JP4534740B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus mainly used for an outdoor surveillance camera, and more particularly to an imaging apparatus having an autofocus function.

In autofocus control in a conventional imaging apparatus, as shown in Patent Document 1, for example, the focus position is moved from the FAR (far distance) end to the NEAR (near distance) end, and the high frequency component of the video signal associated therewith peaks This is achieved by stopping the focus lens at the focus position. Also, in autofocus control when a long life is required like a surveillance camera, peak detection is performed only once for each autofocus operation command, and autofocus operation is not continued thereafter. By performing the control, the life of the focus lens is extended.
Japanese Patent Laid-Open No. 11-69225 (FIG. 1)

  Autofocus control in conventional outdoor surveillance camera devices is configured as described above, and peak detection fails for subjects that have low high-frequency components in the video signal and are difficult to autofocus (for example, when the subject illumination is dark or horizontal stripes). It may be easy to define the focus position. In this case, it stops at an arbitrary position such as a FAR end, a NEAR end, or a position before starting autofocus. Also, in the case of one-push autofocus control that detects the peak only once, it stops at an arbitrary position even if the focus position cannot be detected. In some cases, it can be stopped at a position where the focus shift becomes larger than before autofocus activation. There was a certain problem.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to obtain an imaging apparatus capable of minimizing the amount of focus deviation even when the peak detection of a high frequency component fails in autofocus control. Objective.

  An imaging apparatus according to the present invention includes a lens that collects a subject, an imaging unit that images the condensed subject, a high-frequency extraction unit that extracts a high-frequency component of the subject imaged by the imaging unit, and the high-frequency extraction unit When the peak value can be detected from the extracted high-frequency component, the focus position is a calculated position from the peak value, and when the peak value cannot be detected, the control unit sets the focus position to the infinity position. is there.

  According to the present invention, when the control unit can detect the peak value from the high-frequency component extracted by the high-frequency extraction means, the imaging device sets the focus position as the calculated position from the peak value, and when the peak value cannot be detected. Since the focus position is set at infinity, most of the outdoor subject distance is far away, so there is an effect that the focus shift that may occur can be minimized.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of the imaging apparatus shown in Embodiment 1 of the present invention. In Embodiment 1, when the present invention is used for an outdoor surveillance camera, the object position to be imaged is mostly far away, and the focus position is set when the peak detection of the high frequency component fails in auto focus control. An example will be shown in which the focus shift is reduced by moving to an infinite position compared to before auto-focus activation. The lens 1 includes a focus lens and a zoom lens, and the image pickup apparatus also has a zoom lens driving function, but illustration thereof is omitted.

  In FIG. 1, 1 is a lens, 2 is a CCD, 3 is CDS / AGC / AD, 4 is a BPF, 5 is an integrator, 6 is a microcomputer, 7 is a focus drive circuit, 8 is a focus motor, and 9 is a focus position. The focus potentiometer.

  Next, the operation will be described. First, the flow until the high frequency component of the video is input to the microcomputer 6 will be described. Incident light from the subject is imaged on the CCD 2 by the lens 1. The light imaged on the CCD 2 is converted into an electrical signal, reset noise removal, signal level optimization, and signal AD conversion are performed by the CDS / AGC / AD 3 and sent to the video signal processing portion at the subsequent stage. The AD-converted signal is also sent to the BPF 4 at the same time, and a high-frequency component effective for performing autofocus control is extracted and output to the integrator 5. The integrator 5 integrates the signal from the BPF 4 in units of one screen, and outputs it to the microcomputer 6 as a high frequency component amount for one screen.

  Next, the operation of the microcomputer 6 will be described. FIG. 2 is an operation flowchart of the microcomputer 6 shown in FIG. Then, referring to FIG. 2, first, the processing of microcomputer 6 starts in step S1. This process is started based on an autofocus operation command from the outside. The autofocus operation command is output after the operator has driven the zoom lens and set the angle of view that is the imaging range.

