Optical wavelength selection limiting apparatus and image system

Abstract

To control the light amount of a specific wavelength.SOLUTION: An optical wavelength selection restricting apparatus for limiting the amount of light of a specific wavelength includes: an optical filter made of a light-transmitting member of a color complementary to that of the light of the specific wavelength that blocks transmission of the light of the specific wavelength and covers a transmission region through which light of all wavelengths pass; and a moving mechanism for moving the optical filter, the moving mechanism moving the optical filter to control the area of the optical filter covering the transmission region so as to limit the amount of light of the specific wavelength.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an optical wavelength selection and limiting device for controlling the amount of light of a specific wavelength. [Background technology]

[0002] An imaging system for capturing color images captures images using signals of three wavelengths: red, green, and blue, the three primary colors of light. In the conventional imaging system shown in Figure 5, when the color temperature of the light source is extremely high (blue) or low (red), the amount of light of a specific wavelength exceeds the dynamic range of an optical-to-electrical signal converter 42. Therefore, the system reduces the overall amount of light using a lens aperture or other device to prevent the amount of light entering the image sensor from saturating, and then amplifies the electrical signal of the color with insufficient light. An optical input signal 39 is input to a dimming device 40, such as a lens aperture mechanism. The dimming device 40 attenuates the amount of light exceeding the dynamic range of the downstream optical-to-electrical signal converter 42 to an appropriate amount, and the optical signal is converted into an electrical signal by the optical-to-electrical signal converter 42, which includes an image sensor. The signal level of the electrical signal output from the optical-to-electrical signal converter 42 is detected by signal level detectors 43, 44, and 45, and a control device 41 controls the dimming level of the dimming device 40 and the amplification levels of amplifiers 46, 47, and 48 according to the detected signal level. The signals amplified by amplifiers 46, 47, and 48 are combined into an output video signal 49 and output from the video system. In this conventional video system, after the optical-to-electrical signal converter 42 separates the light source color, the amount of light received by each pixel of the optical-to-electrical signal converter 42 varies depending on the wavelength, and the overall amount of light is suppressed to match the maximum amount of light. For example, in the case of a light source with a strong red color, such as sunlight in the evening, the amount of light in the red channel exceeds the dynamic range of the optical-to-electrical signal converter 42, but the amount of light received by the blue channel image sensor is insufficient, requiring the signal to be amplified by amplifiers 46, 47, and 48 in the subsequent stages. In other words, even if the amount of light in the blue channel does not exceed the dynamic range, if the amount of light in the red channel exceeds the dynamic range of the image sensor, the overall amount of light must be reduced to avoid signal saturation. Therefore, even if the amount of light in the blue channel is sufficient, the amount of light must be reduced by the optical system before being electrically amplified, resulting in increased noise. Conversely, under a blue sky or other blue light source, noise in the red channel increases.

[0003] The conventional video system shown in Fig. 6 has similar signal processing to the conventional video system shown in Fig. 5, but differs in the spectroscopic device (e.g., color separation prism) 52 and optical-electrical signal conversion devices 54, 55, and 56. An optical input signal 50 is input to a dimming device 51 such as a lens aperture mechanism, and separated into wavelengths by a spectroscopic device 52. The separated optical signals are input to optical-electrical signal conversion devices 54, 55, and 56 such as image sensors. A control device 53 operates independent electronic shutters for the optical-electrical signal conversion devices 54, 55, and 56 in accordance with the optical signal amount, changing the exposure time of the image sensors in the optical-electrical signal conversion devices 54, 55, and 56 to match the red, green, and blue signal components without increasing noise depending on the color (wavelength) of the light source. The signal levels of the electrical signals output from optical-electrical signal converters 54, 55, and 56 are detected by signal level detectors 57, 58, and 59, respectively, and control device 53 controls the degree of dimming of dimming device 51 and the degree of amplification of amplifiers 60, 61, and 62 according to the detected signal levels. The signals amplified by amplifiers 60, 61, and 62 are output from the video system as output video signals 63, 64, and 65, respectively. In the conventional video system shown in Figure 6, the exposure time is changed to prevent saturation of the amount of light received by optical-electrical signal converters 54, 55, and 56. However, because the exposure time is different for each color, there is a problem that colored afterimages are generated in moving subjects, resulting in unnatural images.

