Measurement unit, method for measurement, and method for composite prism

Abstract

To increase the accuracy of measuring the linear expansion coefficient of a glass plate.SOLUTION: A measurement unit 100 includes: a first stationary part 31 for measuring the linear expansion coefficient of a glass plate 1 having a linear expansion coefficient of 120×10-7 / K at a maximum or measuring its correlation value, the first stationary part being positioned in contact with the glass plate 1: and a second stationary part 32 equipped with a laser displacement meter 4 for measuring the thermal expansion of the glass plate 1. The first and second stationary parts 31, 32 are made of material with a linear expansion coefficient of 0.5×10-7 / K at a maximum.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a measuring instrument, a measuring method, and a method for manufacturing a composite prism.

Background Art

[0002] A general linear expansion coefficient measuring instrument heats a sample using a heater with the sample sandwiched between a probe and a pedestal, and determines the linear expansion coefficient of the sample based on detecting the displacement amount of the probe corresponding to the expansion of the sample due to heating. Also, regarding measurement at high temperatures, the linear expansion of a standard sample is measured simultaneously to improve the calculation accuracy of the linear expansion coefficient of the sample to be measured. The sample is often placed in a glass tube or the like so as not to be affected by the external environment. Representative samples include metals with a high linear expansion coefficient (for example, aluminum), resins, and rubbers. On the other hand, when the sample is glass, its linear expansion coefficient is about 1 / 3 of that of aluminum and about 1 / 10 to 1 / 100 of that of resin, and various problems arise regarding its accurate measurement.

[0003] Patent Document 1 discloses a method for measuring dimensions using a plurality of displacement sensors, and holding the displacement sensors in a holding member made of an invar material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to measure the linear expansion coefficient of a glass plate with higher precision, it may be required to take a larger temperature rise range of the glass plate. That is, considering the influence of measurement error, when the temperature rise range is narrow, sufficient measurement accuracy cannot be ensured. When heating the glass plate with such a large temperature rise range, naturally, heat is also conducted to the surrounding objects of the glass plate and they thermally expand. For example, in the case of Patent Document 1, since the displacement sensor is a contact type, there is a risk that the displacement sensor itself (for example, its contactor, etc.) thermally expands due to heat conduction from the glass plate.

[0006] As an addition or alternative to the above problems, even if the glass plates are made of the same material, they may have different linear expansion coefficients for each glass plate. In other words, even if glass plates of the same composition are purchased, the linear expansion coefficients may be different for each glass plate. For example, when cutting out glass pieces from a glass plate with a linear expansion coefficient that is not sufficiently small to assemble a composite prism (for example, a composite prism), in the manufacturing process of the composite prism (for example, the polishing process), each glass piece may expand to a different extent, making it difficult to ensure the desired shape and dimensional accuracy of the composite prism. For example, when forming a flat surface (for example, a reflective surface) by polishing in the range across adjacent prism pieces after joining the prism pieces cut out from the glass plate, the flat surface may not be successfully formed finally due to the difference in the amount of heat (degree of expansion) received by each prism piece. This phenomenon becomes more apparent as the linear expansion coefficient of the prism piece is larger.

[0007] One aspect of the present application relates to improving the measurement accuracy of the linear expansion coefficient of a glass plate, and as an addition or alternative, to providing a technology that contributes to improving the yield of the composite prism itself assembled from glass pieces cut out from a common glass plate.

Means for Solving the Problem

[0008] The measuring instrument according to one aspect of the present disclosure is 120×10 -7A measuring instrument for measuring the linear expansion coefficient of a glass plate having a linear expansion coefficient of / K or less or a correlation value thereof, including a first stationary part against which the glass plate abuts and is positioned, and a second stationary part on which a laser displacement meter for measuring the thermal expansion of the glass plate is mounted. Both the first and second stationary parts are made of a material having a linear expansion coefficient of 0.5×10 -7 / K or less. Specifically, a material having a linear expansion coefficient of 0.5×10 -7 / K or less is adopted for the first and second stationary parts. Furthermore, a laser displacement meter is adopted as the displacement meter to reduce the thermal connection between the glass plate and the displacement meter. This promotes more accurate measurement of the linear expansion coefficient of the glass plate. The first and second stationary parts can be different parts of the same component or different components. The linear expansion coefficient of the material of the first and second stationary parts can be measured at least in the temperature range of 25°C to 75°C. The linear expansion coefficient of the glass plate can be measured in the range of normal temperature to 350°C.

