JP2014021716A - Sign guidance display device and sign guidance display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sign guidance display device and a sign guidance display method, which are capable of securing color reproducibility of the guide image of a road sign, the guide image generated on the basis of a pickup image.SOLUTION: A sign guidance display device includes: an on-vehicle camera 2; means 4 for controlling a shutter speed of the camera at a normal speed; means 5 for detecting a road sign on the basis of a pickup image picked up by the on-vehicle camera 2 at a normal speed; the means 4 for controlling a shutter speed at a high speed using the detection by the means 5 as a trigger; means 6 for cut out an image of the road sign from a pickup image picked up with the shutter speed controlled at a high speed, to discriminate a foreground portion from a background portion; the means 4 for controlling the shutter speed at a low speed after the cutting-out; means 7 for determining a chromatic color of the road sign on the basis of a pickup image with the shutter speed controlled at a low speed; and means 8 for synthesizing the chromatic color to the foreground portion/background portion, and generating and displaying a guidance image.

Description

  The present invention relates to a sign guide display device and a sign guide display method, and more particularly to a sign guide display device and a sign guide display method suitable for guide display of a road sign.

  Conventionally, in an in-vehicle device, a road sign is image-recognized based on an image captured by an in-vehicle camera. For example, such a road sign image recognition outputs an alarm according to a recognition result. It has been used to call attention to safe and legal driving (see, for example, Patent Documents 1 and 2).

JP 2008-197769 A Special table 2010-515184 gazette

  By the way, the in-vehicle camera gives priority to the sensitivity over the color appearance for the purpose of increasing the sensitivity especially at night, so it is difficult to recognize the color of the road sign based on the captured image at night. It has the disadvantages.

  For this reason, when trying to guide and display a road sign recognized (generated) based on a captured image at night on the in-vehicle monitor, the original color of the road sign may not be appropriately reproduced.

  Regarding this point, in Patent Document 1, the original blue portion of the road sign is determined by reducing the R value from the nighttime image.

  Further, in Patent Document 2, a traffic sign is found based on the first image information received from the camera, and the second image information obtained by photographing the found traffic sign with high contrast is used. On the basis of which traffic signs are identified.

  However, the color determination in Patent Document 1 is performed for pattern matching, and is not intended to ensure color reproducibility when displaying and displaying road signs.

  Further, in Patent Document 2, although it is possible to increase the shutter speed of the camera and ensure the recognition accuracy of characters and figures of traffic signs, it is not possible to ensure color reproducibility.

  Therefore, the present invention has been made in view of such points, and can ensure the color reproducibility of the road sign guide image generated based on the captured image, and thus does not rely on the navigation function. It is an object of the present invention to provide a sign guide display device and a sign guide display method that allow a user to accurately grasp a road sign ahead.

  In order to achieve the above-described object, a sign guide display device according to the present invention is a sign guide display device that is mounted on a vehicle and guides and displays a road sign on a display unit. An in-vehicle camera that captures an image of the area, a first control unit that controls a shutter speed of the in-vehicle camera to a predetermined normal speed, and the shutter speed controlled to the normal speed by the first control unit. Detection means for detecting the road sign based on a captured image of the in-vehicle camera and second control for changing the shutter speed from the normal speed to a predetermined high speed when triggered by detection of the road sign by the detection means The detection means is detected from the captured image in a state where the shutter speed is controlled to be changed to the high speed by the control means and the second control means. The road sign image is cut out, and after the road sign image is cut out by the background / foreground discrimination means for discriminating the cut out image of the road sign into a background part and a foreground part, Third detection means for changing the shutter speed from the high speed to a predetermined low speed, and the detection based on the captured image in a state where the shutter speed is changed to the low speed by the third control means. Color determining means for determining a chromatic color arranged on the road sign, and combining the chromatic color determined by the color determining means with the background portion or the foreground portion determined by the background / foreground determining means A guidance display means for generating a guidance image of the detected road sign and displaying the generated guidance image on the display unit. It is characterized in that was.

