KR20080054022A - Polarization sensor using position sensitive detector and polarization image sensor using it - Google Patents

Abstract

A polarization sensor using a PSD and a polarization image sensor using the same are provided to obtain the angle of a polarization axis by analyzing output coordinates of the PSD. A polarization sensor calculates the polarized degree of incident light and the angle of a polarization axis and includes a PSD(P), a polarization filter, and a polarization information calculator. The PSD(Position Sensitive Detector) outputs 2D X and Y coordinates of the center of mass of an incident beam. The polarization filters are attached at different polarization axis angles on plural regions of a light incident surface of the PSD. The polarization information calculator calculates the polarized degree of the incident beam and the angle of the polarization axis from the output coordinates of the PSD.

Description

Polarization Sensor with Position Sensitive Detector and Polarization Image Sensor Using It {POLARIZATION SENSOR USING POSITION SENSITIVE DETECTOR AND POLARIZATION IMAGE SENSOR USING IT}

1 is a block diagram of a preferred embodiment of the present invention

Figure 2 is a perspective view showing the polarization axis angle and the arrangement of the PSD of the incident polarization

Figure 3 is a layout view of the output terminal of the general PSD

<Description of Major Symbols in Drawing>

L, L1: incident light, F1, F2, F3, F4: polarization filter

P: PSD O: Origin

The present invention relates to a polarization sensor using a PSD and a polarization image sensor using the same.

Conventional machine vision is about recognizing specific marks in images taken with a camera. In this case, a mark is used by using an infrared light source and attaching an infrared filter passing only infrared rays in front of the camera so that only the mark is photographed brightly. This method has a disadvantage in that an infrared light source including a power line is required.

The present invention provides a polarization image sensor capable of recognizing a polarization mark that can be composed of a polarizing film or the like in the general natural light state, unlike the infrared light source mark that must be installed with the existing power supply wiring, and a polarization sensor used therefor. It is done. Conventional polarization image sensors are known in the US patent (polarization sensitive solid state image sensor and associated method, Pub. No: US 2005/0279921 A1). The conventional polarizing image sensor is a type of polarizing filter attached to each pixel of the conventional image sensor. In contrast, the polarizing image sensor of the present invention is characterized by simplifying the structure by using PSD in the light receiving element of each pixel. That is, the conventional polarizing image sensor is formed of a plurality of light receiving elements constituting one pixel, and a polarizing filter having different polarization axis angles is attached to each light receiving element. In contrast, the light receiving element of the polarization image sensor of the present invention is simply configured with one PDS. In addition, the polarization image sensor of the present invention is very convenient to convert from the polarization information to the luminance signal and the color image signal.

A typical configuration of the polarization sensor of the present invention is four polarization filters of different polarization axes at different angles on four isosceles triangles separated by X shapes on a square two-dimensional PSD (P) as shown in FIG. 1 (F1, F2, F3). , F4) is attached. The angles of the polarization axes of the four polarization filters F1, F2, F3, and F4 measured in the clockwise direction from the y-axis, which are the vertical lines in Fig. 1, are 0 degrees, 45 degrees, 90 degrees, and 135 degrees, respectively. Here, the PSD is a known optical sensor that outputs (x, y) coordinate values corresponding to the center of gravity of the incident light. In more detail, a typical two-dimensional psd has output terminals of currents Ix1, Ix2, Iy1, and Iy2 on four sides of a quadrangle as shown in FIG. 3. It is well known to calculate the x, y coordinates of the center of gravity of the incident light by the sum of the currents, the difference and the division value. When natural light mixed with light from all directions of polarization passes through the polarization filters (F1, F2, F3, F4) arranged as shown in FIG. 1 and enters the psd, the intensity of light passing through the four regions is not different. The coordinates are the origin O x = 0, y = 0. However, when the polarized light polarized in a specific direction is incident, the intensity of light passing through the four polarization filters are all different. That is, the flat polarization filter with the incident polarization and the polarization axis parallel the most light, and the polarization filter that forms 90 degrees to the polarization axis of the incident light blocks the light. In this case, the amount of light passing through each polarizing filter is different and the coordinates biased toward the brightest area are output from the PDS. By converting the coordinates (x, y) into polar coordinates (r, θ) and analyzing the angular coordinates θ, the angle of the polarization axis of the incident light can be calculated. That is, the closer the output coordinate of the PSD constituting the polarization sensor of the present invention to the origin (0,0) is the natural light, and the farther away from (0,0) (that is, the larger the r value of the polar coordinate), the polarization is. If the output coordinates are (x, y) when four polarization filters are arranged as shown in Figs. 1 and 2, the angle (θ) of the polarization axis of the incident light L1 in Fig. 2 is tan 2θ = y / x. θ is the angle value of the polarization axis of the incident light L1 measured clockwise from the y axis shown in Figs. 1 and 2. And the coordinate values x, y are coordinates centered on the origin O shown in Figs.

