JP6472209B2 - Imaging device, control method thereof, and control program - Google Patents

Description

  The present invention relates to an imaging apparatus including an infrared light reduction unit that can be inserted into and removed from an optical path of a photographing optical system, a control method thereof, and a control program, and in particular, an imaging apparatus that inserts and removes an infrared light reduction unit according to illuminance of a subject. About.

  Conventionally, in an imaging apparatus such as a digital camera, a method of selectively inserting and removing an infrared cut filter, which is an infrared light reduction unit, from an optical path of a photographing optical system according to the illuminance of a subject and switching a photographing mode (hereinafter referred to as auto day / night) ) Is used.

  In auto day / night, when the illuminance of the subject is higher than a predetermined illuminance, an infrared cut filter is inserted in the optical path to cut near infrared light (wavelength = about 700 nm or more). On the other hand, when the illuminance of the subject is equal to or lower than the predetermined illuminance, the infrared cut filter is removed from the optical path, and light in the near infrared region is allowed to pass through to increase sensitivity.

  As described above, when light in the near infrared region passes, the color balance in the image is lost. Therefore, when the infrared cut filter is removed, the shooting mode is changed from the color image mode (day mode) to the monochrome image mode (night mode). Mode).

  When detecting the illuminance of the subject, for example, the illuminance (that is, luminance) of the subject is detected by an image signal that is an output of an image sensor such as a CMOS image sensor, or provided separately from the photographing optical system. The illuminance of the subject is detected using an illuminance sensor.

  Furthermore, some imaging apparatuses include an infrared illuminating unit so that the subject is illuminated with infrared light by the infrared illuminating unit in the night mode. In this imaging apparatus, the subject is reliably photographed even under low illuminance by performing illumination with infrared light (see Patent Document 1).

JP 2004-229034 A

  By the way, when the shooting mode is switched based on the subject luminance obtained in accordance with the image signal that is the output of the image sensor, the signal level of the image signal varies greatly between the day mode and the night mode. As a result, a so-called hunting phenomenon occurs in which the photographing mode is repeatedly switched in a short time.

  In order to prevent such a hunting phenomenon, it is conceivable to switch to the day mode when the subject illuminance becomes brighter than the subject illuminance obtained after switching to the night mode. However, in an imaging device including an infrared illumination unit, when the light emission intensity in the infrared illumination unit changes, it becomes difficult to switch the shooting mode at a desired timing.

  On the other hand, in the image pickup apparatus described in Patent Document 1, although the illuminance of the subject is detected using an illuminance sensor provided separately from the photographing optical system, the image pickup apparatus needs to be provided with an illuminance sensor separately. Therefore, the cost of the imaging device itself increases.

  Accordingly, an object of the present invention is to provide an image pickup capable of switching the shooting mode at a desired timing without causing a hunting phenomenon even when the shooting mode is switched when shooting with infrared light. An apparatus, a control method thereof, and a control program are provided.

In order to achieve the above object, an image pickup apparatus according to the present invention is an image pickup apparatus having an image pickup element that forms an optical image via a shooting optical system and outputs an image signal corresponding to the optical image. Infrared light reducing means for reducing the amount of infrared light contained in the optical image that is inserted in an optical path between the optical system and the image sensor and reaches the image sensor, and a subject according to the image signal Detection means for detecting luminance and obtaining illuminance detection results, illumination means for illuminating the subject with infrared light, and the light path of the infrared light reduction means with respect to the optical path according to the intensity of infrared light emitted by the illumination means Correction means for correcting a threshold value at the time of insertion , control means for comparing the illuminance detection result with the corrected threshold value, and inserting the infrared light reduction means into the optical path according to the comparison result; It is characterized by having.

According to the control method of the present invention, an optical image is formed through a photographic optical system, and an image sensor that outputs an image signal corresponding to the optical image is inserted into an optical path between the photographic optical system and the image sensor. A control method for an imaging apparatus, comprising: infrared light reduction means for reducing the amount of infrared light contained in the optical image that reaches the imaging element; and illumination means for illuminating a subject with infrared light Detecting the luminance of the subject according to the image signal to obtain an illuminance detection result, and inserting the infrared light reducing means into the optical path according to the emission intensity of the infrared light by the illumination means And a control step of comparing the illuminance detection result with the corrected threshold value and inserting the infrared light reducing means into the optical path according to the comparison result. It is characterized by.

