JP2019028318A - Lens device and imaging apparatus having the same - Google Patents

Abstract

To provide a lens device capable of preventing fogging due to dew condensation in a configuration that achieves power saving and reduces the frequency of maintenance.SOLUTION: The lens device includes an optical member, an optical holding part holding the optical member, and an exterior member covering the optical holding part, and the lens device has thermal conduction means capable of conducting external heat of the lens device to the optical member via the exterior member, and a control unit for controlling the thermal conduction means. The control unit switches, in response to the external temperature of the lens device and the temperature of the optical member, between a conduction state where the thermal conduction means conducts the external heat to the optical member and a non-conduction state where the means does not conduct heat.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a lens device and an imaging device having the lens device.

  The lens device is also used in an environment in which the temperature outside the lens device suddenly rises, for example, when the lens device is moved from a cooled room to the outside. In such a case, there is a problem that the lens is condensed and cloudy.

  When the external temperature of the lens apparatus rapidly increases, a pressure difference is generated inside and outside the lens apparatus, and high temperature outside air flows in the vicinity of the lens. If the lens is not sufficiently warmed at this time, the surface of the lens becomes lower than the dew point temperature of the outside air, and condensation occurs.

  The dew point temperature is a temperature at which water vapor in the air begins to condense when cooling air in a space where the amount of water vapor is constant. If the temperature is higher than the dew point temperature, condensation does not occur, and if it is lower, condensation occurs.

  In particular, in a lens device having a cover that can be attached to and detached from the lens barrel, a space is provided between the cover and the lens barrel for attaching and detaching the cover. Since this space becomes a heat insulating layer between the outside and the lens, the heat of the outside air is more difficult to transfer to the lens, and condensation is likely to occur.

  Conventionally, a method of heating or keeping a temperature of a lens is known. In patent document 1, the structure which heats glass with a heater is disclosed. Also known is a method of reducing the dew point temperature by installing a desiccant or enclosing dry air to reduce the amount of water vapor in the lens device, thereby increasing the lens temperature margin with respect to the dew point temperature. Patent Document 2 discloses a technique for filling a lens device with a desiccant to reduce the amount of water vapor.

JP 2007-256849 A JP-A-6-258561

  However, the configuration disclosed in Patent Document 1 has a problem of increasing power consumption because it generates heat using electric power.

  In the configuration disclosed in Patent Document 2, since it is necessary to periodically replace the desiccant, there is a problem that burdens the user in terms of maintenance.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a lens apparatus that can prevent fogging due to condensation with a configuration that reduces power consumption and maintenance frequency.

  In order to achieve the above object, the present invention provides a lens device that includes an optical member, an optical holding unit that holds the optical member, and an exterior member that covers the optical holding unit. Heat conduction means capable of conducting heat outside the lens device to the optical member, and a control unit for controlling the heat conduction means, the control unit comprising a temperature outside the lens device, and According to the temperature of the optical member, the heat conducting means switches between a conductive state in which the external heat is conducted to the optical member and a non-conductive state in which the heat is not conducted.

  According to the present invention, it is possible to provide a lens device that can prevent fogging due to dew condensation with a configuration that reduces power consumption and maintenance frequency.

Overall schematic diagram in this embodiment Conceptual diagram in each state of (a) and (b) of part B in FIG. Flowchart of operation of heat conduction means in embodiment 1 Conceptual diagram of the lens barrel of Example 2 Flowchart of operation of heat conduction means in embodiment 2 Flowchart of operation of heat conduction means in embodiment 3

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1
FIG. 1 is a schematic view showing the entirety of a first embodiment of the present invention. A part of FIG. 1 shows an internal structure. FIG. 2 shows a conductive state (a) in which a heat conduction path is formed between the lens and the exterior member, and a non-conductive state in which there is an air layer between the lens and the exterior member and no heat conduction path is formed. It is a detailed view of the B section in FIG. 1 in (b). Details of the conduction state and the non-conduction state will be described later.

(Configuration of lens device)
The exterior member 1 is detachably attached to the lens barrel (optical holding member) 2 in the direction of the optical axis O of the lens 3. There is a space between the exterior member 1 and the lens barrel 2, and the exterior member 1 covers the entire lens barrel 2 so as to surround the optical axis O of the lens 3.

  The lens barrel 2 has an outer holding member 2 a provided on the exterior member 1 side and an inner holding member 2 b provided on the lens (optical member) 3 side, and these are connected to each other by screws 7.

