JP2007051922A - Face detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a face detector capable of reducing a circuit cost, and capable of surely computing the center of the face with reduced picture elements. <P>SOLUTION: This face detector includes a plurality of thermopile elements 721 distributed like a band for detecting infrared rays emitted from the face, an IR temperature detecting part 2 and a temperature distribution complimentary part 3 for computing a temperature distribution, based on a detection result, and a face position computing part 4 for computing the face center, based on a differential value of the temperature distribution, the face position computing part 4 computes a position of the whole face, based on the number of detecting the temperature distribution for the face, out of the plurality of thermopile elements 721. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of a face detection device that detects infrared rays emitted from the face mainly from the center of the face of a vehicle occupant and calculates from the data.

Conventionally, the presence / absence and position of a vehicle occupant are detected by a large number of infrared sensors arranged in a matrix (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-295440 (page 2-7, full view)

  However, in the conventional face detection device, the number of pixels is large and the processing calculation is complicated. Therefore, the circuit cost has become expensive.

This point will be described in detail.
The present invention has been made paying attention to the above-mentioned problems, and an object of the present invention is to provide a face detection device that can reduce the circuit cost and reliably calculate the center of the face with a small number of pixels. It is in.

  In order to achieve the above object, in the present invention, a plurality of elements that detect and detect infrared rays emitted from the face in a band shape, temperature distribution calculation means for calculating a temperature distribution from the detection result, and a differential value of the temperature distribution. And a face center calculating means for calculating the face center.

  Therefore, according to the present invention, it is possible to reduce the circuit cost and reliably calculate the center of the face with a small number of pixels.

  Hereinafter, an embodiment for realizing the face detection device of the present invention will be described based on Example 1 corresponding to claims 1 to 4.

First, the configuration will be described.
FIG. 1 is a system block diagram in which the face detection device according to the first embodiment is applied to a door mirror angle adjustment device.
The door mirror angle adjusting device 1 mainly includes an IR temperature detection unit 2, a temperature distribution complementing unit 3, a face position calculation unit 4, a door mirror rotation angle calculation unit 5, and a door mirror motor control unit 6.

FIG. 2 is a block diagram of the IR temperature detection unit 2 and the thermopile module 7 of the face detection apparatus according to the first embodiment.
The thermopile module 7 includes a lens 71, a thermopile unit 72, a scanning unit 73, and an amplifying unit 74 as main components.
The lens 71 is disposed in front of the thermopile unit 72 and collects infrared rays emitted from the detection area 8 on the thermopile unit 72.
The thermopile unit 72 has thermopile elements 721 for detecting infrared rays arranged in a matrix.

The scanning unit 73 selects an output signal from the thermopile element 721 by an address signal.
The amplifying unit 74 amplifies the output signal of the element selected by the scanning unit 73.

The IR temperature detection unit 2 includes a signal output unit 21, a multiplexer 22, an AD conversion unit 23, and a temperature calculation unit 24.
The signal output unit 21 outputs an address signal in a matrix arrangement of the thermopile elements 721 to the scan unit 73 at a predetermined timing.
The multiplexer 22 receives the output signal from the amplifying unit 74 and selects and switches the thermopile elements 721 in a matrix.
The AD conversion unit 23 performs AD conversion on the amplified signal of the element selected by the multiplexer 22.
The temperature calculation unit 24 calculates a measurement temperature from the AD-converted measurement value. Note that the temperature calculator 24 calculates the temperature distribution by selecting / switching the multiplexer 22.

The temperature distribution complementing unit 3 supplements the temperature distribution from the discrete temperature.
The face position calculation unit 4 calculates a face position and a face center position.
The door mirror rotation angle calculation unit 5 calculates the rotation angle of the door mirror according to the calculated face position.
The door mirror motor control unit 6 drives and controls the motor of the door mirror according to the calculated rotation angle of the door mirror.

Next, the operation will be described.
[Process to change the angle of the door mirror according to the face position]
FIG. 3 is an explanatory diagram illustrating a flow of processing for changing the angle of the door mirror using the face detection device according to the first embodiment.
First, when the temperature is detected by the IR temperature detector 2 and internal discrete data is generated, the temperature distribution is complemented from the discrete temperature.
Next, the face position and the face center position are calculated from the complemented temperature distribution, and the angle of the door mirror is changed from the face position and face center position of the calculation result.
Thereafter, when the driver moves to the left, the internal discrete data changes, and the temperature distribution is corrected again.

