JP2011244357A - Imaging apparatus, relay optical system, and measurement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus etc. that can detect at high speed and with high accuracy, and more surely a weak fluorescence image formed by a image multiplication device.SOLUTION: Because a relay optical system 13 arranged between an image multiplication device 11 and a signal converter 12 is telecentric at an output plane 11b side, i.e., an object side of the image multiplication device 11, in combination with a light flux emitted from the output plane 11b being light distribution which indicates central concentricity, the fluorescence image at the output plane 11b can be reformed on an image sensing surface 12a in a highly precise state and a bright state where aberration, such as distortion, is reduced, and the weak fluorescence image formed by the image multiplication device 11 can be detected with high accuracy and surely.

Description

  The present invention relates to an imaging device that can detect an event that occurs irregularly in the natural world at high speed and record the event, a relay optical system that is used in the imaging device, and a measurement system that uses the imaging device.

  An event to be imaged is converted into a fluorescent image, and the fluorescence image is distributed to two fluorescent images by the light distribution unit, and the shutter signal for the imaging unit that captures the other fluorescent image is used. Thus, an inventor of the present application has proposed an optical distribution type imaging device capable of imaging an event to be imaged with a high S / N (Patent Document 1).

JP 2004-207980 A

  The light distribution type imaging device as described above is a technology that enables imaging of irregular events such as the arrival of weak electromagnetic waves, the generation of weak light, etc. in nanosecond order. Further improvement of the detection limit regarding etc. is desired.

  As a result of examining the factors that have a large influence on the detection limit as described above, the present inventor has found that the fluorescent screen of the image intensifier tube is more reliably detected in order to detect a weak fluorescent image with a high S / N ratio. Focusing on the need to accurately transmit the formed fluorescent image to the solid-state image sensor with little loss, a relay that can form the fluorescence image of the image intensifier tube on the imaging surface of the solid-state image sensor with high accuracy and high efficiency The optical system was examined.

  Note that there are various projection lenses for projecting an image on a liquid crystal panel, for example (Japanese Patent Laid-Open Nos. 2001-116990, 2009-186790, and 2009-258395). All the lenses are premised on a magnified projection at a considerably high magnification, and cannot be applied as they are to a relay optical system premised on image formation close to the same magnification. In addition, the projection lens as described above generally suppresses aberration uniformly in the entire visible light range, and forms a fluorescent image having a specific spectral luminance distribution on the imaging surface of the solid-state imaging device with high accuracy. The situation is not considered.

  An object of the present invention is to provide an imaging apparatus that can detect a weak fluorescent image with high speed and high accuracy.

  Another object of the present invention is to provide a relay optical system that is used in the imaging apparatus as described above and can form a fluorescent image of the image intensifier on an imaging surface of a solid-state imaging device with high accuracy and high efficiency. It is.

  Another object of the present invention is to provide a measurement system that can reliably measure irregularly occurring events and the like at high speed with high accuracy using the above-described imaging apparatus.

  In order to solve the above problems, an imaging device according to the present invention includes an image intensifier that converts a weak event into a fluorescent image, and a signal that converts the fluorescent image output from the image intensifier into an electrical image signal. A conversion device and a relay optical system that projects a fluorescent image on the output surface of the image intensifier on the imaging surface of the signal conversion device and is telecentric on the output surface side.

  According to the imaging apparatus, since the relay optical system is telecentric on the output surface side, that is, on the object side, the fluorescence image on the output surface is coupled with the light distribution emitted from the output surface having a light distribution showing central concentration. Can be re-imaged on the imaging surface in a highly accurate and bright state with reduced aberrations such as distortion, and the weak fluorescent image formed by the image intensifier can be detected accurately and reliably. Can do.

  In a specific aspect or aspect of the present invention, in the imaging device, the relay optical system projects the output surface of the image intensifier on the imaging surface of the signal converter at approximately the same magnification. In this case, the fluorescent image on the output surface can be efficiently formed on the imaging surface of the signal conversion device with little distortion.

  In another aspect of the present invention, the relay optical system includes a first lens group and a second lens group in order from the output surface, and an imaging magnification is obtained by adjusting a distance between the first lens group and the second lens group. Can be corrected. In this case, the fluorescent image on the output surface of the image intensifier can be formed on the imaging surface at an appropriate magnification, and high-accuracy imaging is possible.

  In still another aspect of the present invention, the relay optical system is provided to face the output surface of the image intensifier, and the fluorescent image output from the image intensifier is converted into a first fluorescent image and a second fluorescent image. And having a distributor for guiding the first fluorescent image to the optical path toward the signal converter, and setting the timing for defining the imaging timing for operating the signal converter from the second fluorescent image separated by the distributor And a device. In this case, when an image (event) to be imaged is detected by the timing setting device, the signal conversion device can be operated, and imaging of the event can be performed in synchronization with or predicting an irregularly generated event. It is possible to record high-speed events accurately.

  In still another aspect of the present invention, the timing setting device includes a photomultiplier that individually detects a second fluorescent image from a segmented region that constitutes an output surface of the image multiplier. In this case, it is possible to specify in which divided region of the divided regions constituting the output surface the fluorescent image is formed, and the signal conversion device can be operated appropriately.

  In yet another aspect of the present invention, the timing setting device determines the local region of the signal conversion device corresponding to the segmented region of the photomultiplier based on the detection signal corresponding to the segmented region output from the photomultiplier. A drive signal for selectively operating is output. In this case, since the local region of the signal conversion device can be selectively operated based on the drive signal, the signal conversion device corresponding to the appearing region where the fluorescent image is formed on the output surface of the image intensifier. Imaging in the local region of the image sensor can be made with high sensitivity and high definition adapted to the state of the fluorescent image in the appearing region of the output surface.

  In still another aspect of the present invention, an image intensifier includes a photoelectric conversion unit disposed in an input stage, a proximity multiplication element disposed in a subsequent stage of the photoelectric conversion unit, and a stage subsequent to the proximity multiplication element. And an output surface to be arranged. In this case, it is possible to measure a high-intensity fluorescent image obtained by multiplying the detection output of the photoelectric conversion unit with a proximity multiplication element.