[0009] The measuring method according to another aspect of the present disclosure is a measuring method for measuring the linear expansion coefficient of a glass plate having a linear expansion coefficient of 120×10 -7 / K or less or a correlation value thereof, including abutting and positioning the glass plate against the first stationary part and operating a laser displacement meter mounted on the second stationary part. Both the first and second stationary parts are made of a material having a linear expansion coefficient of 0.5×10 -7 / K or less. The linear expansion coefficient of the material of the first and second stationary parts can be measured at least in the temperature range of 25°C to 75°C.

[0010] The measuring instrument can also include a temperature control device for heating or cooling the glass plate, and the glass plate is heated or cooled by this temperature control device. Preferably, the temperature control device is a surface heater that heats the entire main surface (for example, the lower surface) of the glass plate. Uniform heating within the plane of the glass plate becomes possible, and the measurement time can be shortened. The temperature control device can include a water cooling mechanism in addition to the surface heater, whereby the cooling time of the glass plate is shortened and the measurement cycle is shortened.

[0011] The measuring instrument can further include one or more (preferably a plurality of) non-contact thermometers for measuring the temperature of the glass plate. The measured temperature can also be oversampled using the non-contact thermometer.

[0012] The measured distance can be oversampled using a laser displacement meter. By oversampling and statistically processing the measured distance of the laser displacement meter, the influence of measurement error can be reduced, and it also becomes possible to use a laser displacement meter with lower accuracy. A high-resolution coefficient of linear expansion can also be obtained by obtaining an approximate line in the statistical processing. Typically, a computer performs statistical processing on the oversampling result of the measured distance of the laser displacement meter.

[0013] The measuring instrument can further include a displacement member that is displaceable with respect to the first stationary portion in response to the expansion of the glass plate and is made of a material having a coefficient of linear expansion of 0.5×10 -7 / K or less. The laser displacement meter measures the displacement of a predetermined surface of the displacement member for measuring the thermal expansion of the glass plate. More stable measurement is promoted by measuring the distance to the predetermined surface of the same displacement member rather than measuring the distance to the predetermined surface of separate glass plates.

[0014] The measuring instrument can further include biasing means for biasing the displacement member toward the glass plate in a state where the glass plate is sandwiched between the displacement member and the first stationary portion. The biasing means can include an elastic member such as a spring and / or magnetic portions with the same magnetic poles facing each other, but other configurations (for example, those utilizing gravity) can also be adopted. The adoption of the biasing means enhances the measurement efficiency. The glass plate can be BK7 glass. The laser displacement meter can be based on a phase difference detection method.

[0015] A method for manufacturing a composite prism according to another aspect of the present disclosure includes: (A) a step of selecting a glass plate using the above-described measuring instrument; (B) a step of joining two or more glass pieces cut from the glass plate determined to be a good product in the selection step; and (C) a step of polishing the surface of the composite prism to which two or more glass pieces are joined.

[0016] When polishing the surface of a composite prism in which two or more glass pieces are joined (for example, when performing CMP (Chemical Mechanical Polishing)), each of the two or more glass pieces can receive different amounts of heat and expand to different degrees. After the polishing process, each of the two or more glass pieces contracts, but due to the above-described expansion difference, the shape accuracy of the composite prism may decrease, and its yield may decrease. In the present disclosure, the glass plate is selected using the above-described measuring instrument. That is, two or more glass pieces are cut out from a glass plate confirmed to be a non-defective product having a low linear expansion coefficient, and these are joined and polished. Thereby, it is possible to avoid or suppress the manifestation of a decrease in the shape accuracy of the composite prism due to the thermal influence in the polishing process, and to avoid or suppress a decrease in its yield. When performing step (A) before step (B), it is easier to measure expansion or contraction than in the case where this is not done. Steps (B) and (C) can be carried out in this order or in the reverse order. Typically, steps (A) to (C) are carried out in the same factory.

