JP3661756B2 - Automatic dimmer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic light control device. In particular, the present invention relates to an automatic light control device in an imaging device using an imaging device such as an artificial retina or a low resolution CCD.
[0002]
[Prior art]
Bathers are monitored in the bathroom, and when an accident such as a stroke occurs, a human body detection device that promptly notifies the householder or hot water is discharged from the shower or currant in response to the gesture of the bather. An imaging device using an artificial retina is used for a bathroom facility or the like for changing the set temperature of hot water in a bathtub. An imaging device using an artificial retina is also used in a virtual reality game machine or the like.
[0003]
[Problems to be solved by the invention]
However, in such an imaging device using an artificial retina, an image suitable for recognizing the object and its state can be obtained if the brightness of the object to be photographed or the photographing environment (illumination or natural light) changes. There was a possibility of false detection. For example, if you are monitoring a bather in the bathroom, if the sun is hidden in the cloud or if the sun comes out of the cloud, the amount of light inserted into the bathroom from the window will change abruptly, and the imaging device will have this brightness. There was a risk of malfunction or false detection.
[0004]
The present invention has been made in order to solve the above-described technical problems, and an object of the present invention is to provide an imaging device using an imaging device such as an artificial retina or a low-resolution CCD. It is to perform automatic light control by automatically adjusting the accumulation time so that an optimum image average value can always be obtained.
[0005]
[Means for Solving the Problems]
The automatic light control device according to claim 1 , wherein an image sensor, a calculation unit that calculates an image average value of each imaging point of the image sensor, and a relationship between an image accumulation time using a gain as a parameter and an image average value In the automatic light control device including the light control means having the characteristic curve to be expressed, the image pickup device picks up an image with a first gain and a predetermined image accumulation time corresponding to the gain, and the calculation means outputs the image pickup result. The first image average value is calculated based on the first gain characteristic, and the dimming means has a first gain characteristic so that the first image average value is obtained at a predetermined image accumulation time corresponding to the first gain. A curve is defined, and when the first image average value is within a predetermined range, the image accumulation time is adjusted to correspond to the optimum value of the image average value using the characteristic curve, and the first image average value Is smaller than the predetermined range, the imaging The child images with a second gain larger than the first gain and a predetermined image accumulation time corresponding to the gain, and the computing means computes a second image average value based on the imaging result, The dimming means determines a characteristic curve of the second gain so that the second image average value is obtained during a predetermined image accumulation time corresponding to the second gain, and an image is obtained using the characteristic curve of the gain. When the image accumulation time corresponding to the optimum value of the average value is calculated, and the first image average value is larger than the predetermined range, the image sensor has a third gain smaller than the first gain and the gain. The calculation means calculates a third image average value based on the imaging result, and the dimming means calculates the predetermined image storage corresponding to the third gain. So that the third image average value is reached at time. It determines the gain characteristic curve, and wherein computing the image accumulation time corresponding to the optimum value of the average picture value using the characteristic curve of the gain.
[0006]
The automatic light control device according to claim 2, wherein the light control means in the automatic light control device according to claim 1 compares the image average value calculated by the image average value calculation device with a desired value, A function of increasing the image accumulation time by a predetermined percentage if the average image value is smaller than a desired value, or decreasing the image accumulation time by a predetermined percentage if the image average value is larger than the desired value; It is characterized by having.
[0007]
[Action]
In the automatic light control device according to claim 1, the image storage time of the image sensor can be adjusted by the light control means so that the image average value becomes a desired value. Even when the brightness changes abruptly, automatic adjustment can be performed so as to obtain an optimal image average value (optimal imaging state). Furthermore, after determining the optimum gain with reference to the image average value, the image storage time of the image sensor is adjusted so that the image average value becomes a desired value at the gain. Can adjust the image accumulation time by switching the gain, and can cope with a large light quantity change. Further, by adjusting both the gain and the image accumulation time, it is possible to avoid a long processing time and a rough image.