  Subsequently, in step S2, an autofocus process is started. In the autofocus process, while the high frequency component from the integrator 5 and the focus position from the focus potentiometer 9 are acquired, an instruction is given to the focus drive circuit 7 to drive the focus motor 8, and the focus lens 1 is moved from the FAR end to the NEAR end, for example. The position where the value of the high frequency component reaches a peak is detected. When the peak of the high frequency component is detected, the peak position is stored and the focus position of the peak portion is stored after the state is informed that the peak has been detected, and the process proceeds to step S3. On the other hand, if peak detection cannot be performed in the entire area from the FAR end to the NEAR end, a state indicating that peak detection has not been performed is held, and the process proceeds to step S3.

  In step S3, the microcomputer 6 determines whether or not the peak of the high frequency component has been detected based on the status of the autofocus processing result. If the peak of the high frequency component has been detected, the peak cannot be detected in step S4. In this case, the process proceeds to step S5. Hereinafter, the case where the peak of the high frequency component can be detected and the case where the peak cannot be detected will be described separately.

  (A) When the peak of the high frequency component can be detected, the following processing is performed to move the focus lens to the position where the peak of the high frequency component is detected.

  First, in step S4, the focus lens is moved to a position where the peak of the high frequency component is detected. When the peak of the high frequency component is detected, the focus position of the peak portion is stored in the autofocus process in step S2, so that the focus drive circuit 7 is instructed while acquiring the focus position from the focus potentiometer 9. Then, the focus motor 8 is driven to stop the focus lens at a position where the current focus position matches the stored focus position. Thereby, the focus lens can be moved to the position where the peak of the high frequency component is detected.

  Next, in step S6, the microcomputer process is terminated.

  (B) When the peak of the high frequency component cannot be detected, in this case, the following processing is performed in order to move the focus lens to the infinity position.

  First, in step S5, the focus lens is moved to an infinite position. While acquiring the focus position from the focus potentiometer 9, an instruction is given to the focus drive circuit 7 to drive the focus motor 8, and the focus lens is stopped at a position where the current focus position and the focus position at infinity coincide, The focus lens can be moved to an infinite position. Note that the infinity position of the focus is different from the position of the FAR end in the case of a lens with an overinf setting often used in monitoring applications.

  For this reason, in order to move the focus lens to the infinity position, it is necessary to store the infinity position in advance. This is because the object at infinity in the collimator is photographed at the telephoto (telephoto) end of the zoom lens, and the value of the focus potentiometer 9 when the object is focused on is obtained and stored in the microcomputer 6. Can be realized.

  Next, in step S6, the microcomputer process is terminated.

  As described above, according to the first embodiment, when the peak of the high frequency component cannot be detected in the autofocus processing, the focus lens is moved to the infinity position, so that most subjects are far away. It is possible to minimize the amount of focus deviation that may occur in the imaging of a certain outdoor surveillance camera.

Embodiment 2. FIG.
FIG. 3 is a configuration diagram of the imaging apparatus shown in Embodiment 2 of the present invention. In Embodiment 2, a case will be described in which the present invention is used for an outdoor surveillance camera apparatus in which the imaging range changes by a turntable or the like. The subject position of outdoor surveillance cameras that monitor dam rivers, etc., is unlikely to change for the same surveillance target, and the zoom position is used whenever the peak of high-frequency components can be detected by autofocus control using the characteristics that most are far away Record the turntable position and focus position.

  As a result, when the peak detection of the high frequency component fails, the presence / absence of the peak detection example of the high frequency component in the imaging range based on the recorded zoom position and turntable position is confirmed. In this example, the focus lens is moved to the past focus position, and when there is no detection example, the focus lens is moved to infinity, thereby reducing the focus shift before the autofocus activation.

  In FIG. 3, 10 is a lens, 11 is a CCD, 12 is a CDS / AGC / AD, 13 is a BPF, 14 is an integrator, 15 is a microcomputer, 16 is a focus drive circuit, 17 is a focus motor, and 18 is a position of the focus lens. Is a focus potentiometer that can detect the zoom lens, 19 is a zoom potentiometer that can detect the position of the zoom lens, and 20 is a turntable position output unit that outputs the position of the turntable. The lens 10 includes a focus lens and a zoom lens, and the image pickup apparatus includes a zoom motor that drives the zoom lens, but illustration thereof is omitted.

