KR20170041143A - Imaging device - Google Patents

Abstract

The present invention relates to an imaging device which can acquire a picked-up image capable of smoothly checking an inside of a car even during the day. The imaging device (1) comprises: an imaging element (40); a lens (10) forming an image from a target area on the imaging element (40); and a liquid crystal shutter (30) disposed on a target area side with respect to the imaging element (40). The liquid crystal shutter (30) has incidence side polarizing plate (301) and exit side polarizing plate. A polarizing axis (301a) of the incidence side polarizing plate (301) is set such that a light component in a polarization direction perpendicular to a vertical direction of a main body (101) of the imaging device is blocked by the incident side polarizing plate (301) after passing through the lens (10).

Description

[0001] IMAGING DEVICE [0002]

Field of the Invention [0002] The present invention relates to an image pickup apparatus for picking up a target area, and more particularly to an image pickup apparatus for picking up an outdoors landscape such as an intersection.

2. Description of the Related Art [0002] An image sensing apparatus for sensing a street or an intersection with a surveillance camera is known. In this type of image pickup apparatus, the picked-up image is used for, for example, verification of a traffic accident. In the verification, the situation of the vehicle and the pedestrian and the lighting situation of the signaling device are confirmed. That is, it is confirmed with reference to the captured image whether the horizontal or crossing point is in a situation at the time of an accident.

Patent Document 1 below discloses an image pickup apparatus for picking up a crossing or a crossing point with a surveillance camera. In this image pickup apparatus, when a person image is extracted by processing an image picked up by a surveillance camera, and the extracted person image matches or approximates to the suspect person list, an image photographed by the surveillance camera is transmitted to the terminal.

(Patent Document 1) Japanese Laid-Open Patent Publication No. 2013-153304

When an image of a crossing or a crossing is used for verification of a traffic accident or the like, it is preferable that the driver or the passenger of the vehicle causing the accident can be confirmed smoothly. However, since the sunlight is reflected from the front glass of the vehicle during the daytime at the crossing or the intersection, the visibility in the vehicle significantly deteriorates. For this reason, it is difficult to identify the driver or passenger of the vehicle by the image picked up by the image pickup apparatus.

In view of the above problems, it is an object of the present invention to provide an image pickup apparatus capable of acquiring a picked-up image which can smoothly confirm the inside of a car even during the daytime.

An imaging apparatus according to a preferred embodiment of the present invention includes an imaging element, a lens for imaging light from the target area onto the imaging element, and a liquid crystal shutter arranged on the target area side with respect to the imaging element. Here, the liquid crystal shutter includes an incidence-side polarizer and an exit-side polarizer. The light component in the polarization direction perpendicular to the up-and-down direction of the apparatus main body is blocked by the incidence- The polarization axis of the incident-side polarizer is set.

According to the image pickup apparatus of the present embodiment, the light component of S-polarized light reflected by the front glass of the vehicle is shielded by the incident-side polarizing plate. For this reason, sunlight is reflected by the front glass of the vehicle, so that deterioration of visibility in the vehicle can be suppressed. Therefore, even during the daytime, it is possible to acquire a sensed image capable of smoothly checking the inside of the car.

Here, in the case where the optical system of the image pickup apparatus is configured such that the light component of the S-polarized light reflected by the front glass is directly incident on the liquid crystal shutter without the polarization direction rotating after being taken in by the lens, Side polarization plate is substantially parallel to the polarization axis of the incident-side polarization plate. Thus, the light component of the S-polarized light reflected by the front glass of the vehicle can be shielded by the incident-side polarizing plate.

The image pickup apparatus according to the present embodiment includes a control section for controlling the image pickup element and the liquid crystal shutter. Further, the image pickup device may be configured to accumulate and output charges corresponding to the amount of received light for each line. In this case, the control unit controls the image pickup element so that a part of the charge accumulation period in each line on the image pickup element overlaps with each other, and in the overlap accumulation period in which the charge accumulation periods overlap with each other, And to open the liquid crystal shutter. In this way, since the imaging element is exposed during the overlap accumulation period, the light of the target area is irradiated to all the lines in the same timing and exposure period. Therefore, even when a subject moving at high speed is included in the target area, no distortion occurs in the picked-up image of the subject.

