JP2008166926A - Backlight judging apparatus, and object imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight judging apparatus capable of correctly performing backlight detection, even when there are no main objects in a center section of an imaging region of a camera. <P>SOLUTION: A boarding person 1 sits down on a sheet 2 and wears a seat belt 3. A reflector 4 is pasted upon the seat belt 3. A car-mounted camera performs photometry in a photometry area, in which the reflector 4 is located in the usual status, among photographed images, and detects a part where lumimance is higher than other parts for a predetermined threshold as a position of the reflector 4. Then, as shown in the figure, an area of a decided number of pixels vertically and horizontally is extracted from an image of the detected reflector 4, as a lumimance calculation area 6. When an average value A of lumimance of pixels in the lumimance calculation area 6 is below a predetermined threshold, it is judged as a backlight status. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight determination device and a subject imaging method.

  Conventionally, an in-vehicle camera is used to take an image of the interior of a vehicle, determine whether a person is on board, whether the person on board is an adult or a child, and use it for airbag deployment control, etc. . In such adjustment of the exposure of the in-vehicle camera, the average value of the luminance of the pixels corresponding to the entire imaging screen is obtained, and feedback control is performed so that the average value becomes a predetermined value.

  However, in such exposure adjustment, for example, when the backlight is in a backlit state where the sun rays are inserted from behind the subject, the average value of the luminance of the pixels corresponding to the entire imaging screen increases in the feedback control, resulting in the exposure time. As a result, there is a problem that a human being as a subject is imaged darkly.

As a countermeasure against this, for example, in Japanese Patent No. 3478455, the average value of the luminance of the pixel is calculated separately for the center and the peripheral portion of the imaging region, and the average value of the luminance of the central portion is the average value of the luminance of the peripheral portion. Describes a method of performing a backlight exposure process when it is determined that the backlight is in a backlight state when it is lower than a predetermined value.
Japanese Patent No. 3478455

  However, the technique described in Patent Document 1 is effective when the camera is oriented in a predetermined direction and the main subject is at a predetermined position in the central portion of the imaging region. If the main subject is not located at a predetermined position in the central portion of the imaging area, there is a problem that it does not function effectively.

  The present invention has been made under such circumstances, and a backlight determination device capable of accurately detecting backlight even when a main subject is not in the central portion of the imaging region of the camera, and a subject imaging method using the same. The issue is to provide.

  The first means for solving the above problems includes an in-vehicle camera that images the interior of a passenger car, an infrared light source that illuminates a person on a seat of the passenger car, and a seat belt worn by the occupant. A reflector provided in a portion located on the occupant's body, imaging the human with the infrared light source, and of the captured image, a portion considered to be captured in a steady state A portion from the imaging area where the luminance is equal to or higher than a predetermined first threshold value is determined as the position of the reflector, and the average value of the luminance of the pixels of the portion and a predetermined portion around the portion is determined. A backlight determination device comprising means for determining that the backlight is in a backlight state when the calculated average value is lower than a predetermined second threshold value.

  The second means for solving the above problems includes an in-vehicle camera that images the interior of a passenger car, an infrared light source that illuminates a person riding on a seat of the passenger car, and a seat belt worn by the occupant. A reflector provided in a portion located on the occupant's body, imaging the human with the infrared light source, and of the captured image, a portion considered to be captured in a steady state A portion from the imaging area where the luminance is equal to or higher than a predetermined first threshold value is determined as the position of the reflector, and the average value of the luminance of the pixels of the portion and a predetermined portion around the portion is determined. And a means for determining that the backlight is in a backlight state when a difference between the calculated average value and the average value of the luminance of the pixels in all the imaging regions is larger than a predetermined third threshold value. Is a backlight determination device

  The third means for solving the above problems includes an in-vehicle camera that images the interior of a passenger car, an infrared light source that illuminates a person riding on a seat of the passenger car, and a seat belt worn by the occupant. A reflector provided in a portion located on the occupant's body, imaging the human with the infrared light source, and of the captured image, a portion considered to be captured in a steady state A portion of the imaging area where the luminance is equal to or higher than a predetermined first threshold is determined as the position of the reflector, and one horizontal scanning line passing through the position of the reflector (that is, the luminance of the horizontal pixel) Is calculated from the continuous luminance line), the average value of the luminance of the pixels corresponding to the passenger and the seat is calculated, and when the average luminance is lower than a predetermined third threshold, it is determined that the backlight is in the backlight state. Means to do Is a backlight determination apparatus characterized by having.

  A fourth means for solving the problem is any one of the first to third means, which has a clock and determines the time when the sun is inserted into the vehicle from a date obtained from the clock. However, it is characterized in that it is determined that it is in the backlight state only at the time.

  The fifth means for solving the above-mentioned problem is the intensity of the infrared light source when it is determined that the backlight is in the backlight state by any one of the first to fourth means. In the subject imaging method, the calculated average brightness value is strengthened so as to be a predetermined value.

  According to the present invention, it is possible to provide a backlight determination device capable of accurately detecting backlight even when a main subject is not in the central portion of the imaging region of the camera, and a subject imaging method using the backlight determination device.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an image taken by an in-vehicle camera (not shown). In this invention, it has an infrared light source and radiates infrared light toward the main subject (crew).

  In FIG. 1, a crew member 1 is seated on a seat 2 and a seat belt 3 is attached. A reflector 4 is attached to the seat belt 3. The in-vehicle camera performs photometry in the photometric area 5 that is a range where the reflector 4 is located in a normal state in the captured image, and a part whose luminance is higher than the other part by a predetermined threshold value is reflected on the reflector 4. Detect as position.

