KR100493001B1 - Exposure Control and Method of Low-Cost Camera Set - Google Patents

Abstract

Disclosed are an apparatus and method for adjusting exposure of a low-cost camera set. A solid-state image sensor and a correlated double sampler for converting and outputting an image captured by an amount of light adjusted in response to the first control signal to an analog signal, and a gain controller for outputting an analog image signal having a variable gain in response to a gain control value And a luminance signal extracting unit which extracts a luminance signal from the digital image signal converted from the output of the gain control unit, and limits the level of the extracted luminance signal to an upper limit and a lower limit, and integrates a luminance signal having a restricted level in the unit field. Amplifies the difference between the luminance level limiting and integrating unit for outputting the integrated value every field, the average value of the integrated value and the reference value, limits the amplified difference, and responds to the second control signal. By adding the gain control value of the previous field or the shutter control value of the previous field and limiting the added value again. A gain and shutter value generator for outputting as a gain control value or a shutter control value of the current field, and a timing generator for outputting a first control signal in response to the shutter control value of the current field; It is characterized in that it is generated corresponding to the level.

Description

Exposure Control Device and Method of Low-Cost Camera Set

The present invention relates to exposure adjustment of a low-cost camera set, and more particularly, to an exposure adjustment apparatus and method of a low-cost camera set that can adjust the exposure without a separate control unit in the low-cost camera set.

In general, a low-cost camera set means a multimedia personal computer (PC) and a surveillance camera.

1 is a block diagram of a conventional exposure control device, including a Charge Coupled Device (CCD) 10, a Correlated Double Sampler (CDS) 12, an automatic gain adjuster 14, an analog / An analog to digital converter (ADC) 16, a luminance signal generator 20, a comparator 22, an integrator 24, a register 26, a controller 28, and a timing generator 30 are included. Here, the luminance signal generator 20, the comparator 22, the integrator 24, and the register 26 shown in FIG. 1 are implemented as a single chip 18.

The charge coupling device 10 illustrated in FIG. 1 should always maintain a constant brightness of the captured image regardless of the brightness of the captured image. In other words, the screen should not be so bright that the amount of light in the image being picked up will be saturated, or conversely, it will not be too dark to recognize the shape of the image. As described above, adjusting the amount of incident light in order to maintain the brightness of the image captured at a constant level at all times is called exposure, and performing the exposure automatically according to the amount of incident light is called automatic exposure. Charge-coupled device 10 shown in FIG. 1, correlated double sampler 12, automatic gain regulator 14, analog / digital converter 16, timing generator 30, luminance signal generator 20, comparator 22 ), The integrator 24 and the register 26 will be described later, so the description of the operation is omitted here.

The controller 28, which is implemented as a microprocessor or a microcontroller, inputs an integrated value for each field during the unit field output from the register 26 to determine the brightness of the current image and corresponds to the determined result. The gain control value and the shutter control value are output to the automatic gain regulator 14 and the timing generator 30, respectively. At this time, the timing generator 30 inputs a shutter control value to output the first control signal to the charge coupled device 10, and the charge coupled device 10 measures the amount of light of an image captured in response to the first control signal. Adjust In addition, the automatic gain adjuster 14 adjusts the gain of the analog video signal output from the correlated double sampler 12 in response to the gain control value output from the controller 28, and analog-adjusts the analog video signal having the adjusted gain. Output to the digital converter 16.

On the other hand, the above-described conventional exposure adjustment device has to provide a separate control unit 28 outside the integrated circuit 18, in order to adjust the exposure of the camera. Therefore, the conventional exposure adjustment apparatus has a problem in that it is inappropriate to be applied to the low-cost camera set by increasing the cost required when configuring the camera set, when applied to the low-cost camera set.

An object of the present invention is to provide an exposure adjusting device of a low-cost camera set that can adjust the exposure of a low-cost camera set without a separate control unit.

Another object of the present invention is to provide an exposure adjustment method of a low-cost camera set that can adjust the exposure of a low-cost camera set without a separate control unit.

