JP2013218252A - Camera device and range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of characteristics of a solid state image sensor mounted on a camera device by reducing distortion due to thermal fatigue damage.SOLUTION: A camera device 10 includes an imaging lens 11, a solid state image sensor 30 having an imaging area 33 for taking an object image incident on the imaging lens, and a focal distance holding member 17 for holding the interval between the imaging lens and the solid state image sensor. The focal distance holding member is fixed to the solid state image sensor and has the substantially same linear expansion coefficient as main material of the solid state image sensor.

Description

  The present invention relates to a camera apparatus having an imaging lens and a solid-state imaging element that captures a subject image incident on the imaging lens, and a distance measuring apparatus including the same, and more particularly to a solid-state imaging element caused by a change in ambient temperature. The present invention relates to a camera device and a distance measuring device that can suppress a decrease in characteristics of the camera.

Patent Document 1 describes a distance measuring device which is an example of a camera device with a fixed focal length. The distance measuring device includes an imaging lens (imaging lens), a solid-state imaging device (photosensor array) that captures a subject image incident on the imaging lens, and an interval holding member that holds an interval between the imaging lens and the solid-state imaging device. (Lens holding member). The solid-state imaging device is held by a CCD holding member, and an imaging lens and a CCD holding member are fixed to the interval holding member.
In Patent Document 1, the imaging lens, the interval holding member, and the CCD holding member are made of the same resin material (amorphous cycloolefin polymer), and the linear expansion coefficients of the respective members joined to each other are unified. This suppresses a decrease in ranging accuracy due to changes in ambient temperature and humidity.

Here, since the solid-state imaging device is generally made on a silicon wafer by using semiconductor technology, its linear expansion coefficient is about 3 ppm / ° C. On the other hand, the linear expansion coefficient of the resin material is several tens of ppm / ° C. or higher, and the linear expansion coefficient is about one digit higher than that of the material of the solid-state imaging device.
For this reason, in patent document 1, the thermal fatigue damage in the junction part of a solid-state image sensor and resin material cannot be removed completely. Furthermore, there is a problem that distortion caused by thermal fatigue damage adversely affects the characteristics of the image sensor. The thermal fatigue damage is damage that each member receives due to a temperature change, and mainly includes cracks, peeling, and the like.
The present invention has been made in view of the above-described circumstances, and suppresses deterioration in characteristics of a solid-state imaging device by reducing distortion due to thermal fatigue damage, and has a highly reliable camera device and a ranging device including the same. The purpose is to provide.

  In order to solve the above problems, the present invention maintains an imaging lens, a solid-state imaging device having an imaging region for imaging a subject image incident on the imaging lens, and an interval between the imaging lens and the solid-state imaging device. A focal length holding member, wherein the focal length holding member is fixed to the solid-state image sensor and has a linear expansion coefficient substantially the same as that of the main material of the solid-state image sensor. Features.

  According to the present invention, since the linear expansion coefficient of the spacing member is substantially the same as the linear expansion coefficient of the main material of the solid-state image sensor, distortion caused by thermal fatigue damage between the spacing member and the solid-state image sensor. In addition, it is possible to reduce deterioration in characteristics of the solid-state imaging device.

1 is a plan view of a distance measuring device according to a first embodiment of the present invention. It is AA sectional drawing of the distance measuring device shown in FIG. (A), (b) is a top view which shows an example of an electrical equipment board | substrate. (A)-(e) is sectional drawing which shows the manufacturing process of the distance measuring device shown in FIG.1 and FIG.2. It is sectional drawing which shows the distance measuring device which concerns on 2nd embodiment of this invention. It is sectional drawing which shows the distance measuring device which concerns on 3rd embodiment of this invention. It is BB sectional drawing of the distance measuring device shown in FIG. It is a top view of the ranging apparatus which concerns on 4th embodiment of this invention. It is CC sectional drawing of the distance measuring device shown in FIG. It is sectional drawing which shows the distance measuring device which concerns on 5th embodiment of this invention. (A)-(e) is sectional drawing which shows the manufacturing process of the ranging apparatus shown in FIG. It is sectional drawing which shows the distance measuring device which concerns on 6th embodiment of this invention. It is a block diagram of the ranging system carrying the ranging device which concerns on each embodiment of this invention. It is a figure which shows the basic principle of triangulation.

  Hereinafter, the present invention will be described in detail based on each embodiment. However, the components, types, combinations, shapes, relative arrangements, and the like described in the following embodiments are merely illustrative examples of the present invention unless otherwise specified, and are intended to limit the scope to that only. is not.

The present invention is a monocular or compound-eye camera device that is used in various applications such as in-vehicle, monitoring, medical, or surveying, or is mounted on a robot or a game machine or the like, and performs planar image shooting, stereoscopic image shooting, distance measurement, or the like. It is an invention applicable to.
In the following embodiments, a stereo range finder (compound-eye camera device) having two imaging lenses will be described as an example. However, the present invention is a monocular having a single imaging lens and an imaging region corresponding thereto. The present invention can also be applied to a camera device or a compound eye camera device having three or more imaging lenses and an imaging region corresponding to each imaging lens.

First, prior to describing the embodiment of the present invention, the basic principle of triangulation employed in the distance measuring device will be described. FIG. 14 shows the basic principle of triangulation.
FIG. 14 shows a case where the subject 101 is photographed by two cameras 102 (cameras 102a and 102b) having the same optical system.
The camera 102 includes a lens 103 (103a, 103b) on which a subject image is incident, and an image sensor 104 (104a, 104b) that captures the subject image formed by each lens 103. The camera 102 is fixed on the base substrate 106 so that the optical axes 108a and 108b are parallel to each other.
In the camera 102a, the subject image 107a incident from the lens 103a is projected onto the image sensor 104a with a shift of δ1 from the optical axis 108a. The subject image 107a is received by a large number of light receiving elements (pixels) in an image pickup area on the image pickup element 104a and converted into an electric signal.

