JP5430231B2 - Imaging device - Google Patents

Description

  The present invention relates to a photographing apparatus that uses a stepping motor to drive a movable part such as a focus lens.

  A stepping motor (also referred to as a pulse motor) is a motor configured to drive only a predetermined rotation angle (referred to as a step angle or the like) in response to a pulse input. Such a stepping motor can realize accurate position control with a relatively simple circuit configuration, and is therefore used in various devices in which positioning accuracy is important. For example, in Patent Document 1, a stepping motor is used to drive a scanning unit in a scanner device such as a digital copying machine. And in patent document 1, in order to detect the scanning position of a scanning part, the rotary body which has the slit hole of a several different space | interval is used as an encoder, and the rotation direction and rotational speed of a stepping motor are detected by this rotary body. Thus, the position of the scanning unit is controlled.

  Here, even in a stepping motor, a step-out may occur due to a load fluctuation or the like generated due to the influence of a disturbance or the like. In order to detect such a step-out, in Patent Document 1, an abnormal operation such as a step-out can be detected from the intervals of a plurality of encoder signals (slit signals) read corresponding to a plurality of slit holes having different intervals. I am doing so.

JP-A-5-63911

  In Patent Document 1, a stepping motor is used to drive a scanning unit of a scanner device. For this reason, the stepping motor is driven at a predetermined constant constant speed. Therefore, the waveform of the encoder signal becomes stable and it is easy to detect an abnormality.

  However, the stepping motor is not necessarily driven at a unique constant speed. For example, when a stepping motor is used to drive a focus lens in a photographing apparatus such as a camera, it is necessary to drive the stepping motor at a constant speed in various speed ranges from the lowest speed to the highest speed. In this case, on the high speed side, there is a possibility that the load to be driven fluctuates due to factors such as posture and temperature, thereby causing a step-out due to insufficient torque of the stepping motor. On the low speed side, the stepping motor is oscillating and the output signal waveform of the encoder tends to be disturbed. If the output signal waveform becomes distorted, the encoder output signal waveform may become a patterned waveform that looks like normal operation, and there is some abnormality in the stepping motor from such output signal waveform. It is difficult to detect what has occurred.

  In addition, since the stepping motor in Patent Document 1 is provided in a housing that is not easily affected by disturbance, stable operation is easily obtained. On the other hand, for example, when a stepping motor is used to drive the focus lens of the photographing apparatus, the stepping motor is not necessarily provided at a position that is not easily affected by disturbance. For example, there are many cases where the focus ring is exposed to the outside. In such a case, there is a high possibility that the stepping motor will step out due to the user accidentally touching the focus ring.

  The present invention has been made in view of the above circumstances, and reliably detects abnormal operation of a stepping motor even when it is susceptible to disturbances or when the stepping motor is driven in a plurality of speed regions. An object of the present invention is to provide a photographing apparatus capable of performing the above.

In order to achieve the above object, the imaging apparatus of the first aspect of the present invention is a stepping motor that is rotationally driven in accordance with a pulse signal input in units of one step and drives a movable part of the imaging apparatus by the rotational drive. And a width corresponding to the driving amount of one step of the stepping motor as one unit, and a slit hole having a width that is an integral multiple of the one unit, and two or more types of slit holes having different widths are formed, A rotating body that rotates as the stepping motor rotates, a reading unit that reads the presence or absence of the slit hole and outputs a signal indicating the presence or absence of the slit hole, and the presence or absence of the slit hole from the reading unit. detecting a period of the signal indicating, based on the period, and a control unit for determining whether the stepping motor is operating normally, the width of the slit hole Serial integer multiple of the sum of the spacing of the slit is characterized that it matches the number of steps for one rotation of the stepping motor.

  According to the present invention, it is possible to provide an imaging apparatus that can reliably detect abnormal operation of a stepping motor even when it is susceptible to disturbances or when the stepping motor is driven in a plurality of speed regions.

