JP2010093525A - Imaging device - Google Patents

Abstract

An object of the present invention is to enable an infrared cut filter switching control corresponding to a variation in the amount of infrared light in a shooting environment in an imaging device that performs switching control of an infrared cut filter.
Evaluation of an infrared light amount that is omitted when an infrared cut filter is inserted between an optical lens and an image sensor, or an infrared light amount that is included when an infrared cut filter is detached from between an optical lens and an image sensor. Means, history means for storing the history of the infrared light quantity evaluation value, selection means for selecting a specific infrared light quantity evaluation value from the infrared light quantity evaluation values stored in the history means, and the specified infrared light quantity The reference value for the insertion or removal control of the infrared cut filter is made variable based on the evaluation value.
[Selection] Figure 1

Description

  The present invention relates to an imaging apparatus having an automatic insertion / removal control function of an infrared cut filter.

  In many cases, an imaging device attenuates infrared light reaching the imaging device using an infrared cut filter or a similar means for cutting infrared rays. This is because the infrared light region is not visible to the human eye, but the image sensor is also sensitive to the infrared light region, so the output signal of the image sensor includes a signal containing infrared light. This is to prevent an unnatural color image generated by the image.

  On the other hand, when shooting in a situation where the amount of light cannot be sufficiently obtained such as at night, the sensitivity of the imaging apparatus can be improved by using infrared light. In other words, an infrared cut filter attachment / detachment control function is provided in the image pickup device. When the light quantity is sufficient, the infrared cut filter is attached. When the light quantity is insufficient, the infrared cut filter is removed to improve the sensitivity of the image pickup apparatus. I am letting. However, as described above, when the infrared cut filter is removed, color development becomes unnatural, so switching to monochrome photography is performed.

  For example, surveillance video cameras that monitor streets, etc. need to obtain images that can be monitored both day and night, and are equipped with an infrared cut filter during the day, and the infrared cut filter is automatically removed at dusk. Then, there is an imaging device having an automatic attachment / detachment control function of the infrared cut filter that automatically attaches the infrared cut filter again.

  This infrared cut filter attachment / detachment determination is made based on the amount of light input to the lens of the image pickup device. When the amount of light exceeds a predetermined value and the output image of the image pickup device can be kept sufficiently bright, the image is taken in color, and the amount of light is reduced. Therefore, when the minimum necessary value is obtained such that the brightness of the output video of the image pickup apparatus cannot be maintained, the image is switched to monochrome.

  However, the ratio of the amount of infrared light and the amount of visible light included in the incident light from the subject is not constant, and the amount of light with the infrared cut filter attached, that is, the amount of light that does not include infrared light. When the infrared cut filter is removed when it is determined that it is less than the predetermined value, a phenomenon called hunting occurs in which the light amount is determined to be equal to or greater than the predetermined value and the attachment / detachment of the infrared cut filter is repeated due to the increase in the light amount due to infrared light. There is a case.

  Regarding the prevention of such a hunting phenomenon, Patent Document 1 states that “the difference in sensitivity greatly varies depending on the illumination of the subject, so that the hunting phenomenon is sufficiently achieved only by forming a hysteresis in the integral judgment value between color photography and monochrome photography. “The infrared cut filter switching control unit is able to detect the dummy using the infrared cut filter and the dummy from the feedback control value output from the AGC (Auto Gain Controller) control unit. It is disclosed as a solving means that a difference in sensitivity of photographing using a filter is obtained and the switching timing of the filter is adjusted based on the difference in sensitivity.

JP 2003-198933 A

By the way, an imaging apparatus having an automatic attachment / detachment control function of an infrared cut filter is often used as an imaging apparatus for crime prevention / monitoring purposes, and continues to shoot day and night in an installed shooting environment. In addition, the installation of an image pickup device having an automatic attachment / detachment control function for an infrared cut filter is often performed in the daytime because the installation location is high or the number of installations is large. It is not uncommon for the infrared cut filter installation / removal determination setting operation to be performed in an environment different from the shooting environment such as dusk or dawn when the filter is attached / detached.

  As a result, there are two unintended settings. In the first case, the setting is such that monochrome photography is performed for an unnecessarily long time in an environment where there is little infrared light and the sensitivity does not increase much even if the infrared cut filter is removed. Secondly, in an environment where there is a lot of infrared light and the sensitivity can be expected to increase sufficiently by removing the infrared cut filter, the S / N is poor due to taking longer time for color shooting than necessary. This is a case where shooting is performed with a dark image.

