JP2017215574A - Lens controller and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens controller capable of controlling a lens out of focus due to temperature changes to a proper focus state.SOLUTION: A camera control unit 310 calculates a change amount of the temperature from temperature acquired by a temperature detection part 313. A storage part 315 stores a piece of coefficient data corresponding to a lens. The camera control unit 310 calculates correction amount on the basis of the change amount of the temperature and the coefficient stored in the storage part 315. The camera control unit 310 controls the lens drive on the basis of the correction amount.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a lens control device, and more particularly to correction of focus deviation caused by temperature. The present invention also relates to the control method.

  Conventionally, it has been known that deformation of a lens barrel caused by a temperature change is a cause of positional deviation of a focus lens of a camera.

  In Patent Document 1, a correction value of a position corresponding to the infinity of the focus lens is obtained based on temperature, zoom ratio, and temperature correction data of the focus lens position with respect to the zoom ratio. Then, the driving of the focus lens is controlled based on the correction value and the position corresponding to the infinity of the focus lens. Thereby, it is possible to correct the position shift of the focus lens due to the temperature change.

JP 2003-232986 A

  However, Patent Document 1 has various problems.

  For example, in Patent Document 1, it is considered that the method of shifting the position of the focus lens may differ depending on whether the member expands or contracts depending on whether the temperature has risen or reached a certain temperature. Therefore, it has the following problems.

  That is, even when the temperature is the same, for example, when the temperature is changed from 0 ° C. to 25 ° C. and when the temperature is changed from 50 ° C. to 25 ° C., even when the focus shift due to the shift of the focus lens position can be corrected, it cannot be corrected. There was also.

  Further, for example, even if a certain lens can accurately correct the position shift of the focus lens, another lens may not be able to correct the position shift of the focus lens. This is because it is not taken into account that the way of shifting the position of the focus lens may differ depending on how the member expands and contracts depending on the lens.

  Accordingly, an object of the present invention is to provide a lens control device capable of performing lens control so as to correct a focus shift caused by a temperature change to a focus state closer to the original. Moreover, it aims at providing the control method.

The present invention provides a lens control device in which a lens can be attached and detached, a temperature detection unit that detects a temperature, a first calculation unit that calculates a change in temperature from a plurality of temperatures detected by the temperature detection unit, and a lens Storage means for storing coefficient data corresponding to the second calculation means, second calculation means for calculating a correction amount based on the calculation result by the first calculation means and the coefficient stored in the storage means, and the correction amount And a lens control means for controlling lens driving based on the above.

  According to the present invention, it is possible to perform lens control so that a focus shift caused by a temperature change is corrected to a focus state closer to the original.

Schematic diagram of lens barrel Configuration example of imaging device Focus Correction Processing Flow in Embodiment 1 Processing flow for selecting a focus correction parameter (correction coefficient K) in the second embodiment Processing flow for selecting a focus correction parameter (correction coefficient K) in the third embodiment High temperature processing determination processing flow in Example 4 The figure explaining the subject of Example 1 Focus Correction Processing Flow in Embodiment 5 The figure which showed the relationship between the temperature variation of the camera main body side in Example 6, and the change of a focus position. Focus Correction Processing Flow in Embodiment 6 Focus correction processing flow in Modification 1 of Embodiment 6 Focus Correction Processing Flow in Modification 2 of Embodiment 6 Focus Correction Processing Flow in Embodiment 7 Focus Correction Processing Flow in Embodiment 8

[Example 1]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 2 shows a configuration example of a basic image pickup apparatus according to an embodiment of the present invention. In the first embodiment, an imaging apparatus in which a lens is integrated will be described as an example. However, the lens may be configured to be detachable from the imaging apparatus. In addition, the present embodiment is an embodiment assuming a surveillance camera, but the present embodiment can be applied to cameras other than the surveillance camera.

  In FIG. 2, a lens group 301 is an optical system that condenses light incident from a subject on an image sensor 305.

  The lens group 301 includes a focus lens that focuses on a subject, a zoom lens that adjusts an angle of view, and the like.

  Light entering the camera through the lens group 301 passes through the optical filter 302. The amount of light incident on the image sensor 305 is adjusted by the diaphragm 303.

  As the optical filter 302, for example, an infrared cut filter (IRCF) or the like is installed.

  The image information whose light amount has been adjusted passes through the color filters 304 arranged in a predetermined order for each pixel on the light receiving surface of the image sensor 305 and is received by the image sensor 305.

  The image sensor 305 outputs captured image information to be captured as an analog signal.

  The image formed by the image sensor 305 is gain-controlled by the AGC 306 and the luminance of the image signal is adjusted, and the analog image signal is converted into a digital signal by the A / D converter 307.

  The video signal processing unit 308 performs predetermined processing on the digital image pickup signal from the A / D conversion unit 307 and outputs a luminance signal and a color signal for each pixel, and creates an output video and controls the camera. Each parameter to do is created.

  Parameters used for camera control include those used for exposure control such as an aperture, focus control, and white balance control for adjusting color.

  The video signal output unit 309 outputs the video signal C created by the video signal processing unit 308 to an external device (not shown) via a network (not shown).

  The camera control unit 310 controls the camera based on the camera control parameters obtained from the video signal processing unit 308. The camera is controlled based on a camera control signal D input from an external device (not shown) via a network (not shown).

  The camera control unit 310 includes an exposure control unit 311 (not shown), an optical control unit 312 (not shown), and a storage unit 314. The storage unit 314 stores correction parameters described later. The storage unit 314 can store a temperature detected by a temperature detection unit 313 described later.

  The exposure control unit 311 calculates luminance information in the shooting screen from the luminance signal output from the video signal processing unit 308, and controls the diaphragm 303 and the AGC 306 to adjust the shot image to a desired brightness.

  Furthermore, the camera control unit 310 can also adjust the brightness by adjusting the accumulation time of the image sensor 305 by adjusting the shutter speed.

  As the focusing operation, a high frequency component is extracted from the video signal created by the video signal processing unit 308, and the value of the high frequency component is used as focus focus information (AF evaluation value). That is, in the first embodiment, focus detection is performed using a so-called contrast detection method. However, phase detection may be used for focus detection.

