JP2007013687A - Image pickup device with iris adjustment function by liquid crystal shutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To clarify contrast without depending upon a mechanical iris. <P>SOLUTION: By providing a liquid crystal shutter 32 that varies light transmittance for each pixel over the entire surface of a solid-state image pickup element 13 in place of a mechanical iris adjustment mechanism, the contrast of these images is clarified, even though there are many high luminance parts Aip and the high luminance parts are large, by a high luminance level determining part 45 of a CPU part 38, a whole liquid crystal shutter light transmittance increasing/decreasing part 46, a high luminance part light transmittance increasing/decreasing part 47, a D range/high luminance level comparing part 51, a high luminance group determining part 55, and a D range/high luminance level comparing part 56. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus with an iris adjustment function using a liquid crystal shutter that adjusts an iris by a liquid crystal shutter without using a mechanical iris mechanism.

  When imaging a subject with a camera, the light quantity is adjusted by changing the optical path diameter using a mechanical iris mechanism (mechanical iris) in order to appropriately adjust the light quantity so as not to exceed the dynamic range of the image sensor. . The iris is usually adjusted so that the brightest part is projected as brightly as possible.

  FIG. 12 shows such a conventional mechanical iris.

  FIG. 12 is a block diagram of an image pickup apparatus using a conventional mechanical iris mechanism. As shown in FIG. 12, this imaging apparatus compares a lens 11, a mechanical iris blade mechanism 12, an imaging device 13, a signal processing circuit 14, and a target value and a video signal level of the signal processing circuit 14. The comparison circuit 15 and at least a drive circuit 16 that controls the iris blade mechanism 12 based on the comparison result from the comparison circuit 15 are provided.

  In the conventional imaging apparatus as described above, the image of the subject is received by the imaging device 13 via the lens 11 and the iris blade mechanism 12. The video signal photoelectrically converted by the image sensor 13 is integrated by a signal processing circuit 14 with a certain time constant and output to the comparison circuit 15 in the form of a DC voltage value.

  The comparison circuit 15 determines whether or not it matches (matches) a preset target voltage value, and if smaller than the target voltage value, opens the iris blade mechanism 12 to the drive circuit 16 of the iris blade mechanism 12. The control is performed by increasing the amount of light received by the image sensor 13 by instructing and matching.

  On the other hand, when the voltage is larger than the target voltage value, the drive circuit 16 of the iris blade mechanism 12 is instructed to close the iris blade mechanism 12 to reduce the amount of light received by the image pickup device 13 to match (match). To control.

  As the target voltage value, for example, when a gray scale chart is imaged, a value is selected such that the output signal voltage of the signal processing circuit 14 is 0.7 V (pp).

Japanese Laid-Open Patent Publication No. 2001-8094 (Patent Document 1) discloses that an optical image from an imaging lens is transmitted by a diaphragm blade and received by an imaging device.
JP 2001-8094 A

  However, in the conventional method, when the amount of light is large, the optical path of the iris mechanism is narrowed down, and the focus may be reduced due to the diffraction phenomenon.

  In addition, since the light amount is adjusted by averaging the entire pixels of the image sensor, for example, if the subject is not uniform in brightness but has a large difference in brightness, the entire screen is adjusted uniformly. Since the dynamic range of the image sensor is narrow, there is a problem that a bright place is overcharged with an excessive amount of light, and conversely, the place is crushed due to an insufficient amount of light, and an image cannot be taken with an appropriate brightness.

That is, when the luminance distribution (histogram) on the screen is shown in FIG. 13, the operation of the conventional method of FIG. 12 is to match the center of gravity position of FIG. 13 to a set target value. That is, the conventional method is nothing but adjustment to cover the area where the dynamic range of the image sensor is larger than the histogram. At this time, in FIG. 13, the portion outside the dynamic range of the image sensor (21 in FIG. 13). No.) has a problem that the output of the image sensor is saturated and the contrast cannot be expressed.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain an imaging device with an iris adjustment function using a liquid crystal shutter that can make the contrast clear without using a mechanical iris.