The control program according to the present invention includes an imaging device that forms an optical image via a photographing optical system and outputs an image signal corresponding to the optical image, and an optical path between the photographing optical system and the imaging device. A control program used in an imaging apparatus having an infrared light reduction unit that reduces the amount of infrared light included in the optical image that reaches the imaging element and an illumination unit that illuminates the subject with infrared light A detection step of detecting a luminance of a subject according to the image signal to obtain an illuminance detection result in a computer included in the imaging apparatus; and the infrared light according to an emission intensity of the infrared light by the illumination unit A correction step for correcting a threshold value when the reduction unit is inserted into the optical path is compared with the illuminance detection result and the corrected threshold value, and the infrared light reduction unit is connected to the optical path according to the comparison result. In Characterized in that to execute a control step of entering.

  According to the present invention, when shooting is performed by irradiating infrared light, the shooting mode can be switched at a desired timing without causing a hunting phenomenon even if the shooting mode is switched.

It is a figure which shows the structure about an example of the imaging device by embodiment of this invention. FIG. 2 is a block diagram illustrating an example of a configuration of a control circuit illustrated in FIG. 1. It is a flowchart for demonstrating the mode determination process for the mode switching operation performed in the camera shown in FIG.

  Hereinafter, an example of an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating the configuration of an example of an imaging apparatus according to an embodiment of the present invention.

  The illustrated imaging apparatus is, for example, a digital camera (hereinafter simply referred to as a camera), and includes a plurality of imaging lenses 1 that are imaging optical systems. A filter switching mechanism 3 is disposed at the subsequent stage of the photographing optical system. The filter switching mechanism 3 includes an infrared cut filter 4 (infrared light reducing means) and a filter unit having a transparent substrate 5. As long as the infrared cut filter 4 can reduce the amount of infrared light that reaches the image sensor 7, the infrared cut filter 4 may completely block the infrared light, or may not block the infrared light completely. A sufficient reduction effect may be obtained when the rate is not less than a predetermined value (for example, not less than 90%).

  The filter unit can be moved in a direction orthogonal (crossing) to the optical axis (that is, the optical path) 2 of the photographing optical system, and the infrared cut filter 4 or the transparent substrate 5 is selectively selected according to the movement of the filter unit. Positioned on the optical axis 2. That is, the infrared cut filter 4 or the transparent substrate 5 can be selectively inserted into or removed from the optical axis 2 by driving the infrared cut filter insertion / extraction motor 6 under the control of the control circuit 10 (in other words, The infrared cut filter 4 can be inserted into and removed from the optical path).

  An image pickup device 7 such as a CMOS image sensor is disposed at the subsequent stage of the filter switching mechanism 3, and an optical image (subject image) is formed on the image pickup device 7 through a photographing optical system. The image sensor 7 outputs an image signal corresponding to the optical image to the control circuit 10.

  An infrared illumination unit 11 is connected to the control circuit 10, and the infrared illumination unit 11 uses an LED or the like as a light source to illuminate the subject with infrared light under the control of the control circuit 10. The control circuit 10 controls the entire camera, and the control circuit 10 controls input of power and outputs a video signal corresponding to the image signal.

  At least one of the imaging lens 1 is a zoom lens, and the control circuit 10 drives and controls the zoom motor 12 to move the imaging lens 1 along the optical axis 2 so that the focal length of the imaging lens 1 is telephoto from a wide angle. To change.

  FIG. 2 is a block diagram showing an example of the configuration of the control circuit 10 shown in FIG. In FIG. 2, the filter switching mechanism 3 shown in FIG. 1 is omitted, and only one imaging lens 1 is shown.

  The control circuit 10 includes a camera control circuit 21, an image sensor control circuit 22, a video signal processing circuit 24, an infrared cut filter control circuit 25, a photometry circuit 26, a video signal output circuit 27, an infrared illumination control circuit 28, and a zoom motor. A control circuit 29 is provided.

