JP5779910B2 - Infrared camera and focus position correction method - Google Patents

Description

  The present invention relates to an infrared camera and a focus position correction method, and more particularly to an infrared camera used outdoors that is easily affected by a change in the refractive index of air and a focus position correction method in the infrared camera.

  In recent years, infrared cameras that detect infrared rays emitted by a human body have been widely used for the purpose of nighttime crime prevention. In this infrared camera, germanium, which generally has a high infrared transmittance, is used as a lens material for condensing incident light. The refractive index of this germanium lens varies greatly with changes in temperature. Therefore, a method is used in which a temperature adjustment function is provided in a housing that houses the infrared camera to suppress a temperature change, or silicon or the like that has a small change in refractive index with respect to a temperature change is used as a lens material.

  However, when the temperature adjustment function is provided in the housing, there arises a problem that the size of the housing is increased and the price of the infrared camera is increased. In addition, since materials such as silicon have a lower transmittance in the far infrared region than germanium, there arises a problem that the performance of the infrared camera is deteriorated.

  With respect to such a problem, the following Patent Document 1 discloses a camera, a lens that focuses incident light and enters the camera, a temperature sensor that detects the temperature of the lens or the vicinity of the lens, and the lens. A camera device that includes a focus drive unit that corrects the focal length of the lens and a control unit that controls the focus drive unit, and drives the focus drive unit according to the temperature detected by the temperature sensor to correct the focal length Is disclosed.

JP 2003-131106 A

  In the conventional method described in Patent Document 1, the temperature coefficient of the refractive index is checked from the lens material, the focal position correction amount is stored in the memory in advance, and an appropriate correction amount is transmitted from the memory according to the temperature change amount. However, this method does not consider the influence of the change in the refractive index of air, which is indispensable in actual operation, and thus has a problem that it is impossible to detect the focus position with high accuracy and stability.

  In other words, the refractive index of air depends on the wavelength, temperature, humidity, etc., and the uneven density of air between the camera and the subject varies depending on the environmental conditions. There is a problem in that an accurate focal position cannot be detected only by correcting the focal position specialized only for the change.

  The present invention has been made in view of the above problems, and its main purpose is to detect a focal position with high accuracy and to achieve high definition even when used in an environment where the refractive index of air changes. Another object of the present invention is to provide an infrared camera and a focus position correction method capable of acquiring a simple infrared image.

To achieve the above object, the present invention provides a lens that collects infrared rays emitted from a subject, a camera that detects infrared rays collected by the lens and outputs a video signal, and detects the temperature of the lenses. In the infrared camera, comprising: a temperature sensor that adjusts a focal position by moving the lens in the optical axis direction; and a control unit that controls the focal position adjustment unit ; the stored, by referring to the table associating the temperature and the focal position of the lens, after the temperature sensor has correcting the focal position based on the detected temperature, transfer is moving in the optical axis direction the lens, the image performs control the contrast of the signal is re-correcting the focal position to a position of maximum, the control unit, peak to get the peak value of the output voltage of the video signal A peak portion, an A / D conversion portion for A / D converting the peak value, and the peak at each position when the lens is moved in a predetermined range in the optical axis direction, the peak value is the maximum And a calculation unit that identifies the position to be a focal position.

The present invention also includes a lens that collects infrared rays emitted from a subject, a camera that detects infrared rays collected by the lens and outputs a video signal, a temperature sensor that detects the temperature of the lens, a focal position correction method in the infrared camera and a focus position adjusting section that adjusts the moved focal position the lens in the optical axis direction, and stored in advance, associating the temperature and the focal position of said lens table refers to the a first step of correcting the focus position based on the temperature the temperature sensor detects, the lens is moved in the optical axis direction, the focal position to a position where the contrast of the image signal is maximum A second step of re-correction. In the second step, the projection at each position when the lens is moved in a predetermined range in the optical axis direction is performed. Comparing the peak value of the output voltage of the signal, the peak value can be configured to identify a focal position position of maximum.

  According to the infrared camera and the focal position correction method of the present invention, it is possible to detect a focal position with high accuracy and acquire a high-definition infrared image even when used in an environment where the refractive index of air changes. it can.

