Lens device, control method, and program

Abstract

To provide a lens device, a control method, and a program capable of reducing exposure flickering of a captured moving image even when a light amount change due to aperture driving is non-linear.SOLUTION: A lens device detachably attached to an imaging device includes: an aperture mechanism that adjusts an amount of light; a stepping motor that drives the aperture mechanism; and a communication unit that transmits, to the imaging device, exposure information based on information about the actual position of the aperture mechanism.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a lens apparatus, a control method, and a program. [Background technology]

[0002] In recent years, camera systems have been required to improve the accuracy of their automatic exposure control (hereinafter referred to as AE control), particularly to reduce exposure flicker in recorded videos.To reduce exposure flicker in recorded videos, it is important to always match the amount of exposure control by ISO sensitivity and shutter speed control in AE control with the amount of exposure control by the aperture in the interchangeable lens.

[0003] Patent Document 1 discloses a technique for reducing exposure flicker by performing AE control taking into consideration delays in communication between a camera and a lens and mechanical delays in driving the aperture. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5132497 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 is based on the premise that the change in light quantity due to aperture drive is linear, but in reality the change in light quantity due to aperture drive is not linear due to changes in the degree of overlap of the aperture blades, uneven magnetization of the rotor, etc. In other words, with the technology of Patent Document 1, the amount of exposure control by ISO sensitivity and shutter speed control in AE control does not match the amount of exposure control by the aperture in the interchangeable lens.

[0006] The present invention aims to provide a lens device, a control method, and a program that can reduce exposure flicker in captured moving images even when the change in light amount due to aperture driving is nonlinear. [Means for solving the problem]

[0007] A lens device according to one aspect of the present invention is a lens device that is detachably attached to an imaging device, and includes an aperture mechanism that adjusts the amount of light, and a stepping motor that drives the aperture mechanism. , aperture and a communication unit that transmits exposure information based on information about the actual position of the exposure mechanism to the imaging device at predetermined intervals. The predetermined period is changed according to the driving speed of the aperture mechanism. It is characterized by the following. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a lens device, a control method, and a program that can reduce exposure flicker in captured moving images even when the change in light amount due to aperture driving is nonlinear. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram of an imaging device according to a first embodiment. [Figure 2] FIG. 4 is an explanatory diagram relating to control of the aperture unit. [Figure 3] FIG. 10 is an explanatory diagram of the cause of exposure flicker. [Figure 4] FIG. 10 is a diagram illustrating exposure flicker. [Figure 5] 5 is a diagram showing changes in the output value and F value of the motor rotational position detector of the first embodiment. FIG. [Figure 6] 10 is a flowchart showing aperture drive processing in the first embodiment. [Figure 7] 10 is a flowchart showing a process for acquiring current F-number information according to the first embodiment. [Figure 8] FIG. 10 is a diagram showing the aperture unit in a narrowed state. [Figure 9] 10 is a flowchart showing a process for acquiring the amount of deviation between ideal F-number information and actual F-number information according to the second embodiment. [Figure 10] This is a correction table for the amount of deviation between ideal F-number information and actual F-number information. [Figure 11]11 is a flowchart showing a control process of the pulse rate of a drive signal according to the third embodiment. [Figure 12] 12 is a diagram showing a change in the output of a drive signal when the flow of FIG. 11 is executed. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted. [Example]

[0011] <Configuration of imaging device> FIG. 1 is a configuration diagram of an imaging system according to this embodiment. The imaging system includes a photographic lens (lens apparatus) 100 and a camera (imaging apparatus) 200. The photographic lens 100 is detachably attached to the camera 200. The photographic lens 100 and the camera 200 are mechanically and electrically connected by a mount 300, which is a coupling mechanism. The photographic lens 100 obtains power from the camera 200 via a terminal section of the mount 300, and consumes the power as a driving power source for various actuators and a processing power source for a microprocessor 116 in the photographic lens 100. A microprocessor 207 in the camera 200 and the microprocessor 116 in the photographic lens 100 are connected by a communication line, and information is exchanged between them.

