JP5228409B2 - Optical low-pass filter and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical low-pass filter and a manufacturing method thereof.

  The optical low-pass filter cuts a high-frequency component of the video frequency of light in order to suppress a pseudo signal generated when the image sensor receives light, and its characteristic is determined by a separation pattern for separating light and is a piezoelectric material. A quartz substrate is used. Here, it is known that the characteristics (for example, the separation width of the incident light separation pattern) change in the quartz substrate depending on the thickness dimension thereof. Specifically, when the thickness of the quartz substrate is reduced, the separation width of the separation pattern is reduced.

  Therefore, conventionally, a polishing apparatus as shown in Patent Document 1 has been used to make the quartz substrate have a predetermined thickness.

  In the polishing apparatus described in Patent Document 1, a quartz substrate as a workpiece is interposed between an upper board and a lower board, and an upper board and a lower board are supplied while supplying a polishing liquid between the upper board and the lower board. Is moved relative to each other to polish the quartz substrate.

  Specifically, as shown in FIG. 3, the polishing apparatus 4 described in Patent Document 1 includes upper and lower boards (upper board 42 and lower board 43) having a main shaft 41 penetrating in the center, and the upper board 42. Four carriers 44 sandwiched between the lower plate 43 are provided. A sun gear 45 is fitted on the main shaft 41, and an internal gear 46 is provided outside the carrier 44. The carrier 44 has four holding holes 47 for accommodating a quartz crystal substrate as a workpiece. The carrier 44 performs planetary motion by rotationally driving the sun gear 45 and the internal gear 46. That is, the carrier 44 is configured to revolve around the main shaft 41.

The polishing liquid is a mixture of abrasive grains in the liquid. The polishing liquid is driven into the apparatus through the through-hole 48 provided in the upper plate 42 and the carrier 44 is driven by driving the polishing apparatus 4. Make a planetary movement. Thereby, with relative movement between the quartz substrate and each board (the upper board 42 and the lower board 43), abrasive grains in the polishing liquid taken in between the upper board 42 and the lower board 43 act. Both main surfaces of the quartz substrate are polished (polishing step).
JP-A-9-155726

  Incidentally, in electronic devices such as camcorders equipped with an optical low-pass filter, downsizing and high precision of image pickup devices are currently being achieved. For this reason, with the miniaturization of these image sensors and the high precision of the image sensors, the optical low-pass filter used for the image sensor is similarly affected, and it is required to reduce the separation width of the optical low-pass filter.

  Therefore, when an optical low-pass filter having a plurality of quartz substrates bonded via an adhesive is used, the thickness of the quartz substrate is related to the separation width as described above. By reducing the thickness, the separation width can be reduced.

  However, when adjusting the thickness of the quartz substrate using the polishing apparatus as shown in Patent Document 1 described above, there is a concern that the frequency of breakage and cracking increases when the thickness of the quartz substrate is reduced.

  Also, when processing such an optical low-pass filter, conventionally, the size of the quartz substrate is formed to the main surface size of the optical low-pass filter before the polishing step, and then a plurality of optical low-pass filters are bonded together to obtain desired optical characteristics. (For example, incident light separation patterns and separation widths) have been obtained. However, polishing is performed on each quartz substrate molded to the main surface size of the optical low-pass filter, the optical separation direction is recognized, and bonding is performed after the adhesive is applied. Manufacturing cost is high and this is not a preferable manufacturing process. Therefore, in recent years, a plurality of quartz substrates are bonded to each other after the polishing process, and a plurality of optical substrates are cut from a single wafer having desired optical characteristics (for example, incident light separation pattern and separation width). A so-called multi-chip method for manufacturing a low-pass filter has been implemented.

  However, when such a multi-cavity method is implemented, the optical low-pass filter uses an adhesive to bond a plurality of quartz substrates, but the main surface size of the quartz substrate is 20 mm × 20 mm or more, or this size When the distance is greater than or equal to the vicinity, the amount of the adhesive at each position on the bonding surface of each quartz substrate is different. Specifically, a plurality of quartz substrates are bonded together by bonding the principal surfaces of a plurality of quartz substrates, but the amount of adhesive in the outer peripheral region is larger than the central region of the quartz substrate. Become more. Specifically, the thickness of the adhesive in the central region of the main surface of the quartz substrate is 5 to 10 μm, and the thickness of the adhesive in the outer peripheral region of the main surface of the quartz substrate is 20 to 30 μm.

