JP5368237B2 - Temperature correction amount correction system and operation control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a compensation value to correct the INF position of a focus lens 12. <P>SOLUTION: A distance between a zoom lens HP sensor 11 and a focus lens HP sensor 17 is calculated. A lens barrel temperature is calculated based on the calculated distance. Further, a temperature (detection temperature) inside the lens barrel 1 is detected by a temperature sensor 18. When a temperature difference between the calculated lens barrel temperature and the detection temperature is equal to or more than a threshold value, the compensation value to be determined based on the detection temperature (the compensation value to correct the INF position of the focus lens 12) is corrected. Accordingly, excessive compensation is prevented in advance. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a temperature correction amount correction system and an operation control method thereof.

  In cameras (including digital still cameras, digital movie video cameras, and cameras that record optically on photographic film), plastic lenses are often used as imaging lenses to reduce costs. Yes. Since plastic lenses are easily affected by temperature, a temperature correction amount corresponding to the temperature is determined in advance, and a reference position that is used as a reference when the imaging lens moves according to the temperature correction amount is corrected. Yes (Patent Document 1). In addition, there is one that changes the driving range of the imaging lens according to the temperature (Patent Document 2).

  However, when the temperature is detected by the temperature sensor and the reference position of the imaging lens is corrected by the temperature correction amount corresponding to the detected temperature, the temperature sensor can detect the temperature accurately in response to the temperature change. Plastic lenses often do not respond sensitively to temperature changes and are gradually affected by temperature. If the reference position of the imaging lens is corrected according to the temperature correction amount corresponding to the temperature detected by the temperature sensor, accurate correction is often impossible.

Japanese Patent Laid-Open No. 11-142714 Japanese Unexamined Patent Publication No. 7-110423

  An object of the present invention is to accurately correct a temperature correction amount used for correcting a reference position of an imaging lens.

  The temperature correction amount correcting system according to the present invention includes a first sensor and a second sensor fixed in a lens barrel of a camera in which an imaging lens is movable in the optical axis direction, separated from each other in the optical axis direction. Sensor distance measuring means for measuring the sensor-to-sensor distance between the second sensor and the second sensor, lens barrel temperature calculating means for calculating the temperature of the lens barrel from the sensor-to-sensor distance measured by the sensor-to-sensor distance measuring means, A temperature sensor for detecting the temperature of the lens barrel, and a temperature difference between the temperature of the lens barrel calculated by the lens barrel temperature calculating means and the temperature of the lens barrel detected by the temperature sensor is equal to or greater than a predetermined threshold value The imaging lens moves according to the temperature of the lens barrel in response to the temperature difference determining means for determining whether or not the temperature difference is determined to be greater than or equal to a predetermined threshold by the temperature difference determining means. Characterized in that it comprises a temperature correction amount correction means for correcting a temperature correction amount for correcting the reference becomes a reference position (INF position) come.

  The present invention also provides an operation control method suitable for the temperature correction amount correction system. That is, in this method, the first sensor and the second sensor are fixed in a lens barrel of a digital camera in which the imaging lens is movable in the optical axis direction, and the distance between the sensors is measured. The means measures the distance between the first sensor and the second sensor, and the lens barrel temperature calculating means calculates the temperature of the lens barrel from the sensor distance measured by the sensor distance measuring means. The temperature sensor detects the temperature of the lens barrel, and the temperature difference determining means detects the temperature of the lens barrel calculated by the lens barrel temperature calculating means and the temperature of the lens barrel detected by the temperature sensor. Whether or not the temperature difference is greater than or equal to a predetermined threshold value, and the temperature correction amount correction means determines that the temperature difference is greater than or equal to the predetermined threshold value by the temperature difference determination means. Depending on the temperature of the tube Lens is intended to correct the temperature correction amount for correcting the reference position serving as a reference when moving.

  According to the present invention, the distance between the sensors of the first sensor and the second sensor is measured, and the temperature of the lens barrel (lens temperature) is calculated from the distance between the sensors. The temperature of the lens barrel (detected temperature) is also detected by the temperature sensor. If the temperature difference between the temperature of the lens barrel calculated from the distance between the sensors and the temperature of the lens barrel detected from the temperature sensor is equal to or greater than a predetermined threshold value, the temperature correction amount is corrected. The reference position of the imaging lens is corrected using the corrected temperature correction amount. When the temperature difference between the temperature of the lens barrel calculated from the distance between the sensors and the temperature of the lens barrel detected from the temperature sensor is equal to or greater than a predetermined threshold, the imaging lens is affected by the temperature detected by the temperature sensor. It cannot be said that it is receiving as it is. For this reason, the temperature correction amount is corrected. Since the imaging lens position is corrected using the corrected temperature correction amount, it is possible to prevent the imaging lens position from being excessively corrected as much as it is actually affected.