[0017] When not performing step (A) prior to steps (B) and (C), after the surface of the composite prism over two or more glass pieces is polished, there is a possibility that a slight step may occur on the polished surface of the composite prism at the boundary between adjacent glass pieces. In this case, it is not possible to form an optical path as designed within the composite prism, the optical characteristics of the composite prism cannot be satisfactory, and its yield may decrease. In the present disclosure, as described above, by adopting step (A), it is possible to avoid or suppress the manifestation of a decrease in the shape accuracy of the composite prism due to the thermal influence in the polishing process, and to avoid or suppress a decrease in its yield. Additionally or alternatively, the inspection burden of the composite prism is reduced.

[0018] Typically, a composite prism guides a light beam incident through a lens to an image sensor and is incorporated into an image acquisition device (e.g., a camera module). The composite prism may be composed of one type of prism piece having the same structure, or may be composed of two or more types of prism pieces having different structures. In some cases, the composite prism is composed of a first prism piece cut out from a glass plate and a second prism piece obtained by additional processing (e.g., additional cutting) of the first prism piece.

[0019] The selection of the glass plate is performed based on the measurement result of the linear expansion of the glass plate. Typically, the linear expansion coefficient is calculated for each glass plate to be selected, but other methods can also be adopted. As an alternative to the linear expansion coefficient, a correlation value of the linear expansion coefficient (e.g., ΔD / ΔK in the embodiments described later) can also be adopted. Incidentally, the linear expansion coefficient is calculated by the following formula. Linear expansion coefficient = (ΔD / L) × (1 / ΔK) Here, L represents the length of the glass plate, ΔK represents the temperature change amount, ΔD represents the change amount of the length per ΔK.

[0020] Generally, the expansion of glass and ceramics is ignored and is actually extremely small compared to metals. However, when a composite prism is assembled from two or more glass pieces as described above, the heat distribution generated in those glass pieces may become non-uniform. Also, the linear expansion coefficients of glass and ceramics increase in proportion to their own temperatures. Therefore, the thermal influence received in the polishing process becomes relatively larger than the thermal influence received in other processes (e.g., bonding).

[0021] In some cases, the glass plate is BK7 glass. BK7 glass has a linear expansion coefficient of 120×10 in the temperature range of -30°C to 70°C -7It is a type of glass plate with a coefficient of linear expansion below / K. BK7 glass has a high transmittance in the wavelength band of 350 nm to 2000 nm, that is, it has high transmittance for visible light. BK7 glass may also be designated by model numbers such as BSC7 and BSL7. Typically, BK7 glass has a coefficient of linear expansion (e.g., average value or maximum value) of 71×10 -7 / K (for example, in the range of -30 °C to 70 °C). The coefficient of linear expansion of BK7 glass increases in proportion to the temperature of the BK7 glass. In the polishing process, individual prism pieces made of BK7 glass can be unevenly heated and expand unevenly.

[0022] In some cases, the glass plates to be sorted are those manufactured in the same lot by the same manufacturer. Glass plates manufactured in the same lot by the same manufacturer can generally be presumed to have the same coefficient of linear expansion. However, due to various influences (e.g., manufacturing conditions, position in the furnace), there may be differences in the coefficient of linear expansion even among glass plates in the same lot. In the present disclosure, the above-described step (A) is adopted to sort good and defective products even for glass plates in the same lot. This avoids or suppresses the manifestation of a decrease in the shape accuracy of the composite prism due to the thermal influence in the polishing process, and avoids or suppresses a decrease in its yield.

[0023] In some cases, two or more glass pieces include a first glass piece having a first surface that is a light incident surface or a light exit surface, and a second glass piece having a second surface that should be arranged in the same plane as the first surface. The step of polishing the surface of the composite prism may include polishing the first surface and the second surface flush. When a coating is formed on the surface of the composite prism, the coating can be formed on at least the polished first and second surfaces.