The exposure adjustment method of the low-cost camera set according to the present invention for achieving the above object is a solid-state imaging device for converting and outputting the image captured by the amount of light adjusted in response to the first control signal into an electrical signal, and the electrical signal A correlated double sampler for converting the signal into an analog video signal, gain control means for outputting the analog video signal having a variable gain in response to a gain control value, and converting the output of the gain control means into a digital video signal and outputting the digital video signal. An analog / digital converting means, a luminance signal extracting means for extracting a luminance signal from the digital video signal, and a level of the extracted luminance signal to a first upper limit and a first lower limit, Luminance level limiting means for outputting a luminance signal having a limited level, and An integration means for integrating in the above field and outputting the integrated value for each field, amplifying the difference between the average value and the reference value of the integrated value, limiting the amplified difference, and limiting the result to the second control signal. Gain and shutter value generating means in response to adding the gain control value of the previous field or the shutter control value of the previous field, and limiting the added value again and outputting the gain control value of the current field or the shutter control value of the current field; And a timing generating means for outputting the first control signal in response to the shutter control value of the current field, wherein the second control signal is generated corresponding to the level of the luminance signal.

According to another aspect of the present invention, there is provided a method for adjusting exposure of a low-cost camera set, the method including: (a) obtaining an analog video signal from an image to be captured, (b) extracting a luminance signal from the analog video signal, and (C) integrating the extracted luminance signal every field, (d) obtaining an average value of the integrated value during the current field, (e) subtracting the average value from a reference value, and subtracting (F) obtaining first and second multiplied results by multiplying the result by a first predetermined value and a second predetermined value, respectively, (g) limiting the first and second multiplied results, and (H) determining whether the level of the integrated value is greater than a predetermined level; and if the level of the integrated value is greater than the predetermined level, obtaining a shutter control value using the second multiplied result that is limited (i ) step (J) adjusting the amount of light of the image to be captured using the shutter control value, and determining whether the level of the integrated value obtained after the step (j) is approximated to the reference value; (1) obtaining a gain control value using the first multiplied result, if the level of the integrated value is less than or equal to the predetermined level or the level of the integrated value is not approximated to the reference value; Preferably, the step of adjusting the gain of the analog video signal using a gain control value (m).

Hereinafter, with reference to the accompanying drawings, the configuration and operation of the exposure control device of the low-cost camera set according to the present invention and the exposure adjustment method thereof will be described.

2 is a block diagram of an exposure adjustment apparatus for a low-cost camera set according to the present invention, wherein the solid-state imaging device 40, the correlated double sampler 42, the gain control section 44, the analog / digital conversion section 46, and the luminance signal It consists of an extracting section 50, a brightness level limiting section 52, an integrating section 54, a buffer 56, a gain and shutter value generating section 58, and a timing generator 60. Here, the luminance signal extractor 50, the luminance level limiter 52, the integrator 54, the buffer 56, the gain and shutter value generator 58 illustrated in FIG. 2 are implemented as a single chip 48. It can be seen that.

FIG. 3 is a flowchart for explaining an exposure adjustment method of a low-cost camera set performed in the apparatus shown in FIG. 2, in which a difference between an average value of an integrated luminance signal and a reference value is multiplied by predetermined values and then limited. Step (steps 62 to 74) and adjusting the shutter speed of the camera or the gain of the analog video signal according to the level of the integrated value (steps 76 to 94).

2, the correlated double sampler 42, the gain control section 44, the analog / digital converter 46, the luminance signal extracting section 50, the luminance level limiting section 52, Integrator 54, buffer 56, and timing generator 60 are charge coupled device 10, correlated double sampler 12, automatic gain regulator 14, analog / digital converter 16 shown in FIG. ), Luminance signal generator 20, comparator 22, integrator 24, register 26, and timing generator 30, respectively, and perform the same function.

The solid-state image pickup device 40 and the correlated double samplers 42 shown in FIG. 2 obtain an analog image signal from the captured image (step 62). That is, for example, the solid-state imaging device 40, which may be implemented as the charge coupling device 10 illustrated in FIG. 1, captures images with an amount of light adjusted in response to the control signal C1 output from the timing generator 60. An image is converted into an electrical signal, and the converted electrical signal is output to the correlated double sampler 42. At this time, the correlated double sampler 42 converts the electrical signal input from the solid-state imaging device 40 into an analog video signal, and outputs the converted analog video signal to the gain control section 44. At this time, the gain controller 44 varies the gain of the analog video signal output from the correlated double sampler 42 in response to the gain control value output from the gain and shutter value generator 58, and has an analog having a variable gain. The video signal is output to the analog / digital converter 46. The analog / digital converter 46 converts an analog video signal having a variable gain into a digital video signal and outputs the converted digital video signal to the luminance signal extractor 50.