Similarly, in the camera 102b, the subject image 107b incident from the lens 103b is projected onto the image sensor 104b with a deviation of δ2 from the optical axis 108b. The subject image 107b is received by a large number of light receiving elements (pixels) in the imaging region on the imaging element 104b and converted into an electrical signal.
The “deviation” of each subject image 107 from the optical axis 108 occurs in a direction perpendicular to the optical axis 108 (left-right direction in the figure) in a plane including the two optical axes 108 a and 108 b. Therefore, when the coordinate axis is taken in the left-right direction in the figure, the left direction in the figure is set to the plus direction and the right direction is set to the minus direction, the subject image 107a is shifted by δ1 in the plus direction with respect to the optical axis 108a, and the subject image 107b Since it is shifted by δ2 in the minus direction, it can be expressed as parallax δ = δ1 − (− δ2).

Here, the distance between the optical axes 108a and 108b of the lenses 103a and 103b is called a baseline length. When the base line length is D, the distance from the subject 101 to the lens 103 is L, and the focal length of each lens 103 is f, Equation (1) holds when L >> f.
L = D · f / δ Formula (1)
Since the baseline length D and the focal length f of the lens 103 are design values and are known values, the distance L to the subject 101 can be calculated from the equation (1) by detecting the parallax δ.

[First embodiment]
A distance measuring apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view of the distance measuring apparatus according to the first embodiment of the present invention. 2 is a cross-sectional view taken along the line AA of the distance measuring device shown in FIG. The distance measuring device according to the present embodiment is a compound eye camera device including two imaging lenses, each imaging lens is physically separated from each other, and the focal length holding member is made of silicon, It is characterized in that a solid-state imaging device having two imaging areas is formed on one substrate and that a slit is formed in a part of an electrical board on which the solid-state imaging device is mounted.
The distance measuring device 10 is a device that measures the distance to a subject using the principle of triangulation shown in FIG. As shown in FIG. 2, the distance measuring device 10 (compound-eye camera device) includes a plurality of imaging lenses 11 (11a, 11b) spaced apart from each other, and a plurality of subject images incident on the imaging lenses 11, respectively. The solid-state imaging device 30 having the imaging region 33 (33a, 33b) and the focal length holding member 17 (spacing holding member) that holds the distance between each imaging lens 11 and each imaging region 33 constant are provided. .
The focal length holding member 17 is fixed to the solid-state image sensor 30. The focal length holding member 17 is made of silicon, which is the main material of the solid-state image sensor 30, and has substantially the same linear expansion coefficient as that of the solid-state image sensor 30.
Further, the distance measuring device 10 includes a plurality of electrode pad groups 41 (41a, 41b) corresponding to the respective imaging regions 33, and an electrical component on which the solid-state imaging element 30 is mounted across the electrode pad groups 41. And a substrate 40.
The two imaging lenses 11 each have an optical axis X (Xa, Xb) at the center thereof, and the distance between the centers of the imaging lenses 11 is the base length D (see FIG. 14). The optical axes Xa and Xb of the imaging lenses 11a and 11b are arranged so as to be substantially perpendicular to and parallel to the imaging regions 33a and 33b, respectively. The side walls 13 (13a, 13b: lens non-processed surfaces) of the imaging lenses 11a, 11b are coated with black or a black film so as not to be affected by ambient light. For example, a glass lens or a resin lens can be used as the imaging lenses 11a and 11b. A glass lens has a smaller linear expansion coefficient than a resin lens, and thus is more suitable as a material for an imaging lens used in this embodiment. A glass lens is more expensive than a resin lens and disadvantageous in terms of cost, but is effective in securing high measurement accuracy.
Apertures 15 (15a, 15b) are arranged on the subject side with respect to the imaging lenses 11a, 11b.

The aperture 15 cuts light incident on the distance measuring device 10 from other than the lens portion of the imaging lens 11 out of light incident on the distance measuring device 10 to improve the S / N ratio of the imaging region 33. The aperture 15 can be produced, for example, by etching an SUS430 plate material to form an opening having a size corresponding to the lens portion of the imaging lens 11 (see FIG. 1).
The focal length holding member 17 is disposed between the imaging lens 11 and the imaging region 33. The focal length holding member 17 holds the focal length f (see FIG. 14) from each imaging lens 11 to each imaging region 33 constant. The focal length holding member 17 holds the optical axes Xa and Xb of the imaging lenses 11a and 11b so as to be substantially perpendicular to the imaging regions 33a and 33b and parallel to each other while holding the base line length D.
The focal length holding member 17 applies light to the through-holes 19 (19a, 19b) serving as an optical path for guiding the subject image incident on each imaging lens 11 to each imaging region 33 on a silicon wafer having a thickness that can define the focal length f. It is formed in the direction of the axis X (Xa, Xb). The through hole 19 is formed so that the center of the cross section in the direction perpendicular to the optical axis direction coincides with the optical axis X. That is, the distance between the centers of the two through holes 19a and 19b is made to be the baseline length D.

The solid-state imaging device 30 is manufactured using silicon as a main material. The solid-state imaging device 30 is configured by arranging two imaging regions 33a and 33b in a line on the silicon wafer 31 so that the distance between the centers becomes the baseline length D. The two imaging regions 33a and 33b are formed on one substrate (silicon wafer 31). For each imaging region 33, a CMOS image sensor, a CCD image sensor, or the like in which a plurality of pixels are arranged in a grid pattern can be used. A cover glass 35 is attached to the surface of the imaging region 33 on the light receiving unit side for the purpose of protecting the imaging region 33 (preventing scratches, dust, etc.).
The plurality of electrodes in the imaging region 33 are arranged on the opposite side of the imaging region 33 mounting surface (surface on which the imaging region 33 is not mounted, solid) via TSV (Through Silicon Via: not shown) formed in the silicon wafer 31. The image sensor 30 is drawn to the lower surface side in the drawing. A solder ball is disposed on each electrode drawn from the imaging region 33 to the surface on which the imaging region 33 is not mounted on the silicon wafer 31 via the TSV. The solder balls are BGAs (Ball Grid Array) arranged in a grid pattern, and a group of solder balls corresponding to each imaging region 33 forms a solder ball group 37 (37a, 37b). The solder ball group 37 is used when the solid-state imaging device 30 is mounted on the electrical board 40.

  On the electrical board 40, a plurality of electrode pads that are electrically connected to the respective solder balls of the solid-state imaging device 30 are formed. A group of electrode pads corresponding to each solder ball group 37 constitutes an electrode pad group 41 (41a, 41b). The electrode pad groups 41a and 41b correspond to the imaging regions 33a and 33b on a one-to-one basis. A solid-state image sensor 30 is mounted on each electrode pad group 41 via a solder ball group 37 by SMT (Surface Mount Technology). An underfill material 49 (49a, 49b) is filled between the solid-state imaging device 30 and the electrical board 40 for the purpose of ensuring the reliability of solder ball bonding.