  The present invention provides an image pickup apparatus including a signal processing unit that forms an optical image of a picked-up subject on an image pickup device via a lens system, performs photoelectric conversion, converts the image data into field-unit image data, and outputs the image data. A liquid crystal shutter provided between the lens system and the image sensor, and having a plurality of lattice region portions made of liquid crystal capable of changing light transmittance corresponding to the pixels on the imaging surface of the image sensor; A drive circuit for outputting a drive signal for changing the light transmittance for each of the lattice region portions to the liquid crystal shutter; and a first control signal for setting all the lattice region portions of the liquid crystal shutter to a maximum light transmittance. Is output to the drive circuit, and the image data output from the signal processing unit has luminance data in a predetermined range in which the luminance level is less than or equal to the dynamic range of the image sensor and greater than or equal to a certain luminance level. When the brightness level of the extracted high brightness portion data matches the upper limit value of the dynamic range of the image sensor, the brightness value of the brightness of the image data is desired. An increase / decrease value of the light transmittance of the liquid crystal shutter to match the target value of the liquid crystal shutter, and a means for outputting the increase / decrease value to the drive circuit as a second control signal; and an average value of luminance of the image data If it matches the target value, it is determined whether the brightness level of the high brightness portion data matches the upper limit value, and an increase / decrease value of the light transmittance of the liquid crystal shutter is obtained based on the determination result. Thus, the gist of the present invention is that the device is provided with means for outputting the increase / decrease value as a third control signal to the drive circuit to adjust the iris.

  According to the present invention, instead of the mechanical iris adjustment mechanism, a liquid crystal shutter having a variable transmittance for each pixel is provided on the front surface of the solid-state imaging device, so that even if there are many high-luminance portions and a large region, The contrast of these images can be clarified.

  FIG. 1 is a schematic configuration diagram of an imaging apparatus with an iris adjustment function using a liquid crystal shutter according to an embodiment of the present invention.

  As shown in FIG. 1, the imaging apparatus with an iris adjustment function using a liquid crystal shutter according to this embodiment includes a liquid crystal shutter 32 between a lens 31 and a solid-state imaging device 13. Further, a complementary color filter 40 is provided between the liquid crystal shutter 32 and the solid-state imaging device 13. A signal processing circuit 14 is provided at the subsequent stage of the solid-state imaging device 13. The signal processing circuit 14 digitally converts the video signal photoelectrically converted by the solid-state imaging device 13, and outputs a DC voltage value integrated with a certain time constant to the CPU unit 38 and also from the terminal 37.

  The above-described liquid crystal shutter 32 is made of a liquid crystal material whose light transmittance changes. As shown in FIG. 2, the solid-state imaging device 13 is divided on a lattice, and the divided lattice region ai (ai: a1, a2,...: Number of pixels 3 × 3 or 4 × 4 ,...), The light transmittance changes depending on the applied voltage. For example, the light transmittance changes from a transparent light transmittance to a light transmittance that does not transmit light.

  Further, as shown in FIG. 2, the liquid crystal shutter 32 is provided with a Y-axis drive unit 32b and an X-axis drive unit 32c, and the light transmittance of the target lattice region ai specified by these drive units changes. .

  The CPU unit 38 includes at least a high luminance level determination unit 45, a liquid crystal shutter light transmittance overall increase / decrease unit 46, and a high luminance part light transmittance increase / decrease unit 47, which will be described later, and performs the following processing.

(1) Initially, the high brightness portion determination unit 45 maximizes (transparents) the light transmittance of all the lattice regions ai of the liquid crystal shutter 32, and the image data of the signal processing unit 14 (image data based on the solid-state image sensor) ) In the memory so that the brightness level of the image data Ai (A1, A2,...) Falls within the upper limit of the dynamic range (hereinafter referred to as D range) of the solid-state image sensor 13. While increasing or decreasing the light transmittance of the lattice area ai, a high-luminance portion Aip having a certain range or more (for example, 20 × 20) is extracted. That is, a high-luminance portion Aip having a certain size or more that falls within the peak of the D range is extracted.

(2) Next, the liquid crystal shutter light transmittance overall increase / decrease unit 46 sets the average brightness of the image data of the entire pixels of the solid-state imaging device 13 as the target when the high brightness portion Aip falls within the D range condition. The light transmittance of each lattice ai of the liquid crystal shutter 32 is increased or decreased so as to match the luminance. In other words, the bright and dark areas of the entire screen are understood.

(3) Then, the high luminance portion light transmittance increasing / decreasing unit 47 is configured such that when the average luminance of the image data of the entire pixels of the solid-state imaging device 13 matches the target luminance (the entire screen has reached the target luminance level). When the brightness of each pixel of each high brightness portion Aip in the group of high brightness portions Aip is not equal to the upper limit of the D range (when they do not match), the lattice area ESW of the liquid crystal shutter 32 corresponding to the high brightness portion Aip Increase or decrease the light transmittance. At this time, the light transmittance of the surrounding region WQi of the lattice at the center of the lattice region ESW is increased or decreased with reference to the central lattice region.