  The lens 3 is held on the inner holding member 2 b of the lens barrel 2 by a presser ring 8. The lens device is a zoom lens having a lens group including a focus group including the lens 3 from the subject side, a variator group (not shown), a compensator group (not shown), and a relay group (not shown). Is not limited to this. The lens 3 may be a lens other than the focus group.

  In addition, although the lens 3 of a present Example is comprised with glass, even if it is a lens comprised with resin, the effect of this invention can be acquired.

(Sensor configuration)
The exterior member 1 includes a temperature sensor (first acquisition unit) 15 inside. The temperature sensor 15 detects the temperature of the exterior member 1 as the temperature outside the lens device L1. In this embodiment, the exterior member 1 is made of metal and has a good thermal conductivity, so that it can be used by changing the temperature outside the lens device L1.

  The inner holding member 2 b constituting the lens barrel 2 includes a temperature sensor (second acquisition unit) 13. The temperature sensor 13 detects the temperature of the inner holding member 2b (second temperature) in order to obtain the temperature of the lens 3 indirectly.

  Note that the temperature outside the lens device L1 may be acquired, for example, by a temperature sensor provided outside the exterior member. For example, the structure which acquires the information from the temperature sensor provided in the imaging device (not shown) which the lens apparatus L1 connects may be sufficient. Further, for example, a configuration in which the photographer inputs the temperature of the outside air may be used.

(Heat conduction means)
As shown in FIG. 2, the heat conducting means in the present embodiment includes a heat conducting unit 11 and a drive unit 20 that drives the heat conducting unit 11.

  The heat conducting unit 11 is a member having a higher thermal conductivity than air. For example, a metal such as aluminum having a high thermal conductivity is preferable. Further, the heat conducting portion 11 has a convex portion, and a screw hole is formed in the convex portion. The convex portion may be a separate structure or an insert structure.

  The drive unit 20 includes a motor unit 21 and a drive shaft unit 22.

  The drive shaft portion 22 includes a shaft 22a, a bearing 22b, and a holding member 22c. The bearing 22b is a member that rotatably supports the shaft 22a, and is provided at two locations with respect to the shaft 22b. Each bearing 22b is fitted and fixed to the holding member 22c. The shaft 22a is threaded and is screwed into a screw hole formed in the convex portion of the heat conducting portion 11.

  With the above configuration, the drive shaft portion 22 is a screw feed mechanism capable of moving the heat conducting portion 11 in the extending direction of the shaft 22a when the shaft 22a rotates.

  The motor unit 21 includes a motor 21a, a gear 21b, and a motor holding member 21c. The motor 21a is engaged with the shaft 22a by the gear 21b, thereby transmitting a driving force to the driving shaft portion 22 of the heat conducting unit 11.

  The heat conducting unit 11 is disposed so as to contact the lens barrel 2. As shown in FIG. 2A, the heat conducting unit 11 can come into contact with the lens barrel 2 and the exterior member 1 to form a heat transfer path between the exterior member 1 and the lens 3 by the drive unit 20. Thus, the heat conduction means can take a state in which external heat can be conducted to the lens 3 through the exterior member 1, and this state is a conduction state in this embodiment.

  Further, as shown in FIG. 2B, the heat conducting portion 11 contacts only the lens barrel 2 and does not form a heat transfer path between the exterior member 1 and the lens 3. This state is a non-transmission state in the present embodiment.

  The motor 21a is driven based on a control signal from the control unit. In the present embodiment, the control unit can switch between the conduction state of FIG. 2A and the non-conduction state of FIG. 2B.

  The control unit 23 can acquire the temperature information of the temperature sensor 13 and the temperature sensor 15 which are each acquisition unit.

(Operation and effect)
Hereinafter, the operation and effect of the present embodiment will be described. First, each process is demonstrated based on the flowchart of FIG. 3 about the control process which drives the heat conduction part 11 which the control part 23 performs. The control unit 23 executes this processing in accordance with an operation control program as a computer program.

(Control processing)
In S <b> 101, the control unit 23 acquires information on the temperature TG of the inner holding member 2 b that is part of the lens barrel 2 detected by the temperature sensor 13 and information on the temperature TO of the exterior member 1 detected by the temperature sensor 15. . As described above, TG is temperature information indirectly indicating the surface temperature of the glass, and TO is information as the temperature outside the exterior member.

  In S105, the control unit 23 determines whether the temperature TO of the exterior member 1 is higher than the temperature TG of the inner holding member 2b (TO> TG) using the information acquired in S101.