In the image pickup apparatus according to the present embodiment, the image pickup element has a function of a high-speed read-out mode for outputting a signal at a high speed, and the control unit sets the control mode for the image pickup element in the fast read- , Thereby to generate the overlap accumulation period. In this configuration, since the distortion of the picked-up image is suppressed by using the fast-readout mode, distortion of the subject can be suppressed while maintaining the frame transfer rate of the picked-up image.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to provide an image pickup apparatus capable of obtaining a picked-up image capable of smoothly checking the inside of a car even during the daytime.

The effect or significance of the present invention will become more apparent from the description of the embodiments described below. It should be noted, however, that the embodiments described below are merely illustrative examples of the present invention, and the present invention is not limited to what is described in the following embodiments.

Fig. 1 (a) is a diagram showing an external configuration of an image management system according to an embodiment, and Fig. 1 (b) is a diagram showing an example of a captured image according to the embodiment.
2 is a diagram showing the configuration of an image pickup apparatus according to the embodiment.
3 is a diagram showing a configuration of a CMOS image sensor according to an embodiment.
4A and 4B are diagrams for explaining reading control of the CMOS image sensor according to the embodiment.
FIG. 5A is a graph showing the reflection characteristics of light of P-polarized light and S-polarized light, and FIG. 5B is a diagram showing a state of incident and reflection of light on a reflection surface of a front glass or the like.
6 (a) and 6 (b) schematically show the structure and action of the liquid crystal shutter according to the embodiment.
7 is a front view schematically showing the positional relationship between the apparatus main body of the image pickup apparatus and the incident-side polarizing plate and the image pickup element according to the embodiment.
Fig. 8 (a) is a view showing a picked-up image obtained by actually photographing a front glass of a vehicle by an image pickup apparatus having the configuration of the embodiment, and Fig. 8 (b) Fig. 8 is a diagram showing a picked-up image in which glass is actually picked up. Fig.
9A and 9B are diagrams for explaining a control method of a CMOS image sensor according to a modification.

(Mode for carrying out the invention)

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 (a) is a diagram showing an external configuration of an image management system according to the embodiment.

As shown in Fig. 1 (a), the image management system includes an image capture device 1 and an external device 2. [ The image capturing apparatus 1 is a surveillance camera and is provided in the fixture 3 so as to capture a horizontal or crossing point including a signal unit. The image pickup device 1 is installed in the fixture 3 so that its vertical and vertical directions are along the vertical direction. The fixture 3 is, for example, an outer wall or a roof structure such as a building or a telephone pole. The image pickup device (1) records the picked-up image on an internal recording medium at any time. The external device 2 is a portable personal computer. Alternatively, the external device 2 may be another portable information terminal such as a mobile phone or a tablet.

The image recorded in the image pickup apparatus 1 is appropriately retrieved to the external apparatus 2. [ The imaging device 1 and the external device 2 can communicate by wireless LAN. The external device 2 establishes a communication path by a wireless LAN and downloads an image from the imaging device 1. [ The communication between the image capture device 1 and the external device 2 is not limited to the wireless LAN but may be other communication methods such as Bluetooth.

Fig. 1 (b) is a diagram showing an example of a picked-up image picked up by the image pickup apparatus 1. Fig. Here, the intersection 5 including the signal device 4 is set as the target area. 1 (b) shows a signal device 4 and a vehicle 6 (passenger car) facing the image pickup device 1 for convenience. An image picked up by the image pickup apparatus 1 is used for verification of a traffic accident, for example, after it is collected in the external apparatus 2. [ In this verification, the situation of the vehicle and the pedestrian proceeding at the intersection 5 and the lighting situation of the signaling device 4 are confirmed.

Fig. 2 is a diagram showing the configuration of the image pickup apparatus 1. Fig.

The image pickup apparatus 1 includes a lens 10, an iris 20, a liquid crystal shutter 30, an image pickup element 40, a control unit 50, a storage unit 60, a communication unit 70, Respectively.

The lens 10 captures light from the target area and images the image of the target area on the light receiving surface of the image pickup device 40. [ The iris 20 limits light from the outside so that an appropriate amount of light enters the imaging element 40 in accordance with the intensity of light from the target area. In the iris 20, the iris is adjusted by the iris driving circuit 21.

