JP2008244770A - Manufacturing method of optical apparatus, optical element, and cover member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress foreign substance from sticking onto the surface of an optical filter and the surface of a cover glass of an imaging element without adversely affecting optically. <P>SOLUTION: In a digital single-lens reflex camera, an SiO<SB>2</SB>particulate sedimentary layer 11a is film-made on the surface of a focal plane shutter 50 side (subject side) of the optical element 11. The SiO<SB>2</SB>particulate sedimentary layer 11a is formed on the surface of the optical element 11 by a laser ablation method, wherein thickness is about 1 nm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical device such as a digital camera, an optical element, and a cover member. More specifically, the present invention relates to a surface of a solid-state imaging device incorporated in the optical device, and a surface of an optical element such as an optical filter and a lens. The present invention relates to a technique for suppressing foreign matter from adhering.

  In the interchangeable-lens digital single-lens reflex camera, when a foreign substance such as dust adheres to the vicinity of the focal plane of the photographing lens, there is a problem that the shadow of the foreign substance is reflected in a captured image obtained by the imaging element. Such foreign matter is caused by dust entering from the outside when the lens is replaced, or fine wear powder such as resin, which is the structural member, is generated with the operation of the shutter and mirror inside the camera. It is considered.

  The foreign matter generated due to the above-described causes particularly enters between the cover glass for protecting the image pickup device and an optical filter such as an infrared cut filter or an optical low-pass filter disposed on the front surface of the cover glass. Sometimes. In that case, the camera had to be disassembled to remove the foreign matter. For this reason, it has been extremely effective to provide a sealed structure so that foreign matter does not enter between the cover glass of the image sensor and the optical filter.

  However, if a foreign object adheres to the surface of the optical filter opposite to the side facing the image sensor, the problem still remains that the foreign object appears as a shadow if it is in the vicinity of the focal plane. Yes.

Japanese Unexamined Patent Publication No. 2003-005254 (page 8, FIG. 1 and FIG. 10) JP 2000-029132 A (page 8, FIG. 2) JP 2003-328116 A

  In order to solve the above-mentioned problems, there is one that cleans the cover glass surface of the image sensor with a wiper (see Patent Document 1). By configuring the camera in this way, it is possible to remove foreign matter attached to the cover glass surface of the image sensor or the outermost surface of the dust-proof structure (for example, the surface of the optical filter) without removing the lens and without disassembling the camera.

  However, in the technique disclosed in Patent Document 1, the cover glass surface of the image sensor and the outermost surface of the dustproof structure are rubbed with a wiper. Therefore, for example, when a hard foreign material such as a metal powder adheres, the foreign material may damage the cover glass surface of the image sensor or the outermost surface of the dust-proof structure. In addition, since the foreign matter removed by the wiper floats in the camera, there is a problem that the foreign matter once removed is reattached to the cover glass surface of the image sensor and the outermost surface of the dust-proof structure.

  Therefore, in order to suppress the adhesion of foreign matter, there is one in which a transparent electrode is formed on each of the cover glass surface of the image sensor and the surface of the optical filter (see Patent Document 2). By applying a potential to the transparent electrode provided on the cover glass surface of the image sensor and the surface of the optical filter, static electricity generated on the cover glass surface of the image sensor and the surface of the optical filter is neutralized. Thereby, it becomes possible to suppress adhesion of foreign matters to the cover glass surface of the image sensor and the surface of the optical filter.

  However, in the technique disclosed in Patent Document 2, since a transparent electrode is provided on the surface of the cover glass and the surface of the optical filter, an optical adverse effect such as a decrease in light transmittance to the image sensor occurs. Further, static electricity generated on the surface of the cover glass of the image sensor and the surface of the optical filter is not constant depending on the surrounding environment (temperature and humidity) and usage conditions. For this reason, there is a problem that control for neutralizing static electricity becomes difficult, and the suppression effect becomes insufficient due to static electricity not being neutralized.

  The present invention has been made in view of the above points, and an object thereof is to suppress adhesion of foreign matters to the surface of an optical filter or the cover glass of an image pickup element without causing an adverse optical effect. And

An optical device manufacturing method according to the present invention is an optical device manufacturing method including an imaging unit that converts an optical image of a subject into an electrical signal, and an optical element disposed on a front surface of the imaging unit, It is characterized by having a step of forming a fine particle deposition layer on the object side surface of the optical element by laser ablation.
Another method of manufacturing an optical device according to the present invention is a method of manufacturing an optical device including an imaging unit that converts an optical image of a subject into an electrical signal, the imaging unit including an imaging element and a cover for the imaging element. And a particulate deposition layer is formed on the surface of the cover member on the subject side by a laser ablation method.
The optical element of the present invention is used in an optical apparatus having an imaging unit that converts an optical image of a subject into an electrical signal, and is disposed on the subject side with respect to the imaging unit and has a laser on a surface on the subject side. A fine particle deposition layer is formed by an ablation method.
The cover member of the image pickup means of the present invention is used in an optical device having an image pickup means for converting an optical image of a subject into an electric signal, and is disposed on the subject side with respect to the image pickup element constituting the image pickup means, and A fine particle deposition layer is formed on the surface on the object side by a laser ablation method.

