JP2024068557A - Lens device, method for controlling lens device, and program - Google Patents

Abstract

To provide, for example, a lens device advantageous for detecting an accurate defocus amount.SOLUTION: A lens device (100) has an imaging optical system including a lens group (114) movable for back focus adjustment and is removably attached to an imaging apparatus (200), and the lens device has: an acquisition unit (117) that acquires information on the position of the lens group; a detection unit (119) that detects a defocus amount by using a light beam passing through a part of the imaging optical system on the front side of the lens group; and a processing unit (121) that corrects the defocus amount based on the information on the position of the lens group.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lens device, a control method for a lens device, and a program.

There are known methods for correcting detection errors in the defocus amount in autofocus (AF) processing in imaging devices. Patent Document 1 discloses a method for correcting the back focus adjustment amount when performing external measurement AF so that the target position of the external measurement AF coincides with the target position of the contrast AF. Patent Document 2 discloses storing the positions of each of a pair of phase difference AF sensors and correcting the output of each sensor based on the stored positions.

JP 2006-235351 A JP 2014-81462 A

The method disclosed in Patent Document 1 requires that AF can be performed using multiple methods. In the method disclosed in Patent Document 2, if the back focus (flange back) changes over time due to changes in temperature or air pressure, a detection error in the amount of defocus may occur.

The present invention aims to provide a lens device that is advantageous for detecting the amount of defocus accurately, for example.

A lens device according to one aspect of the present invention has an imaging optical system including a movable lens group for back focus adjustment, and is detachable from an imaging device. The lens device has an acquisition unit that acquires information regarding the position of the lens group, a detection unit that detects the amount of defocus from a light beam that has passed through a part of the imaging optical system in front of the lens group, and a processing unit that corrects the amount of defocus based on the information regarding the position of the lens group.

Other objects and features of the present invention are described in the following embodiments.

The present invention can provide, for example, a lens device that is advantageous for detecting the amount of defocus accurately.

1 is a configuration diagram of an imaging system according to a first embodiment. FIG. 4 is a schematic diagram of a back correction value in each embodiment. 10 is a flowchart showing a process for setting adjustment information in the first embodiment. 10 is a flowchart illustrating a process for clearing adjustment information in each embodiment. FIG. 13 is a configuration diagram of an imaging system according to a second embodiment. 13 is a flowchart showing a process for setting adjustment information in the second embodiment.

The following describes in detail an embodiment of the present invention with reference to the drawings.

First Embodiment
An image capturing system 10 according to a first embodiment of the present invention will be described below with reference to Fig. 1. Fig. 1 is a configuration diagram of the image capturing system 10. The image capturing system 10 is configured to include an image capturing device (camera body) 200, and a lens device (interchangeable lens) 100 that is detachable from the image capturing device 200.

The lens device 100 has a focus lens 101 that constitutes part of the imaging optical system, and moves in a direction along the optical axis OA of the imaging optical system (optical axis direction) to change the position of the image plane of the lens device 100. A focus motor 102 is connected to the focus lens 101. The focus motor 102 is driven by a focus driver 103 to move the focus lens 101 in the optical axis direction. The focus driver 103 is a drive unit that drives the focus lens 101 based on the defocus amount. The position of the focus lens 101 is detected by a focus position detection unit 104 such as an encoder.

The zoom lens 105 constitutes part of the imaging optical system, and moves in the optical axis direction to change the focal length of the lens device 100. A zoom motor 106 is connected to the zoom lens 105. The zoom motor 106 is driven by a zoom driver 107 to drive the zoom lens 105 in the optical axis direction. The position of the zoom lens 105 is detected by a zoom detection unit 108 such as an encoder.

An iris motor 110 is connected to the movable diaphragm (aperture diaphragm) 109. The iris motor 110 is driven by an iris driver 111 and drives the movable diaphragm 109. The position of the movable diaphragm 109 is detected by an iris position detection unit 112 such as an encoder.

The spectroscopic prism 113 separates the light that has passed through the focus lens 101 and the zoom lens 105 into two beams. One of the beams that passes through the spectroscopic prism 113 is incident on the image sensor 201 of the imaging device 200 via the back focus lens 114. The other beam that is reflected by the spectroscopic prism 113 is incident on the focus detection unit 119.