  The sign guide display method according to the present invention is a sign guide display method for guiding and displaying a road sign on a display unit of an in-vehicle device, and a shutter speed of an in-vehicle camera that images a predetermined imaging area in front of the vehicle. The road sign is detected on the basis of a first step of controlling the vehicle speed to a predetermined normal speed and a captured image of the in-vehicle camera in a state where the shutter speed is controlled to the normal speed in the first step. A second step, a third step of changing the shutter speed from the normal speed to a predetermined high speed, triggered by the detection of the road sign in the second step, and the shutter in the third step. The image of the road sign detected in the second step is cut out from the captured image in a state where the speed is changed to the high speed. A fourth step of discriminating the clipped image of the road sign into a background portion and a foreground portion; and after the cutout of the road sign image in the fourth step, the shutter speed is changed from the high speed to a predetermined low speed. And a chromatic color arranged on the detected road sign based on the captured image in a state where the shutter speed is changed and controlled to the low speed in the fifth step. A sixth step of determining, and combining the chromatic color determined in the sixth step with the background portion or the foreground portion determined in the fourth step, thereby detecting the detected road sign. And a seventh step of generating a guide image and displaying the generated guide image on the display unit.

  According to the present invention as described above, based on a captured image captured under a high shutter speed, a road sign image in which characters and figures are accurately reflected is cut out and a background portion of the road sign is extracted. Appropriately determine the foreground part, and then accurately determine the chromatic color that is colorized on the road sign based on the captured image captured under the low-speed shutter, and thus properly determine A road sign guide image can be generated by synthesizing the accurately determined chromatic color in the background portion or the foreground portion. As a result, the color reproducibility of the road sign guide image generated based on the captured image can be ensured, and the user can accurately grasp the road sign ahead without relying on the navigation function. .

  Further, in the sign guide display device of the present invention, the background / foreground discrimination means performs binarization processing on the clipped road sign image, and then displays the binarized road sign image. The background part and the foreground part used are discriminated, and the guidance display means turns the black color by the binarization processing of the background part and the foreground part into the determined chromatic color. You may synthesize.

  According to such a configuration, the background portion and the foreground portion can be easily determined, and the determined chromatic color can be accurately arranged on the road sign image. The color reproducibility can be further ensured while improving the speed.

  Furthermore, in the sign guide display device of the present invention, the guide display means may assign white as it is to the other of the background portion and the foreground portion that has become white due to the binarization process.

  According to such a configuration, a road sign whose character / graphic part or background part is white can be displayed simply and quickly with an accurate color scheme.

  In the sign guide display device of the present invention, when the sensitivity of the in-vehicle camera is increased by the change control by the third control unit, the sensitivity improvement unit further improves the sensitivity by image processing on the captured image. May be provided.

  And according to such a configuration, when imaging at a low shutter speed, by further improving the sensitivity of the in-vehicle camera by image processing, the color determination of the road sign can be performed with higher accuracy, As a result, the color reproducibility of the guide image can be further improved.

  Further, in the sign guide display device according to the present invention, the background / foreground discrimination means is configured such that after the shutter speed is changed to the high speed, the vehicle displays the road sign with respect to the detected road sign. In this case, the background portion and the foreground portion may be determined based on the captured image at the time of detection after detecting that the distance has been approached to be sufficiently illuminated. Similarly, in the sign guide display method according to the present invention, the fourth step includes a step in which the vehicle places a headlamp on the detected road sign after the shutter speed is changed to the high speed. 4-1 for detecting that a distance close to a distance that can be sufficiently illuminated is detected, and the background portion and the foreground portion based on the captured image at the time of detection in the step 4-1 And a 4-2 step of performing the determination.

  Further, according to the present invention, the background portion and the foreground portion can be more reliably determined based on the image captured at a high shutter speed in a sufficiently bright state, so that a higher quality guide is provided. An image can be obtained.

  Furthermore, in the sign guide display device of the present invention, the background / foreground determining means may determine the distance from the vehicle to the road sign based on the size of the detected road sign image. Good.