The liquid crystal shutter 30 has, for example, a so-called normally white type characteristic in which the transmittance becomes maximum when a voltage is not applied and the transmittance becomes low when a voltage is applied. In this case, the liquid crystal shutter 30 transmits light in a state in which no voltage is applied, and blocks light in a state in which a voltage is applied. Alternatively, the liquid crystal shutter 30 may be a liquid crystal shutter having a so-called normally black type characteristic in which the transmittance becomes maximum when the voltage is applied and the transmittance becomes low when the application of the voltage is interrupted . In the liquid crystal shutter 30, the open / close state is switched by the drive signal from the shutter drive circuit 31.

The image pickup device 40 is a CMOS image sensor. The image pickup device 40 has photodiodes at positions corresponding to the respective pixels on the light-receiving surface. The image pickup device 40 is controlled by the image pickup signal processing circuit 41 so that charges are accumulated and output to the photodiodes for each line.

The control unit 50 includes an arithmetic processing circuit such as a CPU (Central Processing Unit), and controls each part in accordance with a program stored and held in the storage unit 60. The storage unit 60 includes a storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The storage section 60 is also used as a work area at the time of control by the control section 50 in addition to storing and maintaining the control program. The control unit 50 controls the iris driving circuit 21, the shutter driving circuit 31 and the imaging signal processing circuit 41 by the program stored in the storage unit 60. [ The communication unit 70 communicates with the external device 2 shown in Fig.

Fig. 3 is a view schematically showing the configuration of the image pickup device 40. Fig. For convenience, the configuration of the portion corresponding to nine pixels is shown in Fig. 3, but in reality, the same configuration is arranged corresponding to the predetermined number of pixels in the longitudinal direction and the transverse direction.

The imaging element 40 has a photodiode 40a at a position corresponding to each pixel. When the photodiode 40a receives light, the photodiode 40a accumulates charges corresponding to the amount of received light. The accumulated charge is converted to a voltage by the amplifier 40b and amplified. The amplified voltage is transmitted to the vertical signal line 40d for each line L when the switch 40c is turned ON. The transmitted voltage is temporarily stored by a column circuit 40e arranged for each vertical signal line 40d. The stored voltage is sent to the horizontal signal line 40g when the column select switch 40f is turned ON. The voltage sent to the horizontal signal line 40g is sent to the image pickup signal processing circuit 41. [ In this way, in the image pickup device 40, a voltage signal is transmitted every line L.

Further, the image pickup device 40 is controlled so as to accumulate electric charges with respect to the photodiode 40a for each line L. That is, the photodiode 40a on one line L is set in a state in which charges can be accumulated for a predetermined period, and when this period elapses, charges generated on each photodiode 40a on the line L are outputted . This control is sequentially performed from the uppermost line L to the lowermost line L. [ When light is irradiated on the photodiode 40a on the line L when the line L is in a state in which charge can be accumulated, electric charges corresponding to the light amount of the irradiated light are accumulated in each photodiode 40a on the corresponding line. The charge thus accumulated is read every line L as described above, converted into a voltage signal, and output to the imaging signal processing circuit 41. [

Hereinafter, a period in which each line is set in a state in which charge accumulation is possible is referred to as " charge accumulation period ".

Returning to Fig. 2, the image pickup signal processing circuit 41 sets each line on the image pickup element 40 to the charge accumulation period in turn, and reads the charge for each line. The imaging signal processing circuit 41 includes an A / D conversion circuit and converts a voltage signal for each line supplied from the imaging element 40 through a horizontal signal line 40g (see Fig. 3) into a digital signal , And outputs it to the control unit (50). The control unit 50 stores the digital signal (luminance signal) supplied from the imaging signal processing circuit 41 in the storage unit 60. [ In this way, one captured image is formed from the luminance signal of the entire line (one frame) output from the imaging signal processing circuit 41.

Figs. 4 (a) and 4 (b) are diagrams for explaining read control of the image pickup device 40. Fig. 4A is a diagram schematically showing a control (hereinafter referred to as " normal readout mode ") in the case where charge is read from each line at a normal speed. FIG. (Hereinafter referred to as " high-speed reading mode ") in the case of reading charges from the line.

