JP2005227363A - Image pickup unit and light controlling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a light quantity of incident light come in a previously determined light controlling range so that a picked-up image having little visual field angle dependence is obtained without being affected by a shading phenomenon when the light quantity of the incident light is controlled by using a dichroic GH (Guest Host) liquid crystal. <P>SOLUTION: In an image pickup unit, application voltage for controlling electric light controlling elements 4 within the light controlling range on the basis of light quantity information obtained from a CCD (Charge Coupled Device) is supplied to the electric light controlling elements 4 provided between an optical system and the CCD and formed by mixing elements 33 having clockwise optical rotating power and elements 32 having counterclockwise optical rotating power in the ratio shown by a usable range 34 so as to come in the previously determined light controlling range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an imaging device and a light control device that perform light control of the amount of incident light.

  In recent years, there has been an increasing demand for high resolution and downsizing of imaging devices such as video cameras and digital still cameras. In response to this requirement, video cameras and digital still cameras are supported by mounting high-density CCDs (Charge Coupled Devices) or reducing the size of the lens. There arises a problem that the image quality deterioration phenomenon appears remarkably. In addition, the size limit of the movable part of the mechanical iris mounted on the lens unit is confronted with the problem of miniaturization. Thus, as a means for solving this problem, an idea of an electrically driven iris using a light control element made of an electrochemical material such as liquid crystal or EC (Electro Chromic) has been proposed (for example, Patent Document 1). reference).

  However, this electric drive iris has not been realized as a specific one only by an idea. One of the reasons is that the material suitable for application to the imaging device is insufficiently identified. This problem is caused by collecting all electrochemical materials such as liquid crystal and EC. In other words, despite the fact that the physical properties differ from material to material, the concept of making all materials common has many problems from the viewpoint of physical properties physics and electrochemistry.

For this reason, so-called two colors that obtain flat transmittance only at a specific wavelength corresponding to the dye by mixing the dye with the liquid crystal molecule and utilizing the property that the dye attaches to the liquid crystal molecule as the liquid crystal is driven. A liquid crystal using a GH (Guest Host) liquid crystal has been proposed (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 11-326894 JP 2001-201769

  However, since the dichroic GH liquid crystal has a viewing angle characteristic, when it is mounted in the lens unit of the image pickup apparatus, there is a problem that the received light intensity varies depending on the incident angle. For this reason, since the amount of light in the imaging screen becomes non-uniform and a shading phenomenon occurs, there is a disadvantage that the captured image becomes unnatural.

  Therefore, in the present invention, when dimming control of the amount of incident light using a dichroic GH liquid crystal is performed, a captured image with less viewing angle dependence is obtained without being affected by the above-described shading phenomenon. It is an object of the present invention to propose an imaging device and a light control device that make the amount of incident light within a predetermined light control range.

  In order to solve the above-mentioned problems and achieve the object of the present invention, the imaging apparatus of the present invention is provided between the optical system and the imaging means, and has left-handed rotation so as to be in a predetermined dimming control range. A dimming unit composed of an electric dimming element generated by mixing the one shown and the one showing right rotatory power, and the dimming unit is controlled within the dimming control range based on the light amount information obtained from the imaging unit Control means for supplying an applied voltage for the purpose.

  The light control means is composed of an electric light control element provided between the optical system and the imaging means. This electric light control element is generated by mixing a device that exhibits left-handed rotation and a device that exhibits right-handed rotation so as to be in a predetermined light control range. The control means supplies an applied voltage for controlling the dimming means within the dimming control range based on the light amount information obtained from the imaging means. The dimming means is driven so as to be within a predetermined dimming control range by the applied voltage supplied from the control means. This mixing ratio is set to a value having a low viewing angle dependency of the dichroic GH liquid crystal element of the light control means. The dimming control range corresponds to the required specifications.

  Further, the light control device of the present invention is provided between the optical system and the imaging means, and exhibits a left optical rotation and a right optical rotation so as to be in a predetermined light control range. It is composed of electric dimming elements generated by mixing, and is controlled within the dimming control range by the applied voltage supplied from the control means based on the light quantity information obtained from the imaging means.

