阅读说明：本技术 图像传感器 (Image sensor with a plurality of pixels ) 是由 渡边浩介 上辻康人 于 2020-02-17 设计创作，主要内容包括：在利用包含液体透镜的光学系统在拍摄元件的拍摄面上成像出被摄体的像的图像传感器中,所述光学系统构成为能够与非易失性存储器以及温度传感器一起从主体模块分离,所述非易失性存储器存储有与所述液体透镜的屈光力相对于施加电压的变化量相关的特性信息,所述温度传感器用于检测所述液体透镜的温度,所述主体模块具有控制部,所述控制部进行针对来自所述拍摄元件的图像数据的图像处理、以及液体透镜控制处理,在所述液体透镜控制处理中,根据存储于所述非易失性存储器的所述特性信息、由所述温度传感器检测出的所述液体透镜的温度以及所述液体透镜的屈光力的目标值,决定应施加于所述液体透镜的施加电压并施加于所述液体透镜。(In an image sensor for forming an image of a subject on an imaging surface of an imaging element by using an optical system including a liquid lens, the optical system is configured to be separable from a body module together with a nonvolatile memory for storing characteristic information on a change amount of refractive power of the liquid lens with respect to an applied voltage and a temperature sensor for detecting a temperature of the liquid lens, the body module includes a control unit for performing image processing on image data from the imaging element and liquid lens control processing, and the liquid lens control processing is performed based on the characteristic information stored in the nonvolatile memory, the temperature of the liquid lens detected by the temperature sensor, and a target value of refractive power of the liquid lens, an application voltage to be applied to the liquid lens is determined and applied to the liquid lens.)

1. An image sensor for forming an image of an object on an imaging surface of an imaging element by using an optical system including a liquid lens,

the optical system is configured to be separable from a main body module together with a nonvolatile memory that stores characteristic information relating to a change amount of refractive power of the liquid lens with respect to an applied voltage, and a temperature sensor that detects a temperature of the liquid lens,

the main body module includes a control unit that performs image processing on image data from the imaging element and liquid lens control processing in which an applied voltage to be applied to the liquid lens is determined and applied to the liquid lens based on the characteristic information stored in the nonvolatile memory, the temperature of the liquid lens detected by the temperature sensor, and a target value of refractive power of the liquid lens.

2. The image sensor of claim 1,

the characteristic information is relationship description information indicating a relationship among refractive power, applied voltage, and temperature of the liquid lens.

3. The image sensor of claim 1,

the characteristic information is a part of information of relationship description information representing a relationship among refractive power, applied voltage, and temperature of the liquid lens,

the control unit determines the relationship description information used for the liquid lens control process based on the remaining information of the relationship description information set in advance and the characteristic information read out from the nonvolatile memory.

4. The image sensor of claim 3,

the relationship description information is described by being decomposed into a first parameter and a second parameter whose deviation caused by individual difference of the liquid lens is smaller than the first parameter,

the portion of information includes the first parameter.

5. The image sensor of claim 4,

the first parameter is a temperature independent parameter.

6. The image sensor according to any one of claims 2 to 5,

the relationship description information is information representing a relationship expression representing a correlation among the refractive power, the applied voltage, and the temperature of the liquid lens.

7. The image sensor of claim 6,

the relational expression is an expression representing a relationship between the refractive power of the liquid lens and the applied voltage with a function of temperature as a coefficient.

8. The image sensor of claim 7,

in the expression representing the relationship between the refractive power of the liquid lens and the applied voltage, at least one of the refractive power of the liquid lens and the applied voltage is expressed by a polynomial expression relating to the other.

Technical Field

The present invention relates to an image sensor using a liquid lens.

Background

In recent years, various optical devices (imaging devices and the like) using a liquid lens have been developed. The liquid lens is an optical member in which the shape of the boundary surface between a conductive aqueous solution and a non-conductive oil enclosed in a lens holder changes by voltage application, and refractive power changes.

The refractive power/applied voltage characteristic of the liquid lens varies according to the temperature of the liquid lens. Therefore, there is a problem that the refractive power of the liquid lens deviates from a desired value due to the surrounding environment in which the optical device is placed or heat generation caused by energization of the optical device itself. There are 2 methods for avoiding this problem, and one is a method for keeping the temperature of the liquid lens constant by heating control in the optical device (for example, see patent document 1). Another method is a method of observing the temperature of the liquid lens, correcting the voltage value according to the temperature thereof, and supplying the voltage value to the liquid lens.