[0012] The photographing lens 100 includes an imaging optical system. The imaging optical system includes, arranged in this order from the object side to the image side, a field lens 101, a zoom lens 102 as a variable magnification lens, an aperture unit (aperture mechanism) 114 that adjusts the amount of light, an afocal lens 103, and a focus lens 104 as a focusing lens. A lens configuration in which the focus lens 104 is arranged on the image side is called a rear-focus lens, and is commonly used in small interchangeable lens cameras, compact digital cameras, etc.

[0013] The zoom lens 102 and the focus lens 104 are held by lens holding frames 105 and 106, respectively. The lens holding frames 105 and 106 are configured to be movable in the optical axis direction (in the direction of the arrow in the figure) when stepping motors 107 and 108 are driven. The stepping motors 107 and 108 move the zoom lens 102 and the focus lens 104, respectively, in synchronization with drive signals.

[0014] The microprocessor 116 performs control in response to lens control commands given from the camera 200, and is responsible for controlling the overall operation of the photographic lens 100. The microprocessor 116 also communicates lens information (information related to the F-number, information related to the T-number, focus lens position information, etc.) to the camera communication unit 208 via the lens communication unit 110. The microprocessor 116 also converts the position of the zoom lens 102 detected by a zoom position detection unit composed of a sensor such as a variable resistor into digital data.

[0015] The drive circuits 111 and 113 respectively drive the stepping motors 107 and 108 in response to drive signals input from the microprocessor 116. That is, the zooming operation of the imaging optical system and the accompanying focusing operation are performed by controlling the stepping motors 107 and 108 using an electronic cam system that utilizes cam trajectory data that is commonly used in digital cameras, etc. The motors that move the zoom lens 102 and the focus lens 104 may be DC motors or ultrasonic motors that use piezoelectric elements as vibrators.

[0016] The aperture unit 114 includes aperture blades 114a and 114b. The aperture full-open position detection sensor 115 includes a sensor such as a photointerrupter, detects whether the aperture blades 114a and 114b are in the full-open position (the position where the aperture diameter is maximum), and outputs the detection information to the microprocessor 116. The microprocessor 116 outputs a control signal (drive signal) to the aperture drive circuit 112 in accordance with the detection information obtained from the aperture full-open position detection sensor 115. The aperture drive circuit 112 drives the stepping motor 109 based on the control signal obtained from the microprocessor 116. In this embodiment, the microprocessor 116 functions as a drive unit that controls the drive of the stepping motor 109.

[0017] A rotational position detection unit (detection unit) 117 is attached to the stepping motor 109 and detects the rotational position of the rotor of the stepping motor 109. In this embodiment, the motor rotational position detection unit 117 is a Hall sensor, but it may be another sensor such as a photointerrupter. The rotational position of the rotor may be detected directly or by detecting a change in a magnetic field caused by the rotation of the rotor. Information related to the detected rotational position of the rotor is stored in the microprocessor 116 and used to control the stepping motor 109.

[0018] The control of the aperture unit 114 performed by the microprocessor 116 will be described below with reference to Fig. 2. Fig. 2 is an explanatory diagram relating to the control of the aperture unit 114.

[0019] The microprocessor 116 includes a drive speed setting unit 118, a drive waveform generating unit 119, a drive amount counting unit 120, an F-number determining unit 121, a ROM 122, and a RAM 123. However, each unit may be configured separately using separate hardware modules, or one or several units may be configured separately.

[0020] The drive speed setting unit 118 determines the pulse rate of the drive signal to be excited to the stepping motor 109 based on the aperture drive speed command issued by the camera 200. The drive waveform generation unit 119 generates an excitation pattern of the drive signal in accordance with the pulse rate determined by the drive speed setting unit 118 and a drive method such as two-phase drive, one-two phase drive, or microstep drive, and outputs the generated drive signal to the aperture drive circuit 112. The aperture drive circuit 112 converts the generated drive signal into the required current and voltage and supplies it to the stepping motor 109.

[0021] The drive amount counting unit 120 increments or decrements the counter each time the excitation pattern generated by the drive waveform generating unit 119 changes, thereby acquiring the drive amount of the aperture unit 114. This makes it possible to acquire information regarding the rotational position of the rotor of the stepping motor 109.