  The light control device is composed of an electric light control element provided between the optical system and the imaging means. This electric light control element is generated by mixing a device that exhibits left-handed rotation and a device that exhibits right-handed rotation so as to be in a predetermined light control range. The control means supplies an applied voltage for controlling the dimming device within the dimming control range based on the light amount information obtained from the imaging means. The dimming device is driven so as to be within a predetermined dimming control range by the applied voltage supplied from the control means. This mixing ratio is set to a value having a low viewing angle dependency of the dichroic GH liquid crystal element of the light control means. The dimming control range corresponds to the required specifications.

  According to the present invention, the electric dimmer element is generated by mixing the left rotatory power and the right rotatory power so as to be in a predetermined dimming control range. When an applied voltage for controlling the dimming means to the dimming control range is supplied based on the light amount information obtained from the means, the dimming means becomes a predetermined dimming control range by the supplied applied voltage. By using the dichroic GH liquid crystal as the dimming means, the viewing angle dependence can be made without being affected by the shading phenomenon. A small number of captured images can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
FIG. 1 is a diagram illustrating an example of an optical system of an imaging apparatus incorporating an electric light control element. In FIG. 1, an electric light control element 4 which is a light control means used in the present embodiment is incorporated in a CCD camera which is an imaging device 1.

  That is, in the imaging apparatus 1, along the optical axis 10 indicated by the alternate long and short dash line, the lens group 2 and the lens group (for zooming) 3 corresponding to the front lens group, and the lens group 5 and the lens group (focus) corresponding to the rear lens group. 6) The CCD 8 having the image pickup surface 9 is arranged in this order at an appropriate interval. A filter 7 such as an infrared cut filter and an optical low-pass filter is disposed on the front surface of the CCD 8, and an image sensor is accommodated in the CCD 8.

  Between the lens group 3 and the lens group 5, the electric dimmer element 4 made of the above-mentioned dichroic GH liquid crystal is disposed. Although not shown, a polarizing plate for light amount adjustment (light amount diaphragm) is attached on the same optical path on the front surface of the electric light control element 4. The focusing lens group 6 is arranged so as to be movable between the lens group 5 and the CCD 8 along the optical path by a linear motor (not shown), and the zoom lens group 3 is arranged along the optical path. And an electric dimmer element are movably disposed.

  2A and 2B are diagrams illustrating a configuration example of the electric light control device, in which FIG. 2A is a cross-sectional view and FIG. 2B is a perspective view. FIG. 2 shows an example of a dichroic GH liquid crystal that is the electric light control element 4 shown in FIG. As shown in FIG. 2A, the electric light control element 21 is composed of a liquid crystal 22, and the front and rear surfaces of the liquid crystal 22 are sandwiched between glass plates 24 and 25 having high transmittance, respectively, and the periphery is shielded by other members. is there.

  As shown in FIG. 2B, the liquid crystal 22 of the electric dimmer 21 configured in this way can be arranged along the optical axis 10 shown in FIG. In the figure, the liquid crystal 22 is shown with a thickness, but is actually formed in a thin film shape.

  Further, an applied voltage V for driving the liquid crystal 22 from a control means (not shown) is supplied. The applied voltage V is set so that the liquid crystal 22 falls within a predetermined dimming control range. The liquid crystal 22 is generated by mixing a material that exhibits left-handed rotation and a device that exhibits right-handed rotation, which will be described later, so as to be in a predetermined dimming control range. The mixing ratio is set to a characteristic value having low viewing angle dependency of the liquid crystal 22.

Below, the left optical rotation and right optical rotation of a pigment | dye are demonstrated.
FIG. 7 is a diagram schematically showing the left optical rotation and right optical rotation of the pigment used in the dichroic GH liquid crystal. In general, when linearly polarized light passes through a substance, the property of rotating its vibration surface is known as optical rotation.

  In FIG. 7, the left-handed optically-rotating dye 71 has molecules 71-2, 71-3, 71-4, and 71-5 P, Q, and R counterclockwise as viewed from the light traveling direction with the nucleus 71-1. , S in this order. In addition, the dextrorotatory dye 72 has molecules 72-2, 72-3, 72-4, 72-5 in the clockwise direction as viewed from the light traveling direction centering on the nucleus 72-1, and P, Q, R, It is comprised so that it may rotate in order of S. The left rotatory dye 71 and the right rotatory dye 72 are in a symmetric relationship with respect to the virtual mirror 73, for example.