  The reason is that a camera that detects infrared rays and outputs a video signal, a lens that collects infrared rays and enters the camera, a focal position adjustment unit that adjusts a focal position by moving the lens in the optical axis direction, In an infrared camera including a temperature sensor that detects the temperature of a lens and a control unit, a peak hold unit that acquires a peak value of an output voltage of a video signal output from the camera, a peak value that is A / An A / D conversion unit that performs D conversion and a calculation unit that corrects the focal position are provided, and the calculation unit corrects the focal position with reference to a previously stored table based on the temperature of the lens detected by the temperature sensor. After that, the peak values at the respective positions when the lens is moved within the predetermined range from the focal position are compared, and control is performed to correct the focal position at a position where the peak value is maximum.

It is a block diagram which shows the structure of the camera part of the infrared camera which concerns on one Example of this invention. It is a block diagram which shows the function of the control part of the infrared camera which concerns on one Example of this invention. It is a block diagram which shows the structure of the camera part of the infrared camera of the former (Unexamined-Japanese-Patent No. 2003-131106). It is a block diagram which shows the function of the control part of the conventional (Japanese Unexamined Patent Publication No. 2003-131106) infrared camera.

  A conventional infrared camera disclosed in Japanese Patent Application Laid-Open No. 2003-131106 will be described. FIG. 3 is a block diagram showing the configuration of the camera unit of a conventional infrared camera. The camera unit 110 detects a lens 120 made of germanium that collects infrared rays on the camera, detects incident infrared rays, and converts them into video signals. The camera 130, the control unit 140, the electric motor 150 for adjusting the focus, the potentiometer 160 for detecting the position of the focus ring, the temperature sensor 170 for detecting the temperature near the lens 120, and the like. Electric motor 150, potentiometer 160, and temperature sensor 170 are connected to control unit 140.

  The focus position correction function in the camera unit 110 of FIG. 3 will be described with reference to the block diagram of FIG. 4 is a block diagram illustrating a configuration of the control unit 140 of the camera unit 110 of FIG. The control unit 140 includes a calculation unit 141, a storage unit 142, an operation unit 143, and the like. Then, the resistance value of the potentiometer 160 and the temperature detected by the temperature sensor 170 are output to the calculation unit 141.

  In FIG. 4, the operator uses the operation unit 143 to set the focus of the place where the user wants to shoot at the ambient temperature when the camera 130 is installed. The resistance value of the position detection potentiometer 160 and the output value (temperature) of the temperature sensor 170 at this time are stored in the storage unit 142 via the calculation unit 141. The operation unit 141 constantly monitors the output value of the temperature sensor 170, calculates a focus ring position correction amount with respect to the temperature change amount when a temperature change of a predetermined value or more occurs, and calculates the focus drive electric motor 150. Start operation. Then, the resistance value of the potentiometer 160 is monitored, and the operation of the electric motor 150 is stopped when the difference from the resistance value before the start of the electric motor 150 coincides with the controlled focus ring position correction amount.

  As described above, the conventional infrared camera described in Patent Document 1 considers only focus correction according to a temperature change stored in advance, and is based on a change in the refractive index of air that is indispensable in actual operation. Since the influence is not taken into consideration, there is a problem that it is impossible to obtain a stable and accurate focus position.

  Therefore, in an embodiment of the present invention, the maximum peak value of the output voltage of the video signal is detected in order to obtain a more accurate image in consideration of the influence of the refractive index of air between the lens and the subject. A two-stage correction is performed so that a focus blur caused by a temperature change can be corrected.

  Specifically, using the characteristic that the contrast value decreases as the focus blur increases, in the method described in Patent Document 1, when a temperature change occurs, the focus position is corrected, and then the position is corrected. The focus ring is moved back and forth within a predetermined range, the position where the peak value of the output voltage of the video signal is maximized (that is, the contrast of the video signal is maximized) is specified, and that position is set as the final focus position. .

  Thus, by adding the function for realizing the operation of the present embodiment to the conventional infrared camera described in Patent Document 1, a stable focus with high accuracy regardless of how the refractive index of air changes. The position can be detected.

  In order to describe the above-described embodiment of the present invention in more detail, an infrared camera and a focal position correction method according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram illustrating the configuration of the camera unit of the infrared camera according to the present embodiment. As in FIG. 3, the camera unit 10 includes a lens 20, a camera 30, a control unit 40, a focal position adjustment unit (electric motor). 50, a potentiometer 60), a temperature sensor 70, and the like.

