JP4466394B2 - Cooled imaging device - Google Patents

Description

  The present invention relates to a cooling type imaging apparatus having a function of cooling an imaging element.

  In the conventional cooling type imaging device disclosed in Patent Document 1, the dark current is reduced and the performance of the imaging element is maintained by cooling the imaging element using an electronic cooling element such as a Peltier element. . When the imaging device is cooled, moisture that has entered the apparatus from the external environment (in the atmosphere) may cause condensation on the imaging surface of the imaging device. Therefore, in this conventional apparatus, the boundary portion of the housing of the image pickup apparatus is simply sealed with an O-ring or the like, and a heat conduction member that cools to a lower temperature than the image pickup element is provided, and the heat conduction member and the Peltier element itself are provided. By dew condensation, the amount of water vapor inside the image pickup apparatus is reduced, and condensation of the image pickup element is prevented.

JP-A-9-162379 (second page, FIG. 1)

  In the technique of Patent Document 1, a single sealed structure space that is simply sealed with an O-ring or the like is formed in the imaging device, and the Peltier element or the imaging device is accommodated in the space. There is a problem that the moisture of the outside air easily enters, and as a result, when the invaded water vapor condenses on the heat conducting member and the Peltier element, the Peltier element is likely to deteriorate.

(1) The cooling type imaging device according to the first aspect of the present invention forms a first sealed chamber sealed to the outside by joining a plurality of divided members via a sealing member. An external housing, and an internal housing that forms a second sealed chamber in the first sealed chamber that is sealed with respect to the first sealed chamber by joining a plurality of divided members via the sealing member. And an image sensor housed in the second sealed chamber, and a cooling element housed in the second sealed chamber and cooling the image sensor.
(2) According to a second aspect of the present invention, in the cooling type imaging apparatus according to the first aspect, the first sealed chamber and the second sealed chamber are filled with a dry gas.
(3) The invention according to claim 3 is the cooling type imaging apparatus according to claim 1 or 2, wherein the first sealed chamber includes an airtight chamber and a buffer chamber formed in a substantially sealed state with the airtight chamber. The housing is provided with a first optical window for introducing incident light into the image sensor facing the buffer chamber, and the second optical window for introducing incident light into the image sensor is provided in the internal housing. The first optical window is provided so as to be detachable, and the second optical window is provided with optical glass.
(4) The invention of claim 4 is the cooling type imaging device according to any one of claims 1 to 3, wherein a dehumidifying device for dehumidifying the first sealed chamber is installed in the external housing. To do.

  According to the present invention, since the second sealed chamber that houses the imaging element and the cooling element is covered with the first sealed chamber, moisture in the outside air can enter the second sealed chamber. It can be greatly reduced and condensation in the second sealed chamber can be suppressed.

Hereinafter, a cooling type imaging apparatus according to the present invention will be described with reference to FIGS. In the figure, the same components are denoted by the same reference numerals.
<First Embodiment>
1A and 1B are diagrams schematically showing the structure of a cooling type imaging apparatus according to a first embodiment of the present invention, where FIG. 1A is a longitudinal sectional view and FIG. 1B is a bottom view. FIG. 2 is an enlarged view of FIG. In FIG. 1A and FIG. 2, the subject side imaged by the photographing lens 101 is referred to as the front of the cooling type imaging apparatus 100.

  The cooling type imaging apparatus 100 according to the first embodiment is sealed with respect to the outer casing 7 which is a main part forming the first sealed chamber B sealed against the outside air and the first sealed chamber B. The inner casing 3 which is a main part forming the second sealed chamber A, and the imaging element 1 and the Peltier element 2 disposed in the second sealed chamber A are provided. The internal housing 3 has a front member 3a and a rear member 3b, and the external housing 7 has a front cover 7a and a rear cover 7b.

  The outer casing 7 is configured by fastening the front cover 7a and the rear cover 7b with an unillustrated screw through an O-ring 10c that is a sealing member. In front of the front cover 7a, a first optical window for introducing the light L into the imaging device 1 is opened, and this opening is closed by a lens mount 9 to which an optical filter 8 is attached.