  In still another aspect of the present invention, the signal conversion device includes a solid-state image sensor that is one of a CMOS image sensor and a CCD image sensor, and is based on a timing signal output from the timing setting device. To work. In this case, the image intensifier and the solid-state imaging device can be operated in synchronization at high speed via the timing setting device.

  In order to solve the above problems, a relay optical system according to the present invention is a relay optical system incorporated in an imaging apparatus having a signal conversion apparatus that converts an image formed on the output surface of the detection apparatus into an electrical image signal. Thus, the image formed on the output surface of the detection device is projected on the imaging surface of the signal conversion device at approximately the same magnification, and is telecentric on the target image side.

  According to the relay optical system, the image formed on the output surface of the detection device, that is, the object side is projected onto the imaging surface of the signal conversion device at substantially the same magnification, and is telecentric on the output surface side, so that it is formed on the output surface. The image can be re-imaged efficiently in a highly accurate and bright state with reduced distortion and other aberrations on the imaging surface, and even if the image formed on the output surface is weak, it is highly accurate. Can be reliably detected.

  In a specific aspect of the present invention, the detection device is an image intensifier that converts a weak event into a fluorescent image on the output surface. In this case, the weak fluorescent image formed by the image intensifier can be reliably detected with high accuracy.

  In another aspect of the present invention, in the relay optical system, a fluorescent image that is provided facing the output surface of the image intensifier and is output from the image intensifier is a first fluorescent image and a second fluorescent image. And a distributor that guides the first fluorescent image to the optical path toward the signal conversion device and guides the second fluorescent image to the optical path toward the timing setting device that defines the imaging timing for operating the signal conversion device. . In this case, the signal converter can be operated using the second fluorescent image branched by the distributor as a trigger, and a high-speed event can be accurately recorded.

  In still another aspect of the present invention, the spot characteristic on the imaging surface of the signal converter is adjusted in accordance with the spectral luminance distribution characteristic of the phosphor constituting the output surface of the image intensifier. In this case, the spot characteristic on the imaging surface can be optimized by a chromatic aberration relay optical system suitable for the phosphor of the image intensifier.

  In still another aspect of the present invention, the first lens group and the second lens group are provided in order from the output surface, and the imaging magnification can be corrected by adjusting the distance between the first lens group and the second lens group. is there. In this case, in this case, the image on the output surface can be formed on the imaging surface with an appropriate magnification, and high-accuracy imaging is possible.

In still another aspect of the present invention, when the numerical aperture of the first lens group is NA1 and the numerical aperture of the second lens group is NA2, the following conditional expression (1)
1.15 ≦ NA2 / NA1 ≦ 1.8 (1)
Satisfied. By setting it within the range of the conditional expression (1), it is possible to suppress light loss when projecting the output surface of the image intensifier on the imaging surface of the signal converter at substantially the same magnification.

In still another aspect of the present invention, when the focal length of the first lens group is f1, and the focal length of the second lens group is f2, the following conditional expression (2)
0.5 ≦ f2 / f1 ≦ 2.0 (2)
Is satisfied, more preferably 0.5 ≦ f2 / f1 ≦ 0.9 (2) ′.
Satisfied. By setting the conditional expression (2) within the range, it is possible to project the output surface of the image intensifier on the image pickup surface of the signal converter with substantially equal magnification while suppressing distortion.

  In still another aspect of the present invention, the imaging magnification is adjusted in a range of ± 1.5% while substantially maintaining the imaging characteristics. In this case, it is possible to adjust the finish so that manufacturing errors of the optical elements and the like constituting the relay optical system can be absorbed.

  In order to solve the above problems, a measurement system according to the present invention operates an imaging device in synchronization with an illumination unit that outputs laser light, an illumination drive unit that operates the illumination unit, the above-described imaging device, and the illumination unit. And an imaging drive unit.

  According to the measurement system, it is possible to spatially identify and measure a weak and passive phenomenon that responds to laser light irradiation.

It is the schematic explaining the imaging device which concerns on one Embodiment of this invention. It is sectional drawing explaining the 1st Example of the relay optical system integrated in the imaging device of FIG. It is a graph which shows the spectral luminance distribution of the fluorescent substance used with the imaging device of FIG. (A) shows various aberrations at low magnification of the relay optical system of the first example, and (B) shows various aberrations at standard magnification. Various aberrations of the relay optical system of the first example at high magnification are shown. (A) And (B) shows the lateral aberration at the time of low magnification of the relay optical system of the first example. (A) and (B) show lateral aberrations at the standard magnification of the relay optical system of the first example. (A) And (B) shows the lateral aberration at the time of high magnification of the relay optical system of the first example. (A)-(C) show the spot diagram by the relay optical system of the 1st example. (A) And (B) shows the encircled energy diagram at the time of low magnification of the relay optical system of the first embodiment. (A) And (B) shows the encircled energy diagram at the time of standard magnification of the relay optical system of 1st Example. (A) And (B) shows the encircled energy diagram at the time of high magnification of the relay optical system of the first embodiment. It is sectional drawing explaining 2nd Example of a relay optical system. It is sectional drawing explaining the 3rd Example of a relay optical system. It is sectional drawing explaining the 4th Example of a relay optical system. It is the schematic explaining the structure of the measuring device incorporating the imaging device of FIG.

[1. Imaging device structure, etc.)
Hereinafter, the structure and the like of an imaging apparatus according to an embodiment of the present invention will be described. An imaging apparatus 10 shown in FIG. 1 is an image intensifier 11 that converts a weak event into a fluorescence image, and a fluorescence image output from the image intensifier 11 (hereinafter simply referred to as a fluorescence image) as an electrical image. A signal conversion device 12 that converts the signal into a signal, a relay optical system 13 that projects a fluorescent image on the output surface 11 b of the image intensifier 11 onto the imaging surface 12 a of the signal conversion device 12, and a distributor 15 provided in the relay optical system 13. And a timing setting device 17 for defining an imaging timing for operating the signal conversion device 12 from the second fluorescent image separated by.

