Imaging device

Abstract

To provide an imaging device that includes a neutral density filter containing a gradation in which light transmittance changes continuously in a movable direction, and is capable of appropriately correcting white balance.SOLUTION: An imaging device includes a neutral density filter, at least one imaging element for receiving light that has passed through the neutral density filter and reduced in amount of light and converting the light into an electrical signal, a movable position detector for detecting a dimming state by detecting the movable position of the neutral density filter, an image processor to which the electrical signal and a detection result of the movable position detector are input, and a memory unit, and attenuation information indicating a unique correlation between the light transmittance of the neutral density filter or the same type of the neutral density filter, and the wavelength of the light is obtained in advance. The attenuation information is stored in the memory unit, and the image processor performs white balance correction based on the detection result by the movable position detector and the attenuation information when image data or an image signal is generated based on the electrical signal.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an imaging device that performs white balance correction and is provided with a neutral density filter that includes a gradation in which the light transmittance changes continuously in the direction of movement of the filter. [Background technology]

[0002] An imaging device is known which includes a variable light transmission filter (neutral reduction filter) which changes the light transmittance depending on the applied voltage, an imaging element which takes in the light which has been transmitted through the variable light transmission filter and has a reduced amount of light and converts it into an electrical signal, a transmittance monitor (detection unit) which monitors the transmittance of the variable light transmission filter, and an image processing unit which receives the electrical signal and the detection results of the detection unit, and in which the image processing unit performs white balance correction based on information on the correlation between the wavelength of light and the transmittance in the variable light transmission filter and the detection results by the transmittance monitor when generating image data or an image signal based on the electrical signal (see, for example, Patent Document 1).

[0003] According to the imaging device of the above document, the amount of light can be finely adjusted by the variable light-transmitting filter, so that it is possible to obtain image data or image signals according to the brightness of the shooting location, and the image generated from light that has passed through the variable light-transmitting filter and has lost its white balance can be optimized by white balance correction.

[0004] Incidentally, the above-mentioned document also describes an imaging device that uses a gradation ND filter (neutral density filter) that is movably supported and includes a gradation in which the light transmittance changes continuously in the moving direction, making it unnecessary to monitor the transmittance using a transmittance monitor. However, the document does not describe the specific processing content of the white balance correction for the imaging device that uses the gradation ND filter.

[0005] Incidentally, the mechanisms for changing the transmittance of a variable light transmittance filter, which changes the light transmittance depending on the applied voltage, and a gradient ND filter, in which a gradation is formed in the direction of movement, are significantly different. Also, the change in shade of a gradient ND filter is often not uniform. As a result, even if the processing contents for white balance correction when a variable light transmittance filter is used are directly applied to the processing contents for white balance correction when a gradient ND filter is used, it may be difficult to achieve appropriate processing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5557962 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide an imaging device that includes a neutral density filter that includes a gradation in which the light transmittance changes continuously in the direction of movement, and that is capable of appropriately correcting white balance. [Means for solving the problem]

[0008] In order to solve the above problem, the present invention provides an image forming apparatus comprising at least one dimming filter that is supported movably and includes a gradation in which the light transmittance changes continuously in the movable direction, at least one image sensor that captures light that has passed through the dimming filter and has a reduced amount of light and converts it into an electrical signal, a movable position detection unit that detects a dimming state by detecting the movable position of the dimming filter, an image processing unit to which the electrical signal and the detection result of the movable position detection unit are input, and a memory unit, wherein attenuation information, which is a unique correlation between the light transmittance of the dimming filter or a dimming filter of the same type as the dimming filter, and the wavelength of light, is determined in advance, the related information is stored in the memory unit, and the image processing unit is configured to perform white balance correction based on the electrical signal, the detection result by the movable position detection unit, and the attenuation information when generating image data or an image signal based on the electrical signal.

[0009] The image sensor may further include a spectrometer that separates the light that has passed through the neutral density filter and has a reduced amount of light into three or more component colors that make up the image data or image signal by dividing the light into predetermined wavelength ranges, and the imaging element may be provided specifically for each of the multiple component colors, and color attenuation information, which is information on a unique correlation between the movable position of the neutral density filter or a neutral density filter of the same type as the neutral density filter and the transmittance of light in the wavelength range related to the component colors, may be obtained in advance for each of the multiple component colors, and the attenuation information may include multiple pieces of color attenuation information.

[0010] The image processing unit may be configured to perform the white balance correction process by correcting the electrical signal output from each of the imaging elements provided for each of the plurality of correction component colors, or the image signal or each correction component color constituting the image data, based on the difference between the color attenuation information relating to the reference component color, which is one of the predetermined component colors, and the color attenuation information for each of the correction component colors, which are the other plurality of component colors.

[0011] The invention may be configured such that, for each of a plurality of set points set at predetermined intervals within the movable range of the neutral density filter, point attenuation information, which is information on the unique correlation between the light transmittance and wavelength in the neutral density filter or a neutral density filter of the same type as the neutral density filter, is determined in advance, the attenuation information includes point attenuation information for each set point, and the image processing unit performs the white balance correction process by correcting the electrical signal output from the imaging element or by correcting an image signal or image data based on the point attenuation information for the set point corresponding to the movable position detected by the movable position detection unit.