[Face position detection function]
FIG. 4 is an explanatory diagram of a state in which the face position is detected in the face detection apparatus according to the first embodiment.
In FIG. 4, the number of pixels in the horizontal direction of the thermopile element 721 is N, and the temperature detection width at N pixels is W. Further, if the width of the face f is 300 mm and the number of detected pixels of the face temperature distribution is M, W: 300 = N: M and M = 300 N / W.
Therefore, the face position can be calculated by detecting the temperature distribution of M by image processing. Thereby, the position of the face is calculated by calculation.

[Face center position detection]
FIG. 5 is an explanatory diagram showing the state of the differential value when detecting the center of the face in the face detection apparatus of the first embodiment.
In the first embodiment, it is assumed that the number of thermopile elements 721 is 8 pixels horizontally.
To detect the center of the face, first, in the case of 8 pixels (# 1 to # 8) in order to secure the working area, after storing the temperature data of # 1 to # 8, the working area next to # 8 The internal temperature is stored in an area (memory).
Next, a differential value of the temperature distribution is calculated. At this time, in order to reduce the calculation amount, the difference from the adjacent pixel is differentiated.
The differential value is searched from # 1, the interval where the differential value (threshold value) changes from + (plus) to-(minus) (when the room temperature is lower than the face temperature) is detected, and the zero cross point is calculated. The face center position. This is because the differential coefficient 0 has a temperature maximum. That is, in FIG. 5, 0+ {a / (a + b)} × (p−0).
In this way, in Example 1, the center of the face can be reliably obtained as a position indicated by a continuous value while reducing the number of thermopile elements 721.

FIG. 6 is a graph showing the temperature distribution measurement values of the pixels # 1 to # 8 of the thermopile module 7 and their differential values for four cases.
6A shows a case where there is no person, FIG. 6B shows a case where the person is in the center on the left side, and FIG. 6C shows a case where the person is in the center on the right side. As shown in FIGS. 6B and 6C, the left side position and the right side position between the thermopile elements with respect to the center position of the thermopile element # 5 can be accurately obtained by the zero cross point of the differential value. FIG. 6D shows a case where the vehicle is in the # 8 direction.

[Calculation of door mirror movement angle]
FIG. 7A is an explanatory diagram of the calculation in a state where the driver moves the face from the front to the left.
In FIG. 7A, it is assumed that the driver's face has moved from X1 in front of the IR sensor to X2 in the left direction. Let L be the distance from the thermopile module 7 to the driver's face. This L is preferably obtained from a driving position sensor. Furthermore, let θ0 be the direction of the driver obtained from the temperature distribution. M in the above description is calculated from M = L × tan θ0.
Here, if the moving angle of the right mirror is θ1, and θ2, θ3, L2, and M2 are set as shown in FIG. 7B, θ3 = tan ⁻¹ (M2 / (L + L2)), θ2 = tan ⁻¹ ((M2 + M) / (L + L2)), and θ1 is calculated from θ1 = θ3−θ2.
Therefore, when the driver's face moves from X1 in front of the IR sensor to X2 in the left direction, it can be dealt with by rotating the motor that drives the right door mirror by θ1.

[An effect that the angle of the door mirror changes according to the position of the face]
In the door mirror angle adjusting device 1 of the first embodiment, the 8-pixel thermopile element 721 (IR sensor element) measures the temperature distribution in the measurement range as shown in FIGS. 3 and 4 with respect to the face position of the driver. .
In this case, the position of the entire face and the position of the face center are measured. For the control of the door mirror, the position of the center of the face is used. However, for abnormalities such as noise, data is used with high reliability by detecting the position of the entire face.

  Here, the face center will be described. The range of measurement in Example 1 is generally from the forehead of the face to the nose. As a result, the temperature changes greatly on the left and right sides of the nose line or on the left and right sides of the nose line. The reason is due to the sunlight. Therefore, if the zero cross point of the differential value of the temperature distribution is taken, the face center can be obtained with high accuracy. As a result, the face center position can be obtained accurately even if the number of pixels to be measured is small and the face center is in the middle of the pixel. Since the face center can mean between the eyes, the same effect as obtaining the eye point can be obtained. As in the first embodiment, the door mirror is controlled by using the face center equal to the eye point.

In the first embodiment, when the driver changes the face position, the change amount of the face center is calculated, and the door mirror angle is changed, so that the driver can look backward as before changing the face position. It can be done.
For example, when passing a narrow road, passing by an oncoming vehicle without a margin, parking, etc., if you move your face to the left or right to look closely, the angle of the door mirror will not change in the past, The back could not be easily confirmed with a door mirror. I had to put my face back and look back or turn my face back. Therefore, when passing on narrow roads, passing by oncoming vehicles without margin, or in parking, etc., it was necessary to drive while checking the face frequently.