  Then, the focus lens position is set by the camera control unit 310 so that the AF evaluation value is maximized, and the optical control unit 312 controls the lens group 301.

  The temperature detection unit 313 is a sensor that detects the temperature of the camera, and transmits the temperature data to the camera control unit 310. There may be a plurality of sensors for detecting the temperature of the camera. For example, sensors may be arranged in the vicinity of the tip of the lens barrel and in the vicinity of the image sensor 305, respectively. In this case, an appropriate temperature may be calculated based on the temperatures detected from both sensors, or one of them may be selected.

  Then, based on the temperature data, the camera controller 310 calculates a correction amount for shifting the focus position due to the temperature, and performs focus correction.

  Since the imaging apparatus in which the lens is integrated is assumed in the first embodiment, a correction amount described later may be acquired from the storage unit 315 that is a nonvolatile memory to calculate a correction amount.

  Here, FIG. 1 shows a specific example of processing when the focus correction amount changes due to the temperature change tendency.

  FIG. 1 shows a schematic diagram of a general lens barrel.

  A lens barrel 101 in the figure has a lens 102.

  The lens 102 is configured to be moved back and forth in the optical axis direction by the power of the lens driving motor 104 held by the slide bar 103 by engaging the screw 105 and the rack 106.

[Explanation of assumed issues]
The biting between the screw 105 and the rack 106 has a mechanical tolerance. The tolerance causes a shift in the focus lens position as a mechanical backlash, and affects the focus control of the camera.

  This will be described in more detail with reference to FIG. For example, after the focus lens (not shown) is moved to perform focusing, the bite between the screw 105 and the rack 106 is shifted to the driving direction of the screw 105 as shown in FIG. Become.

  A case where there is a temperature change in this state is shown in FIGS.

  For example, when there is a temperature change from a certain temperature to a high temperature, the screw 105 and the rack 106 expand as shown in (c), and the position of the lens attached to the rack 106 also varies. .

  Furthermore, as shown in (c), the screw 105 and the rack 106 of the fitting portion interfere with each other due to expansion due to heat, and push out, so that the focus position is further shifted.

  On the other hand, as shown in FIG. 7B, when there is a temperature change from a certain temperature to a low temperature, the member contracts. As a result, the position of the focus lens attached to the rack 106 also varies.

  However, in the case of (b), since the member of the fitting portion contracts, the members do not interfere with each other and are not pushed out by the members. As a result, the focus position shifts by the amount of contraction due to heat.

  As described above, the defocus due to the temperature change depends on whether the member has expanded from a certain temperature to a current temperature and then reaches the current temperature, or whether the member has contracted from a certain temperature to a low temperature and then has reached the current temperature. Different.

  On the other hand, in the related art, although correction according to the absolute temperature at a certain timing is performed, the temperature before the timing is not considered. For this reason, it has been impossible to correct focus deviation considering both whether the temperature was higher or lower before reaching a certain temperature.

  As described above, in the focus correction method that performs only unique correction according to the absolute temperature at a certain timing, the lens control is performed so that the focus shift caused by the temperature change is corrected to a focus state closer to the original. There was a case that could not be done.

[Focus correction (flow)]
Hereinafter, the focus correction in the first embodiment will be described with reference to FIG. FIG. 3 is a processing flow for performing focus correction according to whether the temperature before a temperature at a certain timing is high or low as described with reference to FIG.

  First, the lens is driven to focus on the subject to be photographed (S401).

  Next, the temperature detection unit 313 (temperature detection means) detects the temperature of the camera (S402).

  Subsequently, the camera control unit 310 (determination unit) determines the tendency of temperature change using the temperature detected in S402 (S403). In the present embodiment, the tendency of temperature change is a tendency of how the temperature has changed up to the current temperature. For example, when the current temperature is reached due to an increase in temperature, the camera control unit 310 determines that the temperature change tends to increase.

  As a method for detecting the tendency of temperature change, for example, the current temperature may be compared with the past temperature, and if the current temperature is higher, it may be determined that the temperature tends to increase. In this case, the past temperature to be compared with the current temperature is the temperature detected in S402 a predetermined number of times before or the temperature detected a predetermined time ago.

  Further, the continuity of temperature rise / fall may be determined, and the one having continuity may be determined as the tendency of temperature change.

  In addition, the camera control unit 310 (detection means) detects whether the temperature has increased or decreased during each temperature detection time in a certain period (also referred to as a first period), and the larger of the temperature increase / decrease You may determine the tendency of a temperature change based on a detection result. For example, when the detection result that the temperature has risen is greater than the detection result that the temperature has fallen, the camera control unit 310 determines that the temperature change tends to increase. Further, when the detection result indicating the decrease is greater than the detection result indicating the increase, the camera control unit 310 determines that the temperature change tends to decrease. At this time, the said period is the detection time which detected the present temperature from the detection time which detected the temperature in the past. In this period, the temperature is detected at a plurality of different times.

  Alternatively, a linear expression may be calculated using the current temperature and a plurality of temperatures detected in the past and detection time, and it may be determined whether the temperature tends to increase or decrease based on the inclination.

  On the other hand, when S402 is the first time, for example, the temperature at the time of power activation may be referred to and compared with the current temperature detected in S402.

  If the camera control unit 310 determines in S403 that the temperature change tends to increase, the camera control unit 310 calculates a focus correction amount C for temperature increase (S405).

  On the other hand, when the camera control unit 310 determines in S403 that the temperature change tends to decrease, the camera control unit 310 (acquisition means) calculates a focus correction amount C for decreasing the temperature ( S404).

The focus correction amount C can be calculated by, for example, the following conversion formula.
Focus correction amount C = (ΔT × K) / ppm

  In the above conversion equation, ΔT is a temperature change amount, and K is a correction coefficient, which is switched when the temperature rises and when the temperature falls. Here, ppm indicates a change amount per pulse as a lens driving amount assuming a pulse motor. In the first embodiment, the focus correction amount C is obtained as a pulse that is a unit of lens driving in the first embodiment. However, the present invention is not limited to this.