Advantages of the Invention

[0024] According to one aspect of the present disclosure, it is possible to provide a technique that promotes an increase in the measurement accuracy of the coefficient of linear expansion of a glass plate and, additionally or alternatively, contributes to an improvement in the yield of the composite prism itself assembled from glass pieces cut from a common glass plate.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0026] Hereinafter, non-limiting embodiments and features of the present invention will be described with reference to the drawings. A person skilled in the art can combine each embodiment and / or each feature without excessive explanation, and can also understand the synergistic effect of this combination. Redundant explanations between embodiments are omitted in principle. The reference drawings are mainly for the purpose of describing the invention and are simplified for the convenience of drawing. Each feature is not only effective for the measuring instrument, measuring method, and method for manufacturing a composite prism disclosed in this specification, but is also understood as a universal feature applicable to various other measuring instruments, measuring methods, and methods for manufacturing a composite prism not disclosed in this specification.

[0027] As shown in FIG. 1, the method for manufacturing a composite prism includes a glass plate selection step (S1), a bonding step (S2) of two or more glass pieces cut from a common glass plate, and a polishing step (S3) of the surface of the composite prism formed by bonding two or more glass pieces. The order is not limited to S1, S2, S3, and the order of S1, S3, S2 is also possible.

[0028] First, the measurement system 101 used in the glass plate selection step (S1) will be described with reference to FIGS. 2 to 5. The measurement system 10 includes a measuring instrument 100 and a computer 8. The measuring instrument 100 is for measuring the linear expansion coefficient or the correlation value of the glass plate 1 having a linear expansion coefficient of 120×10 -7 / K or less within the range of normal temperature to 350°C. The thermometer 7 and the laser displacement meter 4 included in the measuring instrument 100 are connected to the computer 8. The computer 8 is not limited to a stand-alone type and may be on a network.

[0029] The measuring instrument 100 includes a first stationary part 31 against which the glass plate 1 is abutted and positioned, and a second stationary part 32 on which a laser displacement meter 4 for measuring the thermal expansion of the glass plate 1 is mounted. The laser displacement meter 4 measures the displacement of a predetermined surface of the glass plate 1 due to the thermal expansion of the glass plate 1 or the displacement of a predetermined surface of another member (for example, the displacement member 3 described later) with which the glass plate 1 is abutted. The laser displacement meter 4 is typically a displacement meter based on the phase difference detection method. Optionally, its minimum resolution is about 100 nm, or 100 nm or less, or 100 nm or more. The glass plate 1 has a pair of main surfaces 11, 12 and one or more side surfaces 13. In the illustrated example, the glass plate 1 has a rectangular shape and has four side surfaces 13. The glass plate 1 is, for example, BK7 glass.

[0030] By the abutment of the glass plate 1 against the first stationary part 31, the glass plate 1 is positioned in the measurement direction (or a direction parallel thereto) by the laser displacement meter 4. Both the first and second stationary parts 31, 32 are 0.5×10 -7It is made of a material with a linear expansion coefficient of 120×10 -7 / K or less. Thus, regardless of the large temperature rise range of the glass plate 1, the change in the distance between the glass plate 1 and the laser displacement meter 4 can be suppressed. Further, the laser displacement meter 4 does not directly contact the glass plate 1, and therefore, the thermal influence on the laser displacement meter 4 itself (for example, its internal structure) can be reduced. In this way, more accurate measurement of the linear expansion coefficient of the glass plate 1 having a linear expansion coefficient of 120×10

[0031] Preferably, the first and second stationary parts 31, 32 are mounted on a support part 21 (for example, blocks 22, 23 running parallel in the measurement direction of the laser displacement meter 4) made of the same material (a material with a linear expansion coefficient of 0.5×10 -7 / K or less), whereby the change in the distance between the first and second stationary parts 31, 32 is suppressed. Specifically, the first stationary part 31 is directly and immovably mounted on the support part 21 (blocks 22, 23). The second stationary part 32 is mounted on the support part 21 (blocks 22, 23) at a position away from the first stationary part 31.

[0032] The measuring instrument 100 can further include a displacement member 3 that is displaceable with respect to the first stationary part 31 and is made of a material with a linear expansion coefficient of 0.5×10 -7 / K or less. In this case, the laser displacement meter 4 measures the displacement of a predetermined surface of the displacement member 3 for measuring the thermal expansion of the glass plate 1. Further, the measuring instrument 100 can include an optional biasing means 6 (see FIG. 3) that biases the displacement member 3 toward the glass plate 1 in a state where the glass plate 1 is sandwiched between the displacement member 3 and the first stationary part 31. The displacement member 3 is always biased toward the glass plate 1 by the biasing means 6, and the contact between the glass plate 1 and the first stationary part 31 and the contact between the glass plate 1 and the second stationary part 32 are always ensured. Note that the first and second stationary parts 31, 32 and the support part 21 construct a support frame 2. The displacement member 3 can also be mounted on the support part 21 in the same manner as the first and second stationary parts 31, 32.