[0008]
In the automatic light control device according to claim 2, when the image average value is smaller than a desired value, the image accumulation time is increased by a predetermined rate, or the image average value is smaller than the desired value. Is larger, the image accumulation time is decreased by a predetermined rate, so that the average image value can be finely adjusted.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a diagram illustrating a configuration of an imaging apparatus using an artificial retina. The image pickup unit 2 of the image pickup apparatus 1 includes an image detection unit 3, an imaging lens 4, a scanner 5, a multiplexer 6, and a scanner drive control unit 7 formed of a C-MOS array of 32 × 32 pixels (= 1024 pixels). It is configured. Here, the pixels of the image detection unit 3 are each expressed in 256 monochrome gradations (256 gradations from level 0 (black) to 255 (white)).
[0010]
In the imaging unit 2, the image in the bathroom is imaged on the image detection unit 3 by the imaging lens 4. The scanner 5 is driven and controlled by the scanner drive control unit 7 and controls each pixel column of the image detection unit 3 so as to sequentially enter a light receiving state (on state) at regular intervals. Photocurrents simultaneously output from the pixels in one column in the light receiving state are converted into serial data by the multiplexer 6, amplified by the amplifier 8, and then input to the image processing unit 9. The dimming unit 10 checks the average image value (brightness of the image) in the image processing unit 9 and adjusts the gain of the imaging device 1 by the amplifier 8 if the average image value is out of an appropriate range. The accumulation time of the image detection unit 3 is adjusted by the scanner drive control unit 7, and light adjustment is performed so that an image with appropriate brightness can be obtained. The determination unit 11 performs a determination according to the purpose of each imaging apparatus 1 (for example, determination as to whether or not there is a person in the bathroom), and outputs the determination result to the outside.
[0011]
In such an imaging apparatus 1, in order to obtain a highly accurate determination result, it is necessary to obtain an image with appropriate brightness as a premise. In the imaging device 1 using the artificial retina, the brightness of the image is expressed by the image average value S. The image average value S is an average value of gradations (256 gradations of 0 gradation (black) to 255 gradations (white)) in all 32 × 32 pixels constituting the image detection unit 3, It is also represented by a value from 0 to 255. Further, it is assumed that the optimum image average value (reference imaging level) in the imaging apparatus 1 is Q, and the allowable width of the image average value S is 2A. That is, the average image value S is
Q-A ≤ S ≤ Q + A
If it satisfies the above, it is allowed.
[0012]
This image average value S is determined by the gain G of the amplifier and the accumulation time τ of the image detection unit. In the case of a camera, the gain here corresponds to the aperture of the camera, and the accumulation time corresponds to the shutter speed of the camera. Therefore, in order to obtain an appropriate image average value of the image pickup apparatus, for example, it may be fixed to an appropriate gain and the accumulation time may be adjusted. Alternatively, it can be said that the gain may be adjusted to an appropriate gain by fixing the storage time to an appropriate value.
[0013]
However, when the accumulation time is fixed, if the accumulation time is lengthened, it takes time to obtain an image, and the response until output becomes worse. Further, if the accumulation time is shortened, the gain must be increased in the case of a dark image, and there is a problem that the image becomes rough when the gain is increased. On the other hand, when the gain is fixed, when the image is dark, the accumulation time becomes longer and the response until output is lowered. Therefore, in order to obtain an appropriate image average value S, it is necessary to adjust both the gain G and the accumulation time τ.
[0014]
Furthermore, the relationship between the gain G, the accumulation time τ, and the image average value S actually changes depending on the brightness of the object and the environment. As shown in FIG. 2, a curve (hereinafter referred to as a characteristic curve) representing the relationship between the accumulation time τ and the image average value S, where the horizontal axis is the accumulation time τ and the vertical axis is the image average value S, is the object and When the environment becomes brighter, it moves upward, and when it becomes darker, it moves downward. At the same time, the shape of the characteristic curve gradually changes as the brightness changes. When the gain increases, the characteristic curve representing the relationship between the accumulation time τ and the image average value S moves upward, and when the gain decreases, the characteristic curve moves downward. The method of changing the characteristic curve due to the difference in gain is also different every time the brightness of the object and the environment is different. However, if the relationship between the gain G, the accumulation time τ, and the image average value S is stored in the memory for each different brightness according to the brightness of the object and the brightness of the environment, the storage capacity of the memory is reduced. It becomes extremely large, and further, it takes a long processing time to determine an appropriate gain G and accumulation time τ.
