the set value has been reached, the applied voltage of the motor 21 is set to zero in step S8, and the autofocus operation ends. In this case, since the focus state could not be achieved, for example, a signal indicating that fact may be output, and the fact may be displayed on a display device (not shown) using this signal.

On the other hand, if it is determined in step S15 that the set value has not been reached, the drive command direction of the motor 21 is reversed, the rotation direction determination suspension period is started in step S17, and the process returns to step S6. When the process returns to step S6 via step S16, in step S6, a drive voltage is applied to the motor 21 via the drive circuit 42 so that the motor 21 rotates in the drive command direction inverted in step S15. To do.

In step S17, the rotation direction determination stop period is started, and in step S11 it is determined whether or not it is the rotation direction determination stop period. If it is the rotation direction determination stop period, step S12 is performed without proceeding to step S12. The reason for returning to S9 is as follows. That is,
When the motor 21 is reversely driven in step S6 via step S16, the rotary plate 24 of the encoder 23 continues to vibrate even after that. Therefore, when the vibration continues, step S13 is performed. If the above process is performed, the motor 21 causes hunting. Therefore, in order to prevent this situation, steps S11 and S17 are performed in this embodiment. The time during which the vibration continues may be obtained in advance and used as the length of the rotation direction determination suspension period.

According to the autofocus device according to the present embodiment described above, since no backlash is formed between the rotary plate 24 of the encoder 23 and the motor 21 unlike the conventional case, the transmission member 6 in FIG. And passive member 7
No special member for forming the backlash is required, and the cost can be reduced accordingly. Then, even when no backlash is formed between the rotary plate 24 of the encoder 23 and the motor 21, the arrival of the lens 21 at the movement limit position is detected at the initial stage of the vibration of the rotary plate 24 of the encoder 23. Therefore, the delay in detecting the arrival of the lens 21 at the movement limit position becomes small. Further, in the present embodiment, when the arrival of the lens at the movement limit position is detected (when it is determined as “NO” in step S13), the drive command to the motor is stopped (step S8) or Since the rotation command to the motor is reversed (step S16), it is possible to prevent the situation where the overcurrent continues to flow to the motor 21.

The configuration shown in FIGS. 2 and 3 and step S13 in the flow chart shown in FIG.
A lens movement limit position detecting device according to an embodiment of the present invention is configured, and this detecting device constitutes a part of the autofocus device according to the above-described embodiment.

Although the autofocus device according to one embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

For example, in the flowchart shown in FIG. 4, when the set value in step 15 is set to 1 (that is, when the reaching of the movement limit position of the lens 21 is detected once, the reversing operation of the motor 21 is not performed. When stopping the motor 21), steps S1, S11,
This is equivalent to the removal of S14 to S17.

Further, in the flow chart shown in FIG. 4, steps S16 and S17 are removed, and step S1
If the content of the register A has not reached the set value in 5, the process may proceed to step S2.

[0047]

As described above, according to the present invention,
Without specially forming a backlash between the motor and the moving part of the encoder, the delay in detecting the arrival of the lens at the movement limit position can be reduced and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an autofocus device according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view specifically showing a relationship between the motor and the encoder in the embodiment.

FIG. 3 is a conceptual diagram showing a relationship among a motor, a lens, and an encoder in the above embodiment.

FIG. 4 is a flowchart showing an example of the operation of the control unit in the above embodiment.

FIG. 5 is a schematic perspective view specifically showing a relationship between a motor and an encoder according to a conventional technique.

[Explanation of symbols]

 21 motor 21a rotary shaft 22 lens 23 encoder 24 rotary plate 25, 26 light receiver / receiver 31, 32 spring element 33 movement limit position 40 focus state detection unit 41 control unit 42 motor drive circuit

Claims (3)

[Claims] 1. A lens movement limit position detection method for detecting that a lens driven by a motor that operates in response to a drive command including a rotation direction command has reached a movement limit position of the lens. An encoder that has a moving portion provided so as to interlock with the rotating shaft of the motor substantially without backlash and outputs a traveling direction signal according to the traveling direction of the moving portion. On the basis of the above, it is determined whether or not the traveling direction of the moving portion of the encoder corresponds to the rotation direction of the motor indicated by the rotation direction command, and it is determined that the two do not correspond, whereby the lens moves A lens movement limit position detection method characterized by detecting that the lens has reached a limit position. 2. A lens movement limit position detecting device for detecting that a lens which is driven by a motor which operates in response to a drive command including a rotation direction command to move reaches a movement limit position of the lens. An encoder that has a moving portion provided so as to interlock with the rotating shaft of the motor substantially without backlash, and outputs a traveling direction signal according to the traveling direction of the moving portion; Based on this, it is determined whether or not the traveling direction of the moving portion of the encoder corresponds to the rotation direction of the motor indicated by the rotation direction command, and a determination unit that generates a detection output when the two do not correspond, A lens movement limit position detecting device characterized by being provided. 3. A motor that operates in response to a drive command including a rotation direction command, a lens that is driven by the motor to move, and a focus state detection unit that outputs a focus state detection signal indicating a focus state by the lens. A moving amount signal indicating a moving amount of the moving unit and a moving direction indicating a moving direction of the moving unit, and a moving unit provided so as to interlock with a rotating shaft of the motor substantially without backlash. An encoder that outputs a signal, a calculation unit that calculates a rotation direction and a rotation amount of the motor necessary for the lens to be in a focus state based on the focus state detection signal, and based on the progress amount signal Supplying the drive command so that the rotation position of the motor becomes a target rotation position determined by the rotation direction and the rotation amount calculated by the calculation means. Means for determining whether or not the traveling direction of the moving portion of the encoder corresponds to the rotation direction of the motor indicated by the rotation direction command, based on the traveling direction signal, and the determination means. A means for stopping the drive command or reversing the rotation direction command when it is determined that the traveling direction of the moving portion of the encoder does not correspond to the rotation direction of the motor indicated by the rotation direction command, An autofocus device characterized by being equipped.