  Thereby, for example, even if a large high-intensity part exists in two lights of an automobile, the two lights become clear.

  That is, since not only the corresponding pixel is adjusted within the D range but also the surroundings are adjusted, it is possible to maintain a good contrast around the corresponding pixel.

  The drive circuit 39 controls the Y-axis drive unit 32b and the X-axis drive unit 32c in order to increase or decrease the light transmittance of each lattice area ai (including ESW and WQi) of the liquid crystal shutter 32 from the CPU unit 38.

  That is, since the imaging apparatus of the present embodiment sets the light transmittance of the liquid crystal shutter at the position corresponding to the pixel based on the luminance of each pixel of the solid-state imaging device 13, the dynamic range of the imaging device is set. It can be used effectively to shoot with sufficient contrast in both dark and bright areas.

  In addition, since the amount of light on the imaging surface can be changed uniformly, the luminance difference is large without causing blurring due to diffraction phenomenon like mechanical iris that adjusts the amount of light by limiting the optical path diameter, or the luminance itself It is possible to take a suitable image at a high place.

  FIG. 3 is a schematic configuration diagram of the CPU unit 38 of the present embodiment. As shown in FIG. 3, the CPU unit 38 (comprising ROM, RAM, CPU, etc.) includes a memory 50 for storing image data for each frame from the solid-state imaging device 13 in the ij column, and a high-luminance unit determination unit 45. D range / high luminance level comparison unit 51, liquid crystal shutter overall light transmittance increase / decrease unit 46, high luminance group determination unit 55, D range / high luminance level comparison unit 56, high luminance group light transmittance increase / decrease Part 47.

  Further, a memory 54 is provided in which the lattice area ai of the liquid crystal shutter 32 is defined by E (i) rows and E (j) columns.

  The high brightness portion determination unit 45 initially maximizes the light transmittance of all the lattice regions ai of the liquid crystal shutter 32 (transparency), and stores the image data (image data based on the solid-state imaging device) of the signal processing unit 14 in the memory. 50, and it is determined whether the luminance level of the image data Ai (A1, A2,...) Matches the upper limit of the D range of the solid-state imaging device 13 and is equal to or greater than a certain range (for example, 20 × 20). When these are satisfied, the high brightness portion Aip is extracted.

  The D range / high luminance level comparison unit 51 compares the luminance level Ri of the position Aij (CCD pixel position) of the high luminance part Aip extracted by the high luminance determination unit 45 with the preset upper limit of the D range. Then, the comparison result is notified to the entire liquid crystal shutter light transmittance increasing / decreasing unit 46.

  The liquid crystal shutter overall light transmittance increase / decrease unit 46 compares the comparison result of the D range / high luminance level comparison unit 51 (the upper limit of the D range is larger or smaller than the level Ri of the high luminance portion Aip) and the position Aij of the high luminance portion Aip. Is read.

  If the upper limit of the D range is greater than the level Ri of the high brightness portion Aip, the driving circuit 39 sets a liquid crystal shutter light transmittance control value that uniformly increases the light transmittance of the lattice region ai of the liquid crystal shutter 32. Output to.

  If the upper limit of the D range is smaller than the level Ri of the high brightness portion Aip, a liquid crystal shutter light transmittance control value that uniformly reduces the light transmittance of the lattice region ai is output to the drive circuit 39.

  Further, when the high-brightness determination unit 45 informs the liquid crystal shutter overall light transmittance increase / decrease unit 46 that the high-brightness portion Aip that matches the upper limit of the D range has been extracted, the average luminance of all the pixels in the memory 50 is determined. When the average value is equal to or less than the target value, the liquid crystal shutter light transmittance control value for uniformly increasing the light transmittance of the lattice area ai of the liquid crystal shutter 32 is driven. Output to the circuit 39. If the average value is equal to or greater than the target value, a liquid crystal shutter light transmittance control value that uniformly reduces the light transmittance of the lattice region ai of the liquid crystal shutter 32 is output to the drive circuit 39.

  When the average luminance of the image data of all the pixels of the solid-state image sensor 13 matches the target luminance (the entire screen is set to the target luminance level), the high luminance group determining unit 55 ), A high-luminance portion in a certain range (for example, 20 × 20 to 60 × 60) is extracted. This extraction extracts the luminance level and the position Aij of the high luminance part. Then, it is determined whether the luminance level of each pixel of the high luminance part Aip is equal to the upper limit of the D range. If they are equal, the process is terminated.

