JP6233735B2 - Imaging device for monitoring and control method thereof - Google Patents

Description

  The present invention relates to an image pickup apparatus that picks up an image while illuminating a subject, and more particularly to an image pickup apparatus that picks up an image of a road or a building site for the purpose of crime prevention or monitoring, and a control method thereof.

  Imaging devices that image roads, building sites, etc. for the purposes of crime prevention and surveillance are widely used. In this type of imaging apparatus, an illumination unit that illuminates the subject is provided so that a good captured image can be obtained even at night. In this illumination section, it is necessary to adjust the light distribution characteristics so that the necessary illumination area corresponding to the imaging area can be illuminated with uniform illuminance. However, if the projection distance from the imaging device to the subject changes, the illuminance distribution Also changes. For this reason, there has been a problem that it is difficult to divert what is set so that an appropriate illuminance distribution can be obtained at a specific projection distance to an application having a significantly different projection distance.

  As related to the problem that the illuminance distribution of the subject changes according to the projection distance in this way, a plurality of lenses having different cross-sectional shapes are arranged opposite to each other, and light emission composed of the light source and the lens is arranged. A technique in which the light distribution characteristics are different for each part is known (see Patent Document 1). According to this, it is possible to obtain an appropriate light amount distribution for each photographing mode such as when using a standard lens, when using a telephoto lens, when using a wide-angle lens, or when performing macro photography by lighting together a plurality of light emitting units.

JP 2007-180520 A

  The prior art relates to an imaging device built in a mobile phone or the like. In such an application, the size of the imaging region of the subject increases as the distance from the imaging device to the subject increases. Become. For example, when shooting three people, the distance between the imaging device and the subject is longer and the imaging range is wider than when shooting one person, and the illumination range that illuminates the imaging range is also expanded. However, as described above, in an imaging device that captures roads or building sites for crime prevention or the like, the imaging area (the subject or range to be monitored) is set in advance, regardless of the distance to the imaging area. The imaging device is installed at a position where the subject or the like can be imaged, and the size of the imaging region does not change greatly according to the distance from the imaging device to the subject. That is, in the monitoring application, the imaging range may be regulated to be substantially constant (for example, within a circle with a radius of 5 m or within a rectangle with a size of 5 m × 5 m) regardless of the distance from the imaging device to the subject. However, it is necessary to illuminate the imaging range with an appropriate amount of light.

  For this reason, as in the above-described conventional technique, the lighting control based on the premise that the imaging region becomes larger as the distance to the subject becomes longer, and the imaging used for the application in which the size of the imaging region does not change according to the distance. Even if it is applied to the apparatus, an appropriate lighting state cannot be obtained. In other words, when the distance to the subject is short, the illuminance becomes excessive at the center of the illumination area, resulting in overexposure in the captured image. On the other hand, when the distance to the subject is long, the necessary illumination area Diffusing light in an unnecessary direction outside causes problems that the illuminance at the subject is insufficient (light quantity is insufficient) and power is wasted.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to appropriately set the necessary illumination area corresponding to the imaging area even when the distance to the subject is greatly different. Another object of the present invention is to provide an imaging apparatus configured to illuminate with a high illuminance and to suppress unnecessary illumination outside a necessary illumination area, and a control method thereof.

An imaging apparatus according to the present invention is an imaging apparatus that images a subject while illuminating an imaging region, and is arranged with a first illuminating unit that emits infrared light and an infrared image that is arranged with the first illuminating unit interposed therebetween. It comprises a second illumination means for emitting light, and at least including a lighting portion and an output control means for controlling the output of the illumination portion, the said first illuminating means illuminating a central portion of the imaging region So that the light distribution characteristic of emitting light in the first emission angle range is set, and the second illuminating means illuminates the area shifted outward from the center of the imaging area . When the light distribution characteristic is set so that light is emitted in a second emission angle range shifted from the emission angle range, and the distance to the subject is short, the output control means and configured to perform output restriction containing off.

The control method of the imaging apparatus of the present invention includes at least a first illumination unit that emits infrared light, and a second illumination unit that is arranged with the first illumination unit interposed therebetween and emits infrared light. an illumination unit, the first lighting unit is set to the light distribution characteristic of emitting light in a first emission angle range so as to illuminate the center of the imaging region, the second illumination means, the An imaging apparatus control method set to a light distribution characteristic that emits light in a second emission angle range shifted from the first emission angle range so as to illuminate a region shifted outward from the center of the imaging region. there are, in the case the distance to the subject is short, and configured to perform output restriction containing off to the first lighting unit.

According to the present invention, it is possible to illuminate the necessary illumination area corresponding to the imaging area with appropriate illuminance and suppress unnecessary illumination outside the necessary illumination area even when the distance to the subject is greatly different. In particular, when the distance to the subject is short, by restricting the output to the first illumination means, it is possible to avoid excessive illuminance at the center of the necessary illumination area. As a result, when installing an imaging device for crime prevention or surveillance purposes, it is difficult to see the illumination light from the person in the illumination area by keeping the output low so as to satisfy the required illuminance at a short distance. Sex can be secured.

The perspective view which shows the imaging device 1 which concerns on 1st Embodiment. Side view showing the installation status of the imaging apparatus 1 Block configuration diagram of the imaging apparatus 1 Front view of imaging device 1 Front view of illumination unit 3 Side view of lighting units 41 and 42 Front view of the first lighting unit 41 The front view which shows separately the light source board | substrate 45 and the lens array 46 which comprise the 1st illumination unit 41 Sectional drawing which shows light emission parts 33a-33d (light source 31 and lens 32) for every illumination group AD Front view showing a modification of the first lighting unit 41 The front view which shows separately the light source board | substrate 45 and the lens array 46 which comprise the 1st illumination unit 41 shown in FIG. Explanatory drawing which shows the output control condition of the light source 31 in each illumination mode of short distance, medium distance, and long distance Explanatory drawing which shows the drive current value in each illumination group AD by a graph Explanatory diagram showing the illuminance distribution in the short-distance, medium-distance, and long-distance illumination modes in a graph The top view which shows typically the state of the illumination by a conventional structure and this embodiment The block block diagram of the imaging device 61 which concerns on 2nd Embodiment. Front view of imaging device 61 Explanatory drawing which shows the state of distance measurement by the imaging device 61 Flow chart showing a procedure of processing performed in the imaging device 61 Explanatory drawing which shows the status of the distance measurement by 3rd Embodiment Explanatory drawing which shows the condition of the current control of the light source 31 which concerns on 4th Embodiment with a graph Explanatory drawing which shows the condition of the illumination distribution measurement by 5th Embodiment

A first invention made to solve the above-described problem is an imaging apparatus that images a subject while illuminating an imaging region, and includes a first illumination unit that emits infrared light, and the first illumination unit. a second illumination means is arranged to emit infrared light across at least including a lighting portion and an output control means for controlling the output of the illumination unit, wherein the first illumination means, The light distribution characteristic is set so that light is emitted in a first emission angle range so as to illuminate the central portion of the imaging region , and the second illuminating means is configured to detect an area shifted outward from the central portion of the imaging region. The light distribution characteristic is set to emit light in a second emission angle range that is shifted from the first emission angle range so as to illuminate , and the output control means, when the distance to the subject is short, configuration and performing output restriction containing off the first illumination means That.

According to this, even when the distance to the subject is greatly different, it is possible to illuminate the necessary illumination area corresponding to the imaging area with an appropriate illuminance and suppress unnecessary illumination outside the necessary illumination area. In particular, when the distance to the subject is short, by restricting the output to the first illumination means, it is possible to avoid excessive illuminance at the center of the necessary illumination area. As a result, when installing an imaging device for crime prevention or surveillance purposes, it is difficult to see the illumination light from the person in the illumination area by keeping the output low so as to satisfy the required illuminance at a short distance. Sex can be secured.

According to a second aspect of the present invention, the illumination unit further includes a third illumination unit that emits infrared light, the first illumination unit is disposed with the third illumination unit interposed therebetween, and the third illumination unit The illumination means illuminates an area shifted outward from the first illumination means, the second illumination means illuminates an area shifted outward from the third illumination means, and the output control means When the distance to the subject is short, the first illumination unit is turned on with an output equal to or less than the third illumination unit, and when the distance to the subject is long, the first illumination unit is turned on. It is set as the structure which lights similarly to the said 3rd illumination means .

  In the third aspect of the invention, the illumination unit further includes third illumination means for emitting infrared light, the first illumination means is disposed with the third illumination means interposed therebetween, and the third illumination means The illumination means illuminates an area shifted outward from the first illumination means, the second illumination means illuminates an area shifted outward from the third illumination means, and the output control means When the distance to the subject is short, the third illumination unit is turned on with output limited to that of the second lighting unit, and when the distance to the subject is long, the third illumination unit is turned on. The means is lit in the same manner as the second lighting means.