On the left side of Figs. 4 (a) and 4 (b), the light receiving surface of the image pickup device 40 and each line L are schematically shown. Here, the uppermost line L is L0 and the lowermost line is Ln. On the right side of Figs. 4 (a) and 4 (b), the control timing for each line is schematically shown.

Referring to Fig. 4 (a), in the normal read mode, control for the uppermost line L0 starts at timing t1, and ends at timing t2. Control for the line L1 below the first stage is started later than the timing t1 by a predetermined time. Thus, each time the line L is changed to the lower end, the start timing is delayed by a predetermined time, and control for each line is sequentially performed. The start timing of the lowermost line Ln is the timing t2 delayed by? T from the timing t1.

At the uppermost line L0, charges are accumulated between the timing t1 and the timing t2. For example, all the periods? T between the timing t1 and the timing t2 become all the charge accumulation periods. The same charge accumulation period is set for the other line L as well. At the timing t2 when the period? T has elapsed from the timing t1, reading of the charge to the uppermost line L0 is carried out.

With respect to the second line L1, the accumulation of electric charges starts at a timing delayed from the timing t1 by a predetermined time, and reading of electric charges is performed at a timing delayed from the timing t2 by a predetermined time. Thus, every time the line L is changed, the start timing of charge accumulation is delayed by a predetermined time, and the execution timing of the charge reading is also delayed by a predetermined time. The start timing of the charge accumulation for the lowermost line Ln is the timing t2 delayed by Δt from the timing t1 and the execution timing of the charge readout becomes the timing t3 delayed by Δt from the timing t2.

Thus, in the normal read mode, the end timing of the charge accumulation with respect to the uppermost line L0 becomes the start timing of the charge accumulation with respect to the lowermost line Ln. Therefore, in the normal read mode, there is no occurrence of a period in which the charge accumulation periods of all the lines overlap each other.

Referring to FIG. 4 (b), in the high-speed read mode, the shift amount of the control start timing between the lines L is shortened in comparison with the normal read mode by increasing the charge reading speed with respect to each line L. In the example of Fig. 4 (b), the shift amount of the control start timing between the lines L is reduced to half as compared with the normal read mode. Therefore, the control start timing for the lowermost line Ln is delayed by? T / 2 from the start timing t1 of control for the uppermost line L0.

The readout speed of charges for each line L is increased by reducing the number of bits when sampling (A / D conversion) the charge signal of each line is smaller than the number of bits in the normal readout mode. This processing is performed by the imaging signal processing circuit 41 under the control of the control unit 50 in Fig. In the fast read mode, since the number of sampling bits is reduced in this way, the image quality of the captured image slightly deteriorates compared with the normal read mode. However, this deterioration is such that there is no particular problem in visibility in applications such as surveillance cameras and the like. Alternatively, it is possible to keep the same sampling bit number by improving and speeding up the image pickup device 40 and the image pickup signal processing circuit 41.

By setting the control mode for the image pickup device 40 to the high-speed read mode in this way, an overlap accumulation period in which the charge accumulation periods of all the lines overlap each other occurs as shown in Fig. 4 (b). By performing exposure in this overlap accumulation period, light from the target area is irradiated to each line L at the same timing, and charges are accumulated in the photodiodes 40a on all the lines L at the same timing and exposure amount do. Therefore, it is possible to suppress distortion of a captured image of a subject moving at high speed. That is, the rolling shutter effect is suppressed, and the global shutter function using the imaging element 40 is realized.

In the present embodiment, the control mode of the image pickup device 40 is set to the fast-read mode. Then, in the overlap accumulation period, the liquid crystal shutter 30 is opened, and the light from the target area is guided to the image pickup element 40. 2 controls the liquid crystal shutter 30 so that the light condensed at the lens 10 is irradiated to the light receiving surface of the image pickup element 40 at a predetermined timing during the overlapping accumulation period Open and close. The control unit 50 causes the shutter drive circuit 31 to stop applying the voltage to the liquid crystal shutter 30 to open the liquid crystal shutter 30 and then to apply the voltage to the liquid crystal shutter 30 The application of the voltage to the liquid crystal shutter 30 is started to close the liquid crystal shutter 30. Thus, for example, as shown in Fig. 4 (b), an exposure period for guiding light to the imaging element 40 is set within the overlapping accumulation period.