  When it is assumed that the temperature change amount ΔT is the same, the correction coefficient K is different between S404 and S405.

  Here, the correction coefficient K may be changed for each temperature range by setting a threshold value. For example, with a threshold value of 25 ° C., the correction coefficient K differs between 26 ° C. and 55 ° C. and −4 ° C. to 25 ° C. even if the temperature change is the same 29 ° C.

  Further, the sign of the correction coefficient K may be different between when the temperature rises and when the temperature falls.

  Further, as shown in FIG. 7, since the interference direction of the screw 105 and the rack 106 varies depending on the lens driving direction, the correction coefficient K may be changed in consideration of the lens driving direction. For example, in FIG. 7, the screw 105 and the rack 106 are in contact with each other on the right side when viewed from the screw 105, and there is a backlash on the left side. In this case, as shown in (c), the screw 105 and the rack 106 expand at high temperatures, and as a result, the rack 106 is pushed rightward by the screw 105. Therefore, the focus correction is performed in the left direction.

  On the other hand, when the screw 105 and the rack 106 are in contact with each other on the left side when viewed from the screw 105, there is a play on the right side (not shown). And if the screw 105 and the rack 106 expand | swell at high temperature mutually, the rack 106 will be extruded by the screw 105 to the left direction as a result. Therefore, the focus correction is performed in the right direction.

  As described above, the direction in which the screw 105 and the rack 106 are shifted to the right side or the left side changes, so that the correction direction may be changed in S404 and S405. For example, the sign of the correction coefficient K is positive or negative. Make them different.

  Then, the camera control unit 310 (lens control means) controls lens driving so that the focus correction amount C based on the temperature change tendency determined in S404 and S405 is shifted with respect to the focus position performed in focusing (S401). Thereby, the focus shift caused by the temperature change is corrected (S406).

  After S406, the process returns to S402, and S402 to S406 are repeated. By always detecting the temperature and repeating the focus correction, it is possible to appropriately correct the focus shift due to the temperature.

[Modification]
Note that in the case of a camera configured so that focus correction cannot be performed, in the case of a so-called single focus camera, focus drive cannot be performed, and thus the focus position equivalent to the correction amount cannot be shifted.

  In such a case, the focus shift due to the temperature change is corrected by the diaphragm operation. Specifically, how much the aperture should be reduced is calculated from the calculated focus correction amount also in the flowchart, and the focus is corrected using the aperture change amount as the focus correction amount.

  The reason why the focus can be corrected by the aperture is as follows. Conventionally, it has been known that the range in which the focus can be seen is expanded by reducing the aperture, that is, the depth becomes deeper. By increasing the depth, blurring of the focus can be eliminated.

  For this reason, even when the focus does not move by controlling the aperture, correction is possible.

[Effect of Example 1]
As described above, in the first embodiment, a different focus correction amount C is calculated depending on whether or not the temperature change tendency is a temperature increase tendency, and the focus correction is performed using the calculated focus correction amount. .

  By performing the above processing, lens control is performed so that the focus shift caused by the temperature change is corrected to a closer focus state even when the focus shift differs depending on the temperature change tendency. be able to.

[Example 2]
The first embodiment has been described assuming a camera that is not a lens interchangeable type. On the other hand, in the second embodiment, focus correction in a camera system in which an optical member including the lens group 301 can be attached and detached will be described. Examples of optical members that can be changed include an optical filter such as an ND filter and an IR cut filter, a dome used in a surveillance camera, and the like in addition to the lens group 301. Here, as a specific example, the lens group 301 will be described as an optical member that can be changed.

  In addition, description is abbreviate | omitted about a common part with Example 1, and it pays attention to a different point, and demonstrates.

[Problems assumed in Embodiment 2]
In the first embodiment, it has been described that the member expands or contracts depending on the tendency of temperature change, and different focus shift occurs. However, since the degree of expansion and contraction of the member may not be uniform due to differences in the material and configuration of the optical member, the amount of defocus due to temperature may vary. Therefore, it is necessary to calculate an appropriate correction amount according to characteristics such as the material and configuration of the optical member to be replaced.

  Therefore, in the second embodiment, it is detected that a lens is attached, and the camera acquires lens data. Then, a focus correction amount C is calculated using the lens data.

[Parameter selection]
FIG. 4 shows a process flow for selecting a focus correction parameter (correction coefficient K) in an interchangeable lens type camera system.

  After this flow, by performing the flow of FIG. 3 described in the first embodiment, the lens control can be performed so as to correct the focus shift caused by the temperature change to a focus state closer to the original.

  First, the optical control unit 312 detects that a lens has been attached (S501). And the memory | storage part 314 acquires the lens data output from the lens. As the lens data described here, unique information that can identify the lens, a correction coefficient suitable for the mounted lens, and the like can be considered.

  Then, the camera control unit 310 determines whether lens data has been acquired (S502).

  If the lens data can be acquired, the camera control unit 310 determines a correction parameter based on the lens data (S503). If the lens data is lens identification information, it may be used by referring to the correction amount based on the identification information. Further, when a correction coefficient suitable for the lens can be acquired as lens data, the correction coefficient is used.

  The correction parameters used at this time may be provided on the interchangeable lens side, or may be provided on the camera body side or an external control device such as a PC that performs camera operation.

  In addition, when sending lens specific information, it is possible to search for correction information applicable to the specific information via the network so that multiple types of correction data can always be used without being held in the camera body. Become.

  When lens data can be acquired by such a method, correction is performed based on the lens data.

  On the other hand, if the lens data cannot be acquired, a correction stop parameter is determined as a correction parameter so as not to perform correction (504). For example, the correction coefficient K = 0. The reason is as follows. When lens data cannot be acquired, it is not known in what case and how much correction should be performed. If correction is performed in such a case, there is a concern that blurring may occur. In addition, there may be a case where the attached lens is a lens that does not consider the focus position correction depending on the temperature. Even in such a case, if the correction is performed, the focus may not be achieved. From the above, in Example 2, correction is not performed when lens data cannot be acquired.