On the other hand, after step 62, the luminance signal extractor 50 extracts the luminance signal from the digital image signal output from the analog / digital converter 46, and outputs the extracted luminance signal through the output terminal OUT. The extracted luminance signal is also output to the luminance level limiting unit 52 (step 64). Here, the level of the extracted luminance signal will be high overall if the currently captured image is a bright image, and conversely, if the image captured in the current field is a dark image.

In order to determine the brightness of the captured image by using this, after the 64th step, the integrating unit 54 integrates the luminance signal output from the luminance level limiting unit 52 in every field and stores the integrated value in the buffer 56. (Step 66). At this time, if the image captured in the current field is bright, the value of integrating the luminance signal during one field will be large. If the image captured in the current field is dark, the value of integrated luminance signal will be small.

However, before performing the integration, the luminance level limiter 52, which may be implemented as the comparator 22 shown in FIG. 1, limits the level of the luminance signal extracted by the luminance signal extractor 50 to the upper limit and the lower limit. And output to the integrating unit 54. That is, the brightness level limiter 52 limits the high brightness level above a certain level and the low brightness level below a certain level so that very bright or dark parts that may exist only in a very small portion of the image are not integrated. . As such, the integrated value is buffered in a buffer 56, which may be implemented as a register 26 shown in FIG. 1, and then output to the gain and shutter value generator 58. FIG.

After the sixty-sixth step, the gain and shutter value generator 58 amplifies the difference between the average value of the integrated value output from the buffer 56 and the reference value, limits the amplified difference, and sets the limiting result as the second control signal. In response to (C2), the gain control value 44 is added as the gain control value of the previous field or the shutter control value of the previous field, and the limit is added again to obtain the gain control value of the current field or the shutter control value of the current field. Output to the timing generator 60 (68th-82nd, 88th-92st steps), respectively.

FIG. 4 is a block diagram of an embodiment of the gain and shutter value generator 58 of FIG. 2 according to the present invention. The divider 102, the subtractor 104, and the first implement the average calculator 100. And second multipliers 106 and 108, first and second limiters 110 and 112, first and second AND gates 114 and 116, first and second adders 118 and 120. , Third and fourth limiters 122 and 124, first and second delay units 126 and 128, and dividers 130 and 132.

On the other hand, after step 66, the average value calculator 100 calculates the average value of the integrated values input from the buffer 56 through the input terminal IN during one field, and outputs the calculated average value to the subtractor 104 ( Step 68). To this end, the divider 102 implementing the average calculation unit 100 divides the value integrated during one field into the area where the integration is performed (size of the window), and divides the result of the division into the subtractor 104 as an average value. Output

After step 68, the subtractor 104 subtracts the average value from the reference value and outputs the subtracted result to the first and second multipliers 106 and 108, respectively (step 70). After step 70, the first and second multipliers 106 and 108 multiply the subtracted result output from the subtractor 104 by the first and second predetermined values G1 and G2, respectively, and multiply the result. Is output to the first and second limiters 110 and 112 as a result of the first and second multiplication, respectively (step 72). Here, the first and second multipliers 106 and 108 serve to make the subtracted result larger or smaller.

After step 72, the first limiter 110 limits the level of the first multiplied result, which is the output of the first multiplier 106, to an upper limit (2 ⁿ -1) and a lower limit (-2 ⁿ ) and limits the restricted level. Outputs the first multiplied result to the first AND gate 114, and the second limiter 112 may set the level of the second multiplied result that is the output of the second multiplier 108 to an upper limit (2 ⁿ −1). The lower limit (−2 ⁿ ) is limited, and a second multiplied result having a limited level is output to the second AND gate 116 (step 74).

FIG. 5 is a circuit diagram of an embodiment of the present invention of the control signal generator 180 for generating the second control signal C2 shown in FIG. 4, the comparators 150 and 152 and the third AND gate 154. It consists of.