  In addition, after installation of the imaging device, it may be assumed that the illumination environment in the vicinity changes and the amount of infrared light changes from the initial setting of the imaging device. In such a case, it is necessary to review the settings for controlling the infrared cut filter again. To do.

However, in the feedback control output from the AGC control unit described in Patent Document 1, switching to monochrome imaging is performed when the sensitivity difference between imaging using an infrared cut filter and imaging using a dummy filter is equal to or greater than a monochrome determination value. However, since it is impossible to make the monochrome determination value variable according to the sensitivity difference, it cannot be adjusted according to the change in the environmental conditions described above.
Therefore, an object of the present invention is to provide an imaging apparatus having a function of automatically changing the control standard of the infrared cut filter according to the installation environment.

  The present invention relates to an image pickup apparatus that performs switching control for inserting and removing an infrared cut filter between an optical lens and an image pickup device, and an infrared ray cut filter from the amount of infrared light that is omitted when the infrared cut filter is inserted and between the optical lens and the image pickup device. Infrared light quantity evaluation means included when desorbing, a history means for storing a history of the infrared light quantity evaluation value, and a specific infrared light quantity evaluation value from among the infrared light quantity evaluation values stored in the history means The selection means for selecting and the reference value for the insertion or removal control of the infrared cut filter based on the specified infrared light quantity evaluation value are made variable, and the detailed means is according to the claims.

  According to the imaging apparatus of the present invention, when there is a lot of infrared light in the shooting environment, the infrared light amount is utilized to realize an image with good S / N even at low illuminance, and there is little infrared light in the shooting environment. In such a case, it is possible to prevent a monochrome image from being taken for a longer time than necessary.

  An embodiment of an imaging apparatus according to the present invention will be described.

  FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention.

  In FIG. 1, a lens 1 focuses incident light on an image pickup device on an image pickup surface of an image pickup device 4, and a diaphragm 2 adjusts an amount of light reaching the image pickup surface of the image pickup device 4. The infrared cut filter 3 removes infrared light from light reaching the imaging surface of the image sensor 4. The imaging element 4 converts the light received on the imaging surface into an electrical signal.

  The signal processing unit 5 has an automatic gain control unit (AGC) inside, adjusts the output signal level of the image sensor 4 under the control of the microcomputer 16, and converts it to a specific format (NTSC system, PAL system, etc.). Output.

The motor (for aperture) 6 controls the aperture 2 with the control amount and timing calculated in the microcomputer 16. The motor (for infrared cut filter) 7 is driven by a switching control signal output from the switching control / switching data acquisition unit 8 inside the microcomputer 16 to attach / detach the infrared cut filter 3 between the lens 1 and the image sensor 4. Do.
Hereinafter, control in the microcomputer 16 will be described.

  First, the illuminance estimation calculation unit 13 determines the brightness of the subject. In this embodiment, the relationship between the illuminance estimation value (L) is calculated as L = 1 / G based on the gain amount (G) of the AGC of the signal processing unit 5, and the darker the gain amount (G) of the AGC, The smaller the value is, the brighter it is, and the estimated illuminance (L) is updated every field (every 1/60 seconds in NTSC format).

  The estimated illuminance value (L) calculated by the illuminance estimation calculation unit 13 is output to the switching control / pre-switching data acquisition unit 8 and the normal control mode switching timing control unit 10.

  The control mode switching unit 9 selects the “normal control mode” when the “sensitivity increase expected value SU” to be described later is equal to or higher than the minimum required level (SUreq), and when it is smaller than the minimum required level (SUreq), “ Select “Data acquisition mode”.

  The normal control mode switching timing control unit 10 functions only when the control mode switching unit 9 selects “normal control mode”, and switches between “illuminance estimation value (L)” notified from the illuminance estimation calculation unit 13. A “switching control reference” (to be described later) notified from the control reference calculation unit 15 is compared and determined, and the switching control / switching data acquisition unit 8 is notified of the switching timing for attaching / detaching the infrared cut filter 3.