Documents of the prior art

Patent document

Patent document 1: U.S. patent application publication No. 2017/0090076 specification

Disclosure of Invention

Problems to be solved by the invention

The former method requires a heating unit, and thus has a problem that power consumption of the apparatus becomes large. The latter method has an advantage of low power consumption, but requires accurate determination of the correction value of the applied voltage. Further, the characteristics of the liquid lens vary from individual to individual, and even if the applied temperature and the applied voltage are the same, the refractive power varies from individual to individual. Therefore, the voltage value correction in the latter method needs to take into account not only the temperature but also the influence of individual differences. Therefore, in order to produce an image sensor capable of performing the applied voltage correction in consideration of the individual difference of the liquid lens, it is necessary to obtain accurate correction information for each image sensor (liquid lens).

An image sensor for automatic inspection or process control is equipped with an image processing unit (MPU, DSP, etc.). Therefore, it is also conceivable to obtain information for correction for each image sensor by the image processing unit. However, in an image sensor manufactured as a relatively compact image sensor called a smart camera, a liquid lens is generally located in the vicinity of an image processing unit, and the volume of a space inside a housing is small. Therefore, it can be said that the following configuration: the liquid lens is easily affected by heat generation of the image processing unit, and the heat is easily enclosed inside the image sensor. Therefore, in the production process of the image sensor, when the energization is started to obtain the correction information for each individual, the temperature starts to rise in the case interior, depending on the conditions, but it may take several tens of minutes before the thermal equilibrium is reached. On the other hand, in order to obtain accurate correction information, it is necessary to measure the optical characteristics of the liquid lens under a constant temperature environment.

Therefore, when the image processing unit is used, voltage correction information in consideration of individual differences of the liquid lenses cannot be obtained with sufficient accuracy without lowering the production efficiency.

The present invention has been made in view of the above problems, and an object thereof is to provide an image sensor that can perform correction of an applied voltage in consideration of individual differences of liquid lenses and can be efficiently produced.

Means for solving the problems

An image sensor according to an aspect of the present invention is an image sensor for forming an image of a subject on an imaging surface of an imaging element by using an optical system including a liquid lens, wherein the optical system is configured to be separable from a main body module together with a nonvolatile memory storing characteristic information relating to a change amount of refractive power of the liquid lens with respect to an applied voltage and a temperature sensor for detecting a temperature of the liquid lens. The main body module of the image sensor includes a control unit that performs image processing on image data from the image pickup device and liquid lens control processing in which an applied voltage to be applied to the liquid lens is determined and applied to the liquid lens based on the characteristic information stored in the nonvolatile memory, the temperature of the liquid lens detected by the temperature sensor, and a target value of refractive power of the liquid lens.

That is, the image sensor can separate a portion (hereinafter, referred to as a lens module) where an optical system including a liquid lens and the like are provided from a main body module having a control section that performs image processing on image data from the imaging element. If the lens module is separated from the main body module, the influence of the heat generation amount of the control unit is eliminated, and therefore the temperature of the liquid lens during the characteristic measurement can be kept constant. As a result, the characteristic information for determining the applied voltage can be accurately obtained in a short time. The lens module includes a nonvolatile memory for storing accurately obtained characteristic information, and a temperature sensor for detecting a temperature of the liquid lens. Therefore, if the above-described structure is adopted, it is possible to realize an image sensor that can perform correction of the applied voltage in consideration of individual differences of the liquid lenses and that can be produced efficiently.

The characteristic information stored in the nonvolatile memory may be information that can determine the applied voltage to be applied to the liquid lens (i.e., the applied voltage at which the refractive power of the liquid lens matches the target value) from the temperature of the liquid lens and the target value of the refractive power of the liquid lens using the characteristic information. Therefore, the characteristic information may be the relation description information itself indicating the relation between the refractive power, the applied voltage, and the temperature of the liquid lens, or may be a part of the relation description information.

