JP4261416B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that performs image recognition using an optimal digital image signal.

In the prior art, several methods have been proposed for obtaining a digital image signal with good contrast when performing image processing.
One is that the maximum and minimum luminance values are obtained from the entire frame image or a part of the area, and the image signal of the next frame is A / D converted based on the obtained maximum and minimum values. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 9-16747

  In the image processing apparatus as described above, since the region for obtaining the maximum value and the minimum value of the luminance can be limited to the periphery of the object, the contrast can be improved without being influenced by the luminance value of an unnecessary part. When the difference in brightness around the object is large and the difference in brightness of the necessary object is small, the effect cannot be obtained.

  For example, when a white line is recognized from an image taken near the tunnel entrance, the brightness difference between the inside and outside of the tunnel is large, and A / D conversion is performed based on the maximum and minimum brightness values obtained from the entire frame image. However, the contrast is not improved because the level is white and black. In addition, if the area for obtaining the maximum and minimum luminance values is limited to the inside or outside of the tunnel, the contrast in the area is improved and the white line in the area can be easily recognized, but the contrast outside the area is deteriorated. However, white line recognition becomes difficult.

  In addition, a moving image such as an in-vehicle camera image may be a completely different image after one frame, so even if A / D conversion is performed using data one frame before, an image with good contrast is obtained. There was a problem that a signal could not be obtained.

  Furthermore, even when the brightness of the shooting range changes suddenly, there is a problem that an image signal with good contrast cannot be obtained even if A / D conversion is performed using data of the previous frame. .

  The present invention has been made to solve such a problem, and an image having a good contrast suitable for image recognition even when the brightness difference around the object is large or the brightness of the photographing range changes suddenly. An object of the present invention is to provide an image processing apparatus capable of obtaining a signal and performing highly accurate image recognition.

  In the image processing apparatus according to the present invention, an A / D conversion processing means for converting an analog image signal obtained by an imaging means for scanning and photoelectrically converting incident light into a digital image signal, and the A / D conversion processing means In the image processing apparatus having the image processing means for performing the image processing on the digital image signal obtained in step (1) and extracting the object, the range for performing the A / D conversion in the A / D conversion processing means is determined. A / D reference value setting means is provided for setting a reference value to be referenced for each predetermined scanning line number range smaller than the number of scanning lines corresponding to one frame of the image.

  According to the present invention, even when there is a large difference in brightness around the object or when the brightness of the shooting range changes suddenly, an image signal with good contrast suitable for image recognition is obtained, and highly accurate image recognition is performed. An image processing apparatus capable of performing the processing can be provided.

Embodiment 1 FIG.
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the image processing apparatus according to the first embodiment. FIG. 2 is an explanatory diagram illustrating an example of a forward traveling image according to the first embodiment. FIG. 3 is a characteristic diagram showing a luminance histogram in the regions (a), (b), and (c) of FIG.

In FIG. 1, an imaging apparatus 1 photoelectrically converts incident light and outputs an analog image signal. The A / D reference voltage setting unit 2 sets a reference voltage that is referred to during A / D conversion. The A / D conversion processing device 3 converts an analog image signal into a digital image signal. The image recognition processing device 4 performs image recognition using the digital image signal obtained by the A / D conversion processing device 3.
The imaging device 1 is configured by a CCD camera for CCTV (Closed_Cicuit_Television) or the like, and incident light incident on photoelectric conversion elements such as CCD elements arranged in a matrix is subjected to photoelectric conversion such as CCD elements arranged in the matrix. An analog image signal is output by performing horizontal scanning and vertical scanning for each element and performing photoelectric conversion.

An analog image signal obtained by the imaging device 1 is input to the A / D reference voltage setting unit 2 and the A / D conversion processing device 3.
The A / D reference voltage setting unit 2 sets a reference voltage that is referred to by the A / D conversion processing device 3 for each scanning line based on the luminance level of the input analog image signal. The reference voltage is a voltage for determining a range in which A / D conversion is performed, and is an upper limit reference voltage (High) for determining the upper limit of the range and a lower limit reference voltage (low) for determining the lower limit of the range. There is. The A / D reference voltage setting unit 2 sets an A / D reference voltage suitable for each scanning line.

Here, FIG. 2 shows an example of a forward traveling image, where the long-distance area is (a), the middle-distance area is (b), and the short-distance area is (c).
Normally, the farther away the reflected light from the road surface, the closer to the total reflection, the closer the brightness value between the road surface and the white line becomes, and the contrast decreases.

Luminance histograms in the regions (a), (b), and (c) of FIG. 2 are shown in FIGS. 3 (a), (b), and (c), respectively. L is the average value of the road surface luminance histogram, and H is the average value of the white line luminance histogram.
As can be seen from this histogram, the difference in luminance between the road surface and the white line differs depending on the forward distance. Therefore, the upper and lower reference voltages of A / D conversion are set according to the area, respectively, for the scanning lines corresponding to area (a), Ha, La, and similarly for area (b), Hb, Lb, (c) area. Is set to Hc, Lc.

In the first embodiment, the upper and lower reference voltages in the A / D conversion process executed by the A / D conversion processing device 3 are set for each scanning line.
In the first scanning line a1 belonging to the region (a) 113, the upper and lower reference voltages Ha to which the upper and lower reference voltages for performing A / D conversion for the scanning line a1 are adapted to the contrast in the region (a). The lower limit reference voltage La is set.
In the second scanning line a2 belonging to the region (a) 113, the upper and lower reference voltages for applying the upper and lower reference voltages for the A / D conversion for the scanning line a2 to the contrast in the region (a). The voltage Ha and the lower limit reference voltage La are set.
Further, even in the third scanning line a3 belonging to the region (a) 113, the upper and lower reference voltages for applying the upper and lower reference voltages for the A / D conversion for the scanning line a3 to the contrast in the region (a). The voltage Ha and the lower limit reference voltage La are set.
In this way, in the 1st to nth scanning lines a1 to an belonging to the region (a) 113, the upper and lower reference voltages for performing A / D conversion on these scanning lines a1 to an are set to the scanning line 1. Each is set to be an upper limit reference voltage Ha and a lower limit reference voltage La adapted to the contrast in the region (a) for each of an. Here, an indicates the number of scanning lines belonging to the region (a) 113 reaching several tens to hundreds.

