JP2014011635A - Image pickup device and control method and program thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of times an IRCF is removed and inserted unnecessarily, and to thereby increase durability.SOLUTION: An image pickup device has an auto day-night function and is able to set the maximum value of gain in the gain control means of image pickup means, in which a changeover evaluation value is calculated on the basis of output from the image pickup means, and auto day-night switching is determined on the basis of the result of comparison between the changeover evaluation value and a changeover threshold value for changing image data output to either color or monochrome. The changeover evaluation value is stored in memory as a learning value, and the learned value and the current changeover evaluation value are compared to determine whether the learned value and the current changeover evaluation value are within a prescribed range. The learned value is altered when the maximum gain value is altered.

Description

  The present invention relates to an automatic day / night function of an imaging apparatus.

  The color vision characteristic, which is a sensitivity characteristic for human colors, and the relative visual sensitivity characteristic, which is a sensitivity characteristic for brightness, have a sensitivity of 380 nm to 780 nm, which is referred to as a visible range. On the other hand, these characteristics have little sensitivity in a wavelength region longer than 700 nm. Therefore, in general, an imaging apparatus includes an infrared light removal filter (IRCF) for correcting visibility that does not allow light in the near infrared region to pass through in front of the imaging device in order to match color reproducibility with human color vision characteristics. ing.

  However, under low illuminance where the subject brightness decreases, the imaging apparatus often removes the IRCF from the optical path, thereby allowing light in the near-infrared region to pass and increasing sensitivity. However, since the color balance is lost when light in the near-infrared region passes, the imaging apparatus needs to switch the shooting mode from a color image (day mode) to a black and white image (night mode). As one of the switching methods, there is a function called auto day / night (hereinafter, ADN) in which the imaging apparatus automatically switches between the day mode and the night mode.

  The threshold value of the subject brightness when switching from the day mode to the night mode is determined based on AE data (shutter speed, aperture value, gain, screen brightness * luminance drop) of the camera.

  In recent years, an imaging apparatus has appeared that has a function of limiting a gain value of an AGC (gain control amplifier circuit), that is, setting a maximum gain value. This function has been increasingly demanded by users in recent years. By using this function, the imaging apparatus can capture beautiful scenes such as night scenes where there are many black surfaces.

  For example, the imaging apparatus described in Patent Document 1 switches the mode by inserting / removing an IRCF according to a determination result from at least one output of the imaging unit and the brightness detection unit.

  In addition, the imaging device described in Patent Document 2 sets a reference light amount serving as a reference for switching from the night mode to the day mode based on the incident light amount when switching from the day mode to the night mode.

JP 2010-279061 A JP 2004-120202 A

  However, the imaging device of Patent Document 1 has a configuration in which the maximum gain value cannot be set. On the other hand, an imaging apparatus having a function of setting a maximum gain value does not appropriately set a determination reference value in accordance with a change in output due to the setting of the maximum gain value. Will go. Moreover, in patent document 2, it is a structure without a learning value. For this reason, if a temporary disturbance such as a car headlight occurs during the calculation of the reference light amount, an appropriate evaluation value is not calculated, and there is a problem that the mode is not switched at a desired brightness. .

  The present invention has been made in view of the above-described problems. Even when the maximum gain value is set, IRCF insertion / extraction is minimized with a simple configuration.

  In order to solve the above-described problems, an imaging apparatus according to the present invention includes an imaging unit including a gain control unit that amplifies a signal from an imaging element, and image data that generates image data of a subject image captured by the imaging unit. Generating means, switching means for switching the output of the image data generated by the image data generating means to either color or black and white, maximum gain setting means for setting a maximum value of the gain of the gain control means, and Switching evaluation value calculating means for calculating a switching evaluation value based on an output from the imaging means, and based on a comparison result of a switching threshold value for switching the switching evaluation value and the output of the image data to either color or monochrome. Determination means for determining switching of image data output by the switching means, learning value storage means for storing the switching evaluation value as a learning value, and learning value storage means. Learning value determination means for comparing the learning value with the current switching evaluation value to determine whether the learning value and the current switching evaluation value are within a predetermined range; and the maximum gain value is changed. And a change means for changing the learning value.