[Effect of Example 2]
In the second embodiment, when the optical member is attached, if the optical member data cannot be acquired, the correction is not performed. By doing so, it is possible to prevent the focus shift from becoming larger by performing the correction. Moreover, when the data of an optical member can be acquired, it correct | amends based on this. As a result, even when the focus shift is different depending on the tendency of the temperature change, the lens control can be performed so as to correct the focus shift caused by the temperature change to a focus state closer to the original.

[Example 3]
Further, FIG. 5 shows a flow when the focus correction by the control of the aperture is further considered in addition to the flow of FIG.

  In the flow of FIG. 5 as well, the flow of FIG. 3 is performed after the flow processing is completed, so that the focus shift caused by the temperature change is corrected to a focus state closer to the original. Lens control can be performed.

  A description of portions common to the second embodiment will be omitted, and the description will be given here while paying attention to different points.

  First, the optical control unit 312 detects that the lens has been attached (S601). At this time, if the lens data can be acquired, the lens data is acquired.

  Next, the camera control unit 310 determines whether lens data has been acquired (S602).

  When the lens data is acquired, the camera control unit 310 determines whether or not focus control is possible (S603).

  If it is determined that focus control is possible, the camera control unit 310 determines a correction parameter (S604), and ends the flow.

  On the other hand, when the lens data can be acquired but the focus control cannot be performed, the camera control unit 310 determines whether or not the aperture can be controlled (S605).

  If the camera control unit 310 determines that the aperture is controllable, the aperture value is changed to a depth corresponding to the correction amount, and the flow of FIG. 5 ends (S606).

  If the camera control unit 310 determines that aperture control cannot be performed in S605, the camera control unit 310 sets parameters for preventing correction (S607). For example, as illustrated in the second embodiment, K = 0.

  Up to this point, the processing when the camera control unit 310 determines that the lens data has been acquired in S602 has been described.

  On the other hand, if it is determined in S602 that the lens data could not be acquired, as in the description in the second embodiment, if the focus is moved and correction is performed without knowing the correction amount by the lens, the correction is not performed correctly. There may be a case where the focus shift becomes large.

  Therefore, in this embodiment, if it is determined in step S608 that aperture control is possible, focus control is performed instead of focus control, but the aperture is reduced to a predetermined aperture value, and focus correction is performed. (S609).

  If the camera control unit 310 determines that aperture control is also impossible in S608, a correction parameter is set so as not to perform correction (S607).

  In addition, although examples of performing focus correction by reducing the aperture so far have been shown, especially when the correct correction amount is unknown, the amount of focus shift is proportional to the temperature change, so the amount of change in temperature is large. It is desirable to reduce the aperture as time passes.

[Effect of Example 3]
In the third embodiment, in addition to the flow of the second embodiment, in consideration of whether or not aperture control is possible, if it is better not to perform correction, focus correction is performed by reducing the aperture.

  In this way, even an interchangeable lens for which lens data cannot be obtained can be corrected. In addition, even a camera that cannot perform focus control can perform focus shift correction by the aperture, and thus it is possible to perform focus shift correction corresponding to a wider range of lenses than in the second embodiment.

[Example 4]
So far, it has been explained that the lens control can be performed so as to correct the focus shift caused by the temperature change to the focus state closer to the original by performing the correction according to the optical member while taking the tendency of the temperature change into consideration. did.

  In the fourth embodiment, a system in which a camera body or an optical member has experienced up to what temperature environment is stored as a history, and a correction coefficient is changed according to a temperature experienced in the past will be described.

  The reason for changing the correction process according to the temperature history is as follows. If it has been exposed to a high temperature environment above the specified temperature, it removes the internal distortion that occurs in the process of cooling the resin during the molding of the lens barrel, etc. by heating, similar to the so-called annealing treatment. The processing has been performed and the distortion is removed. For this reason, the amount of focus shift varies depending on the temperature depending on whether or not there has been exposure to a high temperature environment of a predetermined temperature or higher (hereinafter also referred to as high temperature processing).

[High-temperature treatment judgment]
FIG. 6 is a flowchart of high-temperature processing determination according to the fourth embodiment.

  In addition, here, description is abbreviate | omitted about the part which is common in the Example so far, and it demonstrates paying attention to a difference here.

  First, the camera control unit 310 determines whether a high temperature process has been performed (S701). Whether or not the high temperature processing has been performed can be determined by storing the maximum temperature among the temperatures detected by the temperature detection unit 313 in the past. The determination can also be made by memorizing that the environment has reached a predetermined temperature or higher.

  When the camera control unit 310 determines that the high temperature processing has been performed, a correction parameter for the case where the high temperature processing has been completed is determined (S702). When the camera control unit 310 determines that the high temperature processing has not been performed, the correction stop parameter when the high temperature has not been processed is determined. The correction stop parameter is a parameter used for controlling not to perform correction.

  Furthermore, it is better to determine how long the high temperature state has been maintained (high temperature processing time). For example, the focus correction amount is made different between a case where a predetermined time or more has passed since the temperature has become higher than a predetermined temperature and a case where the temperature is less than the predetermined time. Specifically, when the high temperature state is maintained for a predetermined time or longer, the correction coefficient is made smaller than when the high temperature state is shorter than the predetermined time.

  In addition, as described above, when the high temperature is experienced, internal distortion generated in the process of cooling the resin or the like during molding of the lens barrel or the like can be removed by heating. It is desirable to make it smaller.

[Effect of Example 4]
In the fourth embodiment, when the high temperature processing is performed, the focus correction amount is made different from that when the high temperature processing is not performed. This is because the displacement of the member is removed when the high temperature treatment is performed. By doing so, in the fourth embodiment, it is possible to prevent excessive focus correction.

[Example 5]
In the second embodiment, the example in which the focus correction is performed using the focus correction parameter (correction coefficient K) suitable for each lens in the camera system in which the optical member including the lens group 301 is detachable has been described. In this connection, the present embodiment further illustrates how to hold data of a focus correction parameter (correction coefficient K) suitable for each lens.

[Problem to be solved in Example 5]
In the above-described embodiment, it has been described that the correction coefficient K is varied depending on, for example, whether the temperature tends to increase or decrease. However, until now, the influence due to the difference in the temperature change amount ΔT per unit time has not been considered.