  Similarly to the region (a) 113, the region (b) 114 and the region (c) 115 also use the reference voltages Hb and Lb and the reference voltages Hc and Lc, respectively. D conversion is executed.

As described above, the A / D conversion processing device 3 performs A / D conversion with reference to different A / D reference voltages for the scanning lines belonging to the region (a), the region (b), and the region (c).
As a result, the brightness difference between the white line and the road surface corresponds to the entire range of the A / D range in any region. Therefore, even if the brightness difference around the object varies depending on the region, the brightness of other regions or scanning lines Regardless, it is possible to obtain an image signal with good contrast.

  In the image recognition processing device 4, since the digital image signal obtained by the A / D conversion processing device 3 performs image processing such as binarization and edge extraction to recognize the object, the recognition rate is improved as compared with the conventional case. Reliable results can be obtained.

  In the above example, the area is divided into three, but the area is not particularly divided into three. For example, the upper and lower reference voltages may be set according to the forward distance, or may be set for each scanning line using a storage means such as a data table.

  In the above example, A / D conversion is described with reference to different A / D reference voltages for each scanning line belonging to the regions (a), (b), and (c). A / D conversion may be performed by the A / D conversion processing device 3 by setting different upper and lower reference voltages for each scanning line.

  According to the first embodiment of the present invention, an image pickup means including an image pickup apparatus 1 configured by a CCD camera or the like that scans and photoelectrically converts incident light, and an analog image signal obtained by the image pickup means including the image pickup apparatus 1. A / D conversion processing means comprising an A / D conversion processing device 3 for converting the signal into a digital image signal, and a digital image signal obtained by the A / D conversion processing means comprising the A / D conversion processing device 3 In an image processing apparatus having an image processing means comprising an image recognition processing apparatus 4 for performing image processing and extracting an object, A / D conversion in the A / D conversion processing means comprising the A / D conversion processing apparatus 3 A reference value such as a reference voltage composed of the upper limit reference voltages Ha, Hb, Hc and the lower limit reference voltages La, Lb, Lc, which are referred to in order to determine the range for performing the operation, is set for each scanning line or predetermined Set for each predetermined scanning line number range smaller than the number of scanning lines corresponding to one frame of the image, for example, for each of a plurality of scanning lines belonging to each of the regions (a), (b), and (c). A / D reference value setting means comprising an A / D reference voltage setting unit 2 is provided for image recognition even when the brightness difference around the object is large or when the brightness of the shooting range changes suddenly. It is possible to provide an image processing apparatus capable of obtaining a suitable image signal with good contrast and performing highly accurate image recognition.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a block diagram showing the configuration of the image processing apparatus according to the second embodiment. FIG. 5 is an explanatory diagram showing the operation in the second embodiment. FIG. 6 is an explanatory diagram showing the operation in the second embodiment. FIG. 7 is a connection diagram showing an example of a circuit for realizing the maximum peak value detecting means and the minimum peak value detecting means in the second embodiment. FIG. 8 is a connection diagram showing an example of a circuit for realizing the peak value holding means in the second embodiment.
In the second embodiment, the configuration other than the specific configuration described here has the same configuration contents as the configuration in the first embodiment described above, and exhibits the same operation. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 4 is an example of an image processing apparatus provided with A / D reference value setting means for setting a luminance peak value detected for each scanning line as a reference voltage.

In FIG. 4, the imaging apparatus 1 photoelectrically converts incident light and outputs an analog image signal. The A / D reference voltage setting unit 2 sets a reference voltage that is referred to during A / D conversion. The A / D conversion processing device 3 converts an analog image signal into a digital image signal. The image recognition processing device 4 performs image recognition using the digital image signal obtained by the A / D conversion processing device 3.
In the second embodiment, the A / D reference value setting means including the A / D reference voltage setting unit 2 includes a maximum peak value detection circuit 10, a maximum peak value holding circuit 11, a minimum peak value detection circuit 12, and a minimum peak. It is composed of a value holding circuit 13.

  FIG. 5 and FIG. 6 are explanatory diagrams of the operation in the second embodiment, and the maximum value 212 of the luminance signal 211 and the minimum value 213 of the luminance signal 211 are shown for the luminance signal 211 in a certain nth scanning line. ing.

The maximum peak value detection circuit 10 detects the upper limit value of the luminance level during one scanning period, that is, the maximum voltage value, from the analog image signal obtained by the imaging device 1. The detected maximum voltage value is held by the maximum peak value holding circuit 11 for one scanning period, and the held voltage value is input to the upper limit reference voltage (High) of the A / D conversion processing device 3. The minimum peak value detection means circuit detects the lower limit value of the luminance level during one scanning period, that is, the minimum voltage value, from the analog image signal obtained by the imaging device 1. The detected minimum voltage value is held by the minimum peak value holding circuit 13 for one scanning period, and the held voltage value is input to the lower limit reference voltage (Low) of the A / D converter 3.
In the A / D conversion device 3, the input video signal is A / D converted between the upper limit reference voltage (High) set by the A / D reference voltage setting unit 2 and the lower limit reference voltage (Low). Then, a digital image signal using gradation effectively is output for each scanning line.