It is a block diagram which shows the structure of the imaging device which concerns on one Embodiment of this invention. It is a figure which shows the example of the pulse input for driving a stepping motor. It is a figure which shows the relationship between the excitation pattern with respect to the A phase in the case of 1-2 phase drive, / A phase, B phase, and / B phase, and the rotation direction of a stepping motor. It is a figure which shows the structural example of an external position detection system. It is a figure which shows the detailed structure of an encoder. It is a figure which shows the example of formation of the slit hole which a light shielding feather has. It is a flowchart shown about the flow of the main process at the time of the drive in the imaging device which concerns on one Embodiment of this invention. 5 is a flowchart showing details of a step-out detection 2 process. It is the flowchart which showed the detail of the process of a lens drive. It is a flowchart shown about the process of PI signal validity / invalidity determination. It is a figure which shows the example in case PI signal becomes invalid. It is a figure which shows the example in case PI signal becomes effective. It is a figure which shows the relationship between the state of a stepping motor, a step-out detection effective period, and a step-out detection effective period. It is a figure for demonstrating the step-out judgment corresponding to the step-out detection effective period.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a photographing apparatus according to an embodiment of the present invention. Here, the photographing apparatus shown in FIG. 1 shows an example of a digital camera with interchangeable lenses. That is, the photographing apparatus includes the interchangeable lens 100 and the camera body 200. The interchangeable lens 100 is configured to be detachable from the camera body 200 via a mount 201 provided on the camera body 200. When the interchangeable lens 100 is attached to the camera body 200, the lens CPU 107 in the interchangeable lens 100 and the body CPU 208 in the camera body 200 are connected to be able to communicate with each other. Thereby, the lens CPU 107 operates according to the control of the body CPU 208.

Hereinafter, each of the interchangeable lens 100 and the camera body 200 will be described.
First, the interchangeable lens 100 will be described. As shown in FIG. 1, the interchangeable lens 100 includes a focus lens 101, a stepping motor 102, an encoder 103, a signal detection circuit 104, an external position detection system 105, a motor driver 106, and a lens CPU 107. ing.

  The focus lens 101 is a lens for focus adjustment included in a photographing optical system for condensing a light beam from a subject (not shown). The focus lens 101 is driven along the optical axis direction indicated by an arrow in the drawing, and adjusts the focal position of the photographing optical system.

  The stepping motor 102 is a motor that is rotationally driven by a predetermined step angle in accordance with a pulse current input from the motor driver 106 for each step, and is attached to a movable portion for driving the focus lens 101. By driving the stepping motor 102, the focus lens 101 can be driven along the optical axis direction.

  FIG. 2A and FIG. 2B are diagrams illustrating an example of pulse input for driving the stepping motor 102. Here, the examples of FIGS. 2A and 2B show a case where the winding configuration of the stepping motor 102 is two-phase (A-phase winding, B-phase winding).

  2A shows the pulse input in the case of 2-2 phase driving, and FIG. 2B shows the pulse input in the case of 1-2 phase driving. In general, in the 1-2 phase driving shown in FIG. 2B, the rotation amount of the stepping motor can be controlled more finely than in the 2-2 phase driving shown in FIG. In FIG. 2B, pulse input in the case of microstep driving is also shown by a one-dot chain line. By performing microstep driving, it is possible to control the amount of rotation of the stepping motor in finer steps. In this embodiment, the same method as the conventional method can be used as the driving method of the stepping motor 102. Here, detailed description of each driving method is omitted.

  FIG. 3 shows the relationship between the excitation pattern for the A phase, / A (Aber) phase, B phase, and / B (Beaver) phase and the rotation direction of the stepping motor 102 in the case of 1-2 phase driving. Each time the excitation patterns of the A phase, / A phase, B phase, and / B phase are switched in accordance with the order shown in FIG. 3, the stepping motor 102 is driven to rotate by a predetermined step angle.

  The encoder 103 has a photo interrupter (PI) and a rotating plate. It is possible to detect the drive amount (drive position) of the focus lens 101 from the PI signal output from the PI of the encoder 103. Details of the encoder 103 will be described later.

  The signal detection circuit 104 binarizes the PI signal output from the PI of the encoder 103 and outputs it to the lens CPU 107. With this configuration, the lens CPU 107 can digitally process the PI signal. If the lens CPU 107 is provided with an A / D conversion terminal, the PI signal can be directly captured by the lens CPU 107. In this case, the signal detection circuit 104 is not necessary.