  The tendency of the expansion and contraction of the member of the lens barrel may differ depending on whether the temperature change amount ΔT per unit time is large or small, that is, when the temperature difference is large or small. For example, if the temperature change amount ΔT is the first temperature difference even if the same member is used when the temperature rises, the temperature change amount ΔT is a second temperature difference larger than the first temperature difference. Compared with, the temperature may change more slowly.

  In particular, in the case of a lens barrel composed of a plurality of members, since the change for each member is integrated, the tendency of the lens barrel to expand or contract may be easily changed depending on the temperature difference.

  For this reason, depending on the timing of expansion / contraction of multiple members due to temperature change, even if the same temperature change results, the set of constituent members such as those that easily follow the temperature change and those that do not. The situation changes.

  For example, when there is a correction coefficient corresponding to a temperature difference of 5 ° C. and there is a temperature change from 20 ° C. to 30 ° C., the focus correction amount calculated using a value obtained by simply doubling the correction coefficient is Even if it is used, the focus shift may not always be corrected.

[Focus Correction of Example 5 (Flow)]
In this embodiment, therefore, a method of correcting a focus deviation by selecting a correction coefficient corresponding to the detected temperature difference having a plurality of correction coefficients considering the magnitude of the temperature difference per unit time is described. I do.

  In this embodiment, as an example, the correction coefficient K2 when the first temperature difference (for example, 10 ° C.) changes per unit time (for example, 1 hour) and the second temperature difference (the temperature greater than the first temperature) For example, the storage unit 314 stores a correction table having a correction coefficient K3 when changed. In the present embodiment, a correction coefficient is set using at least one of the correction coefficients K2 and K3 according to the degree of the temperature difference per hour, and the focus shift is corrected using the correction coefficient.

  The correction table may be stored in advance in the storage unit 314, or may be acquired from a detachable lens unit.

  A specific example will be described with reference to the flow of FIG. First, the temperature detection unit 313 detects the current temperature (S801).

  Next, the camera control unit 310 detects the temperature difference between the temperature information acquired before the latest S801 (in this embodiment, the temperature when the previous temperature was detected as an example) and the temperature detected in S801 (S802). . Here, the case where the absolute value of a temperature difference is detected is illustrated.

Here, the camera control unit 310 determines whether or not the temperature difference detected in S802 is greater than or equal to the first temperature difference (greater than or equal to the first change amount) (S803). If it is determined that the difference is equal to or greater than the first temperature difference, the camera control unit 310 calculates a focus correction amount using the correction coefficient K2 (S804). The calculation method for calculating the focus correction amount is exemplified by the same method as in the above-described embodiment.
Focus correction amount C = (ΔT × K) / ppm

  When the temperature difference is less than the first temperature difference (less than the first change amount), the camera control unit determines whether or not the temperature difference is greater than the second temperature difference (greater than the second change amount). 310 determines (S805). When the difference is larger than the second temperature difference, the camera control unit 310 calculates the focus correction amount using the correction coefficient K2 corresponding to the first temperature difference and the correction coefficient K3 corresponding to the second temperature difference (S806). ). In this case, the focus correction amount may be calculated after calculating a more appropriate correction coefficient by performing an interpolation process using the correction coefficient K2 and the correction coefficient K3 in accordance with the temperature difference detected in S801. . For example, when the first temperature difference is 5 ° C. and the second temperature difference is 10 ° C., and the detected temperature change is 7.5 ° C., the correction coefficient K2 is corrected. The camera control unit 310 may calculate an intermediate value of the coefficient K3 and set it as a correction coefficient.

  When the temperature difference is equal to or less than the second temperature difference (less than the second change amount), the camera control unit 310 calculates the focus correction amount using the correction coefficient K3.

  Then, based on the focus correction amount calculated in S804, S806, and S807, the camera control unit 310 controls to perform the focus correction.

  After executing S808, the process returns to S801 to repeat this flow. By always detecting the temperature and repeating the focus correction, it is possible to appropriately correct the focus shift due to the temperature.

  In this embodiment, for simplification of explanation, the case where the correction coefficient corresponding to the first temperature difference and the second temperature difference is illustrated, but it corresponds to each of three or more types of temperature differences. May have a correction value.

  In the present embodiment, the example in which the absolute value of the temperature difference is detected has been described, but +-may be detected. That is, it may be detected whether the temperature has decreased or increased. In that case, the storage unit 314 may store a table having correction coefficients when the temperature is lowered and when the temperature is raised as the correction table for the correction coefficient K2 and the correction coefficient K3.

  Note that the correction coefficient may be set so that the correction amount per temperature difference is larger when the correction coefficient K2 is used than when the correction coefficient K2 is used. This is because when the temperature difference is large, it is considered that the degree of defocus is likely to be larger than when the temperature difference is smaller.

[Effect of Example 5]
In the fifth embodiment, the case where the focus correction is performed using the correction coefficient considering the degree of the temperature difference is illustrated. As a result, even when the degree of defocus differs depending on the degree of temperature difference, the defocus correction can be performed with higher accuracy.

[Example 6]
In the second embodiment, the example in which the focus correction is performed using the focus correction parameter (correction coefficient K) suitable for each lens in the camera system in which the optical member including the lens group 301 is detachable has been described. In this connection, in this embodiment, an example in which focus correction is performed in consideration of a time lag until the temperature detected by the temperature sensor is transmitted to the lens will be described.

[Problem to be solved in Example 6]
There are two main causes of temperature changes that change the focus position: temperature changes in the installation environment and heat generation by the imaging apparatus itself.

  As the temperature change due to the installation environment, for example, a temperature change due to morning and evening or a temperature change due to air conditioning can be considered. Further, as a heat source in the imaging apparatus, for example, a power supply circuit, a video engine that performs image processing, and the like are conceivable. The timing at which the temperature change is transmitted to the lens barrel differs depending on the distance from the heat source and how the heat source is connected.

  When the heat source is in the main body of the imaging device, a delay in temperature change occurs when the lens barrel attached to the imaging device is long or when the thermal conductivity of the member employed in the lens barrel is low. There is a case.

  For example, when a temperature sensor is attached to the camera body, the temperature sensor updates and acquires the temperature detected according to the heat generated by the camera body.