According to the second and third inventions, it is difficult to see the illumination light from the person in the illumination area, it is possible to ensure confidentiality, while avoiding excessive illuminance at the center of the necessary illumination area, The required illuminance can be satisfied over the entire required illumination area .

According to a fourth aspect of the present invention, the output control means divides the distance to the subject into three cases: a short distance, a medium distance, and a long distance, according to a first distance and a second distance shorter than the first distance. Thus, the output of the illumination unit is controlled.

  According to this, since it is sufficient to divide into three cases, it is possible to eliminate the troublesomeness when the user selects, and to illuminate the necessary illumination area with an appropriate illuminance with a practically sufficient level and necessary illumination. Unnecessary illumination outside the area can be suppressed.

In the fifth invention, the output control means turns off the first lighting means and turns on the second lighting means when the distance is short, and turns on the second lighting means when the distance is short. The second illuminating means is turned on and the first illuminating means is lit with an output limited to that of the second illuminating means. In the case of the long distance, the first illuminating means and the second illuminating means are turned on . Both of the illumination means are turned on.

  According to this, it is possible to illuminate the necessary illumination area with an appropriate illuminance and suppress unnecessary illumination outside the necessary illumination area in any of short distance, medium distance, and long distance.

In addition, according to a sixth aspect of the present invention, the output control means turns on the third illumination means with an output more limited than the second illumination means in the case of the short distance and the intermediate distance, In the case of a distance, the third lighting unit is turned on in the same manner as the second lighting unit.

According to a seventh aspect of the invention, the output control means turns on the first illumination means in the same manner as the third illumination means at the intermediate distance and the long distance.

In an eighth aspect of the invention, the third illuminating means emits light in a third emission angle range between the first emission angle range and the second emission angle range.

In the ninth invention, the illumination unit further includes fourth illumination means for emitting infrared light, and the fourth illumination means is disposed with at least a part of the second illumination means interposed therebetween. When the distance to the subject is short, the output control means illuminates the area shifted outward from the second illumination means, and the fourth illumination means is the same as the second lighting means. When the distance to the subject is long, the fourth illumination unit is configured to limit output including turning off.

  According to a tenth aspect of the present invention, the illumination unit further includes a fourth illumination unit that emits infrared light, and the fourth illumination unit is disposed across at least a part of the second illumination unit. Illuminating a region shifted outward from the second illuminating means, and the output control means, in the case of the short distance and the intermediate distance, the fourth illuminating means as the second lighting means. Similarly, the light is turned on, and in the case of the long distance, the fourth lighting unit is configured to limit output including turning off.

  According to the ninth and tenth aspects of the invention, the illumination light cannot be seen from a person outside the necessary illumination area at a long distance, and confidentiality can be ensured.

In an eleventh aspect of the invention, the fourth illumination unit emits light in a fourth emission angle range that is larger than any of the first emission angle range to the third emission angle range. .

In a twelfth aspect of the invention, each of the illuminating units includes a light source and a lens that collects light emitted from the light source. In the first illuminating unit, the light source and the lens include: The optical axis of the light source and the central axis of the lens are arranged in a relatively shifted state with a first shift amount. In the second illuminating means, the light source and the lens are aligned with the optical axis of the light source. The lens is arranged so as to be relatively displaced from the central axis of the lens by a second shift amount larger than the first shift amount.

  According to this, by relatively shifting the optical axis of the light source and the central axis of the lens, the emission angle range can be changed without changing the cross-sectional shape of the lens. Cost can be kept low.

In a thirteenth aspect of the present invention, a plurality of the lenses are arranged at regular intervals, and a plurality of the light sources are arranged in a state where an optical axis is deviated from a central axis of the lens.

  According to this, since the size of the light source is smaller than that of the lens, it is only necessary to shift the light source within the width of the lens, which allows a plurality of lenses to be closely arranged, thereby reducing the size of the apparatus. be able to.

The fourteenth aspect of the invention further includes a distance measuring unit that measures the distance to the subject, and the output control means controls the output of the illumination unit based on the distance acquired by the distance measuring unit. To do.

  According to this, it is possible to save the user the trouble of measuring the distance using the measuring instrument and the input operation necessary for the imaging device so as to perform the control corresponding to the measurement distance. Improves.

In addition, the fifteenth aspect of the present invention is an illumination unit including at least a first illumination unit that emits infrared light and a second illumination unit that is disposed with the first illumination unit interposed therebetween and emits infrared light. The first illumination means is set to a light distribution characteristic of emitting light in a first emission angle range so as to illuminate a central portion of the imaging area, and the second illumination means is configured to emit light in the imaging area. A method for controlling an imaging apparatus set to a light distribution characteristic that emits light in a second emission angle range shifted from the first emission angle range so as to illuminate a region shifted outward from the center of when the distance to the subject is short, and configured to perform output restriction containing off to the first lighting unit.

According to this, even when the distance to the subject is greatly different, it is possible to illuminate the necessary illumination area corresponding to the imaging area with an appropriate illuminance and suppress unnecessary illumination outside the necessary illumination area. In particular, when the distance to the subject is short, by restricting the output to the first illumination means, it is possible to avoid excessive illuminance at the center of the necessary illumination area. As a result, when installing an imaging device for crime prevention or surveillance purposes, it is difficult to see the illumination light from the person in the illumination area by keeping the output low so as to satisfy the required illuminance at a short distance. Sex can be secured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing an imaging apparatus 1 according to the first embodiment. The imaging device 1 includes an imaging unit 2 that images a subject, an illumination unit 3 that illuminates the subject, and a housing 4 that houses the imaging unit 2 and the illumination unit 3. The casing 4 has a box shape with a bottom, an upper open portion thereof is covered with an upper cover 5, and a sunshade 6 is further provided on the upper side thereof. An imaging window 7 and an illumination window 8 made of a cover glass are provided side by side on the front side of the housing 4, and illumination light emitted from the illumination unit 3 is emitted through the illumination window 8, and the subject Light enters the imaging unit 2 through the imaging window 7.

  FIG. 2 is a side view showing an installation state of the imaging apparatus 1. The image pickup apparatus 1 is installed at a required height (for example, 2 m to 5 m) while being supported by the support column 11, and subjects such as persons or vehicles existing on the road or building site for crime prevention or surveillance purposes. Take an image. The illumination unit 3 of the imaging device 1 uses a light source that emits infrared light, which enables imaging without being noticed by a person, without harming the landscape, and particularly excellent transparency. By using a light source that emits near-infrared light, imaging can be performed without being affected by rainfall or fog.

  In addition, the imaging apparatus 1 is used by switching the illumination mode according to the light projection distance from the imaging apparatus 1 to the subject. In particular, in the present embodiment, the first distance (for example, 15 m) and the second distance (for example, 10 m) shorter than the first distance (for example, 5 m to 10 m), the middle distance (for example, 10 m to 15 m), and the long distance There are three cases (for example, 15 to 30 m), and the corresponding illumination mode is selected according to the projection distance.

  The setting of the illumination mode is performed when the apparatus is installed, and is performed when the imaging position is changed. The projection distance from the imaging apparatus 1 to the subject is measured using an appropriate measuring instrument, and the measurement distance is measured. The user selects and sets the illumination mode according to the above.

  In addition to the imaging unit 2 and the illumination unit 3, a control board (not shown) that drives the imaging unit 2 and the illumination unit 3 is accommodated in the housing 4 of the imaging apparatus 1 illustrated in FIG. In addition, interfaces 24 and 25 (see FIG. 3) necessary for communication with an external device and an input operation unit 26 (see FIG. 3) for performing various input operations by the user are provided. The controller 12 is provided separately from the housing 4 as shown in FIG. The controller 12 is installed near the ground so that the user can easily work, and is connected to the control board in the housing 4 via the cable 13.

  FIG. 3 is a block configuration diagram of the imaging apparatus 1. The imaging device 1 includes the imaging unit 2 and the illumination unit 3, a drive unit 21 that drives the illumination unit 3, a storage unit (memory) 22 that stores image data obtained by imaging with the imaging unit 2, and An encryption / encoding unit 23 that encrypts and encodes image data, an output interface 24 and an input interface 25 that transmit and receive data via a network (such as the Internet), and various input operations by a user. An input operation unit 26 is provided, and a control unit 27 that controls each unit in an integrated manner.