[0012] The white balance correction may be performed by determining in advance for each set point a set transmittance which is the light transmittance corresponding to the movable position thereof, and the attenuation information includes information on the set transmittance of each set point, and the image processing unit is configured to perform the white balance correction process by correcting the electrical signal output from the imaging element or by correcting an image signal or image data based on the difference between the light transmittance of the point attenuation information relating to the set point corresponding to the movable position detected by the movable position detection unit and the set transmittance of the set point.

[0013] The optical fiber may further include a movable mechanism that supports the neutral density filter so that the neutral density filter rotates or pivots about a linear axis that is parallel to the direction in which light passes, and the gradation may be configured to change continuously in a direction around the axis.

[0014] The two dimming filters are supported by the movable mechanism so as to rotate or pivot about the same axis as a fulcrum and are shaped into the same circle, and are arranged side by side in the direction of the axis, and a part of the range in which the two gradations always overlap within the movable range of the dimming filters as viewed in the direction of the axis is a transmission range through which light reaching the imaging element is transmitted, the movable mechanism is configured to rotate or pivot the two dimming filters in opposite directions by the same amount of movement, and the two dimming filters are configured so that the shading of each of the gradations is in opposite phase with respect to the transmission range as viewed in the direction of the axis, and the combined transmittance of light is made uniform in the transmission range.

[0015] The optical system may further include a movable mechanism that supports the neutral density filter so that the neutral density filter is slidable in a straight line, and the gradation may be configured to change continuously in the sliding direction of the neutral density filter.

[0016] The neutral density filters may be arranged in a pair side by side in the direction of transmitting light, and a part of the range in which the two gradations always overlap within the movable range of the neutral density filters when viewed in the direction of transmitting light is a transmission range through which light reaching the imaging element passes, and the movable mechanism may be configured to slide the two neutral density filters in different directions with the same amount of movement.

[0017] The movable mechanism may be configured to slide the two dimming filters in opposite directions with the same amount of movement, and the two dimming filters may be configured so that the gradation shades of each filter change symmetrically with respect to the transmission range when viewed in the direction through which light is transmitted, and so that the combined light transmittance of the two dimming filters is uniform within the transmission range.

[0018] A plurality of pairs of the neutral density filters may be provided, each pair being arranged in the light transmitting direction.

[0019] The dimming filters may be arranged in a switching direction that is a direction intersecting the sliding direction when viewed in the direction that transmits light, and the dimming filters arranged in the switching direction may have gradations of different patterns, and the movable mechanism may be configured to slide each of the dimming filters arranged in the switching direction in the switching direction so that the dimming filters that transmit light can be switched.

[0020] The neutral density filter may be constructed from a flexibly deformable film, and may be fitted around a number of rotating rollers so as to describe a circular track, so that when viewed in a direction that transmits light reaching the imaging element, the overlapping portions of the films are positioned within a passing range through which the light passes, and the film is configured so that the light transmittance changes as the portions of the film positioned within the passing range are changed by the rotation of the rollers. Effect of the Invention

[0021] Attenuation information, which is the inherent correlation between the light transmittance and the wavelength of light in a neutral density filter including a gradation in which the light transmittance changes continuously in the direction of movement or in a neutral density filter of the same type, is obtained in advance, and white balance correction is performed using this inherent attenuation information, so that it is possible to appropriately perform white balance correction even on images generated based on light that has passed through neutral density filters in which the changes in shading are rarely uniform. [Brief description of the drawings]

[0022] [Figure 1] 1 is a side cross-sectional view showing a configuration of a main part of an imaging device to which the present invention is applied. [Diagram 2] 1A and 1B are front views showing the configurations of two gradation ND filters. [Diagram 3] 2 is a block diagram showing a configuration of the imaging device shown in FIG. 1. [Figure 4] 4 is a flowchart showing a procedure until an image processing unit generates image data or an image signal. FIG. [Diagram 5] 11 is a characteristic graph showing an example of color attenuation information. [Figure 6] 11 is a characteristic graph showing an example of point attenuation information. [Figure 7] 13A and 13B are a plan view and a front view of a neutral density filter according to another embodiment of the present invention. [Figure 8] FIG. 13 is a plan view of a neutral density filter according to another embodiment. [Figure 9] FIG. 13 is a front view of a neutral density filter according to another embodiment. [Figure 10] FIG. 13 is a plan view of a neutral density filter according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Fig. 1 is a side cross-sectional view of a main part showing the configuration of an imaging device to which the invention is applied, Fig. 2(A) and (B) are front views showing the configurations of two gradation ND filters, and Fig. 3 is a block diagram showing the configuration of the imaging device shown in Fig. 1. The imaging device 1 comprises a main body 2, an interchangeable lens device 3, and a filter device 4 interposed between the main body 2 and the interchangeable lens device 3.

[0024] Here, the direction from the imaging device 1 toward the subject B is defined as the forward direction, and front / back, left / right, and up / down are defined based on this. A filter device 4 is disposed in front of the imaging device body 2, and an interchangeable lens device 3 is disposed in front of the filter device 4.

