JP4120629B2 - Imaging apparatus and imaging method - Google Patents

Description

  The present invention relates to an imaging apparatus and an imaging method.

  In recent years, an automatic driving system that automatically operates a car, a driving assistance system that automatically performs some operations, and a collision warning system have been developed. In this type of system, a white line on a runway and a target object such as a vehicle or a person are extracted by mounting a camera on the vehicle.

  2. Description of the Related Art Conventionally, in an imaging device attached to a vehicle, the photoelectric conversion characteristic of an image sensor system is a logarithmic characteristic, and imaging is possible with a wide dynamic range (see Patent Document 1 below).

Japanese Patent Laid-Open No. 3-192864 Japanese Patent Laid-Open No. 10-340390

  However, if the reflected light from the window glass is overlapped by the scattered light in the vehicle interior during imaging with the in-vehicle camera, the brightness ratio of the target decreases and the contrast decreases, and detection of target objects such as white lines and surrounding moving objects is detected. There is a problem that reliability decreases.

  In order to solve such a problem that the detection reliability of a subject in a required area is reduced due to disturbance light, an optical filter that irradiates the required area with light of a specific wavelength and transmits the light of the specific wavelength is provided. Japanese Patent Application Laid-Open No. 2004-260688 describes a method of imaging with an imaging means. In this method, a device for irradiating light is necessary, and the color of the subject may be erroneously recognized. Further, the effect is increased as the distance between the device for irradiating light and the subject increases. descend.

  The problem to be solved by the present invention is to reduce the contrast of the target object due to the reflected light from the transparent plate when imaging the target object through the transparent plate without using a device for irradiating light. It is an object to provide an imaging apparatus and an imaging method capable of preventing the above.

  A reflected light amount calculation unit, a pixel light amount calculation unit, and a calculation unit, the reflected light amount calculation unit calculates the reflected light amount in the visual field based on the brightness of the image area of the reflecting mirror in the visual field of the imaging means; The pixel light amount calculation unit calculates the light amount of each pixel in the field of view, and the arithmetic unit logarithmically converts the light amount obtained by subtracting the reflected light amount from the light amount of the pixel and outputs the light to the outside. Configure the device.

  By implementing the present invention, a reflection mirror that reflects light from an object other than the target object toward the imaging unit is used, and the reflection in the field of view is based on the brightness of the image area of the reflection mirror in the field of view of the imaging unit. A transparent image is formed when a target object is imaged through a transparent plate without using a device for irradiating light, and forming an imaging device characterized by calculating a light amount and subtracting it from the light amount of each pixel. It is possible to provide an imaging apparatus capable of preventing a decrease in contrast of a target object due to reflected light from a plate-like body.

  FIG. 1 shows the configuration of an image pickup apparatus according to the present invention using an in-vehicle image pickup apparatus as an example.

  An electronic camera 10 that is an imaging means with linear characteristics is installed in the passenger compartment, and the camera 10 passes through a window glass 40 that is a transparent plate-like body and is located in front of the vehicle including the target object as shown in FIG. Captures and outputs a visual field image. The camera 10 is provided with a reflecting mirror 20 for imaging light from a vehicle interior region such as the dashboard 50 that is an object other than the target object reflected on the window glass 40 with the camera 10. The reflecting mirror 20 is a reflecting mirror that blocks light from the target object and reflects light from an object other than the target object (such as the dashboard 50) toward the camera 10 that is an imaging unit.

  The output of the camera 10 is input to the image processing device 30 and is subjected to arithmetic processing and output.

  The reflecting mirror 20 is installed at a position that does not interfere with the subject image during imaging. For example, when a moving object such as a surrounding vehicle is a main subject, it is installed at a position that appears in the upper right corner of the image as in the reflecting mirror image area 100 of FIG. It is set so that the scattered light of the portion where the reflection is generated on the window glass 40 such as the board 50 can be captured by the camera. When the reflecting mirror 20 is a convex mirror, objects other than a wide range of target objects including the dashboard 50 can be projected in the reflecting mirror image area 100, which is advantageous. The reflecting mirror 20 may be fixed to the camera 10 or may be fixed so that the relative positional relationship with the camera 10 is kept constant via the vehicle body.

  The characteristic of the camera 10 is a linear characteristic in which the pixel light amount value changes linearly (in a linear function) with respect to the subject luminance. This is because the linear characteristic does not change the pixel value difference even when the luminance value of the subject changes due to reflection from an object other than the target object, and the S / N can be kept constant. Here, the amount of light is obtained by multiplying the luminance by a certain time.

  In the processing device 30, in the input image, the reflected light amount calculation unit 31 calculates an average value of the pixel values of the reflected mirror image region 100 of the captured image, and uses the previously measured luminance-pixel value characteristics of the camera to obtain the luminance value. This value is multiplied by the reflectance of the window glass 40 to calculate the amount of reflected light superimposed on the subject image, which is the amount of reflected light from the transparent plate-like body (in this case, the window glass 40) in the field of view. . Further, when the reflecting mirror 20 is a convex mirror, the entire dashboard 50 can be projected in the reflecting mirror image area 100. Therefore, the amount of reflected light to be superimposed on the subject image in the field of view is calculated based on the image. It is also possible to calculate it as a function of the position in the field of view, thereby making it possible to remove the influence of reflected light more precisely.