The image sensor may be configured to include "the characteristic information is a part of relationship description information indicating a relationship between refractive power, applied voltage, and temperature of the liquid lens," and the control unit may determine the relationship description information used in the liquid lens control process based on remaining information of the relationship description information set in advance and the characteristic information read from the nonvolatile memory. In the case where the image sensor employs this structure, as the relationship description information, information described by being decomposed into a first parameter and a second parameter whose deviation caused by an individual difference of the liquid lens is smaller than the first parameter is employed, and as the part of information, information including the first parameter is employed. In addition, a parameter independent of temperature in the relationship description information may also be selected as the first parameter.

The relationship description information (the characteristic information itself, or information constituted by the characteristic information and information in the control unit) may be tabular information (including information indicating the refractive power of the liquid lens when a certain applied voltage is applied to a liquid lens at a certain temperature, and the like) indicating the relationship between the refractive power of the liquid lens, the applied voltage, and the temperature. The relationship description information may include information indicating a relationship between optical power and applied voltage for each temperature.

The relationship description information may also be information representing a relationship expression that represents a relationship among the refractive power, the applied voltage, and the temperature of the liquid lens. The relational expression represented by the relational description information may also be an expression representing a relation between the refractive power of the liquid lens and the applied voltage with a function of temperature as a coefficient. In the expression indicating the relationship between the refractive power of the liquid lens and the applied voltage, at least one of the refractive power of the liquid lens and the applied voltage may be expressed by a polynomial expression relating to the other.

The relationship description information may be information composed of a coefficient of a functional expression and information in a table format. That is, the relationship description information may be information constituted by, for example, a coefficient of one of functional expressions g (T) and h (V) of temperature T and refractive power P at applied voltage V, and information in a table format for obtaining a value of the other functional expression, which can be calculated by the following operation.

P＝g(T)·h(V)

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide an image sensor that can perform correction of applied voltage in consideration of individual differences of liquid lenses and can be efficiently produced.

Drawings

Fig. 1 is an explanatory diagram of a schematic configuration of an image sensor according to an embodiment of the present invention.

Fig. 2 is a flowchart of the 1 st liquid lens process executed by the control section of the image sensor.

Fig. 3 is a flowchart of the 2 nd liquid lens process executed by the control section of the image sensor.

Fig. 4 is an explanatory diagram of a schematic configuration of an inspection system prepared to set characteristic information for an image sensor.

Fig. 5 is a flowchart of characteristic information setting processing executed by the inspection device of the inspection system.

Fig. 6 is an explanatory diagram of an execution environment of the property information setting processing.

Fig. 7 is an explanatory diagram of the processing in step S303 of the characteristic information setting processing.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 shows a schematic configuration of an image sensor 1 according to an embodiment of the present invention.

The image sensor 1 of the present embodiment is a device which is supposed to be connected to a host device 50 and developed for automatic inspection or process control. The host device 50 is a computer on which a program for using the image sensor 1 is installed. A plurality of image sensors 1 are generally connected to the host device 50.

As shown in the figure, the image sensor 1 is composed of a lens module 10 having an optical system 11, a temperature sensor 15, and a nonvolatile memory 16, and a main body module 20 having an imaging element 21 and a control unit 22.

The optical system 11 is a combined lens for forming an image of light from a subject (subject) on an imaging surface of the imaging element 21. In the optical system 11, a liquid lens 12 capable of controlling refractive power by changing an applied voltage is used.

The temperature sensor 15 is a sensor for detecting the temperature of the liquid lens 12. As the temperature sensor 15, for example, a resistance temperature sensor or a temperature sensor IC is used.

The nonvolatile memory 16 is a memory for storing characteristic information. As the nonvolatile memory 16, a serial bus type memory (having SPI and I) is generally used²C, a memory of the serial interface; such as a serial EEPROM).

The characteristic information stored in the nonvolatile memory 16 is information for determining a voltage to be applied to the liquid lens 12. The characteristic information may be information that can determine, using the characteristic information, an applied voltage that matches the refractive power of the liquid lens 12 at the current temperature with a target value of the refractive power of the liquid lens 12, based on the temperature of the liquid lens 12 and the target value of the refractive power of the liquid lens 12. The characteristic information may be information that can correct the applied voltage of the liquid lens 12 whose temperature is within the operation guaranteed temperature range.