  This becomes a problem caused by applying pressure when bonding a plurality of quartz substrates, and the adhesive located in the central region of the main surface of the quartz substrate moves in the outer circumferential direction by the pressure during bonding, This is considered to be caused by the fact that the adhesive does not move in the outer peripheral region of the main surface of the quartz substrate where pressure is hardly applied.

  Therefore, in the outer peripheral area of each main surface of the quartz substrate, the amount of the adhesive originally disposed and the adhesive that has moved is excessive, and as a result, in the thin quartz substrate that cannot suppress the movement of the adhesive, Deforms to warp. This becomes more prominent as the size of the main surface of the quartz substrate is increased.

  Accordingly, in order to solve the above problems, the present invention eliminates damage and cracking of a quartz substrate during processing and handling in an optical low-pass filter for manufacturing a large number of optical low-pass filters from one wafer and a method for manufacturing the same. In addition, an object of the present invention is to provide an optical low-pass filter that eliminates warpage of the quartz substrate due to the adhesion of the quartz substrate and reduces the separation width of the optical low-pass filter, and a manufacturing method thereof.

In order to achieve the above object, an optical low-pass filter manufacturing method according to the present invention is a method of manufacturing an optical low-pass filter that manufactures a large number of optical low-pass filters from one wafer. Forming a single wafer and forming a plurality of optical low-pass filters by cutting the wafer to form a single wafer. In the forming step, a plurality of quartz substrates having opposite optical axis directions and different thicknesses are used as a substrate group, and one or more substrate groups are formed . It is thicker than the quartz substrate .

According to the present invention, in an optical low-pass filter for manufacturing a large number of optical low-pass filters from one wafer and a method for manufacturing the same, the crystal substrate is prevented from being damaged or cracked during processing or handling and the crystal substrate is bonded to the crystal substrate. And the separation width of the optical low-pass filter can be reduced. That is, according to the present invention, even when a wafer is formed using a quartz substrate having a size capable of obtaining a large number of optical low-pass filters, the quartz substrate is prevented from being damaged or cracked during processing or handling. It is possible to eliminate warping of the quartz substrate due to adhesion. In addition, since each of the substrate groups has a plurality of quartz substrates having opposite optical axis directions and different thicknesses, the separation width of the incident light separation pattern can be canceled to narrow the separation width. As a result, the separation width of the incident light separation pattern can be arbitrarily set. Therefore, even if the setting is made to reduce the separation width in accordance with the downsizing and high precision of the image sensor, it is possible to cope with the optical low-pass filter without making the quartz substrate thin. In addition, by manufacturing a large number of optical low-pass filters from one wafer, the optical low-pass filter can be manufactured at low cost without manufacturing time and manufacturing cost. Further, since the quartz substrate of the outermost layer is thicker than the quartz substrate inside thereof, it is suitable for eliminating the warp of the quartz substrate.

  In the method, in the forming step, a plurality of quartz substrates whose main surface size is set to 20 mm × 20 mm or more are used, and in the forming step, a plurality of optical low-passes whose main surface size is set to 10 mm × 10 mm or less. A filter may be molded.

  In this case, it becomes possible to manufacture an optical low-pass filter corresponding to downsizing and high precision of the image sensor without damage, cracking or warping of the quartz substrate.

  In order to achieve the above object, an optical low-pass filter according to the present invention is manufactured by the above-described method for manufacturing an optical low-pass filter according to the present invention.

  According to the present invention, since the optical low-pass filter according to the present invention is manufactured by the above-described method for manufacturing an optical low-pass filter, the optical low-pass filter for manufacturing a large number of optical low-pass filters from one wafer and the manufacturing method thereof are It is possible to eliminate breakage and cracking of the quartz substrate at the same time, to eliminate warpage of the quartz substrate due to adhesion of the quartz substrate, and to reduce the separation width of the optical low-pass filter. In addition, a cheaper optical low-pass filter can be obtained.

  According to the present invention, in an optical low-pass filter for manufacturing a large number of optical low-pass filters from one wafer and a method for manufacturing the same, the crystal substrate is prevented from being damaged or cracked during processing or handling and the crystal substrate is bonded to the crystal substrate. And the separation width of the optical low-pass filter can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the case where the present invention is applied to a quartz substrate formed by cutting, for example, 44.8 degrees with respect to the optical axis of the quartz ingot as a quartz substrate is shown. The cutting angle with respect to the optical axis of the crystal ingot can be arbitrarily set.