This state is shown in FIGS. FIG. 5 is a schematic diagram of luminance signal output in the nth scanning line.
According to the above-described operation, the maximum peak value detection circuit 10 detects the maximum value 212 and the minimum peak value detection circuit 12 detects the minimum value 213. Therefore, by setting these two values as the upper and lower limit reference voltages, the contrast between the white line and the road surface can be maximized, and the reference voltage can be set for each scanning line as compared with the method described in the first embodiment. Therefore, it becomes possible to adapt to sudden changes in video.
However, since the maximum value and the minimum value can be detected only after searching all the signals for one line, the set value is delayed by 1H.

  This is shown in FIG. In FIG. 6, the maximum value n−1 and the minimum value n−1 detected by the A / D conversion reference voltage setting unit 2 for the n−1 line are set at the timing at which the imaging device 1 outputs the nth line. Since these two values are held for 1H period, A / D conversion is performed on the n-line signal with the maximum voltage value and the minimum voltage value of the n-1 line. Since video has the property that the similarity between adjacent scanning lines within one frame is high, there is a problem unless there is a sudden change in video with a high spatial frequency such that the brightness differs for each scanning line in the above setting method. It can respond without any problems.

The maximum peak value detection circuit 10 and the minimum peak value detection circuit 12 can be realized with a simple circuit configuration shown in FIG. The clear signal in the figure can be easily realized by diverting the horizontal synchronization signal.
Further, the peak value holding circuits 11 and 13 can also be realized with the simple circuit configuration shown in FIG. 8, and the horizontal synchronizing signal can also be used for On / Off of the switches in the figure.
In the above example, each scanning line has been described, but a plurality of scanning lines may be used.

  According to the second embodiment of the present invention, in the configuration of the first embodiment, the A / D reference value setting means including the A / D reference voltage setting unit 2 is obtained by the imaging means including the imaging device 1. The maximum peak detection means comprising a maximum peak detection circuit 10 for detecting the maximum peak value of luminance for at least one scanning line for the analog image signal, and at least one scanning line for the analog image signal obtained by the imaging means comprising the imaging device 1 Minimum peak value detection means comprising a minimum peak value detection circuit 12 for detecting a minimum peak value of luminance for each scanning line, that is, for each scanning line or each scanning line, and maximum peak holding for holding each peak value for a predetermined time A maximum peak value holding means comprising a circuit 11 and a minimum peak value holding means comprising a minimum peak value holding circuit 13; The maximum peak value and the minimum peak value held by the maximum peak value holding means comprising the maximum peak holding circuit 11 and the minimum peak value holding means comprising the minimum peak value holding circuit 13 are obtained from the A / D converter 3. Since the reference values such as the upper limit reference voltage and the lower limit reference voltage of the A / D conversion processing means are set as appropriate, the reference value of the A / D conversion processing means is appropriately set, so that the brightness difference around the object Even when the image quality is large or when the brightness of the shooting range changes suddenly, it is possible to provide an image processing apparatus capable of obtaining an image signal with good contrast suitable for image recognition and performing highly accurate image recognition.

Embodiment 3 FIG.
A third embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a block diagram showing the configuration of the image processing apparatus according to the third embodiment. FIG. 10 is an explanatory diagram showing the operation in the third embodiment.
In the third embodiment, the configuration other than the specific configuration described here has the same configuration contents as the configurations in the first and second embodiments described above and exhibits the same operation. It is. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 9 shows A / D reference value setting means for setting a peak value of luminance detected for each scanning line as a reference voltage, and delay means for delaying an analog image signal input to the A / D conversion processing means by one scanning period. 1 is an example of an image processing apparatus provided.

In FIG. 9, the imaging device 1 photoelectrically converts incident light and outputs an analog image signal. The A / D reference voltage setting unit 2 sets a reference voltage that is referred to during A / D conversion. The A / D conversion processing device 3 converts an analog image signal into a digital image signal. The image recognition processing device 4 performs image recognition using the digital image signal obtained by the A / D conversion processing device 3.
In the third embodiment, the A / D reference value setting means including the A / D reference voltage setting unit 2 includes a maximum peak value detection circuit 10, a maximum peak value holding circuit 11, a minimum peak value detection circuit 12, and a minimum peak. It is composed of a value holding circuit 13. Then, a delay means comprising a delay circuit 5 is provided.

The delay means including the delay circuit 5 delays the analog image signal obtained from the imaging device 1 by one scanning period.
The analog image signal delayed by one scanning period by the delay circuit 5 is input to the A / D conversion device 3. The A / D converter 3 refers to the reference voltage set by the A / D reference voltage setting unit 2 and performs A / D conversion of the analog image signal input from the delay circuit 5.

This is shown in FIG. For example, it is assumed that the output of the nth line of the imaging device 1 is simultaneously input to the A / D reference voltage setting unit 2 and the delay circuit 5.
The A / D reference voltage setting unit 2 detects the maximum value n and the minimum value n in the period of 1H. While the imaging apparatus 1 outputs the (n + 1) th line, the maximum peak value holding circuit 11 and the minimum peak value holding circuit 13 hold the values.
On the other hand, in the delay circuit 5, when the imaging device 1 outputs the signal of the (n + 1) th line, the signal of the nth line delayed by 1H is output. Therefore, the input to the A / D conversion processing device 3 has the upper limit reference voltage (High) as the maximum value n, the lower limit reference voltage (Low) as the minimum value n, and the signal input as the video value sign of n lines.
In other words, the analog image signal used for setting the reference voltage and the analog image signal used for A / D conversion can be performed on the same scanning line, so even if the screen changes suddenly, the scanning line A digital image signal with good contrast can be obtained every time.
The delay circuit 5 can be easily realized using a CCD delay element or the like.
In the above example, each scanning line has been described. In this case, the delay value of the delay circuit 5 is a delay amount for the plurality of scanning lines.