  At the time of shooting, the optical image incident from the imaging lens 1 passes through the IR cut filter 4 or the transparent substrate 5 and forms an image on the imaging element 7. The image sensor control circuit 22 controls the reading of the image sensor 7 and outputs an image signal corresponding to the optical image from the image sensor 7. Then, the image sensor control circuit 22 sends the image signal to the photometry circuit 26 and the video signal processing circuit 24.

  The video signal processing circuit 24 performs predetermined signal processing on the image signal to generate a color or monochrome video signal. This video signal is output to the outside by the video signal output circuit 27.

  The photometry circuit 26 measures the illuminance (that is, luminance) of the subject according to the image signal and sends the illuminance detection result to the camera control circuit 21. The camera control circuit 21 controls the IR cut filter control circuit 25 and the infrared illumination control circuit 28 according to the illuminance detection result.

  Accordingly, the IR cut filter control circuit 25 and the infrared illumination control circuit 28 drive and control the infrared cut filter insertion / extraction motor 6 and the infrared illumination unit 11, respectively.

  The camera control circuit 21 drives and controls the zoom motor 12 by the zoom motor control circuit 29, moves the imaging lens 1 along the optical axis 2, and changes the focal length of the imaging lens 1 from wide angle to telephoto. .

  FIG. 3 is a flowchart for explaining mode determination processing for mode switching operation performed in the camera shown in FIG. The process according to the illustrated flowchart is performed under the control of the camera control circuit 21, and is automatically and repeatedly executed, for example, when the camera is turned on.

  When the mode determination process is started, the camera control circuit 21 obtains an illuminance detection result (subject illuminance Y1) from the photometry circuit 26 (step S301). Subsequently, the camera control circuit 21 determines whether or not the current shooting mode is the day mode (that is, the color shooting mode) (step S302).

When the shooting mode is the day mode (YES in step S302), the camera control circuit 21 compares the subject illumination Y1 with the first switching threshold TH _DN set in advance, and subject illumination according to the comparison result. It is determined whether or not Y1 <first switching threshold TH _DN (step S303).

The first switching threshold TH _DN is a threshold for switching the shooting mode from the day mode to the night mode.

If the subject illumination Y1 <the first switching threshold TH _DN (the subject illumination Y1 is less than the first switching threshold) (YES in step S303), the camera control circuit 21 changes the shooting mode from the day mode to the night mode (that is, Switch to monochrome photography mode (step S304). In accordance with switching from the day mode to the night mode, the camera control circuit 21 controls the IR cut filter control circuit 25 to remove the infrared cut filter 4 from the optical axis 2.

  Subsequently, the camera control circuit 21 obtains the illuminance detection result as the subject illuminance Y2 from the photometry circuit 26 (step S305). As described above, since the infrared cut filter is removed in the night mode to increase the sensitivity, the subject illuminance in the night mode is set to Y2. Note that subject illumination Y2 may be greater than or equal to subject illumination Y1 under a shooting environment including infrared light.

  Next, since the camera control circuit 21 illuminates the subject with infrared light, the infrared illumination control circuit 28 turns on the infrared illumination unit 11 (step S306). Then, the camera control circuit 21 obtains the light emission intensity in the infrared illumination unit 11 from the infrared illumination control circuit 28 as P1 (step S307).

  Subsequently, the camera control circuit 21 obtains the illuminance detection result from the photometry circuit 26 as the subject illuminance Y3 (step S308). Here, since the subject is illuminated with infrared, the subject illuminance under infrared illumination is Y3. Under infrared illumination, the subject illuminance Y3 is generally greater than or equal to the subject illuminance Y2.

  Thereafter, the camera control circuit 21 takes the difference between the subject illuminance Y2 and the subject illuminance Y3, and sets the difference as the subject illuminance Yup, which is an increase due to the infrared illumination (step S309).

Subsequently, the camera control circuit 21 obtains a second switching threshold TH _ND1 used when switching from the night mode to the day mode based on the subject illuminance Y2 (step S310). Then, the camera control circuit 21 ends the mode determination process.

