JP2007282028A - On-board camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-board camera in which an image with a good visibility can be captured by one shot under the conditions that a brightness difference is large, and it can be intended to curtail the number of components and reduce a cost. <P>SOLUTION: In the on-board camera which photographs out of a vehicle by use of a solid-state imaging device in which a plurality of photodiodes (PD) 30a, 30b are two-dimensionally arranged, the solid-state imaging device comprises a high sensing part 40 composed of a PD 30a having a large light receiving area, and an imaging face 22a composed of a low sensing part 41 composed of a PD 30b having a small light receiving area. The low sensing part 41 images a high brightness region on which beams are irradiated from a headlight, and the high sensing part 40 surrounding the low sensing part 41 images a low brightness region on which beams are not irradiated from the headlight. Incidentally, the high sensing part and the low sensing part can be configured by changing a light condensing property of a micro-lens on the PD. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an in-vehicle camera installed in a vehicle.

  When driving a vehicle in a low light environment at night, the headlight is turned on, but for the driver, the high brightness difference (contrast difference) causes poor visibility in the low brightness area where the headlight light is not irradiated, Discovery of pedestrians and bicycles tends to be delayed.

As a technique for solving such a problem, there is known a device that assists the driver's vision by photographing the driver's field of view with an in-vehicle camera mounted on the vehicle and displaying the image on the monitor toward the driver. (For example, see Patent Documents 1 and 2). In the apparatus described in Patent Document 1, two types of cameras, a visible light camera and an infrared camera, are used to synthesize two types of images obtained in order to clearly display both a region with good visibility and a region with poor visibility. ing. The apparatus described in Patent Document 2 secures a dynamic range that can cope with a high luminance difference by acquiring two types of images having different exposure times and combining them.
Japanese Patent Laid-Open No. 11-308609 JP 2000-217100 A

  However, in the apparatuses described in Patent Documents 1 and 2, since it is necessary to provide a plurality of cameras and to perform image composition, the apparatus becomes complicated, resulting in an increase in the number of parts and an increase in cost. The in-vehicle camera is desirably as compact as possible because it has a limited installation place in the vehicle, and of course, it is also desirable that it be inexpensive.

  The present invention has been made in view of such circumstances, and can obtain an image with good visibility under a situation where the luminance difference is large, and can reduce the number of parts and reduce the cost. An object is to provide an in-vehicle camera that can be realized.

  In order to achieve the above object, an in-vehicle camera according to the present invention is an in-vehicle camera that performs imaging outside a vehicle using a solid-state imaging device in which a plurality of photodiodes are two-dimensionally arranged. A low-sensitivity part and a high-sensitivity part are provided, and a high-brightness region irradiated with light from a vehicle lighting device is imaged by the low-sensitivity unit, and a low-brightness region not irradiated with light from the lighting device is imaged by the high-sensitivity unit. It is characterized by doing.

  The low-sensitivity portion and the high-sensitivity portion are preferably configured by changing the light receiving area of the photodiode. Moreover, it is also preferable that the low sensitivity part and the high sensitivity part are configured by changing the light condensing property of the microlens on the photodiode. Moreover, it is preferable that the said high sensitivity part is arrange | positioned so that the circumference | surroundings of the said low sensitivity part may be enclosed.

  Moreover, it is preferable that the said illuminating device is a headlight. Furthermore, it is preferable to output an image captured by the solid-state imaging device to a monitor installed in the vehicle.

  In the in-vehicle camera of the present invention, the solid-state imaging device includes a low-sensitivity portion and a high-sensitivity portion having different light receiving sensitivities, and images a high-brightness region irradiated with light from the vehicle illumination device by the low-sensitivity portion. Since a low-luminance area that is not irradiated with light is imaged by a high-sensitivity part, an image with good visibility can be obtained by one shooting under a large luminance difference, and the number of parts and the cost can be reduced. be able to.

  In FIG. 1, an in-vehicle camera 10 according to the present invention is attached to an upper portion of a windshield 12 of a vehicle 11 and photographs the front of the vehicle 11 in the traveling direction through the windshield 12. The monitor 13 is installed on the dashboard 14 so that a driver or a passenger can check the screen, and displays an image obtained by the in-vehicle camera 10. The in-vehicle camera 10 and the monitor 13 function as a driving support system for assisting the driver's vision at night. In addition, the installation place of the vehicle-mounted camera 10 and the monitor 13 is not restricted to said position, You may change suitably.