  The image intensifier 11 converts, for example, events that occur randomly in the natural world, that is, the arrival of weak electromagnetic waves or the generation and disappearance of light, or their movement into fluorescence and a fluorescent image that is an aggregate thereof. In other words, the image intensifier 11 receives the electromagnetic wave having a predetermined wavelength (incident electromagnetic wave to the photoelectric conversion unit 21) or moves (the main component is defined in a direction different from the photoelectric conversion unit 21 in terms of time). And a fluorescent image corresponding to the detected intensity distribution of the electromagnetic wave is output from the output surface 11b. For this reason, the image intensifier 11 includes a photoelectric conversion unit 21 disposed at the input stage, a proximity multiplier 23 disposed at the subsequent stage, and a fiber optic plate 24 disposed at the output stage.

  In the image intensifier 11, the photoelectric conversion unit 21 is disposed on the input side where electromagnetic waves arrive, and converges while accelerating the electrons emitted from the photoelectron conversion surface 21a and the photoelectron conversion surface 21a that photoelectrically converts the incident electromagnetic wave. And an electrode portion 21b. The proximity type multiplication element 23 is a micro channel plate (MCP) that multiplies electrons accelerated by the photoelectric conversion unit 21 and may be formed by stacking MCPs in a plurality of stages. The fiber optic plate 24 is provided on the input side of a fluorescent screen 24a that converts electrons multiplied by the proximity type multiplier 23 into a fluorescent image, and a fiber bundle that is emitted from the fluorescent screen 24a and integrated by melting. And an output surface 11b for emitting a fluorescent image incident from one end as it is from the other end.

  The photoelectric conversion surface 21a provided in the photoelectric conversion unit 21 has a diameter of, for example, 10 cm, and the output surface 11b provided in the fiber optic plate 24 has, for example, a diameter of 2.5 cm. In this case, the magnification of the image intensifier 11 is 0.25.

  The signal conversion device 12 includes, for example, a solid-state imaging device 31 that is a CMOS-type imaging device and a drive circuit 32 that causes the solid-state imaging device 31 to perform an imaging operation, and is based on a timing signal output from the timing setting device 17. The solid-state imaging device 31 can perform an imaging operation. The solid-state imaging device 31 has an imaging surface 12a. The entire imaging surface 12a is divided into m (for example, 12) rows in the Y direction and n (for example, 12) columns in the X direction so as to divide the imaging surface 12a into a grid. As m rows × n columns = A (for example, 144) channel local area AR1. Each local area AR1 functions independently as a CMOS type image sensor, and two-dimensional image detection is possible. Each local area AR1 can perform an imaging operation at different timings, and independently performs an imaging operation based on individual timing signals output from the timing setting device 17 described above. That is, the output surface 11b of the image intensifier 11 can be observed individually by virtually dividing it into m rows × n columns = A channel by the local area AR1 constituting the solid-state imaging device 31.

  The relay optical system 13 includes a distributor 15 disposed on the upstream side of the optical path along the optical axis OA and a main body optical system 14 disposed on the downstream side of the optical path from the distributor 15. The relay optical system 13 projects an image of the output surface 11 b of the image intensifier 11 on the imaging surface 12 a of the signal converter 12 at approximately the same magnification. The relay optical system 13 is telecentric on the output surface 11 b of the image intensifier 11, that is, the object side, and is non-telecentric on the imaging surface 12 a of the signal converter 12, that is, the image side.

  The distributor 15 is a prism having a built-in beam split mirror 15c which is a kind of half mirror. The distributor 15 distributes the fluorescent image on the output surface 11b of the image intensifier 11 into two fluorescent images having a predetermined intensity, that is, a first fluorescent image and a second fluorescent image. The light beam of the first fluorescent image that travels straight through the beam split mirror 15c of the distributor 15 is guided to the first optical path OP1, passes through the main body optical system 14, and enters the imaging surface 12a of the signal conversion device 12. The light beam of the second fluorescent image reflected and bent by the beam split mirror 15c of the distributor 15 is guided to the second optical path OP2 and enters the imaging surface 41a of the photoelectric imaging tube 41 of the timing setting device 17. The distributor 15 is set so that the intensity of light transmitted through the beam split mirror 15c and the intensity of light reflected without being transmitted are α (transmittance) versus β (reflectance). Specifically, when the reduction in transmittance due to the absorption of the distributor 15 itself is not taken into account, for example, the transmittance α = 70% and the reflectance β = 30% are set. Note that it is generally desirable that the ratio of α / β be larger than 1 from the viewpoint of increasing the amount of light of the first fluorescent image incident on the imaging surface 12a of the signal converter 12.

  The main optical system 14 includes a first lens group 14a facing the output surface 11b of the image intensifier 11 via the distributor 15, and a second lens group 14b disposed on the downstream side of the optical path from the first lens group 14a. With. An interval adjusting member 14c is provided between the first lens group 14a and the second lens group 14b. The interval adjusting member 14c finely adjusts the projection magnification of the relay optical system 13 within a range of, for example, about ± 1.5% by adjusting the interval between the first lens group 14a and the second lens group 14b. Specifically, when connecting the lens barrel of the first lens group 14a and the lens barrel of the second lens group 14b to each other, the thickness of the sheet-like member (for example, metal foil) inserted between the connection surfaces is changed. As a result, the distance between the first lens group 14a and the second lens group 14b can be adjusted on the micron order, and the magnification can be adjusted as described above. By adjusting the magnification, it is considered that tolerances or manufacturing errors of the optical elements constituting the distributor 15 and the main body optical system 14 can be absorbed, and imaging with a precise magnification or the like becomes possible.

  The first lens group 14a constituting the main optical system 14 will be described in detail later. For example, in the order from the object side to the image side, a lens having a positive refractive power, and a meniscus lens having a positive refractive power convex toward the object side, , A negative refractive power lens, a cemented lens convex on the image side, and two positive refractive power lenses. The second lens group 14b includes, in order from the object side to the image side, a cemented lens that is convex on the object side, a negative refractive power lens, a positive refractive power lens, and a positive refractive power lens that is convex on the object side. It consists of.

  The specific focal length f1 of the first lens group 14a constituting the main optical system 14 is set in a range of, for example, about 50 mm to 90 mm, and the specific focal length f2 of the second lens group 14b is, for example, 16 mm to 59 mm. It was set to a range of degree. The specific pupil diameter of the first lens group 14a is set in a range of about 26 mm to 43 mm, for example, and the specific pupil diameter of the second lens group 14b is set in a range of about 26 mm to 43 mm, for example. .