  According to such a configuration, it is possible to easily grasp the determination timing of the background portion and the foreground portion based on the size of the road sign image, so that the processing and the configuration can be prevented from becoming complicated. .

  The sign guide display device of the present invention may be mounted on an in-vehicle AV device that does not have a navigation function.

  And according to such a structure, it can respond effectively to what is called display audio these days.

  According to the present invention, the color reproducibility of a road sign guide image generated based on a captured image can be ensured, and as a result, the user can accurately grasp the road sign ahead without relying on the navigation function. be able to.

The block diagram which shows the sign guide display apparatus in 1st Embodiment of this invention. The schematic diagram which shows the operation example of a sign guide display apparatus in 1st Embodiment of this invention. The flowchart which shows the sign guide display method in 1st Embodiment of this invention. The block diagram which shows the sign guide display apparatus in 2nd Embodiment of this invention. The flowchart which shows the sign guide display method in 2nd Embodiment of this invention.

(First embodiment)
(Sign guide display device)

  Hereinafter, a first embodiment of a sign guide display device according to the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the sign guide display device 1 according to the present embodiment includes an in-vehicle camera 2 that images a predetermined imaging area in front of the vehicle. This in-vehicle camera 2 is an in-vehicle or out-of-vehicle camera that sequentially images a forward imaging area that changes as the vehicle moves at a set shutter speed (in other words, exposure time), such as a CCD or CMOS. It may be a digital camera provided with a solid-state image sensor.

  As shown in FIG. 1, the sign guide display device 1 includes a captured image acquisition unit 3. Data of a captured image captured by the in-vehicle camera 2 is input (acquired) to the captured image acquisition unit 3.

  Furthermore, as shown in FIG. 1, the sign guide display device 1 has a control unit 4. The control unit 4 functions as first control means, and controls the shutter speed of the in-vehicle camera 2 to a predetermined normal speed. It should be noted that such a trigger for control to the normal speed is caused by the fact that the outside of the vehicle has been determined to be nighttime by detecting outside light by a dimmer sensor (not shown) while the vehicle is traveling, or the road sign generated last time It may be that the period during which the guide image is to be displayed has ended. Moreover, the control at this time may be accompanied by start-up control of the vehicle-mounted camera 2. Further, the normal speed may be a common-sense shutter speed that is set when performing LDW (Lane Departure Warning) using a vehicle-mounted camera 2 that has been conventionally used, or forward vehicle recognition.

  Furthermore, as shown in FIG. 1, the sign guide display device 1 has a road sign detection unit 5 as detection means. When this road sign detection unit 5 detects that the shutter speed of the in-vehicle camera 2 is controlled to the normal speed by the control unit 4 (first control means), for example, by a notification from the control unit 4, the normal speed is detected. A captured image of the in-vehicle camera 2 in the control state (hereinafter referred to as a normal speed captured image) is acquired from the captured image acquisition unit 3. And the road sign detection part 5 detects a road sign based on the acquired normal-speed captured image. At this time, the road sign detection unit 5 may detect the road sign by extracting the outline of the road sign (in other words, the edge) based on the luminance difference in the normal-speed captured image.

  Further, when the control part 4 detects that the road sign is detected by the road sign detection part 5 by, for example, a notification from the road sign detection part 5, the control part 4 functions as a second control unit. It has become. In the function as the second control means, the control unit 4 controls to change the shutter speed of the in-vehicle camera 2 from the normal speed to a predetermined high speed.

  Further, as shown in FIG. 1, the sign guide display device 1 has a background / foreground determination unit 6 as background / foreground determination means. When the background / foreground determination unit 6 detects that the in-vehicle camera 2 shutter speed has been controlled to be changed at high speed by the control unit 4 (second control means), for example, by notification from the control unit 4, the change control is performed. A captured image (hereinafter referred to as a high-speed captured image) of the in-vehicle camera 2 in the state is acquired from the captured image acquisition unit 3. Then, the background / foreground discrimination unit 6 cuts out the road sign image detected by the road sign detection unit 5 from the acquired high-speed captured image, and extracts the extracted road sign image as the background part and the foreground part. Are distinguished (in other words, classified).