[0025] The filter device 4 is detachably attached and fixed to the main body 2. The interchangeable lens device 3 is selectively detachably attached and fixed to either the filter device 4 or the main body 2. In other words, the imaging device 1 can be switched to a mode in which the filter device 4 is omitted and the interchangeable lens device 3 is directly attached to the main body 2.

[0026] Light from subject B is first introduced into the interchangeable lens device 3. The light introduced into the inside of the interchangeable lens device 3 is appropriately enlarged or reduced by passing through one or more lenses (not shown) arranged inside, and is then introduced into the inside of the filter device 4 (inside the housing 6). The light introduced into the inside of the filter device 4 (inside the housing 6) passes through a plurality of neutral density filters 7, 8 arranged inside the housing 6, whereby the amount of light is reduced (dimmed), and then the light is introduced into the inside of the main body 2.

[0027] The light introduced into the main body 2 is separated (dispersed) into three or more component colors (in this example, the three primary colors of light: red (R), green (G), and blue (B)) by dividing it into predetermined wavelength ranges using a color separation prism (spectroscope) 9. Each of the lights relating to the multiple component colors is irradiated onto imaging elements 11R, 11G, and 11B, such as CCDs, that are provided exclusively for each of the component colors, and converted into an electrical signal.

[0028] The main body 2 is equipped with an image processing unit 12 including a microcomputer, etc. The image processing unit 12 generates image data or an image signal corresponding to the subject B based on electrical signals sent from each of the multiple image pickup elements 11R, 11G, and 11B.

[0029] Incidentally, in this example, light from subject B passes through the axis of the cylindrically formed interchangeable lens device 3 and travels in a straight line until it reaches the color separation prism 9. Thereafter, each of the lights that is irradiated to the color separation prism 9 and separated into a plurality of component colors changes its direction and is irradiated to the corresponding image pickup elements 11R, 11G, 11B.

[0030] That is, the optical axis X of the light traveling between the subject B and the color separation prism 9 is coaxial with the cylindrical shape of the interchangeable lens device 3 and is a straight line that is the shortest path in the space between them. The optical axes LR, LG, and LB of the light traveling between the color separation prism 9 and each of the multiple image pickup elements 11R, 11G, and 11B change direction from the above-mentioned optical axis X and become a straight line that is the shortest path in the space between them.

[0031] 1, the space around the optical axis X defines an optical path R, which is the range through which light (hereinafter referred to as "image light") reaches the imaging elements 11R, 11G, and 11B passes. The spaces around the optical axes LR, LG, and LB also define optical paths (not shown) which are the range through which the image light passes. These optical paths R are formed in a circular shape when viewed in the axial direction of the optical axes X, LR, LG, and LB.

[0032] Next, the configuration of the filter device 4 will be described with reference to FIGS.

[0033] As shown in Figures 1 and 3, the filter device 4 includes the housing 6, the neutral density filters 7, 8 arranged inside the housing 6, a movable mechanism 13 arranged inside the housing 6 and supporting the neutral density filters 7, 8 movably together, and a filter side control unit 14 arranged inside the housing 6 and composed of a microcomputer or the like.

[0034] Through holes 6a, 6b through which image light passes are formed in a wall portion (specifically, a front wall portion) of the housing 6 that is closer to the subject B and a wall portion (specifically, a rear wall portion) that is farther from the subject B, respectively. Each of the two through holes 6a, 6b forms a circle centered on the optical axis X when viewed in the axial direction of the optical axis X, and has a diameter equal to or slightly larger than the optical path R so as to cover the entire range of the optical path R when viewed in the axial direction of the optical axis X. The image light introduced into the filter device 4 from one through hole 6a is led out from the other through hole 6b and introduced into the inside of the main body 2.

[0035] The two neutral density filters 7, 8 are supported on the housing 6 side so as to be rotatable or pivotable about an axis 16 that is offset from the optical axis X by a predetermined amount and is parallel to the optical axis X. Incidentally, in the illustrated example, the axis 16 is a physical support axis that constitutes part of the movable mechanism 13 and supports each of the two neutral density filters 7, 8 in an freely rotating state. However, it is of course also possible to support each of the neutral density filters 7, 8 individually so as to be rotatable or pivotable by rollers or the like, and to configure this axis 16 as a virtual straight line.

[0036] The two neutral density filters 7, 8 have the same circular shape when viewed in the axial direction of the optical axis X (in other words, when viewed in the direction that transmits image light, or when viewed in the direction of the axis 16), and are formed into a plate shape having a thickness in the direction of the axis 16. Since the axis 16 passes through the centers of the neutral density filters 7, 8, the two neutral density filters 7, 8 completely overlap when viewed in the axial direction of the axis 16.

[0037] Each of the neutral density filters 7, 8 has a base material 7a, 8a made of a transparent circular glass plate or resin plate, and an optical film 7b, 8b provided on one side, both sides, or inside the base material 7a, 8a by printing a black pigment (e.g., carbon black) with a printer such as an inkjet printer. The optical films 7b, 8b have a gradation formed in which the light transmittance (shade) changes continuously in the movable direction of the neutral density filters 7, 8 (specifically, the direction around the axis 16 when viewed in the axial direction of the axis 16, hereinafter simply referred to as the "circumferential direction").