FIG. 8 is a diagram showing shading characteristics of a dichroic GH liquid crystal element composed only of a pigment having left-handed optical activity. FIG. 8 is an actual measurement using a single dichroic GH liquid crystal element composed only of a pigment having left-handed optical activity.
A dichroic GH liquid crystal containing a dichroic dye is a material in which the transmittance shown on the vertical axis increases or decreases depending on the applied voltage A (lowest) to G (highest). However, since it has viewing angle characteristics due to absorption anisotropy such as left-handed rotation and right-handed rotation of dichroic dye, the transmittance shown on the vertical axis depends on the incident angle of incident light shown on the horizontal axis. Has different so-called shading characteristics. A is no application, and G is the maximum applied voltage.

  From FIG. 8, the angle dependency of the transmittance decreases in the order of substantially applied voltages C, B, D, E, F, G, and A, although there is a slight difference between the left and right of the incident screen. Here, it can be seen that when the dichroic GH liquid crystal element is attached to the lens unit of the image pickup apparatus, it is preferable to attach it at a relatively small incident angle. However, under the recent demand for high resolution and downsizing of image pickup devices, the image pickup devices must be mounted at a relatively large incident angle. Therefore, particularly in current image pickup devices, the image pickup device is mounted at a maximum incident angle of 25 °. It is demanded.

FIG. 9 is a diagram showing the shading characteristics of a dichroic GH liquid crystal element composed only of a right-rotating pigment. FIG. 9 is an actual measurement using a single dichroic GH liquid crystal element composed only of a dye having right rotatory power.
Here again, it can be seen that the transmittance increases or decreases depending on the applied voltages A (lowest) to G (highest). Similarly, A is no application, and G is the maximum applied voltage. From FIG. 9, it can be confirmed that this characteristic is symmetric with respect to FIG. 8 with respect to the center of the vertical axis.

  In normal cases, it is known that there is no problem in use if the shading standard of the imaging apparatus is within 1 ± 0.15 with respect to the central portion indicated by the transmittance on the vertical axis in FIGS. This is because a shading correction function is mounted in the imaging apparatus, and if it is within the above-mentioned standard, it can be handled by the shading correction function.

  However, the conditions for mounting the dichroic GH liquid crystal element on the lens unit of the imaging apparatus are severe, and the areas of applied voltages C, B, D, and E in FIGS. 8 and 9 described above do not satisfy the shading standard. For this reason, it is impossible to satisfy the specifications of an imaging apparatus that requires stable imaging. Therefore, a dimming control range required by generating a dichroic GH liquid crystal element by mixing a left rotatory light and a right rotatory light so that a predetermined dimming control range is obtained. Need to expand.

  Therefore, in the embodiment of the present invention, the ratio of the mixture of the left rotatory and the right rotatory of the dye of the dichroic GH liquid crystal element is set to a characteristic with low dependence on the viewing angle of the liquid crystal. By setting it to a value, a captured image that eliminates the influence of shading is obtained.

FIG. 3 is a diagram showing the weight ratio of the dye in the dichroic GH liquid crystal of the electric light control element.
As shown in FIG. 3, the first condition of the usable range 34 is that the mixture of the chromophoric GH liquid crystal element 31 indicated by the left-handed optical rotation 32 and the right-handed rotatory rotation 33 is mixed. The weight ratio (%) is 50:50. This first condition is a so-called racemic mixture in which the composition of the dichroic dye contained in the dichroic GH liquid crystal is mixed with an equivalence of a mixture of those showing left-handed rotation and those showing right-handed rotation in weight ratios. By adopting a structure, the absorption anisotropy of the dye is eliminated.

FIG. 4 is a diagram showing shading characteristics of a dichroic GH liquid crystal element composed of a racemic dye. As shown in FIG. 4, the transmittance does not increase or decrease depending on the applied voltages A (lowest) to G (highest), and the same characteristics as A from no application of A to the maximum applied voltage of G. . In this case, all the applied voltages A (lowest) to G (highest) regions satisfy the shading standard described above.

