JP2014225828A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device which prevents an out-of-focus image to be provided when a day mode is switched to a night mode.SOLUTION: An image pickup device comprises a photographing optical system 1, focus means 1, 14 for adjusting a point of focus, an image pickup element 3 for converting a subject image to electric signals, a calculation part 11 of a luminance value of an image, filter means 2, insertion/removal means 13 and control means 12 for controlling the focus means and the insertion/removal means. The filter means prevents light of a wavelength within a predetermined range from the photographing optical system from passing the image pickup element. The insertion/removal means inserts or removes the filter means with respect to an optical path. The control means compares a luminance output result form the luminance value calculation part in a state where the filter means is inserted into the optical path with a luminance output result from the luminance value calculation part in a state where the filter means is removed from the optical path, and determines depending on a luminance difference, whether to perform correction of adjustment of the point of focus corresponding to a component of the light of the wavelength within the predetermined range.

Description

The present invention relates to an imaging apparatus. In particular, the present invention relates to an imaging apparatus such as an infrared / visible common camera that performs imaging by inserting / removing filter means such as an infrared light removal filter (hereinafter referred to as IRCF).

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, are sensitivity characteristics from 380 nm to 780 nm, the sensitivity of which is called the visible region, and almost no sensitivity in the wavelength region longer than 700 nm. I don't have it. Therefore, in order to match the color reproducibility of the image pickup device with human color vision characteristics, a visual sensitivity correction IRCF that does not allow light in the near infrared region to pass may be provided in front of the image pickup device. However, under low illuminance where the subject brightness decreases, the IRCF is often removed from the optical path, thereby allowing light in the near infrared region to pass and increasing sensitivity. However, if a light beam in the near-infrared region is allowed to pass, the color balance is lost, so the shooting mode may be switched from a color image (day mode) to a monochrome image (night mode). As a switching method, there is also a function called automatic day / night (hereinafter referred to as ADN) for automatically switching between the day mode and the night mode. The subject brightness threshold for switching from a color image to a black and white image is determined based on, for example, the shutter speed of the camera, the aperture value, AGC (automatic gain adjustment), screen brightness, and the like.

Patent Document 1 discloses a switching method in which the brightness of a subject is determined based on the luminance level of a video signal, and an infrared cut filter is inserted and extracted according to the determination result to switch modes. Patent Document 2 discloses that the optical path length associated with IRCF insertion / extraction is compensated by focus driving, and the focus position is maintained.

JP 2002-016838 A Patent No. 04190346

However, in the related art disclosed in Patent Document 1 described above, when the focus is in the manual focus mode and the mode is switched from the day mode to the night mode, the light source may be out of focus. In particular, in recent years, with the improvement of image quality, the demand for shooting in IRCF night mode using infrared illumination is increasing, and what was in focus in day mode has become out of focus when in night mode. May end up. This is because the focal position of the lens shifts depending on the wavelength of light. Accordingly, an object of the present invention is to provide a technique for realizing an appropriate focus position when the day mode is changed to the night mode.

In order to achieve the above object, an imaging apparatus according to the present invention uses an imaging optical system, focusing means for adjusting a focus position of the imaging optical system, and an object image formed by the imaging optical system as an electrical signal. An image sensor for conversion, a luminance value calculation unit for acquiring the luminance of an image from an electrical signal of the image sensor, and a filter unit for preventing light of a predetermined range of wavelengths from the imaging optical system from passing through the image sensor. An insertion / extraction means for inserting / extracting the filter means with respect to the optical path of the photographing optical system; and a control means for controlling the focusing means and the insertion / extraction means. And the said control means memorize | stores the output result of the said luminance value calculation part in the state which put the said filter means with respect to the optical path of the said imaging optical system as a 1st brightness | luminance output result, The said 1st brightness | luminance output result And the second luminance output result from the luminance value calculation unit in a state where the filter means is omitted, and from the luminance difference between the first luminance output result and the second luminance output result, the predetermined luminance It has a function of determining whether or not to perform focus position adjustment correction corresponding to a light component having a wavelength in the range.