[0015]
For this reason, in the imaging device 1 of the present invention, only one type of characteristic curve representing the relationship between the gain G and the accumulation time τ at the average brightness and the image average value S is stored in the memory in a table format, etc. When the brightness of the object and the environment changes, this characteristic curve is assumed to translate vertically without changing the shape. Then, automatic light control is performed so that an appropriate image average value S can be obtained by a method described below. In the following description, it is assumed that the gain G is adjusted in three stages of g1 (small), g2 (optimum gain), and g3 (large). Further, the accumulation time τ is taken on the horizontal axis, the image average value S is taken on the vertical axis, and the relationship between the accumulation time τ and the image average value S with respect to the gains g1, g2, and g3 is experimentally obtained. Actually, the relationship is as shown in FIG. However, in the following description, in order to make the description easy to understand, the relationship between the accumulation time τ and the image average value S at each of the gains g1, g2, and g3 is represented by a substantially straight line as shown in FIGS. Shall be.
[0016]
Hereinafter, the light control method in the imaging apparatus 1 will be described with reference to the image average value characteristic diagrams of FIGS. 3 to 5 and the flowchart of FIG. 6. Q is an optimum image average value, and the image average value S is (Q−A) <S <(Q + A).
Is acceptable, R is the upper limit value set above the upper limit Q + A of the appropriate average image value, and P is the lower limit value set below the lower limit Q-A of the appropriate average image value. It is a limit value.
[0017]
First, when the automatic dimming operation switch is turned on (step S1), the dimming unit 10 sets the gain to the normal optimum gain g2, sets the accumulation time τ to the default value X (for example, 35 ms), and Is captured and imaged (step S2). The reason why the gain is set to g2 first is to start with an optimum gain. Then, the image average value Sa at this time is measured, and it is checked whether or not the measured image average value Sa falls between the lower limit value P and the upper limit value R (P <Sa <R). (Step S3).
[0018]
When the measured image average value Sa is between the lower limit value P and the upper limit value R (in the case of YES at step S3), the image average is obtained with the gain g2 and the accumulation time τ = X as shown in FIG. The characteristic curve is determined so as to pass through the value S = Sa. For example, the characteristic curve read from the memory is translated up and down, and the characteristic curve is stopped when the value at the accumulation time τ = X on the curve of the gain g2 passes the image average value Sa (stored in the memory). Increase or decrease each table value in the function table by the same value).
[0019]
Next, as shown in FIG. 3, the accumulation time is determined from the curve of gain g2 among the characteristic curves so that the image average value S becomes the optimum value Q. Assuming that the accumulation time thus obtained is τb, the light control unit 10 sets the accumulation time to τb via the scanner drive control unit 7 (step S4).
[0020]
When the accumulation time is set to τb, the image is read again, the image average value S is obtained again, and it is checked whether or not the obtained image average value Sa is equal to the appropriate value Q (step S5). If the image average value Sa is not equal to the appropriate value Q, the process returns to step S4 again to reset the accumulation time τb.
[0021]
If it is determined in step S3 that the calculated image average value Sa does not satisfy P <Sa <R (NO), it is then determined whether the image average value Sa satisfies Sa ≦ P. (Step S6). When it is determined that the image average value Sa is equal to or lower than the lower limit value P, the gain is switched to g3, the accumulation time is set to the default value Y (for example, 68 ms) at the gain g3, and the image is captured again. (Step S7). Then, it is checked whether or not the image average value Sa is equal to the appropriate value Q (step S8).
[0022]
If it is determined in step S8 that the image average value Sa is not equal to the appropriate value Q (NO in step S8), the image average value S = Sa with a gain g3 and an accumulation time τ = Y as shown in FIG. Position the characteristic curve so that it passes through. Then, using this characteristic curve, the accumulation time is adjusted to τc so that the image average value S becomes equal to the appropriate value Q with the gain g3 (step S9).