  However, in Example 1, when the face is moved to the left and right positions and the door mirror is viewed as it is, the rear can be well confirmed. Therefore, driving in difficult situations becomes very easy.

Next, the effect will be described.
In the face detection device according to the first embodiment, the effects listed below can be obtained. Note that (1) to (4) correspond to claims 1 to 4, respectively.

  (1) A plurality of thermopile elements 721 that detect and detect infrared rays emitted from the face in a band shape, an IR temperature detection unit 2 and a temperature distribution complement unit 3 that calculate a temperature distribution from the detection result, and a differential value of the temperature distribution Since the face position calculation unit 4 for calculating the face center from the above is provided, the circuit cost can be reduced, and the face center can be reliably calculated with a small number of pixels.

  (2) Since the face position calculation unit 4 calculates the position of the entire face from the number of detected thermopile elements among the plurality of thermopile elements 721, the position range of the entire face can be grasped, and the face center It can be achieved by detecting a small number of pixels.

  (3) Since the face position calculation unit 4 calculates the center of the face from the position where the differential value of the temperature distribution crosses 0, the circuit cost can be reduced by simple and reliable calculation determination, and the face position calculation can be reliably performed with fewer pixels. The center can be calculated.

  (4) The IR temperature detecting unit 2, the temperature distribution complementing unit 3, and the face position calculating unit 4 are provided in the vehicle as components of the door mirror angle adjusting device 1, and are determined from the face center position and the position of the door mirror. The door mirror rotation angle calculation unit 5 for calculating the movement angle of the door mirror when the face position is moved is provided so that the optimum door mirror angle can be obtained even if the face position is moved. It is possible to assist the operation when used.

As mentioned above, although the face detection apparatus of this invention has been demonstrated based on Example 1, it is not restricted to these Examples about concrete structure, The summary of the invention which concerns on each claim of a claim As long as they do not deviate, design changes and additions are permitted.
The plurality of elements that detect and distribute infrared rays in a band shape may be elements arranged in one or a plurality of rows, or may be arranged in a comb shape.
In the embodiment, the right door mirror is described, but it is desirable to change the angles of the left and right door mirrors according to the movement of the face position.

  The face detection device of the present application can be easily used when the position of the face is known to some extent, such as when a person sits like a car seat or stands at a predetermined position.

It is the system block diagram which applied the face detection apparatus of Example 1 to the door mirror angle adjustment apparatus. It is a block diagram of the IR temperature detection part and thermopile module of the face detection apparatus of Example 1. FIG. It is explanatory drawing which shows the flow of the process which changes the angle of a door mirror using the face detection apparatus of Example 1. FIG. In the face detection apparatus of Example 1, it is explanatory drawing of the state which detects the position of a face. In the face detection apparatus of Example 1, it is explanatory drawing which shows the state of the differential value at the time of detecting the center of a face. It is a graph which shows the temperature distribution measured value of each pixel of # 1 to # 8 of a thermopile module, and its differential value regarding four cases. It is explanatory drawing of a calculation of the driver direction and door mirror movement angle in the state where the driver moved the face from the front to the left.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Door mirror angle adjustment apparatus 2 IR temperature detection part 21 Signal output part 22 Multiplexer 23 Conversion part 24 Temperature calculation part 3 Temperature distribution complement part 4 Face position calculation part 5 Door mirror rotation angle calculation part 6 Door mirror motor control part 7 Thermopile module 71 Lens 72 Thermopile unit 721 Thermopile element 73 Scan unit 74 Amplification unit 8 Detection area f Face

Claims (4)

A plurality of elements that detect and distribute infrared rays emitted from the face in a band shape;
Temperature distribution calculating means for calculating the temperature distribution from the detection result;
A face center calculating means for calculating the face center from the differential value of the temperature distribution;
A face detection apparatus comprising: The face detection device according to claim 1,
Among the plurality of elements, provided with an entire face position calculating means for calculating the position of the entire face based on the number of detected temperature distributions of the face,
A face detection apparatus characterized by that. In the face detection device according to claim 1 or 2,
The face center calculating means includes:
The center of the face is calculated from the position where the differential value of the temperature distribution crosses 0.
A face detection apparatus characterized by that. The face detection device according to claims 1 to 3 is provided in a vehicle,
By providing door mirror movement angle calculation means to calculate the movement angle of the door mirror when the face position moves from the face center position and door mirror position, so that the optimal door mirror angle can be obtained even if the face position is moved did,
A face detection apparatus characterized by that.

Images