As a result, when the numerical aperture of the first lens group 14a is NA1, and the numerical aperture 14b of the second lens group 14b is NA2, the numerical aperture ratio NA2 / NA1 is in the range of about 1.15 to 1.8. In the main body optical system 14 that achieved a particularly high performance, NA2 / NA1 was within the range of about 1.15 to 1.45. That is, the main body optical system 14 has the following conditional expression (1).
1.15 ≦ NA2 / NA1 ≦ 1.8 (1)
Satisfied. By setting the conditional expression (1) within the range, it is possible to suppress distortion and light loss when the output surface 11b of the image intensifier 11 is projected onto the image pickup surface 12a of the signal converter 12 at substantially the same magnification. . That is, when NA2 / NA1 exceeds the lower limit or the upper limit as described above, the symmetry along the optical axis OA of the main body optical system 14 decreases. Specifically, if the condensing rate of the main body optical system 14 is preserved, the distance from the output surface 11b that is the object surface to the imaging surface 12a that is the image surface becomes long, and the imaging surface 12a from the output surface 11b. If the distance up to is stored, the lens diameter becomes small, and the condensing rate of the main body optical system 14 is lowered.

On the other hand, in the main body optical system 14, the ratio f2 / f1 of the focal length of the second lens group 14b to the first lens group 14a is within the range of about 0.55 to 0.9, and the main body optical that achieves particularly high performance. In the system 14, f2 / f1 was within the range of about 0.7 to 0.9. Here, the main body optical system 14 is a somewhat reduced system due to the specification, but considering the case of a somewhat enlarged system or a strictly equal magnification system, the range of f2 / f1. Is considered to be a range including the reciprocal thereof. That is, the main optical system 14 has the following conditional expression (2)
0.5 ≦ f2 / f1 ≦ 2.0 (2)
Is satisfied, more preferably 0.5 ≦ f2 / f1 ≦ 0.9 (2) ′
Satisfied. By making it within the range of the above conditional expression (2), the output surface 11b of the image intensifier 11 can be projected onto the imaging surface 12a of the signal converter 12 with substantially equal magnification while suppressing distortion and light loss. . That is, when f2 / f1 exceeds the lower limit or the upper limit as described above, the symmetry along the optical axis OA of the main body optical system 14 decreases.

  The timing setting device 17 includes a photoelectric imaging tube 41 into which a light beam of the second fluorescent image guided to the second optical path OP2 by being reflected by the distributor 15 and a second fluorescent image guided to the second optical path OP2. A trigger optical system 42 for projecting the image on the imaging surface 41 a of the photoelectric imaging tube 41, a logic circuit unit 43 that operates based on the detection signal of the photoelectric imaging tube 41, and a position that operates based on the output of the logic circuit unit 43 / Timing control circuit 44. The timing setting device 17 monitors the light flux of the second fluorescent image distributed by the distributor 15 of the relay optical system 13 and appropriately captures the first fluorescent image by the solid-state imaging device 31 of the signal conversion device 12. To do.

  The photoelectric imaging tube 41 is a multi-anode photomultiplier, and its imaging surface 41a has m (for example, 12) rows in the Y direction and n (for example, 12) columns in the X direction, and as a whole m rows × n columns = A (for example, 144) channel segment area AR2 is included. In other words, the photoelectric imaging tube 41 has a mesh dynode corresponding to the segment area AR2 of the A channel, and the second on the imaging surface 41a is only from the anode of the dynode to which the second fluorescent image is input with a predetermined intensity or more. A current obtained by photoelectrically converting the fluorescent image is output. Note that the time required for the light beam of the second fluorescent image to enter the imaging surface 41a and output the current is about 1 nanosecond. Based on the current output from each anode, the photoelectric imaging tube 41 is able to identify which divided region AR2 the light beam of the second fluorescent image has entered along with its appearance timing. In other words, the output surface 11b of the image intensifier 11 is virtually divided into m rows × n columns = A channels by the divided area AR2 constituting the imaging surface 41a of the photoelectric imaging tube 41, and can be individually monitored. ing. Note that the virtual segmented area on the output surface 11b of the image intensifier 11 corresponding to such a segmented area AR2 also corresponds to the local area AR1 of the solid-state imaging device 31. Here, a segmented area in which a weak event appears on the output surface 11b is referred to as an appearing area.

  The trigger optical system 42 projects the image of the output surface 11 b of the image intensifier 11 on the imaging surface 41 a of the photoelectric imaging tube 41 at approximately the same magnification. The trigger optical system 42 places the highest importance on brightness, and is non-telecentric on both the object side and the image side. The distributor 15 is also a part of the trigger optical system 42.

  The logic circuit unit 43 includes, for example, a wave height discriminator, and determines whether or not the current output from each anode of the photoelectric imaging tube 41 exceeds a predetermined threshold, that is, the appearance timing of a weak event, for example, in a binary manner. Detect as sensitive information. Specifically, the logic circuit unit 43 thresholds the current output from the anode of an arbitrary row that constitutes the photoelectric imaging tube 41 and the current output from the anode of an arbitrary column. The second fluorescent image detected by 41 is converted into position information and timing information regarding the Y direction (m rows) and the X direction (n columns), respectively. That is, when the light beam of the second fluorescent image is incident on the specific segmented area AR2 of the photoelectric imaging tube 41, the logic circuit unit 43 outputs the information on the time, position, etc., and is detected by the image intensifier 11. It is possible to obtain the time, position, direction of movement, etc. of this event for the weak event.

  The position / timing control circuit 44 includes, for example, a filter, a delay circuit, and the like. The position / timing control circuit 44 controls the signal conversion device 12 based on information output from the logic circuit unit 43, that is, position information and timing information regarding the appearance of a weak event. Make it work. Specifically, the segmented area AR2 of the photoelectric imaging tube 41 and the local area AR1 of the solid-state image sensor 31 are correlated, and the position / timing control circuit 44 has the second fluorescent image in the segmented area AR2. A drive signal for driving the drive circuit 32 of the signal conversion device 12 is output so that the first fluorescent image is picked up in the local region AR1 of the solid-state image pickup device 31 corresponding to the detected appearance region. In other words, the imaging operation by the signal conversion device 12 can be limited to the minimum necessary according to the time, position, moving direction, etc., where the weak event detected by the photoelectric imaging tube 41 appears, so It is possible to extract only high-speed and weak events from the output of the magnification unit 11 and to take an image with a high S / N ratio. At this time, the position / timing control circuit 44 can also adjust the exposure time of imaging by the solid-state imaging device 31 based on the output of the photoelectric imaging tube 41.