According to the present invention, even when the focus is adjusted with the filter means such as the IRCF, even when shooting with infrared illumination or the like when the filter means is removed, a good focus position is realized. become able to.

The block diagram of Example 1 of this invention. FIG. 3 is a diagram illustrating a wavelength of light and a focus position in the first embodiment. The figure which showed the change of the brightness | luminance of the infrared illumination with and without IRCF in Example 1. FIG. 2 is a flowchart of processing according to the first embodiment. Explanatory drawing of Example 2 of this invention. 10 is a flowchart of processing according to the second embodiment. 10 is a flowchart of processing according to the third embodiment.

In the present invention, the filter means blocks the luminance difference between the first luminance output result with the filter means inserted in the optical path of the photographing optical system and the second luminance output result with the filter means removed. It is determined whether or not to perform focus position adjustment correction corresponding to a light component having a wavelength in a predetermined range. The filter means is typically an infrared light removal filter that blocks wavelength components of near infrared or higher, but filter means that blocks other wavelength components can also be used. In the present invention, according to the combination of the type of filter means and the type of illumination light, the focus position is calculated from the luminance difference between the luminance output result with the filter means inserted and the luminance output result with the filter means removed. Decide how to determine whether or not to perform adjustment correction.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
Example 1
FIG. 1 is a configuration diagram of Embodiment 1 of a camera which is an imaging apparatus according to the present invention. In this embodiment, a lens group 1 including a focus lens which is composed of several lenses and can be driven by the lens driving means 14, and an IRCF 2 which can be inserted into and removed from the optical path passing through the lens group 1 by the IRCF driving means 13 are provided. Yes. In the configuration in which the IRCF 2 is inserted / extracted, the optical path length changes when the IRCF 2 is extracted. Therefore, a dummy glass (not shown) is inserted when the IRCF 2 is extracted, so that the optical path length does not change. That is, when the infrared light removal filter as the filter means is removed, the optical path length compensation dummy glass enters the optical path.

In addition, the following elements are provided. Solid-state imaging device 3 such as CCD or CMOS, correlated double-sampling (CDS) circuit 4 for reducing noise, gain control amplifier circuit (Automatic-Gain-Control: AGC) for automatically controlling camera gain ) 5 is provided. Also, an A / D conversion unit 6 that converts an analog signal into a digital signal, an image signal processing unit 7 that performs a predetermined process on the captured image signal, and image data output from the image signal processing unit 7 is used as an external display system. An image signal output unit 8 for output is provided. In addition, an image display unit 9 that displays an image on an output system, an image recording unit 10 that records an image, and a luminance value calculation unit 11 that calculates a luminance value of image data are provided. Furthermore, a control unit 12 is provided that determines the shooting mode based on the luminance value calculated by the luminance value calculation unit 11, controls the insertion / extraction of the IRCF 2 through the driving unit 13, and the focus lens through the driving unit 14.

The operation will be described in detail below. Light from the subject forms an image on the image sensor 3 through the lens group 1 and IRCF 2 as a photographing optical system, and the subject image is converted into an electrical signal and output. A CDS circuit 4 that performs correlated double sampling processing, etc., an AGC amplifier 5 that performs amplification processing, etc., and an A / D converter 6 that converts an analog signal into a digital signal are provided for this electrical signal. The image signal processing unit 7 as image processing means is configured by, for example, Digital-Signal-Processing (DSP). Then, predetermined image processing such as color conversion, AE processing, WB processing, and gamma processing for performing tone conversion of the signal-processed image is performed on the digital signal. Further, the image signal processing unit 7 has a shooting mode switching unit as a shooting mode switching unit, and the image data subjected to the image processing is supplied to the image signal output unit 8 and the luminance value calculation unit 11 as a color image or a monochrome image. Output. The image display unit 9 as an image display unit is configured by an LCD or the like, for example, and displays an image output from the image signal output unit 8.