  Furthermore, the control unit 4 notifies the background / foreground determination unit 6 that the background / foreground determination unit 6 cut out the road sign image or determined the background / foreground part based on the image, for example. When this is detected, it functions as a third control means triggered by this. In the function as the third control means, the control unit 4 changes the shutter speed of the in-vehicle camera 2 from a high speed to a predetermined low speed (a speed lower than the normal speed).

  As shown in FIG. 1, the sign guide display device 1 includes a color determination unit 7 as a color determination unit. When the color determination unit 7 detects that the shutter speed of the in-vehicle camera 2 is changed to the low speed by the control unit 4 (third control means), for example, by a notification from the control unit 4, the change control state A captured image of the in-vehicle camera 2 (hereinafter referred to as a low-speed captured image) is acquired from the captured image acquisition unit 3. And the color determination part 7 determines the chromatic color currently arranged by the road sign detected by the road sign detection part 5 based on the acquired low-speed captured image. For this determination, the signal values (R, G, B) of the pixels corresponding to the road sign may be used, and various other known color recognition techniques may be used.

  Furthermore, as shown in FIG. 1, the sign guide display device 1 has a guide display processing unit 8 as a guide display means. The guidance display processing unit 8 includes data indicating the determination result of the background / foreground part by the background / foreground determination unit 6 and the data indicating the determination result of the color determination unit 7 as the background / foreground determination unit 6 and the color determination unit. 7 is input. Based on these input data, the guidance display processing unit 8 is detected by combining the chromatic color determined by the color determination unit 7 with the background portion or foreground portion determined by the background / foreground determination unit 6. A road sign guide image is generated. The guidance display processing unit 8 displays the generated guidance image on the display unit 9.

  According to such a configuration, based on the high-speed captured image, a road sign image in which characters and figures are accurately reflected is cut out to appropriately determine the background portion and the foreground portion of the road sign, and then the low-speed imaging is performed. Based on the image, the chromatic color arranged on the road sign is accurately determined, and the chromatic color accurately determined on the background part or the foreground part appropriately determined in this way is combined to be the road sign. The guide image can be generated. As a result, the color reproducibility of the road sign guide image generated based on the captured image can be ensured, and the user can accurately grasp the road sign ahead without relying on the navigation function (sign guide function). be able to.

  In addition to the above-described configuration, in the present embodiment, the background / foreground determination unit 6 performs binarization processing on the road sign image cut out from the high-speed captured image, and the road sign after the binarization processing is performed. Using the image, the above-described background portion and foreground portion are discriminated. Here, in the binarization processing, the luminance values of pixels whose luminance values exceed a predetermined threshold in the road sign image are all unified to a value corresponding to white (for example, “255” in 8-bit expression). In addition, the luminance values of the pixels whose luminance values are less than the threshold value are unified to a value corresponding to black (for example, “0”). Then, the background / foreground recognition unit 6 determines a pixel group corresponding to one of white and black (for example, black) unified by such binarization processing as a background portion, and the other (for example, white). The pixel group corresponding to is determined as the foreground portion. Further, in the present embodiment, the guidance display processing unit 8 performs color determination on one of the background portion and the foreground portion thus determined by the background / foreground determination portion 6 that has become black due to the binarization processing. The chromatic colors determined by the unit 7 are combined.

  According to such a configuration, the background portion and the foreground portion can be easily determined, and the determined chromatic color can be accurately arranged on the image of the road sign. As a result, the color reproducibility can be more appropriately ensured.

  In addition to the above-described configuration, in the present embodiment, the guidance display processing unit 8 further includes the background part and the foreground part determined by the background / foreground determining part 6 on the other side that has become white due to the binarization process. White color is assigned as it is.

  According to such a configuration, a road sign whose character / graphic part or background part is white can be displayed simply and quickly with an accurate color scheme.