  However, if the total length of the interchangeable lens is long or the thermal conductivity is poor, the entire lens barrel of the interchangeable lens will be at the temperature calculated by the sensor on the camera body side, and it will take some time to reach the steady state. There is.

  FIG. 9 is a graph showing the relationship between the temperature change amount and the focus position change.

  In region 1, the temperature detected by the temperature sensor is also rising (dotted line), and a change in focus position (solid line) is also generated accordingly. In region 2, the temperature of the heat source is in a stable and steady state, and the temperature change detected by the temperature sensor is constant. However, since the temperature is not transmitted to the lens side, further defocusing occurs. In region 3, heat is transmitted to the lens side, and the change of the focus position is stopped.

  As described above, there may be a time lag until the temperature detected by the temperature sensor is transmitted to the lens. Therefore, it may not be possible to accurately correct the focus deviation simply by correcting the focus based on the temperature change. It was. For example, when the focus shift is corrected based on the temperature change ΔT from the time T1 at the time T2 without considering the time lag of heat transfer occurring in the regions 1 and 2 in FIG. 9, the focus at the time T4 is corrected. It is also possible that the image is corrected to the position and is out of focus at time T2.

[Focus Correction of Example 6 (Flow)]
In view of the above, in this embodiment, focus deviation correction is performed in consideration of a time lag (heat transfer delay) from when the temperature detected by the temperature sensor rises until the temperature is transmitted to the lens barrel.

  In this embodiment, as an example, the storage unit 314 stores the correction table having the correction coefficient K4 that is the correction coefficient of the first region in FIG. 9 and the correction coefficient K5 that is the correction coefficient of the second region in FIG. doing. In the present embodiment, the correction coefficient is selected in consideration of the heat transfer delay, and the focus correction is performed.

  The correction table may be stored in advance in the storage unit 314, or may be acquired from a detachable lens unit.

  A specific example will be described with reference to the flowchart of FIG. First, the temperature detection unit 313 detects the current temperature (S1001).

  Next, the camera control unit 310 compares the temperature information acquired before the latest S1001 (S1002). In this embodiment, the temperature difference between the temperature detected this time and the temperature detected last time is calculated.

  Then, based on the temperature difference acquired in S1002, the camera control unit 310 determines whether or not there has been a temperature change (S1003).

As a result of the determination in S1003, if it is determined that there has been a temperature change, the focus correction amount corresponding to the temperature change amount T calculated in S1002 is used as the region 1 in FIG. 9 using the correction coefficient K4. The camera control unit 310 calculates (S1004). The calculation method for calculating the focus correction amount is exemplified by the same method as in the above-described embodiment.
Focus correction amount C = (ΔT × K) / ppm

  On the other hand, if it is determined in S1003 that there is no temperature change, the time that has elapsed since the time when the focus correction was last performed in S1008 is further determined to determine whether it corresponds to region 2 or region 3 in FIG. The camera control unit 310 determines whether or not it is 1 time or more (S1005). In this embodiment, the first time is the time T4 in FIG.

  When it is determined that the first time or more has elapsed, it is considered that the temperature of the detected heat source is stabilized by the temperature sensor and the focus position is also stable (corresponding to region 3 in FIG. 9). . Therefore, the camera control unit 310 further determines whether or not the focus correction of the temperature difference changed from the previous S1007 (described later) has already been performed (S1006). If S1007 has not been executed in the past, it is determined whether or not the correction of S1007 has already been performed after it is determined in S1003 that there is a temperature difference.

  When the focus correction of the temperature difference changed from the previous S1007 has already been performed, the focus position change is also stable (the shift to the third region in FIG. 9) and the focus correction is not performed.

  When the focus correction of the temperature difference changed from the previous S1007 has not been performed, the camera control unit 310 uses the correction coefficient K5 to correct the change in the focus position corresponding to the second region in FIG. A focus correction amount is calculated (S1007). Here, the camera control unit 310 calculates the focus correction amount corresponding to the temperature change between the temperature detected in S1001 immediately before the focus correction in the previous S1007 and the temperature detected in the latest S1001. If S1007 has not been executed in the past, the camera control unit 310 calculates the focus correction amount based on the temperature difference between the temperature detected in S1001 for the first time and the temperature detected in the latest S1001.

  In S1005, if it is determined that the time elapsed from the time when the focus correction was performed in S1008 last time has not passed the first time or more, the heat source temperature has stabilized, but the heat has been transmitted to the lens barrel. (Corresponding to region 2 in FIG. 9), and no correction is performed.

  After executing S1004 or S1007, focus correction is performed in S1008. Then, the process returns to S1001, and this flow is repeated. By always detecting the temperature and repeating the focus correction, it is possible to appropriately correct the focus shift due to the temperature. In the present embodiment, the temperature difference acquired in S902 is compared with a predetermined temperature (third temperature in the present embodiment), and if it is equal to or higher than the third temperature, it is determined that there has been a temperature change.

  In the present embodiment, the example in which the absolute value of the temperature difference is detected has been described, but +-may be detected. That is, it may be detected whether the temperature has decreased or increased. In that case, the storage unit 314 may store two types of correction tables for the correction coefficient K2 and the correction coefficient K3 described above, that is, when the temperature decreases and when the temperature increases.

[Effects of Example 6]
In the sixth embodiment, correction is performed using a correction coefficient that takes into account the time lag until the temperature detected by the temperature sensor is transmitted to the lens barrel. Thereby, even if there is a time lag from when the temperature of the installation environment rises to when the temperature is transmitted to the lens barrel, it is possible to perform focus deviation correction with higher accuracy.

[Modification 1 of Example 6]
Note that the change in the focus position in the region 2 does not always change with a constant inclination as illustrated in FIG. Therefore, a plurality of time thresholds may be provided corresponding to the region 2, and a plurality of correction coefficients K5 may be provided so as to correspond to the elapsed time.

  A specific example is shown in FIG. FIG. 11 differs from FIG. 10 mainly in having S1108 to S1110. Description will be made focusing on differences from FIG.