  The lens mount 9 is brought into close contact with the front cover 7a through an O-ring 10d and fastened by a screw 11d (see FIG. 1B), and the optical filter 8 is brought into close contact with the lens mount 9 through an O-ring 10e. Fastened with screws 11e. That is, the optical filter 8 is attached to the front cover 7 a via the lens mount 9. With the above configuration, the hermetic chamber B is kept airtight by using the O-rings 10c, 10d, and 10e.

  The optical filter 8 is an infrared cut filter, and cuts light in a long wavelength range exceeding a predetermined wavelength. The infrared cut filter can change the spectral characteristics of light incident on the imaging surface by changing its thickness. The lens mount 9 has a cover filter 9 a disposed in front of the optical filter 8.

  The internal housing 3 provided in the sealed chamber B is configured by joining the front member 3a and the rear member 3b via an O-ring 10a that is a sealing member and fastening them with screws 11a. A second optical window for introducing light L into the imaging element 1 is opened in the front member 3 a, and this opening is closed by the optical glass plate 4. That is, for example, the optical glass plate 4 made of quartz glass or a glass material having mechanical strength and weather resistance is brought into close contact with the front member 3a via the O-ring 10b and then fastened to the front member 3a by the screw 11b. Thereby, the sealed chamber A is formed by the front member 3a, the rear member 3b, and the optical glass plate 4, and airtightness is maintained by using the O-rings 10a and 10b.

  In the sealed chamber A, a circuit board 2a screwed to the front member 3a with a screw 2b is provided, and the imaging element 1 and the Peltier element 2 are mounted on the circuit board 2a. Circuits for controlling the image sensor 1 and the Peltier element 2 are mounted on the circuit board 2a. In mounting the image pickup device 1 and the Peltier device 2 on the substrate 2a, as shown in the figure, the heat absorption surface of the Peltier device 2 is adhered or adhered to the package 1a that houses the image pickup device 1, and the heat dissipation surface of the Peltier device 2 is The heat transfer sheet 2c is in close contact with the rear member 3b. The rear member 3b is integrally provided with a heat transfer member 5 at the rear thereof, and the rear surface of the heat transfer member 5 is in close contact with the rear cover 7b.

  With the above configuration, the imaging device 1 and the Peltier device 2 are housed in the sealed chamber A formed by the front member 3a, the rear member 3b, the optical glass plate 4, and the O-rings 10a and 10b. The cover 7a, the rear cover 7b, the lens mount 9 on which the optical filter 8 is mounted, and the O-ring 10c are provided in the sealed chamber B.

  The rear member 3b is provided with a sealing port 14 for sealing gas in the sealed chamber A, and after exhausting the inside of the sealed chamber A through the sealed port 14, dry nitrogen or dry air is supplied to the sealed chamber A. The filling port 14 is closed after filling. The rear cover 7b is also provided with a sealing port 15 for sealing gas into the sealed chamber B. After exhausting the inside of the sealed chamber B, the sealed chamber B is filled with dry nitrogen or dry air and sealed after filling. The inlet 15 is closed. That is, the insides of the sealed chambers A and B are purged with dry nitrogen or dry air at the time of shipment.

  In the cooling type imaging device 100 having the above structure, the light L that has passed through the photographing lens 101 sequentially passes through the cover filter 9a, the optical filter 8, and the optical glass plate 4, and passes through the opening K (see FIG. 1B). It passes through and forms an image on the imaging surface of the imaging device 1. In the image pickup device 1 such as a CCD, a weak dark current flows during operation even if there is no light input. The reason why the image pickup device 1 is cooled by the Peltier device 2 is to reduce the dark current by lowering the temperature of the image pickup device 1 and to improve the S / N ratio of the video signal.