  In S105, when it is determined that the temperature TO of the exterior member 1 is higher than the temperature TG of the inner holding member 2b (TO> TG), the control unit 23 controls the motor 21a in S106 to control the heat conducting unit 11 and the exterior. The member 1 is brought into contact and brought into a conductive state. Thereafter, the process ends.

  In S105, when it is determined that the temperature TO of the exterior member 1 is equal to or lower than the temperature TG of the inner holding member 2b (TO ≦ TG), the control unit 23 controls the motor 21a in S107 to control the heat conducting unit 11 and the exterior member. 1 is made non-conductive. Thereafter, the process ends.

  The above processing and determination are repeatedly executed at predetermined time intervals.

(effect)
With the above configuration, if the external temperature of the exterior member 1 is high, the conductive state shown in FIG. 2A is taken to bring the optical member into a conductive state that conducts its heat, and the temperature of the optical member is about the same as the outside air temperature. It becomes possible. Therefore, dew condensation can be prevented even when the external temperature rises rapidly.

  On the other hand, when the temperature outside the exterior member 1 rapidly decreases in the conductive state of FIG. 2A, the heat of the lens 3 is rapidly deprived. If the temperature of the surface of the lens 3 becomes equal to or lower than the dew point of the air in the space before the air in the space surrounded by the lens 3 and the lens barrel 2 is in equilibrium with the outside air, condensation begins to occur.

  Therefore, as in the present embodiment, when the temperature of the lens 3 is equal to or lower than the temperature outside the exterior member 1, the non-conductive state shown in FIG. When lowered, the heat conduction between the lens 3 and the exterior member 1 can be cut off. If it does so, it can suppress that a heat | fever is rapidly taken from the glass lens 3, and it can prevent that the surface temperature of the lens 3 becomes relatively lower than dew point temperature. Accordingly, the number of scenes in which the lens apparatus can be used in an environment with a large temperature change is increased, including the case where the external temperature is drastically decreased, and convenience is improved.

  In addition, since it is not necessary to always supply power for heat conduction, the power consumption of the lens device can be reduced.

  Further, frequent maintenance is not required as compared with a conventional configuration such as filling with a drying material, and the burden on the user is reduced.

  Furthermore, the configuration of the present embodiment is a simple configuration and does not increase the size or weight of the lens device.

  As a secondary effect, when the structure can be switched between the conductive state in FIG. 2A and the non-conductive state in FIG. 2B, when the exterior member 1 is detached from the lens barrel 2, The contact with the exterior member 1 can be prevented, and workability can be improved.

  For example, a sensor capable of acquiring a state in which the exterior member 1 is mounted at a predetermined position of the lens barrel 2 and a state in which the exterior member 1 is not mounted is configured in the lens barrel 2. For example, a sensor such as a photo interrupter or a micro switch can be used. When the sensor detects that the exterior member 1 is not mounted at a predetermined position, the control unit 23 controls the motor 21a so that the heat conducting means is in a non-conducting state in FIG. With this configuration, the exterior member 1 can be attached to and detached from the lens barrel 2 with the heat transfer means retracted so as not to contact the exterior member 1.

(Example 2)
The second embodiment is different in sensor configuration and control processing for driving the heat conducting unit 11 of the control unit 23. Hereinafter, the same configurations and the same control processes as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

(Sensor configuration)
First, the sensor configuration of this embodiment will be described with reference to FIG. FIG. 4 shows a conductive state (a) in which a heat conduction path is formed between the lens and the exterior member, and a non-conductive state in which there is an air layer between the lens and the exterior member and no heat conduction path is formed. It is a detailed view of the heat conduction means in (b).

  In the lens device L1 in the present embodiment, a temperature / humidity sensor (third acquisition unit) 14 is added to the configuration of the first embodiment.

  The temperature / humidity sensor 14 detects the temperature and humidity of the internal space IN in order to acquire the dew point temperature of the internal space IN (the space surrounded by the lens barrel 2 and the lens 3) of the lens device L2. In the present embodiment, the temperature / humidity sensor 14 is provided on the outer holding member 2a, but the attachment position is not limited to this as long as the temperature / humidity of the internal space IN can be detected. For example, you may attach to the inner side holding member 2b.

  In this embodiment, the temperature / humidity sensor 14 is configured as a dew point temperature acquisition unit. However, the present invention is not limited to this as long as the dew point temperature can be acquired. For example, it is possible to configure a dew point thermometer and directly acquire information on the dew point temperature.

