Vehicle circumference monitor apparatus

An analog-state video signal is inputted from each of several in-vehicle cameras via a corresponding signal cable. An amendment amount for making uniform signal levels of the analog-state video signals originating from the respective in-vehicle cameras is determined, with respect to each of the analog-state video signals, based on a burst signal included in each analog-state video signal. According to the determined amendment amounts, the analog-state video signals are amplified to make uniform the signal levels, obtaining analog-state uniformed video signals, respectively. A composite image of combining images originating from the in-vehicle cameras is generated based on the obtained analog-state uniformed video signals.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and incorporates herein by reference Japanese Patent Application No. 2010-13276 filed on Jan. 25, 2010.

FIELD OF THE INVENTION

The present invention relates to a The present invention relates to a vehicle circumference monitor apparatus.

BACKGROUND OF THE INVENTION

There is conventionally known a technology to display a captured image of a circumference outside of a vehicle, thereby eliminating a dead angle of the vehicle to help prevent a collision. For example, Patent document 1 discloses a technology to capture an image to cover all angles of a circumferential area at the rear of the vehicle using a rear monitor camera, thereby enabling the recognition of the dead angle which cannot be confirmed by a vehicle mirror.

In addition, there is recently known a technology to use a bird's-eye view image as an effective means to make it easy to understand positional relation between a vehicle and an obstacle, thereby helping prevent an accidental contact. For example, Patent document 2 discloses a technology to display a bird's-eye view image which illustrates an omnidirectional circumference state outside of the vehicle viewed from a viewpoint above the vehicle, thereby making it easy to understand positional relation between the vehicle and the obstacle.

In order to display a bird's-eye view image which illustrates a circumference state of all the directions or areas surrounding the vehicle, a general technology is used as follows. That is, several cameras are installed in the vehicle so as to capture images of several circumferential areas. Such captured images by the cameras are inputted into an electronic control unit (ECU) to undergo a bird's-eye view transformation; the cameras' images having undergone the bird's-eye view transformation are combined to generate a single bird's-eye view composite image.

It is noted that the longer a cable connecting the camera with the ECU is, the more an analog signal from the camera to the ECU attenuates. Thus, a video signal is attenuated more with respect to a camera having a longer cable connecting with the ECU. As a result, an image originating from a camera having the longer cable is faded more in color definition. Further, suppose the case that the several images originating from the cameras having the cables with much mutually different lengths are combined to thereby generate or synthesize a single composite image. In such a case, the originating images are different from each other in the color definition; thus, an appearance of the synthesized single composite image is degraded to reduce a commodity value, posing a disadvantage.

It is noted that such a disadvantage arises more significantly as the size of the vehicle becomes larger to cause the installation positions of the cameras to be separated farther from each other. Therefore, in particular, such a disadvantage arises remarkably with respect to a large-sized vehicle such as a track and a bus.

In addition, a countermeasure to prevent the occurrence of the disadvantage may be adopted which applies A/D conversion to the images captured by the cameras and then transmits resultant digital video signals of the several cameras to the ECU via the corresponding signal cables. In this regard, however, such a countermeasure requires each of the cameras or camera units to have a function to execute the A/D conversion. This poses the cost increase and another disadvantage to make it difficult to reduce the size of each camera or camera unit.

SUMMARY OF THE INVENTION

The present invention is made in view of the above disadvantage. It is an object to provide a vehicle circumference monitor apparatus helping prevent deterioration of an appearance of an image synthesized using several images originating from several in-vehicle cameras and enhancing a commodity value while reducing costs and the size of each in-vehicle camera.

To achieve the above object, according to an example of the present invention, a vehicle circumference monitor apparatus in a vehicle provided as follows. A plurality of in-vehicle cameras are arranged such that at least a part of a capture target of one in-vehicle camera does not overlap with a capture target of an other camera. Each of the in-vehicle cameras captures an image of a vehicle circumferential area outside of the vehicle and outputs an analog-state video signal of the captured image via a corresponding signal cable. An electronic control unit is included to have an image combination section to generate a composite image by a combination to combine images originating from the in-vehicle cameras based on video signals inputted via the signal cables from the in-vehicle cameras. A display device is included to display the composite image generated by the image combination section. Herein, the electronic control unit further includes an amendment amount determination section to determine an amendment amount with respect to the analog-state video signal originating from each of the in-vehicle cameras based on analog signals included in the analog-state video signals inputted via the signal cables from the in-vehicle cameras, in order to make uniform signal levels of the analog-state video signals originating from the respective in-vehicle cameras.

Under the above configuration, based on analog signals inputted via the signal cables from several in-vehicle cameras, in order to make uniform the signal levels of the analog-state video signals originating from respective in-vehicle cameras, an amendment amount is determined with respect to each analog-state video signal originating from each in-vehicle camera. It is noted that the video signal inputted via the corresponding cable from the in-vehicle camera is in an analog state; the analog-state video signal has a high possibility to exhibit a tendency of the same attenuation as an analog signal inputted via the signal cable from the in-vehicle camera. That is, the attenuation of the analog-state video signal can be estimated based on the degree of the attenuation of the analog signal. Thus, based on the analog signal, the amendment amount for making uniform the signal levels of the analog-state video signals originating from the in-vehicle cameras can be determined with sufficient accuracy.

Under the above configuration, based on the determined amendment amount, the amendment about each video signal originating from each in-vehicle camera is executed to make uniform the signal levels originating from the in-vehicle cameras. This enables the combined image that is formed by combining images originating from the several in-vehicle cameras to be displayed in a state where deterioration of the appearance due to the difference in color definition is suppressed.

Further, in the above configuration, while outputting the video signals in the analog state to the electronic control unit from the in-vehicle cameras, it becomes possible to solve the disadvantage of the difference in definition of the images, which originate from the several in-vehicle cameras and arise from the variation in attenuation of the video signals resulting from the difference in length of the corresponding signal cables which send the analog-state video signals. Under the above configuration, as compared with the configuration which provides each in-vehicle camera with a component to execute the A/D conversion, costs in the whole apparatus can be reduced and the miniaturization of the in-vehicle camera or camera unit can be made easier.