The details of the characteristic information set in the image sensor 1 (the nonvolatile memory 16) of the present embodiment and the specific procedure of setting the characteristic information in the image sensor 1 will be described later.

The lens module 10 is a module in which an optical system 11, a temperature sensor 15, and a nonvolatile memory 16 are mounted in a housing (not shown). The lens module 10 is configured to be attachable to and detachable from the body module 20. The lens module 10 is provided with a connector 10c, and when the lens module 10 is mounted on the body module 20, the connector 10c is fitted to the connector 20c of the body module 20. The connector 10c and the respective parts of the lens module 10 (the liquid lens 12, the temperature sensor 15, and the nonvolatile memory 16), and the connector 20c and the control unit 22 of the main body module 20 are wired as schematically shown by solid lines and broken lines in fig. 1. That is, the connector 10c and each part of the lens module 10 and the connector 20c and the controller 22 are wired so that the liquid lens 12, the temperature sensor 15, and the nonvolatile memory 16 are electrically connected to the controller 22 when the connector 10c is fitted to the connector 20 c.

The imaging element 21 is a two-dimensional image sensor such as a CMOS image sensor or a CCD image sensor.

The control unit 22 is a unit that performs various image processing on the image data from the imaging element 21, and performs processing for notifying the host device 50 of the processing result and liquid lens control processing for applying the temperature-corrected applied voltage to the liquid lens 12. The various image processing means reading processing of a barcode or the like, determination processing of the presence or absence of an abnormality, and the like. The control unit 22 is configured by, for example, a driver IC and a microcontroller that generate an application voltage to be applied to the liquid lens 12.

The liquid lens control processing performed by the control unit 22 includes a 1 st liquid lens control processing and a 2 nd liquid lens control processing. The 1 st liquid lens control processing is processing performed by the control section 22 when the power of the image sensor 1 is turned on. The 2 nd liquid lens control processing is processing performed by the control unit 22 when an instruction to change the installation distance is given from the host device 50. Here, the set distance means a distance called a working distance, or the like.

The 1 st liquid lens control process performed by the control unit 22 is a process of the procedure shown in fig. 2.

That is, the control unit 22, which has started the 1 st liquid lens control process when the power of the image sensor 1 is turned on, first reads out the characteristic information from the nonvolatile memory 16 of the lens module 10 and stores the characteristic information therein (step S101). Next, the control unit 22 measures the temperature of the liquid lens 12 based on the output of the temperature sensor 15 (step S102).

Then, the control unit 22 identifies an applied voltage that can match the refractive power of the liquid lens 12 at the current temperature with the target value, using the characteristic information (in fig. 2, the acquired characteristic information) acquired from the lens module 10 (nonvolatile memory 16) and stored therein (step S103). As will be described later in detail with respect to the processing in step S103, the "target value" in the 1 st liquid lens control processing is the refractive power of the liquid lens 12 corresponding to the set distance (the set distance previously set by the user or the default set distance) set in the image sensor 1 at the execution time of the 1 st liquid lens control processing. The refractive power of the liquid lens 12 corresponding to the installation distance is the refractive power of the liquid lens 12 focused (in focus) on the object whose distance from the distal end of the optical system 11 matches the installation distance.

After the control unit 22 that has finished the processing of step S103 performs the processing of applying the determined applied voltage to the liquid lens 12 (step S104), it ends the 1 st liquid lens control processing.

The 2 nd liquid lens control process executed by the control section 22 when an instruction to change the installation distance is given is a process of the procedure shown in fig. 3.

The processing in steps S201 and S203 of the 2 nd liquid lens control processing is the same as the processing in steps S102 and S104 of the 1 st liquid lens control processing, respectively. The process of step S202 of the 2 nd liquid lens control process is a process different from the process of step S103 of the 1 st liquid lens control process only in the following respects: the "target value" is the refractive power of the liquid lens 12 corresponding to the set distance specified by the change instruction.

That is, the 2 nd liquid lens control processing (fig. 3) and the 1 st liquid lens control processing (fig. 2) performed when the power of the image sensor 1 is turned on are processes having substantially the same contents. However, since the 1 st liquid lens control process has been executed when the power of the image sensor 1 is turned on, the control section 22 has already held the characteristic information on the liquid lens 12 when the 2 nd liquid lens control process is executed. Therefore, the 2 nd liquid lens control process is a process of not performing a process of reading out the characteristic information from the nonvolatile memory 16 of the lens module 10.