  According to the present invention, in an imaging apparatus that matches a threshold value at the time of IRCF insertion multiple times for the purpose of preventing a reference light amount calculation error when disturbance occurs, an appropriate value is obtained even when the maximum gain value is changed. By doing so, the number of unnecessary IRCF insertions / removals can be reduced to increase durability.

It is a figure which shows the structure of the camera which concerns on 1st Embodiment. It is a figure which shows the structure of the imaging part of the camera which concerns on 1st Embodiment. It is a flowchart which shows the process of the camera which concerns on 1st Embodiment. It is a figure which shows an example of a to-be-photographed object. It is a figure in which the maximum gain value is set high. It is a figure in which the maximum gain value is set to be low. It is a flowchart which shows the process of the camera which concerns on 1st Embodiment. It is a figure which shows the structure of the camera which concerns on 2nd Embodiment. It is a flowchart which shows the process of the camera which concerns on 2nd Embodiment. It is a table | surface which shows the example of the offset value corresponding to each maximum gain value which concerns on 2nd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Below, the case where a camera is used as an imaging device is demonstrated.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration of a camera according to the first embodiment. The camera includes an image data generation unit 101 that takes in light from the outside and generates image data. The image data generation unit 101 includes an imaging unit (imaging unit) 102 and an image signal processing unit 103 that performs predetermined processing on a signal captured from the imaging unit 102.

  A shooting mode switching unit 104 that switches image data to day mode (color) or night mode (black and white), and a switching evaluation value calculation unit 105 that calculates a reference light amount for switching the mode from the output from the imaging unit 102 as an evaluation value. Is provided. Furthermore, a maximum gain setting unit 107 that can set the maximum value of the gain by a user operation or the like is provided. Similarly, a switching threshold value setting unit 108 that can set a switching threshold value for performing day / night mode switching at a desired brightness by a user operation is provided. A shooting mode determination unit 106 that determines switching of image data output by the shooting mode switching unit 104 based on a comparison result of a switching threshold value for switching the switching evaluation value and the output of image data to either the day mode or the night mode. . A learning value storage unit 109 is provided for acquiring and storing a switching evaluation value after switching when the shooting mode determination unit 106 determines to switch to the night mode.

  The display unit 110 is configured as a display unit that displays the image data output from the shooting mode switching unit 104 based on the comparison result between the switching evaluation value and the switching threshold value.

  Here, FIG. 2 is a diagram illustrating a detailed configuration of the imaging unit (imaging unit) 102.

  The imaging unit 102 includes a lens 201 made up of several lens groups, an infrared light removal filter (Infrared Ray Cut Filter: IRCF) 202, a CCD, An image sensor 203 such as a CMOS is provided. In addition, the imaging unit 102 includes a correlated double sampling (CDS) circuit 204 that performs noise reduction. The imaging unit 102 also includes a gain control amplifier circuit (Automatic Gain Control: AGC) 205 that automatically controls the gain of the camera.

  The imaging unit 102 includes an A / D converter 206 that converts an analog signal into a digital signal.

  The operation of each component described above will be described in detail.

  First, the image data generation unit 101 will be described in detail with reference to FIGS. 1 and 2. The image sensor 203 converts a subject image formed through the lens 201 and the IRCF 202 as an imaging optical system into an electric signal. The CDS circuit 204 performs correlated double sampling processing on the electrical signal output from the image sensor 203. The AGC amplifier 205 performs amplification processing on the electrical signal output from the CDS circuit 204. The A / D converter 206 converts the analog signal amplified by the AGC amplifier 205 into a digital signal.

  The image signal processing unit 103 includes, for example, digital signal processing (DSP) and the like. The image signal processing unit 103 performs predetermined conversion such as color conversion, AE processing, WB processing, and gamma processing that performs tone conversion of a signal-processed image on a digital signal. Perform image processing.

  The image data output from the image data generation unit 101 is input to the shooting mode switching unit 104, converted into a monochrome image or a color image, and output. Here, although the photographing mode switching unit 104 is displayed independently, the image signal processing unit 103 may be included.

  In order to switch between monochrome and color images, the switching evaluation value calculation unit 105 calculates the switching evaluation value from the imaging conditions such as aperture, shutter speed, and gain output from the imaging unit 102.