  According to the present invention, since the fine particle deposition layer is formed by the laser ablation method on the surface of the optical element on the subject side or on the subject side of the imaging means, there is no adverse optical effect, and the subject side surface of the optical element or the imaging is performed. The adhesion force of foreign matter to the surface of the means on the subject side can be reduced, and foreign matter such as dust can be prevented from adhering.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram illustrating a system configuration of a lens interchangeable digital single-lens reflex camera (D-SLR) according to the present embodiment. As shown in FIG. 1, the D-SLR of the present embodiment includes a camera body 100 and a lens device 102 that is detachably attached to the camera body 100. The D-SLR is a single-plate digital color camera using an image sensor such as a CCD or CMOS sensor, and obtains an image signal representing a moving image or a still image by driving the image sensor continuously or once. Here, the imaging element is an area sensor of a type that converts the exposed light into an electrical signal for each pixel, accumulates charges according to the amount of received light, and reads the accumulated charges.

  In FIG. 1, a lens device 102 is detachably attached to a mount mechanism 101 of the camera body 100. The lens device 102 is electrically and mechanically connected to the camera body 100 via the mount mechanism 101. By attaching the lens apparatus 102 having different focal lengths to the camera body 100, it is possible to obtain shooting screens having various angles of view.

  In the camera body 100, a half mirror 111, a sub mirror 122, a focal plane shutter 50, and an imaging unit 10 are disposed on the optical axis L1. The imaging unit 10 includes an optical element 11 and an imaging element 15, which will be described in detail later. A cutoff frequency is set in the optical axis L <b> 1 from the diaphragm 104 of the lens device 102 and the imaging optical system 103 to the solid-state imaging device 15. The limiting optical element 11 is arranged. Thereby, it is possible to prevent a spatial frequency component higher than necessary of the object image (optical image) from being transmitted onto the solid-state imaging device 15.

  The signal read from the solid-state imaging device 15 is displayed on the display unit 107 as image data after being subjected to predetermined processing as will be described later. The display unit 107 is attached to the rear surface of the camera body 100 so that the user can directly observe the display on the display unit 107. If the display unit 107 is composed of an organic EL spatial modulation element, a liquid crystal spatial modulation element, a spatial modulation element using fine particle electrophoresis, or the like, power consumption can be reduced and the display unit 107 can be made thin. be able to. Thereby, power saving and size reduction of D-SLR can be achieved.

  Specifically, the solid-state imaging device 15 is a CMOS process compatible sensor (abbreviated as a CMOS sensor), which is one of amplification type imaging devices. One of the features of the CMOS sensor is that the MOS transistors in the area sensor and the peripheral circuits such as the imaging device drive circuit, AD converter circuit, and image processing circuit can be formed in the same process. It can be greatly reduced. In addition, it has a feature that random access to an arbitrary pixel is possible, reading out for a display is easy, and real-time display can be performed at a high display rate in the display unit 107. The solid-state imaging device 15 utilizes the above-described features, and performs a display image output operation (reading out a part of the light receiving region of the solid-state imaging device 15) and a high-definition image output operation (reading out in the entire light receiving region). )I do.

  The movable half mirror 111 reflects a part of the light beam from the photographing optical system 103 and transmits the rest. The half mirror 111 has a refractive index of about 1.5 and a thickness of about 0.5 mm.

  A focusing screen 105 is disposed on the planned image formation surface of the object image formed by the reflection of the half mirror 111, and a pentaprism 112 is disposed above the focusing screen 105. The object image formed on the focusing screen 105 can be observed by the finder lens 109. The finder lens 109 is composed of one or a plurality of finder lenses (not shown). The focusing screen 105, the pentaprism 112, and the finder lens 109 constitute a finder optical system. Further, specific information is displayed on the focusing screen 105 by the information display unit 180 in the optical viewfinder.