  The control unit 27 includes a ROM that stores a program, a CPU that executes the program, a RAM that is used as a work area, and a timing generator that generates a control signal for the imaging unit 2, for example.

  The illuminating unit 3 includes a plurality of light emitting units 33 a to 33 d configured by a light source 31 and a lens 32. The light source 31 is an infrared LED that emits infrared light (for example, near infrared light). The lens 32 is a condensing lens (for example, a collimating lens) that collects light emitted from the light source 31. The light emitting units 33a to 33d are grouped into four illumination groups A to D. The drive unit 21 includes a drive circuit 34 that drives the light source 31 of the light emitting units 33a to 33d. The drive circuit 34 is a constant current power source provided for each of the four illumination groups A to D of the light emitting units 33a to 33d, and the light source 31 is controlled in units of the four illumination groups A to D.

  The light source 31 can change the output (light emission luminance) by increasing or decreasing the drive current value applied from the drive circuit 34. Each drive circuit 34 has a DA converter (not shown), and outputs a drive current based on a drive control signal (digital value) output from the CPU of the control unit (output control means) 27. The drive current value can be changed by a predetermined number of steps (for example, 0 to 255) according to the drive control signal, and the output (light emission brightness) of the light source 31 is controlled by increasing or decreasing the drive current value. Further, the control unit 27 outputs a pulse signal having a predetermined time width from the timing generator, and each drive circuit 34 drives the light source 31 for the ON duty time of the pulse signal. That is, in this embodiment, the LED as the light source 31 is PWM driven. The timing at which the light source 31 is turned on and off is the same for the lighting groups A to D. For example, when all the lighting groups A to D are turned on, the light source 31 is turned on synchronously between the lighting groups. Repeat turning off. By this intermittent drive, light emission with extremely high luminance can be obtained instantaneously. The period during which each light source 31 is lit (ON duty period) is controlled by the timing generator so as to be included in the exposure period of the image sensor 35 described later.

  The imaging unit 2 includes, for example, a CMOS (Complementary Metal Oxide Semiconductor) type image sensor 35. As described above, since the light emission of the light source 31 is performed periodically, the global shutter method is adopted so that the exposure timing (period length) of each pixel constituting the CMOS is the same. The image sensor 35 outputs image data at a required frame rate (for example, 30 fps). The image data is digitized by an AD converter 36 and is processed by an image processing unit 37 for a normal monochrome image such as γ correction. After image processing, the image data is temporarily stored in the storage unit 22 as single-color image data. Note that the imaging unit 2 does not include a so-called IR cut filter in order to capture reflected light from a subject illuminated with infrared light emitted from the illumination unit 3.

  The image data stored in the storage unit 22 can be directly referred to from the CPU of the control unit 27. In particular, the CPU of the control unit 27 can forcibly write the data in a specific memory area (that is, a part of the image). For example, information such as identification information and imaging time of the imaging device 1 can be directly merged with the image.

  The encryption / encoding unit 23 performs encryption and encoding necessary for sending the image data stored in the storage unit 22 from the output interface 24 to the network. In this encryption and encoding, processing such as conversion into a packet signal compatible with TCP / IP is performed. The image data output from the encryption / encoding unit 23 is transmitted from the output interface 24 to an external device at a remote location via the network, and the image can be viewed on the external device. Monitoring is realized.

  In addition, various operations of the imaging device 1 can be instructed from an external device via a network. For example, in the imaging unit 2, the image data is output as a moving image or a still image captured at a predetermined time interval, and an imaging mode for outputting the moving image or the still image is instructed from an external device. The operation instruction signal from the external device is received by the input interface 25 via the network, and the control unit 27 controls the imaging unit 2 based on the operation instruction signal.

  In addition, the same operation instruction can be given by the input operation unit 26 provided in the imaging apparatus 1 itself. As described above, when the imaging apparatus 1 is installed, an operation for setting the short-distance, medium-distance, and long-distance illumination modes is performed. The illumination mode is set by the input operation unit 26. The control unit controls the drive unit 21 in accordance with this operation.

  In this example, the image data is transmitted to an external device at a remote location via a network. However, the imaging device 1 or the controller 12 includes a reader / writer that reads and writes the recording medium, and the image data is stored on the recording medium. The image data may be stored so that the image can be browsed by reading the image data from the recording medium with an image reproduction device such as a PC. In addition, a so-called mass storage device such as a hard disk drive (HDD) or a solid state drive (SSD) may be provided and recorded.

  FIG. 4 is a front view of the imaging apparatus 1. 4, the cover glass which comprises the illumination window 8 provided in the front surface of the illumination part 3 in FIG. 1 is abbreviate | omitted and shown. The illumination unit 3 includes a first illumination unit 41 and a second illumination unit 42.

  FIG. 5 is a front view of the illumination unit 3. In each of the first and second illumination units 41 and 42, a plurality of light sources 31 constituting the light emitting portions 33a to 33d are two-dimensionally arranged, and the lenses 32 are also two-dimensionally corresponding to the light sources 31 respectively. Are arranged in multiple numbers. In particular, here, a total of 35 light sources 31 and lenses 32 are arranged, with 5 in the X-axis direction and 7 in the Y-axis direction. In the following description, the arrow direction of the X axis is defined as + and the opposite is defined as −.

  FIG. 6 is a side view of the lighting units 41 and 42. The light source 31 is a surface-mount type surface emitting infrared LED, and is disposed on the light source substrate 45. The lens 32 is integrally formed of a light transmissive material such as acrylic resin (PMMA) to form a lens array (lens assembly) 46. All the lenses 32 are aspherical lenses that are point-symmetric with respect to the optical axis C2 and have the same cross-sectional shape.

  As shown in the drawing, the light emission side of the light source 31 has a dome shape and has a specific light distribution characteristic. In consideration of the light distribution characteristics of the light source 31, the lens 32 has a characteristic in which the irradiation range becomes wider as the light projection distance finally becomes longer. Specifically, when the optical axis of the light source 31 and the optical axis of the lens 32 are matched, the light emitting area (about 1 mm × 1 mm) of one light source 31 is about 5 m at a distance of 30 m from the imaging device 1. It has a light distribution characteristic that expands to 5 m. Then, the light emitted from the light source 31 is overlapped in the irradiation region (to be exact, is shifted by the arrangement pitch P (see FIG. 8) for each light source 31) to form one light spot. The light distribution characteristic is a light intensity distribution by illumination, and can be controlled mainly by an emission angle range.

  The light source substrate 45 and the lens array 46 are fixed and integrated with a bracket 47, and are particularly fastened by screws 48 here. A spacer 49 is interposed between the light source substrate 45 and the lens array 46, whereby the light source 31 and the lens 32 are held at a constant interval.

  As shown in FIG. 5, in the 1st lighting unit 41 and the 2nd lighting unit 42, light emission parts 33a-33d (light source 31 and lens 32) are divided into four lighting groups AD according to a light distribution characteristic. Grouped. The grouping according to the light distribution characteristics is symmetrical between the first lighting unit 41 and the second lighting unit 42. Below, the light distribution characteristic of the light emission parts 33a-33d is demonstrated.

  FIG. 7 is a front view of the first lighting unit 41. FIG. 8 is a front view showing separately the light source substrate 45 and the lens array 46 constituting the first illumination unit 41. 7 and 8, only the first lighting unit 41 arranged on the left side is shown. However, the second lighting unit 42 arranged on the right side is different from the first lighting unit 41 in the left and right directions. Appears symmetrically.

  As shown in FIG. 7, the light source 31 and the lens 32 include the optical axis of the light source 31 (pointing to a normal passing through the intersection of diagonal lines of the surface emitting portion (usually square or rectangular) of the LED) and the central axis of the lens 32 ( The optical axis of the light source 31 and the central axis of the lens 32 are offset so that they are relatively parallel to each other in a state in which the geometrical optical center axis is substantially parallel. In particular, in the present embodiment, the lenses 32 are arranged at regular intervals P in the X and Y directions, and the light source 31 is arranged so that the optical axis is shifted in the X direction with respect to the central axis of the lenses 32. That is, as shown in FIG. 8B, in the lens array 46, the lenses 32 are arranged at a constant interval P (for example, 12 mm). As shown in FIG. The light source 31 is arranged so that the optical axis of the light source 31 is deviated from the central axis of 32.

  As described above, the light source 31 and the lens 32 are arranged so that the optical axis of the light source 31 and the center axis of the lens 32 are relatively shifted, and according to the optical axis shift width (shift amount), the light source 31 and the lens 32 are arranged. The light distribution characteristics of the light emitting portions 33a to 33d formed of the lens 32 are different.