The image recording unit 10 serving as an image recording unit is composed of an external recording memory such as a hard disk, and records the image output from the image signal output unit 8. The brightness value calculation unit 11 calculates the brightness of the subject of the image data output from the image signal processing unit 7 as the average brightness of the screen. For example, 0 is calculated when there is no light, and 255 is calculated when the entire surface is white. The control unit 12 has a shooting mode determination function execution unit as a shooting mode determination unit, and has a function of holding a luminance value in the day mode when the day mode is changed to the night mode. Then, when the mode is switched to the night mode, the luminance value is read again from the luminance value calculation unit 11 and compared with the luminance value in the day mode described above. The control means 12 determines the focus position of the focus lens of the lens group 1 based on the amount of the luminance difference.

FIG. 2 shows the relationship between the wavelength of light and the focus position in focus. As can be seen from this figure, the focus position changes depending on the wavelength of light. In particular, it can be seen that the focus position shifts at a wavelength of 650 nm or more in the wavelength component region of the near infrared or higher. FIG. 3 shows the spectral characteristics of infrared illumination. The cut frequency of IRCF is 650 nm, and when the IRCF is included, there is no light having a wavelength of 650 nm or more as shown in FIG. On the other hand, when IRCF is removed, light of 650 nm or more enters as shown in FIG. For this reason, it can be seen that the change in the luminance value changes remarkably between when IRCF is included and when it is removed under infrared illumination. For example, reference is made to the luminance value when the infrared light is illuminated toward the imaging device. In the case of FIG. 3B, the luminance value is almost 0, but reacts greatly when IRCF is removed, and the luminance value rises significantly to 100, for example.

In this embodiment, paying attention to this point, if there is a difference between the luminance with IRCF inserted and the luminance with the IRCF removed, it is determined that the wavelength of the infrared component light is included, and is matched to the wavelength of the infrared ray. Correct the focus position.

Next, description will be made with reference to the flowchart of FIG. In S401, it is determined whether or not IRCF has been entered. If so, it is determined in S402 whether the focus is in auto or manual mode. In the manual mode, the luminance value Y1 is read in S403, the focus position is read in S404, and the process is terminated. In this way, the control means stores the output result of the luminance value calculation unit in a state where the filter means is inserted in the optical path of the photographing optical system when the focus position adjustment is in the manual focus mode. As described above, the focus position adjustment is corrected.

If IRCF is not included in S401, the luminance value Y2 is read in S405. Next, in S406, the brightness values Y1 and Y2 are compared. If Y1 and Y2 are the same or Y1 is larger, it is determined that focus correction is not performed, and that correction is not performed in S409, and the process ends. This is because if there is no change in luminance or the day is brighter, it can be determined that the infrared wavelength light is not increased by removing the IRCF, and that there is no effect on the focus position. Next, if Y2 is larger than the luminance value Y1 in 406, it is determined that there is correction in S407, and a predetermined amount of focus drive is performed in S408, and the process ends. In S407, since the luminance is higher when IRCF is lost, it is clear that the wavelength component of the near-infrared or higher wavelength component has increased, so that it can be determined that the focus position changes. For this reason, the focus lens is driven in addition to the correction amount possessed in advance in addition to the focus position when shooting with the IRCF included. As described above, when the second luminance output result is the same as or lower than the first luminance output result, the control unit corrects the focus position adjustment corresponding to the wavelength component of near infrared or higher. Absent. When the second luminance output result is larger, the focus position adjustment corresponding to the wavelength component of near infrared or higher is corrected.