  Next, the operation will be described. First, the flow until the high frequency component of the video is input to the microcomputer 15 will be described. Incident light from the subject is focused on the CCD 11 by the lens 10. The light imaged on the CCD 11 is converted into an electric signal, and reset noise removal, signal level optimization, and signal AD conversion are performed by the CDS / AGC / AD 12 and sent to the video signal processing portion at the subsequent stage. The AD converted signal is also sent to the BPF 13 at the same time, and a high frequency component effective for performing autofocus control is extracted and output to the integrator 14. The integrator 14 integrates the signal from the BPF 13 in units of one screen, and outputs the signal to the microcomputer 15 as a high-frequency component amount for one screen.

  Next, the operation of the microcomputer 15 will be described. FIG. 4 is an operation flowchart of the microcomputer 15 shown in FIG. FIG. 5 is a focus position table that can be referred to by the microcomputer 15 shown in FIG. 4, in which a focus position that has been successfully detected in the past, a zoom position at the focus position, and a turntable position are recorded. Furthermore, when there is a margin in the recording capacity, if the angle of view (imaging range) calculated from the zoom position and the turntable position is recorded, the search described later can be easily performed. In the following, the description is advanced by recording the angle of view. Then, referring to FIG. 4, first, the processing of microcomputer 15 starts in step S7. This process is started based on an autofocus operation command from the outside.

  Subsequently, in step S8, an autofocus process is started. In the autofocus process, the focus drive circuit 16 is instructed while acquiring the high frequency component from the integrator 14 and the focus position from the focus potentiometer 18 to drive the focus motor 17, and the focus lens is sequentially moved from the FAR end to the NEAR end. The position where the value of the high-frequency component reaches a peak is detected by moving. If the peak of the high frequency component is detected, it is determined that the peak has been detected, the state to that effect is retained, the focus position of the peak portion is stored, and the process proceeds to step S9. On the other hand, if a peak is not detected in the entire region from the FAR end to the NEAR end, the state indicating that the peak cannot be detected is held and the process proceeds to step S9.

  In step S9, the microcomputer 15 determines whether or not the peak of the high frequency component has been detected based on the status of the autofocus processing result. If the peak of the high frequency component has been detected, the peak cannot be detected in step S10. In this case, the process proceeds to step S14. Hereinafter, the case where the peak of the high frequency component can be detected and the case where the peak cannot be detected will be described separately.

  (C) When the peak of the high frequency component can be detected, the following processing is performed to move the focus lens to the position where the peak of the high frequency component is detected.

  First, in step S10, the current zoom lens position is acquired. The zoom position is acquired from the zoom potentiometer 19. In order to obtain a value when the peak of the high frequency component is detected, it is assumed that there is no zoom operation after the detection of the high frequency component peak until the zoom position acquisition.

  Next, in step S11, the current position of the turntable is acquired. The turntable position is acquired from the turntable position output unit 20. In order to obtain a value when the peak of the high frequency component is detected, it is assumed that there is no turntable operation between the detection of the high frequency component peak and the acquisition of the position of the turntable.

  Next, in step S12, the zoom position acquired in step S10 and the turntable position acquired in step S11 are stored. The focus position stored in step S8 is stored in the same status as the zoom position and the turntable position, and the stored focus position, zoom position, and turntable position are recorded in the focus position table. In addition, the angle of view calculated from the zoom position and the turntable position is recorded in the focus position table. Note that it is possible to calculate the angle of view of the zoom lens from the zoom position by a known technique, and it is also possible to calculate the angle of view at the absolute position by adding the position of the turntable.

  Next, the focus lens is moved to the position where the peak of the high frequency component is detected in step S13. When the peak of the high frequency component is detected, the focus position of the peak portion is stored in the autofocus process in step S8, so an instruction is issued to the focus drive circuit 16 while acquiring the focus position from the focus potentiometer 18. By driving the focus motor 17 and stopping the focus lens at a position where the current focus position matches the stored focus position, the focus lens can be moved to the position where the peak of the high frequency component is detected. .

  Next, in step S19, the microcomputer process is terminated.

  (D) When the peak of the high frequency component cannot be detected, the following processing is performed to move the focus lens to the focus position recorded in the focus position table or the infinity position.

  First, in step S14, the current zoom position is acquired. The zoom position is acquired from the zoom potentiometer 19.

  Next, the current turntable position is acquired in step S15. The turntable position is acquired from the turntable position output unit 20.