  According to the third embodiment of the present invention, in the configuration of the first or second embodiment, the analog image signal used for A / D conversion by the A / D conversion processing means including the A / D conversion device 3 is as follows. Since the delay means composed of the delay circuit 5 delays at least one scanning period, the analog image signal is appropriately processed so that the brightness of the photographing range changes suddenly when the brightness difference around the object is large. Even in such a case, it is possible to provide an image processing apparatus capable of obtaining an image signal with good contrast suitable for image recognition and performing image recognition with high accuracy.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a block diagram showing the configuration of the image processing apparatus according to the fourth embodiment. FIG. 12 is an explanatory diagram showing the operation in the fourth embodiment.
In the fourth embodiment, the configuration other than the specific configuration described here has the same configuration contents as those in the first to third embodiments described above, and has the same operation. Is. In the drawings, the same reference numerals indicate the same or corresponding parts.

In the second embodiment, the maximum value and the minimum value are obtained from the analog signal. In the fourth embodiment, an example in which the digital signal is used will be described.
FIG. 11 shows an example of an image processing apparatus including A / D reference value setting means for performing A / D conversion with reference to a predetermined reference voltage and setting the reference voltage using the obtained result.

In FIG. 11, the imaging device 1 photoelectrically converts incident light and outputs an analog image signal. The A / D reference voltage setting device 2 sets a reference voltage that is referred to during A / D conversion. The A / D conversion processing device 3 converts an analog image signal into a digital image signal. The image recognition processing device 4 performs image recognition using the digital image signal obtained by the A / D conversion processing device 3.
In the fourth embodiment, the A / D reference voltage setting device 2 includes a reference voltage setting A / D conversion unit 21 and a reference value setting unit 22.
Here, the difference from the first embodiment is that the configuration of the A / D reference voltage setting device 2 includes a reference voltage setting A / D conversion unit 21 and a reference value setting unit 22. That is, the analog processing configuration of FIG. 2 is realized by digital processing.

  The reference voltage setting A / D converter 21 performs A / D conversion on the analog image signal obtained by the imaging device 1 with a predetermined reference voltage, and inputs the obtained digital image signal to the reference voltage setting unit 22. In the reference voltage setting unit 22, the maximum value and the minimum value are obtained from data in one scanning period of the input digital image signal, and a voltage corresponding to the obtained luminance level of the maximum value is obtained from the A / D conversion processing device 3. The upper limit reference voltage (High) is set, and the voltage corresponding to the obtained minimum luminance level is set as the lower limit reference voltage (Low) of the A / D converter 3.

This is shown in FIG. In the following, a method for obtaining the maximum value will be described first. Here, the comparator 411 detects the larger value. When a pulse is input by the latch 421, the value is latched. The D / A conversion circuit 413 performs A / D conversion on the latched signal.
The signal quantized by the A / D converter 21 is input to A of FIG. 12 and compared with the B signal by the comparator 411. B is cleared to 0 before the scan line begins. The clear timing may be cleared by a horizontal synchronization signal, for example.
Next, the output C of the comparator 411 is fed back to the output of B and compared with the next A / D signal, and the larger one of A and B is output. If this operation is repeated for 1H period, the maximum value during that period can be obtained. If the signal is latched with, for example, a horizontal synchronization signal before the signal of the next scanning line is output, the value is held, and this value is D / A converted so that the A / D conversion processing device 3 of the next stage An upper reference signal (High) is obtained. In the case of the minimum value, it can be easily realized by setting the largest value that can be expressed by the input signal and setting the comparative calculation power to the smaller one instead of clearing it beforehand with 0.

As described above, the upper / lower limit reference voltage of the A / D conversion device 3 is set so that only the maximum luminance level and the minimum luminance level on one scanning line are A / D-converted. The A / D conversion device 3 that performs A / D conversion of the analog image signal can output a digital image signal using gradation effectively for each scanning line.
In the above example, each scanning line has been described. However, it may be a plurality of scanning lines. In this case, a clear pulse of the latch circuit may be input for each of the scanning lines.

  According to the fourth embodiment of the present invention, in the configuration of the first embodiment, the A / D reference value setting means comprising the A / D reference voltage setting device 2 is obtained by the imaging means comprising the imaging device 1. Reference value setting A / D conversion means comprising a reference voltage setting A / D conversion section 21 for converting an analog image signal into a digital image signal, and comprising the reference voltage setting A / D conversion section 21 From the digital image signal obtained by the A / D conversion means for setting the reference value, the reference voltage setting unit 22 makes the maximum and minimum luminance values at least for each scanning line, that is, for each scanning line or for each scanning line. And the reference values such as the upper limit reference voltage and the lower limit reference voltage of the A / D conversion processing means are set using the detected value, so that the A / D conversion processing means is used using a digital signal. Even if there is a large difference in brightness around the object or when the brightness of the shooting range changes suddenly, a high-contrast image signal suitable for image recognition can be obtained for high-accuracy image recognition. An image processing apparatus capable of performing the processing can be provided.

Embodiment 5 FIG.
A fifth embodiment of the present invention will be described with reference to FIG. FIG. 13 is a block diagram showing the configuration of the image processing apparatus according to the fifth embodiment.
In the fifth embodiment, the configuration other than the specific configuration described here has the same configuration contents as those in the first to fourth embodiments described above, and exhibits the same operation. Is. In the drawings, the same reference numerals indicate the same or corresponding parts.