After the seventy-seventh step, the control signal generator 180 shown in FIG. 5 determines whether the level of the value integrated in the integrating unit 54 is greater than a predetermined level, and according to the determined result, the control signal generator 180 generates the second control signal C2. Output to the first and second AND gates 114 and 116 (step 76). To this end, the comparator 150 shown in FIG. 5 compares whether the gain control value output from the divider 130 is equal to the "low" logic level "0" which is the lower limit of the third limiter 122, The result of the comparison is output to the third AND gate 154. At this time, if the shutter control value is not equal to the upper limit of the fourth limiter 124, the inverted value of the result compared in the comparator 150 and the result compared in the comparator 152 is ANDed, and The third AND gate 154, which outputs the second control signal C2, outputs the second control signal C2 having a "high" logic level. That is, if the level of the integrated value is greater than the predetermined level, the second control signal C2 of the "high" logic level is output, and if the level of the integrated value is less than or equal to the predetermined level, the second control of the "low" logic level The signal C2 is output. Therefore, when the gain control value reaches the lower limit (0) of the third limiter 122, the exposure is adjusted to the shutter control value in response to the second control signal C2 of the "high" logic level.

If the level of the value integrated in the integrator 54 is equal to or less than the predetermined level, the gain of the analog video signal is adjusted to perform exposure adjustment of the camera set (steps 88 to 94). That is, in this case, since the second control signal C2 of the "low" logic level is generated as in the above-described example, the output of the first limiter 110 is output to the adder 118, and the second limiter 112 is output. The output of is not output to the adder 120. Therefore, the adder 118 is configured to control the gain of the third limiter 122 which is a gain control value of the output of the first limiter 110 output from the first AND gate 114 and the previous field output from the first delay unit 126. The output is added, and the added result is output to the third limiter 122 (step 88). Here, the first delay unit 126 is a digital delay element that delays the output of the third limiter 122 by a predetermined time and outputs the delayed value to the adder 118 as a gain control value of the previous field. do. After the 88 th step, the third limiter 122 limits the level of the value output from the first adder 118 to the upper limit [(2 ^m −1) × P] and the lower limit [0], and has an adder having a limited level. The output of 118 is output as a gain control value of the current field (step 90). In this case, the result of limiting in the third limiter 122 may be divided by the divider 130 to a predetermined value P, and the divided value may be output as a gain control value (step 92). Here, the divider 130 serves to prevent the integrated value from shaking when the integrated value is close to the reference value. After step 92, the gain controller 44 shown in FIG. 2 varies the gain of the analog video signal in response to the gain control value output from the divider 130, and analog video for the next field having the variable gain. The signal is output to the analog / digital converter 46 (step 94). Therefore, the luminance signal extracted from the digital video signal is integrated in the integrating section 54 for the next field.

FIG. 6 is a view for explaining a process in which an integrated value (or integrated value) is approximated to a reference value, wherein the horizontal axis represents time t and the vertical axis represents integral values, respectively.

In the above-described steps 88 to 94, if the integral value of the current field is much lower than the reference value, the result subtracted by the subtractor 104 will be very large in the positive direction. At this time, as the subtracted result is added to the gain control value of the previous field, the gain control value is greatly increased to increase the gain of the analog video signal. Therefore, the level of the overall luminance signal is increased, so that the screen is shown brightly. Through this process, when a brighter image signal is input to the next field, the subtracted result is smaller than the previous subtracted result, so that the change width of the gain control value is smaller. That is, as shown in FIG. 6, when the subtracted result is large, the gain control value also changes largely so that the integral value approaches the reference value rapidly. In detail, the integral value approaches the reference value. On the contrary, when the input image is too bright and the integral value is larger than the reference value, the subtracted result is displayed in the negative direction and the gain control value is reduced, thereby darkening the screen. In this case, when the magnitude of the subtracted result is large, when the integral value approaches the reference value exponentially and gradually approaches the reference value, the integral value slowly approaches the reference value.

