JP4288544B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus, and can be applied to an imaging apparatus for confirming the rear of an automobile, for example. The present invention makes it possible to provide a color image with sufficient sensitivity by capturing an image of a predetermined subject in a wider band than human visual sensitivity characteristics and adjusting the auto white balance.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is an image pickup apparatus for a vehicle that can be used for confirming the rear of an automobile and can contribute to safety.
[0003]
In a system using such an imaging device, a rear image is mainly captured using a black and white television camera so that the rear and the like can be confirmed with sufficient brightness even at night, and a black and white monitor device Thus, the imaging result is displayed.
[0004]
[Problems to be solved by the invention]
By the way, in the image obtained from the imaging device, the color image has a characteristic that the amount of information is remarkably larger than that of the black and white image. Therefore, in the vehicular imaging apparatus, if it is possible to confirm the rear side or the like by a color image, it is possible to provide various information useful to the driver or the like as compared with the case of confirming by a black and white image. Conceivable.
[0005]
However, in the case of a color image, there is a problem that the sensitivity is inferior to that in the case of a black and white image.
[0006]
The present invention has been made in consideration of the above points, and intends to propose an imaging apparatus capable of providing a color image with sufficient sensitivity.
[0007]
[Means for Solving the Problems]
In order to solve such a problem, in the invention of claim 1, the gain is varied by a predetermined control signal, the imaging means for outputting the imaging result of the predetermined subject with a wide band compared to the human visibility characteristic, Variable gain amplifying means for amplifying and outputting red, blue and green color signals obtained from the imaging result, and control means for outputting the previous control signal based on the imaging result by the imaging means are provided. . The imaging means is set so that the peak of the red wavelength band in the spectral characteristics of the imaging device is suppressed, and the sensitivity in the near-red region is relatively increased .
[0008]
According to the imaging means that outputs the imaging result of a predetermined subject with a wider band than the human visual sensitivity characteristic, it is possible to obtain an imaging result with higher sensitivity than in the case of a normal color image. Further, the gain is varied by a predetermined control signal, and the red, blue and green color signals obtained from the imaging result are amplified and output, and the previous control is performed based on the imaging result by the imaging unit. By providing control means for outputting a signal, it is possible to prevent a sense of incongruity by adjusting the white balance of the imaging result in a wider band than the human visual sensitivity characteristic.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
[0010]
(1) Configuration of Embodiment FIGS. 2A and 2B are a side view and a rear view showing an automobile equipped with an imaging apparatus according to the first embodiment of the present invention. The vehicle 1 is configured such that the imaging device 1 is disposed on a rear bumper, and the rear side is imaged by the imaging device 1 so that obstacles and the like behind the vehicle can be confirmed. In FIG. 2, a range that can be imaged by the imaging apparatus 1 is indicated by a broken line.
[0011]
Here, as shown in FIG. 1, the imaging apparatus 1 obtains an imaging result in a wider band than the human visual sensitivity characteristic by an imaging device 2 such as a CCD solid-state imaging device, and processes the imaging result to install the imaging device in a vehicle. Display on the monitor device.
[0012]
Here, the image sensor 2 is a so-called near-infrared image sensor, and a so-called color filter is disposed on the light receiving surface. In this color filter, for the pixels that are continuous in the horizontal direction, the first filter that transmits incident light without any band limitation, and the second and third filters of the complementary color system corresponding to the color difference signal are cyclic in order. Repeatedly configured. Thereby, the imaging device 2 can output the imaging result by a color image by calculating the imaging result between successive pixels.
[0013]
Further, as indicated by reference numeral A in FIG. 3, the imaging element 2 has a peak in the red wavelength band suppressed as compared with the spectral characteristics of the normal imaging element indicated by reference numeral B, and the relative red region is relatively reduced accordingly. The sensitivity is increased. As a result, the image pickup device 2 can pick up a desired subject with higher sensitivity than a conventional image pickup device because the subject can be picked up with a wider band than the human visual sensitivity characteristic.