(Control processing)
Each process is demonstrated about the control process which drives the heat conduction part 11 which the control part 23 performs based on the flowchart of FIG. The control unit 23 executes this processing in accordance with an operation control program as a computer program.

  In S201, the control unit 23 detects the temperature TG information of the inner holding member 2b detected by the temperature sensor 13, the temperature / humidity information inside the lens device detected by the temperature / humidity sensor 14, and the exterior member 1 detected by the temperature sensor 15. The temperature TO information is acquired.

  In S202, the control unit 23 acquires the dew point temperature TC of the air in the internal space IN of the lens device from the temperature and humidity information in the lens device acquired in S201. The control unit 23 may acquire the dew point temperature TC with reference to a table stored in advance, for example. Alternatively, the dew point temperature TC may be calculated from the acquired temperature and humidity. Note that S202 is not necessary when a dew point thermometer is configured to directly acquire the dew point temperature.

  In S203, the control unit 23 determines whether or not the temperature TG of the inner holding member 2b is higher than the dew point temperature TC (TG> TC).

  When the temperature of the inner holding member 2b is higher than the dew point temperature (TG> TC), there is a high possibility that condensation has not occurred. Therefore, when the control unit 23 determines in S203 that the temperature TG of the inner holding member 2b is higher than the dew point temperature TC, the process proceeds to S107. In S107, the control part 23 makes the heat conducting part 11 and the exterior member 1 non-conductive. Thereafter, the process ends.

  When the temperature of the inner holding member 2b is equal to or lower than the dew point temperature (TG ≦ TC), there is a high possibility that the lens 3 is condensed or starts to condense. Therefore, if the control unit 23 determines in S203 that the temperature TG of the inner holding member 2b is equal to or lower than the dew point temperature TC, the process proceeds to S105. The processes after S105 are the same as those in the first embodiment, and will be omitted.

(effect)
In the present embodiment, in addition to the effects of the first embodiment, the motor 21a can be driven only when there is a high possibility that condensation has occurred.

  In addition, excessive heat transfer to the lens may lead to deterioration of optical performance, but the lens device of this embodiment prevents this because it does not cause unnecessary heat transfer to the lens without condensation. Can do.

(Modification)
In this embodiment, the space in which the temperature / humidity sensor 14 acquires the dew point temperature is the internal space IN surrounded by the lens barrel 2 and the lens 3. However, as long as the dew point temperature in the space near the lens 3 can be acquired, the space from which the dew point temperature is acquired is not limited to this. For example, the dew point temperature of the space on the objective side of the lens barrel 2 surrounded by the lens barrel 2, the lens 3, and a cover glass (not shown) provided at the object-side tip of the lens barrel 2 is acquired. In addition, the effect of the present embodiment can be obtained. Further, by utilizing both of these dew point temperatures, it is possible to more reliably prevent condensation on both the objective surface and the imaging surface side surface of the lens 3.

(Example 3)
Subsequently, a third embodiment will be described. The third embodiment differs from the second embodiment in the control processing of the control unit 23. Hereinafter, the same configurations and the same control processes as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.

(Control processing)
Each process is demonstrated based on the flowchart of FIG. 6 about the control process which drives the heat conduction part 11 which the control part 23 performs. The control unit 23 executes this processing in accordance with an operation control program as a computer program.

  In S203, the control unit 23 determines whether the temperature TG of the inner holding member 2b is higher than the dew point temperature TC (TG> TC).

  In S203, when it is determined that the temperature TG of the inner holding member 2b is higher than the dew point temperature TC (that is, there is a high possibility that there is no condensation), the control unit 23 in this embodiment proceeds to S304.

  In S304, the control unit 23 determines that the temperature difference ΔT (= TG−TC) between the temperature TG of the inner holding member 2b and the dew point temperature TC is equal to or less than a predetermined threshold value (predetermined temperature difference) TH (ΔT ≦ TH). It is determined whether it is.

  In S304, when it is determined that the temperature difference ΔT between the temperature TG of the inner holding member 2b and the dew point temperature TC is larger than the predetermined threshold value TH (ΔT> TH), the control unit 23 proceeds to S107. In S107, the control part 23 makes the heat conducting part 11 and the exterior member 1 non-conductive. Thereafter, the process ends.