[0004] Patent Document 1 (WO 2016 / 046959) is a background art in this field. Patent Document 1 describes an imaging method in which, in an imaging device having a color separation optical system and three or more CMOS imaging elements, B is captured at a speed that is an integer N times the number of output image frames, G or (G1 and G2) is captured at an integer M times that is an integer N+1 or greater, and R is captured at an integer M times that is an integer N+1 or greater, and the vertical synchronization phases of the B, G, and R, or B, G1, G2, and R, captured frames are offset by approximately half the even-number speed vertical synchronization period so that the center phases of the B, G, and R, or B, G1, G2, and R, captured frames used in the output image have approximately the same vertical synchronization phase, and the vertical effective images of the B, G, and R, or B, G1, G2, and R, captured frames with approximately the same vertical synchronization phase are used as the output image. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 046959 Summary of the Invention [Problem to be solved by the invention]

[0006] Depending on the light intensity of each wavelength from the light source, there are wavelengths where the light intensity exceeds the saturation level of the image sensor, and wavelengths where the light intensity is insufficient. In conventional technology, the light intensity of all wavelengths is reduced using the lens aperture mechanism so that the amount of light incident on the image sensor does not exceed the saturation level of the image sensor, and then the signal of the wavelength with insufficient light is amplified. When the electrical signal is amplified, the noise component is also amplified, resulting in a decrease in image quality.

[0007] An object of the present invention is to provide an optical wavelength selection and restriction device that controls the amount of light of a specific wavelength and suppresses degradation of image quality. [Means for solving the problem]

[0008] A representative example of the invention disclosed in the present application is as follows: That is, an optical wavelength selection and limiting device for limiting the amount of light of a specific wavelength, comprising an optical filter that blocks the transmission of light of the specific wavelength and is made of a light-transmitting member of a color complementary to the color of light of the specific wavelength, and that covers a transmission area through which light of all wavelengths passes, and a movement mechanism that moves the optical filter, and the movement mechanism moves the optical filter and controls the area that the optical filter covers on the transmission area, thereby limiting the amount of light of the specific wavelength.

[0009] Furthermore, an example of an optical wavelength selection and limiting device of the present invention is characterized in that it comprises an aperture mechanism having a plurality of blades constituted by the optical filter, the aperture mechanism forms the transmission area surrounded by the plurality of blades, and the movement mechanism moves the plurality of blades to control the area of ​​the area in the transmission area through which light of all wavelengths can pass.

[0010] Furthermore, one example of a video system of the present invention comprises the optical wavelength selection and limiting device described above, a control device for controlling the optical wavelength selection and limiting device, a conversion device for converting an optical signal transmitted through the optical wavelength selection and limiting device into an electrical signal, and an amplifier for amplifying the electrical signal output from the conversion device, and is characterized in that the control device operates the optical wavelength selection and limiting device so as to limit the amount of light of wavelengths whose amount of light exceeds the dynamic range of the conversion device. [Effects of the Invention]

[0011] According to one aspect of the present invention, it is possible to control the balance of the light intensity of each wavelength and to suppress deterioration of image quality due to noise. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiment of the present invention. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a configuration of a video system according to an embodiment of the present invention; [Figure 2] FIG. 1 is a diagram illustrating a configuration of an optical system of a video system according to an embodiment of the present invention. [Figure 3] 1 is a diagram illustrating the configuration of a specific wavelength attenuation device according to an embodiment of the present invention. [Figure 4] 1A and 1B are diagrams illustrating an example of signal processing by the conventional video system and an example of signal processing by the video system of this embodiment. [Figure 5] FIG. 1 is a block diagram showing the configuration of a conventional video system. [Figure 6] FIG. 1 is a block diagram showing the configuration of a conventional video system. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a block diagram showing the configuration of a video system according to an embodiment of the present invention.

[0015] The video system of this embodiment includes specific wavelength attenuators 2, 3, and 4, an optical-electrical signal converter 5, a control device 6, signal level detectors 7, 8, and 9, and amplifiers 10, 11, and 12. The optical-electrical signal converter 5, the control device 6, the signal level detectors 7, 8, and 9, and the amplifiers 10, 11, and 12 constitute an imaging unit 18.