  If it is determined in S1103 that there is a temperature change, the camera control unit 310 determines whether the time elapsed from the time when the focus correction was performed in the previous S1111 is equal to or longer than the first time (S1105). The case where it is determined that the first time or more has passed is the same as in FIG.

  When it is determined that the first time or more has not elapsed, the camera control unit 310 determines whether or not the time elapsed from the time when the focus correction was performed in the previous S1111 is equal to or longer than the second time ( S1108). In this embodiment, the second time is a time corresponding to time T3 in FIG. If the time elapsed from the time when the focus correction was performed in the previous S1111 is equal to or longer than the second time, it is determined that the time T3 of the area 2 has elapsed, and the process proceeds to S1109.

  In S1109, the camera control unit 310 determines whether or not the focus correction of the temperature difference changed from the previous S1110 has already been performed. If S1110 has not been executed in the past, it is determined whether or not the correction of S1110 has already been performed after it is determined in S1103 that there is a temperature difference (S1109). That is, the camera control unit 310 determines whether correction corresponding to the focus shift from time T2 to time T3 in FIG. 9 has been performed.

  When the focus correction of the temperature difference changed from the previous S1110 has not been performed, the camera control unit 310 calculates the focus correction amount using the correction coefficient K5 (S1110). Here, the camera control unit 310 calculates the focus correction amount corresponding to the temperature change between the temperature detected in S1101 immediately before the focus correction in the previous S1110 and the temperature detected in the latest S1101. If S1110 has not been executed in the past, the camera control unit 310 calculates the focus correction amount based on the temperature difference between the temperature detected in S1101 for the first time and the temperature detected in the latest S1101.

  If it is determined in S1108 that the time elapsed from the time when the focus correction was performed in S1111 last time has not elapsed for the first time or more, the time T3 in FIG. .

  In this way, a plurality of time thresholds are provided corresponding to the region 2 and focus correction is performed using a correction coefficient corresponding to the elapsed time. Thereby, even if the change in the focus position in the region 2 is not uniform, the focus shift can be corrected more accurately.

[Modification 2 of Embodiment 6]
Note that the second area may be repeatedly corrected using the same correction coefficient within a certain predetermined time.

  A specific example is shown in FIG. FIG. 12 differs from FIG. 10 mainly in having S1206 to S1208. Further, the correction coefficient K5 corresponding to the region 2 has a correction coefficient smaller than the correction coefficient K5 in the sixth embodiment and the first modification of the sixth embodiment, and the correction value K5 is used until the first time elapses. Repeated focus correction.

  Description will be made focusing on differences from FIG.

  If it is determined in S1205 that the first time or more has not elapsed, the focus correction is performed as a change in the focus position (corresponding to the second region in FIG. 9) after the temperature has reached a stable steady state. The camera control unit 310 controls to shift to S1206 to perform the above.

  Subsequently, the camera control unit 310 calculates a focus correction amount using the correction coefficient K5 (S1206). Here, the camera control unit 310 calculates the focus correction amount corresponding to the temperature change between the temperature detected in S1201 immediately before the focus correction amount calculation in the previous S1206 and the temperature detected in the latest S1201. If S1206 has not been executed in the past, the camera control unit 310 calculates the focus correction amount based on the temperature difference between the temperature detected in S1201 for the first time and the temperature detected in the latest S1201.

  Then, the camera control unit 310 controls to perform focus correction using the focus correction amount calculated in S1206 (S1207).

  After the focus correction in S1207, the camera control unit 310 determines whether or not the first time has elapsed (S1208). If the first time has not elapsed, the process returns to S1207, and the correction in S1207 is repeated until the first time has elapsed. If the first time has elapsed, the process returns to S1201.

  As described above, it is possible to perform focus correction that accurately follows the change in the focus position by repeatedly correcting the second area in small increments using the same correction coefficient within a certain predetermined time.

[Example 7]
In the present embodiment, a method for performing focus correction only when it is determined to be necessary, instead of performing focus correction based on temperature as described above, as needed.

[Problem to be solved in Example 7]
Basically, it is desirable to correct the focus as needed according to the temperature change, but when the temperature change occurs slightly, for example, if the focus lens is driven to correct the focus each time, the wear of the member etc. Therefore, it is conceivable that durability is lowered.

  Therefore, in this embodiment, a method for reducing the frequency of focus correction accompanied by driving of the focus lens will be described below.

[Focus Correction of Example 7 (Flow)]
A specific example will be described using the flow of FIG.

  First, the temperature detection unit 313 detects the current temperature (S1301).

  Next, the temperature acquired in the latest S1301 is compared with the temperature information acquired before the latest S1301, and the camera control unit 310 detects the temperature change amount (S1302). In this embodiment, the temperature difference between the temperature detected this time and the temperature detected last time is calculated.

  The camera control unit 310 calculates a focus correction amount corresponding to the temperature change amount detected in S1302 (S1303). The calculation method of the focus correction amount may be any method of the above-described embodiment.

  Next, the current depth information is calculated from the current camera setting status (S1304). This depth information is information indicating the range of the depth of focus as an example, and is generally calculated from the F value and the allowable circle of confusion.

  Then, the camera control unit 310 determines whether or not the calculated focus correction amount is within the depth of focus (S1305).

  When the calculated focus correction amount is within the depth of focus, focus correction is not performed. This is because it is considered that blur does not occur due to out-of-focus or that the degree of blur is within an allowable range.

  Further, assuming that the focus correction amount is within the depth of focus in S1305, if the focus correction has not been performed, the storage unit 315 stores the temperature change detected in S1302 this time. Then, it is added to the temperature change detected in the next S1302, and it is determined in the next S1305 whether the focus correction amount based on the total temperature change amount is within the depth of focus.

  On the other hand, if it is determined that it is not within the depth of focus, the camera control unit 310 controls to perform focus correction (S1306). This is because it is considered that there is a focus shift that causes blurring.

[Effect of Example 7]
As described above, when it is determined that the focus shift amount is within the depth of focus, the focus shift correction is not performed. Driving the focus lens more than necessary can be suppressed. As a result, more durability can be maintained while focusing more accurately on the subject.