  The predetermined threshold value TH is a value that is set as a margin until condensation occurs. If the temperature difference ΔT is larger than a predetermined threshold TH set in advance, it indicates that the temperature of the surface of the lens 3 exceeds the dew point temperature with a sufficient margin. That is, it can be said that the possibility of condensation on the lens 3 or in the future is considerably low. Therefore, the control unit 23 gives priority to the suppression of the deterioration of the optical performance and sets the heat conducting means to the non-conducting state.

  If it is determined in S304 that the temperature difference between the temperature TG of the inner holding member 2b and the dew point temperature TC (ΔT = TG−TC) is equal to or less than a predetermined threshold (ΔT ≦ TH), the process proceeds to S105. The processes after S105 are the same as those in the first embodiment, and will be omitted.

  If the temperature difference ΔT is equal to or less than a preset temperature difference TH, this means that the temperature margin for condensation is small, and the lens device L1 is expected to have a high possibility of condensation in the future. . Therefore, in order to prevent condensation, the control unit 23 continues to determine whether to transfer the heat of the outside air (steps after S105).

(Specific examples, effects)
Hereinafter, the predetermined temperature margin TH is 5 degrees, the temperature TG of the inner holding member 2b is higher than the dew point temperature TC of the air inside the lens apparatus (that is, no condensation occurs), and the temperature difference ΔT is 3 degrees. In the case of, the control process of the control part 23 is illustrated.

  In S203, the control unit 23 proceeds to S304 because the temperature TG of the inner holding member 2b is higher than the dew point temperature TC of the air inside the lens device.

  In S304, the control unit 23 determines that the temperature difference ΔT is 5 degrees or less, that is, a predetermined threshold value TH or less, and proceeds to S105.

  In S105, the control unit 23 determines to proceed to S106 when the temperature TO of the exterior member 1 is higher than the temperature TG of the inner holding member 2b. If the temperature TO acquired as the outside air temperature is low and the conductive state is set, the heat of the lens 3 is lost and the temperature margin is reduced. In S105, the control unit 23 performs the above determination.

  In S106, the control unit 23 issues a command to the motor 21a, the shaft 22a rotates accordingly, the heat conducting unit 11 is moved to a position where it contacts the exterior member 1, and the conductive state shown in FIG. . If it is already in the conductive state, this state is maintained.

  When the heat conducting portion 11 comes into contact with the exterior member 1, heat conduction occurs from the exterior member 1 to the lens 3 through the heat conduction path indicated by the arrow 103, and the surface temperature thereof increases. Thereby, the margin of the surface temperature of the lens 3 with respect to the dew point temperature can be maintained at a predetermined value (5 degrees in this embodiment) or more, and condensation can be prevented.

  Hereinafter, the predetermined temperature margin TH is 5 degrees, the temperature TG of the inner holding member 2b is higher than the dew point temperature TC of the air inside the lens apparatus (that is, no condensation occurs), and the temperature difference ΔT is 8 degrees. In the case of, the control process of the control part 23 is illustrated.

  If the temperature difference ΔT is 5 degrees or more in S304, the control unit 23 proceeds to S107, issues a command to the motor 21a, and moves to a position where the heat conducting unit 11 does not contact the exterior member 1, FIG. Set to the non-conductive state shown in. If it is already in a non-conductive state, this state is maintained.

  In this state, since the heat conducting portion 11 does not contact the exterior member 1, the temperature of the lens 3 rises more than necessary, and the effect of preventing the optical performance such as focus shift due to the deformation of the glass is obtained. be able to.

(Modification)
If the above processing is configured to be repeatedly executed every 5 minutes, an effect can be obtained according to the state of the lens apparatus every 5 minutes. Although the processing repetition time is 5 minutes, it is not limited to this.

  In the above operation example, the predetermined threshold value TH is set to 5 degrees, but the present invention is not limited to this. The predetermined threshold value TH can be appropriately set according to the situation where the lens apparatus is used.

  The heat conducting unit 11 in the present embodiment has a convex portion, and a screw hole is formed in the convex portion. However, if the convex portion is formed as a separate member and is made of a resin member having low thermal conductivity, heat conduction loss can be reduced and heat can be more effectively transferred to the optical member.

  Moreover, the heat conduction part in this embodiment was demonstrated in the example comprised in the lens barrel 2. FIG. However, the present invention can be carried out even when attached to the exterior member 1.

  In this case, the configuration in which the heat conducting unit 11 is in contact with the exterior member 1 and the lens barrel 2 in the conductive state does not change. preferable. At the same time, for example, it is preferable that the lens barrel 2 or the exterior member 1 is configured with a sensor capable of acquiring a state in which the exterior member 1 is mounted at a predetermined position of the lens barrel 2 and a state in which the exterior member 1 is not mounted.