  Temperature change amount determination means for determining whether or not the amount of change in temperature of the lens barrel detected by the temperature sensor has increased, and determination that the amount of change in temperature of the lens barrel has increased by the temperature change amount determination means In response to this, the distance between the sensors is re-measured by the inter-sensor distance measuring means, the temperature of the lens barrel is calculated from the distance between the sensors obtained by the re-measurement, and the calculated temperature of the lens barrel and The sensor distance measuring means, the lens barrel temperature calculating means, so as to correct the temperature correction amount when a temperature difference from the temperature of the lens barrel detected by the temperature sensor is equal to or greater than a predetermined threshold value; You may make it further provide the control means which controls the said temperature sensor, the said temperature difference determination means, and the said temperature correction amount correction means.

It is a block diagram which shows the electric constitution of a digital still camera. The positional relationship between the CCD and the focus lens is shown. It is a graph which shows the relationship between temperature and a correction amount. It is a flowchart which shows the correction amount correction process procedure. It is a flowchart which shows the correction amount correction process procedure. It is a graph which shows the relationship between a temperature sensor output voltage and temperature.

  FIG. 1 is a block diagram showing an electrical configuration of a digital still camera (a digital movie video camera, which may be a camera for optically recording on a photographic film).

  The overall operation of the digital still camera is controlled by the control device 25. The control device 25 also includes a memory 26 for storing predetermined data and an AE / AF circuit 27 for automatic exposure control and automatic focusing control.

  The digital still camera includes a lens barrel 1.

  The lens barrel 1 includes lenses 2 and 5 constituting a zoom lens. The lens 5 is fixed to the lens barrel 1 by a pedestal 6. The lens 2 is held by holding tables 3 and 4. A screw hole (not shown) is formed in the holding base 4 and meshes with a screw of a lead screw 7 extending in the optical axis direction along the inner wall of the lens barrel 1. When the lead screw 7 is rotated by the zoom motor 8, the lens 2 is moved in the optical axis direction. The lens 2 has an HP (home position) position, a tele position, a wide position, etc., and the lens 2 is positioned according to the zoom amount.

  In the lens barrel 1, a focus lens 12 is provided from the CCD 21 rather than the zoom lenses 2 and 5. The focus lens 12 is held by holding bases 13 and 14. The holding base 14 is also formed with a screw hole (not shown) and meshes with a screw of the lead screw 15 extending in the optical axis direction along the inner wall of the lens barrel 1. When the lead screw 15 is rotated by the focus motor 16, the focus lens 16 is moved in the optical axis direction. The focus lens 12 also has a defined HP position. The position of the focus lens 12 is determined so that the subject image is in focus.

  A mechanical shutter 9 is provided between the lens 5 constituting the zoom lens and the focus lens 12. The mechanical shutter 9 is controlled to be opened and closed by a shutter motor 10.

  The zoom motor 8, the shutter motor 10 and the focus motor 16 are controlled by drivers 31, 32 and 33 which are controlled by a control device 25, respectively.

  In the lens barrel 1, a focus lens HP (home position) sensor (first sensor) 17 for detecting that the focus lens 12 is positioned at the HP position and a lens 5 are positioned at the HP position. A zoom lens HP sensor (second sensor) 11 is fixed. Output signals from these sensors 11 and 17 are input to the control device 27.

  Further, a temperature sensor 18 for detecting the temperature inside the lens barrel 1 is provided inside the lens barrel 1. The output voltage (output signal) from the temperature sensor 18 is input to the detection circuit 24. The signal is converted into a signal corresponding to the temperature in the detection circuit 24 and input to the control device 27.

  The video signal representing the subject image picked up by the CCD 21 is amplified by the amplifier circuit 22 and input to the process circuit 23. In the process circuit 23, predetermined processing is performed and output as a composite signal. The composite signal is also input to the control device 25, and the AE / AF circuit 27 calculates a photometric value, a focus evaluation value, and the like. Based on the calculated photometric value, the shutter speed of the mechanical shutter 9 is determined so as to obtain an appropriate exposure amount. Further, the focus lens 12 is positioned based on the calculated focus evaluation value.

  FIG. 2 shows the positional relationship between the CCD 21 and the imaging lens 12.