[0023]
When the accumulation time is set to τc, the image is read again, the image average value is obtained again, and it is checked whether or not the obtained image average value Sa is equal to the appropriate value Q (step S10). If the average image value Sa is not equal to the appropriate value Q, the process returns to step S9 again to set the accumulation time τc.
[0024]
If it is determined in step S6 that the obtained image average value Sa does not satisfy Sa ≦ P and R ≦ Sa (NO in step S6), the gain is switched to g1 and stored. The time is set to a default value W (for example, 26 ms) at the gain g1, and an image is captured again and captured (step S11). Then, it is checked whether or not the image average value Sa is equal to the appropriate value Q (step S12).
[0025]
If it is determined in step S12 that the image average value Sa is not equal to the appropriate value Q (NO in step S12), the image average value S = Sa with a gain g1 and an accumulation time τ = W as shown in FIG. Position the characteristic curve so that it passes through. Then, using this characteristic curve, the accumulation time is adjusted to τd so that the image average value S becomes equal to the appropriate value Q with the gain g1 (step S13).
[0026]
When the accumulation time is set to τd, the image is read again to obtain the image average value again, and it is checked whether or not the obtained image average value Sa is equal to the appropriate value Q (step S14). If the image average value Sa is not equal to the appropriate value Q, the process returns to step S13 again to set the accumulation time τd.
[0027]
In this way, when it is determined that the image average value Sa has been adjusted to the appropriate value Q in any of steps S5, S8, S10, S12, and S14, shooting is continued with the gain G and the accumulation time τ. However, the image average value is measured and it is monitored whether the image average value Sa deviates from the appropriate range Q−A ≦ Sa ≦ Q + A (S16).
[0028]
If the ambient brightness suddenly changes during this monitoring, and the average image value Sa deviates from the appropriate range (Sa <P, Sa> R), the process returns to step S2 again, and after step S2 Repeat the process.
[0029]
In this imaging apparatus 1, when the brightness of the object or its environment changes suddenly (for example, when a bather is monitored in a bathroom, the sun suddenly hides in the clouds and suddenly If there is a significant change in the amount of light), the accumulation time τ is automatically adjusted so as to obtain an optimum image average value. If a greater change in the amount of light occurs, the gain G of the imaging device 1 is adjusted accordingly. Is adjusted so that the optimum accumulation time τ is obtained in accordance with the change in gain. Then, by automatically adjusting the light so that the optimum image average value is always obtained, it is possible to always perform a stable photographing operation and detection operation.
[0030]
(Second Embodiment)
In the first embodiment, the gain G and the accumulation time τ are automatically adjusted according to changes in the brightness of the object and the environment. However, the characteristic curve actually changes according to the brightness. Therefore, if the same characteristic curve is used regardless of the brightness as in the first embodiment, an error occurs between the actual optimum image average value and the image average value obtained by automatic light control. In some cases.
[0031]
Further, in the above embodiment, when the image average value Sa is between Q−A and Q + A (Q−A ≦ Sa ≦ Q + A), automatic adjustment is performed even if the image average value Sa is slightly deviated from the appropriate value Q. Light does not work.
[0032]
In the embodiment described below, even a small error is corrected by the method shown in the flowchart of FIG. That is, in this embodiment, the image average value Sa is measured (step S21), and the measured image average value Sa is equal to the appropriate value Q (or given a width, for example, 0.99Q <Sa <It is good also as 1.01Q.] It determines (step S22). If the determination results are equal, no processing is performed and the state is maintained as it is.
[0033]
If the measured value Sa is not equal to the appropriate value Q, it is then determined whether the measured image average value Sa is in the range of Q−A <Sa <Q + A (where Sa ≠ Q). If Sa.ltoreq.Q-A or Sa.gtoreq.Q + A, since this is an object of automatic dimming in the first embodiment, automatic dimming is performed by the method described in the first embodiment.