[0014]
As shown in FIG. 4, after the image pickup element 2 is held by a CCD holder 3 as a base material, a seal rubber 4 as a buffer material is disposed on the image pickup surface side, and an optical low-pass filter ( LPF) 5 is arranged. In the image pickup device 2, an adapter 6 made of resin is disposed on the front surface of the optical low-pass filter 5, and a lens 7 is disposed through the adapter 6.
[0015]
As a result, the imaging apparatus 1 also has a band in which the imaging element 2 has sensitivity, and in a normal imaging apparatus, a near-infrared ray that restricts the incidence on the imaging element 2 by an infrared cut filter is also removed from the lens 7. The light is incident on the image sensor 2, so that an imaging result can be obtained with a wider band than human visual sensitivity characteristics.
[0016]
In this way, when the camera is mounted on a vehicle and images the outside during the daytime, the imaging element 2 is relatively increased in sensitivity in this manner because the imaging target is illuminated with sunlight. A sufficient amount of incident light can be secured even in the near red region. On the other hand, at night, a subject is illuminated by a halogen lamp or a xenon lamp used in this type of vehicle, and these lamps illuminate the subject with a wider band than human visibility characteristics. become. As a result, the imaging apparatus 1 can capture a desired subject with a sufficient amount of incident light even at night as compared with an imaging apparatus using a conventional imaging device. FIG. 5 is a characteristic curve diagram showing the spectral characteristics of the halogen lamp. According to this characteristic curve diagram, it can be seen that the halogen lamp emits illumination light with a sufficient amount of light in the near infrared region, which is difficult to perceive by human vision.
[0017]
The preamplifier 10 (FIG. 1) amplifies the output signal of the image pickup device 2 with a predetermined gain and outputs the amplified signal, and the analog / digital conversion circuit (A / D) 12 passes through a correlated double sampling circuit (not shown). An output signal is input, analog-digital converted, and output.
[0018]
The digital signal processing circuit 13 processes the output signal of the analog-digital conversion circuit 12 to generate a video signal SV1, and outputs the video signal SV1 to an in-vehicle monitor device.
[0019]
That is, in the digital signal processing circuit 13, the primary color separation circuit 14 performs a matrix operation process on the output signals of the analog-digital conversion circuit 12 between the output signals corresponding to the continuous pixels, so that the red color signal R and the blue color signal B are processed. A green color signal G is generated. At this time, the primary color separation circuit 14 performs arithmetic processing using a different weighting coefficient (which is a matrix arithmetic coefficient) when processing an imaging result obtained by a similar imaging element in which an IR filter is arranged, and thereby the subject is separated. Even when the color temperature changes, the color signals R, G, and B are generated so that the hue in the video signal SV1 does not change.
[0020]
The variable gain amplifier circuits 15R, 15G, and 15B switch the gain by the control signal S1 output from the system controller 16, and amplify and output the color signals R, G, and B output from the primary color separation circuit 14.
[0021]
The gamma correction circuit 17 corrects and outputs the gamma of each color signal R, G, B output from the variable gain amplification circuits 15R, 15G, 15B, and the subsequent color difference matrix circuit 18 outputs these color signals R, G, B. Is subjected to matrix calculation processing to generate a luminance signal and a color difference signal.
[0022]
The encoder 19 processes the luminance signal and the color difference signal to generate and output a luminance signal and a chroma signal, and the digital / analog conversion circuit (D / A) 20 performs a digital / analog conversion process on the output signal of the encoder 19. Thereafter, addition is performed, thereby generating and outputting a composite video signal SV1.
[0023]
The optical detector 21 performs arithmetic processing on the color signals R, G, and B output from the variable gain amplifier circuits 15R, 15G, and 15B, thereby generating signals necessary for automatic white balance adjustment from the imaging result, and the system controller 16 The system controller 16 generates the control signal S1 based on the output signal of the optical detector 21, thereby adjusting and outputting the gains of the color signals R, G, and B. As a result, the optical detector 21, the system controller 16, and the variable gain amplifier circuits 15R, 15G, and 15B constitute an auto white balance adjustment circuit that expands the band to the near-infrared region side compared to human visibility characteristics, Even when an image is captured, sufficient color reproducibility can be ensured.