The light emitting units 33a to 33d (light source 31 and lens 32) are grouped into four illumination groups A to D according to the optical axis shift width (shift amount). Five constituting the innermost row constitute the lighting group B (third illumination means), and 20 constituting each row from the second row to the fifth row counted from the inner side constitute the lighting group A (first illumination means). 7 that constitute a part of the second row and the outermost one row from the outside are the illumination group C ( second illumination means ) and constitute a part of the outermost row. The three to be used are the illumination group D ( fourth illumination means ).

  The optical axis shift width (first shift amount) Sa of the illumination group A is +0.2 mm in the X-axis direction, and the optical axis shift width (third shift amount) Sb of the illumination group B is +0.4 mm in the X-axis direction. The optical axis shift width (fourth shift amount) Sc of the illumination group C is +0.9 mm in the X-axis direction, and the optical axis shift width (second shift amount) Sd of the illumination group D is +2.7 mm in the X-axis direction. Each is set. The optical axis shift width is not particularly limited, and may be set as appropriate according to the optical characteristics of the light source 31 and the lens 32.

  Here, the light sources 31 are the same, and when the drive currents of the light sources 31 are the same, the amount of light for each of the illumination groups A to D varies depending on the number of the light sources 31. That is, the illumination group A (20) has the largest light amount, and the light amount decreases in the order of the illumination group C (7), illumination group B (5), and illumination group D (3).

  As shown in FIG. 5, the grouping of the illumination groups A to D is symmetrical between the first illumination unit 41 and the second illumination unit 42, and is arranged on the right side. The optical axis shift widths Sa to Sd of the second illumination unit 42 are opposite to each other in the same illumination groups A to D as compared with the first illumination unit 41 shown in FIGS. The optical axis shift width Sa of the illumination group A of the illumination unit 42 is −0.4 mm in the X-axis direction.

  In the present embodiment, the illumination group B (optical axis shift width Sb = 0.4 mm) having a relatively small optical axis shift width is arranged on the innermost side. This is because the light sources 31 of the respective illumination groups B provided are driven by a single drive circuit. By bringing the left and right illumination groups B close to each other, the wiring can be simplified and the cost can be reduced.

  FIG. 9 is a cross-sectional view showing the light emitting sections 33a to 33d (light source 31 and lens 32) for each of the illumination groups A to D, and FIG. 9A shows the illumination group A (optical axis shift width Sa = 0.2 mm). 9B shows the illumination group B (optical axis shift width Sb = 0.4 mm), FIG. 9C shows the illumination group C (optical axis shift width Sc = 0.9 mm), and FIG. ) Indicates the illumination group D (optical axis shift width Sd = 2.7 mm).

  The light source 31 and the lens 32 are arranged so that the optical axis C1 of the light source 31 and the center axis C2 of the lens 32 are relatively shifted, and the lens 32 is moved from the lens 32 according to the optical axis shift width (shift amount) Sa to Sd. The emission angle range from which the light is emitted changes, and the emission angle range differs for each of the illumination groups A to D. This emission angle range is in a direction opposite to the shift direction (X axis positive direction) and the opposite direction (X axis direction) with respect to the straight direction (Z axis direction, a direction parallel to the optical axis C1 of the light source 31 and the central axis C2 of the lens 32). The inclination of the emission angle range increases as the optical axis shift amounts Sa to Sd increase.

Specifically, as shown in FIG. 9A, in the illumination group A having the smallest optical axis shift width (first illumination means, optical axis shift width Sa = 0.2 mm), the straight traveling direction (Z-axis direction) ) Is emitted in an emission angle range (first emission angle range) close to. On the other hand, as shown in FIG. 9D, in the illumination group D ( fourth illumination means , optical axis shift width Sd = 2.7 mm) having the largest optical axis shift width, it is more horizontal than the emission angle range of the illumination group A. Light is emitted in an emission angle range ( fourth emission angle range ) that is greatly shifted outward in the direction (X-axis direction).

Further, as shown in FIG. 9B, in the illumination group B (third illumination means, optical axis shift width Sb = 0.4 mm) having a relatively small optical axis shift width, the emission angle range of the illumination group A is larger. Light is emitted in an emission angle range (third emission angle range) having a large inclination with respect to the straight traveling direction. In addition, as shown in FIG. 9C, in the illumination group C ( second illumination means , optical axis shift width Sc = 0.9 mm) having a relatively large optical axis shift width, the emission with a larger inclination with respect to the straight traveling direction is emitted. Light is emitted in an angle range ( second emission angle range ).

  Thus, the lens 32 condenses the light emitted from the light source 31 by arranging the light source 31 and the lens 32 in a state where the optical axis of the light source 31 and the center axis of the lens 32 are relatively shifted. Besides functioning as a condensing lens, it functions as an optical element that changes the emission angle range.

  In each of the illumination groups A to D, as the optical axis shift widths Sa to Sd increase, the inclination of the emission angle range with respect to the straight traveling direction increases, and according to the inclination of the emission angle range, each of the illumination groups A to D. The illumination area on the subject for each D is also shifted in the horizontal direction (X-axis direction). For this reason, the illumination group A with the smallest optical axis shift width illuminates the center of the imaging region of the subject, and the illumination group B with the next largest optical axis shift width illuminates the area shifted outward from the illumination group A. Next, the illumination group C with the largest optical axis shift width illuminates the area shifted outward from the illumination group B, and the illumination group D with the largest optical axis shift width shifts outside the illumination group C, that is, the outermost area. Illuminate the area.

  Here, the imaging area indicates the area of the subject imaged by the imaging unit 2, and the center of the imaging area is illuminated by the illumination group A. The illumination area of the illumination group A is the imaging area. There is no need to exactly match the center position of the region, and there may be a case where it is shifted from the center position of the imaging region. In addition, the necessary illumination area that needs to be illuminated with a predetermined illuminance or higher is set so as to include the imaging area. Usually, the central portion of the necessary illumination area and the central area of the imaging area generally coincide with each other. It is not necessary for the center position of the image pickup area and the center position of the image pickup area to exactly coincide with each other, and the center position of the necessary illumination area may deviate from the center position of the image pickup area.

  FIG. 10 is a front view showing a modification of the first lighting unit 41. FIG. 11 is a front view showing separately the light source substrate 45 and the lens array 46 constituting the first illumination unit 41 shown in FIG. 10 and 11, only the first lighting unit 41 arranged on the left side is shown, but the second lighting unit 42 arranged on the right side is different from the first lighting unit 41 in the left and right directions. Appears symmetrically.

  In the example shown in FIGS. 7 and 8, the lenses 32 are arranged at regular intervals, and the light source 31 is arranged so that the optical axis of the light source 31 is deviated from the central axis of the lens 32. However, in the modification shown in FIGS. 10 and 11, the light source 31 is arranged at a constant interval P, and the lens 32 is arranged so that the central axis of the lens 32 is deviated from the optical axis of the light source 31. It has become.

  That is, as shown in FIG. 11A, in the light source substrate 45, the light sources 31 are arranged at a constant interval P (for example, 12 mm), and in the lens array 46, as shown in FIG. The lens 32 is arranged so that the central axis of the lens 32 is displaced relative to the optical axis 31 with a predetermined optical axis shift width Sa to Sd.

  Here, as shown in FIGS. 7 and 8, in the configuration in which the light source 31 is shifted with respect to the lenses 32 arranged at regular intervals, the size of the light source 31 is generally smaller than the diameter of each lens 32. Therefore, the lenses 32 can be closely arranged in the lens array 46 to reduce the size, but as shown in FIGS. 10 and 11, the lenses 32 are arranged with respect to the light sources 31 arranged at regular intervals. In the configuration in which the lens 32 is shifted, the lens 32 is shifted outward, so that a gap is formed between the adjacent lenses 32. Therefore, the size reduction is limited, and the configuration shown in FIGS. Is advantageous.

  Next, output control of the light source 31 will be described. As shown in FIG. 3, the light source 31 is driven by the drive current applied from the drive circuit 34, and the output (light emission luminance) of the light source 31 is controlled according to this drive current value. Here, if the maximum drive current value (maximum rating) is used, the light source 31 can be turned on with the maximum output. If the drive current value is made smaller than the maximum drive current value, the output of the light source 31 is limited, and the drive current By increasing or decreasing the value, the output of the light source 31 can be limited at a required ratio.

  FIG. 12 is an explanatory diagram illustrating the output control status of the light source 31 in each of the short-distance, medium-distance, and long-distance illumination modes. FIG. 13 is an explanatory diagram illustrating the drive current values in the illumination groups A to D in a graph. FIG. 14 is an explanatory diagram illustrating the illuminance distribution in the short-distance, medium-distance, and long-distance illumination modes in a graph.