  The optical low-pass filter according to the present embodiment has a configuration in which five crystal substrates 11, 12, 13, 14, and 15 as shown in FIGS. In this embodiment, an adhesive that is a UV curable material is used as the adhesive 2.

  Of the arrows shown in FIG. 1, the arrows on the side surfaces of the quartz substrates 11, 12, 14, 15 indicate the optical axes of the quartz substrates 11, 12, 14, 15. The inclination of the optical axis 15 is based on the cutting angle of the quartz ingot when it is cut from the quartz ingot. Further, among the arrows shown in FIG. 1, the arrows shown on the principal surfaces 111, 121, 141, 151 on the quartz substrates 11, 12, 14, 15 indicate the separation directions on the quartz substrates 11, 12, 14, 15.

  Of the five quartz substrates 11 to 15, the quartz substrates 11 and 12 are quartz birefringent plates. By superposing these quartz substrates 11 and 12, the 0 ° birefringent plate group 16 (the substrate group referred to in the present invention). Is configured. In the 0 ° birefringent plate group 16, incident light is separated in the horizontal direction.

  Specifically, the quartz substrate 11 is a substrate that separates incident light in a 0 ° direction with respect to the horizontal direction, and the thickness thereof is set to 0.5 mm. The quartz substrate 12 is a substrate that separates incident light in a direction of 180 ° with respect to the horizontal direction, and is a substrate that separates light in a symmetric direction (reverse direction) with respect to the quartz substrate 11, and has a thickness of 0.4 mm. Is set to According to the 0 ° birefringent plate group 16, the horizontal separation width can be reduced by canceling the separation direction of the horizontal separation pattern of the incident light.

  Of the five quartz substrates 11 to 15, the quartz substrates 14 and 15 are quartz birefringent plates, and the 90 ° birefringent plate group 17 (substrate group referred to in the present invention) is formed by superimposing these quartz substrates 14 and 15. Is configured. In the 90 ° birefringent plate group 17, incident light is separated in the vertical direction.

  Specifically, the quartz substrate 14 is a substrate that separates incident light in a 90 ° direction with respect to the horizontal direction, and its thickness is set to 0.4 mm. The quartz substrate 15 is a substrate that separates incident light in a 270 ° direction with respect to the horizontal direction, and is a substrate that separates light in a symmetric direction (reverse direction) with respect to the quartz substrate 14, and has a thickness of 0.5 mm. Is set to According to the 90 ° birefringent plate group 17, it is possible to cancel the separation direction of the vertical separation pattern of the incident light and to narrow the vertical separation width.

  Of the five quartz substrates 11 to 15, the quartz substrate 13 is a depolarizing plate, which eliminates the polarization state of the linearly polarized light that passes through the 0 ° birefringent plate group 16 and has a thickness of 0. .4mm is set.

  As for the five quartz substrates 11 to 15 having the above-described configuration, as shown in FIGS. 1 and 2, the quartz substrate 12 is bonded to the quartz substrate 11 to form the 0 ° birefringent plate group 16. The quartz substrate 15 is bonded to form a 90 ° birefringent plate group 17, the quartz substrate 13 is bonded to the quartz substrate 12, the quartz substrate 14 is bonded to the quartz substrate 13, and the 0 ° birefringent plate group 16 and the polarized light are polarized. The canceling plate (quartz substrate 13) and the 90 ° birefringent plate group 17 are laminated.

  In the optical low-pass filter of this embodiment, as shown in FIGS. 1 and 2, an antireflection film 3 (AR coating) is additionally formed on the incident surface 18 outside the quartz substrate 11, and is outside the quartz substrate 15. An antireflection film 3 (AR coating) is additionally formed on the emission surface 19. In the present embodiment, the antireflection film 3 is formed on the incident surface 18 of the quartz substrate 11 and the exit surface 19 of the quartz substrate 15, but the present invention is not limited to this. A film for use in the above may be formed.

  Next, the manufacturing process of this optical low-pass filter will be described in detail below.

  A quartz ingot (not shown) is cut at 44.8 degrees with respect to its optical axis to form quartz substrates 11 to 15 whose principal surfaces are not polished. The main surface size of the quartz substrates 11 to 15 is set to 20 mm × 20 mm or more, and in this embodiment, the main surface size of the quartz substrates 11 to 15 is set to 40 × 30 mm.