  A movable sub-mirror 121 is arranged behind the half mirror 111 (on the image plane side), and reflects a light beam that passes through the half mirror 111 near the optical axis L 1 and guides it to the focus detection unit 121. The sub mirror 122 rotates around a rotation shaft provided on a holding member (not shown) of the half mirror 111 and moves in conjunction with the movement of the half mirror 111. The focus detection unit 121 receives the light beam from the sub-mirror 122 and performs focus detection by the phase difference detection method.

  The optical path splitting system composed of the half mirror 111 and the sub mirror 122 is for the first optical path splitting state for guiding light to the finder optical system and for directing the light flux from the imaging lens (not shown) directly to the solid-state imaging device 15. A second optical path division state (positions indicated by broken lines in FIG. 2: 111 ′ and 122 ′) retracted from the photographing optical path can be taken.

  A movable flash light emitting unit 114 is provided on the upper part of the camera body 100. The flash light emitting unit 114 is movable between a storage position stored in the camera body 100 and a light emission position protruding from the camera body 100.

  The main switch 119 is a switch for starting up the D-SLR. The release button 120 is a button that is pressed in two stages. A shooting preparation operation (photometry operation, focus adjustment operation, etc.) is started by a half-press operation, and a shooting operation (read from the solid-state imaging device 15 is read by a full-press operation. Recording of the recorded image data on the recording medium) is started.

  FIG. 2 is a side sectional view for explaining a schematic configuration of the imaging unit 10 and the focal plane shutter 50 of the digital single-lens reflex camera according to the embodiment of the present invention. As shown in FIG. 2, in the imaging unit 10, reference numeral 11 denotes a thin plate-shaped optical element. Reference numeral 12 denotes a holding member 12 that holds the optical element 11. Reference numeral 13 denotes a support plate, which integrates the optical element 11 and the holding member 12 in contact with the surface of the optical element 11. A solid-state imaging device 15 includes an imaging element 15b, a cover member 15a for protecting the imaging element 15b, and a connection terminal 15c. Reference numeral 16 denotes a seal member that seals between the cover member 15 a of the solid-state imaging device 15 and the optical element 11. Reference numeral 17 denotes a substrate, to which the connection terminal 15c of the solid-state imaging device 15 is connected, and an electrical element constituting a control circuit that controls the operation of the D-SLR is mounted. Reference numeral 18 denotes a holding plate, which is integrated with the solid-state imaging device 15 and fixed to the D-SLR chassis (not shown) with screws (not shown).

On the surface of the optical element 11 on the focal plane shutter 50 side (subject side), a SiO ₂ fine particle deposition layer 11a is formed. The SiO ₂ fine particle deposition layer 11a is formed on the surface of the optical element 11 by a laser ablation method, and has a thickness of about 1 nm.

  On the other hand, in the focal plane shutter 50, reference numeral 21 denotes a front curtain, which includes a plurality of shutter blades 21a to 21d. A rear curtain 22 is composed of a plurality of shutter blades as in the front curtain 21. Reference numeral 23 denotes an intermediate plate that divides the drive space of the front curtain 21 and the rear curtain 22. Reference numeral 24 denotes a presser plate for the rear curtain 22, and an opening is provided at a substantially central portion for imaging. Reference numeral 25 denotes a presser plate for the front curtain 21, and an opening is provided at a substantially central portion for imaging. Reference numeral 29 denotes a stopper rubber having a stopper portion which is positioned when the shutter blades 21a to 21d of the front curtain 21 are opened.

  FIG. 3 is a block diagram showing an electrical configuration of the digital single-lens reflex camera according to the present embodiment. With reference to FIG. 3, the part regarding the imaging and recording of the D-SLR 100 according to the present embodiment will be described. The D-SLR 100 includes an imaging system, an image processing system, a recording / reproducing system, and a control system. The imaging system includes a photographing optical system 103 and a solid-state imaging device 15. The image processing system includes an A / D converter 130, an RGB image processing circuit 131, and a YC processing circuit 132. The recording / reproducing system includes a recording processing circuit 133 and a reproduction processing circuit 134. The control system includes a camera system control circuit 135, an operation detection circuit 136, and an imaging device drive circuit 137.

  The connection terminal 138 is connected to an external computer or the like, and is standardized for transmitting and receiving data. The electric circuit described above is driven by receiving power from a small fuel cell (not shown).

  The imaging system is an optical processing system that forms an image of light from an object on the imaging surface of the solid-state imaging device 15 via the imaging optical system 103. The driving of the diaphragm 104 is controlled via the diaphragm driving source 143, and the driving of the focal plane shutter 50 is controlled via the shutter control circuit 145 as necessary. Receive light with.