  The D range / high luminance level comparison unit 56 determines that the luminance level of each pixel of the high luminance portion Aip is the upper limit of the D range when the luminance of each pixel of the pixel group is not equal to (not equal to) the upper limit of the D range. It is determined whether it is lower, and the determination result is notified to the high luminance group light transmittance increasing / decreasing unit 47. At this time, the pixel position Aij of the high luminance part Aip and the determination result of the luminance level Ri are notified.

  When it is determined that the luminance level of each pixel of the high luminance portion Aip is lower than the upper limit of the D range, the high luminance group light transmittance increasing / decreasing unit 47 is a lattice of the liquid crystal shutter 32 corresponding to the pixel position Aij of the high luminance portion. Increase the light transmittance of the region ESW. Further, when it is determined that the luminance level of each pixel of the high luminance portion Aip is larger than the upper limit of the D range, the light transmittance of the lattice area ESW of the liquid crystal shutter 32 corresponding to the pixel position Aij of the high luminance portion Aip is reduced. To do.

  At this time, the light transmittance of the surrounding region WQi of the lattice at the center of the lattice region ESW is increased or decreased with reference to the central lattice region.

  The operation of the imaging apparatus with an iris adjustment function using the liquid crystal shutter configured as described above will be described below with reference to the flowchart of FIG.

  A light beam from a subject or the like enters the solid-state imaging device 13 via a lens 31 having a focus mechanism or the like, a liquid crystal shutter 32, and a complementary color filter 40.

  This solid-state image sensor 13 (for example, an interline CCD) reads and reads out image signals of pixels adjacent to each other in the vertical direction for each field in the vertical direction on the solid-state image sensor. The signal is output to the signal processing circuit 14.

  After the signal processing circuit 14 performs noise, gain control, etc., the digitally converted image data is output and stored in the memory 50 of the CPU unit 38.

  As the entire image data is stored, the high-intensity portion determination unit 45 initially affects a command to maximize (transparent) the light transmittance of all the lattice areas ai of the liquid crystal shutter 32. The image data (image data based on the solid-state imaging device) of the signal processing unit 14 is stored in the memory 50 while being output to the unit 46. At this time, the entire liquid crystal shutter light transmittance increasing / decreasing unit 46 reads the position a (i, j) of the lattice region ai of the liquid crystal shutter 32 based on the position information E (i, j) of the liquid crystal shutter 32 of the memory 54, and this a The light transmittance of the lattice region ai of (i, j) is maximized (all ai; 000).

  Then, the luminance level of the image data Ai (A1, A2,...) After the light transmittance is maximized is obtained (S100: The luminance of the entire screen is measured).

  Next, a range having an area larger than a certain range and greater than a preset luminance level is extracted as the high luminance portion Aip (S101). In this extraction, the position Aij and the luminance level Ri of the high luminance part Aip are extracted.

  Next, the high luminance part determination unit 45 determines whether or not the preset upper limit value of the D range matches the luminance level of the high luminance part Aip (S102).

  If it is determined in step S102 that the luminance level of the high luminance portion Aip does not match the upper limit of the D range (above the upper limit), the D range high luminance level comparison unit 51 determines that the luminance level Ri of the D high luminance portion Aip is D. It is determined whether it is below the range (S103).

  If it is determined in step S103 that the level of the high brightness portion Aip is equal to or higher than the D range, the liquid crystal shutter overall light transmittance increasing / decreasing portion 46 uniformly reduces the light transmittance of the lattice region ai of the liquid crystal shutter 32. The transmittance control value is output to the drive circuit 39 (S104), and the process proceeds to step S100.

  That is, the entire liquid crystal shutter light transmittance amplifying unit 46 reads the position a (i, j) of the lattice region ai of the liquid crystal shutter 32 based on the position information E (i, j) of the liquid crystal shutter 32 of the memory 54, and this a The light transmittance of the lattice region ai of (i, j) is reduced (all ai; for example, 0.2).

  If the upper limit of the D range is greater than the level Ri of the high brightness portion Aip in step S103, a liquid crystal shutter light transmittance control value that uniformly increases the light transmittance of the lattice area ai is output to the drive circuit 39. (S105), and the process proceeds to step S100.