  The external position detection system 105 is a detection system that detects the position of the focus lens 101 independently of the encoder 103, and is configured to be able to detect a position interval larger than the position interval detected by the encoder 103. A position detection signal from the external position detection system 105 is also input to the lens CPU 107. FIG. 4 is a diagram illustrating a configuration example of the external position detection system 105. First, FIG. 4A shows an example in which the external position detection system 105 is configured with a mechanical section encoder. In the example of FIG. 4A, a predetermined encoder pattern is formed in the drive mechanism unit of the focus lens 101, and depending on the contact state between the encoder pattern accompanying the movement of the focus lens 101 and a plurality of input terminals of the lens CPU 107. The position of the focus lens 101 is detected by detecting the changing signals FCENC1 to FCENC4. FIG. 4B shows an example in which the external position detection system 105 is configured with a linear encoder. In the example of FIG. 4B, a contact that slides as the focus lens 101 moves is connected to the variable resistor R1, and the variable resistor R1 that changes as the focus lens 101 moves is divided. The position of the focus lens 101 is detected by detecting the detected voltage with an A / D converter or the like provided in the lens CPU 107. In addition, various position detection systems can be used.

  The motor driver 106 receives a drive instruction signal from the lens CPU 107 and applies a pulse current for rotating the stepping motor 102 as shown in FIG. 2 in units of steps. The motor driver 106 outputs an EXT signal to the lens CPU 107 when applying a pulse current for rotating the stepping motor 102. This EXT signal is a signal for causing the lens CPU 107 to recognize the timing from the start of the operation of the stepping motor 102 to the end of the operation.

  Furthermore, the motor driver 106 in this embodiment outputs an OKA signal to the lens CPU 107 at one step intervals. 2 and 3 show the output timing of the OKA signal. Based on the OKA signal, the lens CPU 107 recognizes a break of one step. Note that the interval between the OKA signals varies depending on the driving speed of the stepping motor 102. That is, when the stepping motor 102 is driven at a high speed, it is necessary to switch the excitation pattern of each winding at a high speed, so the interval of one step is shortened. Therefore, the interval of the OKA signal is shortened. Conversely, when the stepping motor 102 is driven at a low speed, the interval between the OKA signals becomes long.

  Note that a time corresponding to one step can be determined prior to driving the focus lens 101. Therefore, if the time corresponding to one predetermined step is counted in the lens CPU 107, it is not always necessary to output the OKA signal from the motor driver 106.

  In response to the lens drive instruction from the body CPU 208, the lens CPU 107 outputs a drive instruction signal for instructing the drive direction, drive amount, and drive speed of the stepping motor 102 to the motor driver 106. The lens CPU 107 in this embodiment also has a function as a control unit. That is, the lens CPU 107 in the present embodiment detects the drive amount of the focus lens 101 according to the PI signal from the encoder 103 and controls the drive instruction signal to be given to the motor driver 106. Furthermore, the lens CPU 107 in this embodiment also determines whether or not the stepping motor 102 is operating normally according to the PI signal from the encoder 103 and the position detection signal from the external position detection system 105.

  Next, the camera body 200 will be described. As shown in FIG. 1, the camera body 200 includes an image sensor 202, a shutter 203, a camera shake correction unit 204, a display unit 205, a finder 206, a power source 207, and a body CPU 208.

  The image pickup element 202 has a light receiving surface on which photoelectric conversion elements such as photodiodes are arranged, and from an object (not shown) formed on the light receiving surface through a photographing optical system including the focus lens 101 in the interchangeable lens 100. Light is converted into an electrical signal (hereinafter referred to as an image signal), and the image signal is further converted into a digital signal (hereinafter referred to as image data) and output to the body CPU 208.

  The shutter 203 is disposed with respect to the light receiving surface of the image sensor 202, and puts the light receiving surface of the image sensor 202 in an exposed state or a light shielding state in accordance with an instruction from the body CPU 208. By controlling the exposure time of the light receiving surface of the image sensor 202, the exposure amount in the image sensor 202 can be controlled.

  The camera shake correction unit 204 corrects image shake that occurs in the image sensor 202 due to shaking of the camera body 200, for example, by moving the image sensor 202 in a plane perpendicular to the optical axis of the focus lens 101.

