JP6343253B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus.

  An imaging apparatus represented by a camera or the like includes an image sensor chip. The image sensor chip has, for example, a substrate made of a semiconductor or the like, and a plurality of pixels arranged on the substrate.

  The image surface of the optical lens may be curved in a concave shape (field curvature). Therefore, for example, in a photographed image, it may occur that the focus is in the central part (or the peripheral part) but the focus is not in the peripheral part (or the central part). Accordingly, a method of bending the image sensor chip so as to match the curvature of field can be considered. Since the degree of field curvature varies depending on the state of the optical lens, for example, when the optical lens is replaced or the position of the optical lens is changed, the state of curvature of the image sensor chip may be adjusted accordingly.

JP 2012-182194 A JP 2005-235949 A

  Patent Document 1 describes that an image sensor chip is bent in accordance with the position of an optical lens and the state of the curve is controlled. However, in Patent Document 1, how to measure the actual state of the curvature of the image sensor chip and what kind of control is performed to bring the actual state of the curvature closer to the target (desired state). Is not described.

  Here, Patent Document 2 describes that image data is acquired from an image sensor chip, shading in the image is analyzed, and the curvature state of the image sensor chip is controlled based on the result. However, according to the method of Patent Document 2, when the image does not follow uniform light (for example, when a subject such as a person or a landscape is reflected in the image), it becomes difficult to analyze the shading itself. There is a possibility that the accuracy of the control is lowered.

  An object of the present invention is to provide a technique advantageous in increasing the accuracy of the control in an imaging device that controls the state of curvature of an image sensor chip according to the field curvature of an optical lens.

  One aspect of the present invention relates to an imaging apparatus, and the imaging apparatus includes an image sensor chip having a pixel area in which a plurality of pixels are arranged, and the image sensor is curved so that the pixel area is curved. A control unit that controls the bending state of the chip; a measuring unit that is disposed in a peripheral region of the pixel region in the image sensor chip and measures the bending state of the image sensor chip; and a state of an optical lens used for photographing A setting unit that sets a target of the state of curvature of the image sensor chip based on the control unit, and the control unit is based on a result of comparing the measured state of curvature and the set target The bending state is controlled.

  According to the present invention, the control of the bending state can be made highly accurate.

FIG. 25 is a block diagram for explaining an example of a configuration of an imaging apparatus. It is a flowchart for demonstrating the control method of the curvature state of an image sensor chip. It is a schematic diagram for demonstrating the example of the structure of an imaging device. It is a schematic diagram for demonstrating the example of the structure of an image sensor chip. It is a figure for demonstrating the example of a structure of a measurement part. It is a figure for demonstrating the example of a structure of a measurement part.

  FIG. 1 shows a configuration example of an imaging apparatus 100 according to the present invention. The imaging apparatus 100 includes, for example, an image sensor chip 110, a bending control unit 120, a measurement unit 130, and a setting unit 140. The image sensor chip 110 includes a pixel array 111, a driving unit 112, a reading unit 113, an output unit 114, and a photographing control unit 115, which are formed on a single substrate made of a semiconductor such as silicon.

  The pixel array 111 includes, for example, a plurality of pixels PX arranged in an array (so as to form a plurality of rows and a plurality of columns). Each pixel PX may have a known pixel configuration. For example, the pixel PX includes a photoelectric conversion element and one or more transistors for reading a signal corresponding to the charge generated in the photoelectric conversion element or the amount thereof. The one or more transistors include, for example, a transistor that transfers charges generated in the photoelectric conversion element, a transistor that amplifies a signal corresponding to the amount of the transferred charge, and a transistor that resets the photoelectric conversion element.

  The drive unit 112 includes, for example, a shift register and the like, and sequentially drives the plurality of pixels PX in units of rows based on a control signal from the imaging control unit 115. The reading unit 113 includes, for example, a signal amplification unit, an AD conversion unit, and the like, reads out pixel signals from the respective pixels PX driven by the driving unit 112 based on a control signal from the imaging control unit 115, and outputs the output unit 114. Forward to. The output unit 114 sequentially outputs the transferred pixel signal as image data based on the control signal from the imaging control unit 115.