[0024]
FIG. 6 is a block diagram showing the optical detector 21 and the system controller 16. The optical detector 21 inputs the red and green color signals R and G out of the color signals R, G, and B output from the variable gain amplification circuits 15R, 15G, and 15B to the subtraction circuit 22, and these color signals R , G subtraction signal RG is generated. Further, the blue and green color signals B and G are input to the subtraction circuit 23, and the subtraction signal BG of the color signals B and G is generated. Thereby, the optical detector 21 generates differential signals RG and BG of the red color signal R and the blue color signal B with respect to the green color signal G.
[0025]
Further, the optical detector 21 adds the color signals R, G, and B to generate an equalized luminance signal NAMY that is substantially equal to the luminance signal. In the optical detector 21, the integrating circuit 24 integrates and outputs the difference signals RG and BG output from the subtracting circuits 22 and 23 in units of fields. At this time, the integrating circuit 24 falls when the signal level of the equalized luminance signal NAMY rises from the first reference level set near the saturation level, or falls below the second reference level set around the 0 level. The corresponding difference signals RG and BG are excluded from integration targets. Further, the integration circuit 24 uses the third reference level set to a substantially intermediate reference level between the first and second reference levels as a boundary, so that the difference signal R− corresponding to the high luminance side and the low luminance side corresponds. G and BG are selectively integrated, and integration results are detected on the high luminance side and the low luminance side, respectively.
[0026]
In the system controller 16, these integration results are processed by executing a built-in processing procedure to generate a control signal S1. In FIG. 6, the configuration of the system controller 16 will be described using functional blocks configured by executing this processing procedure.
[0027]
That is, in the system controller 16, the comparison circuit 25 compares the integration result on the high luminance side with the integration result on the low luminance side, and selectively outputs the integration result on the smaller value side. The adder circuit 26 adds the integration results of the difference signals RG and BG selected by the comparison circuit 25, and outputs the integration result represented by R + B-2G. The subtraction circuit 27 subtracts the integration result of the difference signals RG and BG selected by the comparison circuit 25 and outputs the integration result represented by RB.
[0028]
The gain setting circuit 28 generates a control signal S1 based on the output signals of the adder circuit 26 and the subtractor circuit 27, thereby adjusting the audio white balance. In this embodiment, the gain setting circuit 28 is a variable that processes the green color signal G and the blue color signal B because the band on the long wavelength side is relatively expanded as compared with the imaging result in a normal imaging device. The control signal S1 is generated so that the gain of the variable gain amplifier circuit 15R that processes the red color signal R is relatively lower than the gains of the gain device circuits 15G and 15B. Even when a desired subject is imaged with high sensitivity by enlarging the image, sufficient color reproducibility can be ensured.
[0029]
(2) Operation of Embodiment In the above configuration, the imaging device 1 (FIGS. 1 and 2) images the blind spot behind the vehicle via the lens 7, and the imaging result is obtained from the solid-state imaging device 2. . In the imaging apparatus 1, the imaging result is processed by the digital signal processing circuit 13 to generate color signals R, G, and B. The color signals R, G, and B are converted into a video signal SV1 through processing such as gamma correction. Then, the video signal SV1 is displayed by the on-vehicle monitor device. Thereby, in the imaging device 1, it becomes possible to confirm an obstruction behind the back. Furthermore, since the back can be confirmed by a color image, it becomes possible to provide much information to the driver accordingly.
[0030]
In the imaging apparatus 1, when the rear side is imaged in this way, the incident light of the lens 7 is received by the imaging element 2 without passing through the infrared cut filter (FIG. 4), and the imaging element 2 is in the near red region. Since the sensitivity is relatively increased (FIG. 3), it is possible to obtain an imaging result with a wider band than human visual sensitivity characteristics, thereby obtaining a color image with high sensitivity.
[0031]
By the way, when the band is expanded to the near red range in this way, the color reproducibility will deteriorate accordingly, and obstacles etc. due to the hue that is significantly different from the hue that the driver actually sees visually Images will be provided. That is, an unnatural color image is provided to the driver.