In the third embodiment, the maximum value and the minimum value are obtained from the analog signal and the analog delay means is used. In the fifth embodiment, an example in which the digital signal is used will be described.
FIG. 13 shows an A / D reference value setting means 2 for setting a reference voltage using a result of A / D conversion with reference to a predetermined reference voltage, and an analog image input to the A / D conversion processing device 3. It is an example of the image processing apparatus provided with the delay means which delays a signal for 1 scanning period.

In FIG. 13, the imaging device 1 photoelectrically converts incident light and outputs an analog image signal. The A / D reference voltage setting unit 2 sets a reference voltage that is referred to during A / D conversion. The A / D conversion processing device 3 converts an analog image signal into a digital image signal. The image recognition processing device 4 performs image recognition using the digital image signal obtained by the A / D conversion processing device 3.
In the fifth embodiment, the A / D reference voltage setting device 2 includes a reference voltage setting A / D conversion unit 21 and a reference value setting unit 22. Then, a delay means comprising a delay circuit 5 is provided.

The delay circuit 5 delays the analog image signal obtained from the imaging device 1 by one scanning period. The delay circuit 5 can be easily realized using a CCD delay element or the like as described in the third embodiment.
The analog image signal delayed by one scanning period by the delay circuit 5 is input to the A / D conversion processing device 3. The A / D conversion processing device 3 performs A / D conversion of the analog image signal input from the delay circuit 5 with reference to the reference voltage set by the A / D reference voltage setting device 2.

In other words, the analog image signal used for setting the reference voltage and the analog image signal used for A / D conversion can be performed on the same scanning line, so even if the screen changes suddenly, the scanning line A digital image signal with good contrast can be obtained every time.
In the above-described example, the description has been made for each scanning line, but it may be performed for each of a plurality of scanning lines. In this case, the delay amount of the delay means 5 is a delay amount for a plurality of scanning lines.

  According to the fifth embodiment of the present invention, in the A / D conversion processing means including the A / D conversion processing device 3, the reference value setting A / D conversion including the reference voltage setting A / D conversion unit 21 is performed. The analog image signal used for A / D conversion after the reference value is set by the A / D reference voltage setting device 2 having the means is delayed by at least one scanning period by the delay means comprising the delay circuit 5, so that the digital signal Is used to set the reference value of the A / D conversion processing means and appropriately process the analog image signal, even when the brightness difference around the object is large or when the brightness of the shooting range changes suddenly, It is possible to provide an image processing apparatus capable of obtaining a high-contrast image signal suitable for image recognition and performing highly accurate image recognition.

Embodiment 6 FIG.
A sixth embodiment according to the present invention will be described with reference to FIGS. FIG. 14 is a block diagram showing the configuration of the image processing apparatus according to the sixth embodiment. FIG. 15 is an explanatory diagram showing the operation in the sixth embodiment.
In the sixth embodiment, the configuration other than the specific configuration described here has the same configuration contents as those in the first to fifth embodiments described above, and exhibits the same operation. Is. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 14 is an example of an image processing apparatus provided with A / D reference value setting means for setting a reference voltage with reference to the luminance level of the object recognized by the image recognition means 4.

In FIG. 14, the imaging apparatus 1 photoelectrically converts incident light and outputs an analog image signal. The A / D reference voltage setting device 2 sets a reference voltage that is referred to during A / D conversion. The A / D conversion processing device 3 converts an analog image signal into a digital image signal. The image recognition processing device 4 performs image recognition using the digital image signal obtained by the A / D conversion processing device 3.
In the sixth embodiment, the A / D reference voltage setting device 2 uses the reference voltage setting A / D conversion unit 21 and the maximum value or the minimum value obtained from the image processing result to perform A / D conversion. The reference voltage setting unit 23 sets the upper and lower reference voltages. The image recognition processing device 6 includes a set value output unit 30 that outputs an upper / lower limit reference voltage setting signal for the A / D conversion processing device 3.

When the recognized object is on the scanning line, the set value output means 30 provided in the image recognition processing device 6 detects the brightening level of the object on the scanning line or in the target area, and performs image processing. Find the upper and lower limit settings that are convenient for you. Here, the good upper limit setting value for the upper part of the image processing is, for example, a value obtained by adding a predetermined value to the maximum luminance value in the target scanning line or region. Similarly, the lower limit setting value that is convenient for image processing is a value obtained by subtracting a predetermined value from the minimum luminance value in the target scanning line or region.
The upper limit set value and the lower limit set value obtained in this way are input to the reference voltage setting unit 23. The reference voltage setting unit 23 sets the input upper limit set value to the upper limit reference voltage (High) of the A / D conversion processing device 3 and sets the lower limit set value to the lower limit reference voltage (Low).

This is shown in FIG. For example, when the upper limit set value and the lower limit set value output from the luminance output unit 30 are digital values, they are latched by the latch circuits 23a and 23b, respectively, and then D / A converted by the D / A converters 23c and 23d. Two D / A values of the upper limit set value and the lower limit set value are input to the A / D conversion processing device 3 as the upper and lower limit reference voltages for A / D conversion.
As described above, when the object is present on the scanning line, the reference voltage is set so that only A / D conversion is performed between the vicinity of the maximum luminance level and the vicinity of the minimum luminance level of the object. The A / D conversion processing device 3 that performs A / D conversion on the input analog image signal can output a digital image signal that effectively uses the gradation of the object for each scanning line. In the image recognition processing device 6, the digital image signal is subjected to image processing such as binarization and edge extraction to recognize an object, so that the recognition rate is improved as compared with the related art and a reliable result is obtained. be able to.