  As is apparent from the above description, according to the imaging apparatus 10 of the present embodiment, the relay optical system 13 disposed between the image intensifier 11 and the signal converter 12 is an output surface of the image intensifier 11. Since it is telecentric on the 11b side, that is, on the object side, coupled with the fact that the light beam emitted from the output surface 11b has a light distribution showing central concentration, the fluorescent image on the output surface 11b is transformed into distortion on the imaging surface 12a. Re-imaging can be performed in a highly accurate state and a bright state with reduced aberrations, and a weak fluorescent image formed by the image intensifier 11 can be reliably detected with high accuracy.

[2. Relay optical system)
[2a. First Example of Relay Optical System]
Hereinafter, a specific lens configuration and the like of the relay optical system 13 of the first embodiment will be described with reference to FIG. The relay optical system 13 of the first example includes an incident-side distributor 15, a first lens group 14a having a positive refractive power as a whole, a second lens group 14b having a positive refractive power as a whole, and an output. Side prism portion 14d. The distributor 15, the first lens group 14a, the second lens group 14b, and the prism portion 14d are arranged on the optical axis OA from the object side with the image intensifier 11 toward the image side with the signal converter 12. Are provided in order. Among these, the first and second lens groups 14 a and 14 b and the prism portion 14 d constitute a main body optical system 14.

  Hereinafter, a specific lens configuration and the like of the relay optical system 13 will be described. First, the distributor 15 functions similarly to a thick parallel plate. The first lens group 14a includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, And a seventh lens L7. The second lens group 14b includes, in order from the object side, an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, and a twelfth lens L12. The prism portion 14d functions in the same manner as a thick parallel plate. In the first lens group 14a, a stop ST is disposed between the sixth lens L6 and the seventh lens L7.

  In the first lens group 14a of the relay optical system 13, the first lens L1 is a biconvex lens. The second lens L2 is a meniscus lens having a convex incident side and a concave outgoing side. The third lens L3 is a meniscus lens having a convex incident side and a concave outgoing side. The fourth lens L4 is a biconcave lens. The fifth lens L5 is a biconvex lens, and is cemented to the fourth lens L4 on the incident side, and constitutes a cemented lens together with the fourth lens L4. The sixth lens L6 is a meniscus lens having a concave incident side and a convex outgoing side. The seventh lens L7 is a biconvex lens.

  In the second lens group 14b of the relay optical system 13, the eighth lens L8 is a biconvex lens. The ninth lens L9 is a biconcave lens, which is cemented to the eighth lens L8 on the incident side, and constitutes a cemented lens together with the eighth lens L8. The tenth lens L10 is a biconcave lens. The eleventh lens L11 is a biconvex lens. The twelfth lens L12 is a meniscus lens having a convex incident side and a concave outgoing side.

Table 1 shows lens data and the like of the relay optical system 13 of the first example. In the upper column of Table 1, “surface number” is a number assigned to the surface of each lens in order from the output surface (OBJ) 11b side. “RDY” indicates the radius of curvature, and “THI” indicates the lens thickness or air space between the next surface. Further, “material” indicates a lens material (symbol is the glass name of OHARA INC.), And “light beam effective diameter” means the maximum diameter of the light beam passing through the lens.

Table 2 shows paraxial quantities of the relay optical system 13 of the first example. The three sections constituting the column of Table 2 show the cases of low magnification (−1.5%), standard magnification, and high magnification (+ 1.5%), respectively.

  In designing the relay optical system 13 of the first embodiment shown in FIG. 2, the fluorescent image of the output surface 11 b of the image intensifier 11 is placed on the imaging surface 12 a of the signal converter 12 so as to be telecentric on the object side. Is projected with less aberration. Although the projection magnification by the relay optical system 13 is not strictly equal, it is considered that the output surface 11b and the imaging surface 41a have a one-to-one correspondence. As described above, by making the relay optical system 13 telecentric on the object side, the fluorescent image formed on the imaging surface 41a is less distorted or blurred. However, the relay optical system 13 is non-telecentric on the image side in order to ensure the luminance of the fluorescent image formed on the imaging surface 41a. Since the light beam emitted from the output surface 11b exhibits a center-concentrated light distribution or angular distribution, the fluorescent image on the output surface 11b can be taken into the telecentric relay optical system 13 at a relatively high rate on the object side.

  The resulting specification of the relay optical system 13 is that the conjugate length is 250 mm, the projection magnification is 18/25 times, the object side NA is 0.24, and the resolution (spot RMS diameter) is 14 μm. The distortion is 0.1%, the transmittance as an integral value with wavelength weight is 72%, and the magnification can be adjusted by ± 1.5%. The numerical aperture ratio NA2 / NA1 of the first lens group 14a and the second lens group 14b is 1.37, and the focal length ratio of the first lens group 14a and the second lens group 14b is 0. .74.

上記表３を活用して波長ごとに重み付けをすることにより、図２に示すリレー光学系１３では、イメージ増倍装置１１の出力面１１ｂ上のスポットを信号変換装置１２の撮像面１２ａ上に極小サイズで集光させることとしている。 FIG. 3 is a graph for explaining the incident light characteristics used for determining the specifications of the relay optical system 13, and shows the spectral luminance distribution of the phosphor constituting the phosphor screen 24 a of the image intensifier 11. The relay optical system 13 shown in FIG. 2 is designed on the assumption that the phosphor P47 is used. Specifically, as shown in Table 3 below, the spectral luminance distribution of the phosphor P47 was finely read and divided into a plurality of bands, and the barycentric wavelength was obtained for each band (see Table 3).