  The lowest temperature inside the cooling type imaging device 100 is the heat absorption surface of the Peltier element 2 and the contact surface or adhesive surface on the back side of the package 1a in contact therewith. The heat absorbed from the adhesion surface or the adhesion surface of the package 1a is transmitted from the heat dissipation surface of the Peltier element 2 to the heat transfer member 5 integrated with the rear member 3b, and further transferred from the heat transfer member 5 to the rear cover 7b, to the outside of the apparatus. Heat is dissipated.

  Therefore, if moisture exists in the sealed chamber A over a certain level, the water vapor becomes supersaturated in a low temperature region, and condensation occurs in the imaging device 1 and the Peltier device 2. If condensation occurs, the imaging surface of the image sensor 1 may become cloudy and image quality may deteriorate. If the condensation continues for a long time, the performance of the image sensor 1 or the Peltier element 2 may be deteriorated or the life may be shortened.

In the imaging apparatus 100 according to the first embodiment, the sealed chamber A is formed in the sealed chamber B formed by the outer casing 7 so as to be shielded from the outside air as a double sealed structure. The image pickup device 1 and the Peltier device 2 are arranged inside. In other words, the imaging device 1 and the Peltier device 2 are arranged in a sealed chamber A having a double sealed structure that is sealed using a sealing member typified by an O-ring or the like. Therefore, it is difficult for moisture contained in the outside air to enter the sealed chamber A, and it is possible to suppress dew condensation on the imaging device 1 and the Peltier device 2. As a result, it is possible to suppress performance deterioration and shortening of the lifetime of the image sensor 1 and the Peltier element 2.
Further, by filling these sealed chambers A and B with dry nitrogen or dry air at the time of shipment, the inside of the sealed chamber A can be kept in the dry state as shipped even if time passes.

<Second Embodiment>
FIG. 3 is a longitudinal sectional view schematically showing the structure of the cooling type imaging apparatus according to the second embodiment of the present invention. The cooling type imaging device 200 according to the second embodiment has the same basic configuration as the cooling type imaging device 100 according to the first embodiment, but the major difference is that the optical filter 8 can be replaced. is there.

  The cooling type imaging apparatus 200 according to the second embodiment is sealed with respect to the external casing 27 which is a main part forming the first sealed chamber D sealed against the outside air, and the first sealed chamber D. The inner casing 23 which is a main part forming the second sealed chamber C, and the imaging element 1 and the Peltier element 2 disposed in the second sealed chamber C are provided. The internal housing 23 has a front member 23a and a rear member 23b, and the external housing 27 has a front cover 27a and a rear cover 27b.

  The outer casing 27 is configured by fastening the front cover 27a and the rear cover 27b with an unillustrated screw through an O-ring 30c that is a sealing member. In front of the front cover 27a, a first optical window for introducing the light L into the image sensor 1 is opened. In this opening, the optical filter 8 is replaceably mounted by fastening the holding ring 8a to the front cover 27a with a screw 8b. Note that an O-ring (not shown) is interposed between the optical filter 8 and the front cover 27a, whereby the first optical window and thus the sealed chamber D are sealed from the outside air. A lens mount 29 is screwed onto the front cover 27a.

  The internal casing 23 provided in the sealed chamber D seals the circuit board 22a on which the imaging element 1 and the Peltier element 2 are mounted between the front member 23a and the rear member 23b by O-rings 30a and 30b. And are fastened to each other by screws 31a. A second optical window for introducing light L into the imaging element 1 is opened in the front member 23 a, and this opening is closed by the optical glass plate 24. Thereby, the sealed chamber C is formed by the front member 23a, the rear member 23b, and the optical glass plate 24, and the airtightness is maintained by using the O-rings 30a and 30b. Note that the second optical window is disposed to face the first optical window.