  According to the sixth embodiment of the present invention, in the configuration of the first embodiment, the A / D reference value setting means comprising the A / D reference voltage setting device 2 is an image processing means comprising the image recognition processing device 6. Based on the luminance value of the object from the luminance value output unit 30 detected in step 1, reference values such as the upper limit reference voltage and the lower limit reference voltage of the A / D conversion processing means comprising the A / D conversion processing device 3 are set. Since the reference value of the A / D conversion processing means is set using the luminance value of the object, even when the brightness difference around the object is large or when the brightness of the shooting range suddenly changes, It is possible to provide an image processing apparatus capable of obtaining a high-contrast image signal suitable for image recognition and performing highly accurate image recognition.

Embodiment 7 FIG.
A seventh embodiment of the present invention will be described with reference to FIG. FIG. 16 is a characteristic diagram showing the characteristics of the seventh embodiment in comparison with the prior art.
In the seventh embodiment, the configuration other than the specific configuration described here has the same configuration contents as those in the first to sixth embodiments described above, and has the same effect. Is. In the drawings, the same reference numerals indicate the same or corresponding parts.

As described above, the configurations described in the first to sixth embodiments are particularly effective when the input device has a wide input luminance dynamic range.
In the seventh embodiment, there is provided an imaging means including the imaging device 1 having a wide input luminance dynamic range capable of imaging a wide contrast difference in which the input / output characteristics have a nonlinear characteristic in the configuration in the first to sixth embodiments. What was used will be described.

  FIG. 16 is a human output characteristic diagram of an imaging unit having a wide input luminance dynamic range and a conventional imaging unit, where the horizontal axis indicates the luminance input to the imaging unit and the vertical axis indicates the output of the imaging unit. Here, a human output characteristic 701 of the conventional imaging means and an input / output characteristic 702 of the imaging means having a wide input luminance dynamic range are shown. Further, the minimum luminance value a of the imaging target is indicated as 703, and the maximum luminance value b of the imaging target is indicated as 704. Then, the output difference (contrast) 705 between a and b according to the input / output characteristics of the conventional imaging means, the output difference (contrast) 706 between a and b according to the human output characteristics of the imaging means with a wide input luminance dynamic range, and the conventional A / A D conversion range 707 and an A / D conversion range 708 according to the present invention are shown.

  As shown in the figure, in the conventional characteristic 701, instead of the input luminance dynamic range being narrow, for example, the contrast of the upper and lower limit luminance values a and b to be imaged is large (705). On the other hand, in the input / output characteristics 702 of the imaging means having a wide input luminance dynamic range, the contrast of the upper and lower limit luminance values a and b to be imaged is small instead of the wide input luminance dynamic range (706). In image processing, it is a major premise that there is a luminance difference, and an imaging means with a wide dynamic range has a smaller luminance difference than the conventional one, so it cannot be denied that it is disadvantageous in image processing.

According to the present invention, the conventional A / D conversion range 707 is not applied, and voltages corresponding to the target minimum luminance a and maximum luminance b are set as the upper and lower limit reference voltages for A / D conversion. In this case, the luminance difference 706 due to the imaging means having a wide input luminance dynamic range is A / D converted by the A / D conversion range 708, so that the number of bits of the A / D converter is used almost fully. Quantized.
For example, if the number of bits of the A / D converter is 8 bits, and the luminance difference 706 is A / D converted by the conventional A / D conversion range 707, it can be expressed only by a part of the maximum resolution 256. When converted by the A / D conversion range 708 of the present invention, it can be expressed with a resolution substantially close to the maximum value 256.

  According to the seventh embodiment of the present invention, in any configuration from the first to sixth embodiments, the image pickup means including the image pickup apparatus 1 has a wide contrast with a non-linear characteristic in the input / output characteristic. Since it is a wide dynamic range imaging means that can capture the difference, it has good contrast suitable for image recognition even when the brightness difference around the object is large or the brightness of the shooting range changes suddenly It is possible to provide an image processing apparatus that can obtain an image signal and perform high-accuracy image recognition and ensure high resolution.

In the embodiment according to the present invention, the configurations described in the following items (1) to (6) are proposed.
(1) Obtained by an imaging means for photoelectrically converting incident light, an A / D conversion processing means for converting an analog image signal obtained from the imaging means into a digital image signal, and the A / D conversion processing means In an image processing apparatus having image processing means for performing image processing on a digital image signal and extracting an object, a reference voltage to be referred to at the time of A / D conversion is set to a scanning line before the A / D conversion means. An image processing apparatus comprising A / D reference value setting means for setting for each area or for each area.
(2) The A / D reference value setting means detects, from the analog image signal obtained from the imaging means, a maximum peak detecting means for detecting a maximum peak value of luminance at least for each scanning line, and a minimum peak value. It comprises a minimum peak value detecting means, a maximum peak value holding means for holding each peak value for a predetermined time, and a minimum peak value holding means, and the stored maximum peak value and minimum peak value are stored in the A / D conversion processing means. The image processing apparatus according to item (1), wherein the image processing apparatus is set to a reference voltage.
(3) The image processing apparatus according to (2), wherein the analog image signal used for A / D conversion is delayed by at least one scanning period in the A / D conversion processing means.
(4) The A / D reference value setting means first performs A / D conversion using a predetermined reference voltage, and from the obtained digital image signal, the maximum value and the minimum value of luminance at least for each scanning line. And the reference voltage of the A / D conversion processing means is set using the detected value. The image processing apparatus according to item (1),
(5) The image processing apparatus according to (4), wherein in the A / D conversion processing means, an analog image signal used for A / D conversion after setting a reference voltage is delayed by at least one scanning period.
(6) The A / D reference value setting means sets the reference voltage of the A / D conversion processing means based on the luminance value of the object detected by the image processing means (1) The image processing apparatus described.

  The image processing apparatus according to the present invention sets, for each region, a reference voltage that is referred to when A / D converting an image signal.