As a result, while reducing the cost and making easier the miniaturization of the in-vehicle camera, the deterioration of the appearance of the composite image formed by combining the images originating from the several in-vehicle cameras can be suppressed, thereby increasing the commodity value.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is explained with reference to drawings.FIG. 1is a block diagram illustrating an overall configuration of a vehicle circumference monitor apparatus100according to an embodiment of the present invention. The vehicle circumference monitor apparatus100illustrated inFIG. 1is mounted in a subject vehicle. The vehicle circumference monitor apparatus100includes several in-vehicle cameras1ato1d(four cameras inFIG. 1), a display device2, an assist start switch3, and a circumference monitor ECU (electronic control unit)4. Further, the cameras1ato1dare collectively referred to as a cameras arrangement1. The present embodiment is explained with reference to an example case that the vehicle circumference monitor apparatus100is mounted in a track defined as a large-sized vehicle larger than a standard-sized vehicle.

The cameras1ato1dare arranged such that at least a part of a capture target of one camera does not overlap with another capture target of another camera; the cameras1ato1dcapture images in different circumferential areas outside of the vehicle, respectively. In addition, each of the cameras1ato1dhas a wide-angle lens and an imaging element such as a CCD element. The imaging element receives a light via the wide-angle lens. The received light is transformed into an analog video signal (i.e., an analog-state video signal). In the present embodiment, the cameras1ato1dare color cameras of NTSC system. In addition, the cameras1ato1dcan use a well-known CCD camera, for example.

The following explains an installation state or attachment state, in which the cameras1ato1dare installed or attached to the track, with reference toFIG. 2, which is a schematic view illustrating the installation state of the cameras1ato1din the track. In addition, TR ofFIG. 2indicates a vehicle body of the track.

First, a front camera1ais arranged in a front portion of the track, as illustrated inFIG. 2. In detail, the front camera1ais arranged such that an optic axis is directed at a road surface ahead of the vehicle, i.e., in a vehicle forward direction. The front camera1acaptures an image of a circumferential area which spreads in a predetermined angle range in the vehicle forward direction. In addition, a right side camera1bis arranged on a right side portion of the track, as illustrated inFIG. 2. In detail, the right side camera1bis arranged such that an optic axis is directed at a road surface rightward of the vehicle (i.e., in a right side of the vehicle). The right side camera1bcaptures an image of a circumferential area which spreads in a predetermined angle range in the vehicle rightward direction. In addition, a left side camera1cis arranged on a left side portion of the track, as illustrated inFIG. 2. In detail, the left side camera1cis arranged such that an optic axis is directed at a road surface leftward of the vehicle (in a left side of the vehicle). The left side camera1ccaptures an image of a circumferential area which spreads in a predetermined angle range in the vehicle leftward direction. In addition, a rear camera1dis arranged on a rear portion of the track, as illustrated inFIG. 2. In detail, the rear camera1dis arranged such that an optic axis is directed at a road surface rearward of the vehicle (i.e., in a rear of the vehicle). The rear camera1dcaptures an image of a circumferential area which spreads in a predetermined angle range in the vehicle rearward direction.

The cameras1ato1dare arranged such that captured images overlap with one another at edge portions. In other words, an edge portion of the region image-captured by the front camera1aoverlaps with an edge portion of the region image-captured by the right side camera1b; an edge portion of the region image-captured by the front camera1aoverlaps with an edge portion of the region image-captured by the left side camera1c; an edge portion of the region image-captured by the right side camera1boverlaps with an edge portion of the region image-captured by the rear camera1d; and an edge portion of the region image-captured by the left side camera1coverlaps with an edge portion of the region image-captured by the rear camera1d.

Each image captured by each camera is referred to as follows: an image by the front camera1ais a front image; an image by the right side camera1bis a right side image; an image by the left side camera1cis a left side image; an image by the rear camera1dis a rear image.

In addition, the right side camera1bmay be arranged such that an optic axis is directed at a road surface in a circumferential area, which is located on a rear portion of a right side of the vehicle to capture an image of a circumferential area which spreads in a predetermined angle range in the rear portion of the right side of the vehicle. In contrast, the left side camera1cmay be arranged such that an optic axis is directed at a road surface in a circumferential area, which is located on a rear portion of a left side of the vehicle. to capture an image of a circumferential area which spreads in a predetermined angle range in the rear portion of the left side of the vehicle.

Each of the cameras1ato1doutputs an analog video signal, which is acquired by transforming using the imaging element, to the circumference monitor ECU4via signal cables5ato5d. That is, the cameras1ato1doutput, in the analog state, the video signals of the captured images to the circumference monitor ECU4via the corresponding signal cables5ato5d. Thus, the video signal in the analog state may be referred to as an analog-state video signal.

In addition, it is premised that at least one of the signal cables5ato5dconnecting the cameras1ato1dwith the circumference monitor ECU4is different from others. With respect to the body of the vehicle, the length in the forth and back direction is greater than that in the right and left direction. Even if the installation position of the circumference monitor ECU4is considered in the various manners, the deviation in length arises naturally among the signal cables5ato5dconnecting with the cameras1ato1d, which are arranged in different four sides of the vehicle. The tendency to cause such a deviation in length among the signal cables5ato5dis intensified as the size of the vehicle becomes large like a track illustrated inFIG. 2. The following explains the case where the length of the signal cable5dwhich connects the circumference monitor ECU4with the rear camera1dis significantly long as compared with the lengths of the three signal cables5ato5cwhich connect the circumference monitor ECU4with the cameras1a,1b, and1c, respectively, as illustrated inFIG. 2.