[0033] The measuring instrument 100 can further include a temperature control device 5 for heating and / or cooling the glass plate 1. The temperature control device 5 has a support surface for supporting the glass plate 1, and heats and / or cools the glass plate 1 placed on the support surface. The temperature control device 5 can be mounted on the support portion 21 (blocks 22, 23) and positioned between the first and second stationary portions 31, 32. With the glass plate 1 placed on the temperature control device 5, the glass plate 1 is abutted against the first stationary portion 31 for positioning, and / or the glass plate 1 is sandwiched between the first stationary portion 31 and the displacement member 3.

[0034] The measuring instrument 100 can further include one or more thermometers (non-contact thermometers) 7 for measuring the temperature of the glass plate 1. By measuring the real-time temperature of the glass plate 1 with the thermometer 7, the measurement accuracy of the linear expansion coefficient can be improved. Preferably, a plurality of thermometers 7 are employed, and the temperature of the glass plate 1 is measured at a plurality of locations. Also, the reliability of the temperature measurement can be improved by oversampling in each thermometer 7.

[0035] A computer 8 is connected to the measuring instrument 100. The computer 8 calculates the linear expansion coefficient or the correlation value of the glass plate 1 based on the first output signal S10 from the thermometer 7 and the second output signal S20 from the laser displacement meter 4. The laser displacement meter 4 and the thermometer 7 are input devices of the computer 8. It is also possible to implement the computer 8 on the cloud.

[0036] A description will be given with reference to Fig. 3. The glass plate 1 is placed on the temperature control device 5 and sandwiched between the first stationary part 31 and the displacement member 3. The displacement member 3 is biased toward the glass plate 1 by a biasing means 6. Therefore, the contact between the first stationary part 31 and the glass plate 1 and the contact between the displacement member 3 and the glass plate 1 are always ensured. The biasing means 6 can include a magnetic part (not shown) with the same magnetic poles facing each other and / or an elastic member such as a spring (not shown) inserted between the displacement member 3 and the second stationary part 32. The magnetic part includes a first magnet 6a attached to the displacement member 3 and a second magnet 6b attached to the second stationary part 32, and the first and second magnets 6a, 6b are arranged with the same magnetic poles facing each other, generating a magnetic repulsive force between them.

[0037] The glass plate 1 is sandwiched between a reference plane P1 defined by the first stationary part 31 and a pressed surface P2 of the displacement member 3 facing it. When the glass plate 1 is heated by the temperature control device 5 and expands, the pressed surface P2 of the displacement member 3 is pushed by the glass plate 1, and the displacement member 3 displaces against the bias (e.g., magnetic repulsive force) of the biasing means 6. Conversely, when the glass plate 1 contracts, the displacement member 3 returns to its original position according to the bias (e.g., magnetic repulsive force) of the biasing means 6.

[0038] The displacement member 3 has a measured surface P3 on the side opposite to its pressed surface P2. The laser displacement meter 4 is arranged to face the measured surface P3 of the displacement member 3 at a distance. As shown in Fig. 3, when the glass plate 1 linearly expands and its length increases from L1 to L2, the pressed surface P2 of the displacement member 3 displaces to the side away from the reference plane P1, and the measured surface P3 of the displacement member 3 also displaces in the same direction. As a result, the distance between the measured surface P3 of the displacement member 3 and the laser displacement meter 4 decreases from D1 to D2. Thus, the measured distance of the laser displacement meter 4 has a negative correlation with the temperature rise of the glass plate 1, and the measured distance gradually decreases in response to the temperature rise of the glass plate 1.

[0039] By associating and storing the measured temperature of the glass plate 1 by the thermometer 7 and the measured distance by the laser displacement meter 4 based on time, a group of measurement points (a group of black dots shown in FIG. 4) as shown in FIG. 4 can be obtained. Since the temperature rise rate is large, it takes a certain amount of time to acquire the group of measurement points shown in FIG. 4. However, it is a slight burden compared to the product inspection of the composite prism manufactured by omitting the sorting process (S1) of the glass plate.