[0016] The specific wavelength attenuator 2 attenuates a specific wavelength component of the incident optical input signal 1 and transmits other wavelength components as they are. Similarly, the specific wavelength attenuators 3 and 4 also attenuate light of specific wavelength components. The specific wavelength attenuators 2, 3, and 4 constitute an optical wavelength selection and limiting device and attenuate different wavelength components, for example, the three primary colors of light.

[0017] The optical-electrical signal conversion device 5 is composed of an imaging element or the like, converts the input optical signal that has passed through the specific wavelength attenuators 2, 3, and 4 into an electrical signal, and outputs an electrical signal corresponding to light of a specific wavelength component (for example, the three primary colors of light) to the signal level detection devices 7, 8, and 9. Since the dynamic range of the optical-electrical signal conversion device 5 is finite, if an amount of light that exceeds the dynamic range is input, a saturated electrical signal is output.

[0018] The signal level detectors 7, 8, and 9 detect the levels of the electrical signals corresponding to the optical wavelength components assigned to them, and output the detected signal levels to the control device 6. The signal level detectors 7, 8, and 9 also output the input signals to amplifiers 10, 11, and 12, respectively.

[0019] When the signal level output from the signal level detectors 7, 8, and 9 exceeds a set threshold, the control device 6 performs feedback control to increase the amount of light attenuation of the specific wavelength attenuators 2, 3, and 4 corresponding to the wavelengths exceeding the threshold. By repeating this feedback control and maintaining the amount of light attenuation of the specific wavelength attenuators 2, 3, and 4 at that time when the detected signal level falls below the threshold, the optical signal can be converted into a video signal within the dynamic range of the optical-electrical signal converter 5.

[0020] Amplifiers 10, 11, and 12 amplify the signals output from signal level detectors 7, 8, and 9. The signals amplified by amplifiers 10, 11, and 12 are combined into output video signal 13, which is output from the video system. The amplification levels of amplifiers 10, 11, and 12 are individually controlled by control device 6.

[0021] Furthermore, in the video system of this embodiment, specific wavelength attenuation devices 2, 3, and 4 are provided for each wavelength (color) of light, so the amount of attenuation can be set for each color, and for example, the signal level of each color can be made uniform. Conventional attenuation mechanisms attenuate the entire wavelength range using a lens aperture mechanism installed in front of a color separation prism, so it is not possible to attenuate each color individually.

[0022] Furthermore, in the video system of this embodiment, it is possible to align the signal levels of each wavelength by changing the exposure time of the optical-electrical signal conversion device 5 for each wavelength. However, since the amount of afterimage changes depending on the exposure time, a conventional video system (FIG. 6) that combines signals of each wavelength would produce an unnatural image. In the configuration of this embodiment, the specific wavelength attenuators 2, 3, and 4 are used to attenuate each color (wavelength), so there is no change in afterimage and the image obtained by combining signals of each wavelength does not look unnatural.

[0023] Furthermore, in conventional video systems, for example, amplifiers 46, 47, 48, 60, 61, and 62 must be used to change the amplification factor for each wavelength and attenuate the light in order to match the signal levels of each wavelength, resulting in an increase in signal noise at wavelengths with high amplification factors. However, in the video system of this embodiment, the signal levels of each wavelength can be attenuated individually using specific wavelength attenuators 2, 3, and 4, so the amplification factors of amplifiers 10, 11, and 12 in the subsequent stages can be minimized, making it possible to obtain low-noise images.

[0024] As shown in Figures 2 and 3, the specific wavelength attenuation devices 2, 3, and 4 transmit light of wavelengths other than those to be filtered using optical filters of complementary colors to the wavelengths to be attenuated. For example, a mechanism for moving the optical filters can be provided, and the area of ​​the transmission region through which light of all wavelengths is transmitted can be controlled by the movement of the optical filters, thereby limiting the amount of light of specific wavelengths. The optical filters can be configured, for example, with light-transmitting members of cyan, magenta, and yellow, which are complementary to the three primary colors of light: red, green, and blue. The cyan light-transmitting member transmits light of wavelengths other than red, the magenta light-transmitting member transmits light of wavelengths other than green, and the yellow light-transmitting member transmits light of wavelengths other than blue. Various mechanisms can be used for the specific wavelength attenuation devices 2, 3, and 4. As an example, Figure 3 shows specific wavelength attenuation devices 2, 3, and 4 with an iris diaphragm mechanism. Light transmitted through the lens group 14 is blocked or transmitted by the specific wavelength attenuation devices 2, 3, and 4 of each wavelength before reaching the imaging unit 18. The specific wavelength attenuation devices 2, 3, and 4 shown in Figure 3 are configured with an aperture mechanism having multiple blades formed with optical filters of the wavelengths to be attenuated, forming a transmission area surrounded by the multiple blades arranged around the periphery. A movement mechanism then moves the multiple blades to control the area of ​​the transmission area. That is, reducing the transmission area surrounded by the blades of the cyan light-transmitting member reduces the amount of red light, while increasing the transmission area surrounded by the blades of the cyan light-transmitting member increases the amount of red light. However, because the cyan light-transmitting member transmits green and blue light, the amount of green and blue light remains unchanged regardless of the size of the transmission area surrounded by the blades of the cyan light-transmitting member.