In the present embodiment, depending on the configuration of the IRCF, it may be considered that no dummy glass is contained when the IRCF is pulled out. In this regard, Patent Document 2 discloses that the focus position is maintained by performing focus driving for an optical path length associated with IRCF insertion / extraction. In this regard, the present embodiment can be as follows. In the case of the configuration without the dummy glass when the IRCF is removed, only the correction of the optical path length is performed when the correction of the wavelength component above the near infrared is not necessary. When correction of the wavelength component of near infrared or higher is necessary, correction is performed by combining the correction of the wavelength component of near infrared or higher with the correction of the optical path length. In this case, the control means has an optical path length correction function for correcting a predetermined optical path length when the filter means is removed. If it is determined that the focus position adjustment correction corresponding to the light component of the wavelength in the predetermined range is necessary, the amount obtained by adding the correction amount of the predetermined optical path length and the correction amount of the corresponding focus position adjustment described above to the photographing optical This is performed as a correction of the focus position adjustment by the focus means for adjusting the focus position of the system.

(Example 2)
A second embodiment of the present invention will be described. In this embodiment, when the focus is corrected when the IRCF is removed, when determining whether or not the correction is necessary, an increase in luminance is taken into consideration, and appropriate correction is performed accordingly. .

FIG. 5 shows the spectral characteristics of the incandescent lamp. The cut frequency of IRCF is set to 650 nm. When the IRCF is included, there is no light having a wavelength of 650 nm or more as shown in FIG. On the other hand, when IRCF is removed, light of 650 nm or more enters as shown in FIG. Therefore, it can be seen that the luminance value changes between when the IRCF is inserted and when it is removed under incandescent lighting. For example, assume that you are shooting under an incandescent lamp. In the case of FIG. 5A, the luminance value is indicated as 40. When the IRCF is removed, it reacts somewhat, and the luminance value increases to 50.

In this regard, under incandescent lamps, the wavelength band of light is wide, and the proportion of the wavelength in the visible light region is large. Therefore, if the increment at the time of extraction relative to the insertion is less than or equal to the predetermined value, the visible wavelength has a high contribution to the focus.Therefore, depending on the required focus accuracy and lens characteristics, between the day mode and the night mode. There may be no need for focus correction. In the present embodiment, correction is not performed when the increase in the infrared component when the IRCF is removed is below a predetermined amount.

On the other hand, in the case of infrared illumination as described in the first embodiment, a significant change in luminance occurs and the wavelength is significantly different from that in the case of day (IRCF insertion). Therefore, it is necessary to correct the focus when extracting the IRCF. Become. This embodiment pays attention to this point, and when the difference between the brightness with IRCF inserted and the brightness withdrawn is within a predetermined amount, it is determined that the illumination is an incandescent lamp with a wide wavelength band. Do not make corrections. However, if the amount is greater than or equal to the predetermined amount, similarly to the first embodiment, it is determined that the infrared light is clearly illuminated, and correction is made to the focus position that matches the wavelength of the infrared illumination, for example, 850 nm.

This will be described with reference to the flowchart of FIG. In step S601, it is determined whether or not IRCF is present. If it is present, it is determined in step S602 whether or not the focus is in auto or manual mode. In the manual mode, the luminance value Y1 is read in S603, the focus position is read in S604, and the process ends. If IRCF is not included in S601, the luminance value Y2 is read in S605. Next, in S606, the brightness values Y1 and Y2 are compared. If the result is not larger than the predetermined value, it is determined that focus correction is not performed, and that correction is not performed in S609, and the process ends. Next, when Y2 is larger than the luminance value Y1 by a predetermined value or more at 606, it is determined that there is a correction at S607, and a predetermined amount of focus drive is performed at S608, and the process ends. In S607, since the change in luminance is higher when IRCF is lost, it is clear that the wavelength of the near infrared or higher wavelength component has increased significantly, so that it can be determined that the focus focus position changes. For this reason, a correction amount that is held in advance is added to the focus position in the day mode to drive the focus lens. In other words, in this embodiment, the control means focuses on the wavelength component corresponding to the wavelength component of near infrared or higher when the difference from the second luminance output result is equal to or smaller than the first luminance output result. Does not perform position adjustment correction. If the second luminance output result is larger than the first luminance output result by a predetermined value or more, the focus position adjustment corresponding to the wavelength component of near infrared or higher is corrected.