[0038] The gradation is formed in an annular shape over the entire circumferential direction of each of the neutral density filters 7, 8, with the start and end thereof being adjacent to each other in the circumferential direction, causing the neutral density filters 7, 8 to function as gradation ND filters.

[0039] The gradation of the optical films 7b, 8b is set so that the optical density of each of the neutral density filters 7, 8 decreases monotonically and proportionally from the start end to the end end in the circumferential direction. In other words, the optical density of each of the neutral density filters 7, 8 increases monotonically and proportionally from the start end to the end end in the circumferential direction. The light transmittance of the start end of the neutral density filters 7, 8 in the circumferential direction is set to 100% (optical density is the minimum, 0), and the light transmittance of the end end is set to the minimum (optical density is the maximum). For example, if the minimum light transmittance of each neutral density filter is 1 / 16, the maximum light transmittance of the entire filter device 4 is 1 / 256.

[0040] The pair of front and rear neutral density filters 7, 8 are configured as described above so that the entire range in the circumferential direction in which the gradation is formed completely coincides with and overlaps with each other when viewed in the axial direction of the optical axis X. The optical path R is arranged in a state in which it is entirely contained within a partial range of the circular ring-shaped gradation (optical films 7b, 8b) when viewed in the axial direction of the optical axis X. In other words, this partial range becomes the transmission range E of the neutral density filters 7, 8 through which light passes.

[0041] Therefore, during shooting, subject B, the cylindrical axis of interchangeable lens device 3, the circular center of transmission range E, and color separation prism 9 are aligned in a straight line on optical axis X.

[0042] The pair of front and rear darkening filters 7, 8 are configured so that, when viewed in the axial direction of the optical axis X, the changes in the shading of the gradation of the optical films 7b, 8b are in opposite phase to each other with the transmission range E as the reference. The pair of front and rear darkening filters 7, 8 have gradations that are in opposite phase with the transmission range E as the reference, and the total optical density is made uniform in the transmission range E. In other words, the total value of the light transmittance of the pair of front and rear darkening filters 7, 8 (i.e., the light transmittance of the filter device 4) is made uniform throughout the entire transmission range E.

[0043] To explain the opposite phases in more detail, the shading of the gradation of the pair of front and rear neutral density filters 7, 8 changes at the same rate in one direction and the other direction in the circumferential direction, with the center of the transmission range E as the boundary. Correspondingly, the movable mechanism 13 is configured to use a gear mechanism or the like to rotate or turn the pair of neutral density filters 7, 8 by the same amount in opposite directions in the circumferential direction.

[0044] With this configuration, each of the pair of neutral density filters 7, 8 is rotated or turned by the same amount in opposite directions, and the optical density (amount of transmitted light) in the transmission range E realized by the pair of neutral density filters 7, 8 is changed while maintaining a uniform state over the entire range. Therefore, the reduction rate of the amount of image light transmitted through the two neutral density filters 7, 8 is uniform over the entire range, and the occurrence of a gap is suppressed.

[0045] Connected to the input side of the filter side control unit 14 are a movable position detection unit 17 such as a potentiometer or a rotation sensor that detects the movable positions (specifically, the rotation or pivot positions) of the pair of neutral density filters 7, 8, and a setting operation tool 18 that sets the optical density of the filter device 4. Connected to the output side of the filter side control unit 14 is an actuator 19 such as an electric motor that constitutes part of the movable mechanism 13 and drives the pair of neutral density filters 7, 8 to rotate or pivot in opposite circumferential directions. The filter side control unit 14 is also configured to be able to send and receive information to and from the image processing unit 12.

[0046] The filter side control unit 14 rotates or rotates each of the pair of neutral density filters 7, 8 in the relative direction by the movable mechanism 13 including the actuator 19 so that the amount of light transmission (i.e., the dimming state) achieved by the two neutral density filters 7, 8 in the transmission range E becomes the value set by the setting operation tool 18. The movable positions of the neutral density filters 7, 8 at this time are detected by the movable position detection unit 17. That is, the movable position detection unit 17 is configured to detect the light transmittance (i.e., the dimming state) of the neutral density filters 7, 8.

[0047] Next, the configuration of the main body 2 will be described with reference to FIGS.

[0048] The main body 2 has a housing 20 having an intake hole 20a drilled in the wall (front wall) on the filter device 4 side for intake of image light from the filter device 4, the above-mentioned color separation prism 9 arranged inside the housing 20, the above-mentioned multiple image pickup elements 11R, 11G, 11B arranged inside the housing 20, the above-mentioned image processing unit 12 arranged inside the housing 20, an external storage medium (storage unit) 21 that stores image data generated by the image processing unit 12, and an output unit 22 such as a terminal that outputs the image signal generated by the image processing unit 12 to a monitor mounted on the imaging device 1 or an external monitor, etc.

[0049] A storage unit 12a is installed in the image processing unit 12. The image processing unit 12 may store image data generated by itself in the storage unit 12a.