[0032]
For this reason, in the image pickup apparatus 1, the primary color separation circuit 14 generates color signals R, G, and B by matrix calculation processing using matrix calculation coefficients different from those of a normal image pickup apparatus. Color signals R, G, and B are generated so that the color reproducibility does not change greatly.
[0033]
Further, after the color signals R, G, and B generated in this way are integrated by the optical detector 21, a control signal S1 is generated based on the integration result to control the gains of the color signals R, G, and B, respectively. In the result, the auto white balance adjustment is performed so that the relative gain of the red color signal R is lower than the gain of the green color signal G and the blue color signal B because the band on the long wavelength side is relatively expanded. Is done. As a result, the image pickup apparatus 1 can ensure sufficient color reproducibility even when a desired subject is picked up with high sensitivity by expanding the band to the long wavelength side, and thereby, compared with a conventional black and white image pickup apparatus. More information can be provided to the driver. In this way, it was confirmed that the auto white balance was adjusted in this way, and the pull-in range where the auto white balance could be adjusted could be secured from 2500 degrees K to 9500 degrees K.
[0034]
(3) Effects of Embodiments According to the above configuration, a color image can be provided with sufficient sensitivity by capturing an image of a predetermined subject and adjusting the auto white balance in a wider band than human visual sensitivity characteristics. Therefore, much more information can be provided to the driver. Therefore, accidents and driving mistakes can be reduced when backing up at night or in dark parking lots.
[0035]
(4) Other Embodiments In the above-described embodiment, the case where the imaging device is arranged for rearward confirmation has been described. However, the present invention is not limited to this, and as shown in FIG. May be used for side confirmation.
[0036]
In the above-described embodiment, the case where the differential signals RG and BG are generated and integrated has been described. However, the present invention is not limited to this, and after the color signal is integrated, A difference signal may be generated.
[0037]
Further, in the above-described embodiment, the case where the present invention is applied to an in-vehicle imaging device has been described. However, the present invention is not limited thereto, and is disposed in an imaging device mounted on a train, a ship, etc. The present invention can be widely applied to imaging devices and the like.
[0038]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a color image with sufficient sensitivity by capturing an image of a predetermined subject and adjusting the auto white balance in a wider band than the human visual sensitivity characteristic.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an imaging apparatus according to an embodiment of the present invention.
FIGS. 2A and 2B are a side view and a rear view showing an automobile on which the imaging apparatus shown in FIG. 1 is mounted.
3 is a characteristic curve diagram showing spectral characteristics of a solid-state imaging device of the imaging apparatus of FIG. 1. FIG.
4 is an exploded perspective view showing a peripheral configuration of a solid-state imaging element of the imaging apparatus of FIG. 1. FIG.
FIG. 5 is a characteristic curve diagram showing optical characteristics of the halogen lamp.
6 is a block diagram illustrating a configuration of an optical detector and a system controller of the imaging apparatus in FIG. 1. FIG.
FIGS. 7A and 7B are a plan view and a side view illustrating a mounting example of an imaging device according to another embodiment. FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Imaging device, 2 ... Solid-state image sensor, 14 ... Primary color separation circuit, 15R, 15G, 15B ... Variable gain amplifier circuit, 16 ... System controller, 21 ... Optical detector

Claims (3)

An imaging means for outputting an imaging result of a predetermined subject with a wide band compared to human visibility characteristics;
Arithmetic means for processing the imaging result to generate red, blue and green color signals;
Variable gain amplifying means for amplifying the red, blue and green color signals and outputting them by varying the gain according to a predetermined control signal;
Based on the imaging result by the imaging means, e Bei and control means for outputting the control signal,
The imaging means includes
The peak of the red wavelength band in the spectral characteristics of the image sensor is suppressed, and the sensitivity in the near-red region is set to increase relatively.
Imaging device. Illumination means for illuminating the subject with illumination light having spectral characteristics with a wider band than human visibility characteristics
The imaging apparatus according to 請 Motomeko 1. Used in vehicles,
The subject is a subject located at a blind spot of the vehicle at least from the driver's seat of the vehicle.
The imaging apparatus according to 請 Motomeko 1.

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