[0022] The F-number determination unit 121 acquires information about the current F-number (F-number information) based on the drive amount acquired by the drive amount counting unit 120 and the output value of the aperture full-open position detection sensor 115 or the output value of the motor rotation position detection unit 117. For example, the current F-number information corresponding to the drive amount acquired by the drive amount counting unit 120 may be acquired based on the timing when the aperture full-open position detection sensor 115 detects that the aperture blades 114a, 114b are at the full-open position. Alternatively, the current F-number information corresponding to the amount of change in the output value of the motor rotation position detection unit 117 may be acquired based on the full-open F-number.

[0023] The ROM 122 stores the above-mentioned operation programs and other control programs, fixed data, etc. The RAM 123 temporarily stores the results of calculations used in the above-mentioned operation programs and other control programs, and data to be held.

[0024] The camera 200 includes an image sensor 201 , an A / D conversion circuit 202 , a signal processing circuit 203 , a recording unit 204 , an AE control unit 205 , a display unit 206 , a microprocessor 207 , a camera communication unit 208 , and a mode switching unit 209 .

[0025] An optical image passing through the photographing lens 100 is converted into an electrical signal (analog signal) by photoelectric conversion using an image sensor 201 such as a CCD sensor or a CMOS sensor. The analog signal is converted into a digital signal by an A / D conversion circuit 202 and input to a signal processing circuit 203. The signal processing circuit 203 performs various image processing on the input electrical signal (digital signal) to generate focus information indicating the focus state of the image, generate luminance signal information indicating the exposure state, and convert the signal into a recordable data format. An output signal (video signal) from the signal processing circuit 203 is sent to a recording unit 204 and recorded by the recording unit 204. The subject image generated by the signal processing circuit 203 is displayed on a display unit 206, allowing the composition of the subject image being photographed, the focus state, etc. to be confirmed in real time.

[0026] The microprocessor 207 controls the camera 200 in response to inputs from a shooting instruction switch and camera setting related switches (not shown). The microprocessor 207 also controls the microprocessor 116 to issue operation requests and settings to the photographing lens 100, such as requests to drive the zoom lens 102, the aperture unit 114, and the focus lens 104.

[0027] The AE control unit 205 includes a photometric sensor (not shown) that measures the amount of light incident on the image sensor 201, and uses the measured value (photometric value) to control the ISO sensitivity, shutter speed, and F-number so that the exposure of the captured image is appropriate. The mode switching unit 209 switches between set shooting modes such as aperture priority mode, shutter priority mode, still image mode, and video mode. For example, when aperture priority mode is selected, the AE control unit 205 requests aperture control from the microprocessor 116 via the camera communication unit 208 to achieve the F-number set by the user. The AE control unit 205 also achieves appropriate exposure control by adjusting the shutter speed and ISO sensitivity based on the change in light amount expected from changes in the aperture blades 114a and 114b.

[0028] The AE control unit 205 obtains a photometric value by performing photometric calculations based on the exposure information received from the photographing lens 100, and generates control values ​​(ISO, shutter speed, and F-number) from the obtained photometric value. Therefore, if there is a discrepancy between the exposure information received from the photographing lens 100 and the current exposure information of the aperture unit 114, an error will occur in the photometric value, an incorrect control value will be generated, and exposure accuracy will decrease. In particular, when shooting video, exposure flicker will occur, and the exposure flicker will be recorded in the shot video. Note that exposure information is information related to at least one of the F-number, AV value (Aperture Value), and T-number, and the following explanation will be given of an example in which AE control is performed based on F-number information.

[0029] Fig. 3 is an explanatory diagram of the cause of exposure flicker, and shows the state of exposure changes of the camera 200 and the photographing lens 100 after the camera 200 issues an aperture drive command to the photographing lens 100 at time 0 (the left end of the time axis) and AE control and aperture control start. Fig. 4 is a diagram showing exposure flicker.

[0030] The AE control unit 205 periodically receives F-number information from the photographic lens 100 and performs AE control based on that information. The exposure change caused by the aperture unit 114 is not linear due to changes in the overlapping state of the aperture blades 114a and 114b and uneven magnetization of the rotor, as shown by the lower solid line in FIG. 3. In this case, if the F-number information shown by the dotted line in FIG. 3 is notified to the camera 200, the camera 200 will perform an incorrect photometry calculation and perform AE control that results in the exposure change shown by the upper solid line in FIG. 3. As a result, exposure flicker occurs, as shown in FIG. 4.