  The data acquisition mode switching timing control unit 11 functions only when the control mode switching unit 9 selects the “data acquisition mode” and operates almost as a color fixed mode. However, in the “data acquisition mode”, a period in which the infrared cut filter 3 is removed by the timer 14 for a very short time of the day is provided. For example, a switching instruction is sent to the switching control / pre / post-switching data acquisition unit 8 at 00:00 every day to notify the switching timing for attaching / detaching the infrared cut filter 3. With this switching instruction as a trigger, the expected increase in sensitivity is updated and the control mode is reviewed. At this time, if the “sensitivity increase expected value SU” exceeds the minimum required level SUreq, the control returns to the normal control mode.

  The switching control / pre / post-switching data acquisition unit 8 performs a switching operation on the motor (for infrared cut filter) 7 based on the notification of the switching timing from the normal control mode switching timing control unit 10 and the data acquisition mode switching timing control unit 11. The switching control signal is output, and the illuminance estimation value L immediately before switching is acquired from the illuminance estimation calculation unit 13, and is stored as “illuminance immediately before switching (La)”.

  On the other hand, when the infrared cut filter 3 is removed from the imaging surface of the image sensor 4, the output signal of the image sensor 4 increases, and the gain amount G of AGC gradually decreases in the signal processing unit 5 (infrared rays) Note that the amount of gain does not decrease at the moment when the cut filter is removed. After several fields, the gain amount of AGC is stabilized according to the output signal amount of the image sensor 4.

  The switching control / pre / post-switch data acquisition unit 8 holds the stable estimated illuminance value immediately after switching as “immediately after switching (Lb)”, and the expected sensitivity increase value calculation unit 12 together with “illuminance immediately before switching (La)”. “Illuminance immediately after switching (Lb)” is transmitted, and the “sensitivity increase expected value” is updated.

  In response to the request for updating the expected increase in sensitivity from the switching control / pre- and post-switching data acquisition unit 8, the expected increase in sensitivity value calculation unit 12 receives the difference value between the illuminance immediately before switching (La) and “immediately after switching (Lb)” (La -Lb). The latest 10 difference values (La-Lb) are stored, and when a new difference value (La-Lb) is obtained, the oldest data is deleted in order. The maximum value of the last 10 difference values (La-Lb) is set as the current “sensitivity increase expected value SU”.

  When the “sensitivity increase expected value SU” is updated, a “switching control reference value” of the switching control reference calculation unit 15 and a control mode update request of the control mode switching unit 9 are made based on the sensitivity increase expected value SU.

  The switching control reference calculation unit 15 receives the update request from the sensitivity increase expected value calculation unit 12 and updates the “switching control reference value”. The control mode switching unit 9 updates the control mode in response to an update request from the sensitivity increase expected value calculation unit 12.

  Next, based on the control flowchart of FIG. 2 and the color → monochrome switching threshold and monochrome → color switching threshold in the relationship between the expected increase in sensitivity SU and the gain amount (G) of AGC shown in FIG. A control method will be described.

  First, the mode determination unit automatically switches between two modes (normal control mode and data acquisition mode) of the automatic control mode of the infrared cut filter according to the sensitivity increase expected value SU.

  The automatic control of the infrared cut filter in the normal control mode is performed according to the following procedure. For the switching control in the normal control mode, two switching control reference values are provided for the illuminance estimation value L. The two control reference values are a reference value RVin for inserting the infrared cut filter and a reference value RVout for removing the infrared cut filter. During the normal control mode, the estimated illuminance value L and the control reference value are periodically compared. When this comparison is made, if the estimated illuminance value L is larger than the reference value RVin, an infrared cut filter is inserted, and if the estimated illuminance value L is smaller than the reference value RVout, the infrared cut filter is detached. In the normal control mode, the sensitivity increase expected value SU is updated every time this switching is performed.

In addition to the above control, RVin and RVout are dynamically changed according to the sensitivity increase expected value SU.
First, the variable control of RVout will be described. In an environment where the expected increase in sensitivity SU is small and the effect cannot be obtained much even when switching to monochrome photography, the reference value RVout is set to be small so that color photography is continued even when dark. Conversely, in an environment where the expected increase in sensitivity SU is large and a large effect can be obtained when switching to monochrome shooting, you can set a large RVout and switch to monochrome shooting while shooting to a certain level so that you can shoot images with good S / N. Like that.

  Next, variable control of RVin will be described. The variable control of RVin is also basically set to be large when the sensitivity increase expected value SU is large and to be small when the sensitivity increase expected value SU is small. However, in order to prevent the monochrome photography from being continued for an unnecessarily long time, the difference between RVout and RVin is changed so as to be smaller as the sensitivity increase expected value SU is smaller and larger as it is larger.