  The imaging area 15 is an area that is imaged by the CCD image sensor 22 (see FIG. 2) in the in-vehicle camera 10, and is set to substantially coincide with the visual field area of the driver. The high brightness area 16 in the imaging area 15 is an area where light is emitted from the headlight of the vehicle 11 and the driver can visually recognize the scenery. The periphery of the high luminance region 16 is a low luminance region 17 where light is not irradiated from the headlight of the vehicle 11, and it is difficult for the driver to visually recognize an object in this region.

  In FIG. 2, an in-vehicle camera 10 includes a CPU (main control circuit) 20, an imaging lens 21, a CCD image sensor 22, a CDS (double correlation sampling) / AGC (auto gain control) circuit 23, an A / D converter 24, A DSP (digital signal processing circuit) 25 and a communication unit 26 are included.

  The CPU 20 controls the operation of each unit. The imaging lens 21 is composed of one or a plurality of lenses, and makes the light in the imaging area 15 enter the CCD image sensor 22. As will be described in detail later, the CCD image sensor 22 includes an imaging surface 22a (see FIG. 4) composed of two types of sensitivity portions having different light receiving sensitivities, and separates the high brightness region 16 and the low brightness region 17 from different sensitivity portions. Take an image with.

  The CDS / AGC circuit 23 samples and holds the imaging signal output from the CCD image sensor 22, and at the same time performs amplification with an appropriate gain. The A / D converter 24 converts the imaging signal output from the CDS / AGC circuit 23 into digital image data, and inputs the image data to the DSP 25.

  The DSP 25 performs predetermined image processing such as color interpolation, YC conversion, gamma correction, contour correction, and white balance correction on the input image data. The communication unit 26 outputs the image data subjected to image processing by the DSP 25 to the monitor 13. The captured image is displayed on the monitor 13 as a through image.

  Next, the configuration of the CCD image sensor 22 will be described. In FIG. 3, a CCD image sensor 22 includes two types of photodiodes (PD) 30a and 30b which are two-dimensionally arranged and have different light receiving sensitivities, and a read transfer gate (TG) 31 connected to each PD 30a and 30b. , A vertical CCD (VCCD) 32 provided for each vertical column, a horizontal CCD (HCCD) 33 commonly connected to the last stage of each VCCD 32, and an output amplifier 34 connected to the last stage of the HCCD 33. ing. The PD 30a has a larger light receiving area and higher sensitivity than the PD 30b.

  The PDs 30a and 30b photoelectrically convert received light to generate signal charges, and accumulate the generated signal charges. The TG 31 transfers the signal charges accumulated in the PDs 30a and 30b to the VCCD 32 at the same time when the exposure period ends. The VCCD 32 receives the signal charge transferred from the TG 31 and performs vertical transfer step by step toward the HCCD 33. The HCCD 33 receives the signal charges output from the final stage of each VCCD 32 one by one, and performs horizontal transfer toward the output amplifier 34 each time one stage of signal charges is received. The output amplifier 34 detects the signal charge output from the final stage of the HCCD 33 and outputs a voltage signal (imaging signal) corresponding to the charge amount of the signal charge.

  In FIG. 4, the imaging surface 22a of the CCD image sensor 22 includes a high sensitivity portion 40 in which high sensitivity PDs 30a are arranged and a low sensitivity portion 41 in which low sensitivity PDs 30b are arranged. Since the total number of PDs 30a and 30b is actually as large as several million, for the sake of simplicity, the number of PDs 30a and 30b is greatly reduced. The low sensitivity portion 41 has a shape suitable for the high luminance region 16 so that the high luminance region 16 can be imaged. A region other than the low sensitivity portion 41 in the imaging surface 22a is the high sensitivity portion 40, and the high sensitivity portion 40 images the low luminance region 17 described above. Note that the areas of the low-sensitivity portion 41 and the high-sensitivity portion 40 may be appropriately changed according to the shapes of the high-luminance region 16 and the low-luminance region 17. Further, the PDs 30a and 30b are not limited to the square arrangement, and may be other arrangements such as a honeycomb arrangement.

FIG. 5 shows a cross-sectional structure of the PDs 30a and 30b. A p-type well layer 51 is formed on the n-type silicon substrate 50. In the p-type well layer 51, n-type layers 52a and 52b for accumulating signal charges (electrons) generated by photoelectric conversion are formed, and p ⁺ -type layers are respectively formed on the n-type layers 52a and 52b. 53a and 53b are formed. In addition to the p ⁺ -type layers 52 a and 52 b, an n-type layer 54 is formed on the surface layer of the p-type well layer 51. A transfer electrode is disposed above the n-type layer 54 via a gate insulating film 55. 56 is formed.