On the other hand, if the level of the integrated value for the current field is larger than the predetermined level, that is, the level of the integrated value for the current field is too large, the shutter speed of the camera is adjusted, i.e., the exposure is adjusted with the shutter control value ( Steps 78 to 84). Referring to this, as described above, the second control signal C2 having the logic level "high" is generated so that the output of the first limiter 110 is not output to the adder 118 and the output of the second limiter 112. The second AND gate 116 is output to the second adder 120. Accordingly, the second adder 120 adds the second multiplied result limited by the second limiter 112 to the shutter control value of the previous field and outputs the added result to the fourth limiter 124 (78). step). At this time, the second delay unit 128 is a digital delay element similar to the above-described first delay unit 128, and delays the value output from the fourth limiter 124 by a predetermined time and sets the delayed value as the shutter of the previous field. It outputs to the 2nd adder 120 as a control value. After the 78th step, the fourth limiter 124 limits the level of the added result output from the second adder 120 to the upper limit q and the lower limit r, and limits the added result having the limited level to the current field. Is output as the shutter control value (step 80). At this time, when the integrated value is close to the reference value, the divider 132 may limit the result of the limiting value of the fourth limiter 124 to prevent the shaking of the integral value between the reference values. Division may be performed and the divided result may be output as a shutter control value (step 82). After step 82, the timing generator 60 illustrated in FIG. 2 generates the first control signal C1 generated by using the shutter control value output from the gain and shutter value generator 58. As described above, the solid-state imaging device 40 picks up an image with the amount of light adjusted in response to the first control signal C1 (step 84).

After step 84, the control signal generator 180 shown in FIG. 5 determines whether the level of the value integrated in the integrator 54 is close to the reference value (step 86). To this end, the comparator 152 shown in FIG. 5 compares whether the shutter control value output from the divider 132 shown in FIG. 4 is equal to the upper limit q of the fourth limiter 124. If the shutter control value is equal to the upper limit q, that is, when the shutter control value has increased to the maximum value but the integral value has not reached the reference value, the second control signal C2 transitions to the "low" logic level. The exposure adjustment of the camera is then performed by adjusting the gain of the analog signal.

In the above-described exposure adjustment according to the present invention, the shutter speed control of the camera and the gain adjustment of the analog image signal cannot be simultaneously performed. Therefore, for the exposure adjustment, the exposure adjustment by the shutter control value is to reduce the overall amount of light by shortening the time that charges are accumulated in the solid-state image pickup device, so that the gain adjustment of the analog image signal is basically performed first. However, if the integral value still does not reach the reference value even though the gain control value is reduced to the lower limit 0 of the third limiter 122 because the level of the luminance signal is too high, the second control signal C2 is brought to the "high" logic level. do. Therefore, since the shutter control value is reduced and the time for charge accumulation in the solid-state imaging device 40 is shortened, the integrated value of the image can approach the reference value. At this time, when the dark image is taken again and the integral value of the luminance signal is lowered, the shutter control value is increased again, and the time for which charges are accumulated in the solid-state image sensor 40 becomes long, so that the screen becomes bright. However, as described above, when the shutter control value increases to the maximum value q but fails to reach the reference value, the second control signal C2 again becomes the "low" logic level, and the gain control value is used from this point on. The exposure of the camera is adjusted.

As described above, the exposure adjustment apparatus and method of the low-cost camera set according to the present invention is different from the conventional exposure adjustment apparatus shown in FIG. 1 in which the control unit 28 is provided outside the integrated circuit 18. (48) Since the simple gain and shutter value generation unit 58 can be incorporated therein, the cost required for constructing the camera set can be reduced, so that the low cost camera set can be suitably applied.

1 is a block diagram of a conventional exposure adjustment apparatus.

2 is a block diagram of an exposure adjustment apparatus of a low-cost camera set according to the present invention.

3 is a flowchart for explaining an exposure adjustment method of a low-cost camera set performed in the apparatus shown in FIG. 2.

4 is a block diagram of an embodiment according to the present invention of the gain and shutter value generator shown in FIG. 2.

FIG. 5 is a circuit diagram of an embodiment of the present invention of a control signal generator for generating the second control signal shown in FIG. 4.

6 is a diagram for explaining a process of integrating an approximation to a reference value.