  The display unit 205 is provided on the back surface of the camera body 200, for example, and displays various images based on image data and the like obtained via the image sensor 202 under the control of the body CPU 208. The viewfinder 206 is for confirming the state of the subject through a window formed on the back surface of the camera body 200, for example. The viewfinder 206 is an electronic viewfinder, for example, and displays an image based on image data obtained via the image sensor 202 in real time under the control of the body CPU 208.

  The power source 207 is a secondary battery, for example, and supplies power to the body CPU 208 of the camera body 200 and the like. In addition, when the interchangeable lens 100 is attached to the camera body 200, the power source 207 supplies power to the lens CPU 107 of the interchangeable lens 100 and the like.

  The body CPU 208 controls the operation of each part of the camera body 200 such as the image sensor 202, the shutter 203, the camera shake correction unit 204, the display unit 205, and the viewfinder 206. The body CPU 208 also performs various data processing such as image processing on image data obtained via the image sensor 202. Furthermore, when it is necessary to drive the focus lens 101 during autofocus (AF), the body CPU 208 outputs a drive instruction signal including the drive direction, drive amount, and drive speed of the focus lens 101 to the lens CPU 107.

  Next, the configuration of the encoder 103 will be further described. FIG. 5 is a diagram showing a detailed configuration of the encoder 103. In FIG. 5, the encoder 103 includes a photo interrupter (PI) 1031 and a light shielding feather 1032.

  The PI 1031 having a function as a reading unit is formed so that the light emitting element 1031a and the light detecting element 1031b face each other. The PI 1031 is configured to output a PI signal to the signal detection circuit 104 when the light emitted from the light emitting element 1031a is received by the light detection element 1031b. For example, a light-emitting diode can be used as the light-emitting element 1031a, and a phototransistor can be used as the light-detecting element 1031b.

  The light shielding wing 1032 having a function as a rotating body is mounted on the rotating shaft of the stepping motor 102 so as to be disposed between the light emitting element 1031a and the light detecting element 1031b formed in the PI 1031. Furthermore, a plurality of slit holes 1032a as shown in FIG. 6A and FIG. 6B are formed in the light shielding blade 1032, and a portion other than the slit holes 1032a is a light shielding portion 1032b.

  In the present embodiment, a plurality of types of slit holes 1032a having different widths are formed. The width of each slit hole 1032a is an integral multiple of the width corresponding to the driving amount of one step of the stepping motor 102. Further, as shown in FIGS. 6A and 6B, slit holes 1032a having different widths adjacent to each other with the light shielding portion 1032b interposed therebetween are formed.

  Note that the difference in width between the different types of slit holes 1032a is preferably two or more steps. This is to reduce the possibility of erroneous detection of the PI signal.

  Further, in the present embodiment, the width of the light shielding portion 1032b (that is, the slit hole) so that the integral multiple of the total width of the slit hole 1032a and the width of the light shielding portion 1032b is the number of steps for one rotation of the stepping motor 102. 1032a). Similarly to the slit hole 1032a, the width of the light shielding portion 1032b is set to an integral multiple of the width corresponding to the driving amount of one step. Further, all the light shielding portions 1032b have the same width. Further, with respect to the widths of the slit hole 1032a and the light shielding portion 1032b determined as described above, the position interval of the external position detection system 105 corresponds to an integral multiple of the sum of the width of the slit hole 1032a and the width of the light shielding portion 1032b. The interval should be larger than that.

  6A and 6B illustrate an example in which the number of steps for one rotation of the stepping motor 102 is 40 steps.

  FIG. 6A shows light shielding by two types of slit holes 1032a having a width corresponding to a driving amount of 3 steps and a width corresponding to a driving amount of 9 steps, and a light shielding portion 1032b having a width corresponding to a driving amount of 4 steps. An example in which wings 1032 are formed is shown. When the slit hole 1032a is formed in this way, the sum of the width of the slit hole 1032a and the width of the light shielding portion 1032b is 4 + 3 + 4 + 9 = 20 (step). If the 20 steps are doubled, the number of steps of one rotation of the stepping motor 102 becomes 40 steps.