Returning toFIG. 1, the display device2is arranged in a predetermined position (for example, on a dashboard, or on a surface of an instrument panel) of the vehicle compartment of the track so that it can be seen from a driver of the track. The display device2displays an image inputted from the circumference monitor ECU4in an image display window. For example, the display device2enables a full color display and may use a liquid crystal display, an organic electroluminescence display, a plasma display, or the like. Further, the display device2may be included in a display unit of an in-vehicle navigation apparatus.

The assist start switch3is a switch, which is manipulated in order that the occupant of the subject vehicle may order the start of a circumference monitor control. The ON and OFF manipulation of the assist start switch3causes the circumference monitor ECU4to start and stop the circumference monitor control, respectively. Such a circumference monitor control is relative to a process including (i) transforming images captured by the cameras1ato1dinto bird's-eye view images; (ii) combining the several bird's-eye view images to generate or synthesize a composite image, and (iii) displaying the generated composite image in the display device2. A hazard switch or a winker switch may be used as the assist start switch3, for instance.

The circumference monitor ECU4includes mainly a microcomputer having a CPU, ROM, RAM, and backup RAM. The circumference monitor ECU4executes various kinds of control programs stored in the ROM based on the variety of information inputted from the cameras1ato1dand the assist start switch3, so as to execute various kinds of processes including the circumference monitor control. It is noted that the circumference monitor ECU4may by referred to as an electronic control unit.

In addition, the circumference monitor ECU4may be configured to receive a sensor signal from each of the various sensors, for instance, as follows: a sensor signal indicating a shift position from a shift position sensor; a sensor signal indicating a steering angle from a steering sensor; a sensor signal indicating a velocity of the vehicle from a vehicle velocity sensor; a sensor signal indicating a velocity of the vehicle from a vehicle wheel velocity sensor; and a sensor signal indicating a yaw rate from a yaw rate sensor.

The following explains an outline configuration of the circumference monitor ECU4with reference toFIG. 3.FIG. 3is a block diagram illustrating a configuration of the circumference monitor ECU4. As illustrated inFIG. 3, the circumference monitor ECU4includes a video signal acquisition section41, a signal level estimation section42, an amendment amount determination section43, a signal amplification section44, an image processing section45, and an image combination section46.

The video signal acquisition section41acquires the analog video signals inputted via the signal cables5ato5dfrom the cameras1ato1d. Hereinafter, an analog video signal originating from the front camera1ais referred to as a video signal A; an analog video signal originating from the right side camera1bis referred to as a video signal B; an analog video signal originating from the left side camera1cis referred to as a video signal C; and an analog video signal originating from the rear camera1dis referred to as a video signal D.

Explanation about the analog video signal is given usingFIG. 4.FIG. 4is a diagram illustrating a waveform of an analog video signal. In the present embodiment, the cameras1ato1duse color cameras of NTSC system; an analog video signal includes (i) a waveform of a brightness signal and color signal as a signal representing video information (i.e., a signal representing an image), and (ii) a waveform of a synchronization signal and burst signal (i.e., color burst signal) in a blanking period preceding the signal representing video information. InFIG. 4, E represents an amplitude of the synchronization signal, F represents an amplitude of the burst signal, G represents a maximum amplitude of a brightness signal, H represents a maximum amplitude of a color signal, and I represents a black level.

Returning toFIG. 3. The signal level estimation section42compares amplitude values (signal amplitude levels) of the burst signals of the video signals A to D acquired in the video signal acquisition section41. As the result of such comparison, the greatest amplitude value of the burst signal is defined as a reference value (i.e., reference level); a difference is calculated between the amplitude value of each of the burst signals of the video signals A to D and the reference value. The calculated difference is estimated as a difference of the signal level of each video signal A to D. Therefore, the signal level estimation section42may be referred to as a level estimation section. It is noted that the amplitude value of the burst signal of the video signal used as the reference value may be not subjected to the calculation of the difference, or regarded as zero (0), thereby allowing the estimation that the relevant video signal has no difference in signal level. In addition, the amplitude value of the burst signal may adopt either a total amplitude value or a half amplitude value.

In addition, each of the video signals A to D is in the state of an analog signal; it has a tendency in attenuation equivalent to that of its own burst signal with a high possibility. Thus, based on the degree of the attenuation of the corresponding burst signal of each of the video signals A to D, the attenuation of each video signal A to D can be estimated with sufficient accuracy.

In the present embodiment, the reference value is assigned to the greatest amplitude value of the burst signal among the amplitude values of the burst signals in the video signals A to D; a difference is calculated between the amplitude value of each of the burst signals of the video signals A to D and the reference value. However, there is no need to be limited thereto. For, example, based on a predetermined reference value, a difference may be calculated between the amplitude value of each of the burst signals of the video signals A to D and the reference value. Such a predetermined reference value may be assigned to a value which is estimated to be greater than any amplitude value of the burst signal of each video signal A to D such as an amplitude value prior to the occurrence of the attenuation in signal level due to passage of the corresponding signal cable5.

The amount determination section43determines an amendment amount of each of the analog-state video signals A to D based on the difference in signal level of the video signal A to D estimated in the signal level estimation section42. In detail, the amendment amount is determined such that the video signals A to D are amplified by the same as the differences of the amplitude values of the burst signals of the video signals A to D from the above-mentioned reference value. With respect to the video signal originating from the same camera as the camera from which the burst signal assigned to the reference value originates, the amendment is unnecessary; thus, the amendment amount may be undetermined or determined to be zero (0).

Further, in the present embodiment, the amendment amount is determined such that the video signals A to D are amplified by the same as the differences of the amplitude values of the burst signals of the video signals A to D from the above-mentioned reference value. However, there is no need to be limited thereto. For instance, as long as the amendment amount is determined to make uniform the differences, the amendment amount may be determined so as to amplify the video signals A to D more than the corresponding differences.