  Then, as shown in FIG. 2, an area having the number of pixels determined in the vertical and horizontal directions is extracted as a luminance calculation area 6 from the detected image of the reflector 4. For example, if the position of the reflector 4 corresponds to the pixels from the a-th to b-th in the horizontal direction and the c-th to d-th in the vertical direction, M and N are integers, and (a-M) to ( b + M), the range of the (c−N) to (d + N) th pixels in the vertical direction is extracted as the luminance calculation area 6. In the following drawings, the same components as those shown in the previous drawings are denoted by the same reference numerals and description thereof is omitted.

  When the average luminance value A of the pixels in the luminance calculation area 6 is equal to or less than a predetermined threshold value, it is determined that the backlight is in the backlight state. Alternatively, when the value of (B−A), which is the difference between the average value A of the luminance and the average value B of the luminance of the pixels of the entire image, exceeds a predetermined threshold value, the backlight state is determined.

  FIG. 3 is a diagram illustrating another method for determining the backlight state. In FIG. 3A, the position of the reflector 4 is determined by the method as described above, and a line 7 of horizontal pixels passing therethrough is formed. When the transition of the luminance of the line 7 is seen, a line showing the transition of the luminance as shown in FIG. 3B is obtained. Among these, the high luminance portion at the center is a portion corresponding to the reflector 4. Therefore, the left and right low luminance portions of the high luminance portion correspond to the pixel portions corresponding to the occupant 1 and the seat 2. The average value of the luminance of the pixels corresponding to the crew member 1 and the seat 2 is obtained, and when the average luminance is lower than a predetermined third threshold, it is determined that the backlight is in the backlight state.

  By the way, the backlight state is generated only in the time zone when the sun is inserted from the vehicle window. Therefore, the date and time may be determined using a clock, and the above-described backlight determination may be performed only when the time is the time when the sun is inserted through the vehicle window.

  In the embodiment of the present invention, when it is determined that the backlight is in the backlight state by the backlight determination device as described above, the intensity of the infrared light source is increased, and thereby the brightness of the 6 pixels in the brightness calculation area described above is increased. The average value A or the average luminance value of the pixels on the line 7 corresponding to the sheet 2 is set to a predetermined value. Thereby, it becomes possible to image the brightness of the main subject as the predetermined brightness.

  In the above description, the image calculation process is performed by the CPU on the image data read from the in-vehicle camera to the CPU via the frame memory. The CPU also performs backlight determination based on a clock and control of the intensity of the infrared light source.

It is a figure which shows the outline | summary of the image imaged with the vehicle-mounted camera. It is a figure which shows the example of a brightness | luminance extraction area. It is a figure which shows another method of discriminating a backlight state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Crew, 2 ... Seat, 3 ... Seat belt, 4 ... Reflector, 5 ... Photometry area, 6 ... Luminance calculation area, 7 ... Line

Claims (5)

  An in-vehicle camera that images the interior of a passenger car, an infrared light source that illuminates a person on the passenger's seat, and a reflection provided on a portion of the seat belt worn by the occupant located on the occupant's body A first image whose luminance is determined in advance from an imaging region of a portion in which the human is imaged in a steady state among the captured images. A portion that is equal to or greater than a threshold is determined as the position of the reflector, and the average value of the luminance of the pixel of the portion and a predetermined portion around the portion is calculated, and the calculated average value is determined in advance. A backlight determination device comprising means for determining that the backlight is in a backlight state when the threshold is lower than the second threshold.   An in-vehicle camera that images the interior of a passenger car, an infrared light source that illuminates a person on the passenger's seat, and a reflection provided on a portion of the seat belt worn by the occupant located on the occupant's body A first image whose luminance is determined in advance from an imaging region of a portion in which the human is imaged in a steady state among the captured images. A portion that is equal to or greater than a threshold value is determined as the position of the reflector, the average value of the luminance of pixels of the portion and a predetermined portion around the portion is calculated, the calculated average value, and the entire imaging region A backlight determining apparatus comprising: means for determining that the backlight is in a backlight state when a difference from the average luminance value of the pixels is greater than a predetermined third threshold value.   An in-vehicle camera that images the interior of a passenger car, an infrared light source that illuminates a person on the passenger's seat, and a reflection provided on a portion of the seat belt worn by the occupant located on the occupant's body A first image whose luminance is determined in advance from an imaging region of a portion in which the human is imaged in a steady state among the captured images. The portion that is equal to or greater than the threshold is defined as the position of the reflector, and the occupant from one horizontal scanning line that passes through the position of the reflector (that is, the luminance of the pixels in the horizontal direction is indicated by a continuous luminance line). And a backlight determination device characterized by comprising means for calculating an average value of the luminance of the pixels corresponding to the seat and determining that the pixel is in the backlight state when the average luminance is lower than a predetermined third threshold value.   4. The backlight determination device according to claim 1, wherein the backlight has a timepiece, and from the date obtained from the timepiece, the time when the sun is inserted into the vehicle is determined, and it is determined that the backlight is in the backlight state only at the time. The backlight determination apparatus characterized by performing.   When the backlight determination device according to any one of claims 1 to 4 determines that the backlight is in a backlight state, the intensity of the infrared light source is calculated as an average value of the calculated luminance. A subject imaging method characterized by strengthening to become a predetermined value.

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