By weighting each wavelength by using Table 3 above, in the relay optical system 13 shown in FIG. 2, the spot on the output surface 11 b of the image intensifier 11 is minimized on the imaging surface 12 a of the signal converter 12. It is supposed to be condensed by size.

  FIG. 4A shows various aberrations (spherical aberration, astigmatism, and distortion) of the relay optical system of Example 1 when the magnification is low (−1.5%). B) shows various aberrations (spherical aberration, astigmatism and distortion) at the standard magnification (± 0%), and FIG. 5 shows various aberrations at the high magnification (+ 1.5%). Aberrations (spherical aberration, astigmatism and distortion) are shown.

  FIGS. 6 (A) and 6 (B) show lateral aberrations when the relay optical system of the first example has a low magnification (−1.5%), and FIGS. 7 (A) and 7 (B). ) Shows the lateral aberration when the standard magnification (± 0%) is used, and FIGS. 8A and 8B show the lateral aberration when the magnification is high (+ 1.5%). Yes.

表４からも明らかなように、物体高が変化しても、ＲＭＳスポット直径があまり大きく変化しないことが分かる。 FIGS. 9A to 9C show spot diagrams at a low magnification (−1.5%), a standard magnification, and a high magnification (+ 1.5%) of the relay optical system of the first example. Table 4 below shows the RMS spot diameter at standard magnification.

As is clear from Table 4, it can be seen that the RMS spot diameter does not change much even if the object height changes.

  10 (A) and 10 (B) show an encircled energy diagram of the first example when the magnification is low (−1.5%). FIG. 11 (A) And 11 (B) show the encircled energy diagram when the standard magnification (± 0%) is used, and FIGS. 12 (A) and 12 (B) show the high magnification (+ 1.5%). The encircled energy diagram in the case is shown. It can be seen that the energy distribution smoothly decreases when the abscissa radius increases at each magnification spot. The relay optical system of the first embodiment causes diffraction or the like on the imaging surface 12a of the signal conversion device 12. It can be seen that a sharp fluorescent image with little blur is projected.

[2b. Second embodiment of relay optical system]
Hereinafter, a specific lens configuration and the like of the relay optical system 13 of the second embodiment will be described with reference to FIG. The relay optical system 13 of the second embodiment includes, in order from the object side, a distributor 15 on the incident side, a first lens group 14a having a positive refractive power as a whole, and a second lens having a positive refractive power as a whole. A group 14b and an exit-side prism portion 14d are provided.

  Hereinafter, a specific lens configuration and the like of the relay optical system 13 will be described. The first lens group 14a includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. It consists of a lens L7. The second lens group 14b includes, in order from the object side, an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, and a twelfth lens L12. In the illustrated relay optical system 13, the object-side distributor 15 and the image-side prism portion 14d function in the same manner as a thick parallel plate. In the first lens group 14a, a stop ST is disposed between the sixth lens L6 and the seventh lens L7.

  In the first lens group 14a of the relay optical system 13, the first lens L1 is a biconvex lens. The second lens L2 is a meniscus lens having a convex incident side and a concave outgoing side. The third lens L3 is a biconcave lens. The fourth lens L4 is a biconcave lens. The fifth lens L5 is a biconvex lens, and is cemented to the fourth lens L4 on the incident side, and constitutes a cemented lens together with the fourth lens L4. The sixth lens L6 is a meniscus lens having a concave incident side and a convex outgoing side. The seventh lens L7 is a biconvex lens.

  In the second lens group 14b of the relay optical system 13, the eighth lens L8 is a meniscus lens having a convex incident side and a concave outgoing side. The ninth lens L9 is a meniscus lens having a convex incident side and a concave outgoing side, and is cemented to the eighth lens L8 on the incident side, and constitutes a cemented lens together with the eighth lens L8. The tenth lens L10 is a biconcave lens. The eleventh lens L11 is a biconvex lens. The twelfth lens L12 is a meniscus lens having a convex incident side and a concave outgoing side.

Table 5 shows lens data and the like of the relay optical system 13 of the second example. In the upper column of Table 5, “surface number” is a number assigned to each lens surface in order from the output surface (OBJ) 11b side. “RDY” indicates the radius of curvature, and “THI” indicates the lens thickness or air space between the next surface. Further, “material” indicates a lens material, and “light ray effective radius” means the maximum radius of a light beam passing through the lens.

  In designing the relay optical system 13 of the second embodiment shown in FIG. 13, the fluorescent image of the output surface 11b of the image intensifier 11 is placed on the imaging surface 12a of the signal converter 12 so as to be telecentric on the object side. Is projected with less aberration. However, the relay optical system 13 is non-telecentric on the image side in order to ensure the luminance of the fluorescent image formed on the imaging surface 41a. Since the light beam emitted from the output surface 11b exhibits a center-concentrated light distribution or angular distribution, the fluorescent image on the output surface 11b can be taken into the telecentric relay optical system 13 at a relatively high rate on the object side.

  In the case of the relay optical system 13 of the second example, the numerical aperture ratio NA2 / NA1 of the first lens group 14a and the second lens group 14b is 1.30, and the first lens group 14a and the second lens. The focal length ratio f2 / f1 of the group 14b is 0.77.

[2c. Third embodiment of relay optical system]
Hereinafter, a specific lens configuration and the like of the relay optical system 13 of the third example will be described with reference to FIG. The relay optical system 13 of the third embodiment includes, in order from the object side, a distributor 15 on the incident side, a first lens group 14a having a positive refractive power as a whole, and a second lens having a positive refractive power as a whole. A group 14b and an exit-side prism portion 14d are provided.

  Hereinafter, a specific lens configuration and the like of the relay optical system 13 will be described. The first lens group 14a includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. It consists of a lens L7. The second lens group 14b includes, in order from the object side, an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, and a twelfth lens L12. In the illustrated relay optical system 13, the object-side distributor 15 and the image-side prism portion 14d function in the same manner as a thick parallel plate. In the first lens group 14a, a stop ST is disposed between the sixth lens L6 and the seventh lens L7.