Here, FIGS. 3A and 3B are plan views showing an example of the electrical board. As shown in the drawing, a slit 43 (43A or 43B: buffer portion) is formed between the electrode pad groups 41a and 41b of the electrical board 40. The slit 43 is a space that separates adjacent electrode pad groups 41a and 41b.
The slit 43 can be a concave slit 43A extending from the edge of the electrical board 40 toward the center as shown in FIG. In this manner, the edge of the electrical board 40 may be separated by the slits 43A. Moreover, the slit 43 can also be made into the slit 43B as a through-hole which penetrates the electrical equipment board | substrate 40 extended toward the center part from the edge part of the electrical equipment board | substrate 40, for example, as shown to (b). Thus, it is good also as a structure with which the edge of the electrical equipment board | substrate 40 is continued, without separating by the slit 43B. As described above, in the electrical board 40 according to the present embodiment, the adjacent electrode pad groups 41 are physically separated by the slits 43 in the region where the solid-state imaging device 30 is mounted.

As shown in FIG. 2, the underfill material 49 is filled in a state in which the solder ball groups 37 and the electrode pad groups 41 corresponding to the imaging regions 33a and 33b are separated. That is, on the electrical board 40 side from the solder ball group 37, the members corresponding to the adjacent imaging regions are arranged separately from each other for each imaging region. Further, in the distance measuring device 10, the focal length holding member 17 and the solid-state imaging device 30 are integrally configured, but are physically separated in the imaging lens 11 portion.
As shown in FIGS. 1 and 3, an electrical signal from each imaging region 33 is processed in a region where the electrode pad group 41 is not formed (a region where the solid-state imaging device 30 is not mounted) in the electrical board 40. A distance measuring arithmetic circuit (calculator) 45 and a digital signal processor (DSP) 47 for calculating the distance to the subject are mounted.

Next, a method for manufacturing the distance measuring device according to the first embodiment of the present invention will be described.
4A to 4E are cross-sectional views illustrating the manufacturing steps of the distance measuring device shown in FIGS. 1 and 2. The same components as those in the previous figure will be described with the same reference numerals.
First, as shown in FIG. 4A, a solid-state imaging device 30 is prepared. The solid-state imaging device 30 is a double CMOS sensor array in which two imaging regions 33a and 33b are arranged in parallel. As the cover glass 35, AF45 (linear expansion coefficient: 4.5 ppm / ° C.) manufactured by shot, which has a linear expansion coefficient close to that of the silicon wafer 31 on which the imaging regions 33a and 33b are formed (silicon linear expansion coefficient of 2). .8 ppm / ° C.).
In this embodiment, since a double CMOS sensor array is used as the solid-state image sensor 30, the solid-state image sensor 30 can be manufactured by a general semiconductor manufacturing process. Accordingly, the high accuracy obtained in the semiconductor manufacturing process can be ensured for the distance between the two imaging regions 33a and 33b. In addition, since the two imaging regions 33a and 33b are formed on the silicon wafer having a small linear expansion coefficient, the parallax change caused by the environmental temperature change can be suppressed to a small value. As such, a high parallax accuracy is obtained, thereby improving the ranging accuracy.

The solid-state imaging device 30 forms a plurality of imaging regions (33a, 33b...) On a silicon wafer 31 having a 6-inch or 12-inch diameter, and then covers a cover glass 35 on the light-receiving portion side of each imaging region 33. It is manufactured by pasting, forming a TSV in the silicon wafer 31, and cutting in accordance with the base line length D of the silicon wafer 31. Furthermore, the solid-state image pickup device 30 is completed by disposing solder balls (solder ball groups 37a and 37b) on the respective electrodes drawn to the non-mounting surface of the imaging region 33 via the TSV.
For the solder balls, for example, tin (Sn), silver (Ag), or copper (Cu) based alloys not containing lead can be used. Sn-30% Ag-0.5% Cu is the mainstream, but increasing the silver content leads to an increase in cost. Therefore, in order to reduce costs, Sn-10% Ag-0.7% Cu has a low silver composition. Sn-0.3% Ag-0.7% Cu, Sn-0.1% Ag-0.7% Cu, or the like may be used.

Next, as shown in FIG. 4B, the focal length holding member 17 is directly attached to the surface of the cover glass 35 corresponding to the light receiving unit side of the solid-state imaging device 30 with an adhesive. At this time, the through holes 19a and 19b of the focal length holding member 17 are attached with their positions aligned so that the centers of the through holes 19a and 19b (the centers in the cross section in the direction perpendicular to the optical axis X) are the approximate centers of the imaging regions 33a and 33b.
Silicon was used for the base material of the focal length holding member 17. Silicon is a material that is opaque in the visible light region, and exhibits the effect that light incident into one through hole 19a does not leak into the other through hole 19b. That is, since the focal length holding member 17 itself functions as a light shielding member that prevents crosstalk of the imaging light beam, there is no need to make a separate light shielding member. Therefore, the number of manufacturing steps is reduced, leading to cost reduction. If a separate light shielding member is produced, thermal fatigue due to a difference in linear expansion coefficient between the focal length holding member and the light shielding member may occur when the environmental temperature changes. Since the focal length holding member 17 is made of a single material, the problem of thermal fatigue does not occur, and the measurement accuracy and durability of the distance measuring device 10 are improved.

  In addition, since the material of the focal length holding member 17 used in the present embodiment is silicon, which is the same material as the base material of the solid-state imaging device 30, the linear expansion coefficients of the focal length holding member 17 and the solid-state imaging device 30 are the same. It is almost the same. Therefore, the influence of thermal fatigue between the focal length holding member 17 and the solid-state imaging element 30 becomes a negligible level, it becomes easy to ensure the bonding strength between the solid-state imaging element 30 and the focal length holding member 17, and the linear expansion between the members. The reliability of the distance measuring device is improved by reducing thermal fatigue due to the coefficient difference.