Claims (8)

A solid-state imaging device for converting an image captured by an amount of light adjusted in response to the first control signal into an electrical signal and outputting the electrical signal; A correlated double sampler for converting the electrical signal into an analog video signal; Gain control means for outputting said analog video signal having a variable gain in response to a gain control value; Analog / digital conversion means for converting the output of said gain control means into a digital video signal and outputting it; Luminance signal extraction means for extracting a luminance signal from the digital video signal; Luminance level limiting means for limiting the level of the extracted luminance signal to a first upper limit and a first lower limit, and outputting a luminance signal having a limited level; Integrating means for integrating the luminance signal having the limited level in a unit field and outputting the integrated value every field; Amplifying the difference between the average value of the integrated value and the reference value, limiting the amplified difference, and adding the limiting result to the gain control value of the previous field or the shutter control value of the previous field in response to the second control signal, Gain and shutter value generating means for limiting the added value again and outputting the gain control value of the current field or the shutter control value of the current field; And Timing generating means for outputting said first control signal in response to said shutter control value of a current field, And the second control signal is generated corresponding to the level of the luminance signal. The method of claim 1, wherein the gain and shutter value generating means Average value calculating means for calculating an average value of the integrated values; Subtraction means for subtracting the average value from the reference value; First multiplication means for multiplying the subtracted result by a first predetermined value; Second multiplication means for multiplying the subtracted result by a second predetermined value; A first limiter for limiting the level of the result multiplied by the first multiplication means to a second upper limit and a second lower limit; A second limiter for limiting the level of the result multiplied by the second multiplication means to the second upper limit and the second lower limit; First logical AND means for ANDing and outputting the second control signal inverted with the output of the first limiter; Second logical AND means for performing an AND operation on the output of the second limiter and the second control signal; First adding means for adding the output of the first AND product and the gain control value of a previous field and outputting the added result; Second adding means for adding the output of said second AND product and said shutter control value of a previous field and outputting the added result; A third limiter for limiting the level of the result added by the first adding means to a third upper limit and a third lower limit, and outputting the added result having the restricted level as the gain control value of the current field; A fourth limiter for limiting the level of the result added by the second adding means to a fourth upper limit and a fourth lower limit, and outputting the added result having the restricted level as the shutter control value of the current field; First delay means for delaying an output of the third limiter by a predetermined time and outputting the gain control value of a previous field; And And a second delay means for delaying the output of said fourth limiter by said predetermined time and outputting it as said shutter control value of a previous field. The method of claim 2, wherein the gain and shutter value generating means First dividing means for dividing the output of the third limiter by a third predetermined value and outputting the divided result as the gain control value of the current field; And And a second dividing means for dividing the output of the fourth limiter as a fourth predetermined value and outputting the divided result as the shutter control value of the current field. The exposure adjusting device of claim 2, wherein A first comparator for comparing whether the gain control value of the current field is equal to the third lower limit and outputting a result of the comparison; A second comparator comparing the shutter control value of the current field with the fourth upper limit and outputting a result of the comparison; And And a third logical multiplication means for logically multiplying the inverted value of the result compared by the second comparator and the result compared by the first comparator and outputting the result of the logical multiplication as the second control signal. Exposure adjuster for low-cost camera sets. 2. An apparatus according to claim 1, wherein said luminance signal extracting means, said luminance level limiting means, said integrating means and gain and shutter value generating means are integrated. In the exposure adjustment method of a low-cost camera set, (a) obtaining an analog image signal from an image to be captured; (b) extracting a luminance signal from the analog video signal; (c) integrating the extracted luminance signals every field; (d) obtaining an average of the integrated values during the current field; (e) subtracting said average value from a reference value; (f) multiplying the subtracted result by a first predetermined value and a second predetermined value to obtain first and second multiplied results; (g) limiting the first and second multiplied results; (h) determining whether the level of the integrated value is greater than a predetermined level; (i) if the level of the integrated value is greater than the predetermined level, obtaining a shutter control value using the second multiplied result; (j) adjusting the amount of light in the captured image using the shutter control value; (k) determining whether the level of the integrated value obtained after step (j) is close to the reference value; (l) obtaining a gain control value using the limited first multiplied result if the level of the integrated value is less than or equal to the predetermined level or the level of the integrated value is not approximated to the reference value; And (m) adjusting the gain of the analog video signal using the gain control value. The method of claim 6, wherein step (i) (i1) adding the limiting second multiplied result to the shutter control value of a previous field; (i2) limiting the result added in step (i1); and (i3) dividing the result of the limit in step (i2) by a first predetermined value to obtain the shutter control value of the current field. The method of claim 7, wherein step (l) (l1) adding the limited first multiplied result to the gain control value of a previous field; (l2) limiting the result added in step (l1); And and (l3) dividing the result limit in step (l2) by a second predetermined value to obtain the gain control value of the current field.