  In addition to the above-described configuration, in the present embodiment, the background / foreground discrimination unit 6 further detects the vehicle with respect to the road sign detected by the road sign detection unit 5 after the shutter speed is changed to high speed by the control unit 4. Detecting that the road sign has been approached to a predetermined distance that can be sufficiently illuminated by the headlamp, and determining the background portion and the foreground portion based on the high-speed captured image at the time of detection It has become.

  According to such a configuration, the background portion and the foreground portion can be more reliably recognized based on the high-speed captured image captured in a sufficiently bright state, so that a higher-quality guide image can be obtained. .

  In addition to the above-described configuration, in the present embodiment, the background / foreground determination unit 6 further determines whether the vehicle is based on the size of the road sign image detected by the road sign detection unit 5 (for example, the number of occupied pixels). Is determined to have reached the predetermined distance.

  According to such a configuration, it is possible to easily grasp the discrimination timing of the background portion and the foreground portion based on the size of the road sign image, so that the processing and the configuration can be prevented from becoming complicated.

  In addition, each of the above-described components 3 to 8 of the sign guide display device 1 is a program storage such as a RAM that is used for temporary storage of data and a ROM that stores a program for realizing the functions of the components 3 to 8. The present invention may be embodied by a device, an arithmetic processing unit such as a CPU that executes a program stored in the program storage device, or the like.

  Next, FIG. 2 is a schematic diagram illustrating an operation example in the present embodiment.

  That is, FIG. 2A shows a state where a road sign is detected based on a normal speed captured image captured at a normal shutter speed. A broken line frame f surrounding the road sign in FIG. 2A is a detection frame f indicating that the road sign is detected. The detection frame f may be displayed on the display unit 10 together with the captured image.

  Next, FIG. 2B shows that a high-speed captured image is taken when the vehicle approaches a road sign and reaches a predetermined distance after the shutter speed is changed to a high speed from the state of FIG. -Indicates the displayed state.

  Next, FIG. 2 (c) shows that the road sign image detected in FIG. 2 (a) is cut out from the high-speed captured image captured in FIG. 2 (b), and the background portion and foreground are obtained by binarization processing. A state determined as a part is shown. In FIG. 2C, the image portion corresponding to the black portion by the binarization processing is determined as the background portion, and the image portion corresponding to the white portion by the binarization processing is the foreground portion. Has been determined. At this time, since the road sign image is cut out from the high-speed captured image, so-called apparent sensitivity is low, but the resolution is high, and characters and figures in the road sign are clearly reflected, The background portion and the foreground portion can be appropriately determined.

  Next, FIG. 2 (d) shows that after the image of the road sign in FIG. 2 (c) is cut out, the shutter speed is changed to a low speed, and the vehicle further approaches the road sign, resulting in a low speed. The captured image is captured and displayed.

  Next, FIG. 2E shows a state in which the chromatic color “blue” arranged on the road sign is determined based on the low-speed captured image captured in FIG. At this time, the low-speed captured image has a low resolution and is blurred or blurred, but has a high apparent sensitivity, and thus reflects the color of the actual road sign faithfully. For this reason, accurate color determination can be performed.

  Finally, in FIG. 2 (f), blue determined in FIG. 2 (e) is combined with the background portion (black) determined in FIG. 2 (c), and also determined in FIG. 2 (c). The guide image is generated and displayed by assigning white to the foreground part (white) as it is. This guidance image may be displayed in a superimposed manner on the actual captured image display screen. At this time, the guide image is obtained by combining the chromatic color accurately determined in FIG. 2 (e) with the background portion appropriately determined in FIG. 2 (c), so that the color reproducibility is good. It is an image. Such a guidance image may be continuously displayed during a predetermined period (for example, until the road sign is not detected from the captured image).

(Sign guide display method)

  Next, a first embodiment of a sign guide display method according to the present invention to which the above-described sign guide display device 1 is applied will be described with reference to FIG.

  In this embodiment, first, in step 1 (ST1) of FIG. 3, the shutter speed of the in-vehicle camera 2 is set to a normal speed, triggered by the occurrence of a trigger such as nighttime detection, under the control of the control unit 4.