  The pixel array 111 is arranged in a central region (referred to as “region R1”) on the substrate in a plan view (hereinafter simply referred to as “plan view”) with respect to the upper surface of the substrate. The region R1 may be referred to as a pixel region. In addition, the driving unit 112, the reading unit 113, the output unit 114, and the imaging control unit 115 are arranged in a peripheral region of the region R1 (referred to as “region R2”) in plan view.

  The bending control unit 120 bends the image sensor chip 110 so that the region R1 is bent, and controls the bending state of the image sensor chip 110. The state of bending may be specified by the amount of bending or may be specified by the bending rate. For example, the curved state may be specified by the height difference between the center portion and the end portion of the curved image sensor chip 110, or specified by the curvature when the structure in the cross section in a predetermined direction is approximated to an arc. May be. Alternatively, the state of bending may be specified by another physical quantity indicating the degree of bending.

  Note that the image sensor chip 110 may be curved in at least one direction. For example, when the image sensor chip 110 has a rectangular shape having a long side and a short side in plan view, the image sensor chip 110 may be curved in the long side direction. Here, the image sensor chip 110 having a rectangular shape is illustrated as a typical example, but the image sensor chip 110 may take other shapes depending on the purpose or the like.

  The measurement unit 130 measures the bending state of the image sensor chip 110. Although details will be described later, the measurement unit 130 is disposed, for example, in the peripheral region R2 on the substrate. For example, the measurement unit 130 measures the bending state substantially constantly or at a predetermined cycle, and outputs the measurement result to the bending control unit 120.

  The setting unit 140 sets the target of the curved state based on the state of an optical lens (for example, an optical lens that is attached to the imaging device 100 or further included in the imaging device 100) used for shooting. More specifically, the setting unit 140 sets a desired state based on the field curvature assumed for the optical lens as a target for the above-described curved state. The setting unit 140 outputs the set target to the bending control unit 120.

  The bending control unit 120 compares the bending state of the image sensor chip 110 measured by the measuring unit 130 with the target set by the setting unit 140, and feeds back the comparison result to the control of the bending state. . That is, the bending control unit 120 adjusts the actual bending state of the image sensor chip 110 based on the result of the comparison so that it approaches the set target. According to this configuration, the state of bending of the image sensor chip 110 can be measured by the measurement unit 130 at a desired timing, and the result can be fed back to the control of the state of bending.

  The setting unit 140 sets a target corresponding to information on the optical lens. For example, the setting unit 140 can set or update the target of the curved state in response to a result of monitoring the state of the optical lens that is substantially always or at a predetermined cycle. For example, when the state of the optical lens is changed between when the imaging apparatus 100 is ready to shoot in still image shooting and before the user presses a switch for starting shooting, the set target is It is updated to the one corresponding to the optical lens whose state has been changed. The case where the state of the optical lens is changed includes, for example, the case where the optical lens is replaced in a lens interchangeable camera. When the optical lens is replaced, for example, the setting unit 140 receives information indicating the model number and the focal length from the optical lens, and sets a target corresponding to the information. Further, when the state of the optical lens is changed, for example, the case where the position of the optical lens in the imaging apparatus 100 (the position of the optical lens with respect to the image sensor chip 110) is changed for the purpose of zooming in or out of the subject. Including. When the position of the optical lens is changed, the setting unit 140 indicates the position of the optical lens, for example, from the optical lens or from a lens driving unit that drives the optical lens to control its position. Receiving information, a target corresponding to the information is set.

  The setting unit 140 may include, for example, a memory (not shown) that stores a reference table and a selection unit (not shown) that selects a parameter corresponding to the state of the optical lens with reference to the reference table. In the above-described example, the selection unit can select, for example, a parameter corresponding to the model number of the optical lens, or a parameter corresponding to the position of the optical lens. In this case, the bending control unit 120 controls the bending state of the image sensor chip 110 based on the selected parameter. In another embodiment, the setting unit 140 may include a calculation unit (not shown), and the parameters described above may be calculated by the calculation unit by a predetermined calculation process based on the state of the optical lens.