[0031] The following describes changes in the output value of the motor rotational position detector 117 in this embodiment. The rotor of the stepping motor 109 is equipped with a detection magnet and a Hall sensor called the motor rotational position detector 117. As the rotor rotates, the magnetic flux density at the motor rotational position detector 117 changes, and the rotor's rotational position (≒ the positions of the diaphragm blades 114a and 114b) can be detected based on the change in magnetic flux density. FIG. 5(a) shows the output value of the motor rotational position detector 117 when the diaphragm unit 114 is driven by a drive signal output at a constant pulse rate. FIG. 5(b) shows the change in the F-number associated with changes in the output value of the motor rotational position detector 117. By storing the amount of change in the F-number relative to the amount of change in the output value of the motor rotational position detector 117 in the ROM 122 in advance, it is possible to determine the amount of change in the F-number from the amount of change in the output value of the motor rotational position detector 117. Even when a drive signal is output at a constant speed, the F-number change caused by the diaphragm unit 114 is not constant. Therefore, by notifying the camera 200 of the F-number information obtained based on the output value of the motor rotation position detection unit 117, the camera 200 can perform AE control based on the F-number information, thereby reducing exposure flicker.

[0032] 6, a process of acquiring current F-number information (actual exposure information) from the output value of the motor rotation position detection unit 117 and notifying it to the camera 200 will be described. Fig. 6 is a flowchart showing the aperture drive process of this embodiment.

[0033] In step S101, the microprocessor 116 determines whether or not there is a drive instruction from the camera 200 to the aperture unit 114. If it is determined that there is a drive instruction, the process proceeds to step S102, and if it is determined that there is not, the process of this step is repeated.

[0034] In step S102, the microprocessor 116 outputs a drive signal to drive the aperture to the specified drive amount or target F-number, and starts driving the aperture. The pulse rate of the drive signal is changed in accordance with an instruction from the camera 200.

[0035] In step S103, the microprocessor 116 acquires information on the shooting mode of the camera 200 through communication.

[0036] In step S104, the microprocessor 116 determines whether the shooting mode of the camera 200 acquired in step S103 is the video mode. If it is determined to be the video mode, the process proceeds to step S105; if it is determined not to be the video mode, the camera is driven to the specified drive amount or target F-number, and this flow ends.

[0037] In step S105, the microprocessor 116 determines whether a predetermined period has elapsed since the start of aperture drive. The predetermined period may be set in advance as a fixed value in the ROM 122. Furthermore, since the amount of change in the output value of the motor rotation position detection unit 117 per unit time increases as the pulse rate increases, the predetermined period may be changed according to the pulse rate so that changes in the output value of the motor rotation position detection unit 117 can be detected with high resolution. If it is determined that the predetermined period has elapsed, the process proceeds to step S106; if it is determined that the predetermined period has not elapsed, the process proceeds to step S107.

[0038] In step S106, the microprocessor 116 (F-number determination unit 121) acquires the current F-number information of the aperture unit 114.

[0039] FIG. 7 is a flowchart showing the process of acquiring the current F-number information.

[0040] In step S1061, the microprocessor 116 acquires the output value of the motor rotation position detection unit 117 (information on the actual position of the diaphragm unit 114).

[0041] In step S1062, the microprocessor 116 obtains the difference (amount of output change) between the output value obtained in step S1061 and the output value of the motor rotation position detection unit 117 stored in the previous process.

[0042] In step S1063, the microprocessor 116 acquires the amount of change in the F-number (information regarding changes in exposure information per predetermined cycle) from the amount of change in output acquired in step S1062. The amount of change in the F-number corresponding to the amount of change in output from the motor rotational position detection unit 117 is previously measured and stored in the ROM 122. Note that in this embodiment, the amount of change in the F-number is acquired from the amount of change in output from the motor rotational position detection unit 117, but the present invention is not limited to this. For example, the amount of change in the F-number may be acquired from the degree of overlap between the diaphragm blades 114a and 114b, the attitude of the diaphragm unit 114, the temperature or cumulative number of drives of the stepping motor 109, etc.