  As the solid-state imaging device 15, an imaging element having 3700 square pixels arranged in the long-side direction and 2800 pixels in the short-side direction and having a total number of about 10 million pixels is used. Then, R (red), G (green), and B (blue) color filters are alternately arranged in each pixel, thereby forming a so-called Bayer array in which four pixels form a set. In the Bayer array, the overall image performance is improved by arranging more G pixels that are easily felt when an observer looks at the image than R pixels and B pixels. In general, in image processing using this type of image sensor, a luminance signal is generated mainly from G, and a color signal is generated from R, G, and B.

  The signal read from the solid-state imaging device 15 is supplied to the image processing system via the A / D converter 130, and image data is generated by image processing by this image processing system. The A / D converter 130 converts, for example, an output signal of the solid-state imaging device 15 into a 10-bit digital signal according to the amplitude of the signal read from each pixel of the solid-state imaging device 15, and outputs the signal. It is. The subsequent image processing is executed by digital processing.

  The image processing system is a processing system that obtains an image signal of a desired format from R, G, and B digital signals. The color signal of R, G, and B is converted into a luminance signal Y and a color difference signal (R−Y), (B -Y), and the like.

  The RGB image processing circuit 131 is a signal processing circuit that processes the output signal of the A / D converter 130. The RGB image processing circuit 131 includes a white balance circuit, a gamma correction circuit, and an interpolation calculation circuit that performs high resolution by interpolation calculation.

  The YC processing circuit 132 is a signal processing circuit that generates a luminance signal Y and color difference signals RY and BY. The YC processing circuit 132 includes a high-frequency luminance signal generation circuit that generates a high-frequency luminance signal YH, a low-frequency luminance signal generation circuit that generates a low-frequency luminance signal YL, and a color difference signal that generates color difference signals RY and BY. A generator circuit; The luminance signal Y is formed by combining the high frequency luminance signal YH and the low frequency luminance signal YL.

  The recording / reproducing system is a processing system that outputs an image signal to a memory (not shown) and outputs an image signal to the display unit 107. The recording processing circuit 133 performs a writing process and a reading process of the image signal to the memory. The reproduction processing circuit 134 reproduces the image signal read from the memory and outputs it to the display unit 107.

  The recording processing circuit 133 includes a compression / expansion circuit for compressing YC signals representing still image data and moving image data in a predetermined compression format and expanding the compressed data. The compression / decompression circuit has a frame memory or the like for signal processing, accumulates YC signals from the image processing system for each frame in the frame memory, and reads out signals accumulated from each block among a plurality of blocks. Compress and encode. The compression encoding is performed by, for example, performing two-dimensional orthogonal transformation, normalization, and Huffman encoding on the image signal for each block.

  The reproduction processing circuit 134 performs matrix conversion on the luminance signal Y and the color difference signals RY and BY, for example, into RGB signals. The signal converted by the reproduction processing circuit 134 is output to the display unit 107 and displayed (reproduced) as a visible image. The reproduction processing circuit 134 and the display unit 107 may be connected via wireless communication such as Bluetooth (registered trademark), and when configured in this way, an image captured by this camera is monitored from a remote location. be able to.

  The control system is a processing system that controls driving in the imaging system, the image processing system, and the recording / reproducing system in accordance with the operation of various switches provided in the D-SLR. The operation detection circuit 136 detects the operation of the main switch 119, the release button 120, etc. (other switches are not shown), and outputs the detection result to the camera system control circuit 135. The camera system control circuit 135 receives the detection signal from the operation detection circuit 136 and performs an operation according to the detection result. In addition, the camera system control circuit 135 generates a timing signal for performing an imaging operation and outputs the timing signal to the imaging device drive circuit 137.

  The imaging device driving circuit 137 receives a control signal from the camera system control circuit 135 and generates a driving signal for driving the solid-state imaging device 15. The information display circuit 142 receives a control signal from the camera system control circuit 135 and controls driving of the information display unit 180 in the optical viewfinder.

  For example, when the release button 120 is fully pressed, the camera system control circuit 135 controls driving of the solid-state imaging device 15, operation of the RGB image processing circuit 131, compression processing of the recording processing circuit 133, and the like. Further, by controlling the driving of the information display unit 180 in the optical finder via the information display circuit 142, the display in the optical finder (display segment state) is changed.

  Next, the focus adjustment operation of the photographic optical system 103 will be described. The camera system control circuit 135 is connected to the AF control circuit 140. Further, by attaching the lens device 102 to the camera body 100, the camera system control circuit 135 is connected to the lens system control circuit 141 in the lens device 102 via the mount contacts 101a and 102a. The AF control circuit 140, the lens system control circuit 141, and the camera system control circuit 135 communicate with each other data necessary for specific processing.