  The lens 20 includes a zoom lens, a focus lens, a diaphragm, and the like, and collects infrared rays emitted from the subject on the camera 30. The camera 30 may be an infrared sensor that detects infrared rays incident through the lens 20 (a single-element sensor may be scanned two-dimensionally, a linear array sensor may be scanned one-dimensionally, or a two-dimensional array. It may be a sensor), and is configured by a signal processing unit that converts the detected infrared light into a two-dimensional infrared image video signal. The video signal is output to an image processing unit (not shown) and output to the control unit 40. The control unit 40 includes a CPU (Central Processing Unit) and a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and controls the operation of the entire camera unit 10. The electric motor 50 is a motor that operates in accordance with a control signal from the control unit 40, and adjusts the focal position by moving the lens 20 in the optical axis direction. The potentiometer 60 is a means for detecting the position (angle of the focus ring) of the lens 20 and outputs a resistance value corresponding to the position (angle) to the control unit 40. The temperature sensor 70 is configured by a thermocouple or the like, detects the temperature near the lens 20, and outputs a signal corresponding to the temperature to the control unit 40.

  FIG. 2 is a block diagram illustrating functions of the control unit 40 of the infrared camera according to the present embodiment. The control unit 40 includes a calculation unit 41, a storage unit 42, an operation unit 43, a peak hold unit 44, and an A / D conversion unit. 45 or the like.

  The calculation unit 41 obtains the temperature in the vicinity of the lens 20 from the temperature sensor 70, refers to a table that defines the correction amount of the focus ring for each temperature of the lens 20, calculates the position correction amount of the focus ring, Based on the position correction amount, the operation of the focus driving electric motor 50 is controlled. Further, the peak value of the output voltage of the video signal is acquired from the peak hold unit 44 and compared, and the position correction amount of the focus ring that maximizes the peak value (that is, the contrast of the video signal is maximized) is calculated. Based on the position correction amount, the operation of the electric motor 50 for driving the focus is controlled. The storage unit 42 stores the resistance value of the potentiometer 60, the output value of the temperature sensor 70, the above table, and the like. The operation unit 43 enables an operation for setting a focus. The peak hold unit 44 detects the peak value of the output voltage of the video signal received from the camera 30 (the peak value of the output voltage in a region other than the entire infrared image region or the region where infrared rays are not incident). The A / D conversion unit 45 digitizes the detected peak value and outputs the digitized value to the calculation unit 41.

  In FIG. 2, first, the operator operates the operation unit 43 to set the focus of the place where the photograph is desired. At this time, the focus ring rotates and a video signal is transmitted from the camera 30 to the control unit 40. The peak hold unit 44 that has received the video signal from the camera 30 detects the peak value of the output voltage of the video signal, and the A / D conversion unit 45 digitizes the peak value and transmits it to the calculation unit 41.

  When recognizing the maximum peak value, the calculation unit 41 acquires the resistance value of the position detecting potentiometer 60 at the maximum peak value, and transmits a stop signal to the electric motor 50 for driving the focus. At this time, the resistance value of the position detecting potentiometer 60 and the output value of the temperature sensor 70 are stored in the storage unit 42 via the calculation unit 41. In this way, the initial position of the lens 20 is determined.

  Next, the calculation unit 41 constantly monitors the output value of the temperature sensor 70 and acquires from the storage unit 42 a pre-stored table that defines the correction amount of the focus ring for each temperature of the lens 20. Based on the temperature acquired from the temperature sensor 70 and the table, the position correction amount of the focus ring with respect to the temperature change amount is calculated, and the operation of the focus driving electric motor 50 is started based on the position correction amount. Then, the calculation unit 41 monitors the resistance value of the potentiometer 60, and when the difference from the resistance value of the potentiometer 60 before the start of the electric motor 50 coincides with the position correction amount of the focus ring to be controlled, Stop operation.