  On the other hand, the maximum gain value can be set in the maximum gain setting unit 107 that can set the maximum value of the gain. In addition, the higher the maximum gain, the higher the sensitivity, and the higher the sensitivity, the more the image can be taken. However, there is a deterioration due to image noise, sharpness, and other components. . For example, this setting may be disclosed to the outside, and the user may arbitrarily select or switch automatically depending on the internal state of the camera.

  Then, the determination unit 106 inputs the switching evaluation value output from the switching evaluation value calculation unit 105 and the switching threshold value output from the switching threshold value setting unit 108, and outputs the image in the day mode by the shooting mode switching unit 104. Or whether to output in night mode. For example, if the switching evaluation value is less than or equal to the switching threshold, the image is output in the night mode.

  2 is provided, and when it is determined that the switching unit 104 outputs in the night mode, the determination unit 106 outputs a signal to an IRCF drive unit (not shown). Thereafter, the IRCF driving unit removes the IRCF 202 from the optical path of the imaging optical system, thereby taking in an infrared component and increasing the luminance.

  Further, when the determination unit 106 determines to output in the night mode, the switching evaluation value considering the luminance increase of the infrared component is stored in the learning value storage unit 109 as a learning value.

  The image display unit 109 is composed of, for example, an LCD and displays the image data output from the switching unit 104.

  Next, an operation process until the learning value is stored when the shooting mode of the camera is switched from the day mode to the night mode will be described using the flowchart shown in FIG.

  When the shooting mode is the day mode, the image data is output in color. Here, the image data generation unit 101, the shooting mode switching unit 104, the switching evaluation value calculation unit 105, the shooting mode determination unit 106, the switching threshold setting unit 108, and the learning value storage unit 109 operate mainly to perform the processing shown in the flowchart. Is realized.

  First, in step s301, it is determined from the image data output from the image data generation unit 101 whether the current day / night mode is the day mode or the night mode. First, the case of the day mode will be described below.

  In step s302, it is determined whether or not the current switching evaluation value calculated by the switching evaluation value calculation unit 105 is equal to or less than the switching threshold set by the switching threshold setting unit 108. The switching evaluation value is calculated by the switching evaluation value calculation unit 105 based on the imaging conditions output from the imaging unit 102 in the image data generation unit 101, that is, the aperture value, shutter speed, and AGC gain value.

Below, an example of the calculation method of a switching evaluation value is shown.
S = iris + shutter + AGCgain
Here, S represents a switching evaluation value. Further, iris, shutter, and AGCgain are an aperture value, a shutter speed, and an AGC gain value, respectively. Moreover, each value is shown below.

  The switching evaluation value S is a value indicating exposure brightness, that is, an EV value. The EV value is obtained by logarithmically adding each of the aperture value (F value), shutter speed (seconds), and AGC gain value (dB). The switching evaluation value is always calculated from the current shooting conditions when the day / night function mode is auto.

  The shooting mode determination unit 106 compares the current switching evaluation value with the switching threshold value. If the switching evaluation value is equal to or less than the switching threshold value, the IRCF is removed from the optical path and switched to the night mode once (step s303). .

  In step s304, the switching evaluation value after IRCF removal is acquired, and the learning value stored in advance (the switching evaluation value calculated by a series of flows when changing from the previous day mode to the night mode. For details, see step s304. If the result of comparing the current switching evaluation value and the current switching evaluation value is within a predetermined range, there is almost no change in the subject due to only a change in brightness over time in the shooting environment at the time of storing the learning value. The night mode is continued until the switching evaluation value becomes equal to or higher than the switching threshold (IRCF removal is terminated once).

  In step s305, if the result of comparing the switching evaluation value and the learning value in step s304 is outside the predetermined range, the switching evaluation value at that time is temporarily stored.

  In step s306, the IRCF is again inserted into the optical path to enter the day mode, and then the switching evaluation value is calculated again.

  In step s307, it is determined whether or not the current switching evaluation value is equal to or lower than the switching threshold. If the switching evaluation value is equal to or higher than the switching threshold, it is determined that a disturbance has occurred during the previous switching evaluation value calculation, and the switching evaluation value is switched next. The day mode is continued until the threshold value is reached. In this case, the process starts from step s304.

  In step s308, when it is determined in step s307 that the switching evaluation value is two times lower than the switching threshold value (two times in combination with step s304), the IRCF is removed from the optical path to enter the night mode.