The details of the characteristic information set in the image sensor 1 and the specific processing procedure of the processing in steps S103 and S202 will be described below. In the following description, the refractive power of the liquid lens 12 is also simply referred to as refractive power.

The image sensor 1 of the present embodiment is configured as a device that stores 2 real values as characteristic information in the nonvolatile memory 16.

Specifically, as shown in the following expressions (1) to (3), the liquid lens 12 used in the image sensor 1 expresses the refractive power P at the temperature T and the applied voltage V by a linear expression of the applied voltage V having the linear expression s (T) of the temperature T as a coefficient of 1 and the linear expression y (T) of the temperature T as a coefficient of 0.

P＝S(T)×V+Y(T)…(1)

S(T)＝s₂×T²+s₁×T+s₀…(2)

Y(T)＝y₂×T²+y₁×T+y₀…(3)

And, for the liquid lens 12, s₀And y₀The value of (a) is relatively largely deviated by the difference in solids, and the other 4 coefficients(s)₂、s₁、y₂、y₁) The value of (a) is hardly deviated by the difference in solid. When the respective coefficient values that hardly deviate due to the difference in the solid state of the liquid lens 12 are stored in the nonvolatile memory 16, the storage capacity of the nonvolatile memory 16 is wastefully used. Thus, the image sensor 1 passes s₂Value s₁Value y₂Value of y₁The value is preset in the control unit 22 so that only s is stored in the nonvolatile memory 16₀Value and y₀Means for obtaining a value.

In addition, since the characteristic information is the above information, the 1 st and 2 nd liquid lens controlsThe processing of steps S103 and S202 of the manufacturing process (fig. 2 and 3) is to use the preset S₂Value s₁Value y₂Value of y₁The value to calculate the processing of the applied voltage. More specifically, the processing in steps S103 and S202 is as follows: using a predetermined s₂Value s₁Value y₂Value of y₁Value, s obtained from lens module 10₀Value of y₀The applied voltage V is calculated by performing the following calculations (see expressions (1) to (3)) on the value, the temperature T of the liquid lens 12, and the target refractive power Ptgt of the liquid lens 12.

V＝(Ptgt-(y₂×T²+y₁×T+y₀))/(s₂×T²+s₁×T+s₀)…(4)

Hereinafter, a process of setting the characteristic information to the image sensor 1 will be described.

Fig. 4 shows a schematic configuration of an inspection system 40 provided for setting characteristic information for the image sensor 1. As shown in the drawing, the inspection system 40 provided for setting characteristic information on the image sensor 1 is composed of an inspection jig 30 and an inspection device 35.

The inspection jig 30 corresponds to the body module 20 from which the control unit 22 is removed. That is, the inspection jig 30 is configured to be able to mount the lens module 10. The inspection jig 30 is configured such that, when the lens module 10 is mounted, the connector 10c of the mounted lens module 10 (hereinafter also referred to as a mounting module 10) is fitted to the connector 30 c. The inspection jig 30 is configured such that when the lens module 10 is mounted, the positional relationship between the optical system 11 of the mounting module 10 and the imaging device 31 is the same as the positional relationship between the optical system 11 and the imaging device 21 when the body module 20 is mounted on the lens module 10.

In addition, the inspection jig 30 has a connector 32. The connector 32, the connector 30c, and the imaging element 31 are wired so that the inspection device 35 is connected to the liquid lens 12, the temperature sensor 15, the nonvolatile memory 16, and the imaging element 31 when a cable from the inspection device 35 is connected to the connector 32.

The inspection device 35 is a device configured to be capable of executing a characteristic information setting process of obtaining characteristic information about the liquid lens 12 in the mount module 10 and writing the characteristic information into the nonvolatile memory 16 in the mount module 10. As already described (defined), the mounting module 10 refers to the lens module 10 mounted on the inspection jig 30.

Fig. 5 is a flowchart of the characteristic information setting process.

This characteristic information setting process is performed in a state where the temperatures of the mounting module 10 and the inspection jig 30 are controlled to a constant temperature (25 degrees celsius in the present embodiment). In the inspection device 35, as in the main body module 20 (control unit 22), a coefficient s is set in advance, which is not present or is small in variation due to individual difference of the liquid lens 12 among the coefficients of the above-described formulas (2) and (3)₂、s₁、y₂、y₁The value of (c).

