JP2009250785A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device which corrects highly accurately a change in the length of a baseline due to a temperature change, and has reliability sufficient as a distance measuring camera module to be mounted on a vehicle and used. <P>SOLUTION: This imaging device has a lens unit 6 having a plurality of optical lenses 4, 5 arranged on the same plane, an imaging element 12 having a plurality of image pickup areas corresponding to the plurality of optical lenses one to one, and a temperature detecting element 7 arranged touching the lens unit 6 to detect the temperature of the lens unit 6. The imaging device corrects a distance between the optical axes of the plurality of optical lenses 4, 5, based on the temperature detected by the temperature detecting means, and calculates its distance up to a photographic subject based on the corrected distance between the optical axes of the plurality of optical lenses. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a compound eye type imaging apparatus including a plurality of optical systems and an imaging element.

  A camera module used as a mobile phone camera or a vehicle-mounted small camera is an imaging device that forms a subject image on an imaging element such as a CCD or CMOS sensor via a lens and acquires image information of the subject.

  In recent years, such a camera module is demanded not only for colorization but also for higher image quality, and the number of pixels per unit area directly linked to image quality is steadily progressing to higher pixels. . There is also a demand for structural ingenuity to cope with downsizing, and stability and reliability over time of basic performance.

  Furthermore, a camera module using a compound eye lens in which a plurality of lenses are formed on the same surface has been proposed. With this compound-eye camera module, it is possible to measure the three-dimensional information of the subject and the distance to the subject.

Patent Document 1 discloses an example of a compound eye type camera module. An image pickup apparatus disclosed in Patent Literature 1 includes an image pickup device including a plurality of image pickup regions, a plurality of image pickup optical systems that respectively form subject images on the plurality of image pickup regions, and an image processing unit that processes an output signal of the image pickup device. And temperature measuring means for detecting the ambient temperature. The image processing unit performs position correction on the plurality of images by the plurality of imaging optical systems according to the output of the temperature measurement unit. Then, a plurality of images subjected to position correction are synthesized and a synthesized image signal is output.
JP 2002-204462 A

  When measuring the distance to the subject using such a compound eye type camera module, the change in the distance between the optical axes of the imaging optical system due to the temperature change, that is, the change in the baseline length has a great influence on the distance measurement accuracy. . Therefore, if the change in the baseline length cannot be corrected with high accuracy, it becomes a fatal defect particularly when used as a ranging camera module for in-vehicle use.

  Also in Patent Document 1, a temperature sensor is arranged on a substrate holding an image sensor, and a change in baseline length is corrected based on the ambient temperature detected by the temperature sensor.

  However, the configuration of Patent Document 1 has insufficient reliability as a ranging camera module for in-vehicle use.

  The present invention has been made in view of the above-described problems, and provides an imaging apparatus having sufficient reliability as a ranging camera module for in-vehicle use by correcting a change in baseline length caused by a temperature change with high accuracy. Is.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging unit having a lens unit in which a plurality of optical lenses are arranged on the same plane, and a plurality of imaging regions corresponding to the plurality of optical lenses on a one-to-one basis. An element and a temperature detection element that is disposed in contact with the lens unit and detects the temperature of the lens unit, and based on the temperature detected by the temperature detection means, the distance between the plurality of optical lenses is determined. The imaging apparatus corrects and calculates the distance to the subject based on the corrected distance between the plurality of optical lenses.

  According to the present invention, since the change in the baseline length caused by the temperature change can be corrected with high accuracy, an imaging apparatus having high reliability can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows an imaging apparatus according to the first embodiment of the present invention. 1A is a top view of the imaging apparatus, FIG. 1B is a perspective view of the lens unit, and FIG. 1C is a cross-sectional view as viewed from the side of the imaging apparatus. In each figure, the same components are described using the same numbers.

  In FIG. 1A, 1 is an upper lens barrel, 2 is an opening A formed in the upper lens barrel, 3 is an opening B formed in the upper lens barrel, 4 is an optical lens A, and 5 is an optical lens B. .

  A lens unit 6 formed with two optical lenses 4 and 5 is fixed to the upper barrel 1. The two optical lenses 4 and 5 are disposed at positions corresponding to the openings 2 and 3 that limit the entry angle of external light. The openings 2 and 3 have a conical shape having an inclined surface whose diameter decreases from the subject side to the optical lens side.

  FIG. 1B is a diagram showing a configuration for detecting the temperature of the lens unit 6. In FIG. 1B, 6 is a lens unit, 7 is a temperature detection element, and 8 is a lead wire. The lens unit 6 is obtained by integrally forming an optical lens A4 and an optical lens B5 on the same surface. The temperature detection element 7 is embedded in the lens unit 6 at a position where it does not interfere with the optical path of the optical lenses 4 and 5, that is, in a region other than the optical lens. The temperature detection element 7 is connected to a lead wire 8 for taking out an output.