  Further, the second condition of the usable range 34 is that the weight ratio (%) of the mixture of the chromophoric GH liquid crystal element indicated by 31 with the left rotatory rotation 32 and the right rotatory rotation 33 is shown. Is 80:20. This second condition is that the composition of the dichroic dye contained in the dichroic GH liquid crystal is mixed with the one showing the left optical rotation and the one showing the right optical rotation at a weight ratio of 80:20. The absorption anisotropy of the dye is reduced.

  FIG. 5 is a diagram showing the shading characteristics of a dichroic GH liquid crystal element having a dye composition in which the weight ratio of the weight of a left-rotating dye to the right-rotating dye is 80:20. In this case, on the right side of the screen on the horizontal axis, the above-described shading standard is satisfied in all the applied voltages A (lowest) to G (highest) regions. On the other hand, on the left side of the screen, only the areas of applied voltages A, E, F, and G satisfy the shading standard described above.

  Further, the fourth condition of the usable range 34 is that the weight ratio (%) of the mixture of the chromophoric GH liquid crystal element indicated by 31 with the left rotatory rotation 32 and the right rotatory rotation 33 is shown. Is 20 to 80. In the fourth condition, as in the second condition, the dichroic dye contained in the dichroic GH liquid crystal has a weight ratio of 20 which shows left-handed rotation and right-handed rotation. By mixing with the pair 80, the absorption anisotropy of the dye is reduced.

  FIG. 6 is a diagram showing the shading characteristics of a dichroic GH liquid crystal element having a dye composition in which the weight ratio of the weight of the left rotatory dye to the right rotatory dye is 20:80. In this case, on the left side of the screen on the horizontal axis, all the applied voltages A (lowest) to G (highest) satisfy the above-described shading standard. On the other hand, on the right side of the screen, only the areas of applied voltages A, E, F, and G satisfy the shading standard described above.

  Therefore, since the third condition of the usable range 34 is between the second condition and the fourth condition, the above-described shading standard is satisfied. The third condition of the usable range 34 is that the weight ratio (%) of the mixture of the dichroic GH liquid crystal element indicated by 31 with the left rotatory power 32 and the right rotatory power 33 is 80. The ratio is between 20-20: 80. This second condition is that the composition of the dichroic dye contained in the dichroic GH liquid crystal has a left optical rotation and a right optical rotation with a weight ratio of 80:20 to 20:80. The absorption anisotropy of the dye is reduced by mixing at a ratio of between. In this case, the third condition is obtained by removing the first condition from the ratio in the above-described range.

  As described above, the mixing ratio between the one showing the left optical rotation and the one showing the right optical rotation of the dye of the dichroic GH liquid crystal element is set under the first to fourth conditions in the usable range 34. Thus, it is possible to obtain a captured image that eliminates the influence of shading.

The operation of the dimming control of the electric dimming element configured under the first condition to the fourth condition in the usable range 34 shown in FIG. 3 will be described below.
First, the CPU 11 shown in FIG. 2 controls the dimming GH liquid crystal 22 constituting the electric dimming element 21 provided between the optical system as shown in FIG. The applied voltage V for driving to be in the control range is set for each of the first condition to the fourth condition in the usable range 34 shown in FIG. This dimming control range is a value corresponding to the required specification. The value of the applied voltage V corresponding to the dimming control range set by the CPU 11 is stored in the memory in correspondence with the first to fourth conditions of the usable range 34 shown in FIG. The Such a setting operation may be performed, for example, at an adjustment stage in the manufacturing process of the imaging apparatus 1 or may be performed when the power is turned on.

  Next, light amount data D obtained from the CCD 8 is supplied to the CPU 11 during various adjustments in which focus control or the like is performed during photographing by the imaging device 1. Based on the light amount data D, the CPU 11 reads out the value of the applied voltage V from the value stored in the memory so that the electric dimming element 21 falls within an appropriate dimming control range.

  The CPU controls the applied voltage V set in the memory in correspondence with the first condition to the fourth condition of the usable range 34 shown in FIG. 3 in order to control the electric dimming element 21 to the dimming control range. It controls to read and supply to the electric light control element 21. FIG.

  With the applied voltage V read out by the CPU 11, the electric dimmer 21 configured by the first condition to the fourth condition in the usable range 34 shown in FIG. 3 is set to an appropriate dimming control range. Dimming control is performed. The applied voltage V is set to a value having a low viewing angle dependency of the dichroic GH liquid crystal element of the electric dimmer 21 and is stored in the memory in advance.