As shown in fig. 5, in the characteristic information setting process, first, a process of searching for the applied voltage V1 focused on the photographed workpiece 1 (step S301) and a process of searching for the applied voltage V2 focused on the photographed workpiece 2 (step S302) are performed. Here, as schematically shown in fig. 6, the imaging workpieces 1 and 2 are subjects for focus adjustment disposed at positions where the distances 1 and 2 are set. Hereinafter, the refractive power of the lens 12 corresponding to the set distance n (n is 1 or 2) is described as refractive power n.

The processing in steps S301 and S302 of the characteristic information setting processing of the present embodiment is as follows: by repeating the process of analyzing the image data from the imaging element 31 while changing the applied voltage applied to the liquid lens 12, the applied voltage with the maximum contrast between adjacent pixels is searched for, and the search results are set as the applied voltages V1 and V2. However, the processing in steps S301 and S302 may be any processing as long as it is processing capable of searching for an applied voltage for focusing.

When the process of step S302 is completed, the slope a and intercept b of a straight line (refractive power/applied voltage straight line in fig. 5) representing the relationship between refractive powers 1, 2 and applied voltages V1, V2 are calculated (step S303). More specifically, as shown in fig. 7, in the orthogonal coordinates where the vertical axis is the refractive power and the horizontal axis is the applied voltage, the slope a and the intercept b of the straightness of the point passing through the coordinates (applied voltage V1, refractive power 1) and the point passing through the coordinates (applied voltage V2, refractive power 2) are calculated.

Then, based on the calculated slope a, intercept b, and the like, s of the above-mentioned expression (2) is calculated₀The value and y of the above-mentioned formula (3)₀The value (step S304). That is, in step S304, the known numbers (S) are added₂Value s₁Value, a value, and T value) into s₀＝a-s₂×T²-s₁X T to calculate s₀The value is obtained. In addition, in step S304, the known numbers (y) are added₂Value y₁Value, b value, and T value) into y₀＝b-y₂×T²-y₁X T to calculate y₀The value is obtained. In the former expression, the expression (2) in which S (T) is replaced by a is modified to s₀The expression obtained by transforming the expression (3) wherein Y (T) is replaced by b into the expression related to y₀The formula (2) is obtained.

Then, s is carried out₀Value of y₀After the process of writing the value as the property information into the nonvolatile memory 16 of the mounting module 10 (step S305), the property information setting process is ended.

As described above, the image sensor 1 of the present embodiment is configured such that the lens module 10 provided with the optical system 11 including the liquid lens 12 can be separated from the main body module 20 provided with the control unit 22. If the lens module 10 is separated from the main body module 20, the temperature of the liquid lens 12 does not change due to the influence of the amount of heat generated by the control unit 22, and therefore, the characteristic information can be accurately obtained for each liquid lens 12 used in each image sensor 1. The lens module 10 includes a nonvolatile memory 16 for storing accurately obtained characteristic information and a temperature sensor 15 for detecting the temperature of the liquid lens 12. Therefore, the control unit 22 of the image sensor 1 (the control unit 22 in the body module 20 after the lens module 10 is mounted) can perform the applied voltage correction of the liquid lens 12 in consideration of the temperature difference and also in consideration of the individual difference of the liquid lens 12.

Modifications of the examples

The image sensor 1 of the above embodiment can be variously modified. For example, when the refractive power of the liquid lens 12 is expressed by the above expressions (1) to (3), but the values of all the coefficients of expressions (2) and (3) vary depending on individual differences, the image sensor 1 can be modified such that all the coefficients(s) of expressions (2) and (3) are stored in the nonvolatile memory 16₂、s₁、s₀、y₂、y₁And y₀) As a means of characteristic information. In addition, the image sensor 1 can be modified to the device in which the control unit 22 is modified so that s in the characteristic information obtained from the lens module 10 is used for the calculation of the applied voltage V in the expression (4)₂Value s₁Value y₂Value y₁The value is obtained. Further, if the applied voltage focused on the photographed workpiece is searched under 6 conditions in which the combination of the temperature and the set distance is different, the values of all the coefficients of expressions (2) and (3) can be calculated from the search result.