  The focus detection unit 121 outputs a detection signal in a focus detection area provided at a predetermined position in the shooting screen to the AF control circuit 140. The AF control circuit 140 generates a focus detection signal based on the output signal from the focus detection unit 121, and detects the focus adjustment state (defocus amount) of the photographing optical system 103. Then, the AF control circuit 140 converts the detected defocus amount into a drive amount of a focus lens, which is a part of the photographing optical system 103, and sends information related to the focus lens drive amount via the camera system control circuit 135. To the lens system control circuit 141.

  Here, when the focus adjustment is performed on the moving object, the AF control circuit 140 takes into account the time lag from when the release button 120 is fully pressed until the actual imaging control is started. Predict an appropriate stop position. Then, information regarding the driving amount of the focus lens to the predicted stop position is transmitted to the lens system control circuit 141.

  On the other hand, when the camera system control circuit 135 determines that the brightness of the object is low and sufficient focus detection accuracy cannot be obtained based on the output signal of the solid-state imaging device 15, the flash light emitting unit 114 is driven to select the object. Illuminate. You may make it illuminate an object not with the flash light emission unit 114 but with the white LED and fluorescent tube which are not shown in D-SLR.

  When the lens system control circuit 141 receives information on the driving amount of the focus lens from the camera system control circuit 135, the lens system control circuit 141 controls the driving of the AF motor 147 disposed in the lens device 101. As a result, the focus lens is moved in the direction of the optical axis L1 by the drive amount via a drive mechanism (not shown), and the photographing optical system 103 is brought into focus. When the focus lens is composed of a liquid lens or the like, the interface shape is changed.

  When the lens system control circuit 141 receives information on the exposure value (aperture value) from the camera system control circuit 135, the lens system control circuit 141 controls the driving of the aperture drive actuator 143 in the lens device 102. Thereby, the diaphragm 104 is operated so as to have a diaphragm aperture diameter corresponding to the diaphragm value.

  The shutter control circuit 145 controls the front curtain drive source 35, the charge source 36, and the rear curtain drive source 37. The front curtain drive source 35 is configured by an electromagnetic actuator configured by a known coil, yoke, or the like, a drive lever, or the like. The charge source 36 is configured by a drive lever, a spring, and the like for performing the closing operation in order to return the front curtain 21 that has performed the opening operation to the closed state shown in FIG. The rear curtain drive source 37 is composed of an electromagnetic actuator, a drive lever, and the like that are configured by known coils, yokes, and the like for opening and closing the rear curtain 22. When the information on the shutter speed from the camera system control circuit 135 is received, the driving of the front curtain drive source 35, the rear curtain drive source 37, and the charge drive source 36 is controlled. As a result, the front curtain 21 and the rear curtain 22 of the focal plane shutter 50 are operated so as to achieve the shutter speed. By the operation of the focal plane shutter 50 and the diaphragm 104, an appropriate amount of object light can be directed to the image plane side.

  When the AF control circuit 140 detects that the object is in focus, this information is transmitted to the camera system control circuit 135. At this time, if the release button 120 is fully pressed, the photographing operation is performed by the imaging system, the image processing system, and the recording / reproducing system as described above.

Next, the effect of the SiO ₂ fine particle deposition layer 11a formed on the surface of the optical element 11 of the present embodiment will be described with reference to FIG. 4 (a) is a state in which the contact angle was measured with the substrate provided with the SiO ₂ deposited film having a thickness of about 90nm on the outermost surface by vacuum deposition the surface without ablation treatment and distilled water It is shown. On the other hand, FIG. 4B shows a contact angle between distilled water and a substrate provided with an SiO ₂ fine particle deposition layer (hereinafter abbreviated as “deposition layer 11a”) having a thickness of about 1 nm on the outermost surface by ablation processing. It shows the state when measuring.

The contact angle was measured using a fully automatic contact angle meter Model CA-W manufactured by Kyowa Interface Science Co., Ltd. The contact angle was measured by a static method, and the value 20 seconds after dropping the droplet was taken as the measured contact angle. The contact angle was measured several times for each substrate, and the average value was determined. The average contact angle was 48.9 degrees (deviation was 1.V) for the substrate with the SiO ₂ vapor deposition film on the outermost surface by vacuum deposition. 0 degree). On the other hand, the contact angle average was 66.2 degrees (deviation was 1.1 degrees) for the substrate provided with the deposited layer 11a on the outermost surface by ablation.