  As described above, the imaging lens 12 is movable in the optical axis direction. The moving range of the focus lens 12 is a position P1 closest to the CCD 21 (the HP position of the focus lens 12, the position P1 and the HP position of the focus lens 12 do not have to be the same) and a position P2 farthest from the CCD 21 ( The HP position of the lens 5 and the position P2 and the HP position of the lens 5 do not have to be the same). A reference position (INF position) is defined at a position near the position P1 between these positions P1 and P2. When the imaging lens 12 is moved for focus control, this INF position is used as a reference. With reference to the INF position, the imaging lens 12 is moved by a desired distance (the number of steps of the focus motor 16 and the amount of rotation) so that the subject image is focused. This INF position is stored in the memory 26 as a position defined by a predetermined number of steps (rotation amount) of the focus motor 16 from the HP position of the focus lens 12.

  When the focus lens 12 (and other lenses are the same) is a plastic lens, the focus motor 16 is controlled to be positioned at the position determined by the automatic focusing process in order to expand and contract under the influence of temperature. Even if it is not positioned at the determined position. Since the INF position is stored in the memory 26 as a position defined by a predetermined number of steps (rotation amount) of the focus motor 16 from the HP position of the focus lens 12, even if the number of steps is the same, it varies depending on the temperature. The focus lens 12 may be positioned at the position. Therefore, the number of steps is corrected according to the temperature in the lens barrel 1 detected by the temperature sensor 18 (correction amount by temperature).

  However, when the temperature is detected by the temperature sensor and the number of steps of the focus lens 12 is corrected by a temperature correction amount corresponding to the detected temperature, the temperature sensor can accurately detect the temperature in response to the temperature change. However, since plastic lenses are not sensitive to temperature changes and are often affected by temperature, the position of the focus lens 12 is adjusted according to the temperature correction amount corresponding to the temperature detected by the temperature sensor. In many cases, correct correction cannot be performed. In this embodiment, the correction amount according to the temperature can be further corrected according to the temperature.

  FIG. 3 shows the relationship between the detected temperature and the correction amount due to temperature.

  It is assumed that the temperature detected by the temperature sensor 18 is the temperature t1. Then, using the temperature / correction amount graph G1, it can be seen that the correction amount due to the temperature corresponding to the temperature t1 is the correction amount ΔP1. In this embodiment, as will be described later, the distance between the focus lens HP sensor 17 and the zoom lens HP sensor 11 is measured, and the lens temperature obtained from the distance between the sensors and the temperature sensor 18 are obtained. When the temperature difference from the detected temperature is equal to or greater than a predetermined threshold value, the correction amount ΔP1 obtained as described above is corrected.

  For example, if the detected temperature t1 is higher than the lens barrel temperature and the temperature difference between the lens barrel temperature and the detected temperature is equal to or greater than the threshold value, the temperature correction amount graph is not the temperature correction amount graph G1. The correction amount is calculated using a temperature correction amount graph G2 that is smaller than the correction amount obtained by G1. For example, in the case of the detected temperature t1, the correction amount obtained using the temperature correction amount graph G2 is ΔP2. This correction amount ΔP2 corresponds to the correction amount calculated using the temperature correction amount graph G1 when the detected temperature is a temperature t2 lower than the temperature t1. When the detected temperature is higher than the lens barrel temperature, the focus lens expands due to the temperature, but since it is not affected as much as the temperature detected by the temperature sensor 18, it is actually affected. The correction amount is calculated using the temperature / correction amount graph G2 that gives the correction amount ΔP2 for the possible lens barrel temperature (correction of correction amount).

  Conversely, if the detected temperature t1 is lower than the lens barrel temperature and the temperature difference between the lens barrel temperature and the detected temperature is equal to or greater than the threshold value, the temperature correction amount is not the temperature correction amount graph G1. The correction amount is calculated using a temperature correction amount graph G3 that is larger than the correction amount obtained from the graph G1. For example, in the case of the detected temperature t1, the correction amount obtained using the temperature correction amount graph G3 is ΔP3. This correction amount ΔP3 corresponds to the amount of correction calculated using the temperature correction amount graph G1 when the detected temperature is a temperature t3 higher than the temperature t1. When the detected temperature is lower than the lens barrel temperature, the focus lens contracts due to the temperature, but it is not affected as much as the temperature detected by the temperature sensor 18, so it is actually affected. A correction amount is calculated using a temperature / correction amount graph G3 that provides a correction amount ΔP3 for the possible lens barrel temperature.

  Data representing such graphs G1 to G3 is stored in the memory 26 described above.

  4 and 5 are flowcharts showing a processing procedure for correcting the correction amount due to temperature.