  FIG. 3 shows the relationship between the expected increase in sensitivity SU and the switching control reference values RVin / RVout in this embodiment. In the figure, the horizontal axis represents the expected increase in sensitivity SU, and the vertical axis represents the control reference value. In the imaging apparatus shown in the present embodiment, the relationship between the expected increase in sensitivity SU and the control reference value is changed to be linear.

  In the data acquisition mode, as described above, the infrared cut filter is attached and detached at a specific time managed by the timer in a very short time, and the sensitivity increase expected value SU is updated.

  With these controls, when there is little infrared light and there are few merits of switching to monochrome photography, it is possible to change the control standard so as to continue color photography without removing the infrared cut filter as much as possible. Furthermore, in an environment where there is almost no effect, automatic control can be autonomously restored when the amount of infrared light increases due to a change in the shooting environment after that. In addition, when there is a lot of infrared light and there are many merits of switching to monochrome photography, it is also possible to change the control reference so as to obtain an image with good S / N that does not rely excessively on the gain of AGC.

  The preferred embodiments of the present invention that can solve the above-described problems have been described with reference to the drawings. With the image pickup apparatus of the present invention, the installation operator does not need to make settings related to the control of the infrared cut filter, and even if the infrared light amount of the installation environment changes, the image pickup apparatus itself sets the set value. This eliminates the need for resetting. Therefore, the present invention has sufficient industrial applicability.

Block diagram of the present invention Overall processing flow of the present invention Control standard setting according to the expected increase in sensitivity

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lens 2 ... Diaphragm 3 ... Infrared cut filter 4 ... Imaging element 5 ... Signal processing part 6 ... Motor (for diaphragm)
7 ... Motor (for infrared cut filter)
8 ... Data acquisition unit 9 before and after switching control / switching 9 ... Control mode switching unit 10 ... Normal control mode switching timing control unit 11 ... Data acquisition mode switching timing control unit 12 ... Expected increase in sensitivity Calculation unit 13 ... Illuminance estimation calculation unit 14 ... Timer 15 ... Switching control reference calculation unit 16 ... Microcomputer

Claims (3)

An optical lens, an image sensor, an automatic gain controller (AGC) that performs feedback control so as to make the output signal level of the image sensor constant, a signal processor that converts the output signal of the AGC into a video signal, When the gain amount of the AGC is greater than or equal to the threshold A, an infrared cut filter is inserted between the optical lens and the image sensor, and when the gain amount of the AGC is less than or equal to the threshold B (B <A), the infrared cut filter A filter switching control unit that performs control to detach the optical lens and the imaging element from each other;
A filter insertion history unit that stores a difference in the AGC gain amount before and after the insertion of the infrared cut filter for a predetermined number of insertions, and updates AGC gain amount difference information for the predetermined number of insertions when the infrared cut filter is inserted;
A filter desorption history unit that stores a difference in the AGC gain amount before and after desorption of the infrared cut filter for a predetermined number of desorptions and updates AGC gain amount difference information for the predetermined desorption number during desorption of the infrared cut filter When,
A specific AGC gain amount difference I is selected from the AGC gain amount difference information stored in the filter insertion history portion, or a specific AGC gain amount difference information stored in the filter desorption history portion is selected. Sensitivity increase expectation value calculation section for selecting AGC gain amount difference II;
Switching control for correcting the threshold A based on the specific AGC gain amount difference I selected by the sensitivity increase expected value calculation unit or correcting the threshold B based on the specific AGC gain amount difference II A reference calculation unit;
An imaging apparatus comprising:   2. The imaging apparatus according to claim 1, wherein the threshold A, the threshold B, and the difference between the threshold A and the threshold B are increased as the difference in AGC gain amount selected by the expected increase in sensitivity value calculation unit is increased. An image pickup apparatus comprising: a switching control reference calculation unit. The imaging device according to claim 1,
A timer, and a data acquisition mode control unit that instructs the filter switching control unit to insert the infrared cut filter after the timer set time has elapsed,
When the AGC gain amount difference information at the time of filter insertion selected by the sensitivity increase expected value calculation unit is equal to or larger than a predetermined value, the filter switching control unit is driven, and the AGC gain amount difference information is less than the predetermined value. In this case, the data acquisition mode control unit includes a control mode switching unit that sets the timer.

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