The signal amplification section44has an amplifier (AMP), for example. The signal amplification section44amplifies the video signals A to D acquired in the video signal acquisition section41according to the amendment amounts determined in the amendment amount determination section43, and makes uniform the signal levels of the video signals A to D. Thus, the signal amplification section44may be referred to as a unit-side amplification section. With respect to the video signal originating from the same camera as the camera from which the burst signal assigned to the reference value originates, the amendment may be not made or the amendment amount is determined to be zero (0).

The following explains an operation flow in the vehicle circumference monitor apparatus100with respect to the amendments of the video signals of the cameras1ato1dwith reference toFIG. 5.FIG. 5is a flowchart illustrating a video signal amendment process in the vehicle circumference monitor apparatus100. It is noted that the present process is started when the power source of the vehicle circumference monitor apparatus100is turned into an ON state, i.e., when the ignition switch of the subject vehicle is turned into an ON state.

It is further noted that a flowchart or the processing of the flowchart in the present application includes sections (also referred to as steps), which are represented, for instance, as S1. Further, each section can be divided into several sub-sections while several sections can be combined into a single section. Furthermore, each of thus configured sections can be referred to as a means or unit and achieved not only as a software device but also as a hardware device.

First, at S1, a video signal transmission request is made which confirms whether the cameras1ato1dare allowed to output the video signals to the circumference monitor ECU4via the signal cables5; then the processing advances to S2. At S2, at the time when the circumference monitor ECU4comes to be in the state to be able to accept the video signals A to D from the cameras1ato1d, the circumference monitor ECU4sends a transmission permission notice to the cameras1ato1dvia the signal cables5ato5dto permit the output of the video signals A to D. The processing then moves to S3.

At S3, the cameras1ato1doutput the analog video signals of test patterns to the circumference monitor ECU4via the signal cables5ato5d. The processing then moves to S4. At S4, the video signal acquisition section41of the circumference monitor ECU4receives the analog video signal (i.e., each of the analog-state video signals A to D) of the test pattern of each camera1ato1d. The processing then moves to S5.

At S5, the signal level estimation section42of the circumference monitor ECU4compares the amplitude values of the burst signals (for example, color burst signals) of the analog-state video signals A to D with each other. The processing then moves to S6. At S6, the signal level estimation section42of the circumference monitor ECU4assigned the reference value to the greatest amplitude value of the burst signals as the result of the comparison at S5, and designates, as a reference camera, the camera which outputs the burst signal the amplitude value of which is used as the reference value. The processing then moves to S7.

At S7, the amendment amount determination section43determines the amendment amounts, then causing the processing to move to S8. At S8, with respect to the video signals of the cameras1other than the reference camera, the signal amplification section44of the circumference monitor ECU4makes the signal amplification according to the amendment amounts determined at S7(i.e., the video signals of the cameras1other than the reference camera are amended). The present process is then ended.

In the present embodiment, after the cameras1ato1dsend the video signal transmission requests to the circumference monitor ECU4and receives the transmission permission notice from the circumference monitor ECU4, the cameras1ato1doutput the analog video signals of the test patterns to the circumference monitor ECU4. However, there is no need to be limited thereto. For instance, when the power source of the vehicle circumference monitor apparatus100is turned into an ON state, the analog video signal of the test pattern may be outputted to the circumference monitor ECU4from each of the cameras1ato1d.

Returning toFIG. 3. The image processing section45has an ND conversion circuit, for example. The image processing section45transforms the video signals A to D, which are amplified in the signal amplification section44and in the analog state, into the data of the digital signals. Hereinafter, the video signals A to D transformed into the data of the digital signals are referred to as capture images A to D (i.e., digital-state capture images A to D), respectively.

In addition, the image processing section45transforms each of the capture images A to D into a bird's eye view image, which is an image on a ground surface viewed when the ground surface is looked down in a perpendicular direction. The bird's eye view image is obtained as image data of a ground surface coordinate system, which is a coordinate system on a road surface, while designating the installation position of each of the cameras1ato1das a respective viewpoint, by using a well-known coordinate transformation equation. Thus, the image processing section45may be referred to as a bird's-eye view transformation section. Hereinafter, the bird's-eye view images acquired by transforming the capture images A to D are referred to as bird's-eye view images A to D, respectively. Furthermore, in the image processing section45, a required image processing such as lens distortion correction may be first applied to the capture images A to D, which may be then transformed into the bird's-eye view images.

The image combination section46applies a rotation movement and a parallel movement to each of the bird's-eye view images A to D which are obtained in the image processing section45so as to dispose them on a single coordinate plane (i.e., dispose the images A to D so as to be seen as a single image) by using a well-known transformation equation, thereby generating or synthesizing a composite image which combines the bird's-eye view images A to D. Further, when generating the above composite image, the image combination section46operates as follows: (i) reading out an image of a track (for example, an image of a computer graphic illustrating the track) stored in a memory device (unshown); (ii) arranging the read image in a point corresponding to the position of the track; and (iii) combining the track image with the bird's-eye view images A to D. Then, the image combination section46sends drawing data of the generated composite image to the display device2to display the relevant composite data.

It is noted that there may be a case that the cameras1ato1dcannot capture images in the whole of the surrounding areas. In such a case, a bird's-eye view image acquired in the past by the cameras1ato1d(hereinafter, called a history image) may be used for an image which is not viewed presently by the cameras1ato1d, thereby enabling the synthesis of the bird's-eye view image entirely surrounding the track. In this case, the motion of the track may be acquired accurately; the history image may be added to the bird's-eye view images A to D according to the acquired motion of the track, thereby performing the combination of the images. In addition, the motion of the track may be understood by extracting a motion vector using a pattern matching in the image processing and the various sensors such as a vehicle velocity sensor, a steering sensor, and a gyroscope.