  When the sensor detects that the exterior member 1 is not mounted at a predetermined position, the control unit 23 controls the motor 21a so that the heat conducting means is in a non-conducting state in FIG. With this configuration, the exterior member 1 can be attached to and detached from the lens barrel 2 with the heat transfer means retracted so as not to contact the lens barrel 2.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  In the above embodiment, the lens apparatus has been described as an example. However, the present invention is also applicable to an image pickup apparatus having a camera having an image sensor and a lens barrel that connects an image of a subject to the image sensor. In this case, it is possible to provide an imaging device in which condensation does not easily occur even when used in various temperature environments. When the present invention is used for such an imaging apparatus, it is desirable to use the lens apparatus of the present embodiment as a lens barrel that connects an image of a subject to the imaging element.

DESCRIPTION OF SYMBOLS 1 Exterior member 2 Lens tube 3 Glass 11 Heat conduction part 20 Drive part 23 Control part

Claims (9)

An optical member;
An optical holding unit for holding the optical member;
An exterior member that covers the optical holding unit,
Heat conduction means capable of conducting heat outside the lens device to the optical member through the exterior member;
A controller for controlling the heat conduction means,
The control unit has a conduction state in which the heat conduction means conducts the external heat to the optical member according to a temperature outside the lens device and a temperature of the optical member, and a non-conduction state in which the heat conduction means does not conduct, The lens device characterized by switching. First acquisition means for acquiring the external temperature;
Second acquisition means for acquiring the temperature of the optical member,
When the external temperature is higher than the temperature of the optical member, the control unit sets the heat conducting means to the conducting state.
2. The lens device according to claim 1, wherein when the temperature outside the exterior member is equal to or lower than the temperature of the optical member, the heat conducting unit is switched to the non-conducting state. The second acquisition means detects the temperature of the optical holding member as the temperature of the optical member,
3. The lens device according to claim 2, wherein in the non-conductive state, the heat conducting means does not contact at least one of the exterior member and the optical holding member. The lens apparatus according to claim 3, wherein the first acquisition unit detects a temperature of the exterior member as the external temperature. The lens apparatus according to claim 1, wherein the heat conducting unit is configured between the exterior member and the optical holding member. Further comprising third acquisition means for acquiring a dew point temperature in the vicinity of the optical member;
When the temperature of the optical member is equal to or lower than the dew point temperature and the external temperature is higher than the temperature of the optical member, the control unit sets the heat conducting means to the conductive state.
6. The lens device according to claim 2, wherein when the temperature of the optical member is higher than the dew point temperature, the heat conducting unit is set in the non-conducting state. When the temperature of the optical member is higher than the dew point temperature in the lens device according to claim 6,
When the temperature difference between the dew point temperature and the temperature of the optical member is equal to or less than a predetermined threshold value, and the external temperature is higher than the temperature of the optical member, the heat conducting means is set to the conductive state,
When the temperature difference between the dew point temperature and the temperature of the optical member is less than or equal to a predetermined threshold, and the external temperature is less than or equal to the temperature of the optical member, the heat conducting means is in the non-conductive state,
7. The lens apparatus according to claim 6, wherein when the temperature difference between the dew point temperature and the temperature of the optical member is larger than a predetermined threshold value, the heat conducting means is set in the non-conducting state.   An image pickup apparatus comprising: a camera having an image pickup device; and the lens device according to claim 1, wherein an image of a subject is formed on the image pickup device of the camera by the lens device. An optical member, an optical holding unit that holds the optical member, an exterior member that covers the optical holding unit, and a drive unit, and heat from the outside of the lens device is transmitted through the exterior member to the optical member A heat conducting means capable of conducting heat, a control unit for controlling the driving unit,
A method of controlling a lens device comprising:
The controller is
Obtaining information on the temperature outside the lens device, the temperature of the optical member, and the dew point temperature of the space surrounded by the optical holding unit and the optical member;
Determining whether the temperature of the optical member is higher than the dew point temperature;
Determining whether a temperature difference between the optical member and the dew point temperature is greater than a predetermined threshold;
Determining whether the external temperature is higher than the temperature of the optical member;
Controlling the driving unit based on any of the determinations, and the step of switching the conduction state in which the heat conduction means conducts the external heat to the optical member and the non-conduction state in which the heat conduction means does not conduct. A control method for a lens device.

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