  In step s309, the switching evaluation value calculated after IRCF removal in step s308 is stored as a learning value. The learning value here is referred to in step s304 when the day mode is switched to the night mode.

  Up to this point, the switching evaluation value has finally shifted from the day mode to the night mode by being twice below the switching threshold value. It should be noted that the above-described multiple switching determination method is commonly used.

  Next, the case of the night mode will be described first.

  In step s310, when the day / night mode is the night mode, it is determined whether or not the current switching evaluation value is greater than or equal to the switching threshold. The switching threshold value here may be a switching threshold value that takes into account the brightness increase when switching from the day mode to the night mode, or may be set in advance by the user.

  In step s311, when the switching evaluation value becomes equal to or greater than the switching threshold value in step s310, the IRCF is inserted on the optical path to shift to the day mode, and then the day mode is continued until the switching evaluation value becomes equal to or less than the switching threshold value.

  Here, an example of a captured image of the camera in the present embodiment will be described with reference to FIGS.

  First, an example when time passes in a place where a subject can be photographed as shown in FIG. FIG. 5 shows a case where the maximum gain setting value (maximum gain value) is set to an initial value or a higher value in the maximum gain setting unit 107. In FIG. 5, an appropriate gain is added depending on the subject brightness. Here, when the maximum gain value is set to the initial value, the calculated switching evaluation value is assumed initially. On the other hand, when the maximum gain value is set higher than the initial value, the gain is higher than the initially set maximum gain value.

  In the present embodiment, the maximum gain value is arbitrarily set by the user. However, the maximum gain value may be set automatically depending on the shooting situation, the subject, and the like.

  When the subject brightness is dark, the day mode of the image data is larger when the maximum gain value set by the maximum gain setting unit 107 is larger than when the maximum gain value set by the maximum gain setting unit 107 is smaller. The time (color output) will be maintained for a long time.

  On the other hand, FIG. 6 shows a case where the maximum gain value is set lower in the maximum gain setting unit 107. Therefore, the actual subject brightness is brighter when the brightness of the display image is the same as when the maximum gain is set higher. Therefore, the imaging condition inside the camera shows a bright value. As a result, the switching evaluation value calculated by the switching evaluation value calculation unit is relatively low.

  In addition, even when the subject is the same brightness and subject, the switching evaluation value calculated after the maximum gain value is changed is different. Therefore, the comparison result between the learning value and the switching evaluation value obtained in the flowchart of FIG. It is not within the prescribed range. Therefore, the learning value becomes invalid.

  Therefore, when the learning value is stored in advance, the learning value is initialized (predetermined in advance) when the maximum gain value is changed (step s402) in the automatic day / night mode in step s401 as shown in FIG. The initial value is set to the initial value), the possibility of being effective as a learning value increases.

  Similarly, when the maximum gain value is changed, if the switching evaluation value is compared with a predetermined switching threshold value, it may not be switched at the desired brightness. The switching threshold value may be changed to an appropriate value. The above-described switching threshold may be arbitrarily determined by the user, or the luminance change when the maximum gain value is changed may be offset.

(Second Embodiment)
Next, a second embodiment will be described.

  FIG. 8 is a diagram illustrating a configuration of a camera according to the second embodiment. In the present embodiment, description will be made mainly on the configuration added from the configuration of the first embodiment, and the same configuration as that of the first embodiment will be denoted by the same reference numeral, and the description thereof will be omitted.

  The camera in FIG. 8 includes a learning value correction unit 111 that corrects a learning value stored in advance. The learning value correction unit 111 receives and corrects a learning value stored in advance when the maximum gain value is changed. As a correction method, as shown in FIG. 9, an offset value is determined in advance using a table or the like according to the maximum gain value, and an offset value corresponding to the changed maximum gain value is added to or subtracted from the learning value. The offset value can be arbitrarily determined, and the learning value may be increased or decreased based on an evaluation function or the like instead of a table.

  Next, the flow until the learning value is offset will be described using the flowchart shown in FIG. It is assumed that the learning value is stored in advance through steps s301 to s311 in FIG. In step s501, it is determined whether the day / night mode is auto day / night. In manual mode, nothing is done because the learning value is not valid.