The above configuration enables the following. A deviation among the video signals A to D may arise in respect of a signal level due to a difference in the attenuation among the analog signals. The difference in attenuation is caused by a difference in length among the signal cables5ato5d. Even if such a deviation arises, the video signals A to D can be amended to make uniform the signal levels with sufficient accuracy by amplifying the video signals A to D based on the amendment amounts, which are determined so as to make uniform the differences of the amplitude values of the burst signals of the respective video signals A to D. Thus, the composite image which combines the bird's-eye view images A to D originating from the cameras1ato1dcan be displayed in the display device2so as to help prevent the deterioration of the appearance due to the difference in color definition among the bird's-eye view images A to D.

The following explains an effect of the present embodiment specifically usingFIG. 6AandFIG. 6B.FIG. 6Ais a schematic diagram, as a comparative example, for explaining a composite image in cases that the present embodiment is not applied. In contrast,FIG. 6Bis a schematic diagram for explaining a composite image according to the present embodiment. In addition, inFIG. 6AandFIG. 6B, J illustrates a region corresponding to the bird's-eye view image A in the composite image, K illustrates a region corresponding to the bird's-eye view image B in the composite image, L illustrates a region corresponding to the bird's-eye view image C in the composite image, and M illustrates a region corresponding to the bird's-eye view image D in the composite image.

According to an example illustrated inFIG. 2, the length of the signal cable5dwhich connects the circumference monitor ECU4and the rear camera1dis significantly great as compared with the lengths of the other three signal cables5ato5cwhich connect the circumference monitor ECU4with the cameras1a,1b, and1c, respectively. Attenuation in the analog signal via the signal cable5thereby becomes remarkable with respect to the video signal D as compared with video signals A to C. Therefore, when the video images A to D are transformed; without executing the above-mentioned amendment, into the bird's-eye view images A to D, and the composite image which combines the bird's-eye view images A to D is displayed in the display device2, the color definition of the bird's-eye view image D in the region M is significantly inferior to those of the bird's-eye view images A to C in the regions J to K. The appearance of the composite image is degraded as illustrated inFIG. 6A.

In contrast, according to the vehicle circumference monitor apparatus100of the present embodiment, after making uniform the signal levels by executing the above-mentioned amendment, the video images A to D are transformed into the bird's-eye view images A to D, which are combined to generate a composite image; the generated composite image is then displayed in the display device2. As illustrated inFIG. 6B, the deviation in the color definition among the bird's-eye view images A to D in the regions J to M thus does not arise; thereby, the deterioration in the appearance of the composite image can be suppressed.

In the above configuration of the present embodiment, each of the cameras1ato1ddoes not include a component which executes an ND conversion of a video signal while the circumference monitor ECU4includes the component which executes the ND conversion of a video signal. Thus, the cost of the above configuration of the present embodiment can be reduced in comparison with a cost of a configuration in which the component executing the ND conversion of the video signal is included in each of the cameras1ato1d. Furthermore, each camera does not need to include a component executing the ND conversion of the video signal; the miniaturization of the cameras1ato1dbecomes easier.

As a result, while making easier miniaturization of the cameras1ato1dand suppressing the cost more, the deterioration of the appearance of the composite image generated by combining the bird's-eye view images A to D originating from the cameras1ato1dis suppressed to increase a commodity value.

In addition, the vehicle circumference monitor apparatus100according to the present embodiment may be suitably applied to or used in a track, which a carrier body can be attached to and detached from, for a use mode in which the combination of the cameras1ato1dto be used is changed according to the presence or absence of a carrier body. In the above use mode in which the combination of the cameras1ato1dis changed according to the presence or absence of the carrier body, when the carrier body is used, the rear camera out of the four front, rear, right side, and left side cameras for the circumference monitor is attached to a rear portion of the carrier body; in contrast, when the carrier body is not used, the rear camera is attached to a position at the rear of the driver seat.

The following explains a conventional technology. For instance, there is a case that the combination of the cameras1ato1dor the cameras arrangement1to be used is changed according to the presence or absence of the carrier body, and the length of the signal cable which connects a circumference monitor camera and a circumference monitor ECU is also changed. In such a case, the following seems to be necessary to suppress the deterioration in the appearance of the composite image. That is, two kinds of parameters for amendments of the video signals are previously stored in association with the presence or absence of the carrier body; according to the presence or absence of the carrier body, those two kinds of parameters are selectively used properly. In this regard, however, in the foregoing configuration, a component needs to be included which acquires the information on the presence or absence of the carrier body; simultaneously, an additional work needs to be done which specifies two kinds of parameters with respect to each of the different vehicle models having different lengths of the signal cables connecting the circumference monitor ECU with the circumference monitor camera.

In contrast, the vehicle circumference monitor apparatus100of the present embodiment is configured to make uniform the signal levels of the video signals originating from respective in-vehicle cameras, based on the amplitude values of the burst signals of the analog-state video signals which the circumference monitor ECU4actually receives from the cameras for the circumference monitor, enabling the suppression of the deterioration of the appearance of the composite image. Thus, any component which acquires the information on the presence or absence of the carrier body is unnecessary, and any additional work is unnecessary to designate and store a parameter for the amendment of the video signal for every kind of a vehicle model. Therefore, the vehicle circumference monitor apparatus100is excellent in general-purpose properties.

Furthermore, in the mode in which the number and installation positions of cameras for circumference monitor are fixed in a vehicle, the suppression of the deterioration of the appearance of the composite image may be also achieved by previously storing the parameters for the amendment of the video signals according to the length of the signal cable which connects each camera with the circumference monitor ECU. In this regard, however, an additional work needs to be done which specifies two kinds of parameters with respect to each of the different vehicle models having different lengths of the signal cables connecting the circumference monitor ECU with the circumference monitor camera.

In contrast, as explained above, according to the vehicle circumference monitor apparatus100of the present embodiment, the signal levels of the video signals originating from respective in-vehicle cameras are made uniform based on the amplitude value of the burst signal of the analog video signal which the circumference monitor ECU4actually receives from each camera for circumference monitor, enabling the suppression of the deterioration of the appearance of the composite image. Thus, any additional work is unnecessary to designate and store the parameter for the amendment of the video signal for every kind of a vehicle model. With respect to this point, the vehicle circumference monitor apparatus100is therefore excellent in general-purpose properties.