1 (a) and 1 (b), when the image pickup apparatus 1 is provided so as to pick up an intersection, the captured image picked up by the image pickup apparatus 1 is verified as a traffic accident or the like . In this case, it is desirable that the driver or the passenger of the vehicle causing the accident can be smoothly checked. However, since the intersection is exposed to the sunlight during the daytime, sunlight is reflected by the front glass of the vehicle 6, and the visibility in the car is markedly lowered by this reflection. This makes it difficult to identify the driver or passenger of the vehicle by the image picked up by the image pickup device 1. [

Thus, in the present embodiment, a configuration for acquiring a good sensed image even during the daytime is formed in the image sensing apparatus 1. [ Hereinafter, this configuration will be described.

First, with reference to Figs. 5 (a) and 5 (b), the reflection action of sunlight by the front glass will be described.

5 (a) is a graph showing the reflection characteristics of light of P polarized light and light of S polarized light. Fig. 5 (b) is a view schematically showing a state of incidence and reflection of light on a reflection surface of a front glass or the like. Fig.

Here, as shown in Fig. 5 (b), when the light beam is incident on and reflected by the reflection surface, the P polarized light is a light beam whose polarization direction is parallel to the surface (incident surface) including both incident light and reflected light Polarized state. The S polarized light refers to a polarized state in which the polarization direction is perpendicular to the surface (incident surface).

In general, the relationship between the angle (incident angle)? Of incident light with respect to the normal line set on the reflecting surface and the reflectance of P polarized light and S polarized light is as shown in Fig. 5 (a). In the graph of Fig. 5, the abscissa is the incident angle?, And the ordinate is the reflectance. The vertical axis is normalized by setting the maximum value to 1.

As shown in Fig. 5 (a), the component of the S-polarized light is predominant in the reflected light on the reflecting surface. Therefore, the reflected light of the light in the front glass also dominates the S polarized light component. Therefore, when the S polarized light component reflected by the front glass is removed at the time of image capturing, the influence of the reflection of the front glass on the captured image can be suppressed, and the visibility of the car can be improved.

Here, the front glass is inclined in the horizontal direction by a predetermined angle from the substantially vertical direction, and the sunlight is incident on the front glass from above. Therefore, the S polarized light component of the reflected light in the front glass is substantially parallel to the horizontal direction. In this embodiment, the liquid crystal shutter 30 is configured to remove the S polarized light component.

Figs. 6 (a) and 6 (b) schematically show the structure and operation of the liquid crystal shutter 30. Fig.

6A, the liquid crystal shutter 30 includes an incidence-side polarizing plate 301, two electrodes 302 and 303, and an output-side polarizing plate 304. As shown in Fig. A liquid crystal is filled between the two electrodes 302 and 303. Reference numeral 305 denotes a liquid crystal molecule. The polarization axis 301a of the incident-side polarization plate 301 and the polarization axis 304a of the exit-side polarization plate 304 are orthogonal to each other. The incident-side polarization plate 301 transmits only the light parallel to the polarization axis 301a and the exit-side polarization plate 304 transmits only the light whose polarization direction is parallel to the polarization axis 304a.

When no voltage is applied to the electrodes 302 and 303 as shown in Fig. 6A, the light taken through the lens 10 (see Fig. 2) is reflected by the polarization axis 301a Only the parallel light components transmit through the incidence-side polarizing plate 301. The light component is rotated 90 degrees by the liquid crystal molecules 305 while passing through the liquid crystal. That is, the liquid crystal molecules 305 are oriented so that the action of rotating the polarization direction by 90 degrees in such a state that no voltage is applied to the electrodes 302 and 303 is given to the light. In this way, the polarization direction of the light component transmitted through the incident-side polarization plate 301 becomes parallel to the polarization axis 304a of the exit-side polarization plate 304 by the action of the liquid crystal molecules 305. [ Thus, the light component passes through the exit-side polarization plate 304 and is guided to the image pickup element 40 (see Fig. 2).