  Furthermore, when it is determined in step S102 that the high luminance portion Aip does not match the D range, the liquid crystal shutter overall light transmittance increasing / decreasing portion 46 obtains the average of the luminance of all the pixels in the memory 50 (S106: overall Measure the average brightness).

  Then, the liquid crystal shutter overall light transmittance increasing / decreasing unit 46 determines whether or not the average value matches the target value (S107).

  In step S107, when the target value does not match the average value, the liquid crystal shutter overall light transmittance increasing / decreasing unit 46 determines whether or not the target value is larger than the average luminance value (the center of gravity of the histogram) (S108).

  If it is determined in step S108 that the target value is greater than the overall luminance average (NO), a liquid crystal shutter light transmittance control value for uniformly reducing the light transmittance of the lattice area ai of the liquid crystal shutter is output to the drive circuit. Then, the process proceeds to step S106.

  If the average brightness is less than or equal to the target value, a liquid crystal shutter light transmittance control value that uniformly increases the light transmittance of the lattice area ai of the liquid crystal shutter 32 is output to the drive circuit 39 (S110), and the process is performed. Move on to step S106.

  That is, when the brightness level of the high brightness portion Aip matches the upper limit of the D range, the light transmittance of the liquid crystal shutter 32 is increased or decreased until the overall brightness average matches the target value.

  The processing from step S106 to S110 to S107 will be described with reference to FIGS. In FIG. 5, when the luminance distribution of the entire image is shown as a histogram, if the D range is in the range of Di to Dp, the shaded portion is an unrepresentable region.

  Therefore, the center of gravity (average value in the present embodiment) of the histogram of the entire image is obtained, and the light transmittance of the liquid crystal shutter 32 is increased or decreased so that the center of gravity becomes a predetermined target value.

  In this way, since the center of gravity of the histogram is shifted as shown in FIG. 7 or FIG. 8, contrast can be expressed within the D range.

  On the other hand, if it is determined in step S107 that the level of the high luminance portion matches the upper limit of the D range and the average value of the entire image matches the target value, the following processing is performed for each high luminance pixel group. Perform (S111).

  When the average luminance of the image data of the pixels of the entire image of the solid-state imaging device 13 matches the target luminance, the high luminance group determining unit 55 selects the high luminance portion in a certain range. Extracted as a high luminance part Aip. This extraction extracts the luminance level and the position Aij of the high luminance part. Then, it is determined whether the luminance level of each pixel of the high luminance portion Aip is equal to the upper limit of the D range (S112). If they are equal, the process is terminated.

  The D range / high luminance level comparison unit 56 determines that the luminance level of each pixel of the high luminance portion Aip is the upper limit of the D range when the luminance of each pixel of the pixel group is not equal to (not equal to) the upper limit of the D range. It is determined whether it is lower (S113). If it is determined in step S113 that the luminance level of each pixel of the high luminance portion Aip is smaller than the upper limit of the D range, the light transmittance of the lattice area ESW of the liquid crystal shutter 32 corresponding to the position Aij of the high luminance portion Aip is set. Increase (S115), and the process proceeds to step S112.

  In other words, the entire liquid crystal shutter light transmittance increasing / decreasing unit 46 reads the position information E (i, j) of the liquid crystal shutter 32 of the memory 54 corresponding to the position Aij of the high brightness portion Aip (also referred to as EQI), and this liquid crystal shutter 32. The position a (i, j) of the lattice area ai is read, and the light transmittance of the lattice area ai at the position of this EQI is increased (for example, 0.5).

  At this time, the area of the surrounding position is also changed. As shown in FIG. 9, this change is performed so that the luminance level of the surrounding pixels decreases according to the distance from the corresponding pixel. When it is determined that the luminance level of each pixel of the high luminance portion Aip is larger than the upper limit of the D range, the light transmittance of the lattice area ESW of the liquid crystal shutter 32 corresponding to the position Aij of the high luminance portion Aip is reduced. (S114), the process proceeds to step S112. At this time, as shown in FIG. 9, the brightness level of the surrounding pixels is reduced according to the distance from the corresponding pixel.

  That is, the processing of step S111 to step S115 performs the following processing.

  As shown in FIG. 10A, when the upper limit of the D range is only 100, even if the luminance of the pixels of each solid-state imaging device is 90 to 150 as shown in FIG. Since the upper limit of the range is 100, the luminances 101 to 150 cannot be expressed and become 100 as shown in FIG.