  Both the main surfaces 111, 121, 131, 141, 151 of the quartz substrates 11-15 are polished by using the polishing apparatus 4 described above so that these quartz substrates 11-15 have the desired thicknesses. In this embodiment, the thickness of the quartz substrate 11 is set to 0.5 mm, the thickness of the quartz substrate 12 is set to 0.4 mm, the thickness of the quartz substrate 13 is set to 0.4 mm, and the thickness of the quartz substrate 14 is set. The thickness is set to 0.4 mm, and the thickness of the quartz substrate 15 is set to 0.5 mm.

  The quartz substrates 11 to 15 polished to the above-described desired thickness using the polishing apparatus 4 are laminated by laminating the main surfaces 111 to 151 at a time through the adhesive 2 in the arrangement shown in FIGS. Two wafers 1 are formed (formation process referred to in the present invention). The adhesive 2 used here is a UV curable material, and the thickness of the adhesive 2 after bonding the quartz substrates 11 to 15 is set to fall within a range of 5 to 10 μm.

  Further, the formation process will be described in more detail. Two substrate groups (0 ° birefringent plate groups 16, 0) having two quartz substrates 11, 12 (and 14, 15) having different optical thickness directions and different thicknesses. A 90 ° birefringent plate group 17) is laminated. Specifically, the quartz substrate 11 that separates the incident light in the direction of 0 ° with respect to the horizontal direction and the quartz substrate 12 that separates the incident light in the direction of 180 ° with respect to the horizontal direction via the adhesive 2 are provided. The 0 ° birefringent plate group 16 is formed by bonding. In addition, a quartz substrate 15 that separates incident light in a 270 ° direction with respect to the horizontal direction is bonded to the quartz substrate 14 that separates incident light in a direction of 90 ° with respect to the horizontal direction via the adhesive 2. 90 ° birefringent plate group 17 is formed. Then, the 0 ° birefringence plate group 16, the depolarization plate (quartz substrate 13), and the 90 ° birefringence plate group 17 are bonded via the adhesive 2. Here, only the bonding state of the quartz substrates 11 to 15 is described, and all the quartz substrates 11 to 15 are bonded through the adhesive 2 at a time.

  Further, from the thickness of the quartz substrates 11 to 15 described above, as shown in FIGS. 1 and 2, the outermost quartz substrate 11 (15) of the wafer 1 is thicker than the inner quartz substrate 12 (14). That is, the outermost quartz substrate 11 (15) of the manufactured optical low-pass filter is thicker than the inner quartz substrate 12 (14).

  Then, after the above-described forming process, the wafer 1 composed of the laminated quartz substrates 11 to 15 is divided into nine rectangular optical low-pass filters by a dicing saw as a cutting device (the division shown in FIG. 2). Nine optical low-pass filters are formed from one wafer 1 (see the step 5 in the present invention). The main surface size of the optical low-pass filter molded in this molding process is set to 10 mm × 10 mm or less, and in this embodiment, it is 8 mm × 9 mm.

  The light incident on the optical low-pass filter formed by the forming process is separated into an ordinary ray and an extraordinary ray by the 0 ° birefringent plate group 16, and the separated ordinary ray and extraordinary ray are respectively 90 ° birefringent plates. The group 17 is separated into four points (square vertices (corner portions)).

  As described above, the optical low-pass filter according to the present embodiment and the method for manufacturing the optical low-pass filter use five crystal substrates 11 to 15 whose main surface size is set to 20 mm × 20 mm or more. The main surfaces 111 to 151 are bonded and laminated through the adhesive 2 to form one wafer 1, and nine optical low-pass filters are formed from one wafer 1. In the formation of one wafer 1, two substrate groups (0 ° birefringent plate group 16) composed of two quartz substrates 11, 12 (and 14, 15) having opposite optical axis directions and different thicknesses are used. , 90 ° birefringent plate group 17). Therefore, according to the present embodiment, the quartz substrates 11 to 15 are not damaged or cracked during processing or handling, the quartz substrates 11 to 15 are not warped by the adhesion of the quartz substrates 11 to 15, and the optical low-pass filter is used. The separation width can be reduced.

  That is, according to the present embodiment, even if the wafer 1 is formed using the quartz substrates 11 to 15 having a size capable of obtaining a large number of optical low-pass filters, the quartz substrates 11 to 15 are damaged during processing or handling. Further, it is possible to eliminate cracks of the quartz substrates 11 to 15 due to adhesion of the quartz substrates 11 to 15 as well as to eliminate cracks. Further, in the 0 ° birefringent plate group 16 and the 90 ° birefringent plate group 17, the two crystal substrates 11 and 12 (14, 15) having different optical thicknesses and different thicknesses are respectively configured. The separation direction of the incident light separation pattern can be offset to narrow the separation width. As a result, the separation width of the incident light separation pattern can be arbitrarily set. Therefore, even if the setting is such that the separation width is narrowed as the image pickup device is miniaturized and made highly precise, it is possible to cope without reducing the quartz substrates 11 to 15 of the optical low-pass filter.