Next, as shown in FIG. 4C, the imaging lenses 11 a and 11 b are directly bonded onto the focal length holding member 17. The imaging lenses 11a and 11b are bonded with their positions aligned so that the centers (optical axes Xa and Xb) of the imaging lenses 11a and 11b coincide with the centers of the imaging regions 33a and 33b.
Note that the side walls 13a and 13b of the imaging lenses 11a and 11b are painted black or a black film is applied to prevent the intrusion of ambient light.

The imaging lenses 11a and 11b were made by press molding a glass material. Sumita Optical K-VC78 was used for the optical glass material of the imaging lenses 11a and 11b. K-VC78 is an example of a material that can be used for the imaging lens 11. Any optical glass material can be used according to the optical design.
In the present embodiment, since the two imaging lenses 11a and 11b are physically separated and attached to the focal length holding member 17, the thermal expansion of the imaging lens 11 due to the fluctuation of the environmental temperature is caused by the imaging lenses 11a and 11b. It is hard to affect the distance between. That is, the change in the distance between the imaging lenses 11 a and 11 b due to the environmental temperature change is determined by the linear expansion coefficient between the focal length holding member 17 and the solid-state imaging device 30. Therefore, the change in the positional relationship between the imaging lenses 11a and 11b and the imaging regions 33a and 33b becomes insensitive to environmental temperature changes. Further, since silicon having a small coefficient of linear expansion is used for the focal length holding member 17, the dependency of the baseline length D on the environmental temperature is reduced, and the dependency of the measurement accuracy on the environmental temperature can be suppressed.

Next, as shown in FIG. 4D, the apertures 15a and 15b are attached to the surfaces of the imaging lenses 11a and 11b with an adhesive. The apertures 15a and 15b are pasted with their positions aligned so that the two opening centers of the apertures 15a and 15b coincide with the centers (optical axes Xa and Xb) of the imaging lenses 11a and 11b.
The aperture 15 was manufactured by etching a 0.25 mm thick SUS430 material. The aperture 15 may use a metal material other than the SUS430 material used in this embodiment. Moreover, you may use another material and may manufacture with another construction method.

  4 (b) to 4 (d), as the adhesive for bonding the solid-state imaging device 30 and the focal length holding member 17, the focal length holding member 17 and the imaging lens 11, and the imaging lens 11 and the aperture 15, respectively. An adhesive that can withstand a lead-free reflow process at about 270 ° C. is preferable, and a heat-resistant epoxy adhesive, a modified silicon adhesive, and the like are particularly suitable. In this embodiment, Alemcobond 570 (developed by Alemco Products, USA), which is a high heat-resistant epoxy adhesive, was used. Alemcobond 570 is a one-component adhesive having a heat resistant upper limit of 316 ° C. It is a material that can withstand lead-free reflow and is easy to handle and highly productive because it is one-part. The adhesive thickness was adjusted to 0.2 mm.

  Finally, as shown in FIG. 4 (e), a distance calculation circuit 45 and a digital signal processor 47 are mounted in advance, and an electrical board 40 having electrode pad groups 41a and 41b formed on the surface is bonded. The solder ball groups 37a and 37b were aligned with the electrode pad groups 41a and 41b on the electrical board 40 and passed through a reflow furnace, whereby the electrical board 40 and the solid-state imaging device 30 were electrically and mechanically connected. Furthermore, in order to improve the reliability of the connection portion, an underfill material 49 was poured between the solid-state imaging device 30 and the electrical component substrate 40 and hardened. The electrode pad groups 41a and 41b of the electrical board 40 are separated from each other by the slits 43, and the underfill material 49 is injected into a state separated between the solder ball groups 37 and between the electrode pad groups 41. .

As described above, in the present embodiment, since the focal length holding member is formed of silicon, which is the main material of the solid-state imaging device, the environmental temperature change that has been a problem when parts having different linear expansion coefficients are joined. The accompanying problem of thermal stress can be avoided, and a decrease in reliability due to thermal fatigue can be suppressed.
In addition, since silicon having a small linear expansion coefficient is used for the focal length holding member, the dependency of the baseline length on the environmental temperature can be reduced.
Since silicon applied to the focal length holding member is opaque to the visible light region, it functions as a light shielding member that prevents crosstalk of the imaged light beam without providing a separate light shielding member. Therefore, the number of manufacturing steps for forming the light shielding structure can be reduced.
Furthermore, a slit 43 is formed between the electrode pad groups 41 a and 41 b of the electrical board 40, and the electrical board 40 is physically separated between the electrode pad groups 41. Therefore, the influence of the thermal expansion of the electrical board 40 with respect to the environmental temperature change becomes difficult to be transmitted to the solid-state imaging device 30, and the change in the baseline length D can be suppressed. Accordingly, it is possible to suppress a decrease in measurement accuracy with respect to a change in environmental temperature.

[Second Embodiment]
A distance measuring apparatus according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the distance measuring apparatus according to the present embodiment. This sectional view corresponds to the AA section of FIG. The present embodiment is characterized in that ceramics are used for the focal length holding member. The same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The focal length holding member 51 of the distance measuring device 50 is a member that keeps the focal length f (see FIG. 14) from the imaging lens 11 to the imaging region 33 constant, and is disposed between the imaging lens 11 and the imaging region 33. Has been. The focal length holding member 51 is formed with through holes 19 (19a, 19b) in the direction of the optical axis X (Xa, Xb) that serve as an optical path for guiding the subject image incident on each imaging lens 11 to each imaging region 33. Yes. The through hole 19 is formed so that the center of the cross section in the direction perpendicular to the optical axis direction coincides with the optical axis X.

In this embodiment, the material of the focal length holding member 51 may be a silicon carbide (SiC) -based or silicon nitride (Si ₃ N ₄ ) -based ceramic material, which is a covalent bond material having strong interatomic bonding force. .
Many silicon carbide ceramic materials having a linear expansion coefficient of 3 to 4 ppm / ° C. and silicon nitride ceramic materials having a coefficient of linear expansion of 2 to 3 ppm / ° C. have been commercialized. It can be made substantially the same as the linear expansion coefficient (2.8 ppm / ° C.).
In addition, silicon carbide-based and silicon nitride-based ceramics are opaque to the visible light region, and the material itself has a light shielding effect. As in the first embodiment, a new light shielding member is added. There is no need to grant.