The ablation process for forming the deposition layer 11a on the substrate is as follows. For example, as disclosed in Patent Document 3, target fine particles (miniaturized particles) emitted by irradiating a target (SiO _{2 in the} present embodiment) prepared in a vacuum vessel with pulsed laser light (ultraviolet laser). Is deposited on the substrate.

The target used was a SiO ₂ target manufactured by Kojundo Chemical Laboratory Co., Ltd., the wavelength of the pulse laser was 266 nm, the output was 50 mJ / pulse, the inside of the vacuum vessel was helium gas atmosphere, and the pressure was 0.05 Pa. .

  In general, when the contact angle between a liquid and a solid is θ, the following equation (1) is established (from “Basic Properties of Powder” edited by the Powder Engineering Society).

In equation (1), Δγ _L is the amount of change in the surface energy of the liquid (mJ / m ² ), and γ _C is the critical surface tension (mJ / m ² ) of the solid. Assuming that θ is smaller than 90 degrees and Δγ _L is constant from equation (1), the contact angle θ increases as the critical surface tension γ _{C of the} solid decreases. In other words, as the surface energy of the solid decreases, the contact angle θ of the liquid (here, distilled water) increases. Therefore, when FIG. 4A is compared with FIG. 4B, it can be said that the surface energy of the ablated substrate that has a large contact angle as shown in FIG. 4B is smaller.

  FIG. 4C is an enlarged view of A in FIG. 2 and shows a state where the dust 30 is attached to the surface of the optical element 11. As will be described later, a liquid bridge is formed between the dust 30 and the surface of the optical element 11. As shown in the present embodiment, the liquid bridge (indicated by a solid line in FIG. 4C) formed when the deposited layer 11 a is present on the surface of the optical element 11 is shown as 70. Further, the liquid bridge formed when there is no deposition layer 11a on the surface of the optical element 11 (indicated by a broken line in FIG. 4C) is shown as 70 '. This is based on the results shown in FIGS. 4 (a) and 4 (b). That is, the contact angle θ is different depending on whether or not the deposited layer 11a is present on the surface of the optical element 11, and θ1 and θ2 respectively (θ1 <θ2, see FIG. 4C).

When the dust 30 adheres to the surface of the optical element 11, water molecules (not shown) contained in the air aggregate between the dust 30 and the surface of the optical element 11 to form the liquid bridge 70. This liquid bridge 70, that liquid bridge force between the surface of the dust 30 and the optical element 11, the adhesive force F _L represented by the following formula (2) is applied ( "intermolecular force and surface force" J · By N. Israel Ativiri).

In equation (2), γ _sv is the surface energy (mJ / m ² ) of the substrate (optical element 11 in the present embodiment), and R is the radius (m) of the dust 30. Here, when considering the liquid bridging force with respect to the dust 30 having the same radius, the radius R of the dust 30 is constant. Therefore, the smaller the surface energy γ _{sv of the} substrate to which the dust 30 is attached, the smaller the adhesion force _FL is. It can be said that it is small. This is because the liquid bridge 70 formed between the dust 30 and the surface of the deposited layer 11a and the liquid bridge 70 ′ formed between the dust 30 and the surface of the optical element 11 are compared with each other. When the layer 11a is not present (S2 in FIG. 4C), the liquid bridge 70 with the deposited layer 11a is smaller (S1 in FIG. 4C) than the liquid bridge 70 ′. Trip liquid bridge 70 is small also small adhesive force F _L.

Further, as described above, since the surface energy γ _{sv of the} substrate (optical element 11) varies depending on the presence or absence of the deposited layer 11a, the surface energy γ _sv1 when the deposited layer 11a is present and the adhesion force when the deposited layer 11a is absent. When γ _sv2 is compared, γ _sv1 <γ _{sv2 holds} . Therefore, the adhesive force F _L1 when deposited layer 11a is present, the deposition layer 11a is compared with the adhesion force F _L2 in the absence, consisting of the formulas (2) and F _L1 <F _L2.

Apart from this, van der Waals force, which is an interaction force, acts between the dust 30 and the surface of the optical element 11. The Van der Waals force is an adhesion force F _V represented by the following equation (3).

  In Expression (3), A is the Hamarker constant (J) of the dust 30, D is the diameter (m) of the dust 30, and Z is a separation distance between the dust 30 and the surface of the optical element 11 of 0.4 nm. Here, the Hamarker constant has a proportional relationship with the surface energy γ of the substrate as shown in the following formula (4) (from “Intermolecular force and surface force” by J. N. Israel Ativiri).