[0050] Incidentally, the optical density or light transmittance of the filter device 4 set by the setting operation tool 18 is not uniform over the entire range of light wavelengths, but rather has a bias depending on the wavelength region. Due to this bias, the white balance (balance of color tones) of the light that has passed through the pair of neutral density filters 7, 8 of the filter device 4 is lost compared to the light before passing through, resulting in a problem of image degradation. To correct this, the image processing unit 12 performs a correction process to correct the white balance (white balance correction) before performing a generation process to generate image data or an image signal.

[0051] In performing this white balance correction, first, for the neutral density filters 7, 8 (in this example, a pair of neutral density filters 7, 8) or the same type of neutral density filter (a neutral density filter having the same or approximately the same shading pattern), information on the inherent correlation between the transmittance of the image light (specifically, the transmittance of the light that has passed through the transmission range E of the pair of neutral density filters 7, 8) and the wavelength of the image light (attenuation information) is obtained in advance, and the information is stored in the memory unit 12a or the external storage medium 21.

[0052] When the correction process is executed, white balance correction is performed based on the attenuation state of the neutral density filters 7 and 8 at that time point detected by the movable position detection unit 17 and the attenuation information described above.

[0053] 4 is a flow diagram showing the procedure until the image processing unit generates image data or an image signal. When the image processing unit 12 detects an electrical signal from the imaging elements 11R, 11G, and 11B, the image processing unit 12 starts processing from step S1. In step S1, an electrical signal acquisition process is executed to acquire an electrical signal from each of the multiple imaging elements 11R, 11G, and 11B, and the process proceeds to step S2.

[0054] In step S2, a movable position acquisition process is executed to acquire the detection result (the movable positions of the pair of neutral density filters 7, 8) of the movable position detection unit 17 at that time from the filter side control unit 14, and the process proceeds to step S3.

[0055] In step S3, a correction process, which is the above-mentioned white balance correction process, is performed based on the movable positions of the pair of neutral density filters 7, 8 acquired by the movable position acquisition process and the inherent attenuation information of the pair of neutral density filters 7, 8 or the same type of neutral density filters 7, 8 acquired from the storage unit 12a or the external storage medium 21, and then the process proceeds to step S4. Incidentally, the white balance correction in this example is performed on the electrical signals acquired from each of the multiple image pickup elements 11R, 11G, 11B.

[0056] In step S4, a generation process is executed to generate image data or an image signal based on a plurality of electrical signals whose white balance has been adjusted by the correction process, and the process proceeds to step S5.

[0057] In step S5, the image data generated by the generation process is output to the memory unit 12a or the external storage medium 21 for storage, or an output process is executed in which the image signal generated by the generation process is output from the output unit 22 to the outside and displayed on a monitor screen, thereby completing the series of processes.

[0058] In the illustrated example, the generation process is performed after the correction process, but this order may be reversed. In this case, white balance correction is performed on each of the correction component colors that make up the image signal or image data generated by the generation process.

[0059] 5 is a characteristic graph showing an example of color attenuation information. In the illustrated example, color attenuation information is used. The color attenuation information is characteristic graph information showing a unique correlation between the movable positions of the pair of neutral density filters 7, 8 or neutral density filters of the same type and the transmittance of light in the wavelength range related to the component colors. This color attenuation information is obtained in advance for each of the multiple component colors and is stored in the storage unit 12a or the external storage medium 21 as the attenuation information.

[0060] Ideally, the color attenuation information for each of the multiple component colors should be identical, and the optical density (amount of light transmission) should increase or decrease proportionally (change linearly) with respect to the amount of change in the movable positions of the neutral density filters 7, 8, but in reality, there is variation among the multiple component colors, and they change slightly non-linearly with respect to the amount of change in the movable positions, as shown in Figure 5. Incidentally, it is necessary for the conversion of the movable positions of each component color to fall within the range (standard) between the two virtual lines in the figure.

[0061] In the correction process, based on the difference between the color attenuation information for the reference constituent color, which is a predetermined constituent color (in this example, "green"), and the color attenuation information for each of the other constituent colors, which are the other constituent colors (in this example, "red" and "blue"), the electrical signals output from each of the imaging elements 11R, 11B provided for each of the multiple correction constituent colors are corrected, or each correction constituent color that constitutes the image signal or image data generated before the correction process by the above-mentioned generation process is corrected.

[0062] For example, in the example shown in Fig. 5, when the pair of neutral density filters 7, 8 are rotated 320 degrees from the initial position in the direction opposite to each other, the optical density in the green wavelength range is about 1.3, while the optical density in the red wavelength range is about 1.25, and the optical density in the blue wavelength range is about 1.2. The intensity of each of the red and blue electrical signals or the colors themselves is corrected so that the optical densities of the red and blue correction constituent colors are the same or approximately the same as the optical density of the green reference constituent color. Specifically, the intensity of the red or the electrical signal related thereto is increased by 1.3 / 1.25 times, and the intensity of the blue or the electrical signal related thereto is increased by 1.3 / 1.2 times.

[0063] Incidentally, in this example, green was selected as the reference constituent color because, among the multiple constituent colors in this example, it is most similar to the spectral sensitivity of the human eye, but it is of course possible to select another constituent color as the reference color.

[0064] According to the imaging device 1 configured as described above, it is possible to appropriately correct an image in which the color balance is lost by reducing the amount of light, and it is possible to obtain image data or image signals with more natural color tones.