[0043] In step S1064, the microprocessor 116 acquires current F-number information by adding the amount of change in F-number acquired in step S1063 to the previous F-number information.

[0044] In step S1065, the microprocessor 116 stores the output value of the motor rotation position detection unit 117 in the RAM 123.

[0045] In step S1066, the microprocessor 116 stores in the RAM 123 the current F-number information acquired in step S1064.

[0046] In step S107, microprocessor 116 determines whether or not there is a request to transmit current F-number information from camera 200. If it is determined that there is a transmission request, the process proceeds to step S108, and if it is determined that there is not a transmission request, the process proceeds to step S109.

[0047] In step S108, microprocessor 116 notifies camera 200 of the current F-number information acquired in step S106. Note that instead of the current F-number information, the camera may be notified of the amount of deviation between ideal F-number information (ideal exposure information) corresponding to the drive signal of stepping motor 109 instructed by camera 200 and the current F-number information.

[0048] In step S109, the microprocessor 116 determines whether or not the camera 200 has been driven to the drive amount or target F-number instructed by the camera 200. If it is determined that the camera 200 has been driven to the instructed drive amount or target F-number, this flow ends, and if it is determined that the camera 200 has not been driven to the instructed drive amount or target F-number, the flow returns to step S105.

[0049] As described above, according to the configuration of this embodiment, the camera 200 periodically performs AE control based on the current F-number information received from the photographing lens 100. This makes it possible to obtain a photometric value from the F-number information of the aperture unit 114, improving exposure accuracy and reducing exposure flicker during video recording. [Example]

[0050] The configuration of the imaging system of this embodiment is the same as the configuration of the imaging system of embodiment 1. In this embodiment, configurations different from those of embodiment 1 will be described, and detailed descriptions of similar configurations will be omitted.

[0051] When a drive signal is output at a constant speed, the diaphragm blades 114a and 114b do not move at a constant speed due to uneven magnetization of the rotor or changes in the overlap of the diaphragm blades, i.e., changes in the load. Figure 8 shows the diaphragm unit 114 in a stopped-down state where the diaphragm blades 114a and 114b are stopped down. When the diaphragm blades 114a and 114b are stopped down, the overlapping area of ​​the diaphragm blades 114a and 114b increases, increasing friction. As a result, the load during operation becomes greater than when the diaphragm blades 114a and 114b are positioned on the open side, and the diaphragm blades 114a and 114b cannot move at a constant speed.

[0052] In this embodiment, a deviation amount between ideal exposure information and actual exposure information, which corresponds to a difference between an actual amount of change in output of the motor rotation position detection unit 117 per predetermined period and an ideal amount of change in output of the motor rotation position detection unit 117, is notified by advance measurement. Alternatively, actual exposure information obtained using the deviation amount may be notified. In this embodiment, an example of performing AE control based on F-number information will be described, as in the first embodiment.

[0053] FIG. 9 is a flowchart showing the process of acquiring the amount of deviation between the ideal F-number information and the actual F-number information corresponding to the actual position of the aperture unit 114 in this embodiment.

[0054] In step S201, the microprocessor 116 (drive waveform generating unit 119) outputs one unit of drive waveform. One unit may be one step of 1-2 phase drive, or a drive amount that can be expressed as a multiple of the drive resolution of microstep drive.

[0055] In step S202, the microprocessor 116 determines whether or not the driving of the aperture unit 114 has ended. If it is determined that the driving has ended, the process proceeds to step S203, and if it is determined that the driving has not ended, the process of this step is repeated.

[0056] In step S203, the microprocessor 116 acquires the output value of the motor rotation position detection unit 117.

[0057] In step S204, the microprocessor 116 acquires F-number information (amount of deviation between ideal exposure information and actual exposure information) corresponding to the difference between the ideal amount of output change per unit of the drive waveform and the output value acquired in step S203. Note that in this embodiment, the F-number information is acquired from the difference between the ideal amount of output change per unit of the drive waveform and the output value acquired in step S203, but the present invention is not limited to this.