  In the image processing apparatus according to the present invention, a reference voltage to be referred to in a gap for A / D conversion of an image signal is set for at least one scanning line, and is detected for each scanning line or a plurality of scanning lines. The peak voltage of the analog image signal thus set is set as a reference voltage.

  Further, in the A / D conversion in which the peak voltage of the analog image signal is obtained and set to the reference voltage, the input analog image signal is delayed by at least one scanning line.

  The image processing apparatus according to the present invention performs A / D conversion using a predetermined reference voltage, detects the maximum value and the minimum value for each scanning line from the obtained digital image signal, and detects the maximum value and the minimum value. A reference voltage is set based on the value, A / D conversion is performed again, and image recognition processing is performed using the obtained image signal.

  Further, in A / D conversion in which a reference voltage is set using a result of A / D conversion with a predetermined reference voltage, an input analog image signal is used after being delayed by at least one scanning line.

  The image processing apparatus according to the present invention sets a reference voltage to be referred to when the image signal is A / D converted at least for each scanning line using the luminance of the object recognized by the image recognition process. Is.

  Further, the image pickup means of the image processing apparatus according to the present invention uses a wide dynamic range image pickup means that can pick up an image without saturating the signal on both the bright side and the dark side even in a situation where the contrast between light and dark is large.

  As described above, in the image processing apparatus according to the present invention, since the reference voltage corresponding to the brightness is set for each area, the A / D is used by using an appropriate reference voltage without being affected by the brightness of other areas. Conversion can be performed. As a result, a digital image signal with good contrast can be obtained, and therefore, using this digital image signal, accurate image recognition can be performed.

  In the image processing apparatus as described above, by setting the reference voltage at the time of A / D conversion at least for each scanning line, even if the brightness difference around the object is large, the brightness of other scanning lines is affected. Instead, A / D conversion can be performed with reference to a reference voltage suitable for each scanning line.

  Further, by detecting the peak voltage on the scanning line from the analog image signal, setting the peak voltage as a reference voltage and performing A / D conversion, the gradation of the digital image signal on the scanning line is effectively used. Therefore, an image signal with good contrast suitable for image recognition can be obtained.

  Further, the maximum peak voltage value and the minimum peak voltage value of the luminance signal of each scanning line are detected, and the analog image signal input to the A / D conversion is delayed for one scanning period in which the detected value is set to the upper and lower limit reference voltages. By doing so, the luminance signal for detecting the maximum voltage and the minimum voltage set as the upper and lower reference voltages and the luminance signal for A / D conversion can be those on the same scanning line. As a result, even when the screen changes suddenly and the brightness of the shooting range changes suddenly, a digital image signal using gradation effectively can be obtained for each scanning line. Therefore, accurate image recognition can be performed.

  In the image processing apparatus according to the present invention, the maximum value and the minimum value of the luminance on the scanning line are obtained from the result of A / D conversion performed using a predetermined reference voltage, and the result of D / A conversion of the obtained value is obtained. Set to the reference voltage and perform A / D conversion again. As a result, even when the video changes suddenly and the brightness of the shooting range changes suddenly, a digital image signal using gradation effectively can be obtained for each scanning line. It is effective for image recognition processing that handles image data, and this digital image signal can be used to perform accurate image recognition.

  Furthermore, the maximum and minimum luminance values are obtained from the result of A / D conversion performed using a predetermined reference voltage, and the set reference voltage is set while the reference voltage is set based on the obtained value. By delaying the analog image signal input to the A / D conversion performed using the luminance signal for detecting the maximum value and the minimum value for setting the upper and lower limit reference voltage, and the set reference voltage A As the luminance signal for performing the / D conversion, those on the same scanning line can be used. As a result, even when the screen changes suddenly and the brightness of the shooting range changes suddenly, a digital image signal using gradation effectively can be obtained for each scanning line. Therefore, accurate image recognition can be performed.

  In addition, the reference voltage to be referred to at the time of A / D conversion is set at least for each scanning line based on the luminance value of the object recognized by the image recognition means, so that the full scale of the digital image signal can be recognized. Therefore, it is possible to obtain an image signal with good contrast suitable for image recognition.

  In addition, since a wide dynamic range imaging device is used, it is possible not only to reproduce the difference in brightness, but also in a low-contrast situation, even if the signal is saturated or blacked out on the bright side or dark side. However, since the full scale of the digital image signal can be set within the luminance range necessary for image recognition, an image signal with good contrast suitable for image recognition can be obtained.

  In the image processing apparatus according to the present invention, the maximum voltage characteristic and the minimum voltage value of the longitude signal of each scanning line are detected, and the detected value is set as the upper and lower limit reference voltage to perform A / D conversion. As a result, even when the video changes suddenly, a digital image signal using gradation effectively can be obtained for each scanning line, which is effective for image recognition processing that handles image data for each scanning line. If this digital image signal is used, accurate image recognition can be performed.

  The image processing apparatus according to the present invention refers to the brightness of the object detected by the image recognition means for each scanning line, sets the reference voltage, and performs A / D conversion. As a result, it is possible to obtain a digital image signal that effectively uses the gradation except for an unnecessary luminance level that is higher than that of the object. Therefore, accurate image recognition can be performed using this digital image signal. be able to.

  In the image processing apparatus according to the present invention, A / D conversion is performed only between the maximum luminance level and the minimum luminance level on the scanning line, or the luminance level and the minimum luminance of the object on the scanning line are only A / D converted. For example, only a necessary part is A / D converted for each scanning line. As a result, in an image processing apparatus using a wide dynamic range imaging means that can capture a wide contrast difference, only data of a necessary luminance level is extracted, and a digital image signal using gradation effectively is obtained. Therefore, if this digital image signal is used, accurate image recognition can be performed.