  FIG. 2 is a flowchart for explaining a method for controlling the bending state of the image sensor chip 110. In step S200 (hereinafter, simply referred to as “S200”, the same applies to other steps), the setting unit 140 sets a target for the state of curvature of the image sensor chip 110 and corresponding to the state of the optical lens. To do. In S <b> 210, the measurement unit 130 measures the bending state of the image sensor chip 110. In S220, it is determined whether or not the target set in S200 matches the bending state measured in S210. If they match, this control is terminated, and if they do not match, the process proceeds to S230. In S230, the curved state is adjusted so that it approaches the target. Note that S200 and S210 may be performed in the reverse order or in parallel. Moreover, although the case where it returns to S210 after S230 is illustrated in the figure, you may return to S200.

  For example, in the case of still image shooting, the above-described control is substantially always or at a predetermined cycle from when the imaging apparatus 100 is ready to shoot until the user presses a switch for starting shooting. It only has to be done. In addition, for example, in the case of moving image shooting, this control may be performed substantially always or at a predetermined cycle during shooting.

  3A to 3C are schematic diagrams for explaining an example of the structure of the imaging apparatus 100. FIG. As illustrated in FIG. 3A, the image sensor chip 110 and the bending control unit 120 are accommodated in a package 170 for protecting them from the external environment. The package 170 includes, for example, a casing-shaped member 171 and a translucent plate member 172. The subject is imaged on the image sensor chip 110 through the optical lens 150 and the optical filter 160, for example. At this time, the image surface can be curved concavely due to lens aberration. The bending control unit 120 may bend the image sensor chip 110 so as to match this image plane.

  As illustrated in FIG. 3B, the bending control unit 120 is disposed on the surface opposite to the light receiving surface of the image sensor chip 110, and by a predetermined means for bending the image sensor chip 110. The image sensor chip 110 is bent. As a means for bending the image sensor chip 110, a known device may be used. For example, the image sensor chip 110 may be supported by a support portion (not shown) at its end, and the image sensor chip 110 may be bent by changing the position of the support portion. In another example, the image sensor chip 110 may be curved by suction. In another example, a magnetic field may be supplied to the image sensor chip 110, and the image sensor chip 110 may be bent by the magnetic force. In another example, heat may be supplied to the image sensor chip 110, and the image sensor chip 110 may be bent using a difference in thermal expansion coefficient of each member constituting the image sensor chip 110.

  FIG. 3C is a schematic diagram of the layout of the image sensor chip 110 in plan view. In the figure, a central region R1 and a peripheral region R2 on the substrate are shown. As described above, the measurement unit 130 is disposed in the region R2. Since the region R2 is easily affected by the curvature of the image sensor chip 110, this configuration is advantageous for measuring the stress applied to the image sensor chip 110, and the measurement accuracy of the curvature of the image sensor chip 110 is improved. .

  In the region R2, in addition to the measurement unit 130, other units 131 (for example, other measurement units, at least a part of the setting unit 140, etc.) may be further arranged. The measurement unit 130 and the other unit 131 may be arranged in two corner regions that are diagonally related to each other as illustrated in FIG. 3C in plan view. They may be arranged side by side or may be arranged side by side along one side. Moreover, the measurement unit 130 may include two or more parts, and the two or more parts may be arranged at two or more positions different from each other.

FIG. 4 is a diagram for explaining an example of the measurement unit 130 and is a schematic diagram of a layout of the image sensor chip 110 in plan view. The measurement unit 130 includes, for example, pressure sensors 130 _{1 to} 130 ₄ . Each of the pressure sensors 130 _{1 to} 130 ₄ is a piezoresistive pressure sensor composed of a piezoresistive element. These four pressure sensors 130 _{1 to} 130 ₄ are arranged in the region R2 and correspond to the four sides forming the outer edge in the plan view of the substrate, respectively, and along the long side direction of the substrate in the plan view. It is formed in a line shape. In the case of a piezoresistive pressure sensor, a change in stress due to diaphragm deformation due to a pressure difference is detected as a change in the resistance value of the piezoresistive element and converted into a pressure. In this example, a stress change caused by the bending amount controlled by the bending control unit 120 is detected as a change in the resistance value of the piezoresistive element and converted into a bending amount. When the substrate is a semiconductor substrate such as a silicon substrate, the pressure sensors 130 _{1 to} 130 ₄ may be diffusion resistance elements formed by injecting impurities into the substrate. In another embodiment, each of the pressure sensors 130 _{1 to} 130 ₄ may be, for example, a piezoresistive element type pressure sensor formed on a diaphragm of a substrate.