  Here, when van der Waals force with respect to the same dust 30 is considered, the diameter D of the dust 30 and the separation distance Z between the dust 30 and the surface of the optical element 11 are constant. Therefore, the surface energy γ of the optical element 11 differs depending on whether or not the deposition layer 11 a is present on the surface of the optical element 11.

As described above, when the surface energy γ _{sv1 in the} presence of the deposited layer 11a and the adhesive force γ _sv2 in the absence of the deposited layer 11a are compared, γ _sv1 <γ _sv2 . Therefore, when the Hamarker constant A ₁ when the deposited layer 11 a is present is compared with the Hamarker constant A ₂ when the deposited layer 11 a is absent from the formula (4), the following formula (5) is established.
A ₁ <A ₂ (5)

From the inequalities (5) and (3), when the van der Waals force adhesion F _V1 with the deposited layer 11a and the adhesion force F _V2 without the deposited layer 11a are compared, F _V1 <F _V2 Become. That is, the deposit layer 11a can reduce the liquid bridging force and van der Waals force, which are the adhesion force of the dust 30 to the deposit layer 11a (optical element 11). As a result, even if the dust 30 tries to adhere to the optical element 11, if the deposited layer 11 a is present, the adhesion force is small, so that the dust 30 falls from the surface of the optical element 11 due to the influence of gravity applied to the dust 30, and It becomes difficult to adhere to the surface.

FIG. 5 is a TEM observation image of the deposited layer 11a. FIG. 5 shows a substantially central cross section of the Si substrate ablated on the Si substrate under the above-described conditions so that the structure of the deposited layer 11a can be observed. As shown in FIG. 5, it can be seen that a SiO ₂ film having a thickness of about 3 nm is formed on the Si substrate. It can also be seen that the height of the irregularities formed on the surface is about 0.5 nm. Usually, since a natural oxide film of about 1 to 2 nm is formed on the Si substrate, it was found that the thickness of the deposited layer 11a by the ablation process is about 1 nm.

  Hereinafter, the result of confirming the effect of reducing the adhesion force of the dust 30 to the optical element 11 by the deposited layer 11a will be shown. FIG. 6 is a diagram illustrating a schematic configuration of a jig that has been confirmed to have an adhesive force reduction effect. In the figure, reference numeral 31 denotes an electrode member which is moved in the X direction in the figure from the position 31x to the position 31y at a predetermined speed by a drive source (not shown).

  In addition, as shown in FIG. 7, electrodes 31 a to 31 e are provided on the electrode member 31 on the side facing the optical element 11. The electrodes 31a, 31c, and 31e are joined at a not-shown portion to have the same potential, and the electrodes 31b and 31d are also joined at the not-shown portion to have the same potential, and the electrodes 31a, 31c, 31e and the electrode 31b, A voltage is applied between 31d so that a predetermined potential difference is generated. Thereby, a gradient force is generated between the electrodes 31a, 31c, 31e and the electrodes 31b, 31d.

  The principle of generating this gradient force will be described below. As shown in FIG. 8A, consider a case where (1) positively charged particles, (2) negatively charged particles, and (3) uncharged particles are inserted between opposing planar electrodes. .

  When three types of particles are inserted into the uniform electric field, (1) positively charged particles move to the negative electrode with Coulomb force, (2) negatively charged particles move to the positive electrode with Coulomb force, and (3) uncharged particles are internalized by polarization. Electric charges are generated, but they do not move because the Coulomb forces are balanced.

  Next, when the particle of (3) is moved to the unequal electric field portion at the lower end of the electrode, an upward component force is generated in the Coulomb force according to the bending of the electric field lines. This component force is the gradient force. The charged particles of (1) and (2) also generate a gradient force due to polarization, and the acting force is the resultant force of the Coulomb force and the gradient force.

  The above contents are considered with a pair of electrodes arranged in a plane as shown in FIGS. Comparing an electrode with a uniform electrode spacing (gap length) (FIG. 8B) and a non-uniform electrode (FIG. 8C), the latter generates an unequal electric field in the plane direction. That is, since the non-uniformity of the electric field can be increased, the gradient force acts not only in the planar direction of the electrode but also in the thickness direction of the electrode.

  Here, as shown in FIG. 8D, by applying a direct current to the electrode member 31, (1) positively charged particles are applied to the negative electrode by Coulomb force, and (2) negatively charged particles are applied to the positive electrode by Coulomb force. 3) Uncharged particles can be attracted to the middle of both poles by a gradient force. That is, both effects of electrostatic attraction and gradient force attraction can be obtained.