In the above configuration, the video signals A to D are amplified in the signal amplification section44of the circumference monitor ECU4, executing the amendment which makes uniform the signal levels of video signals A to D. Thus, it is not necessary to provide the means for amplifying the video signal to each camera, respectively. Therefore, the cost which provides the means for amplifying the video signals in the whole of to vehicle circumference monitor apparatus100can be held down. In addition, it is not necessary to provide any circuit for amplifying the video signals in the in-vehicle cameras1ato1dor the circumference monitor ECU4; thus, the costs can be held down also. In addition, it is not necessary to provide any circuit for amplifying the video signals in the in-vehicle cameras1ato1d; thus, the configuration of the camera1ato1dcan be simplified, making it easier to use an existing camera. Further, under the above configuration, the flexibility in use of the apparatus becomes higher.

Further, the above-mentioned amendment amount is determined by using the analog signal in the blanking period of the video signal. The analog signal in the blanking period is a signal preceding the signals representing image information, such as a synchronization signal and a burst signal. This enables the following: before displaying the image which image information actually illustrates, the amendment amount is earlier determined so as to make uniform the signal levels of the video signals A to D originating from the cameras1ato1d, enabling the display of the composite image the deterioration of which is suppressed in the appearance.

In the present embodiment, the video signals A to D are amplified in the signal amplification section44of the circumference monitor ECU4so as to execute an amendment to make uniform the signal levels of the video signals A to D. However, there is no need to be limited thereto. For example, the video signals A to D may be amplified in the cameras1ato1dso as to execute an amendment to make uniform the signal levels of the video signals A to D.

The following explains another configuration as a first modification of the foregoing embodiment with reference toFIG. 7andFIG. 8.FIG. 7is a block diagram illustrating a schematic configuration of a circumference monitor ECU4a, as the first modification of the foregoing embodiment, in cases that the cameras1ato1damend the video signals A to D.FIG. 8is a diagram illustrating a schematic configuration of a front camera, as the first modification of the foregoing embodiment, in the case that amendment is made in the camera. To simplify the explanation of the present first modification, an element or component having the same function as that of the element or component explained in the foregoing embodiment is assigned with the same reference number as that in the foregoing embodiment and omitted from the following explanation.

The following explains an outline configuration of the circumference monitor ECU4awith reference toFIG. 7. As illustrated inFIG. 7, the circumference monitor ECU4aincludes the following: the video signal acquisition section41, the signal level estimation section42, the amendment amount determination section43, the image processing section45, an image combination section46, and a control signal transmission section47. It is noted that the circumference monitor ECU4ahas a configuration identical to that of the circumference monitor ECU4except that the signal amplification section44is not included and the control signal transmission section47is included.

The amendment amount determination section43of the circumference monitor ECU4agenerates control signals for amplifying the video signals A to D according to the respective determined amendment amounts, and transmits the generated control signals to the cameras1ato1dvia the control signal transmission section47. More specifically, the control signal for amplifying the video signal A is sent to the front camera1a; the control signal for amplifying the video signal B is sent to the right side camera1b; the control signal for amplifying the video signal C is sent to the left side camera1c; further, the control signal for amplifying the video signal D is sent to the rear camera1d. It is noted that a configuration of the above transmission can be achieved such that the control signal transmission section47transmits to the cameras1ato1dvia the signal cables5ato5d.

The image processing section45of the circumference monitor ECU4atransforms, into the digital-state data, the analog-state video signals A to D, which were amplified by the cameras1ato1daccording to the control signals transmitted from the control signal transmission section47; it then transforms the digital-state data into the bird's-eye view images.

The following explains a schematic configuration of the front camera1ain the case that amendment is made in the camera. As illustrated inFIG. 8, the front camera1acontains a control unit11. It is noted that the control unit11is connected to a power source and GND.

The control unit11has an imaging element such as a CCD element and transforms, into an analog video signal, a light which is received by the imaging element via a wide-angle lens. In addition, when a control signal for amplifying the video signal A according to the amendment amount is transmitted from the control signal transmission section47of the circumference monitor ECU4a, the control unit11receives the control signal. According to this control signal, the control unit11amplifies using an amplifier (AMP) the analog video signal (i.e., analog-state video signal A), which is acquired by transformation with the imaging element. The control unit11outputs the analog video signal amplified by the AMP to the circumference monitor ECU4avia the signal cable5a. Therefore, the control unit11may be referred to as a camera-side amplification section.

It is noted that before the time when the above-mentioned control signal is transmitted from the control signal transmission section47, the control unit11outputs directly the analog video signal acquired by the transformation with the imaging element, to the circumference monitor ECU4avia the signal cable5a, without amplifying it using the AMP.

In addition, the above explanation is made as an example using the front camera1a. Similarly, with respect to the cameras1bto1d, the analog video signal is amplified according to the control signal transmitted from the control signal transmission section47, thereby amending the signal levels of the analog-state video signals A to D to become uniform.

In the foregoing embodiment, the amplitude value of the burst signal is used for the signal level estimation section42to estimate the difference among the video signals A to D. However, there is no need to be limited thereto. For example, another alternative configuration may use a amplitude value of an analog signal other than the burst signal in the blanking period, such as a synchronization signal; further, another configuration may use an amplitude value (for example, a maximum amplitude value, an average value of amplitude values) representing image information such as a brightness signal, a color signal. Further, a signal amplitude level may include an amplitude value, a maximum amplitude value, an average value of amplitude values.

Further, in the foregoing embodiment, the signal level estimation section42estimates a difference in signal level among the video signals A to D; the amendment amount determination section43determines an amendment amount based on the result of the estimation. However, there is no need to be limited thereto. For example, based on the amplitude values of the burst signals of the video signals A to D acquired by the video signal acquisition section41, the amendment amount determination section43may determine an amendment amount with reference to a predetermined table.