As described above, according to the present embodiment, the silicon carbide (SiC) -based ceramic material has a linear expansion coefficient of 3 to 4 ppm / ° C., and the silicon nitride (Si ₃ N ₄ ) ceramic material has a linear expansion coefficient of 2 to 3 ppm / ° C. Many products have been commercialized and can be made substantially the same as the linear expansion coefficient of the solid-state imaging device 30, so that thermal fatigue due to the difference in linear expansion coefficient between the solid-state imaging device 30 and the focal length holding member 51 can be reduced. Therefore, the reliability of the distance measuring device is improved.
Silicon carbide-based and silicon nitride-based ceramics are opaque to the visible light region, and the material itself has a light shielding effect, so that crosstalk of the imaged light beam can be prevented without providing a separate light shielding member. Since it functions as a light shielding member, the number of processing steps can be reduced, and the light shielding member is not required, leading to cost reduction.

[Third embodiment]
A distance measuring apparatus according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a cross-sectional view showing the distance measuring apparatus according to the present embodiment. This sectional view corresponds to the AA section of FIG. FIG. 7 is a cross-sectional view of the distance measuring apparatus shown in FIG. The present embodiment is characterized in that a glass material is used for the focal length holding member, and a chromium or nickel metal film is used as a light shielding member. The same members as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.
The focal length holding member 61 of the distance measuring device 60 is a member that keeps the focal length f (see FIG. 14) from the imaging lens 11 to the imaging region 33 constant, and is disposed between the imaging lens 11 and the imaging region 33. Has been. The focal length holding member 61 is formed with through holes 19 (19a, 19b) in the direction of the optical axis X (Xa, Xb) that serve as an optical path for guiding the subject image incident on each imaging lens 11 to each imaging region 33. Yes. The through hole 19 is formed so that the center of the cross section in the direction perpendicular to the optical axis direction coincides with the optical axis X.

In this embodiment, Tempax glass or Pyrex (registered trademark) glass can be used as the material of the focal length holding member 61.
Tempax glass has a linear expansion coefficient of 3.2 ppm / ° C., Pyrex (registered trademark) glass has a linear expansion coefficient of 3.2 ppm / ° C., and the linear expansion coefficient (2.8 ppm / ° C.) of the solid-state imaging device 30 using silicon as a base material. Can be made almost identical.
In this embodiment, Tempax glass is used for the base material (main body) 63 of the focal length holding member 61. As the base material 63 of the focal length holding member 61, in addition to Tempax glass and Pyrex (registered trademark) glass, AF45, AF32, Tempax Float (registered trademark of Shott) also have a linear expansion coefficient close to that of silicon. It is applicable from. However, these are materials that are commercially available as thin glass, and the thickness of the glass is limited. Therefore, to use it as it is, the range of use is limited to ranging devices for short focal distance measurement with a short focal length. The In addition, in order to use it for a distance measuring device other than the short focus distance measuring, it is necessary to devise a method such as bonding a plurality of glasses, which increases the number of steps. In that respect, Tempax glass and Pyrex (registered trademark) glass have a wide variety of commercially available glass thicknesses, and thus can be applied to distance measuring devices having various focal lengths, and the range of selectivity is further expanded. Furthermore, since a general-purpose material can be used, it is advantageous in that the material cost can be suppressed.
When a material transparent in the visible light region such as glass is used as the base material 63 of the focal length holding member 61, a light shielding function as a crosstalk suppressing means in the imaging region 33 is required. In the present embodiment, crosstalk is suppressed by adding a light shielding film 65 to the base material 63 of the focal length holding member 61. The light shielding film 65 is formed by depositing a chromium or nickel metal film. As a film forming method, a vacuum deposition method, a sputtering method, a plating method, or the like is effective. In particular, the plating method is more practical in securing the adhesion of the film.

As described above, in this embodiment, a glass material is used as the base material of the focal length holding member. The glass material can cover a wide range by optical polishing, and a flat and smooth joining surface can be secured. Since the distance between the imaging lens and the imaging region can be made uniform, the image shift between the left and right is suppressed.
In addition, since the linear expansion coefficient of the focal length holding member can be substantially the same as the linear expansion coefficient of the solid-state imaging device, it is easy to ensure the bonding strength between the imaging lens and the solid-state imaging device and the focal length holding member, and The reliability of the distance measuring device is improved by reducing thermal fatigue due to the difference in linear expansion coefficient.
Since Tempax glass or Pyrex (registered trademark) glass material transmits visible light, distance measurement is possible without forming a through hole as an optical path for guiding the subject image to the imaging region. The manufacturing cost can be reduced.

[Fourth embodiment]
A fourth embodiment of the present invention will be briefly described with reference to FIGS. FIG. 8 is a plan view of a distance measuring apparatus according to the fourth embodiment. 9 is a cross-sectional view taken along the line CC of the distance measuring device shown in FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
As shown in the figure, the electrical board 71 of the distance measuring device 70 in this embodiment is not formed with the slits 43 as shown in FIGS. 1 and 2, and the electrical board 71 has a rectangular shape. The distance measurement arithmetic circuit 45 and the DSP 47 shown in FIG.
Other members constituting the distance measuring device 70 are the same as those in the first embodiment, and the focal length holding member 17 is made of silicon.
As described above, in this embodiment, since the focal length holding member is made of silicon having the same linear expansion coefficient as that of the main material of the solid-state imaging device, there is a problem when parts having different linear expansion coefficients are joined. Since the problem of thermal stress associated with environmental temperature changes can be avoided, a decrease in reliability due to thermal fatigue can be suppressed.
In addition, since silicon having a small linear expansion coefficient is applied to the imaging distance holding member, the dependency of the baseline length on the environmental temperature can be reduced.
Further, since silicon applied to the imaging distance holding member is opaque with respect to the visible light region, it functions as a light shielding member for preventing crosstalk of the imaging light beam without providing a separate light shielding member. Therefore, the number of manufacturing steps for forming the light shielding structure can be reduced.
In addition, you may use the focal distance holding member shown in 2nd embodiment or 3rd embodiment.