  Next, in step S16, the angle of view recorded in the focus position table in the process of step S12 is compared with the current angle of view to determine whether there is something similar.

  That is, the current angle of view is compared with the angle of view recorded in the focus position table, and the one closest to the current monitoring angle of view is selected from the recorded angle of view. Next, the degree of overlap of the angle of view between the angle of view selected in the above process and the current angle of view is confirmed, and the stored zoom position selected when the overlap is equal to or greater than an assumed value, for example, 50% or greater. Then, it is determined that the turntable position is the same as the current zoom position and turntable position, the focus position is selected, and the process proceeds to step S17.

The above operation will be described in more detail. For example, when a 1 / 2-type CCD is used as the CCD 11, the zoom position recorded in the focus position table is 20 mm, the rotary table position is 50 ° in the pan direction, and the tilt direction is 0 °. Then, the angle of view recorded in the focus position table is
・ Horizontal angle of view = 2 × tan ⁻¹ ((CCD length / 2) / zoom position)
= 2 × tan ⁻¹ ((6.4 / 2) / 20)
= 2 × tan ⁻¹ (0.16)
= 18.18 °
Calculate absolute position from turntable position + direction ... turntable position + angle of view / 2 = 59.09 °
-Direction ... turntable position-angle of view / 2 = 40.91 °
・ Vertical angle of view = 2 x tan ^-1 ((CCD length / 2) / zoom position)
= 2 × tan ⁻¹ ((4.8 / 2) / 20)
= 2 × tan ⁻¹ (0.12)
= 13.68 °
Calculate absolute position from turntable position + direction: turntable position + angle of view / 2 = 6.84 °
-Direction ... rotary table position-angle of view / 2 = -6.84 °
It becomes.

In contrast, the current zoom position is 19 mm, the turntable position is 48 ° in the pan direction, and the tilt direction is 2 °. Then, the angle of view at the current position is
・ Horizontal angle of view = 2 × tan ⁻¹ ((6.4 / 2) / 19)
= 2 × tan ⁻¹ (0.16842)
= 19.12 °
Calculate absolute position from turntable position + direction ... turntable position + angle of view / 2 = 57.56 °
-Direction ... turntable position-angle of view / 2 = 38.44 °
・ Vertical direction Angle of view = 2 × tan ⁻¹ ((4.8 / 2) / 19)
= 2 × tan ⁻¹ (0.1263)
= 14.40 °
Calculate absolute position from turntable position + direction ... turntable position + angle of view / 2 = 9.20 °
-Direction ... rotary table position-angle of view / 2 = -5.20 °
It becomes.

Next, the calculation of the degree of similarity is
・ Horizontal overlapping angle of view… 40.91 ° ～ 57.56 °
Angle of view between the extreme + end and the extreme end ... 38.44 ° to 59.09 °
Overlap ratio = Duplicated angle of view / Overall angle of view
= (57.66-40.91) / (59.09-38.44)
= 16.75 / 20.65
= 0.81
・ Vertical direction Overlapping angle of view… -5.20 ° ～ 6.84 °
Angle of view between the extreme + end and the extreme end ... -6.84 ° to 9.20 °
Overlap ratio = Duplicated angle of view / Overall angle of view
= (6.84 + 5.20) / (9.20 + 6.84)
= 12.04 / 16.04
= 0.75
・ Overall overlap ratio = Horizontal overlap ratio x Vertical overlap ratio = 0.81 * 0.75
= 0.6075
In this case, since it is 50% or more, it is determined that the degree of overlap is higher than expected and is similar.

  As described above, the focus position table is searched, the one closest to the current angle of view is selected, and the process proceeds to step S17. If the angle of view corresponding to the above condition is not found by searching the focus position table, it is determined that there is no similar position in the focus position table, and the process proceeds to step S18. In the following, the zoom position, the turntable position, the current zoom position, and the turntable position recorded in the focus position table will be described separately when there is something similar and when there is no similar thing.

  (E) To compare the angle of view recorded in the focus position table with the current angle of view and to find a similar one, to move the focus lens to the focus position corresponding to the angle of view selected in step S16. In addition, the following processing is performed.