The above configuration is explained with reference toFIG. 9as a second modification according to the embodiment.FIG. 9is a block diagram illustrating a schematic configuration of a circumference monitor ECU4bin the second modification (i.e., in cases that an amendment amount is determined using a table). To simplify the explanation of the present modification, an element or component having the same function as that of the element or component explained in the foregoing embodiment is assigned with the same reference number as that in the foregoing embodiment and omitted from the following explanation.

As illustrated inFIG. 9, the circumference monitor ECU4bincludes the video signal acquisition section41, the amendment amount determination section43, the signal amplification section44, the image processing section45, the image combination section46, and a table storage section48. It is noted that the circumference monitor ECU4bhas a configuration identical to that of the circumference monitor ECU4except that the signal level estimation section42is not included and the table storage section48is included.

The table storage section48stores a table which previously associates an amplitude value of a burst signal with an amendment amount. It is noted that the table associates an amplitude value of a burst signal with an amendment amount such that the smaller the amplitude value of the burst signal is, the larger the amendment amount (i.e., an amplification amount of a video signal) is. More specifically, the association is made such that as the amendment amount is small, the amplitude value of the burst signal is large in inverse proportion; the differences in attenuation degree among the video signals A to D of the cameras1ato1dcan be made up by the amendment amounts.

The amendment amount determination section43of the circumference monitor ECU4brefers to the above table stored in the table storage section48based on the amplitude values of the burst signals of the video signals A to D acquired in the video signal acquisition section41, and determines an amendment amount according to the amplitude value.

In the present modification, the table stored in the table storage section48is referred to using the amplitude value of the burst signal. However, there is no need to be limited thereto. For example, another alternative configuration may use a amplitude value of an analog signal other than the burst signal in the blanking period, such as a synchronization signal. another configuration may use an amplitude value (for example, a maximum amplitude value, an average value of amplitude values) showing image information such as a brightness signal, a color signal.

Further, in the foregoing embodiment, the ON and OFF manipulations of the assist start switch3cause the circumference monitor control to start and stop, respectively. However, there is no need to be limited thereto. For example, suppose the case that the circumference monitor control is started at the time of back parking. In this case, the circumference monitor ECU4may start the circumference monitor control when determining that the shift position becomes at a reversed “R” under a predetermined velocity (for example, 10 km/h), based on the velocity of the subject vehicle detected by the vehicle velocity sensor or the vehicle wheel velocity sensor and the shift position detected by the shift position sensor. In addition, the circumference monitor control may be stopped when determining that the shift position becomes at the parking “P.”

Further, suppose the case that the circumference monitor control is started at the time of turning right/left or changing traffic lanes. In this case, when the predictive information on turning right/left or changing traffic lanes is detected by a winker switch, the circumference monitor control may be started. In addition, in such a case, when it is detected that the winker switch is turned off, the circumference monitor control may be stopped.

Further, suppose the case that the circumference monitor control is started at the time of starting-off from the parking lot. In this case, when it is detected that the shift position is switched into the drive “D” or reverse “R” from the parking “P” by the shift position sensor, the circumference monitor control may be started. In addition, in such a case, when the velocity of the subject vehicle detected by the vehicle velocity sensor or the vehicle wheel velocity sensor becomes greater than a predetermined velocity (for example, 10 km/h), the circumference monitor control may be stopped.

In the foregoing embodiment, the case that the vehicle circumference monitor apparatus100is mounted in a track is explained as an example. Without need to be limited thereto, it can be mounted in a vehicle other than the track.

Now, the problem may be defined as follows. The differences in length among the signal cables5ato5dtransmitting analog-state video signals result in deviations in attenuation degree among the analog-state video signals. Such deviations result in differences in color definition among the images originating from the cameras1ato1d. Such differences are defined as the problem. It is noted that such a problem arises more significantly as the size of the vehicle becomes larger to cause the installation positions of the cameras to be separated farther from each other. It is thereby more desirable that the vehicle circumference monitor apparatus100is mounted in a large-sized vehicle.

For instance, if the vehicle circumference monitor apparatus100according to the present embodiment is mounted in a middle-sized vehicle larger than a standard-sized vehicle, an effect of suppressing the deterioration of the appearance of the composite image formed by combining the images originating from the individual in-vehicle cameras1ato1dbecomes more remarkable. It is thereby more desirable that the vehicle circumference monitor apparatus100is mounted in a middle-sized vehicle, such as a minibus, larger than a standard-sized vehicle. In addition, if the vehicle circumference monitor apparatus100is mounted in a large-sized vehicle such as a track and a motor coach (i.e., bus), an effect of suppressing the deterioration of the appearance of the composite image formed by combining the images originating from the individual in-vehicle cameras1ato1dbecomes much more remarkable. It is thereby much more desirable that the vehicle circumference monitor apparatus100is mounted in a large-sized vehicle. It is noted that the above mentioned standard-sized vehicle, middle-sized vehicle, and large-sized vehicle may be classifications of vehicles in a road traffic law in each nation.

Further, in the foregoing embodiment, several images of camera coordinate system are transformed into bird's-eye view images; the bird's-eye view images are combined to generate a composite image; the generated composite image is displayed in the display device2. However, there is no need to be limited thereto. For example, several images of the camera coordinate system may be combined, without changing into the bird's-eye view image, to generate a composite image; the generated composite image may be thus displayed in the display device2.

Further, in the foregoing embodiment, the cameras1ato1duse color cameras of NTSC system. However, there is no need to be limited thereto. For example, color cameras of another system may be used; alternatively, monochrome cameras may be used.

Further, in the foregoing embodiment, the vehicle circumference monitor apparatus100is provided with four cameras1ato1d. Without need to be limited thereto, the vehicle circumference monitor apparatus100may have another configuration to have the cameras arrangement1having cameras, the number of which is other than four.