Example 3
A third embodiment of the present invention will be described. In this embodiment, when the focus position is corrected when the IRCF is removed, an appropriate correction is performed in consideration of the increase in luminance when determining whether or not the correction is necessary.

In Example 2, under the incandescent lamp, the wavelength band of light is wide, and the ratio of the wavelength in the visible light region is large. Accordingly, an example has been described in which focus correction is not performed in the day mode and the night mode depending on the characteristics of the lens. The present embodiment attempts to achieve the best position by correcting this even with a slight amount of defocus as the image quality is improved. For this. If the infrared component rises when the IRCF is removed, correction is performed to a more appropriate position. Specifically, a configuration capable of correction according to the increase is shown. For example, if there is not much increase, no correction is made assuming illumination by a fluorescent lamp or the like. If the increase is a predetermined amount, for example, a correction amount assuming an incandescent lamp is applied. It is intended to carry out a correction amount assuming under illumination.

This will be described with reference to the flowchart of FIG. In S701, it is determined whether or not IRCF is present. If so, it is determined in S702 whether the focus is in auto or manual mode. In the manual mode, the luminance value Y1 is read in S703, the focus position is read in S704, and the process ends. If IRCF is not included in S701, the luminance value Y2 is read in S705. Next, in S706, the luminance values Y1 and Y2 are compared. If the result is not greater than the predetermined value TH1, a predetermined correction amount is corrected. However, when TH1 is 0, the focus correction amount 1 is 0 and no correction is required. In this case, this is equivalent to not performing correction driving with a correction amount of 0 in S708.

Next, in S706, when Y2 is larger than the luminance value Y1 by the predetermined value TH1, the difference between Y2 and Y1 is compared with the predetermined value TH2 in S709. If the difference is smaller than TH2 in S709 (that is, greater than TH1 and less than TH2), a predetermined focus correction amount 2 is obtained in S710. On the other hand, if the difference is larger than TH2 in S709, a predetermined focus correction amount 3 is obtained in S711. Then, focus driving is performed in S708. In view of the fact that the brightness value when IRCF is lost is high, it is clear that the wavelength of the near infrared or higher wavelength component is increasing, and it can be determined that the focus focus position can be changed. . For this reason, the respective correction amounts possessed in advance according to the luminance difference are obtained when the IRCF is lost, and the focus lens is driven for correction. That is, if the second luminance output result is the same or lower than the first luminance output result or is larger than a predetermined first luminance threshold value compared with the first luminance output result, the control means does not perform correction driving or first The focus position adjustment is corrected by the correction amount. The difference between the first luminance output result and the second luminance output result is compared with a predetermined second luminance threshold value, and the difference is larger than the predetermined first luminance threshold value. When the brightness threshold value is less than 2, the focus position adjustment is corrected by the second correction amount. When the difference is larger than the predetermined second luminance threshold value, the focus position adjustment is corrected by a third correction amount that is larger than the second correction amount. The above control method of this embodiment can also be understood as follows. That is, the control means does not perform correction driving when the second luminance output result is the same as or lower than the first luminance output result. On the other hand, the difference between the first luminance output result and the second luminance output result is compared with a predetermined luminance threshold value, and the focus position adjustment corresponding to the wavelength component of near infrared or higher is performed according to the comparison difference. Make corrections.