[Modification of Example 7]
In addition, although it demonstrated based on the simple flow for description here, when the depth width changed by the change of imaging environment (for example, change of F value) at the time of imaging | photography, especially when the depth became shallow Even if there is no temperature change, it is desirable to perform focus correction at that time. That is, for example, it is determined whether or not there is a change in the depth range. If there is a change, correction is performed regardless of whether or not the correction amount is within the focal depth. If there is no change, the processing of S1305 to S1306 is performed.

  In addition, even when a person crosses during shooting, the drive frequency can be further suppressed by providing a dead time instead of reacting immediately.

[Example 8]
In the present embodiment, a correction method that considers not only the focus correction considering the temperature and the shooting environment but also the driving characteristics of the focus adjustment mechanism will be described.

[Problem to be solved in Example 8]
As a driving characteristic of the focus adjustment mechanism, for example, when driving by a stepping motor due to a clearance (mechanism) between gears constituting the lens barrel, the lens may not be driven by one step driving of the motor. is there.

  In such a case, the minimum drive amount is determined in the control of the drive system, and when actual drive is performed, the control is performed by performing drive exceeding this minimum drive amount.

  In the case of such a drive system, even if a temperature change occurs, if the drive amount is less than the minimum drive amount, it cannot be actually controlled. If you perform focus correction without taking this into account, if the focus correction amount is less than the minimum drive amount, it will be considered that the focus has been corrected even though the focus lens is not moving, and focus deviation correction will be performed. It is conceivable that the accuracy of this will decrease.

  Therefore, in this embodiment, focus deviation correction is performed in consideration of the minimum drive amount.

[Focus Correction of Example 8 (Flow)]
A specific example will be described using the flow of FIG.

  First, the temperature detection unit 313 detects the current temperature (S1401).

  The camera control unit 310 detects whether the temperature has changed by comparing with the temperature information acquired before the latest S1401 (S1402). In this embodiment, the temperature difference between the temperature detected this time and the temperature detected last time is calculated.

  Based on the temperature change amount detected in S1402, the camera control unit 310 calculates a focus correction amount (S1403).

  Subsequently, the camera control unit 310 determines whether or not the focus correction amount calculated in S1403 is less than the minimum drive amount (S1404). If it is less than the minimum driving amount, the focus is not corrected.

  Here, when focus correction is not performed due to less than the minimum drive amount, the temperature detected immediately before performing focus correction in the previous S1405 and the temperature change detected in the latest S1401 are stored.

  Then, the stored temperature change amount is added to the temperature change amount detected in the next step S1402, and the focus correction amount is calculated.

  On the other hand, if it is not within the minimum drive amount, the camera control unit 310 controls to perform focus correction (S1405).

[Effect of Example 8]
As described above, in this embodiment, by performing the focus correction when the temperature change amount becomes equal to or greater than the minimum drive amount, more accurate focus deviation correction can be performed in consideration of the drive characteristics of the focus adjustment mechanism. Can do.

[Other Examples]
The embodiments described so far can be combined as appropriate.

  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.

  Also, when a software program that realizes the functions of the above-described embodiments is supplied from a recording medium directly to a system or apparatus having a computer that can execute the program using wired / wireless communication, and the program is executed Are also included in the present invention.

  Accordingly, the program code itself supplied and installed in the computer in order to implement the functional processing of the present invention by the computer also realizes the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  As a recording medium for supplying the program, for example, a magnetic recording medium such as a hard disk or a magnetic tape, an optical / magneto-optical storage medium, or a nonvolatile semiconductor memory may be used.

  As a program supply method, a computer program that forms the present invention may be stored in a server on a computer network, and a connected client computer may download and program the computer program.

310 camera control unit 313 temperature detection unit 315 storage unit

Claims (6)

A lens control device in which a lens can be attached and detached,
Temperature detecting means for detecting the temperature;
First calculating means for calculating a temperature change amount from a plurality of temperatures detected by the temperature detecting means;
Storage means for storing coefficient data according to the lens;
Second calculation means for calculating a correction amount based on a calculation result by the first calculation means and a coefficient stored in the storage means; and a lens control means for controlling lens driving based on the correction amount. A lens control device comprising: The storage means stores a first coefficient corresponding to a first change amount and a second coefficient corresponding to a second change amount smaller than the first change amount corresponding to the first lens. And
When the temperature change amount calculated by the first calculation means is equal to or greater than the first change amount, the second calculation means calculates a correction amount using the first coefficient,
When the temperature change amount calculated by the first calculation means is equal to or less than the second change amount, the second calculation means calculates a correction amount using the second coefficient,
When the temperature change amount calculated by the first calculation means is less than the first change amount and greater than the second change amount, the second calculation means is configured to use the first coefficient and the second coefficient. The lens control apparatus according to claim 1, wherein the correction amount is calculated using a coefficient of the lens. The second calculation means calculates a correction amount based on the third change amount and the third coefficient calculated by the first calculation means, and a temperature change is detected by the first calculation means. Calculating a correction amount based on the third change amount and the fourth coefficient when the first time or more has elapsed since
The lens control device according to claim 1, wherein the lens control unit controls driving of the lens based on each correction amount. The lens control unit controls driving of the lens based on the correction amount calculated by the second calculation unit based on the third change amount and the third coefficient calculated by the first calculation unit. With
When a temperature change is detected by the first calculation means, a correction amount based on the third change amount and the fourth coefficient calculated by the first calculation means until the first time or more elapses. The lens control device according to claim 1, wherein driving of the lens is controlled based on the control.   The lens control unit does not drive a lens and the storage unit stores the correction amount when the correction amount calculated by the second calculation unit is within the depth of focus. The lens control device according to claim 1. A control method for a lens control device to which a lens can be attached and detached,
A temperature detection step for detecting the temperature;
A first calculation step of calculating a temperature change amount from a plurality of temperatures detected in the temperature detection step;
A storage step of storing coefficient data according to the lens;
A second calculation step for calculating a correction amount based on the calculation result in the first calculation step and the coefficient stored in the storage step; a lens control step for controlling lens driving based on the correction amount; Have
The method of controlling a lens control device, wherein the second calculation step calculates the correction amount based on a coefficient corresponding to the lens.

Images