Each or any combination of processes, functions, sections, steps, or means explained in the above can be achieved as a software section or unit (e.g., subroutine) and/or a hardware section or unit (e.g., circuit or integrated circuit), including or not including a function of a related device; furthermore, the hardware section or unit can be constructed inside of a microcomputer.

Furthermore, the software section or unit or any combinations of multiple software sections or units can be included in a software program, which can be contained in a non-transitory computer-readable storage media or can be downloaded and stored in a non-transitory computer-readable storage media via a communications network.

Aspects of the disclosure described herein are set out in the following clauses.

As an aspect of the disclosure, a vehicle circumference monitor apparatus in a vehicle provided as follows. A plurality of in-vehicle cameras are arranged such that at least a part of a capture target of one in-vehicle camera does not overlap with a capture target of an other camera. Each of the in-vehicle cameras captures an image of a vehicle circumferential area outside of the vehicle and outputs an analog-state video signal of the captured image via a corresponding signal cable. An electronic control unit is included to have an image combination section to generate a composite image by a combination to combine images originating from the in-vehicle cameras based on video signals inputted via the signal cables from the in-vehicle cameras. A display device is, included to display the composite image generated by the image combination section. Herein, the electronic control unit further includes an amendment amount determination section to determine an amendment amount with respect to the analog-state video signal originating from each of the in-vehicle cameras based on analog signals included in the analog-state video signals inputted via the signal cables from the in-vehicle cameras, in order to make uniform signal levels of the analog-state video signals originating from the respective in-vehicle cameras.

Further, as an optional aspect of the disclosure, the video signal may be amplified by the electronic control unit; thereby, it is not necessary to provide each in-vehicle camera with the means for amplifying the video signal each. Therefore, the cost which provides the means for amplifying the video signals in the whole apparatus can be held down. In addition, it is not necessary to provide each in-vehicle camera or the electronic control unit with any circuit for amplifying the video signals in each in-vehicle camera; thus, the costs can be held down also. In addition, it is not necessary to provide each in-vehicle camera with any circuit for amplifying the video signals in each in-vehicle camera; thus, the configuration of the camera or camera unit can be simplified more, making easier to use an existing camera. Further, under the above configuration, the flexibility of the apparatus becomes higher.

As an optional aspect of the disclosure, the electronic control unit may transmit a control signal to each in-vehicle camera; the control signal is used to amplify a video signal, which is to be outputted via the corresponding signal cable from each in-vehicle camera, according to the amendment amount determined by the amendment amount determination section. The video signal is thus amplified in the in-vehicle camera, thereby making uniform the signal levels of the video signals outputted via the signal cables from the several in-vehicle cameras.

The disadvantage of the difference in definition among the several images, which originate from the several in-vehicle cameras, arises from the variation in attenuation of the analog-state video signals resulting from the difference in length among the signal cables which send the video signals. Such a disadvantage arises more significantly as the size of the vehicle becomes larger to cause the installation positions of the cameras to be separated farther from each other. As an optional aspect of the disclosure, if the vehicle circumference monitor apparatus may mounted in a vehicle larger than a standard-sized vehicle, an effect of suppressing the deterioration of the appearance of the composite image formed by combining the images originating from the several in-vehicle cameras becomes more remarkable.

Furthermore, if the vehicle circumference monitor apparatus according is mounted in a large-sided vehicle, an effect of suppressing the deterioration of the appearance of the composite image formed by combining the images originating from the several in-vehicle cameras becomes much more remarkable.

Further, as an optional aspect of the disclosure, the electronic control unit may include a bird's-eye view transformation section which transforms an image, which is represented by a video signal inputted via a signal cable from an in-vehicle camera, into a bird's-eye view image which is an image on a ground level glanced down perpendicularly from an upper position. The image combination section may combine the bird's-eye view images, which originate from the several in-vehicle cameras and obtained by the bird's-eye view transformation section to generate or synthesize a composite image.

In order to make uniform the signal levels of the video signals originating from respective in-vehicle cameras, an amendment amount is determined with respect of each video signal'originating from each in-vehicle camera based on analog signals inputted via the cables from several in-vehicle cameras. Such an amendment amount may be determined in the following manners, for instance.

As an optional aspect of the disclosure, the electronic control unit may estimate the difference in signal level among the video signals originating from the respective in-vehicle cameras based on analog signals inputted via the cables from several in-vehicle cameras, and determine the amendment amount based on the estimated difference in signal level.

Further, in the above, a reference signal level may be defined as the largest signal level among those of the respective analog signals inputted via the signal cables from the several in-vehicle cameras. The difference from the reference signal level may be calculated for each of the signal levels of the analog signals inputted via the corresponding signal cables from the several in-vehicle cameras. The calculated difference may be estimated as a difference in signal level of the video signal originating from each in-vehicle camera; the amendment amount may be determined according to the calculated above difference.

Furthermore, as an optional aspect of the disclosure, the electronic control unit may include a table storage section which stores a table which previously associates the amendment amount and the signal level of the analog signal inputted via the signal cable from each of the several in-vehicle cameras. The amendment amount determination section may refer to the table stored in the table storage section based on analog signals inputted via the cables from several in-vehicle cameras, thereby determining the amendment amount.

Further, as an optional aspect of the disclosure, the above-mentioned amendment amount may be determined using an analog signal in the blanking period of the video signal. The analog signal in the blanking period may be a signal such as a synchronization signal or a burst signal, which precedes a signal for expressing an image. Thus, before actually displaying the composite image, the amendment amount can be determined and the video signal originating from each in-vehicle camera can be amended. This enables the display of the composite image the deterioration of which is suppressed in the appearance.

In the above, the burst signal may be used as an analog signal in the blanking period. The amendment amount may be thereby determined to make uniform the signal levels of the video signals originating from the respective in-vehicle cameras.