[0040] For the sorting of the glass plate 1, the flow shown in FIG. 5 can be adopted. S11 is as described above. It should be added that the measured temperature can be oversampled using each of the plurality of thermometers 7, and / or the measured distance can be oversampled using the laser displacement meter 4. Preferably, both the measured temperature and the measured distance are oversampled during the temperature rise process of the glass plate 1.

[0041] In S12, an approximate line is applied to a group of measurement points. Various statistical processes can be applied to a group of measurement points (temperature and distance acquired at the same time) on the computer 8, thereby improving the measurement accuracy of the linear expansion coefficient and / or enabling the use of a low-resolution laser displacement meter. For example, as the statistical process, the least squares method is exemplified, but it is not limited thereto.

[0042] In S13, the linear expansion coefficient is calculated. For example, the computer 8 calculates the linear expansion coefficient based on the approximate line calculated as described above. The linear expansion coefficient is represented by (ΔD / L)×(1 / ΔK). L represents the length of the glass plate (which coincides with the direction in which expansion or contraction is measured). ΔK represents the temperature difference between two measurement points, and ΔD represents the distance difference between two measurement points. When calculating the linear expansion coefficient based on two adjacent measurement points along the temperature axis, the number of calculable linear expansion coefficients is the number of all measurement points - 1, but when obtaining the approximate line, it is one. Incidentally, instead of calculating the linear expansion coefficient itself, a value correlated with this can also be calculated.

[0043] It is also possible to measure the thermal expansion of the glass plate 1 in consideration of the maximum temperature reached by heating in the grinding process. In some cases, the expansion of the glass plate 1 is measured in a temperature range of at least 30 °C or more.

[0044] In S14, the linear expansion coefficient is compared with the threshold value. If the linear expansion coefficient is less than the threshold value, it is understood that the linear expansion coefficient of the glass plate 1 is sufficiently low, and the glass plate 1 is determined to be a good product. If the linear expansion coefficient is equal to or greater than the threshold value, it is understood that the linear expansion coefficient of the glass plate 1 is not sufficiently low, and the glass plate 1 is determined to be a defective product. Not limited to simple comparison, weighting can also be utilized to enhance the reliability of the determination.

[0045] FIG. 6(a) shows the glass plate 1 selected as a good product in the sorting process (S1). This glass plate 1 is cut into a plurality of glass pieces 1a to 1f as shown in FIG. 6(b), and some of the glass pieces 1a, 1c, 1e are further cut into a triangular prism shape as shown in FIG. 6(c). Next, as shown in FIG. 6(d), the glass pieces 1b, A1, A2 are joined (S2) so that the rectangular parallelepiped glass piece 1b is sandwiched between the triangular prism-shaped glass pieces A1, A2. As the joining method, any method such as adhesion or welding can be adopted. In this way, the composite prism 9 (for example, a composite prism) having the main surfaces 9a, 9b and the inclined surfaces 9c, 9d is assembled.

[0046] Subsequently, as shown in FIG. 7, the surface of the composite prism 9 is polished (S3). Typically, CMP polishing is performed, and polishing is performed until the adjacent surfaces of a plurality of (for example, two) glass pieces facing the CMP apparatus 99 are flush. In the polishing process, the composite prism 9 (and the individual glass pieces 1b, A1, A2) is also heated and expanded by frictional heat. In the present disclosure, the glass pieces are cut out from the glass plate 1 having a sufficiently low linear expansion coefficient in advance, and therefore, the flatness of the main surfaces 9a, 9b of the composite prism 9 after polishing is ensured to be good. Repeating, polishing may be performed before joining the glass pieces.

[0047] Optionally, as shown in FIG. 8, coatings 81 and 82 are formed on the main surfaces 9a and 9b of the composite prism 9. The coatings 81 and 82 can have a predetermined refractive index, for example. The coatings 81 and 82 can be AR coatings. Alternatively, the coatings 81 and 82 can be absorption layers that absorb the leakage light from the composite prism 9. In this case, the absorption layer is removed in the light incident region and the light exit region.