The focus detection unit 119 has a phase difference detection lens and a phase difference detection sensor, and photoelectrically converts a pair of images (two images) formed by two light beams split by the phase difference detection lens using the phase difference sensor. In other words, the focus detection unit 119 is a detection unit that detects the amount of defocus using the light beam that has passed through a part of the imaging optical system in front of the back focus lens 114.

The back focus lens 114 is a lens group that is movable in the optical axis direction to change the back focus of the lens device 100 (to perform back focus adjustment). A back focus motor 115 is connected to the back focus lens 114. The back focus motor 115 is driven by a back focus driver 116 to drive the back focus lens 114 in the optical axis direction. The back focus position detection unit 117 is an acquisition unit that acquires the position (information regarding the position) of the back focus lens 114, and has, for example, an encoder. The back focus lens 114 can also be driven from the outside using a back focus adjustment knob 118 that is engaged with a gear (not shown). The back focus adjustment knob 118 is an operation unit that can be operated by the user, but another operation unit may be used.

Here, due to manufacturing errors in the lens device 100 or the imaging device 200, or changes in environmental temperature or air pressure, the actual distance from the flange surface of the lens device 100 to the imaging element 201 may change with respect to the designed flange back of the lens device 100. If the back focus is not adjusted, there is a possibility that focus adjustment cannot be performed no matter how much the focus lens 101 is operated. For this reason, the user needs to accurately adjust the back focus to match the actual flange back for the combination of the lens device 100 and the imaging device 200 used for shooting before shooting. As a method of adjustment, the back focus lens 114 is moved by driving the back focus motor 115 or by the user operating the back focus adjustment knob 118.

The lens CPU 120 has a correction unit 121, a focus calculation unit 122, a lens control unit 123, an adjustment information storage unit 124, and a lens communication unit 125. The lens control unit 123 controls the driving of the focus lens 101 based on the calculation result of the focus calculation unit 122. The lens control unit 123 also controls the zoom lens 105, the adjustable aperture 109, and the back focus lens 114.

The correction unit 121 is a processing unit that corrects a pair of image signals (output signals of the focus detection unit 119) that are part of the shooting light beam photoelectrically converted by the focus detection unit 119. More specifically, the correction unit 121 corrects the defocus amount based on information about the position of the back focus lens 114 detected by the back focus position detection unit 117. This will be described in detail later.

The focus calculation unit 122 is a defocus amount calculation unit that calculates a defocus amount based on the phase difference between a pair of image signals corrected by the correction unit 121. The adjustment information storage unit 124 is a storage unit that stores position information of the back focus lens 114 when the imaging device 200 is attached, and changes the position information based on the correction amount changed by the correction unit 121. Details of this will be described later.

The lens communication unit 125 is a communication unit that communicates with the camera communication unit 202 of the imaging device 200. When the lens communication unit 125 receives a command or request from the camera communication unit 202, it outputs the command to the lens control unit 123. Conversely, when the lens communication unit 125 receives information from the lens control unit 123 in response to a command or request from the camera communication unit 202, it transmits the information that has been input to the camera communication unit 202. Here, commands from the camera communication unit 202 include, for example, a drive command to the focus lens 101 for adjusting the focus, or a drive command to the back focus lens 114 for adjusting the back focus.

Next, the correction unit 121 will be described with reference to FIG. 2. FIG. 2 is an explanatory diagram of the correction value in the correction unit 121, and shows a side view of the phase difference detection sensor 301 of the focus detection unit 119. A solid line 302 indicates the ideal position of the phase difference detection sensor 301 in a steady state. The position of the phase difference detection sensor 301 is adjusted during manufacturing so as to be as close as possible to the ideal position shown by the solid line 302. However, in reality, the position of the phase difference detection sensor 301 deviates from the ideal position due to factors such as tilting and distortion. For this reason, a correction value corresponding to the amount of deviation from the ideal position is stored in a non-volatile memory (not shown) as a sensor back correction value 303 (303a, 303b, 303c). Then, by applying the stored sensor back correction value 303 during calculation by the focus calculation unit 122, high-precision focus detection can be performed.