  FIG. 6B shows three types of slit holes 1032a having a width corresponding to a driving amount of 2 steps, a width corresponding to a driving amount of 5 steps, and a width corresponding to a driving amount of 7 steps, and a driving amount of 2 steps. The example which formed the light-shielding blade 1032 in the light-shielding part 1032b of the width | variety corresponding to is shown. When the slit hole 1032a is formed in this way, the sum of the width of the slit hole 1032a and the width of the light shielding portion 1032b is 2 + 2 + 2 + 5 + 2 + 7 = 20 (step). Also in this case, if the total of the width of the slit hole 1032a and the width of the light shielding portion 1032b is doubled, the number of steps corresponding to one rotation of the stepping motor 102 is 40 steps.

  Although not shown, for example, two types of slit holes 1032a having a width corresponding to a driving amount of 4 steps and a width corresponding to a driving amount of 8 steps, and light shielding of a width corresponding to a driving amount of 4 steps. The light shielding feather 1032 may be formed by the portion 1032b. Also in this case, the sum of the width of the slit hole 1032a and the width of the light shielding portion 1032b is 4 + 4 + 4 + 8 = 20 (step).

  In addition, each of the above examples shows an example in which the sum of the width of the slit hole 1032a and the width of the light shielding portion 1032b is doubled to obtain the number of steps for one rotation of the stepping motor 102. However, the slit hole 1032a is formed so that the sum of the width of the slit hole 1032a and the width of the light shielding part 1032b is 40 (step), that is, one times the sum of the width of the slit hole 1032a and the width of the light shielding part 1032b. Alternatively, the slit is formed so that the sum of the width of the slit hole 1032a and the width of the light shielding portion 1032b is 10 (step), that is, four times the sum of the width of the slit hole 1032a and the width of the light shielding portion 1032b. The hole 1032a may be formed.

  When the stepping motor 102 is rotationally driven to drive the movable portion 101a of the driving mechanism of the focus lens 101, the light shielding blade 1032 is also rotated along with this rotational driving. Depending on the rotation state of the light shielding wing 1032, light emitted from the light emitting element 1031 a of the PI 1031 is received by the light detecting element 1031 b through the slit hole 1032 a or shielded by the light shielding portion 1032 b. As described above, the PI signal is output while light is received by the light detection element 1031b. Therefore, by counting the time during which the PI signal is output, the rotation direction and the rotation amount of the light shielding blade 1032, That is, the driving direction and driving amount of the stepping motor 102 can be detected.

  In this embodiment, by forming a plurality of slit holes 1032a having different widths in the light shielding wing 1032, it is possible to reliably detect abnormality such as step-out. Details of the step-out detection will be described later.

  Hereinafter, the operation of the photographing apparatus having the above-described configuration will be described. FIG. 7 is a flowchart showing the flow of main processing at the time of lens driving performed at the time of AF (autofocus) or the like in the photographing apparatus according to the present embodiment.

  In FIG. 7, the lens CPU 107 determines whether or not a lens driving instruction has been issued from the body CPU 208 (step S101). If it is determined in step S101 that no lens driving instruction has been issued, the lens CPU 107 performs a step-out detection 2 process (step S102). Details of the process of step-out detection 2 will be described later.

  After the step-out detection 2 is executed, the lens CPU 107 determines whether or not step-out is detected as a result of the step-out detection 2 (step S103). In step S103, if no step-out is detected, the process returns to step S101. In this case, the lens CPU 107 determines again whether or not a lens driving instruction has been issued from the body CPU 208. Further, when the step-out is detected in the determination of step S103, the lens CPU 107 ends the process of FIG. In this case, the body CPU 208 may be notified that a step-out has occurred. In this way, for example, it can be displayed on the display unit 205 of the camera body 200 that an abnormality has occurred during lens driving.

  In the determination in step S101, when a lens driving instruction is issued, the lens CPU 107 performs lens driving (step S104). Details of the lens driving process will be described later. After the lens drive is executed, the lens CPU 107 executes the processing after step S103.

  FIG. 8 is a flowchart showing details of the process of step-out detection 2. It is assumed that a PI signal is interrupted and inputted from the encoder 103 to the lens CPU 107 via the signal detection circuit 104 during the process of step-out detection 2.

  In FIG. 8, the lens CPU 107 determines whether or not a PI signal is input (step S201).