As shown in Fig. 6 (b), when a voltage is applied to the electrodes 302 and 303, the liquid crystal molecules 305 are aligned in one direction. Therefore, the light component transmitted through the incident-side polarizing plate 301 reaches the output-side polarizing plate 304 without rotating the polarization direction. Therefore, the polarization direction of the light component is orthogonal to the polarization axis 304a of the exit-side polarization plate 304. [ Therefore, this light component is blocked by the exit-side polarization plate 304 and is not guided to the image pickup element 40 (see Fig. 2).

As described above, the liquid crystal shutter 30 transmits light in a state in which no voltage is applied to the electrodes 302 and 303, and blocks light in a state where a voltage is applied to the electrodes 302 and 303. The control unit 50 of Fig. 2 releases the application of the voltage to the electrodes 302 and 303 in the exposure period of Fig. 4 (b), and applies the voltage to the electrodes 302 and 303 in the other periods . Thereby, in the exposure period in the overlap accumulation period, the light from the target area is guided to the image pickup device 40. [

In this embodiment, by adjusting the direction of the polarization axis 301a of the incident-side polarizing plate 301, the light of the S-polarized component reflected by the front glass is blocked by the incident-side polarizing plate 301. [

7 is a front view schematically showing the positional relationship between the apparatus main body 101 of the image pickup apparatus 1, the incident-side polarization plate 301 and the image pickup element 40. Fig.

7, the liquid crystal shutter 30 is arranged such that the vertical direction of the apparatus main body 101 is parallel to or substantially parallel to the polarization axis 301a of the incident-side polarizing plate 301. As shown in Fig. Here, as shown in Fig. 1, the image pickup apparatus 1 is installed such that the vertical direction of the apparatus main body 101 is along the vertical direction. Therefore, when the liquid crystal shutter 30 is arranged such that the vertical direction of the apparatus main body 101 is parallel or substantially parallel to the polarization axis 301a of the incident-side polarization plate 301, the polarization axis 301a of the incident- , And is substantially parallel to the plane perpendicular to the horizontal plane.

On the other hand, in the light reflected by the front glass of the vehicle, the polarization direction Rs of the S polarization component is horizontal and the polarization direction Rp of the P polarization component is perpendicular to the polarization direction Rs. Thus, when the incident-side polarization plate 301 is arranged such that the polarization axis 301a is parallel or substantially parallel to the vertical direction of the apparatus main body 101 as described above, the polarization direction Rs of the light of the S polarization component reflected by the front glass Is substantially perpendicular to the polarization axis 301a of the incident-side polarization plate 301. [ Therefore, the S-polarized light component reflected by the front glass is blocked by the incidence-side polarizing plate 301, and only the P-polarized light component passes through the incidence-side polarizing plate 301. Thereby, the S-polarized light component dominant in the light reflected by the front glass is excluded by the incidence-side polarizing plate 301.

As described above, in this embodiment, since the S polarized light component dominant in the light reflected by the front glass is excluded by the incident-side polarizing plate 301, the influence of the reflection of the front glass in the sensed image is suppressed . As a result, the visibility of the vehicle can be enhanced.

Fig. 8 (a) is a diagram showing a picked-up image in which the front glass of the vehicle is actually picked up by the image pickup apparatus 1 having the configuration of the above embodiment. Fig. 8 (b) is a diagram showing a picked-up image in which a front glass of a vehicle is actually picked up by a general camera (comparative example). Fig.

As shown in Fig. 8 (b), in a picked-up image in which a front glass of a vehicle is photographed by a general camera (comparative example), a situation in which the inside of the car can not be visually recognized due to reflection of sunlight in the front glass Respectively.

On the other hand, in the captured image obtained by picking up the front glass of the vehicle by the image pickup apparatus 1 having the configuration of the above embodiment, reflection of sunlight in the front glass is effectively suppressed as shown in Fig. 8 (a) And the visibility of the captured image is improved to such an extent that the inside of the car can be satisfactorily confirmed. From the result of the verification, the effect of improving the visibility by the constitution of the above embodiment was confirmed.

≪ Effect of Embodiment >

According to the present embodiment, the following effects are obtained.