[0048] The composite prism 9 obtained as described above is incorporated into various devices. In some cases, as shown in FIG. 9, the composite prism as the composite prism 9 is incorporated into the camera module 200. The camera module 200 includes a lens module 201, an image sensor 202, a housing 203, and the composite prism 9. The lens module 201 includes one or more lenses and is typically constructed from a combination of a plurality of aspherical lenses. The image sensor 202 performs image acquisition based on the light beam that has entered through the lens of the lens module 201 and reached through the composite prism 9. The imaging axis AX2 of the image sensor 202 is parallel to the optical axis AX1 of the lens module 201. In other words, the image sensor 202 is located radially outward from the optical axis AX1 of the lens module 201. The imaging axis AX2 is equal to the normal line located at the center of the imaging region (pixel arrangement region) of the image sensor 202.

[0049] The composite prism 9 has a light incident portion 91, a light exit portion 92, and an intermediate portion 93 provided between the light incident portion 91 and the light exit portion 92. The light incident portion 91 is located on the optical axis AX1 of the lens module 201, and the light beam that has arrived through the lens of the lens module 201 is incident thereon. The light exit portion 92 is disposed on the imaging axis AX2 of the image sensor 202 and emits the light beam that has propagated through the composite prism 9 toward the image sensor 202. The intermediate portion 93 is located midway between the optical axis AX1 and the imaging axis AX2.

[0050] The composite prism 9 is a joined body of three individual glass blocks corresponding to a light incident portion 91, a light exit portion 92, and an intermediate portion 93. A first joint surface 94 is formed between the light incident portion 91 and the intermediate portion 93, and a second joint surface 95 is formed between the intermediate portion 93 and the light exit portion 92. The glass blocks can be joined by adhesion or welding. When an adhesive is used, a glass block having no or a small refractive index difference is used. Deterioration in the quality of the acquired image by the image sensor 202 is avoided or suppressed.

[0051] The composite prism 9 has a main surface 9a, a main surface 9b, an inclined surface 9c, and an inclined surface 9d. The main surface 9a is formed in a range extending over the light incident portion 91 and the intermediate portion 93 and includes a light incident surface 9e. The main surface 9b is formed on the opposite side of the main surface 9a in a range extending over the intermediate portion 93 and the light exit portion 92 and includes a light exit surface 9f. The inclined surface 9c is formed obliquely with respect to the main surface 9a and includes a first reflection surface on which a light beam incident on the prism 9 through the light incident surface 9e is internally reflected. The inclined surface 9d is oriented obliquely with respect to the main surface 9b and includes a second reflection surface on which a light beam that has guided through the intermediate portion 93 is internally reflected. The composite prism 9 has a thickness defined by the main surface 9a and the main surface 9b.

[0052] Note that the lens module 201, the image sensor 202, and the composite prism 9 are fixed to the housing 203 in an arbitrary manner (e.g., directly or indirectly).

[0053] As shown in FIG. 10, the laser displacement meter 4 is directly opposed to the side surface 13 of the glass plate 1 without passing through the displacement member 3 and can also measure the distance to the side surface 13 of the glass plate 1.

Example

[0054] Using the measuring instrument 100 shown in FIG. 2, the linear expansion coefficient of a glass plate having a width of 100 mm × 100 mm was determined. A laser displacement meter with a minimum resolution of 100 nm was used. The temperature rise range was 50°C, and the glass plate was heated from 25°C to 75°C. The measurement time was about 5 minutes. The displacement amount was 40 μm (100×10 -3 ×(80×10 -7) × 50 = 40) was calculated. Note that 100 in the left side is the width (mm) of the glass plate, and 80 × 10 -7 is the linear expansion coefficient ( / K), and 50 is the temperature rise range (K). The displacement amount due to the linear expansion of the measurement mechanism part is 15 nm (150 × 10 -3 × (0.1 × 10 -7 ) × 10 = 30) was calculated. 150 on the left side is the length (unit: mm) of the support frame 2, and 0.1 × 10 -7 is the linear expansion coefficient ( / K) of the ultra-low thermal expansion rate material of the support frame 2, and 10 is the temperature rise range (K) of the support frame 2.