  When the PI signal is input in the determination in step S201, the lens CPU 107 performs a step-out determination corresponding to the step-out detection 2 (step S202). As shown in FIG. 7, the step-out detection 2 is performed when no lens driving instruction is issued from the body CPU 208. Therefore, when the step-out detection 2 is performed, normally, the focus lens 101 should be stopped and no PI signal should be input. Therefore, when the PI signal is input in the determination in step S201, the lens CPU 107 determines that a step-out has occurred.

  If the PI signal is not input in the determination in step S201, the lens CPU 107 ends the process in FIG. In this case, the process after step S103 of FIG. 7 is performed.

  FIG. 9 is a flowchart showing details of the lens driving process. During the lens driving process, the lens CPU 107 receives the PI signal from the encoder 103, the external position detection signal from the external position detection system 105, and the OKA signal from the motor driver 106.

  In FIG. 9, the lens CPU 107 performs initial settings necessary for driving the focus lens 101 (step S301). In this initial setting, the driving direction, driving amount, and driving speed of the stepping motor 102 corresponding to the driving direction, driving amount, and driving speed of the focus lens 101 that are instructed together with the lens driving instruction are calculated and the focus lens 101 is driven. The PI signal time in is calculated.

  Here, the PI signal time will be described. The PI signal time is a time interval at which the PI signal should be output. This PI signal time is used in the processing of step-out detection 1 described later in detail. The PI signal time is calculated according to the following equation.

PI signal time = (width of slit hole formed in shading blade 1032) × (OKA signal interval)
For example, when the interval of the OKA signal is X, the PI signal time in the case of the stepping motor 102 to which the shading blade 1032 shown in FIG. 3A is attached is a portion where the width of the slit hole corresponds to 3 steps. 3X, where the slit hole width corresponds to 9 steps is 9X. In this case, if the stepping motor 102 is normally driven at a constant speed, a period in which the PI signal is at the H (high) level appears in the order of 3X, 9X, 3X, 9X,. It is assumed that the slit hole portion corresponds to the H (high) level of the PI signal.

  After the initial setting, the lens CPU 107 starts counting an internal PI signal detection timer (not shown) (step S302). Thereafter, the lens CPU 107 outputs a drive instruction signal to the motor driver 106 to start driving the focus lens 101 (step S303). Further, the lens CPU 107 starts detecting the PI signal from the signal detection circuit 104 (step S304).

  Next, the lens CPU 107 determines whether the PI signal from the signal detection circuit 104 is valid or invalid (step S305).

  Here, PI signal valid / invalid determination processing will be described with reference to FIGS. FIG. 10 is a flowchart showing the PI signal valid / invalid determination process.

  In FIG. 10, the lens CPU 107 determines whether or not an OKA signal is input from the motor driver 106 (step S401). If the OKA signal is input in the determination in step S401, the PI signal count is cleared to 0 (step S402).

  After step S401 or S402, the lens CPU 107 determines whether a PI signal is input from the signal detection circuit 104 (step S403). In the present embodiment, the rise and fall of the PI signal are counted as one count in the section delimited by the OKA signal (OKA signal section), and the PI signal is input when the PI signal rises or falls. It is determined that If the PI signal is input in the determination in step S403, 1 is added to the count of the PI signal (step S404).

  After step S403 or S404, the lens CPU 107 determines whether the input PI signal is valid or invalid based on the PI signal count result within the OKA signal interval (step S405). In the present embodiment, when the total rise and fall of the PI signal within the OKA signal section is an even number, it is determined that the PI signal is invalid. Conversely, if the total rise and fall of the PI signal within the OKA signal interval is an odd number, it is determined that the PI signal is valid.

  FIG. 11A and FIG. 11B show examples in which the PI signal is invalid. FIG. 11A shows an example in which one rising edge and one falling edge are detected during the OKA signal interval (when the sum of the rising edge and falling edge of the PI signal is 2). FIG. 11B shows an example in which two rising edges and two falling edges are detected during the OKA signal interval (when the total rise and fall of the PI signal is 4). Both rising and falling of the PI signal are detected during the OKA signal period, corresponding to the operation of the stepping motor 102 for one step, the light shielding portion 1032b of the light shielding blade 1032, the slit hole 1032a, and the light shielding portion 1032b. Is detected, or the slit hole 1032a, the light shielding part 1032b, and the slit hole 1032a of the light shielding blade 1032 are respectively detected. In such a case, it is considered that at the end of the OKA signal interval, the stepping motor 102 is rotating in the reverse direction with respect to the rotation direction to be driven, that is, the stepping motor 102 is oscillating. Therefore, it is assumed that the PI signal in such a case is invalid.