The light component of the S-polarized light reflected by the front glass of the vehicle is shielded by the incidence-side polarizing plate 301. [ Therefore, sunlight is reflected from the front glass of the vehicle, thereby suppressing deterioration in visibility of the vehicle. Therefore, even during the daytime, it is possible to acquire a sensed image capable of smoothly checking the inside of the car.

The controller 50 is configured to cause the charge accumulation period of each line on the image pickup element 40 to overlap with each other Thereby controlling the image pickup device 40. In addition, the control unit 50 opens the liquid crystal shutter 30 within the overlap accumulation period in which the charge accumulation periods overlap with all the lines. Thereby, since the imaging element 40 is exposed during the overlap accumulation period, the light in the target area is irradiated to the imaging element 40 in all the lines in the same timing and exposure period. Therefore, even when a subject moving at high speed is included in the target area, no distortion occurs in the picked-up image of the subject.

In the image pickup apparatus according to the present embodiment, the image sensor has a function of a high-speed reading mode for outputting a signal at a high speed, and the image sensor control unit sets the control mode for the image sensor to the high- , The overlap accumulation period is generated. According to this configuration, since the distortion of the picked-up image is suppressed by using the high-speed read mode, the distortion of the object can be suppressed while maintaining the frame transfer rate of the picked-up image.

<Example of change>

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications may be made to the embodiments of the present invention.

For example, in the above embodiment, as shown in Fig. 4 (b), the overlap accumulation period is generated by setting the control mode of the image pickup device 40 to the high speed read mode. However, Likewise, by setting the control mode of the image pickup element 40 to the low speed mode, a redundant accumulation period may be generated. In the low speed mode, the imaging period of each line is set to twice the normal read mode shown in Fig. 9 (a), i.e., 2? T. Also in this case, the liquid crystal shutter 30 is controlled to be opened, for example, in a redundant accumulation period. That is, in the overlap accumulation period, the exposure period for guiding light to the image pickup device 40 is set. By setting the exposure period in this manner, even when a subject moving at high speed is included in the target area, no distortion occurs in the captured image of the subject.

In the above embodiment, a liquid crystal shutter having a normally white type property is used as the liquid crystal shutter 30. However, a liquid crystal shutter having a normally black type property may be used as the liquid crystal shutter 30. [

When the liquid crystal shutter 30 having the characteristics of the normally black type is used, the liquid crystal molecules 305 are aligned in the state in which no voltage is applied to the electrodes 302 and 303, as shown in Fig. 6 (b) So that the light from the target area is blocked by the exit-side polarizing plate 304. 6 (a), the liquid crystal molecules 305 are oriented so that the light from the target region passes through the exit-side polarizing plate 304. In this case, as shown in Fig.

Even when the liquid crystal shutter 30 having the normally black type property is used, the vertical direction of the apparatus main body 101 is parallel to the polarization axis 301a of the incident-side polarizing plate 301, By arranging the incident-side polarizers 301 so that they are parallel or substantially parallel, light of S-polarized light reflected by the front glass of the vehicle is shielded by the incident-side polarizers 301. Therefore, sunlight is reflected from the front glass of the vehicle, thereby suppressing deterioration in visibility of the vehicle. Therefore, even during the daytime, it is possible to acquire a sensed image capable of smoothly checking the inside of the car.

However, for the following reason, it is preferable to use a liquid crystal shutter having a characteristic of the normally white type rather than a liquid crystal shutter having the characteristic of the normally black type as the liquid crystal shutter 30. [

The liquid crystal shutter 30 is different in the rate of change of the transmittance at the start of the voltage application and at the time of stopping the voltage application, depending on the characteristics of the liquid crystal. Generally, the rate of change of the transmittance when the voltage is applied is fast, but the rate of change of the transmittance when the application of the voltage is stopped is gentle. This is because the rate of change of the transmittance when the application of the voltage is stopped depends on the viscosity of the liquid crystal and it takes time for the order of the liquid crystals to return to the original direction.