The dashed line 304 indicates the ideal position of the phase difference detection sensor 301 when a shift in the back relationship occurs due to environmental factors such as changes in temperature and air pressure caused by differences in optical sensitivity between the imaging system and the focus detection system. Here, when the back focus of the imaging system shifts due to temperature or air temperature, the user can adjust it by driving the back focus lens 114, but it is difficult to adjust the back of the focus detection system. In other words, a back shift 305 between the imaging system and the focus detection system can occur due to external factors such as temperature and air pressure.

Next, the adjustment information storage unit 124 will be described with reference to Figures 3 and 4. Figure 3 is a flowchart showing the process of setting adjustment information, and shows the setting conditions of the adjustment information in the adjustment information storage unit 124 and the method of calculating the correction value.

First, in step S401, back focus adjustment is performed by user operation. Here, the back focus adjustment is performed by manual adjustment by user operation of the back focus adjustment knob 118, or by a drive command from the imaging device 200 via the lens communication unit 125. Next, in step S402, the lens CPU 120 determines whether the back focus adjustment is completed. If it is determined that the back focus adjustment is completed, the process proceeds to step S403. On the other hand, if it is determined that the back focus adjustment is not completed, the process returns to step S401. Here, in the case of a user operation using the back focus adjustment knob 118, the completion of the back focus adjustment is determined by the elapse of time from the locked state after the user operation is completed. For example, if the position information does not change within a predetermined period after the lens device 100 is attached to the imaging device 200, it is determined that the back focus adjustment is completed. Alternatively, the completion of the back focus adjustment may be determined by the input of an operation completion button (not shown) from the user. Also, in the case of a drive command from the imaging device 200, a completion notification is performed by communication via the lens communication unit 125.

Next, in step S403, the lens CPU 120 determines whether or not the adjustment information is stored in the adjustment information storage unit 124. If it is determined that the adjustment information is stored, the process proceeds to step S404. On the other hand, if it is determined that the adjustment information is not stored, the process proceeds to step S405. Here, the adjustment information includes at least the position information when the adjustment of the back focus lens 114 is completed for the first time after the lens device 100 is attached to the imaging device 200.

In step S404, the lens CPU 120 stores the current position information of the back-focus lens 114 as adjustment information in the adjustment information storage unit 124. This step is executed when adjustment of the back-focus lens 114 is completed for the first time after it is attached to the imaging device 200. In this way, the adjustment information storage unit 124 stores position information acquired in response to a notification from the imaging device 200 via the lens communication unit 125, or position information acquired in response to a user operation of the back-focus adjustment knob 118.

In step S405, the lens CPU 120 updates (changes) the correction value (updates the adjustment information stored in the adjustment information storage unit 124). This step is executed when readjustment of the adjusted back-focus lens 114 is necessary due to an external factor such as an environmental change. The lens CPU 120 acquires the difference (back-focus lens displacement amount) between the position information of the back-focus lens 114 (reference position information) stored in the adjustment information storage unit 124 and the current position information of the back-focus lens 114. The lens CPU 120 then calculates the correction value of the focus detection system (AF system correction amount) based on the back-focus lens displacement amount.

In this embodiment, the correction value corresponding to the difference is calculated, for example, by referring to Table 1 below. Table 1 shows the correction value (AF system correction amount (μm)) according to the optical sensitivity (back focus displacement amount (μm)) of the imaging system and focus detection system in the adjustment information storage unit 124, and is table data showing the relationship between the back focus displacement amount and the AF system correction amount.

FIG. 4 is a flowchart showing the process of clearing (initializing) the adjustment information, and shows the conditions for clearing the adjustment information stored in the adjustment information storage unit 124. First, in step S501, the lens CPU 120 determines whether or not it has detected that the lens device 100 has been removed from the imaging device 200. This detection determination is performed, for example, by a mechanical switch or communication from the imaging device 200. If it is determined that it has been detected that the lens device 100 has been removed from the imaging device 200, in step S502, the lens CPU 120 clears (initializes) the adjustment information stored in the adjustment information storage unit 124.

In this embodiment, the correction unit 121 obtains a correction value (correction value corresponding to the difference) for the focus detection system using table data such as Table 1, but is not limited to this. The correction unit 121 may, for example, use a polynomial to calculate a correction value corresponding to the difference in optical sensitivity between the imaging system and the focus detection system (the correction value may be obtained by calculation based on the difference).