  Further, according to the present invention, even in an imaging means with a wide input luminance dynamic range, the voltage corresponding to the minimum luminance and the maximum luminance of the target is set as the upper / lower reference voltage for A / D conversion, so that only low contrast can be obtained. Even if the target cannot be obtained, the contrast can be improved at the quantization stage, so that it is possible to obtain a digital image signal that effectively uses gradation, and with this digital image signal, accurate image recognition is performed. be able to.

It is a block diagram which shows the structure of the image processing apparatus in Embodiment 1 by this invention. It is explanatory drawing which shows an example of the driving image of the front in Embodiment 1 by this invention. It is a characteristic diagram which shows the brightness | luminance histogram in area | region (a), (b), (c) of FIG. It is a block diagram which shows the structure of the image processing apparatus in Embodiment 2 by this invention. It is explanatory drawing which shows the operation | movement in Embodiment 2 by this invention. It is explanatory drawing which shows the operation | movement in Embodiment 2 by this invention. It is a connection diagram which shows an example of the circuit which implement | achieves the maximum peak value detection means and the minimum peak value detection means in Embodiment 2 by this invention. It is a connection diagram which shows an example of the circuit which implement | achieves the peak value holding means in Embodiment 2 by this invention. It is a block diagram which shows the structure of the image processing apparatus in Embodiment 3 by this invention. It is explanatory drawing which shows the operation | movement in Embodiment 3 by this invention. It is a block diagram which shows the structure of the image processing apparatus in Embodiment 4 by this invention. It is a block diagram which shows the structure of the image processing apparatus in Embodiment 4 by this invention. It is a block diagram which shows the structure of the image processing apparatus in Embodiment 5 by this invention. It is a block diagram which shows the structure of the image processing apparatus in Embodiment 6 by this invention. It is a block diagram which shows the structure of the reference voltage setting means 23 in Embodiment 6 by this invention. It is a characteristic diagram which shows the characteristic in Embodiment 7 by this invention compared with a prior art.

Explanation of symbols

1 imaging device, 2 A / D reference voltage setting device, 3 A / D conversion device, 4 image recognition processing device, 5 delay circuit, 6 image recognition processing device, 10 maximum peak value detection circuit, 11 maximum peak value holding circuit, 12 Minimum peak value detection circuit, 13 Minimum peak value holding circuit, 21 Reference voltage setting A / D converter, 22, 23 Reference voltage setting unit, 30 Luminance output unit, 111 White line, 112 Road surface, 113 area (a), 114 region (b), 115 region (c), 211 luminance signal in the nth scanning line, 212 maximum luminance signal value in the nth scanning line, 213 minimum luminance signal value in the nth scanning line, 411 comparison , 412 latch, 413 D / A converter, 701 Human output characteristics of an imaging apparatus in the prior art, 702 Input / output characteristics of an imaging apparatus with a wide input luminance dynamic range, 7 3 Minimum brightness value a of the imaging target a, 704 Maximum brightness value b of the imaging target, 705 Output difference (contrast) between a and b according to the input / output characteristics of the imaging device in the prior art, 706 Human output of the imaging device with a wide input dynamic range Output difference (contrast) between a and b according to characteristics, 707 A / D conversion range according to prior art, 708 A / D conversion range according to the present invention.

Claims (8)

  An imaging unit that scans incident light to perform photoelectric conversion, an A / D conversion processing unit for converting an analog image signal obtained by the imaging unit into a digital image signal, and the A / D conversion processing unit In an image processing apparatus including an image processing unit that performs image processing on a digital image signal and extracts an object, a reference that is referred to in order to determine an A / D conversion range in the A / D conversion processing unit An image processing apparatus comprising A / D reference value setting means for setting a value for each predetermined scanning line number range smaller than the number of scanning lines corresponding to one frame of an image.   An imaging unit that scans incident light to perform photoelectric conversion, an A / D conversion processing unit for converting an analog image signal obtained by the imaging unit into a digital image signal, and the A / D conversion processing unit In an image processing apparatus including an image processing unit that performs image processing on a digital image signal and extracts an object, a reference that is referred to in order to determine an A / D conversion range in the A / D conversion processing unit An image processing apparatus comprising A / D reference value setting means for setting a value for each scanning line.   The A / D reference value setting means includes a maximum peak detecting means for detecting a maximum peak value of luminance for each scanning line in the analog image signal obtained by the imaging means, and an analog image signal obtained by the imaging means. A minimum peak value detecting means for detecting a minimum peak value of brightness for each scanning line; a maximum peak value holding means for holding each peak value for a predetermined time; and a minimum peak value holding means; The image according to claim 1 or 2, wherein the maximum peak value and the minimum peak value held by the value holding means and the minimum peak value holding means are set as reference values for the A / D conversion processing means. Processing equipment.   The image processing apparatus according to claim 1, wherein an analog image signal used for A / D conversion in the A / D conversion processing unit is delayed by at least one scanning period.   The A / D reference value setting means includes reference value setting A / D conversion means for converting an analog image signal obtained by the imaging means into a digital image signal, and the reference value setting A / D conversion. A maximum value and a minimum value of luminance are detected at least for each scanning line from the digital image signal obtained by the means, and a reference value of the A / D conversion processing means is set using the detected value. The image processing apparatus according to claim 1 or 2.   6. The image processing apparatus according to claim 5, wherein an analog image signal used for A / D conversion after setting a reference value in the A / D conversion processing means is delayed by at least one scanning period.   The A / D reference value setting means sets the reference value of the A / D conversion processing means based on the luminance value of the object detected by the image processing means. 2. The image processing apparatus according to 2. The image processing apparatus according to any one of claims 1 to 7, wherein the imaging unit is a wide dynamic range imaging unit that can capture a wide difference in brightness with an input / output characteristic having a nonlinear characteristic. .

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