  In the present embodiment, as shown in FIG. 2, the output of the light source 31 for each of the three illumination modes selected when the light projection distance from the imaging device 1 to the subject is a short distance, a medium distance, and a long distance, respectively. At this time, as shown in FIGS. 12 and 13, output control of the light source 31 is performed in units of illumination groups according to the illumination mode.

  In the output control of the light source 31, in addition to turning on the light source 31 with the maximum drive current value (first drive current value) Max, no drive current is applied to the light source 31, that is, the light source 31 is turned off, Output limitation is performed to turn on the light source 31 with a drive current value smaller than the drive current value Max, in particular, an intermediate drive current value (second drive current value) Mid that is ½ of the maximum drive current value Max here. . The maximum drive current value Max and the intermediate drive current value Mid are, for example, 3.4 W and 1.7 W when converted into electric power.

  Here, based on FIG. 12, FIG. 13, the output control condition of the light source 31 is demonstrated for every four illumination groups AD.

  First, in the illumination group A (first illumination means, optical axis shift width Sa = 0.2 mm), output restriction is performed to turn off the light source 31 in the short-distance illumination mode, and intermediate output in the intermediate-distance illumination mode, that is, intermediate The output restriction for turning on the light source 31 with the drive current value Mid is performed. On the other hand, in the long-distance illumination mode, the output of the light source 31 is not limited, and the light source 31 is turned on with the maximum output, that is, the maximum drive current value Max.

  In the illumination group B (third illumination means, optical axis shift width Sb = 0.4 mm), output limitation of the light source 31 is performed in each of the short-distance and medium-distance illumination modes. Unlike A, both the short-distance and medium-distance illumination modes are subjected to intermediate output, that is, output limitation for turning on the light source 31 with an intermediate drive current value Mid. On the other hand, in the long-distance illumination mode, similarly to the illumination group A, the output of the light source 31 is not limited, and the light source 31 is turned on at the maximum output, that is, the maximum drive current value Max.

In the illumination group C ( second illumination means , optical axis shift width Sc = 0.9 mm), the light source 31 is turned on at the maximum output, that is, the maximum drive current value Max regardless of the illumination mode, and the output is not limited. .

In the illumination group D ( fourth illumination means , optical axis shift width Sd = 2.7 mm), the light source 31 is turned on at the maximum output, that is, the maximum drive current value Max in each of the short-distance and medium-distance illumination modes. 31 is not limited. On the other hand, in the long-distance illumination mode, output restriction for turning off the light source 31 is performed.

  In the present embodiment, the current value for driving the light source 31 is set in a plurality of stages as described above, and the driving power is selected according to the distance from the imaging device to the subject. It may be configured to be constant (for example, maximum rating) and to increase or decrease the PWM drive ON period according to the distance. If at least the ON period of the light source 31 is included in the exposure period of the image sensor 35 driven by the global shutter method, the same effect as that in the case of selecting the drive current can be obtained, and the brightness of the image to be captured is Be the same.

  Next, the output control status of the light source 31 will be described for each of the short-distance, medium-distance, and long-distance illumination modes.

  As shown in FIG. 9, in each of the illumination groups A to D, as the optical axis shift widths Sa to Sd are increased, the inclination of the emission angle range with respect to the straight traveling direction is increased. The illumination area on the subject of D is shifted in the horizontal direction (X-axis negative direction). For this reason, as shown in FIG. 14, in each of the illumination groups A to D, the illuminance peak on the subject is sequentially shifted outward.

  Here, as shown in FIG. 12A, in the short-distance illumination mode, output restriction is performed to turn off the light source 31 in the illumination group A having the smallest optical axis shift width, and the optical axis shift width is relatively small. In the illumination group B, output restriction for turning on the light source 31 with an intermediate driving current value Mid is performed, and in the illumination groups C and D having a large optical axis shift width, output restriction is not performed.

  By controlling in this way, in the short-distance illumination mode, as shown in FIG. 14A, the illumination group B illuminates the central area of the necessary illumination area, and the illumination group C is outside the illumination area of the illumination group B. The illumination group D illuminates the peripheral area of the necessary illumination area, and thereby the required illumination intensity can be satisfied over the entire necessary illumination area.

  In particular, it is possible to avoid an excessive illuminance at the center of the necessary illumination region by performing output restriction to turn off the light source 31 in the illumination group A having the smallest optical axis shift width. In addition, since the illumination group B having a relatively small optical axis shift width illuminates an area closer to the center of the illumination area, the illuminance at the center of the necessary illumination area is reduced by reducing the drive current of the illumination group B. It can avoid becoming excessive.

  Further, as shown in FIG. 12B, in the middle-distance illumination mode, output restriction is performed to turn on the light source 31 with an intermediate drive current value Mid in the illumination groups A and B having a small optical axis shift width. In the illumination groups C and D having a large axis shift width, output restriction is not performed.

  By controlling in this way, in the middle-distance illumination mode, as shown in FIG. 14B, the illumination group A illuminates the central area of the necessary illumination area, and the illumination group B is outside the illumination area of the illumination group A. The illumination group C illuminates the area where the illumination group C deviates from the illumination area of the illumination group B, and the illumination group D illuminates the peripheral area of the necessary illumination area. The required illuminance can be satisfied across.

  In particular, since the illumination groups A and B having a small optical axis shift width illuminate the central portion of the necessary illumination region and the vicinity thereof, the drive current of the illumination groups A and B is reduced, thereby reducing the required illumination region. It is possible to avoid excessive illuminance at the center.

  Further, as shown in FIG. 12C, in the long-distance illumination mode, output restriction is performed to turn off the light source 31 in the illumination group D having the largest optical axis shift width, and output is performed in the other illumination groups A to C. There are no restrictions.

  By controlling in this way, as shown in FIG. 14C, the illumination group A illuminates the central area of the necessary illumination area, and the illumination group B illuminates an area shifted outside the illumination area of the illumination group A. Then, the illumination group C illuminates the peripheral area of the illumination area, so that the necessary illuminance can be satisfied over the entire necessary illumination area.

  In particular, by performing output restriction to turn off the light source 31 in the illumination group D having the largest optical axis shift width, it is possible to avoid useless illumination in a region outside the necessary illumination region. Further, by increasing the drive current in all the illumination groups A to C to be lit, the necessary illuminance can be ensured over the entire required illumination area at a long distance.

As described above, in this embodiment, when the distance to the subject is short (short-distance and medium-distance illumination modes), output restriction is performed on the illumination group A (first illumination unit), and the subject When the distance is long (far-distance illumination mode), the output is limited for the illumination group D ( fourth illumination means ), so even if the distance to the subject is greatly different, the necessary illumination corresponding to the imaging region It is possible to illuminate the area with an appropriate illuminance and suppress unnecessary illumination outside the necessary illumination area.

  In other words, when the distance to the subject is short, output restriction is performed on the illumination group A, so that overexposure that occurs in the captured image due to excessive illuminance at the center of the necessary illumination area is suppressed. Can do. On the other hand, when the distance to the subject is long, output restriction is performed on the lighting group D, so that light is prevented from diffusing in an unnecessary direction outside the necessary illumination area and power consumption is kept low. Can do.

  By the way, when installing the imaging device 1 for the purpose of crime prevention or monitoring, it is necessary to prevent the person existing in the imaging area from being aware of being monitored by the imaging device 1, For this reason, in the present embodiment, an LED that emits infrared light to the light source 31 is used. Further, the light source 31 is preferably one that emits near-infrared light with excellent transparency in order to avoid the influence of rainfall. However, in an LED that emits near-infrared light, a small amount of light having a wavelength that falls within the visible range is emitted, and in the case of a high output, the illumination light appears slightly red from the person in the illumination region, and is hidden. Sexuality decreases.

  With respect to such a problem, in this embodiment, confidentiality can be ensured by performing output control of the light source 31 as described above. Hereinafter, the significance of this embodiment regarding confidentiality will be described.

  FIG. 15 is a plan view schematically showing the conventional configuration and the illumination state according to the present embodiment. FIG. 15A shows the case of the conventional configuration, and FIGS. 15B-1 and 15B-2 show the case of the conventional configuration. The cases according to the present embodiment are respectively shown.

  Here, the imaging devices 1 and 51 image roads and building sites for the purpose of crime prevention, etc., regardless of the distance from the imaging devices 1 and 51 to the subject, the horizontal width of the imaging region is constant, Therefore, the width of the necessary illumination area is also constant.