  That is, not only a vertical force, which is a Coulomb force, acts on the dust 30 attached to the surface of the optical element 11 facing the electrode member 31, but also a shear force due to a gradient force acts. Therefore, it can be removed from the surface of the optical element 11 even if the dust 30 is charged or not.

  In FIG. 9, the removal result of the dust 30 using the jig | tool shown in FIG. 6 using this gradient force is shown. As shown in FIG. 9, the optical element 11 having the deposited layer 11a (expressed as an ablation substrate in FIG. 9) has a contact angle compared to the optical element 11 without the deposited layer 11a (expressed as a solid substrate in FIG. 9). It can be seen that the removal rate of the dust 30 is high.

  This confirms that the surface energy of the optical element 11 decreases due to the presence of the deposited layer 11a, and accordingly, the removal rate of the dust 30 attached to the surface of the optical element 11 is improved. That is, the presence of the deposited layer 11a not only suppresses the adhesion of dust to the surface of the optical element 11, but also facilitates the removal of the adhered dust.

  According to the above configuration, foreign matter such as dust can be prevented from adhering to the surface of the optical element 11 without causing an adverse optical effect.

(Other embodiments)
In the above embodiment, the SiO ₂ fine particle deposition layer 11a is provided on the surface of the optical element 11, but the optical element 11 is not provided between the focal plane shutter 50 and the solid-state imaging device 15 as shown in FIG. In this case, that is, when the focal plane shutter 50 and the solid-state imaging device 15 face each other, dust adhering to the surface of the solid-state imaging device 15 becomes a problem.

Even in this case, as shown in FIG. 10, it is preferable to provide the SiO ₂ fine particle deposition layer 80 on the surface of the cover member 15a of the solid-state imaging device 15 by the laser ablation method. As a result, an effect equivalent to that of the above-described embodiment can be obtained, so that it is possible to suppress dust from adhering to the surface of the solid-state imaging device 15 without adversely affecting optically.

It is the schematic which shows the system configuration | structure of the digital single-lens reflex camera which concerns on embodiment. It is a side sectional view for explaining a schematic configuration of an imaging unit and a focal plane shutter of the digital single-lens reflex camera according to the embodiment. It is a block diagram which shows the electric constitution of the digital single-lens reflex camera which concerns on embodiment. (A), (b) is a figure which shows the photograph which measured the contact angle of the surface of an optical element, (c) is an enlarged view of A in FIG. It is a figure which shows the TEM observation image of the surface of an optical element. It is a figure which shows schematic structure of the jig | tool which confirmed the adhesive force fall effect. It is a top view of the electrode member which comprises the jig | tool shown in FIG. It is a figure for demonstrating gradient power. It is a figure which shows the measurement result which confirmed the effect of the deposit layer using the jig | tool shown in FIG. It is a sectional side view for demonstrating schematic structure of the imaging part and focal plane shutter of the digital single-lens reflex camera which concern on other embodiment.

Explanation of symbols

10: imaging unit 11: optical elements 11a, 80: SiO ₂ particle deposition layer 15: a solid-state imaging device 15a: cover member 15b: image pickup device 15c: connection terminal 30: dust 50: focal plane shutter

Claims (7)

An optical device manufacturing method comprising: an imaging unit that converts an optical image of a subject into an electrical signal; and an optical element disposed on a front surface of the imaging unit,
A method of manufacturing an optical device, comprising: forming a fine particle deposition layer on a subject side surface of the optical element by a laser ablation method. A method of manufacturing an optical apparatus including an imaging unit that converts an optical image of a subject into an electrical signal,
The method of manufacturing an optical apparatus, wherein the imaging unit includes an imaging element and a cover member of the imaging element, and a fine particle deposition layer is formed on a subject side surface of the cover member by a laser ablation method. The method for manufacturing an optical device according to claim 1, wherein the fine particle deposition layer is a SiO ₂ fine particle deposition layer. Used in an optical device having an imaging means for converting an optical image of a subject into an electrical signal,
An optical element which is disposed on the subject side with respect to the image pickup means and has a fine particle deposition layer formed on the surface of the subject side by a laser ablation method. The optical element according to claim 4, wherein the fine particle accumulation layer is a SiO ₂ fine particle accumulation layer. Used in an optical device having an imaging means for converting an optical image of a subject into an electrical signal,
The cover member of the image pickup means, wherein the image pickup element constituting the image pickup means is disposed on the subject side, and a fine particle deposition layer is formed on the surface of the subject side by a laser ablation method. . The cover member according to claim 6, wherein the particulate deposition layer is a SiO ₂ particulate deposition layer.

Images