[Fifth embodiment]
A distance measuring apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a cross-sectional view of the distance measuring device, which corresponds to the CC cross section of FIG. The distance measuring device according to this embodiment includes two physically separated solid-state imaging elements, and the electrical board on which the two solid-state imaging elements are mounted is rectangular (no slit is formed). There is. Hereinafter, the same members as those in the first to fourth embodiments are denoted by the same reference numerals, and the description thereof is omitted.
The distance measuring device 80 includes two solid-state imaging devices 30 (30a, 30b) each having an imaging region 33 (33a, 33b) for capturing subject images incident on the imaging lenses 11a, 11b. Each imaging region 33 is formed on a different substrate (silicon wafers 31a and 31b), and the surface of each imaging region 33 on the light receiving unit side is protected (prevention of scratches, dust, etc.). For the purpose, cover glasses 35 (35a, 35b) are respectively attached.
In the distance measuring device 80, each solid-state imaging device 30a, 30b has its imaging plane (surface of the imaging areas 33a, 33b) on the same plane, and the distance between the centers of the two imaging areas 33a, 33b is the baseline length D ( (See FIG. 14).
Each solid-state imaging device 30 is formed with a plurality of imaging regions (33a, 33b...) On a silicon wafer 31 having a diameter of 6 inches or 12 inches, for example, and then a cover glass on the light receiving unit side of each imaging region 33. 35 is affixed, TSV is formed in the silicon wafer 31, and the silicon wafer 31 is cut for each solid-state imaging device 30 (30a, 30b...). Furthermore, the solid-state image pickup device 30 is completed by disposing solder balls (solder ball groups 37a and 37b) on the respective electrodes drawn to the non-mounting surface of the imaging region 33 via the TSV.

Next, a method for manufacturing the distance measuring device will be described.
FIGS. 11A to 11E are cross-sectional views illustrating manufacturing steps of the distance measuring device shown in FIG. The same components as those in FIG. 10 are described with the same reference numerals. Moreover, below, the process different from the manufacturing process mainly shown in 1st embodiment (FIG. 4) is demonstrated, and description is abbreviate | omitted about the same process.
First, as shown in FIG. 11A, a focal length holding member 17 is prepared. The base material of the focal length holding member 17 is silicon.
Next, as shown in FIG. 11B, the two solid-state imaging devices 30a and 30b are bonded and fixed to one surface of the focal length holding member 17 in the through hole 19 formation direction. The cover glass 35a and 35b of the solid-state imaging devices 30a and 30b are bonded and fixed to the focal length holding member 17, respectively. At the time of bonding, the positions of the through holes 19a and 19b are aligned so that the centers of the through holes 19a and 19b (the centers in the cross section perpendicular to the direction in which the through holes 19 extend) are the centers of the imaging regions 33a and 33b.
Since the adhesion process after FIG.11 (c) is the same as that of 1st embodiment (after FIG.4 (c)), description is abbreviate | omitted.

As described above, in this embodiment, since the focal length holding member is formed of silicon, which is the main material of the solid-state imaging device, the environmental temperature change that has been a problem when parts having different thermal expansion coefficients are joined is used. The accompanying problem of thermal stress can be avoided, and a decrease in reliability due to thermal fatigue can be suppressed.
In addition, since silicon having a small linear expansion coefficient is used for the focal length holding member, the dependency of the baseline length on the environmental temperature can be reduced.
Since silicon applied to the focal length holding member is opaque to the visible light region, it functions as a light shielding member that prevents crosstalk of the imaged light beam without providing a separate light shielding member. Therefore, the number of manufacturing steps for forming the light shielding structure can be reduced.
In addition, you may apply the focal distance holding member shown in 2nd embodiment or 3rd embodiment.

[Sixth embodiment]
A distance measuring apparatus according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 12 is a cross-sectional view of the distance measuring device, and corresponds to a cross section AA in FIG. Hereinafter, the same members as those in the first to fifth embodiments are denoted by the same reference numerals, and the description thereof is omitted.
A distance measuring device 90 according to the present embodiment includes two solid-state image sensors 30 (30a, 30b) that are physically separated as in the fifth embodiment, and an electrical board on which each solid-state image sensor 30 is mounted. A slit 43 is formed in a part of 40 as in the first embodiment.
About the manufacturing method of the two solid-state image sensors 30a and 30b, it is the same as that of 5th embodiment. Moreover, any of the electrical boards shown in FIGS. 3A and 3B may be used as the electrical board 40. The distance measuring device 90 can be manufactured in the same process as the fifth embodiment shown in FIG. Of course, instead of the focal length holding member 17, the focal length holding member shown in the second embodiment or the third embodiment may be applied.
As described above, according to the present embodiment, slits as buffer portions are formed in the electrical board, and the adjacent electrode pad groups are physically separated, so the influence of the thermal expansion of the electrical board 40 on the environmental temperature change. However, it becomes difficult to be transmitted to the solid-state imaging device 30, and the change in the baseline length D can be suppressed. Accordingly, it is possible to suppress a decrease in measurement accuracy with respect to a change in environmental temperature.

[Ranging system]
An example of a distance measuring system using the distance measuring apparatus shown in the first to sixth embodiments will be described. FIG. 13 is a configuration diagram of a ranging system equipped with a ranging device according to each embodiment of the present invention. In the following, an example in which the distance measuring device shown in the fifth embodiment is mounted will be described.
The distance measuring system 110 is electrically connected to the distance measuring device 80 and the electrical board 71, and performs a predetermined process on an electrical signal taken out from the electrical board 71. And a display terminal 113 that receives the processed electrical signal and displays information related to distance measurement.

The processing board 111 includes a distance calculation arithmetic circuit 45 and a digital signal processor (DSP) 47, receives an electrical signal from each imaging region 33, and forms a plurality of subject images captured by each imaging region 33. Based on this, calculations for distance determination and various image processing are performed. In the first embodiment (FIG. 1), an example of a distance measuring device in which a distance measuring arithmetic circuit and a DSP are mounted on an electrical board is shown. However, as shown in FIGS. The DSP may be separated from the electrical board.
The display terminal 113 may be a terminal having only a display function, or may be a terminal having an input function and various arithmetic functions. Examples of the latter include a touch panel type dedicated terminal and a computer device including a display. In the display terminal 113, for example, only a numerical value (distance) is a predetermined value based on a numerical value obtained by combining an image captured by the imaging region 33 and the numerical value, or an image captured by the imaging region 33. An image subjected to the above process is displayed.
Furthermore, you may provide the external communication part 115 which communicates between the process board | substrate 111 and an external apparatus not shown. For example, it is possible via the external communication unit 115 to provide a signal serving as a shooting trigger to the processing board 111, monitor the operation state of the processing board 111, and receive a determination result related to distance measurement from the processing board 111. It becomes. As the external device, for example, a control device such as a PLC (Programmable Logic Controller) can be used.