The second switching threshold TH _ND1 is calculated as, for example, TH _ND1 = Y2 + α. The variable α is a hysteresis for preventing hunting when switching the photographing mode. If the variable α is set large, hunting can be better prevented. On the other hand, if the variable α is set small, switching from the night mode to the day mode can be performed more quickly.

If the subject illumination Y1 ≧ the first switching threshold TH _DN (the subject illumination Y1 is equal to or greater than the first switching threshold) (NO in step S303), the camera control circuit 21 ends the mode determination process.

  If the shooting mode is not the day mode (NO in step S302), that is, if the shooting mode is the night mode, the camera control circuit 21 sets the emission intensity in the infrared illumination unit 11 from the infrared illumination control circuit 28 to P2. Obtain (step S311).

  If there is a change in the light emission intensity in the infrared illumination unit 11 since the switching to the night mode, the light emission intensity P2 is different from the light emission intensity P1. On the other hand, if there is no change in the emission intensity in the infrared illumination unit 11 since the switching to the night mode, the emission intensity P2 is equal to the emission intensity P1.

Subsequently, the camera control circuit 21 corrects the second switching threshold value TH _ND1 obtained in step S310, and sets the corrected threshold value as the third switching threshold value TH _ND2 (step S312). Here, the camera control circuit 21 corrects the second switching threshold value by adding an increase value (correction value) of subject illuminance due to infrared illumination. In this case, the correction value increases as the emission intensity by the infrared illumination unit 11 increases, and decreases as the emission intensity decreases.

When the light emission intensity P2 is zero (light-off state), the correction value is zero, and when the light emission intensity P2 is equal to the light emission intensity P1, the correction value is equal to the subject illuminance Yup that is an increase. Therefore, the third switching threshold TH _ND2 is obtained by, for example, TH _ND2 = TH _ND1 + (Yup × P2 / P1). Note that P2 / P1 indicates the rate of change in emission intensity.

  Note that the camera control circuit 21 may perform correction based on a correction data table recorded in advance in a built-in memory or the like. In this correction data table, for example, correction values for correction are defined in accordance with the relationship between subject illuminance and light emission intensity.

  Furthermore, the increase in subject illuminance due to infrared illumination also changes due to the distance to the subject, the temperature of the infrared illumination unit 11, and the aging of the infrared illumination unit 11 (that is, aging). By doing so, correction can be performed more accurately.

Subsequently, the camera control circuit 21 by comparing the object illuminance Y1 and third switching threshold _{TH ND2,} determines whether the illuminance of the subject Y1> third switching threshold _{TH ND2} (step S313). If subject illumination Y1> third switching threshold TH _ND2 (YES in step S313), camera control circuit 21 turns off infrared illumination unit 11 by infrared illumination control circuit 28 (step S314). That is, the camera control circuit 21 stops the illumination by the infrared illumination unit 11.

  Thereafter, the camera control circuit 21 switches the shooting mode from the night mode to the day mode (step S315). At this time, the camera control circuit 21 controls the IR cut filter control circuit 25 to insert the infrared cut filter 4 onto the optical axis 2 in accordance with the switching from the night mode to the day mode. Then, the camera control circuit 21 ends the mode determination process.

When subject illumination Y1 ≦ third switching threshold TH _ND2 (NO in step S313), camera control circuit 21 ends the mode determination process.

  As described above, in the embodiment of the present invention, the second switching threshold value for switching from the night mode to the day mode is corrected according to the light emission intensity of the infrared illumination unit 11, and therefore the change in the light emission intensity. It is possible to prevent the shooting mode from being switched inadvertently due to the influence of the above.

  In the above description, in step S312, the second switching threshold for switching from the night mode to the day mode is corrected by adding the increase in subject illuminance due to infrared illumination. You may make it correct | amend by subtracting the raise of the object illumination intensity by infrared illumination.