The transfer electrode 56 is shielded from light by a light shielding film 58 provided via an interlayer insulating film 57, and openings 58a and 58b are formed in the light shielding film 58 above the p ⁺ type layers 53a and 53b, respectively. ing. The light shielding film 58 is covered with a planarization film 59, and a color filter 60 that transmits light of a specific wavelength such as red, green, and blue is provided on the planarization film 59. On the color filter 60, a microlens 61 that collects incident light is provided.

  The PDs 30a and 30b are configured as buried photodiodes by pnpn junctions under the openings 58a and 58b, respectively. The opening 58a has a larger opening area (light receiving area) than the opening 58b, and the PD 30a has higher light receiving sensitivity than the PD 30b. The TG 31 includes a p-type well layer 51 and a transfer electrode 56 between the n-type layers 52a and 52b and the n-type layer 54. The VCCD 32 includes the n-type layer 54 and the transfer electrode 56. ing. The transfer electrode 56 performs charge transfer control of the TG 31 and the VCCD 32 according to the applied voltage.

  As described above, the CCD image sensor 22 incorporated in the in-vehicle camera 10 includes the low sensitivity unit 41 that images the high luminance region 16 and the high sensitivity unit 40 that images the low luminance region 17. An image with good visibility under a large situation can be acquired by one shooting. In addition, since the vehicle-mounted camera 10 has the same configuration as that of a normal vehicle-mounted camera or surveillance camera except for the CCD image sensor 22, the number of parts can be reduced and the cost can be reduced.

  In the above embodiment, the low-sensitivity part and the high-sensitivity part are configured by changing the light receiving area of the PD, but the present invention is not limited to this, and the low-sensitivity part and the high-sensitivity part are collected by the condensing of the microlens. It is also possible to configure by changing the sex. FIG. 6 shows a second embodiment of the present invention. An imaging surface 70 is a low-sensitivity portion in which a microlens 72 having a small diameter and a low light condensing property is arranged with respect to a PD 71 that is two-dimensionally arranged and has the same light receiving area. 73 and a high-sensitivity portion 75 provided with a microlens 74 having a large diameter and a high light collecting property.

  In the above-described embodiment, a CCD image sensor is taken as an example of a solid-state imaging device built in a vehicle-mounted camera. However, the present invention is not limited to this, and a CMOS image sensor or the like can be used instead of the CCD image sensor. It is also possible to apply a solid-state imaging device.

  Moreover, in the said embodiment, although the imaging | photography direction of a vehicle-mounted camera is made into the direction (front) in which the light of a headlight is irradiated, this invention is not limited to this, This imaging | photography direction is used for other things, such as a backlight. The direction in which the light of the illumination device is irradiated can also be set.

  Moreover, in the said embodiment, although the imaging surface was comprised by 2 types of sensitivity parts, a low sensitivity part and a high sensitivity part, this invention is not limited to this, An imaging surface is comprised by 3 or more types of sensitivity parts. May be.

It is the schematic which shows the vehicle which installed the vehicle-mounted camera and the monitor. It is a block diagram which shows the structure of a vehicle-mounted camera. It is the schematic which shows the structure of a CCD image sensor. It is a top view which shows the imaging surface of a CCD image sensor. It is sectional drawing which follows the AA line of FIG. It is a figure which shows 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Car-mounted camera 11 Vehicle 13 Monitor 15 Imaging area 16 High brightness area 17 Low brightness area 22 CCD image sensor 22a Imaging surface 30a, 30b Photodiode 40 High sensitivity part 41 Low sensitivity part 70 Imaging surface 72, 74 Micro lens 73 Low sensitivity part 75 High sensitivity part

Claims (6)

In an in-vehicle camera that performs imaging outside a vehicle using a solid-state imaging device in which a plurality of photodiodes are two-dimensionally arranged,
The solid-state imaging device includes a low sensitivity portion and a high sensitivity portion with different light receiving sensitivities,
An in-vehicle camera, wherein a high-luminance region irradiated with light from a lighting device of a vehicle is imaged by the low-sensitivity portion, and a low-luminance region not irradiated with light from the lighting device is imaged by the high-sensitivity portion.   The in-vehicle camera according to claim 1, wherein the low sensitivity part and the high sensitivity part are configured by changing a light receiving area of a photodiode.   The in-vehicle camera according to claim 1, wherein the low-sensitivity part and the high-sensitivity part are configured by changing a condensing property of a microlens on a photodiode.   The in-vehicle camera according to any one of claims 1 to 3, wherein the high sensitivity part is disposed so as to surround the low sensitivity part.   The in-vehicle camera according to claim 1, wherein the illumination device is a headlight.   6. The vehicle-mounted camera according to claim 1, wherein an image captured by the solid-state image sensor is output to a monitor installed in a vehicle.

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