Due to the characteristics of the liquid crystal, for example, in a so-called normally black type liquid crystal shutter in which the transmittance is low in a state where a voltage is not applied and the transmittance is increased when a voltage is applied, The transmittance is maximized. However, even if the application of the voltage is stopped, the transmittance is not returned to the minimum value. Therefore, when the normally black type liquid crystal shutter is used as the liquid crystal shutter 30, the exposure time for the image pickup device 40 becomes longer than the desired length, and thus the image picked up by the subject tends to be shaken.

On the other hand, in a so-called normally white type liquid crystal shutter in which the transmittance is maximized when no voltage is applied and the transmittance is lowered when a voltage is applied, after the application of the voltage is stopped, However, when the application of the voltage is started, the transmittance quickly returns to the minimum value. Therefore, when the normally white liquid crystal shutter is used as the liquid crystal shutter 30, the exposure time for the image pickup device 40 does not become longer than the expected time, and the image picked up by the subject is not shaken effectively .

For the above reasons, it is preferable to use a normally white liquid crystal shutter as the liquid crystal shutter 30 as in the above embodiment. Thus, it is possible to effectively suppress the occurrence of a blur in the captured image of the subject.

In the above embodiment, the light component of S-polarized light reflected by the front glass is taken in by the lens 10, and then, with the assumption that the polarized light reaches the liquid crystal shutter 30 as it is without rotating, The direction of the polarization axis 301a of the liquid crystal panel 301 is set. On the other hand, if the optical system from the lens 10 to the liquid crystal shutter 30 is designed so that the polarization direction of the light component of the S-polarized light reflected by the front glass is rotated by a predetermined angle after being captured by the lens 10 The direction of the polarization axis 301a of the incident-side polarizing plate 301 is set so that the direction of polarization of the S-polarized light component reflected by the front glass is substantially perpendicular to the polarization axis 301a at the position of the incident- Good when adjusted. That is, the light component in the polarization direction (polarization direction parallel to the horizontal direction) perpendicular to the up-and-down direction of the apparatus main body 101 is transmitted through the lens 10 and then incident on the incidence-side polarization plate 301 of the liquid crystal shutter 30 The polarization axis 301a of the incident-side polarization plate 301 may be set so as to be blocked by the polarization axis 301a. As a result, the light component of the S-polarized light reflected by the front glass can be removed by the incidence-side polarizing plate 301, similarly to the above embodiment.

In the above-described embodiment, an example in which the intersection is photographed by the image capturing apparatus 1 is shown. However, the image capturing region may not necessarily be an intersection point, or may be another region through which the vehicle passes.

In the above embodiment, the imaging apparatus 1 is provided on an outer wall or roof structure of a building, a telephone pole, or the like. However, for example, the structure of the imaging apparatus 1 may be integrated into a streetlight or the like. Further, the image pickup apparatus 1 is not limited to a surveillance camera, and may be another image pickup apparatus.

In addition to the above, the embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

1: Imaging device
10: Lens
30: liquid crystal shutter
40: active element
50:
301: incident-side polarization plate
301a: polarization axis
304: Outgoing-side polarizer

Claims (4)

An image pickup element,
A lens that focuses light from the target area on the imaging element,
And a liquid crystal shutter disposed on the side of the target area with respect to the imaging element,
Wherein the liquid crystal shutter includes an incidence-side polarizer and an exit-side polarizer, and the light component in the polarization direction perpendicular to the up-and-down direction of the apparatus main body is transmitted through the lens and then blocked by the incidence- When the polarizing axis of the polarizing plate is set
And the image pickup device. The method according to claim 1,
Side polarization plate is arranged such that the vertical direction of the apparatus main body is substantially parallel to the polarization axis of the incident-side polarization plate. 3. The method according to claim 1 or 2,
And a control unit for controlling the image pickup element and the liquid crystal shutter,
The imaging element accumulates and outputs charges corresponding to the amount of light received by each line,
Wherein,
The image pickup element is controlled so that a part of the charge accumulation period in each line on the image pickup element overlaps with each other,
And said liquid crystal shutter is opened within an overlap accumulation period in which charge accumulation periods overlap with all of said lines. The method of claim 3,
The imaging device has a function of a high-speed reading mode for outputting a signal at high speed,
Wherein the control section sets the control mode for the image pickup element to the fast readout mode to generate the overlap accumulation period.

Images