 In this way, if the polarization filters are arranged regularly on different areas on the light receiving surface of the PSD with different polarization axis angles, the output coordinate values of the PSD can be analyzed to distinguish whether the incident light is natural light or polarized light. Can be calculated.

When such a polarization sensor is used as a light receiving element of each pixel of the image sensor, a polarization image sensor capable of photographing polarization can be configured. The configuration of a specific polarization image sensor is as follows. Conventional color image sensors output R, G, and B values at each pixel. The R, G, and B values are converted into a luminance signal Y and two color signals Cb and Cr to form an ntsc signal and output to the outside of the camera. In contrast, the polarization image sensor according to the present invention uses the polarization sensor according to the present invention as a light receiving element for each pixel of the image sensor. At this time, the two color signals Cb and Cr are obtained by firstly transforming the output coordinate values (x, y) of the polarization sensor of each pixel. The luminance signal Y is a value proportional to the total amount of light incident on the polarization sensor of each pixel, that is, the sum of the absolute values of the four current outputs of FIG. 3 (| Ix1 | + | Ix2 | + | Iy1 | + | Iy2 |) is obtained by first-order conversion. The reason for the first-order conversion is to make the range of the output coordinate x, y values of the PSD positive and the maximum value to the maximum value of the existing color signals Cb and Cr. . The maximum value of the sum of the absolute values of the four current outputs (| Ix1 | + | Ix2 | + | Iy1 | + | Iy2 |) is intended to be the maximum value of the existing luminance signal Y. When the luminance signal Y and the color signals Cb and Cr obtained by the conversion are configured as NTSC signals and outputted, if the NTSC signals are displayed on a monitor, the parts without polarization appear as black and white images and the parts with polarization appear as color. Therefore, by attaching the polarization filter to the mark to be recognized in the machine vision to reflect or transmit the polarized light in the natural light state and to shoot it with the polarization image sensor according to the present invention to recognize if only the pixel with the color component in the image taken It becomes a polarization mark. In addition, analyzing the color value can also calculate the angle of the polarization axis of the polarization mark. That is, when the polarization mark is photographed with the polarization image sensor of the present invention, only the polarization mark portion is photographed in color, and the other background portions are photographed in black and white. Therefore, using a polarization mark instead of an infrared light source mark that requires a conventional power source and a camera using a polarization image sensor as a camera used for machine vision, the polarization mark can be easily detected in natural light without a separate power supply.

Using the polarization sensor according to the present invention, it is possible to find out whether the incident light is polarized and if the polarization is the angle of the polarization axis by analyzing the output coordinates of the PSD. In addition, by using the polarization sensor according to the present invention as a pixel light-receiving element, a black and white signal proportional to the total amount of light received is output and the output coordinates (x, y) of the PSD by the received light are respectively two colors. When converted into a signal, a polarized image sensor may be configured to output an image in which only a portion that is polarized is displayed in color, and a portion that is not polarized is displayed in black and white. Using such a polarizing image sensor, it is possible to recognize an infrared mark even when shooting with natural light instead of an infrared light source mark that requires a conventional power source.

Claims (5)

In the polarization sensor for calculating the polarization of the incident light and the polarization axis angle, A PSD for outputting two-dimensional x, y coordinates of the center of gravity of the incident light amount; A polarization filter unit attached to a plurality of regions of the light incident surface of the PSD at different polarization axis angles; And a polarization information calculator configured to calculate whether the incident light is polarized and the angle of the polarization axis from the output coordinates of the PSD. According to claim 1, wherein the polarization filter unit is attached clockwise from the top to the angle of the polarization axis is 0, 45, 90, 135 degrees on the area that divides the rectangular PSD into four isosceles triangles of x-shape, respectively; The polarization information calculation unit determines that the incident light is polarized as the output coordinate value of the PSD is farther from the origin, and at this time, the angle obtained by converting the output coordinate value into polar coordinates is analyzed to calculate the angle of the polarization axis of the incident light. In the image sensor to take a picture The light receiving element of each pixel is a polarization sensor that detects polarization The luminance signal of each pixel is a value proportional to the total amount of light incident on the polarization sensor, and the color signal is a value including angle information of the polarization axis of incident light detected by the polarization sensor. According to claim 3, wherein the polarization sensor constituting the light receiving element of each pixel A PSD for outputting two-dimensional x, y coordinates of the center of gravity of the incident light amount; A polarization filter unit attached to a plurality of regions of the light incident surface of the PSD at different polarization axis angles; And a polarization information calculator configured to calculate whether the incident light is polarized and the angle of the polarization axis from the output coordinates of the PSD. The method of claim 4 The polarization filter unit is attached clockwise from the top so that the angle of the polarization axis is 0,45,90,135 degrees, respectively, on the area that divides the rectangular PSD into four isosceles triangles of x shape. The polarization information calculating unit determines that the incident light is polarized as the output coordinate value of the PSD is far from the origin, and calculates the angle of the polarization axis of the incident light by analyzing the angle obtained by converting the output coordinate value into polar coordinates. .

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