[0034]
On the other hand, if Q−A ≦ Sa ≦ Q + A (Sa ≠ Q), it is further divided into a case of Q−A ≦ Sa <Q and a case of Q <Sa ≦ Q + A (step S25). In this step, if Q−A ≦ Sa <Q, the accumulation time τ is multiplied by (1 + α) (step S26). As the accumulation time τ increases, the image average value increases accordingly. Here, α is a small positive number, for example, α = 0.1.
[0035]
If Q <Sa ≦ Q + A, the accumulation time τ is multiplied by (1−β) and the image is taken (step S27). When the accumulation time is reduced, the image average value is also reduced accordingly. Here, β is also a small positive number, for example, β = 0.1.
[0036]
Accordingly, even when the image average value Sa is slightly deviated from the appropriate value Q, the image average value asymptotically approaches the appropriate value q by repeating the steps S21 to S23 and S25 to S27. . Therefore, according to this embodiment, it is possible to make the average image value coincide with the appropriate value Q with high accuracy.
[0037]
【The invention's effect】
According to the automatic light control device according to claim 1, after determining the optimum gain with reference to the image average value, the image accumulation time of the image sensor is set so that the image average value becomes a desired value at the gain. In an apparatus using an image sensor such as an artificial retina or a low-resolution CCD, an optimum image average value can be obtained by adjusting the gain and image accumulation time even when there is a sudden change in the amount of light. Can do.
[0038]
According to the automatic light control device according to claim 2, when the image average value is smaller than the desired value, the image accumulation time is increased by a predetermined percentage, or when the image average value is larger than the desired value. Since the image accumulation time is decreased by a predetermined ratio, the average image value can be finely adjusted.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of an imaging apparatus using an artificial retina.
FIG. 2 is a diagram showing a relationship (measured data) between an accumulation time and an average image value using gain as a parameter;
FIG. 3 is a diagram illustrating an example of adjusting an image average value.
FIG. 4 is a diagram for explaining an adjustment example of an average image value when an object and an environment are dark.
FIG. 5 is a diagram for explaining an example of adjusting the average image value when the object and the environment are bright.
FIG. 6 is a flowchart showing a procedure of automatic light control processing in the imaging apparatus.
FIG. 7 is a flowchart showing a procedure of automatic light control processing according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Imaging device 2 Imaging part 3 Image detection part 7 Scanner drive control part 8 Amplifier 9 Image processing part 10 Light control part

Claims (2)

An image pickup device , a calculation means for calculating an image average value of each image pickup point of the image pickup device, and a light control means having a characteristic curve representing a relationship between an image storage time and an image average value using a gain as a parameter. In the automatic light control device,
The image pickup device picks up an image with a first gain and a predetermined image accumulation time corresponding to the gain, the calculation means calculates a first image average value based on the image pickup result, and the light control means When a characteristic curve of the first gain is determined so that the first image average value is obtained at a predetermined image accumulation time corresponding to the first gain, and the first image average value is within a predetermined range. Adjusts the image accumulation time to correspond to the optimum value of the average image value using the characteristic curve,
When the first image average value is smaller than a predetermined range, the imaging device captures an image with a second gain larger than the first gain and a predetermined image accumulation time corresponding to the gain, and the computing means Calculates the second image average value based on the imaging result, and the dimming means adjusts the second image average value so that the second image average value is obtained during a predetermined image accumulation time corresponding to the second gain. A gain characteristic curve of 2 and calculating an image accumulation time corresponding to the optimum value of the average image value using the gain characteristic curve;
When the first image average value is larger than a predetermined range, the imaging element captures an image with a third gain smaller than the first gain and a predetermined image accumulation time corresponding to the gain, and the computing means Calculates a third image average value based on the imaging result, and the dimming means adjusts the third image average value so as to be the third image average value at a predetermined image accumulation time corresponding to the third gain. 3. An automatic light control device characterized by determining a gain characteristic curve of 3 and calculating an image accumulation time corresponding to an optimum value of an average image value using the gain characteristic curve .   The light control means compares the image average value calculated by the image average value calculation means with a desired value, and when the image average value is smaller than the desired value, increases the image accumulation time by a predetermined rate, The automatic light control device according to claim 1, further comprising a function of reducing the image accumulation time by a predetermined ratio when the average image value is larger than a desired value.

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