As illustrated in FIGS. 5 (A) and (B), the pressure sensor ₁₃₀ 1 to 130 ₄ each being resistive element form a bridge circuit. In this example, the Wheatstone bridge circuit is used, but other bridge circuits such as a Wien bridge circuit, a Maxwell bridge circuit, and a snake side bridge circuit may be used.

For example, in the configuration of FIG. 5A, pressure sensors 130 ₁ and 130 ₂ are arranged in series on the first path between two nodes to which the voltage source V ₀ is connected. Pressure sensors 130 ₃ and 130 ₄ are arranged in series on the second path, which is the other path. Then, the node potential between the pressure sensor 130 ₁ and the pressure sensor 130 _2, the difference between the node potential between the pressure sensor 130 ₃ and the pressure sensor 130 ₄ is amplified through an amplifier A1, the voltage Output as V _OUT . The configuration of FIG. 5B is the same as the configuration of FIG. 5A except that the current source I ₀ is used instead of the voltage source V ₀ .

In such a circuit configuration, when the image sensor chip 110 is curved, the resistance values of the pressure sensors 130 _{1 to} 130 ₄ that are resistance elements change. Along with this, the node between the pressure sensor 130 ₁ and the pressure sensor 130 _2, the voltage _{V OUT} a potential difference is generated, corresponding to the potential difference between the node between the pressure sensor 130 ₃ and the pressure sensor 130 ₄ Is output. In other words, the curved state of the image sensor chip 110 is converted to the voltage _VOUT . The bending control unit 120 may control the bending state of the image sensor chip 110 based on the voltage _VOUT .

For example, the pressure sensor 130 _first resistance value when no stress is applied to the pressure sensor 130 ₁ and R, the variation of the pressure sensors 130 ₁ of the resistance value when the stress σ is applied to the pressure sensor 130 ₁ and ΔR Then, typically, (ΔR / R) ∝σ is established. When this relational expression is used, V _OUT σ is established for the output voltage V _OUT described with reference to FIGS. 5 (A) and 5 (B). Assuming that the image sensor chip 110 is uniformly curved, σ∝ (1 / r) is established when the radius of curvature is r. According to these equations, the voltage _VOUT and the radius of curvature r are inversely proportional. The control of the bending state by the bending control unit 120 may be performed based on the model exemplified above, but may be performed based on another model.

  Incidentally, as described above, according to Patent Document 2, shading analysis is performed on image data, and the curvature state of the image sensor chip is controlled based on the result. However, according to this method, when the image does not follow uniform light (for example, when a subject such as a person or a landscape is reflected in the image), it is difficult to analyze the shading itself, and the curved state There is a risk that the accuracy of the control will decrease.

  On the other hand, according to this configuration example, the measurement unit 130 does not need to use the image data read from the pixel array 111, measures the bending state of the image sensor chip 110 at a desired timing, and outputs the result. It is possible to feed back to the control of the bending state. In addition, the measurement unit 130 is disposed in the peripheral region R2 on the substrate, which is easily affected by the curvature of the image sensor chip 110. Therefore, according to the present configuration example, the bending state of the image sensor chip 110 can be appropriately measured by the measurement unit 130, which is advantageous in increasing the accuracy of the control of the bending state.

  Further, according to the method of Patent Document 2, the time required for the curved state to reach the target (or within the allowable range) is relatively long. For example, when the frame rate is 60 [fps], the time required to acquire image data for one frame is about 16.7 [msec]. Thereafter, shading analysis is performed, and the bending state is controlled based on the result. Actually, a series of operations including the acquisition of the image data, the shading analysis, and the control of the bending state may be repeated until the shading disappears. Then, it may take a considerable time (for example, 100 [msec] or more) for the curved state to reach the target.

  On the other hand, according to this configuration example, the measurement unit 130 does not need to perform shading analysis on the image data read from the pixel array 111, and measures the bending state of the image sensor chip 110 in a relatively short time. Can do. For example, according to the configuration examples of FIGS. 4 and 5, the time required for measurement of the bending state is 10 [μsec] or less, and the control is performed after starting the control of the bending state based on the measurement result. The time until completion is suppressed to 10 [msec] or less. Therefore, this configuration example is advantageous for speeding up the control of the bending state.