  FIGS. 12A and 12B show an example in which the PI signal is valid. FIG. 12A shows an example in which two rising edges and one falling edge are detected during the OKA signal interval (when the sum of the rising edge and falling edge of the PI signal is 3). FIG. 12B shows an example in which three rising edges and two falling edges are detected during the OKA signal interval (when the total rise and fall of the PI signal is 5). In such a case, the stepping motor 102 is correctly driven to rotate in the direction to be finally rotated at the end of the OKA signal interval. Therefore, it is assumed that the PI signal in such a case is valid.

  Here, returning to FIG. 9, the description will be continued. After the PI signal valid / invalid determination in step S305, the period during which the PI signal determined to be valid is H is calculated from the count of the PI signal detection timer (step S306). Next, the lens CPU 107 determines whether or not it is currently in the step-out detection period (step S307). The step-out detection period in the present embodiment is either a period during which the stepping motor 102 is operating at a constant speed (step-out detection effective period 1) or a period during which the stepping motor 102 is stopped (step-out detection effective period 2). I will do it. Actually, the determination in step S307 is performed while the lens is being driven. Therefore, in step S307, it is determined whether or not the out-of-step detection valid period is one. Further, the step-out determination in the step-out detection valid period 2 corresponds to the processing of step-out detection 2 described above. FIG. 13 shows the relationship between the state of the stepping motor 102 and the step-out detection valid periods 1 and 2. As shown in FIG. 13, step-out detection is not performed for initial excitation (excitation before driving the stepping motor 102) and holding excitation (excitation after driving the stepping motor 102). Further, step-out detection is not performed during acceleration of the stepping motor 102 after initial excitation or during deceleration of the stepping motor 102 before holding excitation. Further, step-out detection is not performed for a predetermined time A (value determined by the mechanical structure of the stepping motor 102) ms after holding excitation. The initial excitation period, the holding excitation period, the acceleration of the stepping motor 102, the deceleration of the stepping motor 102, and the period of the predetermined time A after the holding excitation are all periods in which the operation of the stepping motor 102 is not stable. . Then, the step-out determination is made in the other periods.

  If it is determined in step S307 that the current step-out detection valid period is 1, the lens CPU 107 performs a step-out determination corresponding to the step-out detection valid period 1 (step S308).

Here, the step-out determination corresponding to the step-out detection effective period 1 will be described. In this embodiment, during the step-out detection valid period 1, it is determined whether or not an abnormality such as step-out has occurred from the following three conditions.
(1) Is PI signal of the same output pattern continuous?
(2) Whether the time during which the PI signal is at the H level coincides with the PI signal period
(3) State of External Position Detection Signal from External Position Detection System 105 First, (1) will be described. As shown in FIGS. 6A and 6B, the light shielding wing 1032 in this embodiment has slit holes 1032a formed so that slit holes 1032a having different widths are adjacent to each other with the light shielding portion 1032b interposed therebetween. ing. Therefore, for example, if the stepping motor 102 to which the light-shielding blade 1032 having the slit hole 1032a as shown in FIG. The relationship of high (H) / low (L) is as shown in FIG. That is, if the stepping motor 102 is normally driven, PI signals corresponding to the slit holes 1032a having different widths should be alternately input. Based on such a concept, for example, in a state where a PI signal corresponding to the slit hole 1032a having the same width is input twice in succession, the stepping motor 102 itself has stopped due to some disturbance, or the stepping motor It is determined that step-out has occurred because 102 is performing a vibration operation.

  Next, (2) will be described. As described above, the period during which the PI signal is H is determined by the width of the slit hole 1032a and the interval of the OKA signal. Accordingly, when the period during which the PI signal is H does not coincide with the PI signal period calculated at the time of initial setting of lens driving, it is determined that the step-out has occurred. Actually, it is desirable to set a time width of an allowable error Y (%) as shown in FIG. 14B in the PI signal period calculated at the time of initial lens drive setting.