  Next, in step 2 (ST2), the road sign detection unit 5 determines whether a road sign is present in the normal speed captured image. If a positive determination result is obtained in step 2 (ST2), the process proceeds to step 3 (ST3). If a negative determination result is obtained, step 2 (ST2) is repeated.

  Next, in step 3 (ST3), the shutter speed of the in-vehicle camera 2 is changed to a high speed under the control of the control unit 4.

  Next, in step 4 (ST4), the vehicle has reached a predetermined distance to the road sign based on the size of the road sign image detected in step 2 (ST2) by the background / foreground discrimination unit 6. It is determined whether or not. If a positive determination result is obtained in step 4 (ST4), the process proceeds to step 5 (ST5). If a negative determination result is obtained, step 4 (ST4) is repeated.

  Next, in step 5 (ST5), the background / foreground discrimination unit 6 cuts out the road sign image detected in step 2 (ST2) from the high-speed captured image, and the cut-out image is divided into the background portion and the foreground portion. To determine.

  Next, in step 6 (ST6), the shutter speed of the in-vehicle camera 2 is changed to a low speed under the control of the control unit 4.

  Next, in step 7 (ST7), the color determination unit 7 determines a chromatic color arranged on the road sign detected in step 2 (ST2) based on the low-speed captured image.

  Next, in step 8 (ST8), the guidance display processing unit 8 performs step 2 (ST5) based on the determination result of the background / foreground part in step 5 (ST5) and the determination result of chromatic color in step 7 (ST7). A guide image of the road sign detected in ST2) is generated and displayed, and the process is terminated.

(Second Embodiment)

  Next, a second embodiment of the present invention will be described with reference to FIG. 4 and FIG. 5 with a focus on differences from the first embodiment.

  The difference between the sign guidance display device 21 in the present embodiment and the first embodiment is that a sensitivity improving unit 22 as a sensitivity improving means is provided.

  Here, the sensitivity improving unit 22 is slow when the apparent sensitivity of the in-vehicle camera 2 is increased due to the low shutter speed of the in-vehicle camera 2 under the control of the control unit 4 (third control means). The sensitivity is further improved by image processing on the captured image. Examples of the image processing include integration of low-speed captured images for a plurality of frames that are adjacent to each other, addition of adjacent pixels in the low-speed captured images of the same frame, and the like.

  Then, the color determination unit 7 determines the chromatic color arranged on the road sign detected by the road sign detection unit 5 based on the low-speed captured image after the image processing by the sensitivity improvement unit 22. It has become.

  In the sign guide display method according to this embodiment, the sensitivity is further improved by the sensitivity improving unit 22 between Step 6 (ST6) and Step 7 (ST7) in the first embodiment (ST9). Execute.

  According to the present embodiment, when the image is captured at a low shutter speed, the sensitivity of the in-vehicle camera 2 is further improved by image processing, so that the color determination of the road sign can be performed with higher accuracy. The color reproducibility of the guide image can be further improved.

  In addition, this invention is not limited to embodiment mentioned above, You may change variously in the limit which does not impair the characteristic of this invention.

  For example, the sign guide display devices 1 and 21 of the present invention may be mounted on an in-vehicle AV device that does not have a navigation function.

  Further, depending on the configuration of the road sign, the black portion by the binarization process may be the foreground portion, and the white portion may be the background region.

  Further, whether the background portion or the foreground portion should be determined may be determined based on the arrangement state of the binarized pixel values. For example, a pixel group having the same binarized pixel value that fills the periphery (near the contour) of the road sign in a frame shape, and a pixel group having the same binary pixel value arranged at a position different from these pixel groups For the pixel group having the same binary pixel value arranged so as to be divided into a plurality of parts on the center side of the road sign, these may be determined as the foreground part. .