  First, in step S17, the focus lens is moved to the focus position corresponding to the recorded angle of view selected in step S16. While acquiring the focus position from the focus potentiometer 18, an instruction is given to the focus drive circuit 16 to drive the focus motor 17, and the focus lens is stopped at a position where the current focus position and the selected focus position coincide with each other, The focus lens can be moved to the selected focus position.

  Next, in step S19, the microcomputer process is terminated.

  (F) Focus position table When the recorded angle of view is compared with the current angle of view and there is no similarity, the following processing is performed to move the focus lens to the infinity position in this case. The

  First, in step S18, the focus lens is moved to an infinite position. While acquiring the focus position from the focus potentiometer 18, the focus drive circuit 16 is instructed to drive the focus motor 17, and the focus lens is stopped at a position where the current focus position and the focus position at infinity coincide, The focus lens can be moved to an infinite position.

  Next, in step S19, the microcomputer process is terminated.

  As described above, according to the second embodiment, when the peak of the high frequency component cannot be detected in the autofocus process, the imaging range being imaged is compared with the imaging range recorded by the focus position table, and similar. If there is an imaging range, the focus position is set as the focus position recorded corresponding to the imaging range. Generally, subject distances such as dams and rivers that are monitored by outdoor surveillance cameras are less likely to change within the same monitoring angle of view, so that the amount of focus deviation that can occur due to the above operations can be minimized. it can.

  If there is no similar imaging range, the focus position is set to the infinity position. In general, since most subjects of the outdoor surveillance camera are far away, the amount of focus shift that may occur due to the above-described operation can be minimized. Further, when the microcomputer 15 detects a peak value from the high frequency component, the corresponding focus position and the angle of view as the imaging range are recorded in the focus position table, so that the number of search targets increases and the rate at which a similar imaging range can be extracted increases. To do. If the angle of view is also recorded in the focus position table in advance, the search process can be performed easily. Furthermore, since the extraction of the angle of view is calculated from the position of the turntable, the angle of view can be calculated at the absolute position.

  As an application example of the present invention, it can be used for an outdoor monitoring camera for monitoring a dam, a river or the like.

It is a block diagram of the imaging device shown in Embodiment 1 of this invention. It is an operation | movement flowchart of the microcomputer shown in FIG. It is a block diagram of the imaging device shown in Embodiment 2 of this invention. It is an operation | movement flowchart of the microcomputer shown in FIG. 5 is a focus position table that can be referred to by the microcomputer shown in FIG.

Explanation of symbols

1 Lens 2 CCD
3 CDS / AGC / AD
4 BPF
5 Integrator 6 Microcomputer 7 Focus Drive Circuit 8 Focus Motor 9 Focus Potentiometer 10 Lens 11 CCD
12 CDS / AGC / AD
13 BPF
14 Integrator 15 Microcomputer 16 Focus Drive Circuit 17 Focus Motor 18 Focus Potentiometer 19 Zoom Potentiometer 20 Turntable Position Output Unit

Claims (3)

A lens that focuses the subject,
Imaging means for imaging the condensed subject;
High-frequency extraction means for extracting high-frequency components of the subject imaged by the imaging means;
A control unit that detects a focus position from the high-frequency component extracted by the high-frequency extraction unit, and moves a focus lens to the focus position, and has a predetermined imaging range that is changed by rotation of a turntable provided at the predetermined position. In an imaging device for imaging,
A focus position recording unit that records a focus position in the predetermined imaging range captured by the imaging unit ;
A first step in which when the peak value can be detected from the high frequency component extracted by the high frequency extraction means , the control unit sets the focus position to a position calculated from the peak value;
If the peak value cannot be detected in the first step, the imaging range being imaged is compared with the imaging range recorded by the focus position recording means. If there is a similar imaging range, the focus position corresponds to the imaging range. The second step to set the recorded focus position,
An imaging apparatus, wherein if there is no similar imaging range in the second step, a third step is performed in which the focus position is set to an infinite position. Control unit, high-frequency extraction means imaging apparatus as in claim 1, wherein said be recorded on the focus position recording means and the corresponding focus position and the imaging range when detecting a peak value from the high-frequency component extracted by the . The imaging apparatus according to claim 1 or 2 , wherein extraction of an imaging range is calculated from a position of a turntable that drives the imaging apparatus.

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