  As shown in FIG. 15A, in the imaging device 51 according to the conventional configuration, since the illumination mode is not switched according to the distance, red is widely used so that the actual illumination area includes the necessary illumination area at a short distance. It is necessary to irradiate infrared light with high output so as to irradiate external light and satisfy the required illuminance at a long distance. For this reason, the illumination light appears clearly red from the person in the illumination area at a short distance, and the illumination light can be seen from a person outside the necessary illumination area at a long distance. Sex cannot be secured.

  On the other hand, in the imaging device 1 according to the present embodiment, as shown in FIGS. 15B-1 and 15B-2, the illumination mode is switched according to the distance. Thereby, in the short distance illumination mode shown in FIG. 15 (B-1), it becomes difficult to see illumination light from a person in the illumination area by keeping the output low so as to satisfy the required illuminance at a short distance position. Confidentiality can be ensured. Further, in the long-distance illumination mode shown in FIG. 15B-2, the illumination area is narrowly limited so that the actual illumination area satisfies the necessary illumination area at a long-distance position. Therefore, the long-distance illumination mode is outside the necessary illumination area. Illumination light is not visible to a person, and confidentiality can be ensured.

(Second Embodiment)
In the first embodiment, the user manually switches the illumination mode according to the projection distance from the imaging device 1 to the subject. However, in the second embodiment described below, the projection distance is measured. Thus, the illumination mode is automatically set based on the measurement distance. The points not particularly mentioned are the same as in the above embodiment.

  FIG. 16 is a block configuration diagram of an imaging apparatus 61 according to the second embodiment. FIG. 17 is a front view of the imaging device 61.

  As illustrated in FIG. 16, the imaging device 61 includes a distance measuring unit 62 that measures the light projection distance from the imaging device 61 to the subject. The distance measuring unit 62 measures a projection distance based on a so-called TOF (Time of Flight) method, and includes an infrared sensor 63, an amplifier 64, a comparator 65, a D / A converter 66, A high-speed counter 67 and a clock generator 68 are provided.

  The infrared sensor 63 is composed of a photodiode, for example. As shown in FIG. 17, the infrared sensor 63 is provided on the front side of the imaging device 61 side by side with the imaging unit 2 and the illumination unit 3.

  FIG. 18 is an explanatory diagram showing the status of distance measurement by the imaging device 61. FIG. 18A shows the status viewed from the back side of the imaging device 1, and FIG. 18B shows the status from the side of the imaging device 1. Each situation is shown.

  The distance measurement process for measuring the light projection distance from the imaging device 61 to the subject only needs to be performed once, for example, when the imaging device 61 is installed. The accuracy can be improved by arranging and measuring the subject. In the example of FIG. 18, the reflector 71 is disposed as a dummy subject at the center position of the illumination area on the road surface that is the subject. Since this reflecting plate 71 is placed at an arbitrary position in a relatively wide range such as 5 m to 30 m from the imaging device, for example, in order to make reflection characteristics as constant as possible, it is made of a retroreflecting material using, for example, glass beads. It is desirable that

  FIG. 19 is a flowchart illustrating a procedure of processing performed by the imaging device 61. Here, the time from when the light from the imaging device 1 is irradiated until the light reflected by the reflecting plate 71 enters the imaging device 1 is calculated, and the distance from the imaging device 1 to the reflecting plate 71 is calculated. The illumination mode is selected based on this distance.

  Specifically, first, a threshold level signal is output from the control unit 27 to the comparator 65 in advance to set a threshold level for detecting reflected light. And the infrared light for a measurement is radiate | emitted from the illumination part 3 (ST101). In the measurement, all the light sources 31 may be turned on with the maximum light amount in order to correspond to any of the short distance to long distance illumination modes. Here, the control unit 27 resets the count value of the high-speed counter 67 and the light source 31 of any one of the four illumination groups A to D, for example, the light source of the illumination group A (optical axis shift width = 0.2 mm). 31 is driven to output an optical pulse having a predetermined time width. Here, the reset high-speed counter 67 counts up based on a 1 GHz (one period is 1 ns) clock signal output from the clock generator 68.

  The infrared light (light pulse) emitted from the illumination unit 3 is reflected by the reflecting plate 71 and enters the infrared sensor 63, and the distance measuring unit 62 detects that the reflected infrared light is incident ( ST102). At this time, the output of the infrared sensor 63 is amplified by the amplifier 64 after the offset component is removed by an operational amplifier (not shown) to generate an analog level signal. The analog level signal is compared with the threshold level by the comparator 65, and when the analog level signal exceeds the threshold level, the comparator 65 outputs a detection signal to the high-speed counter 67 and the control unit 27. The high-speed counter 67 that has received the detection signal captures the count value at that time in a register (not shown). On the other hand, the detection signal input to the control unit 27 functions as an interrupt signal (IRQ) for the CPU, and based on the interrupt signal, the CPU accesses the register of the high-speed counter and acquires the count value.

Next, the distance to the reflector 71 is calculated based on the count value in the control unit 27 (ST103). At this time, the CPU of the control unit 27 calculates the distance based on the speed of light C (300 × 10 ⁶ [m / s]) and the count value N as follows.
300 × 10 ⁶ [m / s] × 10 ⁻⁹ × N / 2 = 0.15 × N [m]
Here, the count frequency is 1 G (1 × 10 ⁹ ) [Hz] (period = 1 × 10 ⁹ [s] = 1 [ns]). The reason why the count value N is divided by 2 is to make the measured distance one-way because the measured distance is the round-trip. Thus, if a 1 G [Hz] clock is used, the distance to the assumed subject position can be measured with an accuracy of 15 cm.

  Next, the control unit 27 determines the illumination mode based on the measured distance (ST104). Here, the illumination mode is determined by comparing the measured distance with a predetermined threshold. In the present embodiment, there are three illumination modes, short distance, medium distance, and long distance. Therefore, the first threshold value (15 m) for distinguishing between the medium distance and the long distance is distinguished from the short distance and the medium distance. The illumination mode is determined by comparison with the second threshold value (10 m).

  Next, processing for setting the driving conditions (lighting on / off and driving current value) of the light source 31 based on the determined illumination mode is performed (ST105 to ST107). The driving condition of the light source 31 is stored in advance in the ROM of the control unit 27 for each illumination mode, and processing for setting the driving condition of the light source 31 is performed with reference to this.

  In this embodiment, an example using the TOF method has been described. However, an ultrasonic wave (for example, about 20 to 30 KHz) may be used instead of light, and a stereo method or other known distance measurement methods may be used. You may make it use. In the present embodiment, the distance to the reflecting plate 71 is calculated. However, the illumination mode may be determined directly from the count value N (reflection time), and further, directly from the count value N. The driving condition of the light source 31 may be obtained.

  Further, as shown in FIG. 18B, in the description so far (see FIG. 2), the projection distance is described as the horizontal distance D, but the distance (reflection path length) D ′ obtained by the TOF method is Strictly different from the distance D in the horizontal direction, the relationship between the two is defined by the installation height H of the imaging device 61, but the distance D ′ affects the actual illumination state. For this reason, when the distance D ′ is actually measured by the TOF method as in the second embodiment, the illumination mode is determined based on the threshold relating to the distance D ′, and the user selects the illumination mode as in the first embodiment. When selecting and setting, the illumination mode may be determined in consideration of the installation height H of the imaging apparatus 1.

(Third embodiment)
In the second embodiment, when the illumination mode is automatically set based on the measurement distance, the light projection distance from the imaging device 61 to the subject is measured by the TOF method. In the embodiment, the illumination area on the subject is imaged, and the projection distance is measured based on the lateral width of the illumination area. For this reason, in this embodiment, as shown in FIG. 16, the distance measuring unit 62 that measures the projection distance based on the TOF method is not provided. The points not particularly mentioned are the same as in the above embodiment.

  FIG. 20 is an explanatory diagram showing the status of distance measurement according to the third embodiment. When the subject (road surface of the road) is irradiated with light from the imaging device 81, a brightly illuminated illumination area appears on the subject. The horizontal width of the illumination region changes according to the light projection distance from the imaging device 81. Here, by adjusting the imaging magnification of the imaging device 1 (corresponding number of pixels when an article having a predetermined reference length is imaged assuming a specific separation distance), the width of the illumination area is adjusted. Based on this, it is possible to acquire the projection distance, and the width of the illumination area is obtained by imaging the illumination area on the subject and subjecting the obtained captured image to image processing by the control unit 27.