  In addition, since nine optical low-pass filters whose main surface size is set to 10 mm x 10 mm or less are molded, the optical low-pass filter corresponding to the downsizing and high precision of the image sensor is damaged, cracked or warped of the quartz substrate. It can be manufactured without.

  Further, the quartz substrates 11 to 15 are laminated, and the quartz substrate 11 (15) of the outermost layer is set to be thicker than the quartz substrate 12 (14) on the inner side thereof. It is suitable for eliminating warpage.

  In this embodiment, nine optical low-pass filters are manufactured from one wafer 1. However, the present invention is not limited to this, and a plurality of optical low-pass filters can be manufactured from one wafer. The number of manufactured optical low-pass filters may be set arbitrarily.

  In this embodiment, the light is separated at four points by the optical low-pass filter. However, the present invention is not limited to this. For example, the 0 ° birefringence plate group 16 may be configured by superimposing two quartz substrates, and only an IR cut glass or the like may be bonded. In the 0 ° birefringent plate group 16, incident light is separated into only two points in the horizontal direction.

  In this embodiment, the light is separated on the four vertexes of the square shape by the optical low-pass filter. However, the present invention is not limited to this, and the light may be separated on the four vertexes of the rhombus shape. Alternatively, it may be separated on the vertices of four points of a parallelogram shape or a rectangular shape.

  In this embodiment, an optical low-pass filter is constituted by the 0 ° birefringent plate group 16, the depolarizing plate (quartz substrate 13), and the 90 ° birefringent plate group 17. However, the present invention is not limited to this. Alternatively, any substrate group may be used as long as the optical axis direction is the reverse direction, a plurality of quartz substrates having different thicknesses are used as the substrate group, and the plurality of substrate groups are stacked. For example, the optical low-pass filter may be composed of a 0 ° birefringent plate group, a 45 ° birefringent plate group, and a 135 ° birefringent plate group. The 45 ° birefringent plate group here is for separating incident light in the 45 ° direction with respect to the horizontal direction. Specifically, the incident light is directed in the 45 ° direction with respect to the horizontal direction. It consists of a substrate to be separated and a substrate that separates incident light in the direction of 225 ° with respect to the horizontal direction. The 135 ° birefringent plate group separates incident light in the 135 ° direction with respect to the horizontal direction, and specifically separates the incident light in the −45 ° direction with respect to the horizontal direction. It is comprised from the board | substrate and the board | substrate which isolate | separates the incident light in a 315 degree direction with respect to a horizontal direction.

  It should be noted that the present invention can be implemented in various other forms without departing from the spirit, gist, or main features. For this reason, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  The present invention can be applied to an optical low-pass filter using crystal.

FIG. 1 is a perspective view showing a schematic configuration of a quartz crystal substrate which is a constituent member of a wafer according to the present embodiment. FIG. 2 is a schematic side view of the wafer according to this example. FIG. 3 is a plan view showing a schematic configuration of the polishing apparatus.

Explanation of symbols

1 Wafer 11, 12, 13, 14, 15 Crystal substrate 111, 121, 131, 141, 151 Main surface 2 Adhesive

Claims (3)

In a manufacturing method of an optical low-pass filter for manufacturing a large number of optical low-pass filters from one wafer,
Using a plurality of quartz substrates, and forming a single wafer by laminating and laminating the principal surfaces of the plurality of quartz substrates via an adhesive; and
A molding step of cutting a single wafer to form a plurality of optical low-pass filters;
In the forming step, the optical axis direction is the reverse direction, and a plurality of quartz substrates having different thicknesses are used as a substrate group, and one or more substrate groups are formed, and the quartz substrate in the outermost layer is the inside of the quartz substrate. An optical low-pass filter manufacturing method characterized by being thicker than a quartz substrate . In the manufacturing method of the optical low-pass filter according to claim 1,
In the forming step, a plurality of crystal substrates whose main surface size is set to 20 mm × 20 mm or more are used,
In the forming step, a large number of optical low-pass filters whose main surface size is set to 10 mm × 10 mm or less are formed.   An optical low-pass filter manufactured by the method for manufacturing an optical low-pass filter according to claim 1.

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