  In the first lens group 14a of the relay optical system 13, the first lens L1 is a biconvex lens. The second lens L2 is a meniscus lens having a convex incident side and a concave outgoing side. The third lens L3 is a meniscus lens having a convex incident side and a concave outgoing side. The fourth lens L4 is a biconcave lens. The fifth lens L5 is a biconvex lens, and is cemented to the fourth lens L4 on the incident side, and constitutes a cemented lens together with the fourth lens L4. The sixth lens L6 is a meniscus lens having a concave incident side and a convex outgoing side. The seventh lens L7 is a biconvex lens.

  In the second lens group 14b of the relay optical system 13, the eighth lens L8 is a biconvex lens. The ninth lens L9 is a biconcave lens, which is cemented to the eighth lens L8 on the incident side, and constitutes a cemented lens together with the eighth lens L8. The tenth lens L10 is a biconcave lens. The eleventh lens L11 is a biconvex lens. The twelfth lens L12 is a meniscus lens having a convex incident side and a concave outgoing side.

Table 6 shows lens data of the relay optical system 13 of the third example. In the upper column of Table 6, “surface number” is a number assigned to the surface of each lens in order from the output surface (OBJ) 11b side. “RDY” indicates the radius of curvature, and “THI” indicates the lens thickness or air space between the next surface. Further, “material” indicates a lens material, and “light ray effective radius” means the maximum radius of a light beam passing through the lens.

  When designing the relay optical system 13 of the third embodiment shown in FIG. 14, the fluorescent image of the output surface 11b of the image intensifier 11 is placed on the imaging surface 12a of the signal converter 12 so as to be telecentric on the object side. Is projected with less aberration. However, the relay optical system 13 is non-telecentric on the image side in order to ensure the luminance of the fluorescent image formed on the imaging surface 41a. Since the light beam emitted from the output surface 11b exhibits a center-concentrated light distribution or angular distribution, the fluorescent image on the output surface 11b can be taken into the telecentric relay optical system 13 at a relatively high rate on the object side.

  In the case of the relay optical system 13 of the third example, the numerical aperture ratio NA2 / NA1 of the first lens group 14a and the second lens group 14b is 1.40, and the first lens group 14a and the second lens. The focal length ratio f2 / f1 of the group 14b is 0.72.

[2d. Fourth embodiment of relay optical system]
Hereinafter, a specific lens configuration and the like of the relay optical system 13 of the fourth example will be described with reference to FIG. The relay optical system 13 of the fourth example includes, in order from the object side, a distributor 15, a first lens group 14a, a second lens group 14b, a prism portion 14d, a third lens group 114a, and a mirror 13r. And a fourth lens group 114b.

  Hereinafter, a specific lens configuration and the like of the relay optical system 13 will be described. The first lens group 14a includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. It consists of a lens L7. The second lens group 14b includes, in order from the object side, an eighth lens L8, a ninth lens L9, a tenth lens L10, an eleventh lens L11, and a twelfth lens L12. The third lens group 114a includes, in order from the object side, a thirteenth lens L13, a fourteenth lens L14, a fifteenth lens L15, and a sixteenth lens L16. The fourth lens group 114b includes, in order from the object side, a seventeenth lens L17, an eighteenth lens L18, a nineteenth lens L19, a twentieth lens L20, a twenty-first lens L21, a twenty-second lens L22, and a twenty-third lens. The lens includes a lens L23, a 24th lens L24, a 25th lens L25, and a 26th lens L26. In the illustrated relay optical system 13, the distributor 15 on the object side and the prism portion 14 d at the intermediate position function in the same manner as a thick parallel plate. In the fourth lens group 114b, a stop ST is disposed between the twentieth lens L20 and the twenty-first lens L21.

  In the first lens group 14a of the relay optical system 13, the first lens L1 is a biconvex lens. The second lens L2 is a meniscus lens having a convex incident side and a concave outgoing side. The third lens L3 is a meniscus lens having a convex incident side and a concave outgoing side. The fourth lens L4 is a biconcave lens. The fifth lens L5 is a biconvex lens, and is cemented to the fourth lens L4 on the incident side, and constitutes a cemented lens together with the fourth lens L4. The sixth lens L6 is a meniscus lens having a concave incident side and a convex outgoing side. The seventh lens L7 is a biconvex lens.

  In the second lens group 14b, the eighth lens L8 is a biconvex lens. The ninth lens L9 is a biconcave lens, which is cemented to the eighth lens L8 on the incident side, and constitutes a cemented lens together with the eighth lens L8. The tenth lens L10 is a biconcave lens. The eleventh lens L11 is a biconvex lens. The twelfth lens L12 is a meniscus lens having a convex incident side and a concave outgoing side.

  In the third lens group 114a, the thirteenth lens L13 is a biconcave lens. The fourteenth lens L14 is a meniscus lens having a convex incident side and a concave outgoing side, and is cemented to the thirteenth lens L13 on the incident side, and constitutes a cemented lens together with the thirteenth lens L13. The fifteenth lens L15 is a meniscus lens having a concave entrance side and a convex exit side. The sixteenth lens L16 is a biconvex lens.

  In the fourth lens group 114b, the seventeenth lens L17 is a biconcave lens. The eighteenth lens L18 is a biconcave lens. The nineteenth lens L19 is a biconvex lens, which is cemented to the eighteenth lens L18 on the incident side, and constitutes a cemented lens together with the eighteenth lens L18. The twentieth lens L20 is a biconvex lens. The twenty-first lens L21 is a meniscus lens having a convex incident side and a concave outgoing side. The twenty-second lens L22 is a biconvex lens. The 23rd lens L23 is a biconcave lens, and is cemented to the 22nd lens L22 on the incident side, and constitutes a cemented lens together with the 22nd lens L22. The 24th lens L24 is a biconcave lens. The 25th lens L25 is a meniscus lens having a concave incident side and a convex outgoing side. The twenty-sixth lens L26 is a meniscus lens having a convex incident side and a concave outgoing side.

Table 7 shows lens data and the like of the relay optical system 13 of the fourth example. In the upper column of Table 7, “surface number” is a number assigned to the surface of each lens in order from the output surface (OBJ) 11b side. “RDY” indicates the radius of curvature, and “THI” indicates the lens thickness or air space between the next surface. Further, “material” indicates a lens material, and “light ray effective radius” means the maximum radius of a light beam passing through the lens.