Therefore, according to the present invention, when a high-luminance portion (for example, a car light) is detected, the pixel position Aij having the highest luminance (150) is obtained, and the pixel at this pixel position is obtained as shown in FIG. Is reduced (becomes dark) in the liquid crystal shutter region ESI (position is defined by aij) corresponding to the pixel position so that becomes the upper limit value 100 of the D range. In other words, the entire liquid crystal shutter light transmittance increasing / decreasing unit 46 reads the position information E (i, j) of the liquid crystal shutter 32 of the memory 54 corresponding to the position Aij of the high brightness portion Aip (also referred to as EQI), and this liquid crystal shutter 32. Read the position a (i, j) of the lattice area ai of the current and reduce the light transmittance of the lattice area ai at the position of this EQI (for example;
Further, in order to distinguish from other images, for example, the pixels around the 150 pixels with the light quantity so that the value of the pixel portion WQi of the light quantity 90 of the pixels around the 150 pixels is at the level of the light quantity 80. The light transmittance of the area of the liquid crystal shutter corresponding to the position is lowered.

  Further, the light transmittance is lowered so that the pixel having the light quantity of 140 has a light quantity of 85, and the pixel has a light quantity of 130.

  In the above description, the case of the decrease has been described with reference to FIGS. 9 to 11, but it may be increased according to the distance from the corresponding pixel.

It is a schematic block diagram of the imaging device with an iris adjustment function by the liquid-crystal shutter of embodiment of this invention. It is a schematic block diagram of a liquid-crystal shutter part. It is a software block diagram of a CPU unit. It is a flowchart explaining the operation | movement of this Embodiment. It is explanatory drawing explaining the process to step S106-S110-S107 with a histogram. It is explanatory drawing explaining the process to step S106-S110-S107 with a histogram. It is explanatory drawing of the histogram of a brightness | luminance at the time of changing the histogram gravity center by this Embodiment into a target value, and the number of pixels. It is explanatory drawing of the histogram of a brightness | luminance at the time of changing the histogram gravity center by this Embodiment into a target value, and the number of pixels. It is explanatory drawing explaining the graph which shows the coefficient which reduces a light transmittance with respect to the surrounding pixel as the center of the pixel concerned with respect to the pixel beyond D range of a solid-state image sensor. It is explanatory drawing explaining controlling the brightness of this Embodiment in D range. It is explanatory drawing explaining an example for discriminating surrounding contrast, controlling the high-intensity group of this Embodiment within D range. It is a schematic block diagram of the conventional imaging device. It is explanatory drawing explaining the conventional subject with the histogram.

Explanation of symbols

13 body imaging device 32 liquid crystal shutter 38 CPU unit 45 high luminance level determining unit 46 liquid crystal shutter light transmittance overall increasing / decreasing unit 47 high luminance unit light transmittance increasing / decreasing unit 51 D range / high luminance level comparing unit 55 high luminance group determining unit 56 D range / high brightness level comparison section

Claims (1)

In an imaging apparatus including a signal processing unit that forms an optical image of an imaged subject on an imaging element via a lens system, performs photoelectric conversion, converts the image data into field-unit image data, and outputs the image data.
A liquid crystal shutter provided between the lens system and the image pickup device and having a plurality of lattice region portions made of liquid crystal capable of changing the light transmittance corresponding to the pixels on the imaging surface of the image pickup device; ,
A drive circuit that outputs a drive signal for changing the light transmittance for each of the lattice region portions to the liquid crystal shutter;
A first control signal for setting all the lattice area portions of the liquid crystal shutter to a maximum light transmittance is output to the drive circuit, and the luminance level of the image data output from the signal processing unit is the imaging element. Means for extracting luminance data within a predetermined range that is equal to or less than the dynamic range and equal to or higher than a certain luminance level as high luminance portion data;
When the brightness level of the extracted high brightness portion data matches the upper limit value of the dynamic range of the image sensor, the liquid crystal shutter for matching the brightness value of the brightness of the image data to a desired target value Means for obtaining an increase / decrease value of the light transmittance and outputting the increase / decrease value to the drive circuit as a second control signal;
When the average brightness value of the image data matches the target value, it is determined whether the brightness level of the high brightness portion data matches the upper limit value, and the liquid crystal shutter is based on the determination result. Means for obtaining an increase / decrease value of the light transmittance and outputting the increase / decrease value to the drive circuit as a third control signal,
An imaging apparatus with an iris adjustment function using a liquid crystal shutter, characterized in that an iris adjustment is made.