As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1 .. Lens (imaging optical system, focusing means), 2 .. Infrared light removal filter (IRCF, filter means), 3 .. Image sensor, 11 .. Luminance value calculation unit, 12. IRCF driving means (insertion / extraction means), 14 Lens driving means (focusing means)

Claims (9)

Photographic optics,
Focusing means for adjusting the focus position of the photographing optical system;
An image sensor for converting a subject image formed by the photographing optical system into an electrical signal;
A luminance value calculation unit for acquiring the luminance of the image from the electrical signal of the image sensor;
Filter means for preventing light components of a predetermined range of wavelengths from the imaging optical system from passing through the imaging device;
Insertion / extraction means for taking the filter means in and out of the optical path of the photographing optical system;
Control means for controlling the focus means and the insertion / extraction means;
Have
The control unit stores an output result of the luminance value calculation unit in a state where the filter unit is inserted in an optical path of the photographing optical system as a first luminance output result, and the first luminance output result and the The second luminance output result from the luminance value calculation unit in a state where the filter means is omitted is compared, and from the luminance difference between the first luminance output result and the second luminance output result, the predetermined range of An imaging apparatus having a function of determining whether or not to perform focus position adjustment correction corresponding to a light component of a wavelength. The filter means is an infrared light removal filter;
The control means determines whether or not to correct the focus position adjustment corresponding to the wavelength component of near infrared or higher from the luminance difference between the first luminance output result and the second luminance output result. The photographing apparatus according to claim 1, wherein the photographing apparatus has a function. When the second luminance output result is the same or lower than the first luminance output result, the control means corresponds to the light component of the predetermined range of wavelength or the wavelength component of near infrared or higher. If the second brightness output result is larger without performing focus position adjustment correction, performing focus position adjustment correction corresponding to the light component of the wavelength in the predetermined range or the wavelength component of near infrared or higher. The imaging apparatus according to claim 1, wherein the imaging apparatus is characterized. When the difference from the second luminance output result is less than or equal to a predetermined value compared to the first luminance output result, the control means is a light component having a wavelength in the predetermined range or a wavelength greater than or equal to the near infrared If the second luminance output result is larger than the first luminance output result by a predetermined value or more without correcting the focus position adjustment corresponding to the component, the light component of the wavelength in the predetermined range or the near infrared or higher The imaging apparatus according to claim 1, wherein a focus position adjustment correction corresponding to the wavelength component is performed. The control means does not perform correction driving when the second luminance output result is equal to or lower than the first luminance output result, and the first luminance output result and the second luminance output result. Is compared with a predetermined luminance threshold value, and focus position adjustment correction corresponding to the light component of the wavelength in the predetermined range or the wavelength component of near infrared or higher is performed according to the comparison difference. The imaging apparatus according to claim 1 or 2. If the second luminance output result is the same as or lower than the first luminance output result or larger by a predetermined first luminance threshold value or less than the first luminance output result, the control means does not perform correction driving. And the difference between the first luminance output result and the second luminance output result is compared with a predetermined second luminance threshold value, and the difference is If it is larger than the first luminance threshold but less than or equal to the predetermined second luminance threshold, the focus position adjustment is corrected by a second correction amount, and the difference becomes the predetermined second luminance. 3. The image pickup apparatus according to claim 1, wherein when the threshold value is larger than the threshold value, the focus position adjustment is corrected by a third correction amount larger than the second correction amount. The imaging apparatus according to claim 1, wherein the control unit corrects the focus position adjustment when the focus position adjustment is in a manual focus mode. 8. The photographing apparatus according to claim 1, wherein a dummy glass for optical path length compensation enters the optical path when the filter means or the infrared light removal filter is removed. The control means has an optical path length correction function for correcting a predetermined optical path length when the filter means or the infrared light removal filter is removed.
When it is determined that the correction of the focus position adjustment corresponding to the light component of the wavelength in the predetermined range or the wavelength component of near infrared or higher is not necessary, only the correction of the predetermined optical path length is performed, When it is determined that correction of focus position adjustment corresponding to a light component or a wavelength component of near infrared or higher is necessary, an amount obtained by adding the correction amount of the predetermined optical path length and the correction amount of the corresponding focus position adjustment The photographing apparatus according to any one of claims 1 to 7, wherein correction is performed as a focus position adjustment correction by the focus unit.

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