DESCRIPTION OF SYMBOLS 1 Sign guidance display apparatus 2 Car-mounted camera 4 Control part 5 Road sign detection part 6 Background / foreground discrimination part 7 Color judgment part 8 Guide display processing part 10 Display part

Claims (9)

A sign guide display device mounted on a vehicle for displaying a road sign on a display unit,
An in-vehicle camera that images a predetermined imaging area in front of the vehicle;
First control means for controlling the shutter speed of the in-vehicle camera to a predetermined normal speed;
Detecting means for detecting the road sign based on a captured image of the vehicle-mounted camera in a state where the shutter speed is controlled to the normal speed by the first control means;
Triggered by detection of the road sign by the detection means, second control means for controlling the shutter speed to be changed from the normal speed to a predetermined high speed;
The image of the road sign detected by the detection means is cut out from the captured image in a state where the shutter speed is controlled to be changed to the high speed by the second control means, and the cut out image of the road sign is A background / foreground discrimination means for discriminating between a background portion and a foreground portion;
Third control means for changing the shutter speed from the high speed to a predetermined low speed after the image of the road sign is cut out by the background / foreground discrimination means;
Color determining means for determining a chromatic color arranged on the detected road sign based on the captured image in a state where the shutter speed is controlled to be changed to the low speed by the third control means;
By synthesizing the chromatic color determined by the color determination unit with the background part or the foreground part determined by the background / foreground determination unit, a guidance image of the detected road sign is generated and generated. A sign guide display device comprising: guide display means for displaying the guide image on the display unit. The background / foreground discrimination means includes
After performing the binarization process on the clipped road sign image, the background part and the foreground part using the road sign image after the binarization process are determined,
The guidance display means includes
The sign guide display device according to claim 1, wherein the determined chromatic color is synthesized with one of the background portion and the foreground portion that has become black due to the binarization process. The guidance display means includes
The sign guidance display device according to claim 2, wherein white is assigned as it is to the other of the background portion and the foreground portion that has become white due to the binarization process. 2. The apparatus according to claim 1, further comprising: a sensitivity improving unit that further improves the sensitivity by image processing on the captured image when the sensitivity of the in-vehicle camera is increased by the change control by the third control unit. The sign guide display device according to any one of claims 3 to 4. The background / foreground discrimination means includes
After the shutter speed is changed to the high speed, it is detected that the vehicle has approached the detected road sign to a distance where the road sign can be sufficiently illuminated by a headlamp. The sign guidance display device according to any one of claims 1 to 4, wherein the background portion and the foreground portion are determined based on the captured image at the time of detection. The background / foreground discrimination means includes
The sign guide display device according to claim 5, wherein a distance from the vehicle to the road sign is determined based on a size of the detected road sign image. The sign guide display device according to any one of claims 1 to 6, wherein the sign guide display device is mounted on an in-vehicle AV device having no navigation function. A sign guide display method for displaying a road sign on a display unit of an in-vehicle device,
A first step of controlling a shutter speed of an in-vehicle camera that images a predetermined imaging area in front of the vehicle to a predetermined normal speed;
A second step of detecting the road sign based on a captured image of the in-vehicle camera in a state where the shutter speed is controlled to the normal speed in the first step;
A third step of changing and controlling the shutter speed from the normal speed to a predetermined high speed triggered by the detection of the road sign in the second step;
In the third step, the road sign image detected in the second step is cut out from the captured image in a state where the shutter speed is controlled to be changed to the high speed, and the road sign image cut out is extracted. A fourth step of distinguishing between the background portion and the foreground portion;
A fifth step of controlling to change the shutter speed from the high speed to a predetermined low speed after cutting out the image of the road sign in the fourth step;
A sixth step of determining a chromatic color arranged on the detected road sign based on the captured image in a state where the shutter speed is controlled to be changed to the low speed in the fifth step;
A guide image of the detected road sign is generated by synthesizing the chromatic color determined in the sixth step with the background portion or the foreground portion determined in the fourth step. And a seventh step of displaying the guidance image on the display unit. The fourth step includes
After the shutter speed is changed to the high speed, it is detected that the vehicle has approached the detected road sign to a distance considered to be able to sufficiently illuminate the road sign with a headlight. -1 step;
The sign guide according to claim 8, further comprising: a 4-2 step of determining the background portion and the foreground portion based on the captured image at the time of detection in the 4-1 step. Display method.