  When the power of the digital still camera is turned on, the movable lens 2 constituting the zoom lens is positioned on the zoom lens HP (step 41 in FIG. 4). Subsequently, the lens 2 is positioned at the wide position (step 42 in FIG. 4).

Then, the focus lens 12 is positioned at a position P1 (HP of the focus lens 12) closest to the CCD 21, which is a position detected by the focus HP sensor 17 (step 43 in FIG. 4). Subsequently, the focus lens 12 is positioned at a position detected by the zoom lens HP sensor 11 and farthest from the CCD 21 (HP of the zoom lens) (step 44 in FIG. 4).

  The distance between the sensors of the focus HP sensor 17 and the zoom lens HP sensor 11 is calculated (step 46 in FIG. 4). Since the focus lens 12 is moved by the focus motor 16, the distance between the sensors can be calculated from the number of steps of the focus motor 16. The lens barrel temperature t2 that substantially affects the lens in the lens barrel 1 is calculated from the calculated inter-sensor distance (step 47 in FIG. 4). Data representing the distance between the sensors at the reference temperature, which is a standard temperature, is stored in the memory 26, and the lens barrel temperature t2 can be calculated based on the difference from the distance between the sensors at the reference temperature.

  Subsequently, the temperature (detected temperature) t1 in the lens barrel 1 detected by the temperature sensor 18 is read (step 48 in FIG. 5). As described above, the correction amount ΔP1 based on the temperature is determined from the detected temperature t1 (step 49 in FIG. 5).

  If the temperature difference Δt between the detected temperature t1 of the temperature sensor 18 and the lens barrel temperature t2 calculated from the distance between the sensors is equal to or greater than the threshold value, the correction amount is set as described above based on the detected temperature t1 of the temperature sensor 18. If calculated, the error may increase. Therefore, if the temperature difference Δt between the detected temperature t1 of the temperature sensor 18 and the lens barrel temperature t2 calculated from the distance between the sensors is equal to or greater than a threshold value (YES in step 50 in FIG. 5), correction based on the detected temperature t1. As described above, the amount ΔP1 is corrected so as not to be overcorrected (step 51 in FIG. 5). As described above, the correction amount ΔP1 is corrected so as to decrease if the detected temperature t1 is higher than the lens barrel temperature t2 (ΔP2). Conversely, if the detected temperature t1 is lower than the lens barrel temperature t2, the correction amount ΔP1 increases. (ΔP3). The correction amount ΔP1 can be corrected by adding or subtracting the correction amount to the calculated correction amount ΔP1. If the temperature difference is not greater than or equal to the threshold value (NO in step 50 in FIG. 5), the correction amount ΔP1 is not corrected.

  The INF position of the focus lens 12 is corrected with the corrected temperature correction amount or the uncorrected temperature correction amount (step 52 in FIG. 5). That is, the number of steps from the HP of the focus lens 12 is corrected based on the temperature correction amount. For example, in the case of the reference temperature, if the INF position is the focus motor 16 and is 20 steps from the HP position of the focus lens 12, the focus lens 12 is moved to the HP position when there is no temperature effect. Is moved to the INF position by moving 20 steps. If the temperature difference is less than the threshold value, the number of steps is corrected by the correction amount ΔP1 obtained from the detected temperature t1 of the temperature sensor 16, so that the focus lens 12 is moved to the HP position. Is moved to the INF position by moving (20 + ΔP1) steps. Further, when there is an influence of temperature and the temperature difference is equal to or greater than the threshold value, the correction amount ΔP1 obtained from the detected temperature t1 of the temperature sensor 16 is further corrected by the corrected amount ΔP2 or ΔP3. Therefore, the focus lens 12 is positioned at the INF position by moving (20 + ΔP2) or (20 + ΔP3) steps from the HP position.

  If no termination command is given (NO in step 53), it is determined whether or not the amount of change in the detected temperature t1 of the temperature sensor 16 has become greater than a predetermined threshold value (step 54 in FIG. 5). When the change amount of the detected temperature t1 is larger than a predetermined threshold value (YES in step 54 in FIG. 5), the focus lens 12 is positioned closest to the CCD 21 so as to measure the distance between the sensors again. (Step 44 in FIG. 4). If the change amount of the detected temperature t1 is not larger than the predetermined threshold value (NO in step 54 in FIG. 5), the processing from step 48 is repeated without measuring the inter-sensor distance again. Although it is not desirable to measure the distance between sensors many times, the distance between sensors is measured only when necessary because the distance between sensors is measured when the amount of change in the detected temperature t1 of the temperature sensor 16 increases. it can.