When the refractive power of the liquid lens 12 cannot be sufficiently approximated by equation (1) (i.e., the linear expression of V), the characteristic information may be the values of all or a part of the coefficients of equation (5) or equation (6) below. The coefficient in the case where the characteristic information is a value of a part of the coefficients of each of the formulae may be determined (selected) based on the degree of variation due to individual differences of the liquid lenses 12 or the like.

In these formulae, n is an integer of "2" or more. In addition, C_i(T) (i is 0 to n) is a temperature T which represents a coefficient value of an i-th term of an n-th expression of the (5) expression as a refractive power PA function. D_i(T) (i ═ 0 to n) is a function of temperature T representing the coefficient value of the i-th order term of expression (6) as the n-th order expression of applied voltage V.

The above-described expressions (1) to (3), (5), and (6) are all expressions that represent the relationship between the refractive power P of the liquid lens 12 and the applied voltage V using a function of the temperature T as a coefficient, but as described above, the characteristic information may be any information that can determine the applied voltage that matches the refractive power of the liquid lens 12 at the current temperature with the target value from the temperature of the liquid lens 12 and the target value of the refractive power of the liquid lens 12 using the characteristic information. Therefore, the characteristic information may be information (hereinafter referred to as relationship description information) itself indicating a relationship among the refractive power, the applied voltage, and the temperature of the liquid lens 12, or may be a part of the relationship description information. The relationship description information is not limited to the correlation information of "an expression representing the relationship between the refractive power P of the liquid lens 12 and the applied voltage V with a function of the temperature T as a coefficient". For example, the relationship description information may be related information of "an expression representing a relationship between refractive power P and temperature T having a function of applied voltage V as a coefficient". The relationship description information may be information composed of a coefficient of a functional expression and information in a table format. That is, the relationship description information may be information constituted by, for example, a coefficient of one of the functional expressions g (T) and h (V) of the refractive power P at the temperature T and the applied voltage V, and information in a table format for obtaining a value of the other functional expression, which can be calculated by the following operation.

P＝g(T)·h(V)

While the example using the coefficients of the relational expression has been described as an example of the relational description information (information of which a part or all is stored in the nonvolatile memory 16 as the characteristic information), the relational description information may be information in a table format indicating the relationship between the refractive power, the applied voltage, and the temperature of the liquid lens 12 (information including a plurality of information indicating the refractive power of the liquid lens when a certain applied voltage is applied to the liquid lens 12 at a certain temperature). The relationship description information may include information indicating a relationship between optical power and applied voltage for each temperature. Even when the above-described information (i.e., information that is not a coefficient of the relational expression) is used as the relational description information, the characteristic information stored in the nonvolatile memory 16 can be made temperature-independent information.

The relationship description information may be information that does not directly indicate the relationship between the refractive power, the applied voltage, and the temperature (for example, information indicating the relationship between a value (working distance, etc.) related to the refractive power, the applied voltage, and the temperature).

Please note

An image sensor (1) for forming an image of an object on an imaging surface of an imaging element (21) by an optical system (11) including a liquid lens (12), the image sensor (1),

the optical system (11) is configured to be separable from a main body module (20) together with a nonvolatile memory (16) and a temperature sensor (15), the nonvolatile memory (16) stores characteristic information relating to a change amount of refractive power of the liquid lens (12) with respect to an applied voltage, the temperature sensor (15) detects a temperature of the liquid lens (12),

the main body module (20) has a control unit (22), and the control unit (22) performs image processing on image data from the imaging element (21) and liquid lens control processing in which an application voltage to be applied to the liquid lens (12) is determined and applied to the liquid lens (12) based on the characteristic information stored in the nonvolatile memory (16), the temperature (12) of the liquid lens detected by the temperature sensor (15), and a target value of the refractive power of the liquid lens (12).

Description of the reference symbols

1: an image sensor; 10c, 20c, 30c, 32: a connector; 10: a lens module; 11: an optical system; 12: a liquid lens; 15: a temperature sensor; 16: a non-volatile memory; 20: a body module; 21. 31: an imaging element; 22: a control unit; 30: inspecting the fixture; 35: an inspection device; 40: an inspection system; 50: and a host device.