[0065] Incidentally, this imaging device 1 can of course be applied to digital cameras and the like that mainly capture still images, but can also be applied to video cameras and television cameras that capture moving images.

[0066] The present invention is not limited to the present embodiment, and various configurations can be adopted within the scope of the present invention. For example, the actuator 19 may be omitted, and the movable positions of the neutral density filters 7 and 8 may be changed manually. In this case, the setting operation tool 18 is also omitted.

[0067] Also, the filter device 4 can be provided inside the main body 2 or inside the interchangeable lens device 3. Furthermore, the filter device 4 can be disposed on the front side of the interchangeable lens device 3, in which case the lens device and the main body 2 are integrated together. Incidentally, it is also possible to use a fixed lens device as this lens device, rather than the interchangeable interchangeable lens device 3.

[0068] Furthermore, the shape of the rotating or rotationally actuated neutral density filters 7, 8 may be formed in a sector or semicircle instead of a circle. In the case of a semicircle shape, the start and end of the gradation are not adjacent to each other, but are located at the farthest points from each other.

[0069] Next, with reference to FIG. 6, a different portion of another embodiment of the imaging device 1 from the above embodiment will be described.

[0070] 6 is a characteristic graph showing an example of point attenuation information. In this example, point attenuation information is used as the attenuation information. The point attenuation information is characteristic graph information showing a unique correlation between the transmittance and wavelength of light in the pair of neutral density filters 7, 8 or neutral density filters of the same type for each of a plurality of set points set at predetermined intervals in the movable range of the pair of neutral density filters 7, 8 (in the example shown, each movable position where the transmittance is 100% or the movable position where the transmittance is halved from the first set point).

[0071] This point attenuation information is obtained for each of a plurality of set points, and is stored in the storage unit 12a or the external storage medium 21 as the attenuation information.

[0072] Ideally, the point attenuation information for each set point should be a constant value over the entire wavelength range. However, as shown in FIG. 6, in reality, the light transmittance varies depending on the wavelength range.

[0073] In the correction process, white balance correction is performed by correcting the electrical signals output from each of the imaging elements 11R, 11G, and 11B based on the point attenuation information of the set points corresponding to the movable positions detected by the movable position detection unit 17, or by correcting the image signals or image data generated by the generation process.

[0074] To explain more specifically, as described above, in this example, a set transmittance (in the illustrated example, 1 / 1, 1 / 2, 1 / 4, 1 / 8, 1 / 16, 1 / 32, 1 / 64), which is the light transmittance corresponding to the movable position, is predetermined for each of the multiple setting points, and the attenuation information includes information on the set transmittance of these setting points.

[0075] In the correction process, white balance correction is performed by correcting the electrical signals output from the imaging elements 11R, 11G, and 11B based on the difference between the light transmittance of the point attenuation information relating to the set point corresponding to the movable position detected by the movable position detection unit 17 and the set transmittance, or by correcting the image signal or image data generated by executing the generation process based on them.

[0076] For example, in the example shown in FIG. 6, when a pair of neutral density filters 7, 8 are positioned at a set point where the set transmittance is 1 / 4, the intensity of the electrical signal for each wavelength range (in this example, the electrical signal for each constituent color), image signal, or image data (in this example, a scalar quantity according to the resolution of each constituent color) is corrected so that the transmittance is 50% over the entire wavelength range of the image light (all constituent colors in this example).

[0077] Incidentally, when the neutral density filters 7, 8 are operated to a movable position that is not set to the set point, a characteristic graph is generated using the characteristic graph of a nearby set point, and balance correction of the electrical signal, image signal, or image data is performed using this characteristic graph.

[0078] For example, when the neutral density filters 7, 8 are operated to a movable position where the transmittance is 1 / 6, a characteristic graph of optical density and wavelength when the transmittance is 1 / 6 is generated based on the characteristic graph of optical density and wavelength when the set transmittance is 1 / 4, which is the closest above and below, and the characteristic graph of optical density and wavelength when the set transmittance is 1 / 8, and white balance correction is performed based on this characteristic graph.

[0079] Incidentally, since it is possible to obtain a combination of a correction value at the 1 / 2 point, a correction value at the 1 / 4 point, a correction value at the 1 / 8 point, and similar points and correction values, a correction function can be generated as a characteristic graph by an interpolation calculation. This correction function may be generated on the spot, or may be generated in advance and stored in the storage units 12a and 12b. In the above example, it is possible to perform white balance correction using a correction value calculated from the correction function corresponding to 1 / 6.

[0080] It is not essential that the imaging device 1 is provided with a plurality of imaging elements 11R, 11G, and 11B, and it is also possible to omit the color separation prism 9 and employ a configuration in which image light is received by a single imaging element.

[0081] Next, with reference to FIG. 7, a different portion of another embodiment of the imaging device 1 from the above embodiment will be described.

[0082] 7(A) and (B) are a plan view and a front view of a neutral density filter according to another embodiment. The neutral density filters 23, 24 are supported so as to be drivable to slide left and right in a straight line by a movable mechanism 13 including an actuator 19. As in the above-mentioned embodiment, the neutral density filters 23, 24 are also formed with a gradation such that the optical density thereof changes by continuously and monotonically increasing or decreasing on one side in the sliding direction, which is the movable direction.