The measurement unit 130 is not limited to the configuration examples exemplified above, and may take other configurations. For example, FIG. 4 illustrates a configuration in which the pressure sensors 130 _{1 to} 130 ₄ are formed in a line shape along the long side direction. However, under other conditions, for example, the pressure sensors 130 ₁ and 130 ₄ are short. It may be formed in a line shape along the side direction. The other conditions include, for example, a case where the method of bending the image sensor chip 110, the direction of the bending, and the method of measuring the bending state are changed.

  In another embodiment, the measurement unit 130 may measure the bending state based on a change in the band gap caused by bending the image sensor chip 110. Specifically, when the image sensor chip 110 is bent, the crystal structure of the member constituting the substrate is distorted, so that the band gap of the member changes. Therefore, the measurement unit 130 can monitor the band gap and measure the state of bending based on the result.

  In another embodiment, the measurement unit 130 may measure the state of the curvature based on a change in the pixel signal from the optical black pixel that accompanies the curvature of the image sensor chip 110. Specifically, the plurality of pixels PX arranged in the pixel array 111 includes image pickup pixels arranged in the central portion and optical black pixels arranged in the peripheral portion thereof in the pixel array 111. The optical black pixel is provided with a light blocking member for blocking incident light, and the pixel signal read from the optical black pixel follows the amount of dark current (noise component) flowing through the substrate. Here, when the band gap is Eg, the Boltzmann constant is k, and the absolute temperature is T, the amount of the dark current is typically proportional to exp (−Eg / 2kT). Therefore, the measurement unit 130 can also monitor the pixel signal from the optical black pixel and measure the bending state based on the result.

  Note that since the value of the pixel signal read from a single optical black pixel is extremely small, a plurality of optical black pixels are arranged over one or more columns, one or more rows, or one or more columns and one or more rows. The signal values from these may be added. In addition, a dedicated unit for reading out the pixel signal from the optical black pixel and capable of operating at high speed with respect to the frame rate is provided separately from the driving unit 112, the reading unit 113, and the like. May be.

  In another embodiment, the measurement unit 130 may measure the bending state based on a change in capacitance that accompanies the bending of the image sensor chip 110. For example, a capacitance is formed between the image sensor chip 110 and another member (for example, a parallel plate-like conductive member arranged in parallel with the image sensor chip 110) located in the vicinity of the image sensor chip 110. The When the image sensor chip 110 is bent, the capacitance value changes. The measuring unit 130 can also measure the bending state of the image sensor chip 110 based on the change amount of the capacitance.

  FIGS. 6A and 6B are schematic views showing another configuration example for measuring the bending state of the image sensor chip 110. As illustrated in FIG. 6A, the imaging apparatus 100 includes a laser light irradiation unit 210 and a laser light detection unit 220 as the measurement unit 130 or instead of the measurement unit 130. The imaging apparatus 100 may further include a light reflecting unit 230 that reflects the laser light and is disposed on the image sensor chip 110. As illustrated in FIG. 6B, the light reflecting portion 230 may be disposed in the peripheral region R2 on the substrate in plan view, and may be disposed in a corner region thereof.

  The laser light irradiation unit 210 irradiates the image sensor chip 110 (the light reflection unit 230 thereof) with laser light. The laser light detection unit 220 detects the laser light reflected by the image sensor chip 110 (the light reflection unit 230 thereof). The curved state of the image sensor chip 110 is measured based on the detection position of the reflected laser beam in the laser beam detector 220. For example, when the image sensor chip 110 is not curved, the laser light is detected by the laser light detection unit 220 through a trajectory indicated by a broken line in the drawing. Further, when the image sensor chip 110 is bent, the laser light is detected by the laser light detection unit 220 through a trajectory indicated by a one-dot chain line in the drawing. That is, the detection position of the laser light in the laser light detection unit 220 varies depending on the curved state of the image sensor chip 110. Therefore, the bending state of the image sensor chip 110 can be measured based on the detection position.