  FIG. 6 shows a modification, and shows the relationship between the output voltage of the temperature sensor 16 and the temperature.

  An output voltage / temperature graph G11 is defined. When the output voltage of the temperature sensor 16 is known, the temperature is detected using the output voltage / temperature graph G11. For example, if the output voltage is V1, the temperature is t11.

  As described above, the temperature difference between the temperature detected by the temperature sensor 16 is higher than the lens barrel temperature calculated from the distance between the sensors and the temperature detected by the temperature sensor 16 and the lens barrel temperature calculated from the distance between the sensors. If the threshold value is exceeded, the output voltage is converted to temperature using an output voltage / temperature graph G12 that lowers the detected temperature. Further, the temperature detected by the temperature sensor 16 is lower than the lens barrel temperature calculated from the distance between the sensors, and the temperature difference between the temperature detected by the temperature sensor 16 and the lens barrel temperature calculated from the distance between the sensors is equal to or greater than a threshold value. In this case, the output voltage is converted into temperature using an output voltage / temperature graph G13 in which the detected temperature becomes high.

  As described above, even if the temperature itself detected from the temperature sensor 16 is corrected, the correction amount described above can be substantially corrected.

  Although the focus lens 12 has been described in the above-described embodiments, it goes without saying that the present invention can be similarly applied not only to the focus lens 12 but also to a zoom lens.

1 Lens tube 2, 5, 12 lenses
11 Zoom lens HP sensor (second sensor)
17 Focus lens HP sensor (first sensor)
18 Temperature sensor

Claims (3)

A first sensor and a second sensor which are fixed in the optical axis direction within a lens barrel of a camera in which the focus lens is movable in the optical axis direction;
From the rotation amount of the focus motor when the focus lens is moved from the position of the first sensor to the position of the second sensor by a focus motor, the first sensor and the second sensor A sensor-to-sensor distance measuring means for measuring a sensor-to-sensor distance;
Lens barrel temperature calculating means for calculating the temperature of the lens barrel from the distance between sensors measured by the sensor distance measuring means;
A temperature sensor for detecting the temperature of the lens barrel,
Temperature difference determining means for determining whether a temperature difference between the temperature of the lens barrel calculated by the lens barrel temperature calculating means and the temperature of the lens barrel detected by the temperature sensor is equal to or greater than a predetermined threshold; and Temperature correction that corrects a reference position as a reference when the imaging lens moves in accordance with the temperature of the lens barrel in response to the temperature difference being determined to be equal to or greater than a predetermined threshold by the temperature difference determining means. Temperature correction amount correction means for correcting the amount,
Temperature correction amount correction system equipped with. Temperature change amount determining means for determining whether or not the amount of change in temperature of the lens barrel detected by the temperature sensor has increased, and determining that the amount of change in temperature of the lens barrel has increased by the temperature change amount determining means. In response to this, the distance between the sensors is re-measured by the inter-sensor distance measuring means, the temperature of the lens barrel is calculated from the distance between the sensors obtained by the re-measurement, and the calculated temperature of the lens barrel and The sensor distance measuring means, the lens barrel temperature calculating means, so as to correct the temperature correction amount when a temperature difference from the temperature of the lens barrel detected by the temperature sensor is equal to or greater than a predetermined threshold value; Control means for controlling the temperature sensor, the temperature difference determining means, and the temperature correction amount correcting means;
The temperature correction amount correction system according to claim 1, further comprising: The first sensor and the second sensor are fixed within the lens barrel of the camera in which the focus lens is movable in the optical axis direction and are separated from each other in the optical axis direction within the movement range of the focus lens. And
An inter-sensor distance measuring means is configured to detect the first lens based on a rotation amount of the focus motor when the focus lens is moved from the position of the first sensor to the position of the second sensor by a focus motor . Measure the distance between the sensor and the second sensor,
The lens barrel temperature calculating means calculates the temperature of the lens barrel from the inter-sensor distance measured by the inter-sensor distance measuring means,
A temperature sensor detects the temperature of the lens barrel,
The temperature difference determining means determines whether the temperature difference between the temperature of the lens barrel calculated by the lens barrel temperature calculating means and the temperature of the lens barrel detected by the temperature sensor is equal to or greater than a predetermined threshold value. ,
The temperature correction amount correction means becomes a reference when the imaging lens moves according to the temperature of the lens barrel in response to the temperature difference being determined by the temperature difference determination means to be equal to or greater than a predetermined threshold value. Correct the temperature correction amount to correct the reference position.
Operation control method of temperature correction amount correction system.

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