[0083] The neutral density filters 23, 24 are arranged in a pair in the direction of the optical axis X, and a part of the range in which the two gradations always overlap within the movable range of the neutral density filters 23, 24 as viewed in the axial direction of the optical axis X is defined as the above-mentioned transmission range E.

[0084] The movable mechanism 13 slides the two neutral density filters 23, 24 in different directions (specifically, opposite directions) by the same movement amount. The gradation shades of the two neutral density filters 23, 24 change symmetrically with respect to the transmission range E as viewed in the axial direction of the optical axis X, and the optical density of the combined light (amount of light transmission) is uniform over the entire range.

[0085] According to the imaging device 1 configured as above, compared to the above-mentioned embodiment in which the axis 16 serving as the fulcrum for rotation or pivoting needs to be offset from the optical axis X, it is easier to achieve space saving.

[0086] 7, the pair of neutral density filters 23, 24 may be slid not in mutually opposite directions, but in a direction in which one neutral density filter 24 is inclined relative to the other neutral density filter 23. In this case, the gradation of one of the neutral density filters 23, 24 will be in the same direction as the sliding direction, but the gradation of the other will be in a direction different from the sliding direction of itself (specifically, the shading changes in the sliding direction of the one filter).

[0087] Next, with reference to FIG. 8, a different portion of another embodiment of the imaging device 1 from the above embodiment will be described.

[0088] 8 is a plan view of a neutral density filter according to another embodiment of the present invention. As shown in the drawing, a pair of neutral density filters 23, 24 arranged in the axial direction of the optical axis X may be provided in multiple pairs in the axial direction.

[0089] Next, with reference to FIG. 9, a different portion of another embodiment of the imaging device 1 from the above embodiment will be described.

[0090] 9 is a front view of a neutral density filter according to another embodiment. A plurality of neutral density filters 26, 27 shown in the figure are arranged in a switching direction (up and down direction in the illustrated example) that intersects (orthogonal to) the above-mentioned sliding direction (left and right direction in the illustrated example) when viewed in the light transmitting direction, and the neutral density filters 26, 27 arranged in the switching direction have gradations with different patterns.

[0091] In the illustrated example, the gradation of the two dimming filters 26, 27 is set so that the transmittance of one dimming filter 26 gradually and monotonically increases in the range of 0 to 50% toward one side in the sliding direction, while the transmittance of the other dimming filter 28 gradually and monotonically increases in the range of 50 to 100% toward the other side in the sliding direction.

[0092] The movable mechanism 13 including the actuator 19 slides the plurality of neutral density filters 26, 27 arranged in the switching direction together in a unified manner so that the neutral density filters 26, 27 that transmit light can be switched.

[0093] Next, with reference to FIG. 10, a different portion of another embodiment of the imaging device 1 from the above embodiment will be described.

[0094] 10 is a plan view of a neutral density filter according to another embodiment. The neutral density filter 28 shown in the figure is made of a flexibly deformable film, and is hung around a plurality of rotating rollers 29, 30 so as to draw a circular endless track. The neutral density filter 28 is a gradation ND filter, as in the above-mentioned embodiment. When viewed in the direction that transmits the image light, the portion where the films overlap is located in the passing range R through which the light passes.

[0095] The light transmittance of the film changes as the portion of the film positioned within the passing range R is changed by the rotation of the rollers 29, 30. Incidentally, the rollers 29, 30 constitute a part of the movable mechanism 13. One of the rollers 29, 30 is one or a pair of drive rollers 29, 29 that are rotationally driven by the actuator 19, and the remaining rollers are free-rotating rollers 30 that are supported in an idling state.

[0096] According to the imaging device 1 configured as above, the size of the filter device 4 can be easily further reduced. [Explanation of symbols]

[0097] 1. Imaging device 2 Main unit 3. Interchangeable lens device 4. Lens device 6. Chassis 6a Passing hole (introduction hole) 6b Passing hole 7 Neutral Density Filter (Gradation ND Filter) 7a Base material 7b Optical film 8 Neutral Density Filters (Gradation ND Filters) 8a Base material 8b Optical film 9. Color separation prism (spectroscope) 11R image sensor 11G image sensor 11B Image sensor 12 Image processing section 12a Storage section 13 Movable mechanism 14 Filter side control section 16 axes 17 Movable position detector 18 Setting operation tool 19 Actuator (motor) 20. Cabinet 20a intake hole 21 External storage medium (storage unit) 22 Output section 23 Neutral Density Filter (Gradation ND Filter) 24 Neutral Density Filter (Gradation ND Filter) 26 Neutral Density Filter (Gradation ND Filter) 27 Neutral Density Filter (Gradation ND Filter) 28 Neutral Density Filter (Gradation ND Filter) 29 Drive roller (roller) 31 Idle roller (roller) LR optical axis LG optical axis LB optical axis E Transmission Range R Passing range X optical axis

Claims

1. At least one neutral density filter that is movably supported and includes a gradation in which light transmittance changes continuously in a movable direction; at least one image sensor that captures light whose amount has been reduced by passing through the neutral density filter and converts it into an electrical signal; a movable position detector that detects a light-attenuating state by detecting a movable position of the light-attenuating filter; an image processing unit to which the electrical signal and the detection result of the movable position detection unit are input; A storage unit, Attenuation information, which is a unique correlation between the transmittance of light in the neutral density filter or a neutral density filter of the same type as the neutral density filter and the wavelength of light, is previously obtained; The storage unit stores the attenuation information, The image processing unit is configured to perform white balance correction based on the electrical signal, a detection result by the movable position detection unit, and the attenuation information when generating image data or an image signal based on the electrical signal.