(Other)
Although several preferred embodiments have been described above, the present invention is not limited to these embodiments, and some of the embodiments may be changed without departing from the spirit of the present invention. In addition, the names of the units used in the present specification are merely used to describe the corresponding functions, and the functions of the units are not limited to those described above. For example, the concept of the “imaging device” includes a device (for example, a personal computer or a portable terminal) having a photographing function as an auxiliary in addition to a device (for example, a camera) whose main purpose is photographing.

  100: imaging device, 110: image sensor chip, 120: bending control unit, 130: measurement unit, 140: setting unit.

Claims (15)

An imaging device including an image sensor chip having a pixel region in which a plurality of pixels are arranged,
A control unit that controls the state of curvature of the image sensor chip so that the pixel region is curved;
A measurement unit that is arranged in a peripheral region of the pixel region in the image sensor chip and measures a state of curvature of the image sensor chip;
A setting unit that sets a target of the curvature state of the image sensor chip based on the state of the optical lens used for photographing,
The control unit controls the bending state based on a result of comparing the measured bending state and the set target. The imaging apparatus according to claim 1, wherein when the state of the optical lens is changed, the setting unit updates the set target based on the state of the optical lens whose state has been changed. . The setting unit includes a memory that stores a reference table, and a selection unit that selects a parameter corresponding to the state of the optical lens with reference to the reference table,
The imaging apparatus according to claim 1, wherein the control unit controls the bending state based on the selected parameter. The imaging device according to any one of claims 1 to 3, wherein the setting unit sets the target of the curved state based on a model number of an optical lens attached to the imaging device. . The imaging apparatus according to any one of claims 1 to 4, wherein the setting unit sets a target of the curved state based on a position of the optical lens. The imaging device according to any one of claims 1 to 5, wherein the measurement unit includes a piezoresistive pressure sensor. The image sensor chip has a semiconductor substrate;
The imaging device according to claim 1, wherein the measurement unit includes a diffusion resistor formed on the semiconductor substrate. The measurement unit includes a plurality of sensors, and the plurality of sensors respectively correspond to a plurality of sides forming an outer edge of the image sensor chip in a plan view with respect to an upper surface of the image sensor chip. The imaging device according to any one of claims 1 to 7. In the plan view, the image sensor chip has a rectangular shape having a long side and a short side, and each of the plurality of sensors is formed in a line shape along the long side direction. The imaging apparatus according to claim 8, wherein the imaging apparatus is characterized. The imaging device according to claim 8 or 9, wherein each of the plurality of sensors is a resistance element, and the plurality of sensors form a bridge circuit. The measurement unit includes a plurality of other pixels that are different from the plurality of pixels and are arranged in the peripheral region,
Each of the plurality of pixels forms an imaging pixel;
6. The imaging apparatus according to claim 1, wherein each of the plurality of other pixels forms an optical black pixel. The said measurement part is monitoring the band gap of the member which comprises the said image sensor chip | tip, and measures the said curvature state based on the result of this monitoring. The imaging apparatus of Claim 1. An imaging device including an image sensor chip having a pixel region in which a plurality of pixels are arranged,
A control unit that controls the state of curvature of the image sensor chip so that the pixel region is curved;
A measuring unit for measuring the state of curvature of the image sensor chip;
A setting unit that sets a target of the curvature state of the image sensor chip based on the state of the optical lens used for photographing,
The measurement unit includes a laser light irradiation unit that irradiates the image sensor chip with laser light, and a laser light detection unit that detects the laser light reflected by the image sensor chip. Measure the curvature state of the image sensor chip based on the detection position of the laser light in the laser light detection unit,
The image sensor chip includes a substrate made of a semiconductor and a light reflection unit that reflects the laser beam from the laser beam irradiation unit, and the light reflection unit receives the image sensor chip with respect to the substrate. The control unit is provided on the side opposite to the light receiving surface of the image sensor chip with respect to the substrate,
The control unit controls the bending state based on a result of comparing the measured bending state and the set target. The image sensor chip further includes a peripheral region outside the pixel region,
The light reflecting portion imaging apparatus according to claim 13, characterized in that arranged in the peripheral region in the image sensor chip. The imaging device according to claim 13 or 14, wherein the light reflecting portion is arranged in a corner region of the image sensor chip in a plan view with respect to an upper surface of the image sensor chip.

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