[Effects of the embodiment]
Hereinafter, the effect which each embodiment of the present invention has is explained in detail.
First, it has the effect of reducing the distortion generated between the spacing member and the solid-state image sensor due to the difference in linear expansion coefficient, and preventing the deterioration of the characteristics of the image sensor.
The optical sensor array that captures a subject image in Patent Document 1 is a solid-state imaging device (CCD), and the solid-state imaging device is formed on a silicon wafer, and therefore the linear expansion coefficient thereof is about 3 ppm / ° C. Further, the imaging lens, the interval holding member, and the CCD holding member are formed of the same resin material (amorphous cycloolefin polymer) having no hygroscopicity. Amorphous cycloolefin polymers include heat-resistant polycarbonate and ZEONEX (registered trademark of ZEON CORPORATION). Their linear expansion coefficient is about 70 ppm / ° C., which is about 20 times larger than the linear expansion coefficient of the base material (silicon) of the optical sensor array.
Thus, if the difference in linear expansion coefficient between the members joined to each other is large, each member is subject to thermal fatigue damage. In a device composed of a plurality of parts having different linear expansion coefficients, the problem of thermal stress accompanying a temperature change cannot be avoided. When restraint is strengthened to suppress thermal deformation, a large stress works, and destruction starts from a structurally weak place. On the other hand, if the constraint is weakened, a positional deviation occurs between the imaging lens and the solid-state imaging device, which causes a problem that destruction starts from a place where the constraint is weak and a problem that measurement reproducibility cannot be obtained.
In the embodiment of the present invention, the focal length holding member (the member corresponding to the lens holding member and the CCD holding member of Patent Document 1) is made substantially the same as the linear expansion coefficient of the solid-state imaging device, so that the focal length holding member is obtained. The thermal fatigue damage between the sensor and the image sensor is reduced.

Furthermore, in this embodiment, thermal fatigue damage is reduced by using two single lenses that are physically separated as the imaging lens.
That is, a glass lens or a resin lens is used as the imaging lens in the camera device. Glass and resin have a very large linear expansion coefficient compared with a solid-state image sensor. In other words, the linear expansion coefficient difference between the imaging lens and the focal length holding member is large. Therefore, in the distance measuring apparatus of the present embodiment, two physically separated single lenses are used. By physically separating the imaging lenses in this way, the distance between the imaging lenses is less affected by the linear expansion coefficient of the imaging lens. That is, the temperature dependence of the inter-lens distance is almost determined by the linear expansion coefficient of the focal length holding member, so that thermal fatigue damage is reduced and measurement accuracy is improved.

To explain using a specific example, when the base length D of the pair of lenses 103a and 103b shown in FIG. 14 is 5 mm and the lens aperture Φ of the lenses 103a and 103b is 1 mm, The lens length in the middle / left / right direction is 6 mm or more. Temporarily, when the length A of the joint surface between the imaging lens and the focal length holding member is 6 mm, the linear expansion coefficient α1 of the focal length holding member is 3 ppm / ° C., and the linear expansion coefficient α 2 of the imaging lens is 70 ppm / ° C., the temperature changes. When Δt is 10 ° C,
The amount of thermal expansion of the focal length holding member is
A × α1 × Δt = 6 mm × 3 ppm / ° C. × 10 ° C. = 0.18 μm Formula (2)
The thermal expansion of the imaging lens is
A × α2 × Δt = 6 mm × 70 ppm / ° C. × 10 ° C. = 4.2 μm Formula (3)
Therefore, from the formulas (2) and (3), in the case where the two imaging lenses are integrated, when there is a temperature change of 10 ° C., a heat of about 4 μm is generated between the focal length holding member and the imaging lens. An expansion difference will occur.

On the other hand, when the two imaging lenses are physically separated single lenses, the lens length in the left-right direction in the figure is determined by the lens aperture Φ, and in this example, the length is 1 mm or more. When the joint surface length A between the imaging lens and the focal length holding member is 1 mm, the linear expansion coefficient α1 of the focal length holding member is 3 ppm / ° C., and the linear expansion coefficient α 2 of the imaging lens is 70 ppm / ° C., the temperature change Δt is 10. If there was ℃,
The amount of thermal expansion of the focal length holding member is
A × α1 × Δt = 1 mm × 3 ppm / ° C. × 10 ° C. = 0.03 μm Formula (4)
The thermal expansion of the imaging lens is
A × α2 × Δt = 1 mm × 70 ppm / ° C. × 10 ° C. = 0.7 μm (5)
Therefore, from the equations (4) and (5), when the two imaging lenses are physically separated single lenses, when there is a temperature change of 10 ° C., the focal length holding member and the imaging lens Thus, a difference in thermal expansion of 0.67 μm occurs.

Therefore, when the temperature change Δt is 10 ° C., the difference in thermal expansion between the imaging lens and the focal length holding member is about 4 μm when the two imaging lenses are integrated, whereas the two imaging lenses are physically It can be seen that it is 0.67 μm in the case of a single lens separated into two.
As described above, by physically separating the imaging lens, the integrally continuous length of the imaging lens in the baseline length direction is shortened, and the continuous joining length with the focal length holding member is shortened. By doing so, thermal fatigue damage between the imaging lens and the focal length holding member is reduced.