According to this embodiment, if the back focus of the imaging system is readjusted due to an external factor such as an environmental change, and a shift occurs in the back relationship between the imaging system and the focus detection system, it is possible to appropriately correct the back shift of the focus detection system.

Second Embodiment
Next, an imaging system 10a according to a second embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 is a configuration diagram of the imaging system 10a. The imaging system 10a is configured to include an imaging device (camera body) 200 and a lens device (interchangeable lens) 100a that is detachable from the imaging device 200. The lens device 100a differs from the lens device 100 of the first embodiment in that it has a temperature sensor 501. Note that in this embodiment, a description of the same configuration as the imaging system 10 of the first embodiment will be omitted.

The temperature sensor 501 is a temperature detection means for detecting the temperature (temperature information) of the lens device 100, and includes, for example, a thermistor. The adjustment information storage unit 124 stores the output value (first temperature information) of the temperature sensor 501 acquired at the timing when the sensor back correction value 303 is stored (when adjusting the lens device 100).

Next, the adjustment information storage unit 124 will be described with reference to FIG. 6. FIG. 6 is a flowchart showing the process of setting adjustment information. Note that in FIG. 6, the same process (steps S401 to S403) as in FIG. 3 will not be described.

In step S601, the lens CPU 120 stores the output value of the temperature sensor 501 (second temperature information) together with the position information of the back focus lens 114 as adjustment information in the adjustment information storage unit 124.

In step S602, the current output value (third temperature information) of the temperature sensor 501 is stored. Then, in step S603, the lens CPU 120 compares the temperature information at the timing when the sensor back correction value 303 was acquired, the temperature information at the timing when the position information of the back focus lens 114 was stored, and the current temperature information. Depending on the comparison result, the process proceeds to a different step.

If the comparison result of the temperature information is any of the following results (1) to (4), the process proceeds to step S604. In step S604, the lens CPU 120 refers to Table 1 and calculates the correction value of the focus detection system.
(1) The first temperature information, the second temperature information, and the third temperature information are all close to each other. (2) The second temperature information and the third temperature information are close to each other, and the first temperature information is different. (3) The first temperature information and the second temperature information are close to each other, and the third temperature information is different. (4) The first temperature information, the second temperature information, and the third temperature information are all different. In the cases of results (1) and (2), it is considered that the back focus shift of the imaging system has occurred due to an external factor other than temperature. On the other hand, in the cases of results (3) and (4), it is considered that the back focus shift of the imaging system has occurred due to temperature. In other words, only when the first temperature information and the third temperature information are close to each other, and the second temperature information is different (result (5)), this flow is terminated without calculating the correction value of the focus detection system. This is because the fact that the first temperature information and the second temperature information are different means that it is considered that the back focus shift of the imaging system and the focus detection system has occurred at the time when the second temperature information is acquired. In addition, the fact that the first temperature information and the third temperature information are close means that it is considered that the back focus shift of the imaging system and the focus detection system has also returned to the original state.

In this embodiment, the back adjustment of the focus detection system is performed in response to the temperature information obtained from the temperature sensor 501, but this is not limited to this, and for example, an air pressure sensor may also be used.

Other Embodiments
The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

According to each embodiment, for example, it is possible to provide a lens device, a control method for the lens device, and a program that are advantageous for detecting an accurate defocus amount.

The disclosure of each embodiment includes the following configurations and methods:

(Configuration 1)
A lens device having an imaging optical system including a movable lens group for back focus adjustment, the lens device being detachable from an imaging device,
an acquisition unit that acquires information regarding the position of the lens group;
a detection unit that detects a defocus amount based on a light beam that has passed through a portion of the imaging optical system located in front of the lens group;
and a processing unit that corrects the defocus amount based on information regarding the position of the lens group.
(Configuration 2)
2. The lens apparatus according to configuration 1, wherein the acquisition unit detects at least one of a position of the lens group and a state of the lens apparatus.
(Configuration 3)
3. The lens device according to configuration 1 or 2, wherein the state of the lens device includes at least one of temperature, humidity, air pressure, attitude, and insertion/removal of a variable magnification optical system in the lens device.
(Configuration 4)
4. The lens apparatus according to any one of configurations 1 to 3, wherein the processing unit stores a correction amount for the defocus amount in association with information relating to the position of the lens group.
(Configuration 5)
3. The lens apparatus according to claim 2, wherein the processing unit calculates a correction amount for the defocus amount based on information relating to the position of the lens group.
(Configuration 6)
a storage unit that stores information regarding the position of the lens group;
3. The lens apparatus according to claim 2, wherein the processing unit corrects the defocus amount based on a change in information relating to the positions of the lens groups.
(Configuration 7)
An operation unit operable by a user;
7. The lens apparatus according to configuration 6, wherein the processing unit stores information relating to the positions of the lens group in the storage unit based on an operation of the operation unit.
(Configuration 8)
7. The lens apparatus according to configuration 6, wherein the processing unit stores information regarding the positions of the lens group in the storage unit based on a change in the information regarding the positions of the lens group.
(Configuration 9)
The lens device described in any one of configurations 6 to 8, wherein the processing unit initializes information regarding the positions of the lens group stored in the memory unit when the lens device is detached from the imaging device.
(Configuration 10)
the imaging optical system includes a focus lens group that is driven for focusing;
10. The lens apparatus according to any one of configurations 1 to 9, further comprising a drive section that drives the focus lens group based on the defocus amount corrected by the processing section.
(Method 1)
A method for a lens apparatus having an imaging optical system including a movable lens group for back focus adjustment and detachable from an imaging device, comprising:
obtaining information regarding the position of the lens group;
a defocus amount is detected based on a light beam passing through a portion of the imaging optical system in front of the lens group;
and correcting the amount of defocus based on information about the position of the lens group.
(Configuration 11)
A program causing a computer to execute the method described in Method 1.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments, and various modifications and variations are possible within the scope of the gist of the invention.

100 Lens device 114 Back focus lens (lens group)
117 Back focus position detection unit (acquisition unit)
119 Focus detection unit (detection unit)
121 Correction unit (processing unit)
200 Imaging device

Claims (12)

A lens device having an imaging optical system including a movable lens group for back focus adjustment, the lens device being detachable from an imaging device,
an acquisition unit that acquires information regarding the position of the lens group;
a detection unit that detects a defocus amount based on a light beam that has passed through a portion of the imaging optical system located in front of the lens group;
and a processing unit that corrects the defocus amount based on information regarding a position of the lens group. The lens device according to claim 1, characterized in that the acquisition unit detects at least one of the position of the lens group and the state of the lens device. The lens device according to claim 1, characterized in that the state of the lens device includes at least one of the temperature, humidity, air pressure, attitude, and insertion/removal of a variable magnification optical system in the lens device. The lens device according to claim 1, characterized in that the processing unit stores a correction amount for the defocus amount in association with information regarding the position of the lens group. The lens device according to claim 2, characterized in that the processing unit calculates a correction amount for the defocus amount based on information about the position of the lens group. a storage unit that stores information regarding the position of the lens group;
The lens apparatus according to claim 2 , wherein the processing unit corrects the defocus amount based on a change in information relating to the positions of the lens groups. An operation unit operable by a user;
The lens device according to claim 6 , wherein the processing unit stores information relating to the positions of the lens group in the storage unit based on an operation of the operation unit. The lens device according to claim 6, characterized in that the processing unit stores information about the position of the lens group in the storage unit based on a change in the information about the position of the lens group. The lens device according to claim 6, characterized in that the processing unit initializes information about the positions of the lens group stored in the memory unit when the lens device is removed from the imaging device. the imaging optical system includes a focus lens group that is driven for focusing;
10. The lens apparatus according to claim 1, further comprising a drive section that drives the focus lens group based on the defocus amount corrected by the processing section. A method for a lens apparatus having an imaging optical system including a movable lens group for back focus adjustment and detachable from an imaging device, comprising:
obtaining information regarding the position of the lens group;
a defocus amount is detected based on a light beam passing through a portion of the imaging optical system in front of the lens group;
and correcting the amount of defocus based on information about the position of the lens group. A program that causes a computer to execute the method according to claim 11.