  Next, (3) will be described. Even if the PI signal is output normally, it cannot be said that the step-out has not necessarily occurred. For this reason, although the PI signal is input and the driving amount of the stepping motor 102 is calculated from the input of the PI signal to the extent that the external position detection signal is also input from the external position detection system 105, Even when no external position detection signal is input from the external position detection system 105, it is determined that the step-out has occurred. For example, at the signal interval (inside the arrow) of the external position detection system 105 shown in FIG. 14C, the planned number of PI signal inputs is compared with the actually detected number of PI signal inputs. When the predetermined amount is exceeded, it is determined to be out of step.

  By using the step-out determination as described above, the step-out determination can be correctly performed even when the stepping motor is driven at a constant speed in various speed ranges from the lowest speed to the highest speed. On the low speed side, when the stepping motor 102 is oscillating, the state can also be detected as a step-out.

  After step out determination corresponding to step out detection valid period 1 in step S308, the lens CPU 107 determines whether step out has been detected (step S309). In step S309, when step out is not detected, the process returns to step S303. Then, the lens CPU 107 repeats the processes in steps S303 to S309 until the drive amount of the focus lens 101 reaches the drive amount instructed from the body CPU 208. On the other hand, when the step-out is detected in the determination in step S309, the lens CPU 107 ends the process of FIG. In this case, the body CPU 208 may be notified that a step-out has occurred. In this way, for example, it can be displayed on the display unit 205 of the camera body 200 that an abnormality has occurred during lens driving.

  As described above, according to the present embodiment, a plurality of types of slit holes 1032a having different widths are formed in the light shielding wing 1032 so that a predetermined relationship is established during the period in which the PI signal input to the lens CPU 107 is H. I try to have it. Thereby, it is possible to correctly determine the step-out in the stepping motor 102 suitable for driving the movable part of the photographing apparatus.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention. In the above-described example, the movable part of the focus lens 101 is illustrated as an example of the movable part of the photographing apparatus driven by the stepping motor 102. However, the technique of the present embodiment can be applied to other various movable parts. For example, the technique of the present embodiment may be applied to a stepping motor for driving a diaphragm. If the photographing optical system has a zoom lens, the stepping motor for driving the zoom lens is used. However, the technique of the present embodiment may be applied.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

  DESCRIPTION OF SYMBOLS 100 ... Interchangeable lens, 101 ... Focus lens, 102 ... Stepping motor, 103 ... Encoder, 104 ... Signal detection circuit, 105 ... External position detection system, 106 ... Motor driver, 107 ... Lens CPU, 200 ... Camera body, 201 ... Mount DESCRIPTION OF SYMBOLS 202 ... Imaging device 203 ... Shutter 204 ... Correction | amendment part 205 ... Display part 206 ... Finder ... 207 ... Power supply 208 ... Body CPU, 1031 ... Photo interrupter (PI), 1032 ... Light-shielding feather

Claims (4)

A stepping motor that is rotationally driven in accordance with a pulse signal input in units of one step, and that drives the movable portion of the imaging apparatus by the rotational drive;
The stepping motor has a width corresponding to the driving amount of one step as one unit, and is a slit hole having a width that is an integral multiple of the one unit, and two or more types of slit holes having different widths are formed. A rotating body that rotates with the rotation of the motor;
A reading unit that reads the presence or absence of the slit hole and outputs a signal indicating the presence or absence of the slit hole;
A control unit that detects a period of a signal indicating the presence or absence of the slit hole from the reading unit and determines whether or not the stepping motor is operating normally based on the period;
Equipped with,
The imaging apparatus according to claim 1, wherein an integral multiple of the total width of the slit holes and the interval between the slit holes is equal to the number of steps of one rotation of the stepping motor . The difference between the width of at least one slit hole and the width of another slit hole among the two or more kinds of slit holes having different widths of the rotating body is larger than two steps. The imaging device described. The control unit determines whether the stepping motor is operating normally by comparing a period of a signal indicating the slit hole output from the reading unit with a time calculated based on the width of the slit hole. The imaging device according to claim 1. 4. The photographing apparatus according to claim 3, wherein the control unit determines whether or not the stepping motor is operating normally when the stepping motor is moved at a constant speed.

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