  The front member 23a and the front cover 27a are fixed in contact with each other in the surface area P by fastening with a screw (not shown), and the front chamber 23a, the optical glass plate 24, the front cover 27a, and the optical filter 8 are used as a buffer chamber. D2 is formed. The buffer chamber D2 constitutes a part of the sealed chamber D, and a space excluding the buffer chamber D2 is referred to as an airtight chamber D1. That is, the sealed chamber D includes an airtight chamber D1 and a buffer chamber D2. And as above-mentioned, the buffer chamber D2 is formed by making the front member 23a surface-contact with the front cover 27a and fastening in the area | region shown by the code | symbol P of FIG. 3, The buffer chamber D2 and the airtight chamber D1 are It can be considered as a space adjacent to each other in a substantially airtight state.

  As in the first embodiment, the heat absorbing surface of the Peltier element 2 is in close contact with or bonded to the package 1a that accommodates the imaging element 1, and the heat radiating surface of the Peltier element 2 is connected to the rear member 23b via the heat transfer sheet 2c. Is in close contact. The rear member 23b is integrally provided with a heat transfer member 25 at a rear portion thereof, and the heat transfer member 25 is in close contact with the rear cover 27b.

  Similarly to the first embodiment, the rear member 23b is provided with a sealing port 34 for sealing gas into the sealed chamber C, and after the inside of the sealed chamber C is exhausted through the sealed port 34. The sealed chamber C is filled with dry nitrogen or dry air, and the filling port 34 is closed after filling. The rear cover 27b is also provided with a sealing port 35 for sealing gas into the sealed chamber D. After exhausting the inside of the sealed chamber D, the sealed chamber D is filled with dry nitrogen or dry air and sealed after filling. The inlet 35 is closed. That is, the insides of the sealed chambers C and D are purged with dry nitrogen or dry air at the time of shipment.

  As described above, the imaging device 1 and the Peltier device 2 are double-blocked from the outside air by being arranged in the sealed chamber C formed in the sealed chamber D.

  Next, replacement work of the optical filter 8 in the cooling type imaging apparatus 200 will be described. First, the screw-type lens mount 29 is removed from the front cover 27a, and then the screw 8b is loosened and removed, and the press ring 8a and the optical filter 8 are taken out. Then, another optical filter is attached instead of the optical filter 8 and the lens mount 29 is attached in the reverse procedure of the removal. At the time of replacement, the buffer chamber D2 is opened to the atmosphere. However, as described above, the buffer chamber D2 and the airtight chamber D1 are in a substantially airtight state, and outside air, that is, moisture in the outside air enters the airtight chamber D1. Can be suppressed.

  Note that the transfer of moisture from the buffer chamber D2 to the airtight chamber D1 depends on the degree of adhesion in the surface contact region P between the front member 23a and the front cover 27a, and therefore when the buffer chamber D2 is temporarily opened. It is desirable that the amount of water transferred from the buffer chamber D2 to the hermetic chamber D1 is designed to be extremely small.

  In the cooling type imaging apparatus 200 according to the present embodiment, the incident light path of the light L to the imaging element 1, the cooling of the imaging element 1 by the Peltier element 2, the heat conduction from the Peltier element 2 to the rear cover 27b, etc. are the first. Since it is the same as that of the cooling type imaging device 100 according to the embodiment, the description is omitted.

  In the cooling type imaging apparatus 200 according to the present embodiment, the imaging element 1 and the Peltier element 2 are arranged in the sealed chamber C having a double sealed structure, and thus, similar to the cooling type imaging apparatus 100 according to the first embodiment. Has the effect of. The buffer chamber D2 is provided so that the airtight chamber D1 is not opened to the atmosphere when the optical filter 8 is replaced. Since the buffer chamber D2 and the airtight chamber D1 are in a substantially airtight state, even in the cooling type image pickup device 200 in which the optical filter 8 is exchangeable, the arrangement space of the image pickup device 1 and the Peltier device 2 is outside air. Can be isolated as a double sealed structure space, and dew condensation on the Peltier element 2 can be suppressed.

  In addition, since the airtightness between the buffer chamber D2 and the outside air is not necessarily essential, a thin filter with low rigidity can be used, and the accompanying effect that the degree of freedom of selection as the optical filter 8 increases can be obtained.