[0058] In step S205, the microprocessor 116 stores the F-number information acquired in step S204 in the ROM 122. In step S206, the microprocessor 116 determines whether or not all measurements of the drive amount that the aperture unit 114 can drive have been completed. If it is determined that the measurements have been completed, this flow ends, and if it is determined that the measurements have not been completed, the processing of this step is repeated.

[0059] Fig. 10 is a correction table for the amount of deviation between ideal F-number information and actual F-number information. As shown in Fig. 10, the amount of deviation in the F-number is stored as F-number information (correction value) according to the count number of the drive amount for the aperture unit 114. The table of Fig. 10 may be stored for each drive speed. Alternatively, the table may be stored according to factors other than friction that change the load on the aperture blades 114a and 114b, such as the degree of overlap between the aperture blades 114a and 114b, the attitude of the aperture unit 114, the temperature of the stepping motor 109, the cumulative number of drives, etc.

[0060] In this embodiment, when a request to send current F-number information is received after a drive instruction is issued from the camera 200, the correction value table is referenced from the count number of the drive amount count unit 120 at that timing, the current F-number information is acquired, and the acquired information is notified to the camera 200. The camera 200 periodically performs AE control based on the current F-number information received from the photographing lens 100, thereby making it possible to acquire a photometric value from the F-number information realized by the aperture unit 114. This improves exposure accuracy and makes it possible to reduce exposure flicker during video recording. Note that the actual F-number information may be notified to the camera 200 instead of the amount of deviation from the ideal F-number information. [Example]

[0061] In the first and second embodiments, a method for changing the F-number information notified to the camera 200 depending on the driving state of the aperture unit 114 was described. In this embodiment, a method for controlling the aperture unit 114 so that the change in light intensity is constant will be described.

[0062] The configuration of the imaging system of this embodiment is similar to the configuration of the imaging system of Embodiments 1 and 2. In this embodiment, the configuration different from the configuration of Embodiments 1 and 2 will be described, and detailed description of the similar configuration will be omitted.

[0063] FIG. 11 is a flowchart showing the control process of the pulse rate of the drive signal in this embodiment.

[0064] In step S301, the microprocessor 116 determines whether or not there is a drive instruction from the camera 200 to the aperture unit 114. If it is determined that there is a drive instruction, the process proceeds to step S302; if not, the process of this step is repeated.

[0065] In step S302, the microprocessor 116 acquires an ideal output change amount per predetermined period of the motor rotation position detector 117. The predetermined period in this embodiment is a confirmation period of the output of the motor rotation position detector 117, which will be described later.

[0066] In step S303, the microprocessor 116 outputs a drive signal to drive the aperture to the specified drive amount or target F-number, and starts driving the aperture. The pulse rate of the drive signal is changed in accordance with an instruction from the camera 200.

[0067] In step S304, the microprocessor 116 acquires information on the shooting mode of the camera 200 through communication.

[0068] In step S305, microprocessor 116 determines whether the shooting mode of camera 200 acquired in step S304 is the video mode. If it is determined to be the video mode, the process proceeds to step S307, and if it is determined not to be the video mode, the process proceeds to step S306.

[0069] In step S306, the microprocessor 116 drives the aperture unit 114 at the specified speed up to the specified drive amount or target F-number.

[0070] In step S307, microprocessor 116 determines whether a predetermined period has elapsed since the start of aperture drive. The predetermined period may be set in advance as a fixed value in ROM 122. Furthermore, since the amount of change in the output value of motor rotation position detection unit 117 per unit time increases as the pulse rate increases, the predetermined period may be changed according to the pulse rate so that changes in the output value of motor rotation position detection unit 117 can be detected with high resolution. If it is determined that the predetermined period has elapsed, the process proceeds to step S308; if it is determined that the predetermined period has not elapsed, the process proceeds to step S314.

[0071] In step S308, the microprocessor 116 acquires the output value of the motor rotational position detector 117, and also acquires the difference from the previous output value (actual output change amount).

[0072] In step S309, microprocessor 116 determines whether the ideal output change amount obtained in step S302 is greater than the actual output change amount obtained in step S308. If the ideal output change amount is greater than the actual output change amount, the process proceeds to step S310; if not, the process proceeds to step S311.