[0025] Furthermore, each of the specific wavelength attenuators 2, 3, and 4 controls the amount of light of a specific wavelength using an aperture mechanism, and the specific wavelength attenuators 2, 3, and 4 can independently adjust the aperture opening for a desired wavelength, so that the depth of field for each color can be independently controlled, allowing for accurate adjustment of the camera focus.

[0026] 4A and 4B are diagrams showing an example of signal processing by a conventional video system and an example of signal processing by the video system of this embodiment, in which the horizontal axis represents frequency and the vertical axis represents light intensity.

[0027] 4A, light of the three primary colors of red, green, and blue is input, with the red signal having the greatest amount of light, followed by the green signal and the blue signal having the least amount of light, as shown in FIG. 4A. The amount of light of the red signal exceeds the dynamic range of the optical-electrical signal conversion device 5, while the amounts of light of the green and blue signals are less than the dynamic range of the optical-electrical signal conversion device 5.

[0028] In this case, in a conventional video system, as shown in Fig. 4(B), the lens diaphragm mechanism reduces the overall amount of light so that the maximum amount of light does not exceed the dynamic range of the optical-electrical signal conversion device 5, and as shown in Fig. 4(C), the signals are amplified in subsequent amplifiers 10, 11, and 12 so that the signal level differences between red, green, and blue are reduced. In other words, the green and blue signals must be amplified in subsequent amplifiers 10, 11, and 12 by the amount of light attenuated by the diaphragm mechanism, which also amplifies noise.

[0029] On the other hand, in the video system of this embodiment, the red, green, and blue signals can be dimmed at different rates. In this example, since only the light amount of the red signal exceeds the dynamic range of the optical-electrical signal conversion device 5, as shown in Figure 4(D), one of the specific wavelength dimming devices 2, 3, and 4 dims only the red signal, while the other specific wavelength dimming devices 2, 3, and 4 do not dim the green and blue signals. Therefore, as shown in Figure 4(E), the amplification rate of the subsequent amplifiers 10, 11, and 12 can be reduced, thereby reducing the amplification of noise that accompanies signal amplification and enabling the acquisition of images based on signals with less degradation.

[0030] As described above, the optical wavelength selection and limiting device according to the embodiment of the present invention includes an optical filter that is composed of a light-transmitting member of a complementary color to a specific wavelength of light and blocks the transmission of light of that specific wavelength. The optical filter covers a transmission area that transmits light of all wavelengths, and a movement mechanism that moves the optical filter. The movement mechanism moves the optical filter and controls the area that the optical filter covers in the transmission area to limit the amount of light of the specific wavelength, thereby controlling the balance of the amount of light of each wavelength. Furthermore, since light other than the specific wavelength is not attenuated, light of wavelengths that do not exceed the dynamic range is not attenuated, thereby effectively utilizing the dynamic range of the optical-to-electrical signal conversion device 5. Furthermore, by suppressing the amount of light for each wavelength before the optical-to-electrical signal conversion device 5 converts the optical signal to an electrical signal, the amplification factor of the electrical signal is reduced, and degradation of image quality due to noise can be suppressed.