  Specifically, first, the light source 31 of the illumination unit 3 is turned on. The four light groups A to D have different light diffusion conditions. For example, the light source 31 of the light group A having the narrowest diffusion width is turned on. Next, the illumination area that appears on the subject is imaged by the imaging unit 2. Then, the control unit 27 obtains an illuminance distribution pattern on the subject by performing image processing on an image obtained by imaging by the imaging unit 2, and extracts an effective illumination region based on the illuminance distribution pattern. Thus, the width of the effective illumination area is obtained. Next, the projection distance is obtained from the calculated lateral width of the effective illumination area. At this time, the correlation between the projection distance and the horizontal width of the illumination area is stored in advance in a ROM as a table, for example, and the projection distance is obtained from the horizontal width of the effective illumination area with reference to this.

(Fourth embodiment)
In the first to third embodiments, the driving conditions (lighting) of the light source 31 set in advance for each illumination mode are classified into the short-distance, medium-distance, and long-distance illumination modes according to the projection distance. In the fourth embodiment described below, the driving conditions of the light source 31 are set in advance according to the light projection distance, and the light output is controlled according to the light projection distance. The output control of the light source 31 is performed under the driving condition selected based on the light distance. The points not particularly mentioned are the same as in the above embodiment.

  FIG. 21 is an explanatory diagram showing the current control status of the light source 31 according to the fourth embodiment in a graph. FIG. 21 also shows the state of current control according to the first embodiment shown in FIG.

  In the fourth embodiment, a drive current value corresponding to the light projection distance is set in advance for each illumination group, and the drive current value is changed according to the measured light projection distance. Since the irradiance (power density) is inversely proportional to the square of the distance, the illuminance distribution can be made more appropriate by changing the drive current value corresponding to the distance by a quadratic function (parabola).

  In the illumination group A (optical axis shift width Sa = 0.2 mm), in the case of a short distance, output limitation by turning off is performed as in the first embodiment. On the other hand, in the case of a medium distance and a long distance, the drive current value is controlled to increase in a quadratic function as the light projection distance increases. In the illumination group B (optical axis shift width Sb = 0.4 mm), in the case of a short distance, as in the first embodiment, a constant output restriction is performed with an intermediate drive current value Mid. On the other hand, in the case of a medium distance and a long distance, the drive current value is controlled to increase in a quadratic function as the light projection distance increases. In the illumination group C (optical axis shift width Sc = 0.9 mm), similarly to the first embodiment, the light source 31 is turned on with the maximum drive current regardless of the light projection distance, and the output is not limited. In the illumination group D (optical axis shift width Sd = 2.7 mm), the case is not divided according to the light projection distance, and the drive current value is reduced in a quadratic function as the light projection distance increases. To be controlled.

Thus, in the present embodiment, as in the first embodiment, when the distance to the subject is short (short-distance and medium-distance illumination modes), the output is made to the illumination group A (first illumination means). When the restriction is performed and the distance to the subject is long (long-distance illumination mode), the output restriction is performed on the illumination group D ( fourth illumination means ), so the distance to the subject is greatly different. Even in this case, it is possible to illuminate the necessary illumination area corresponding to the imaging area with an appropriate illuminance and suppress unnecessary illumination outside the necessary illumination area.

  In this embodiment, when the distance to the subject is short (short-distance and medium-distance illumination modes), output is limited for the illumination group A, and output is also limited for the illumination group D. However, since the output of the lighting group D is limited at a rate smaller than that of the lighting group A, the illuminance within the necessary lighting area can be ensured. Also, when the distance to the subject is long (long-distance illumination mode), output restriction is performed on the illumination group A in addition to output restriction on the illumination group D. On the other hand, since the output is limited at a rate smaller than that of the illumination group D, the illuminance within the necessary illumination area can be ensured.

(Fifth embodiment)
In the first to fourth embodiments, the light projection distance is measured and the output control of the light source 31 is performed based on the light projection distance. However, in the fifth embodiment described below, on the subject. The actual illuminance distribution of the light source 31 is measured, and the driving conditions (lighting on / off and driving current value) of the light source 31 are adjusted so that an ideal illuminance distribution is obtained based on the actual illuminance distribution. The points not particularly mentioned are the same as in the above embodiment.

  FIG. 22 is an explanatory diagram showing a situation of illuminance distribution measurement according to the fifth embodiment. Here, a reference sheet 92 having a predetermined reflectance is laid on the road surface so that the measurement result does not depend on the road surface condition (dry, wet, etc.). The reference sheet 92 is preferably made of a thin resin, so that it is not necessary to prevent the vehicle from passing on the reference sheet 92. The reference sheet 81 has a size sufficiently larger than the imaging area.

  In the illuminance distribution measurement, first, the light source 31 of the illumination unit 3 is turned on in the imaging device 91. At this time, all the light sources 31 of the four illumination groups A to D are turned on with the maximum drive current value. Next, the reference sheet 92 is imaged by the imaging unit 2. And in the control part 27, the illuminance distribution pattern on the reference | standard sheet | seat 81 is acquired by performing image processing with respect to the image obtained by the imaging by the imaging part 2, and based on this illuminance distribution pattern, an effective illumination area is determined. Extract. At this time, the reference sheet 92 may be imaged for a relatively long period of time, and the illuminance distribution may be obtained based on an image from which the so-called foreground is removed. Specifically, the imaging period is set to about 30 to 60 seconds, for example, and an average value is obtained for each pixel of the frame image captured during this period. As a result, the influence of the foreground such as a person or a vehicle passing through the monitoring area can be reduced. Also, if the influence of averaging (remaining foreground components) becomes a problem even in this way, the influence of disturbance can be further reduced by performing the median filter processing.

  Next, the illuminance distribution pattern in the effective illumination area is compared with the target pattern prepared in advance. In this comparison, both sizes are normalized to be the same, and divided into blocks each consisting of a plurality of pixels to calculate a representative value (average value). The sum of squares of these differences is used as an evaluation function. And the drive condition of the light source 31 is set so that this evaluation function may become the minimum. In the case where the light amount control is performed in minute steps as shown in the fourth embodiment, a known algorithm such as a genetic algorithm can be used to obtain a driving condition that minimizes the evaluation function. .

  Here, the driving condition of the light source 31 may be set for each of the four illumination groups A to D, as in the above-described embodiment, but the driving condition may be set for each light source 31.

  In each of the above embodiments, the light source 31 that emits infrared light is used. However, the present invention is not limited to this, and a light source that emits visible light can also be used.

  In each of the above embodiments, as shown in FIG. 5, the illumination unit 3 is configured by the two illumination units 41 and 42, but the present invention is not limited to this, for example, The illumination unit may be composed of a single illumination unit. In this case, only one light source substrate or lens array is required.

  Further, in each of the above-described embodiments, as shown in FIG. 5 and the like, a lens that collects light emitted from the light source 31 is used to change the emission angle range in the illumination groups A to D. However, the optical axis of the light source and the central axis of the lens are arranged so as to be relatively deviated from each other. However, the present invention is not limited to this, and for example, an optical element other than a lens (for example, a prism) May be used to change the emission angle range.

  In each of the above-described embodiments, as shown in FIG. 5 and the like, the plurality of light emitting units 33a to 33d (light source 31 and lens 32) are grouped into four illumination groups A to D according to the light distribution characteristics. However, the present invention is not limited to this, and the light emitting units can be grouped into two, three, or four or more illumination groups. Further, the arrangement position of the light emitting units constituting each illumination group is not limited to the illustrated configuration.

  Further, in each of the embodiments described above, as shown in FIG. 5 and the like, the optical axis of the light source 31 and the central axis of the lens 32 are relatively shifted in all of the four illumination groups A to D. The present invention is not limited to this. For example, the illumination group A illuminates the central area of the subject. Therefore, a configuration in which the optical axis of the light source 31 and the central axis of the lens 32 are not relatively shifted is also possible. Is possible.

  Further, in each of the embodiments described above (except for the fourth embodiment), as shown in FIG. 13, when the output of the light source 31 is limited, the first drive current value smaller than the maximum drive current value (first drive current) is used. However, the present invention is not limited to this, and the light source 31 has a plurality of drive current values smaller than the maximum drive current value. The output restriction may be performed in multiple stages.

  In each of the embodiments described above (except for the fourth embodiment), the second drive current value applied to the light source 31 when the output of the light source 31 is limited is the maximum drive current value. Although the intermediate drive current value Mid that is ½ of the drive current value Max is set, the present invention is not limited to this, and the second drive current value is set according to the light emission characteristics, the number of arrangements, and the like of the light source 31. May be set appropriately.

  Further, in each of the above-described embodiments, the light source 31 that can change the output (light emission luminance) by increasing or decreasing the drive current value is employed, and in addition to lighting at the maximum output, lighting at the intermediate output The lighting state is optimized by turning on or at an arbitrary output lower than the maximum output. In addition to the output control based on the driving current value, the light source 31 to be turned on in the lighting group is used. The output control can be performed by changing the number, and the output control based on the number of lighting light sources and the output control based on the drive current value can be combined.