  In this embodiment, the temperature detection element is embedded in the lens unit, but may be adhered to the surface of the lens unit.

  In the present embodiment, the temperature detection element is disposed at the end of the lens unit, but it is more preferable to dispose the temperature detection element in a region between the optical lenses 4 and 5. This is because the temperature change in this part most affects the change in the baseline length.

  In the present embodiment, an imaging device having two optical lenses 4 and 5 is described as a lens unit. However, the present invention is not limited to this, and many optical devices such as three eyes and four eyes are used. The same effect can be obtained as an imaging apparatus having a lens unit in which lenses are formed on the same surface.

  FIG. 1C is a cross-sectional view seen from the side of the imaging device of the present embodiment. In FIG. 1C, 9 is a lower lens barrel, 10 is an optical filter, 11 is a light shielding wall, 12 is an image sensor, and 13 is a substrate. An optical filter 10 having wavelength selectivity on the lens unit 6 side is bonded and fixed to the lower barrel 9 at a predetermined position. A light shielding wall 11 that divides the imaging region corresponding to each optical lens is disposed between the imaging element 12 and the optical filter 10. The upper lens barrel 1 to which the lens unit 6 and the temperature detecting element 7 are fixed is bonded and fixed to the lower lens barrel 9. The lens barrel in which the upper lens barrel 1 and the lower lens barrel 9 are integrated is positioned on the image pickup device 12 and fixed to the substrate 13 by a technique such as adhesion. Further, the lead wire 8 for taking in the output of the temperature detecting element 7 is taken out of the lower barrel 9 and connected to an electric circuit on the substrate 13.

  Next, effects of the imaging apparatus according to the present embodiment will be described.

  FIG. 2 is a cross-sectional view seen from the side of the imaging device 14 of the present embodiment. As shown in FIG. 2, temperature detection elements were provided at four positions 15, 16, 17, and 18. And this imaging device was thrown into the thermostat, the temperature of the thermostat was changed to each temperature, and the temperature in each position of an imaging device was measured.

  In the actual experiment in the present embodiment, the imaging device was put in a constant temperature bath set to 20 ° C. and the imaging device was operated and left for 2 hours, and then the four positions 15, 16, 17, and 18 were used. The temperature was measured. Further, the set temperature was changed from 20 ° C. to 40 ° C. at a rate of temperature increase of 20 ° C./hr, and left for 1 hour after reaching 40 ° C., and the temperatures at the four positions 15, 16, 17 and 18 were measured. Further, for the set temperature of 60 ° C., the temperature was measured in the same procedure as when the set temperature was changed from 20 ° C. to 40 ° C.

  The results are shown in Table 1. This measurement value is the temperature at each measurement position when the ambient temperature reaches the set temperature and is left for about 1 hour at the same temperature. As a result of increasing the temperature to 20 ° C., 40 ° C., and 60 ° C., the temperature at each of the positions 15, 16, 17, and 18 had an error of several degrees at any measurement position. In particular, the detected temperature of the temperature detecting element disposed on the back surface of the image pickup apparatus has a large error, and an error of 1.4 ° C. occurred when the ambient temperature was 20 ° C. and 40 ° C. and 2 ° C. and 60 ° C., respectively.

  Since this temperature distribution assumes an actual use state and is experimented in a state where the image pickup apparatus is operated, the image pickup device itself becomes a heat source, and the detected temperature becomes higher as the image pickup device is closer to the image pickup device. Also from such a result, the present invention in which the temperature detection element is directly connected to the lens unit is effective for accurately correcting the base line length between the lenses.

  From the above results, it can be seen that when the ambient temperature changes, the temperature at each position of the imaging device does not reach the ambient temperature in about 1 hour. In the conventional imaging apparatus, the ambient temperature is measured and the temperature correction is performed, but in this case, an error of several degrees has occurred. Even an error of several degrees greatly affects reliability as a ranging camera module for in-vehicle use.

  In addition to the change in ambient temperature, it has become clear from experiments that the influence of external light absorption cannot be ignored. That is, the lens unit material absorbs external light and the temperature of the lens unit rises. This effect is particularly noticeable when the ambient temperature is low.

  Based on these new findings described above, the imaging apparatus according to the present embodiment has a structure in which the temperature detection element 7 is brought into direct contact with the lens unit 6 to directly measure the temperature of the lens unit. Then, based on the detected temperature, the temperature change of the baseline length between the optical lens 4 and the optical lens 5 is corrected. As a result, the influence of ambient temperature change and the influence of external light absorption can be corrected with high accuracy, and sufficient reliability can be obtained as a ranging camera module for in-vehicle use.