[0031] Furthermore, specific wavelength attenuators 2, 3, and 4 are arranged upstream of the optical-electrical signal converter 5, and the light intensity for each wavelength of the optical signal output from the specific wavelength attenuators 2, 3, and 4 is controlled according to the amount of light received at each wavelength by the optical-electrical signal converter 5. As a result, it is possible to prevent the increase in electrical noise due to the color temperature of the light source and the occurrence of colored afterimages due to differences in exposure time, as in conventional imaging systems. The amount of afterimage varies depending on the time it takes for the image sensor to receive light to obtain one frame of optical signal. A longer light-receiving time results in a brighter image with more afterimage, while a shorter light-receiving time results in a darker image with less afterimage. Therefore, if the light-receiving time of the image sensor is varied for each color to equalize the light intensities of red, green, and blue, the amount of afterimage for each color will change. For example, if a moving image is captured using different light-receiving times for each color, the amount of afterimage for each color will differ, resulting in an unnatural image. However, in this embodiment, the image is captured using the same light-receiving time without varying the light-receiving time for each color, so unnaturalness due to differences in the amount of afterimage for each color does not occur.

[0032] The present invention is not limited to the above-described embodiments, but includes various modifications and equivalent configurations within the spirit and scope of the appended claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to configurations including all of the described configurations. Furthermore, part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Furthermore, the configuration of another embodiment may be added to the configuration of one embodiment. Furthermore, part of the configuration of each embodiment may be added, deleted, or replaced with other configurations.

[0033] Furthermore, the aforementioned configurations, functions, processing units, processing means, etc. may be realized in part or in whole in hardware, for example by designing them as integrated circuits, or may be realized in software by having a processor interpret and execute a program that realizes each function.

[0034] Information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or in a recording medium such as an IC card, an SD card, or a DVD.

[0035] In addition, the control lines and information lines shown are those that are considered necessary for explanation, and do not necessarily represent all the control lines and information lines that are necessary for implementation. In reality, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0036] 1...optical input signal, 2...specific wavelength attenuation device, 3...specific wavelength attenuation device, 4...specific wavelength attenuation device, 5...optical-electrical signal conversion device, 6...control device, 7...signal level detection device, 8...signal level detection device, 9...signal level detection device, 10...amplifier, 11...amplifier, 12...amplifier, 13...output video signal, 14...lens group, 18...imaging unit, 19...incident light, 20...incident light, 21...incident light, 26...signal saturation level of optical-electrical signal conversion device, 28...amount of attenuation of all wavelength components, 230...amount of attenuation of specific wavelength components, 32...example of increased noise component in conventional method, 34...example of increased noise component in present invention, 39...optical input signal, 40...attenuation device, 41...control device, 42...optical-electrical signal conversion device, 42...signal level detection device, 44...signal level detection device, 45...signal level detection device, 46...amplifier, 47...amplifier, 48...amplifier, 49...output video signal, 50...optical input signal, 51...dimming device, 52...spectroscopic device, 53...control device, 54...optical-electrical signal conversion device, 55...optical-electrical signal conversion device, 56...optical-electrical signal conversion device, 57...signal level detection device, 58...signal level detection device, 59...signal level detection device, 60...amplifier, 61...amplifier, 62...amplifier, 63...output video signal, 64...output video signal, 65...output video signal

Claims

1. An optical wavelength selection and limiting device that limits the amount of light of a specific wavelength, an optical filter that is composed of a light-transmitting member of a complementary color to the specific wavelength of light and blocks transmission of the specific wavelength of light, and that covers a transmission region through which light of all wavelengths is transmitted; a moving mechanism for moving the optical filter, The optical wavelength selection and limiting device is characterized in that the movement mechanism moves the optical filter to control the area that the optical filter covers in the transmission region, thereby limiting the amount of light of the specific wavelength.

2. 2. The optical wavelength selection and limiting device according to claim 1, an aperture mechanism having a plurality of blades constituted by the optical filter; the aperture mechanism forms the transmission area surrounded by the plurality of blades; The optical wavelength selection and limiting device is characterized in that the movement mechanism moves the plurality of blades to control the area of ​​the region in the transmission region through which light of all wavelengths can be transmitted.

3. A video system for capturing video, an optical wavelength selection / limiting device according to claim 1 or 2; a control device for controlling the optical wavelength selection and limiting device; a conversion device that converts the optical signal transmitted through the optical wavelength selection and limiting device into an electrical signal; an amplifier that amplifies the electrical signal output from the conversion device, The video system is characterized in that the control device operates the optical wavelength selection limiting device so as to limit the amount of light of wavelengths whose amount of light exceeds the dynamic range of the conversion device.

Images