[0055] Even if the laser displacement meter 4 with a minimum resolution of about 100 nm is adopted by obtaining an approximate line by oversampling and the least squares method, sufficient measurement accuracy could be ensured. Also, the error amount with respect to the displacement amount was negligibly small, and sufficient measurement accuracy could be ensured.

[0056] Comparative Example It has been confirmed that if there is a difference in the linear expansion coefficient between adjacent glass pieces of the composite prism, the quality of the image acquired by the image acquisition device via the composite prism deteriorates. Specifically, when a temperature difference of 30 K occurs between two adjacent glass pieces with a length of 5 mm, a step of about 10 nm may occur between each reflecting surface, which greatly affects the quality of the transmitted image.

[0057] Based on the above disclosure, those skilled in the art can make various changes to each feature and each embodiment.

Explanation of Reference Numerals

[0058] 1: Glass plate 1a~1f: Glass pieces 2: Support frame 3: Displacement member 4: Laser displacement meter 5: Temperature control device 6: Biasing means 7: Thermometer 8: Computer 9: Composite prism 9a: Main surface 9b: Main surface 9c: Inclined surface 9d: Inclined surface 100: Measuring instrument 101: Measurement system

Claims

1. 120 × 10 -7 An instrument for measuring the coefficient of linear expansion of a glass plate having a coefficient of linear expansion of 120 × 10 / K or less or a correlation value thereof a first stationary part against which the glass plate abuts and is positioned; a second stationary part on which a laser displacement meter for measuring the thermal expansion of the glass plate is mounted; The measuring instrument, wherein both the first and second stationary parts are made of a material having a linear expansion coefficient of 0.5×10 -7 / K or less.

2. The measuring instrument according to claim 1, further comprising one or more non-contact thermometers for measuring the temperature of the glass plate.

3. The measuring instrument according to claim 1 or 2, wherein the measured distance is oversampled using the laser displacement meter.

4. Displaceable with respect to the first stationary part at least in accordance with the expansion of the glass plate and further comprising a displacement member made of a material having a linear expansion coefficient of 0.5×10 -7 / K or less, wherein the laser displacement meter measures the displacement of a predetermined surface of the displacement member for measuring the thermal expansion of the glass plate, the measuring instrument according to claim 1 or 2.

5. The measuring instrument according to claim 4, further comprising biasing means for biasing the displacement member toward the glass plate in a state where the glass plate is sandwiched between the displacement member and the first stationary part.

6. The measuring instrument according to claim 1 or 2, further comprising a temperature control device for heating or cooling the glass plate.

7. The measuring instrument according to claim 1 or 2, wherein the glass plate is made of BK7 glass.

8. The measuring instrument according to claim 1 or 2, wherein the laser displacement meter is based on a phase difference detection method.

9. a step of sorting glass plates using the measuring instrument according to claim 1 or 2; a step of bonding two or more glass pieces cut from the glass plates determined to be good products in the sorting step; A method for manufacturing a composite prism, comprising a step of polishing the surface of the composite prism in which the two or more glass pieces are joined.

10. The method for manufacturing a composite prism according to claim 9, wherein the composite prism guides a light beam incident through a lens to an image sensor.

11. The method for manufacturing a composite prism according to claim 9, wherein the two or more glass pieces include a first glass piece having a first surface that is a light incident surface or a light exit surface, and a second glass piece having a second surface to be arranged in the same plane as the first surface.

12. The method for manufacturing a composite prism according to claim 11, wherein the step of polishing the surface of the composite prism includes polishing the first surface and the second surface flush.

13. The method for manufacturing a composite prism according to claim 12, wherein polishing the first surface and the second surface flush includes polishing using a CMP apparatus.

14. The method for manufacturing a composite prism according to claim 13, further comprising forming a coating on the surface of the composite prism, the coating being formed at least on the polished first and second surfaces.

15. 120×10 -7 A method for measuring the linear expansion coefficient or the correlation value thereof of a glass plate having a linear expansion coefficient of / K or less bringing the glass plate into contact with and positioning it against the first stationary part; operating a laser displacement meter mounted on the second stationary part; The measuring method, wherein both of the first and second stationary parts are made of a material having a coefficient of linear expansion of 0.5×10 -7 / K or less.

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