  Further, in the above-described example, the ratio of the mixture of the pigment of the dichroic GH liquid crystal element, which is the electrochromic device 21, that shows the left optical rotation and the one that shows the right optical rotation, can be used as shown in FIG. Although only the first condition to the fourth condition of the range 34 are shown, the present invention is not limited to this, and the electric dimming element has an arbitrary ratio within the range of the third condition described above according to the required dimming control range. In this case, for each dichroic GH liquid crystal element, the value of the applied voltage V may be set so that the dimming control range for obtaining the optimum transmittance is obtained.

It is a figure which shows the example of an optical system of the imaging device incorporating an electric light control element. It is a figure which shows the structural example of an electric light control element, FIG. 2A is sectional drawing, FIG. 2B is a perspective view. It is a figure which shows the weight ratio of the pigment | dye in the dichroic GH liquid crystal of an electric light control element. It is a figure which shows the shading characteristic of the dichroic GH liquid crystal element comprised with the pigment | dye of a racemic structure. It is a figure which shows the shading characteristic of the dichroic GH liquid crystal element used as the pigment | dye structure whose weight ratio of the pigment | dye which has a left optical rotation and the pigment | dye which has a right optical rotation is 80:20. It is a figure which shows the shading characteristic of the dichroic GH liquid crystal element used as the pigment | dye composition whose weight ratio of the pigment | dye which has a left optical rotation and the pigment | dye which has a right optical rotation is 20:80. It is a figure which shows the left rotatory power and right rotatory power of the pigment | dye used for a dichroic GH liquid crystal. It is a figure which shows the shading characteristic of the dichroic GH liquid crystal element comprised only with the pigment | dye which has a left optical rotation. It is a figure which shows the shading characteristic of the dichroic GH liquid crystal element comprised only with the pigment | dye which has a right rotatory power.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Imaging device 2, 3, 5, 6 ... Lens group, 4 ... Electric light control element, 7 ... Filter, 8 ... CCD, 9 ... Imaging surface, 10 ... Optical axis, 21 ... Electric light control element, 22 ... Liquid crystal, 24, 25 ... Glass plate, 31 ... Dye weight ratio of dichroic GH liquid crystal element, 32 ... Left rotation, 33 ... Right rotation, 34 ... Usable range

Claims (10)

In an imaging device for imaging a subject using an imaging means via an optical system,
An electrical control provided between the optical system and the imaging means and generated by mixing a left optical rotation and a right optical rotation so that a predetermined dimming control range is obtained. A light control means comprising an optical element;
An imaging apparatus comprising: control means for supplying an applied voltage for controlling the dimming means within the dimming control range based on light amount information obtained from the imaging means. The imaging device according to claim 1,
An image pickup apparatus, wherein the electrochromic device is a dichroic GH liquid crystal device. The imaging device according to claim 2,
An image pickup apparatus, wherein the mixing ratio is set to a characteristic value having low viewing angle dependency of the dichroic GH liquid crystal element. The imaging device according to claim 1,
An image pickup apparatus, wherein the mixing ratio is 50:50. The imaging device according to claim 1,
The above-mentioned mixing ratio is a ratio between 80:20 and 20:80 excluding 50:50. In a light control device used in an imaging device that images an object using an imaging means via an optical system,
An electrical control provided between the optical system and the imaging means and generated by mixing a left optical rotation and a right optical rotation so that a predetermined dimming control range is obtained. It consists of optical elements,
A dimming device, wherein the dimming control range is controlled by an applied voltage supplied from a control unit based on light amount information obtained from the imaging unit. The light control device according to claim 6,
The light control device is characterized in that the electric light control device is a dichroic GH liquid crystal device. In the light modulation apparatus of Claim 7,
The light control device according to claim 1, wherein the mixing ratio is set to a characteristic value having low viewing angle dependency of the dichroic GH liquid crystal element. The light control device according to claim 6,
A dimmer characterized in that the mixing ratio is 50:50. The light control device according to claim 6,
The dimming device according to claim 1, wherein the mixing ratio is a ratio between 80:20 and 20:80 excluding 50:50.

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