[0073] In step S310, the microprocessor 116 increases the pulse rate of the drive signal output to the aperture unit 114. The amount of increase may be stored in advance in the ROM 122, or may be changed according to the pulse rate.

[0074] In step S311, microprocessor 116 determines whether the ideal output change amount obtained in step S302 is smaller than the actual output change amount obtained in step S308. If the ideal output change amount is smaller than the actual output change amount, the process proceeds to step S312, and if it is determined that this is not the case, i.e., if the ideal output change amount is equal to the actual output change amount, the process proceeds to step S313.

[0075] In step S312, the microprocessor 116 reduces the pulse rate of the drive signal output to the aperture unit 114. The amount of reduction may be stored in advance in the ROM 122, or may be changed according to the pulse rate.

[0076] In step S313, the microprocessor 116 maintains the pulse rate of the drive signal output to the aperture unit 114.

[0077] In step S314, the microprocessor 116 maintains the pulse rate of the drive signal output to the aperture unit 114.

[0078] In step S315, the microprocessor 116 determines whether the camera has been driven to the drive amount or target F-number instructed by the camera 200. If it is determined that the camera has been driven to the instructed drive amount or target F-number, this flow ends, and if it is determined that the camera has not been driven to the instructed drive amount or target F-number, the flow returns to step S307.

[0079] Figure 12 shows the change in the output of the drive signal when the flow of Figure 11 is executed. The dotted line shows the change in the output of the Hall sensor when the pulse rate of the drive signal is maintained constant. As shown in Figure 12(a), by changing the pulse rate of the drive signal in accordance with the change in the output of the motor rotation position detector 117, it is possible to keep the change in the light amount caused by the aperture unit 114 constant, as shown in Figure 12(b). [Other Examples] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0080] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0081] 100 Photographic lenses (lens devices) 109 Stepping Motor 110 Communications Department 114 Aperture unit (aperture mechanism) 200 Camera (imaging device)

Claims

1. A lens device that is detachably attached to an imaging device, An aperture mechanism that adjusts the amount of light; a stepping motor that drives the aperture mechanism; a communication unit that transmits exposure information based on information about an actual position of the diaphragm mechanism to the imaging device at predetermined intervals; The lens device is characterized in that the predetermined period is changed in accordance with the drive speed of the diaphragm mechanism.

2. The stepping motor further includes a detection unit for detecting a rotational position of a rotor of the stepping motor, 2. The lens device of claim 1, wherein the information regarding the actual position of the diaphragm mechanism is determined based on the rotational position of the rotor.

3. 2. The lens apparatus according to claim 1, wherein the exposure information is actual exposure information obtained based on information about an actual position of the diaphragm mechanism.

4. 2. The lens device according to claim 1, wherein the exposure information is a deviation amount between ideal exposure information and actual exposure information corresponding to an actual position of the diaphragm mechanism.

5. 5. The lens device according to claim 4, wherein the ideal exposure information corresponds to a drive signal for the stepping motor instructed by the imaging device.

6. 6. The lens device according to claim 1, wherein the exposure information is information relating to at least one of an F-number, an AV-number, and a T-number.

7. 2. The lens device according to claim 1, wherein the exposure information is based on information regarding a change in exposure information per predetermined period corresponding to a difference between information regarding the position of the diaphragm mechanism at a first timing and information regarding the position of the diaphragm mechanism at a second timing that is the predetermined period before the first timing.

8. 2. The lens device according to claim 1, wherein the exposure information is based on information regarding a change in the exposure information per predetermined period corresponding to a difference between information regarding the actual position of the diaphragm mechanism per predetermined period and information regarding the ideal position of the diaphragm mechanism per predetermined period.

9. A method for controlling a lens device that is detachably attached to an imaging device and that includes an aperture mechanism that adjusts the amount of light, a stepping motor that drives the aperture mechanism, and a detection unit that detects the rotational position of a rotor of the stepping motor, comprising: obtaining exposure information based on information about the actual position of the aperture mechanism; transmitting the exposure information to the imaging device at predetermined intervals; A control method characterized in that the predetermined period is changed in accordance with a drive speed of the diaphragm mechanism.

10. A program causing a computer to execute the control method according to claim 9.

Images