Next, modifications of the first and second embodiments will be described.
FIG. 4 is a longitudinal sectional view schematically showing the structure of a modified example of the cooling type imaging apparatus 100 according to the first embodiment. The cooling type imaging device 100 </ b> A is configured by adding a dehumidifier 40 to the cooling type imaging device 100. Therefore, the description which overlaps with the content described in the first embodiment is omitted, and the description will focus on the different points.

  The dehumidifier 40 is attached to the front cover 7a and dehumidifies the sealed chamber B. As the dehumidifier 40, for example, a device (product for dehumidification) by electrochemically decomposing moisture in the sealed chamber B into oxygen, hydrogen ions, and electrons, and transferring (releasing) hydrogen ions to the outside of the front cover 7a. Name: Rosale, manufactured by Mitsubishi Electric Corporation). In the cooling type imaging device 100A, the sealed chamber B is kept at a low humidity by the dehumidifier 40, so that the moisture content in the sealed chamber A is reduced as compared with the cooling type imaging device 100 according to the first embodiment. be able to. As a result, it is possible to further prevent the image sensor 1 and the Peltier element 2 from condensing. Of course, the above modification can also be applied to the cooling type imaging apparatus 200 according to the second embodiment.

  Regarding the correspondence between the claims and the components according to the embodiment, the sealed chambers A and C correspond to the second sealed chamber, and the sealed chambers B and D correspond to the first sealed chamber, respectively. Further, the O-rings 10a, 10c, 30a, 30b, and 30c correspond to sealing members. The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the above embodiment and the items described in the claims.

It is a figure which shows typically the structure of the cooling type imaging device which concerns on the 1st Embodiment of this invention, (a) is a longitudinal cross-sectional view, (b) is a bottom view. It is a figure which expands and shows Fig.1 (a). It is a longitudinal cross-sectional view which shows typically the structure of the cooling type imaging device which concerns on the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows typically the structure of the modification of the cooling type imaging device 100 by 1st Embodiment.

Explanation of symbols

1: Image sensor 2: Peltier element 3, 23: Internal housing 3a, 23a: Front member 3b, 23b: Rear member 4, 24: Optical glass plate 5, 25: Heat transfer member 7, 27: External casing 7a, 27a : Front cover 7b, 27b: Rear cover 8: Optical filter 9, 29: Lens mount 10a to 10e, 30a to 30c: O-ring 14, 15, 34, 35: Filling port 40: Dehumidifier 100, 200, 100A: Cooling Type imaging device 101: photographing lens A, B, C, D: sealed chamber D1: airtight chamber D2: buffer chamber K: opening L: light

Claims (4)

An external housing that forms a first sealed chamber sealed against the outside by joining a plurality of divided members via the sealing member;
An internal housing that forms a second sealed chamber in the first sealed chamber, which is sealed with respect to the first sealed chamber, by joining a plurality of divided members via a sealing member;
An image sensor housed in the second sealed chamber;
A cooling type imaging apparatus comprising: a cooling element that is housed in the second sealed chamber and that cools the imaging element. The cooling type imaging apparatus according to claim 1,
A cooling type imaging apparatus, wherein the first sealed chamber and the second sealed chamber are filled with a dry gas. The cooling type imaging apparatus according to claim 1,
The first sealed chamber includes an airtight chamber, and a buffer chamber formed in a substantially sealed state with the airtight chamber,
The external casing is provided with a first optical window for introducing incident light into the imaging element so as to face the buffer chamber,
The internal housing is provided with a second optical window for introducing incident light into the imaging element, facing the first optical window,
A cooling type imaging apparatus, wherein an optical filter is detachably provided in the first optical window, and optical glass is provided in the second optical window. In the cooling type imaging device according to any one of claims 1 to 3,
The cooling type imaging apparatus, wherein a dehumidifying device for dehumidifying the first sealed chamber is installed in the external casing.

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