  As is apparent from the above description, in the example shown in FIGS. 1 and 2, the photometry circuit 26 functions as detection means, and the camera control circuit 21 functions as correction means. The camera control circuit 21 and the infrared cut filter insertion / extraction motor 6 function as control means.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also included in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 1 Imaging lens 3 Filter switching mechanism 4 Infrared cut filter 5 Transparent substrate 6 Infrared cut filter insertion / extraction motor 7 Imaging element 10 Control circuit 11 Infrared illumination part 12 Zoom motor 21 Camera control circuit

Claims (12)

An image pickup apparatus having an image pickup element that forms an optical image through a photographing optical system and outputs an image signal corresponding to the optical image,
Infrared light reducing means for reducing the amount of infrared light included in the optical image that is inserted in an optical path between the imaging optical system and the image sensor and reaches the image sensor;
Detection means for detecting the luminance of the subject according to the image signal and obtaining an illuminance detection result;
Illumination means for illuminating the subject with infrared light;
Correction means for correcting a threshold when the infrared light reduction means is inserted into the optical path according to the emission intensity of infrared light by the illumination means;
Control means for comparing the illuminance detection result with the corrected threshold value, and inserting the infrared light reduction means into the optical path according to the comparison result;
An imaging device comprising:   The imaging apparatus according to claim 1, wherein the correction unit performs correction so that the threshold value increases as the light emission intensity increases. The correction means, instead of correcting the threshold value, the illuminance detection result obtained from the detection means in a state where the infrared light reduction means is removed from the optical path between the imaging optical system and the image sensor. To correct
2. The control unit according to claim 1, wherein the control unit compares the corrected illuminance detection result with the threshold value, and inserts the infrared light reduction unit into the optical path according to the comparison result. Imaging device.   The imaging apparatus according to claim 3, wherein the correction unit performs correction so that the illuminance detection result decreases as the emission intensity increases.   5. The imaging according to claim 1, wherein the correction unit obtains a correction value for correction based on a change rate of the emission intensity and an increase in the illuminance detection result. apparatus.   The correction means obtains a correction value for correction by a correction data table in which a correction value for correction is defined in accordance with a relationship between the illuminance detection result and the light emission intensity. The imaging device according to any one of 1 to 4.   The correction unit performs the correction in consideration of at least one of a distance from the imaging device to a subject, a temperature of the illumination unit, and a secular change of the illumination unit. The imaging device according to any one of the above.   The control means switches the photographing mode to a color photographing mode when the infrared light reducing means is inserted into the optical path, and switches the photographing mode to a monochrome photographing mode when the infrared light reducing means is removed from the optical path. The imaging apparatus according to claim 1, wherein the imaging apparatus is characterized.   The imaging apparatus according to claim 8, wherein the control unit performs illumination by the illumination unit in the monochrome photographing mode.   The control means stops illumination by the illuminating means when the illuminance detection result is larger than the corrected threshold value, and switches the photographing mode from the monochrome photographing mode to the color photographing mode. Item 10. The imaging device according to Item 8 or 9. An optical image is formed through the photographing optical system, and an image sensor that outputs an image signal corresponding to the optical image is inserted into an optical path between the photographing optical system and the image sensor to reach the image sensor. An imaging apparatus control method comprising: infrared light reduction means for reducing the amount of infrared light contained in the optical image; and illumination means for illuminating a subject with infrared light,
A detection step of detecting a luminance of a subject according to the image signal and obtaining an illuminance detection result;
A correction step of correcting a threshold when the infrared light reducing means is inserted into the optical path according to the emission intensity of infrared light by the illumination means;
A control step of comparing the illuminance detection result with the corrected threshold value and inserting the infrared light reducing means into the optical path according to the comparison result;
A control method characterized by comprising: An optical image is formed through the photographing optical system, and an image sensor that outputs an image signal corresponding to the optical image is inserted into an optical path between the photographing optical system and the image sensor to reach the image sensor. A control program used in an imaging apparatus having infrared light reducing means for reducing the amount of infrared light contained in the optical image and illumination means for illuminating a subject with infrared light,
In the computer provided in the imaging device,
A detection step of detecting a luminance of a subject according to the image signal and obtaining an illuminance detection result;
A correction step of correcting a threshold when the infrared light reducing means is inserted into the optical path according to the emission intensity of infrared light by the illumination means;
A control step of comparing the illuminance detection result with the corrected threshold value and inserting the infrared light reducing means into the optical path according to the comparison result;
A control program characterized by causing

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