  In the input image, the pixel light amount calculation unit 32 converts the output of the camera 10 into the luminance value of the pixel by using the luminance-pixel value characteristic of the camera 10 measured in advance for each pixel of the image.

  The output of the pixel light amount calculation unit 32 and the output of the reflected light amount calculation unit 31 are input to the calculation unit 33, and after subtracting the output of the reflection light amount calculation unit 31 from the output of the pixel light amount calculation unit 32, logarithmically convert and output as an output image. Is output. Note that such calculation may be performed using a luminance value, or may be performed using a light amount obtained by multiplying the luminance value by a certain time.

  The above processing will be described with reference to FIG. 3 in the case where a white line on the road surface is imaged. From the captured pixel values Va1 and Vb1 of the road surface and white line in the shade, and pixel values Va2 and Vb2 of the road surface and white line in the sun. The pixel light amount calculation unit 32 calculates the luminance values A1 ′, B1 ′, A2 ′, and B2 ′ corresponding to each unit according to the linear relationship indicated by “linear” in the figure, and from these values, the reflected light amount calculation unit After subtracting the brightness increase I calculated in 31 (corresponding to the amount of reflected light) to obtain A1, B1, A2, and B2, the log is shown as “Log” for A1, B1, A2, and B2. Logarithmic conversion is performed according to the logarithmic relationship shown. In the pixel value after conversion, the contrast d1 in the shade is maintained at the same value as the contrast d2 in the sun.

  FIG. 2 is a diagram for explaining the effect of the present invention by the imaging screen of the camera 10. (A) of the figure shows a case where there is no reflection from the window glass 40, (b) shows a conventional imaging screen when there is reflection from the window glass 40, and (c) shows from the imaging apparatus according to the present invention. The output screen is shown. As shown in (b) of the figure, the contrast between the white line in the shade and the road surface is lowered by the superimposition of the reflected light from the window glass 40 as compared with that in the sun. On the other hand, the output of the imaging apparatus according to the present invention is as shown in (c), and even when there is an overlap of reflected light on the window glass, an image with contrast maintained is subtracted from the influence. Obtainable. Even in a bright area in the sun and a dark area such as a shade, an image with the same contrast ratio can be obtained with a constant reflectance ratio.

  Next, a processing procedure by the imaging apparatus configured as described above will be described with reference to the flowchart of FIG.

  The process is started when, for example, the ignition of the vehicle is turned on, and steps S1 to S5 are periodically repeated at a time interval Δt.

  In step S1, imaging with the camera 10 is performed.

  In step S2, the amount of light in the reflecting mirror image region 100 of the captured image is calculated. The details are as described above.

  In step S3, the amount of light in the subject area of the captured image is calculated. The details are as described above.

  In step S4, the pixel value of the subject is calculated from the two light quantities calculated in steps S2 and S3. The details are as described above.

In step S5, the calculated pixel value is output.
When the process up to step S5 is completed, the process returns to step S1 to capture the next image and perform the process.

  As described above, according to the present invention, a logarithmic characteristic image maintaining the contrast of a subject can be obtained even when the subject light is superposed by the reflected light from the transparent plate-like body. Even if there is a change in illuminance due to a place such as a shadow or time such as day and night, an image can be obtained in which the contrast of a subject having the same reflectance ratio is kept constant.

It is a figure for demonstrating the structure of this invention. It is a figure explaining the effect of this invention. It is a figure for demonstrating the relationship between the luminance value in this invention, and a pixel value. It is a figure for demonstrating the processing flow in this invention.

Explanation of symbols

  10: Camera, 20: Reflecting mirror, 30: Image processing device, 31: Reflected light amount calculating unit, 32: Pixel light amount calculating unit, 33: Computing unit, 40: Window glass, 50: Dashboard, 100: Reflecting mirror image area.

Claims (4)

  An imaging unit having a linear characteristic for imaging a target object through a transparent plate, and a light beam from an object other than the target object that is disposed at a position where the image is captured by the imaging unit and blocks the light from the target object. An imaging apparatus comprising a reflecting mirror that reflects toward a light source, a reflected light amount calculation unit, a pixel light amount calculation unit, and a calculation unit, wherein the reflected light amount calculation unit is an image of the reflecting mirror in the field of view of the imaging unit The amount of reflected light from the transparent plate-like body in the field of view is calculated based on the brightness of the region, the pixel light amount calculation unit calculates the amount of light of each pixel in the field of view, and the arithmetic unit calculates from the amount of light of the pixel An imaging apparatus, wherein the amount of light obtained by reducing the amount of reflected light is logarithmically converted and output to the outside.   The imaging apparatus according to claim 1, wherein the reflecting mirror is a convex mirror.   The target object is imaged by the imaging means having a linear characteristic through the transparent plate, and light from an object other than the target object is reflected toward the imaging means by a reflecting mirror disposed at a position where the image is taken by the imaging means. The reflected light amount calculation unit calculates the reflected light amount from the transparent plate-like body in the visual field based on the brightness of the image area of the reflecting mirror in the visual field of the imaging means, and the pixel light amount calculation unit calculates the reflected light amount in the visual field. An imaging method, comprising: calculating a light amount of each pixel, logarithmically converting a light amount obtained by subtracting the reflected light amount from the light amount of the pixel by an arithmetic unit, and outputting the result to the outside.   The imaging method according to claim 3, wherein the reflecting mirror is a convex mirror.

Images