1. An imaging device comprising:

2. a spectrometer that separates the light having a reduced amount of light transmitted through the neutral density filter into three or more component colors that constitute the image data or image signal by dividing the light into predetermined wavelength ranges, the imaging element is provided for each of the plurality of component colors; color attenuation information, which is information on a unique correlation between a movable position of the neutral density filter or a neutral density filter of the same type as the neutral density filter and a transmittance of light in a wavelength range related to the constituent colors, is obtained in advance for each of the plurality of constituent colors; The attenuation information includes a plurality of the color attenuation information. The imaging device according to claim 1 .

3. The image processing unit is configured to perform the white balance correction process by correcting the electrical signal output from each of the image pickup devices provided for each of the plurality of correction constituent colors, or the image signal or each correction constituent color constituting the image data, based on a difference between the color attenuation information related to the reference constituent color, which is one of the predetermined constituent colors, and the color attenuation information for each of the correction constituent colors, which are the other plurality of constituent colors. The imaging device according to claim 2 .

4. point attenuation information, which is information on a unique correlation between the transmittance and wavelength of light in the light-reducing filter or a light-reducing filter of the same type, is obtained in advance for each of a plurality of set points set at predetermined intervals in the movable range of the light-reducing filter; the attenuation information includes point attenuation information for each set point; The image processing unit is configured to perform the white balance correction process by correcting the electrical signal output from the imaging element or correcting an image signal or image data based on point attenuation information of the set point corresponding to the movable position detected by the movable position detection unit. The imaging device according to claim 1 .

5. For each of the set points, a set transmittance is previously determined, which is a light transmittance corresponding to the movable position of the set point; The attenuation information includes information on the set transmittance of each set point; The image processing unit is configured to perform the white balance correction process by correcting the electrical signal output from the imaging element or correcting an image signal or image data based on a difference between the light transmittance of the point attenuation information related to the set point corresponding to the movable position detected by the movable position detection unit and the set transmittance of the set point. The imaging device according to claim 4.

6. The optical fiber further includes a movable mechanism that supports the neutral density filter so as to rotate or pivot about a linear axis that is parallel to a light transmitting direction, The gradation is configured to change continuously in a direction around the axis. The imaging device according to claim 1 .

7. The two neutral density filters supported by the movable mechanism so as to rotate or pivot about the same axis and shaped into the same circle are arranged side by side in the direction of the axis, a part of a range in which the two gradations always overlap within a movable range of the neutral density filter as viewed in the direction of the axis is a transmission range through which light reaching the image sensor passes, The movable mechanism is configured to rotate or pivot the two neutral density filters in opposite directions by the same amount of movement, The two neutral density filters are configured such that the gradation shading of each filter changes in an opposite phase with respect to the transmission range when viewed in the direction of the axis, and the combined light transmittance of each filter is uniform in the transmission range. The imaging device according to claim 6.

8. a movable mechanism for supporting the neutral density filter so as to be slidable along a straight line; The gradation is configured to change continuously in the sliding direction of the neutral density filter. The imaging device according to claim 1 .

9. The neutral density filters are arranged in a pair in a light transmitting direction, a part of a range in which the two gradations always overlap within a movable range of the neutral density filter when viewed in a direction in which light is transmitted is a transmission range through which light reaching the image sensor passes; The movable mechanism is configured to slide the two neutral density filters in different directions by the same amount of movement. The imaging device according to claim 8.

10. The movable mechanism is configured to slide the two neutral density filters in opposite directions by the same amount of movement, The two neutral density filters are configured such that the gradation of each filter changes symmetrically with respect to the transmission range when viewed in the direction in which light is transmitted, and the combined light transmittance of each filter is uniform within the transmission range. The imaging device according to claim 9.

11. A plurality of pairs of the above-mentioned neutral density filters arranged in a direction in which light passes are provided.

11. The imaging device according to claim 9 or 10.

12. The light-reducing filters are arranged in a switching direction that intersects with the sliding direction when viewed in a direction that transmits light, The plurality of neutral density filters arranged in the switching direction have gradations of different patterns, The movable mechanism is configured to slide each of the plurality of neutral density filters arranged in the switching direction in such a manner that the neutral density filters that transmit light can be switched. The imaging device according to claim 8.

13. The neutral density filter is made of a flexibly deformable film, and is wound around a plurality of rotating rollers so as to draw a circular endless track; When viewed in a direction that transmits light reaching the imaging element, the overlapping portions of the films are disposed within a range through which the light passes, The film is configured such that the light transmittance is changed by changing the portion of the film located in the passing range by the rotation of the roller. The imaging device according to claim 1 .

Images