  When the position correction by the above control is completed, the calculation unit 41 can receive the signal from the peak hold unit 44 via the A / D conversion unit 45, and moves back and forth by a predetermined amount from the previously completed correction position. A signal is transmitted to the electric motor 50 so that the focus ring operates. The peak hold unit 44 that has received the video signal from the camera 30 detects the peak value of the output voltage of the video signal, and the A / D conversion unit 45 digitizes the peak value and transmits it to the calculation unit 41.

  When the calculation unit 41 compares the peak values and recognizes the maximum peak value, the calculation unit 41 acquires the resistance value of the position detecting potentiometer 60 at the maximum peak value and transmits a stop signal to the electric motor 50. At this time, the resistance value of the position detecting potentiometer 60 and the output value of the temperature sensor 70 are stored in the storage unit 42 via the calculation unit 41. This is the final correction position. When a temperature change occurs thereafter, the same operation is performed to determine the correction position.

  As described above, in the infrared camera according to the present embodiment, the calculation unit 41 corrects the focal position with reference to the table stored in advance based on the temperature of the lens 20 detected by the temperature sensor 70, and then starts from the focal position. When the lens 20 is moved within a predetermined range, the peak value of the output voltage of the video signal at each position is obtained and compared, and the peak value is maximized (that is, the contrast of the video signal is maximized). Since the control for correcting the focal position is performed, the focal position can be detected with high accuracy and a high-definition infrared image can be obtained even when used in an environment where the refractive index of air changes. it can.

  Note that the present invention is not limited to the above-described embodiments, and the configuration and control thereof can be appropriately changed as long as the focus position correction by the method of the present invention is possible.

  For example, although the infrared camera has been described in the above embodiment, the present invention can be similarly applied to a camera that detects an arbitrary wavelength used in an environment that is easily affected by a change in the refractive index of air.

  INDUSTRIAL APPLICABILITY The present invention can be used for a camera used in an environment that is easily affected by a change in the refractive index of air, particularly an infrared camera used outdoors and a focus position correction method using the infrared camera.

DESCRIPTION OF SYMBOLS 10 Camera part 20 Lens 30 Camera 40 Control part 50 Drive motor 60 Potentiometer 70 Temperature sensor 41 Calculation part 42 Memory | storage part 43 Operation part 44 Peak hold part 45 A / D conversion part 110 Camera part 120 Lens 130 Camera 140 Control part 150 Drive motor 160 Potentiometer 170 Temperature sensor 141 Calculation unit 142 Storage unit 143 Operation unit

Claims (4)

A lens that collects infrared rays emitted from a subject, a camera that detects infrared rays collected by the lens and outputs a video signal, a temperature sensor that detects the temperature of the lens, and an optical axis direction of the lens A focal position adjustment unit that adjusts the focal position by moving to
In an infrared camera comprising a control unit that controls the focal position adjustment unit,
The controller is
The pre-stored table that associates the temperature of the lens and the focal position is referred to, and after correcting the focal position based on the temperature detected by the temperature sensor, the lens is moved in the optical axis direction, and the video infrared camera contrast signals have line control to re-correct the focal position to a position of maximum, to correct the change in the focal position due to the refractive index change of the air between said object infrared camera, characterized in that .   The control unit includes a peak hold unit that acquires a peak value of an output voltage of the video signal, an A / D conversion unit that performs A / D conversion on the peak value, and the lens that moves within a predetermined range in the optical axis direction. The infrared camera according to claim 1, further comprising: a calculation unit that compares the peaks at the respective positions when the peak values are made and specifies a position where the peak value is maximized as a focal position. A lens that collects infrared rays emitted from a subject, a camera that detects infrared rays collected by the lens and outputs a video signal, a temperature sensor that detects the temperature of the lens, and an optical axis direction of the lens A focal position adjustment unit for adjusting the focal position by moving to a focal position correction method in an infrared camera,
A first step of referring to a pre-stored table associating the temperature of the lens and the focal position and correcting the focal position based on the temperature detected by the temperature sensor;
By moving the lens in the optical axis direction and re-correcting the focal position to the position where the contrast of the video signal is maximized, the change in the focal position due to the change in the refractive index of air between the subject and the infrared camera is corrected. And a second step of performing a focal position correction method. In the second step,
The peak value of the output voltage of the video signal at each position when the lens is moved in a predetermined range in the optical axis direction is compared, and the position where the peak value is maximum is specified as the focal position. The focal position correction method according to claim 3.

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