  In each of the above embodiments, the case where the imaging device is installed at a predetermined height from the ground has been described. However, the installation location can be changed as appropriate. It can be installed not only on a stationary body such as the ground but also on a moving body. The moving body may be mounted inside or outside the vehicle. Further, the image pickup apparatus may be portable and used by a person.

  The imaging device and the control method thereof according to the present invention can illuminate the necessary illumination area corresponding to the imaging area with appropriate illuminance and suppress unnecessary illumination outside the necessary illumination area even when the distance to the subject is greatly different. It is useful as an imaging apparatus that captures an image while illuminating a subject, particularly an imaging apparatus that captures an image of a road or a building site for the purpose of crime prevention or surveillance, and a control method thereof.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Imaging part 3 Illumination part 21 Drive part 27 Control part (output control means)
31 Light source 32 Lens 33a Light emitting part of illumination group A (first illumination means)
33b Light emitting unit of illumination group B (third illumination means)
33c Light-emitting part of illumination group C ( second illumination means )
33d Light emitting part of illumination group D ( fourth illumination means )
34 Drive circuits 41 and 42 Illumination unit 45 Light source substrate 46 Lens array C1 Optical axis C2 of light source Center axis Sa to Sd of lens Optical axis shift amount (deviation amount)

Claims (15)

A monitoring imaging apparatus that images a subject while illuminating a necessary illumination area that is set to include the imaging area,
An illumination unit including at least a first illumination unit that emits infrared light, and a second illumination unit that is disposed across the first illumination unit and emits infrared light;
Output control means for controlling the output of the illumination unit,
The necessary illumination area consists of a rectangular area having a certain lateral width regardless of the distance from the monitoring imaging device,
The first illumination means is set to a light distribution characteristic that emits light in a first emission angle range so as to illuminate a central portion of the necessary illumination area ,
The second illumination means emits light in a second emission angle range shifted from the first emission angle range so as to illuminate a region shifted outward from the center of the necessary illumination region. Set to
The first illuminating means and the second illuminating means are further configured such that, in the necessary illumination area, a peak of each illuminance distribution is set to a width of the necessary illumination area including the rectangular area regardless of a distance from the monitoring imaging device. Have in,
The output control means includes
If the distance to the subject is short, it has rows output limit including off to the first lighting unit, when the distance to the subject is long, the output limitation for the first lighting unit It performs termination or full lighting, the respect to the second illumination means, monitoring imaging device and performing full lighting regardless of the distance from the monitoring imaging device in the required illumination area. The illumination unit further includes third illumination means for emitting infrared light,
The first illumination means is disposed across the third illumination means,
The third illuminating means illuminates a region shifted outward from the first illuminating means,
The second illuminating means illuminates a region shifted outward from the third illuminating means,
When the distance to the subject is short, the output control means turns on the first illumination means with an output equal to or less than the third illumination means, and when the distance to the subject is long, the output control means 1 lighting means is lit in the same manner as the third lighting means ,
Said third illumination means further characterized in that perforated the required illumination regardless of the distance from the monitoring imaging device in the region, the horizontal width of the required illumination area comprising the peak of each intensity distribution from said rectangular region The monitoring imaging apparatus according to claim 1. The illumination unit further includes third illumination means for emitting infrared light,
The first illumination means is disposed across the third illumination means,
The third illuminating means illuminates a region shifted outward from the first illuminating means,
The second illuminating means illuminates a region shifted outward from the third illuminating means,
When the distance to the subject is short, the output control means turns on the third illumination means to limit the output than the second illumination means, and when the distance to the subject is long, The third lighting means is turned on in the same manner as the second lighting means ,
Said third illumination means is further regardless of the distance from the monitoring imaging device in the required illumination area, and characterized in that have a peak of the illuminance distribution in the width of the required illumination area formed of the rectangular region The monitoring imaging device according to claim 1 or 2. The output control means divides the distance to the subject into three cases of a short distance, a medium distance, and a long distance according to a first distance and a second distance shorter than the first distance, and outputs the output of the illumination unit. The monitoring imaging device according to claim 1, wherein the monitoring imaging device is controlled. The output control means turns off the first illumination means and turns on the second illumination means when the distance is short, and turns on the second illumination means when the distance is medium. At the same time, the first illuminating means is turned on with an output limited to that of the second illuminating means, and both the first illuminating means and the second illuminating means are lit when the distance is long. The monitoring imaging apparatus according to claim 4. The illumination unit further includes third illumination means for emitting infrared light,
The output control means turns on the third illuminating means when the short distance and the medium distance are more limited than the second illuminating means, and turns on the third illuminating means when the distance is long. The monitoring image pickup apparatus according to claim 5, wherein the third illumination unit is lit in the same manner as the second illumination unit. 7. The imaging for monitoring according to claim 6, wherein the output control means turns on the first illumination means in the same manner as the third illumination means at the intermediate distance and the long distance. apparatus. Said third illumination means of claim 2, wherein the emitting light at a third emitting angle range between the first emission angle range and the second emitting angle range, according to claim 3 The monitoring imaging device according to claim 6 . The illumination unit further includes fourth illumination means for emitting infrared light,
The fourth illuminating means is disposed across at least a part of the second illuminating means, and illuminates a region shifted outward from the second illuminating means,
The output control means turns on the fourth illumination means in the same manner as the second illumination means when the distance to the subject is short, and the fourth control means when the distance to the subject is long. There line output restriction containing off the illumination means,
The said 4th illumination means has further the peak of the illumination intensity distribution in the horizontal width of the required illumination area | region which consists of the said rectangular area | region at least the near side of the said required illumination area, The Claim 2 or Claim characterized by the above-mentioned. 4. The imaging device for monitoring according to 3. The illumination unit further includes fourth illumination means for emitting infrared light,
The fourth illuminating means is disposed across at least a part of the second illuminating means, and illuminates a region shifted outward from the second illuminating means,
The output control means turns on the fourth illumination means in the same manner as the second illumination means in the case of the short distance and the intermediate distance, and the fourth illumination in the case of the long distance. There line output restriction containing off against means,
5. The fourth illumination unit according to claim 4, wherein the fourth illumination unit further has a peak of the illuminance distribution at least in front of the required illumination area within a lateral width of the required illumination area including the rectangular area. The monitoring imaging apparatus according to any one of 8. The fourth illumination means emits light in a fourth emission angle range that is larger than any of the first emission angle range to the third emission angle range. The monitoring imaging device according to 10. Each of the illumination means has a light source and a lens that collects light emitted from the light source,
In the first illumination means, the light source and the lens are arranged in a state where the optical axis of the light source and the central axis of the lens are relatively shifted with a first shift amount,
In the second illuminating means, the light source and the lens are arranged in a state where the optical axis of the light source and the central axis of the lens are relatively shifted with a second shift amount larger than the first shift amount. The monitoring imaging apparatus according to claim 1, wherein the monitoring imaging apparatus is provided. A plurality of the lenses are arranged at regular intervals,
The monitoring imaging apparatus according to claim 12, wherein a plurality of the light sources are arranged in a state where an optical axis is deviated from a central axis of the lens. A distance measuring unit for measuring a distance to the subject;
The monitoring imaging apparatus according to claim 1, wherein the output control unit controls the output of the illumination unit based on a distance acquired by the distance measuring unit. An illumination unit including at least a first illumination unit that emits infrared light, and a second illumination unit that is disposed with the first illumination unit interposed therebetween and emits infrared light;
The first illuminating means is configured to include the imaging region , and the first emission unit illuminates a central portion of the necessary illumination region including a rectangular region having a constant lateral width regardless of the distance from the monitoring imaging device. It is set to the light distribution characteristic that emits light in the angle range,
The second illumination means emits light in a second emission angle range shifted from the first emission angle range so as to illuminate a region shifted outward from the center of the necessary illumination region. A monitoring imaging device control method set to
Image the subject while illuminating the necessary illumination area,
The first illuminating means and the second illuminating means further have a peak of each illuminance distribution within the width of the required illumination area consisting of the rectangular area, regardless of the distance from the monitoring imaging device,
If the distance to the subject is short, it has rows output limit including off to the first lighting unit, when the distance to the subject is long, the output limitation for the first lighting unit Control of the imaging device for monitoring characterized in that the lighting device is released or fully lit, and the second illumination means is fully lit regardless of the distance from the monitoring imaging device in the necessary illumination area. Method.