  In the present embodiment, the temperature detection element is arranged so as to be in contact with the end of the lens unit so that light from outside does not enter the part, but the temperature detection element is also arranged in the part where the temperature detection element is arranged. An opening may be provided in the upper barrel 1 so that light from outside enters. In this case, since the influence of the temperature rise due to the external light can be directly measured, it can be corrected with higher accuracy.

  Next, a temperature correction method in the imaging apparatus according to the present embodiment will be described.

  Table 2 and FIG. 3 show the results of actually measuring the amount of change in the baseline length at each ambient temperature.

  With reference to about 20 ° C., the actual change in baseline length was measured under two conditions of about 40 ° C. and about 60 ° C. As is apparent from the results of FIG. 3, when the temperature of 20 ° C. is raised, the baseline length changes by about 3.5 μm. Moreover, when 40 degreeC temperature rose, the baseline length change of about 7.3 micrometers was recognized. The change in the baseline length is caused by the thermal expansion or thermal contraction of the lens unit material and depends on the lens unit material. In the present embodiment, the lens unit is formed of a plastic material, but since the plastic material has a larger coefficient of thermal expansion than glass or the like, the change in the baseline length becomes large.

  FIG. 4 is a schematic diagram for explaining the distance measurement calculation method. In FIG. 4, L is the distance from the optical lens to the subject, f is the focal length from the optical lens 4 or 5 to the image sensor, D is the base length that is the distance between the optical axes of the optical lens 4 and the optical lens 5, S is the parallax. In the imaging apparatus of the present embodiment, the distance to the subject can be obtained by the following (Equation 1).

  In (Equation 1), D and f are known, and S is a variable. By obtaining the value of S from the difference between the two images, the distance L to the subject can be obtained.

  However, D and f, which should be the existing values, are based on the premise that they always maintain a constant value (Equation 1), whereas D or f changes due to external factors such as temperature. The accuracy deteriorates depending on the error. In particular, D is highly susceptible to temperature and needs to be corrected accurately.

  In other words, the distance calculation D is calculated using a design value as a fixed value (assumed temperature is 20 ° C.) to obtain the distance L, so that an error occurs between the fixed value given in the calculation and the actual D depending on the temperature. Then, the error must be corrected.

  Table 2 shows an error dimension in which the design base line length D (in this embodiment, 2.5 mm at 20 ° C.) changes in an atmosphere of about 40 ° C. and about 60 ° C. assuming the use environment (both are on the + side). As a result of actual measurement, in order to improve the distance measurement calculation accuracy, it is necessary to predict this error and correct it in a timely manner.

  In other words, when the base line length D changes depending on the external temperature, a result of mistaking the distance to the subject is caused unless effective correction is performed.

  In the imaging apparatus of the present embodiment, the temperature of the lens unit can be detected with high accuracy by directly connecting the temperature detection element to the lens unit and correcting the baseline length from the output of the temperature detection element. Therefore, by correcting the value of the baseline length L in the above (Equation 1) from the obtained temperature, it becomes possible to perform high-precision distance measurement even in an environment where the temperature change is severe, and as a distance measurement camera module for in-vehicle use Sufficient reliability can be realized.

  The imaging apparatus of the present invention is useful as a small camera mounted on a mobile phone, a ranging camera for in-vehicle use, or the like.

Explanatory drawing of the imaging device of this embodiment Explanatory drawing of the temperature measurement position in the imaging device of this Embodiment The graph which shows the relationship between the detection temperature and baseline length change in the imaging device of this Embodiment Diagram explaining the principle of finding the distance by the principle of triangulation

Explanation of symbols

1 Upper barrel 2 Opening A
3 Opening B
4 Optical lens A
5 Optical lens B
6 Lens unit 7 Temperature detection element 8 Lead wire 9 Lower lens barrel 10 Optical filter 11 Shading wall 12 Image sensor 13 Substrate 14 Imaging device 15 Temperature detection position 16 Temperature detection position 17 Temperature detection position 18 Temperature detection position

Claims (4)

A lens unit in which a plurality of optical lenses are arranged on the same plane;
An imaging device having a plurality of imaging regions corresponding to the plurality of optical lenses on a one-to-one basis;
A temperature detecting element that is disposed in contact with the lens unit and detects the temperature of the lens unit;
An imaging apparatus that corrects distances between the plurality of optical lenses based on temperatures detected by the temperature detection unit, and calculates distances to a subject based on the corrected distances between the plurality of optical lenses. The imaging device according to claim 1, wherein the temperature detection element is disposed in contact with the lens unit in a region other than the plurality of optical lenses. The imaging device according to claim 2, wherein the temperature detection element is disposed in contact with the lens unit in a region between the plurality of optical lenses. The imaging device according to claim 2, wherein external light is incident on a region of the lens unit where the temperature detection element is disposed in contact.

Images