Second, it has the effect of improving the ranging accuracy.
In Patent Document 1, the imaging lens, the interval holding member, and the CCD holding member are formed of the same resin material (amorphous cycloolefin polymer) that does not absorb moisture. Therefore, the change resulting from the environmental temperature of the base line length D (see FIG. 14) is determined by the linear expansion coefficient of the resin material forming these members. As described above, the linear expansion coefficient of the amorphous cycloolefin polymer is about 70 ppm / ° C.
For example, if the base line length D of the pair of lenses 103a and 103b shown in FIG. 14 is 5 mm, the distance L from the center of the lenses 103a and 103b to the subject is 5 m, and the focal length f of the lenses 103a and 103b is 5 mm, triangulation From equation (1) indicating the basic principle, the parallax δ is
δ = D · f / L = 5 mm · 5 mm / 5 m = 5 μm (6)
It becomes.
That is, in this distance measuring apparatus, when a parallax δ of 5 μm is detected, the distance L is recognized as 5 m.
For example, when resin is used for the spacing member as in the conventional example, assuming that the linear expansion coefficient α of the resin is 70 ppm / ° C., if the temperature change Δt is 10 ° C., the thermal expansion amount of the spacing member Is
D × α × Δt = 3.5 μm (7)
This is equivalent to a change in parallax of 3.5 μm.
As a result, if the temperature change is 10 ° C., a distance measurement error as large as 70% (= 3.5 μm / 5 μm) occurs even if the same distance of 5 m is measured.

On the other hand, in the present embodiment, the linear expansion coefficient of the focal length holding member (the member corresponding to the interval holding member and the CCD holding member in Patent Document 1) is approximately 3 ppm / ° C., which is substantially the same as the linear expansion coefficient of the solid-state imaging device. Is set to Therefore, since the linear expansion coefficient can be reduced as compared with the conventional example, the dependency of the measurement accuracy on the environmental temperature change can be reduced, and the distance measurement accuracy can be maintained even when the environmental temperature rises and falls.
When a material substantially the same as the linear expansion coefficient of the imaging elements 104a and 104b is used for the imaging distance holding member as in the present invention, assuming that the linear expansion coefficient α is 3 ppm / ° C., the temperature change Δt is 10 ° C. If there was
D × α × Δt = 0.15 μm (8)
This is equivalent to a change in parallax of 0.15 μm.
As a result, even if the same distance of 5 m is measured when the temperature change is 10 ° C., the measurement error falls within 3% (= 0.15 μm / 5 μm).

Third, it is possible to suppress an increase in cost due to an increase in the number of parts.
For example, in Patent Document 2, at least six components, ie, a single lens (two), a lens holder, a light shielding spacer, an imaging region (two solid-state imaging devices), a substrate, and an imaging device holder are required.
On the other hand, in the present invention, as shown in FIGS. 2, 5, and 6, the solid-state imaging device 30 (including the imaging lens 11 (two), the focal length holding member 17 (corresponding to the light shielding spacer), and the two imaging regions 33). 1 type) and 4 types and 6 parts of the electrical board 40 (2 pieces), the same or better performance as the conventional example can be obtained, and the number of parts can be reduced and the cost can be reduced.

Fourth, the apparatus can be reduced in size.
For example, in Patent Document 2, a solid-state image sensor is mounted on a substrate including a digital signal processor (DSP), and the substrate is mounted on an image sensor holder. Further, a light shielding spacer is joined to the image sensor holder so as to cover the outer periphery of the substrate. For this reason, the area of the imaging surface is a size obtained by adding the wall thickness of the light shielding spacer to the area of the substrate.
On the other hand, in the present invention, since the focal length holding members 17, 51, 61 are assembled according to the outer periphery of the solid-state image sensor 30, the area of the image pickup surface is the area of the solid-state image sensor 30. In other words, the area of the image pickup surface is the size obtained by adding the wall thickness of the focal length holding members 17, 51, 61 to the image pickup region 33, and the size of the electrical board 40 including the distance calculation arithmetic circuit 45 and the digital signal processor 47. It is decided regardless. Therefore, the apparatus can be downsized.

  DESCRIPTION OF SYMBOLS 10 ... Distance measuring device, 11 ... Imaging lens, 13 ... Side wall, 15 ... Aperture, 17 ... Focal length holding member, 19 ... Through-hole, 30 ... Solid-state image sensor, 31 ... Silicon wafer, 33 ... Imaging region, 35 ... Cover Glass, 37 ... Solder ball group, 40 ... Electrical board, 41 ... Electrode pad group, 43 ... Slit, 45 ... Calculation circuit for distance measurement, 47 ... Digital signal processor (DSP), 49 ... Underfill material, 50 ... Distance measurement Device: 51 ... Focal length holding member, 60 ... Distance measuring device, 61 ... Focal length holding member, 63 ... Base material, 65 ... Light shielding film, 70 ... Distance measuring device, 71 ... Electrical board, 80 ... Distance measuring device, DESCRIPTION OF SYMBOLS 90 ... Ranging device, 101 ... Subject, 102 ... Camera, 103 ... Lens, 104 ... Imaging device, 106 ... Base substrate, 107 ... Subject image, 108 ... Optical axis, 110 ... Ranging system, 111 ... Processing substrate 113 ... display terminal, 115 ... external communication unit, D ... base line length, f ... focal length, X ... optical axis

JP-A-11-281351 WO2006 / 046396

Claims (8)

A camera apparatus comprising: an imaging lens; a solid-state imaging device having an imaging region for imaging a subject image incident on the imaging lens; and a focal length holding member that holds an interval between the imaging lens and the solid-state imaging device Because
The focal length holding member is fixed to the solid-state image sensor, and has a linear expansion coefficient substantially the same as the main material of the solid-state image sensor. A plurality of the imaging lenses spaced apart from each other;
The camera device according to claim 1, wherein the solid-state imaging device has a plurality of imaging regions that respectively capture subject images incident on the imaging lenses. The focal length holding member is made of silicon,
The through-hole serving as an optical path for guiding the subject image incident on the imaging lens to the imaging region is formed in the focal length holding member in the optical axis direction. Camera device. The focal length holding member is made of silicon carbide or silicon nitride ceramics,
The through-hole serving as an optical path for guiding the subject image incident on the imaging lens to the imaging region is formed in the focal length holding member in the optical axis direction. Camera device.   The camera apparatus according to claim 1, wherein the focal length holding member is made of a glass material of AF45, Tempax glass, or Pyrex (registered trademark) glass.   The camera apparatus according to claim 2, wherein each of the imaging regions is formed on the same substrate. It has a plurality of electrode pad groups corresponding to each imaging region, and includes an electrical board on which the solid-state imaging device is mounted across each electrode pad group,
The camera device according to claim 2, wherein the electrical board has a buffer portion formed between the electrode pad groups. The camera device according to any one of claims 1 to 7,
A ranging apparatus comprising: a ranging calculation circuit that processes an electrical signal from the imaging region; and a digital signal processor.

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