  In step s502, after it is determined in step 501 that it is auto day / night, it is determined whether or not the maximum profit value in which the current learning value is stored has been changed.

  In step s503, if it is determined in step s502 that the maximum gain value has been changed, an offset value corresponding to the maximum gain value is acquired from the table of FIG. Here, assuming that the maximum gain value is changed from the initial value to the high value, and assuming that the amount of change of the maximum gain value at that time is +6.0 dB, the offset value is +1.0 EV.

  In step s504, the offset value acquired in step s503 is added to or subtracted from the learning value.

  By performing the above-described processing, the learning value can be made effective for the problem that the switching evaluation value changes with the same brightness and with the same subject when the maximum gain value is changed. As a result, even when the maximum gain value is changed, once the learning value is stored, IRCF insertion / removal can be completed at one time as long as the shooting environment does not change significantly, so durability can be improved. is there.

  As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention. For example, in the above-described embodiment, the camera described as the imaging device can be applied to a digital still camera or a digital video camera. Further, the blocks other than the image data generation unit do not necessarily have to be provided in the camera, and may be provided by another device. For example, a system configuration in which a client terminal (for example, a personal computer, a tablet, or the like) connected to the camera via a network includes the determination unit 106 and the like so that the camera can be remotely controlled.

  In the first and second embodiments, the image signal processing unit 103, the shooting mode switching unit 104, the switching evaluation value calculation unit 105, the shooting mode determination unit 106, the maximum gain setting unit 107, the switching threshold setting unit 108, learning The value correction unit 111 and the like may be realized by the CPU executing a program.

  That is, each unit constituting the imaging apparatus and each step of the imaging apparatus control method according to the present embodiment can be realized by operating a program stored in a memory of a computer or the like. This program and a computer-readable recording medium on which this program is recorded are included in the present invention.

  Further, the present invention can be embodied as a system, apparatus, method, program, recording medium, or the like, and may be applied to a system including a plurality of apparatuses.

  In the present invention, a program for realizing the functions of the above-described embodiments may be directly or remotely supplied to an apparatus or a system. That is, a case where the present invention is achieved by reading and executing a supplied program by a computer of the system or apparatus is also included.

DESCRIPTION OF SYMBOLS 101 Image data generation part 102 Imaging part 103 Image signal processing part 104 Shooting mode switching part 105 Switching evaluation value calculation part 106 Shooting mode determination part 107 Maximum gain setting part 108 Switching threshold value setting part 109 Learning value memory | storage part 110 Display part 111 Learning value Correction unit

Claims (5)

Imaging means including gain control means for amplifying a signal from the imaging element;
Image data generating means for generating image data of a subject image imaged by the imaging means;
Switching means for switching the output of the image data generated by the image data generating means to either color or black and white;
Maximum gain setting means for setting a maximum value of the gain of the gain control means;
Switching evaluation value calculating means for calculating a switching evaluation value based on an output from the imaging means;
A determination unit for determining switching of the output of the image data by the switching unit based on a comparison result of a switching threshold value for switching the switching evaluation value and the output of the image data to either color or black and white;
Learning value storage means for storing the switching evaluation value as a learning value;
Learning value determination means for comparing the learning value stored in the learning value storage means with a current switching evaluation value to determine whether the learning value and the current switching evaluation value are within a predetermined range;
An imaging apparatus comprising: a changing unit that changes the learning value when the maximum gain value is changed.   The imaging apparatus according to claim 1, wherein the changing unit changes the learning value to an initial value. An image data generation step for generating image data of a subject image imaged by an imaging means including a gain control means for amplifying a signal from the imaging element;
Switching the output of the image data generated by the image data generation step to either color or black and white;
Setting a maximum value of gain of the gain control means;
Calculating a switching evaluation value based on an output from the imaging means;
Determining switching of image data output by the switching means based on a comparison result of a switching threshold value for switching the switching evaluation value and the output of the image data to either color or black and white;
Storing the switching evaluation value as a learning value;
Comparing the learning value stored in the learning value storage means with the current switching evaluation value to determine whether the learning value and the current switching evaluation value are within a predetermined range;
And a changing step of changing the learning value when the maximum gain value is changed.   The method according to claim 1, wherein the changing step changes the learning value to an initial value.   The program for performing the control method of the imaging device of Claim 3 or 4.