  In designing the relay optical system 13 of the fourth embodiment shown in FIG. 15, the fluorescent image of the output surface 11 b of the image intensifier 11 is placed on the imaging surface 12 a of the signal converter 12 so as to be telecentric on the object side. Is projected with less aberration. However, the relay optical system 13 is non-telecentric on the image side in order to ensure the luminance of the fluorescent image formed on the imaging surface 41a. Since the light beam emitted from the output surface 11b exhibits a center-concentrated light distribution or angular distribution, the fluorescent image on the output surface 11b can be taken into the telecentric relay optical system 13 at a relatively high rate on the object side.

  In the relay optical system 13 of the fourth example, the numerical aperture ratio NA2 / NA1 of the first lens group 14a and the second lens group 14b is 1.15, and the first lens group 14a and the second lens are as follows. The focal length ratio f2 / f1 of the group 14b is 0.87.

Table 8 below summarizes the focal length ratio f2 / f1 and the numerical aperture ratio NA2 / NA1 for the first lens group 14a and the second lens group 14b with respect to the first to fourth examples. It is. In addition, about the 5th-8th Example in Table 9, although description of the specific lens structure was abbreviate | omitted, it has a lens structure similar to the 1st-4th Example.

[3. Measurement system structure etc.)
Hereinafter, the structure and the like of the measurement system according to an embodiment of the present invention will be described with reference to FIG.

  The measurement system 100 includes an illumination unit 81 that outputs laser light, an illumination drive unit 82 that operates the illumination unit 81, an imaging optical system 83 that focuses and forms an electromagnetic wave from a measurement target, and an illumination unit. The illumination control unit 85 that controls the operation of 81, the imaging device 10 that captures the electromagnetic waves collected by the imaging optical system 83, and a visualization / storage device 84 associated with the imaging device 10 are provided.

  The illumination unit 81 includes a laser light source 81a having a pulse laser that generates illumination laser light, and an irradiation optical system 81b having two polygon mirrors that scan the laser light two-dimensionally. The irradiation optical system 81b is provided with a motor 81d for rotating the polygon mirror, and the motor 81d is provided with an encoder 81e for detecting the rotation angle of the motor 81d. .

  The illumination drive unit 82 includes a trigger circuit that causes the laser light source 81a to emit light, and adjusts the emission timing of the illumination laser light emitted from the laser light source 81a based on a reference signal from the control unit 85.

  The illumination control unit 85 associated with the illumination unit 81 or the like controls the operation of the illumination drive unit 82 and includes a pulse generator that outputs a reference signal to the trigger circuit of the illumination drive unit 82. The illumination control unit 85 controls the operation of the motor 81d while monitoring the encoder 81e provided in the illumination unit 81 based on the reference signal from the pulse generator, and the illumination unit 81 via the illumination drive unit 82. To scan with laser light.

  The imaging device 10 captures an electromagnetic wave from a measurement target through the imaging optical system 83, but has the structure shown in FIG.

  The visualization / storage device 84 converts the image signal output irregularly from the signal conversion device 12 of the imaging device 10 into data visualized according to the intensity and the like, and the visualized data is stored in the storage device as needed. store. The visualization / storage device 84 controls the operation state of the imaging device 10, and adjusts the shooting direction and the like of an object to be shot by the imaging device 10 via the imaging optical system 83. The imaging area by the imaging device 10 covers the irradiation range of the laser beam by the illumination unit 81.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and can be implemented in various modes without departing from the gist thereof. Such modifications are also possible.

  That is, the configuration of the image intensifier 11 is not limited to that illustrated in FIG. 1 and can be various.

  Further, the solid-state imaging device 31 constituting the signal conversion device 12 is not limited to a CMOS imaging device, and a CCD imaging device can be used. When using a CCD type image sensor, the shutter function can be utilized.

  The photoelectric imaging tube 41, the trigger optical system 42, the logic circuit unit 43, the control circuit 44, and the like constituting the timing setting device 17 are merely examples, and various modifications are possible. For example, the photoelectric imaging tube 41 can be a hybrid photodetector. A hybrid photodetector is a vacuum tube in which a multi-pixel sensor such as a CCD or CMOS is enclosed, and is converted into photoelectrons on the surface of the vacuum tube like a photoelectric imaging tube, and the photoelectrons are converted into an electrostatic lens in a vacuum. The photodetection signal is obtained by propagating the laser beam directly to the silicon multi-pixel sensor.

  In the measurement system 100, a control unit that comprehensively controls the operation of the illumination unit 81 and the operation of the imaging device 10 can be provided. By such a control unit, the observation direction by the imaging device 10 and the irradiation direction of the laser light by the illumination unit 81 can be matched to perform accurate association, and the observation timing by the imaging device 10 and the illumination unit It is also possible to detect a difference, that is, a delay from the timing of the laser beam by 81.

  The imaging apparatus 10 according to the above-described embodiment can be applied to various applications, for example, various fields such as inspection, monitoring, and medical care, by appropriately correcting the specification.

AR1 ... local region, AR2 ... segmented region, L1 to L12 ... lens, OA ... optical axis, OP1 ... optical path, OP2 ... optical path, 10 ... imaging device, 11 ... image intensifier, 11b ... output surface, 12 ... signal conversion Device: 12a ... Imaging surface, 13 ... Relay optical system, 14 ... Main body optical system, 14a, 14b ... First and second lens groups, 14c ... Spacing adjustment member, 14d ... Prism section, 15 ... Distributor, 15c ... Beam Split mirror, 17 ... Timing setting device, 21 ... Photoelectric conversion unit, 21a ... Photoelectron conversion surface, 21b ... Electrode unit, 23 ... Proximity multiplier, 24 ... Fiber optic plate, 24a ... Phosphor screen, 31 ... Solid-state image sensor 32 ... Drive circuit 41 ... Photoelectric tube 41a ... Imaging surface 42 ... Optical system for trigger 43 ... Circuit portion, 44 ... timing control circuit, 44 ... control circuit

Claims (17)

An image intensifier that converts weak events into fluorescent images;
A signal converter for converting the fluorescent image output from the image intensifier into an electrical image signal;
An imaging apparatus comprising a relay optical system that projects the fluorescent image on the output surface of the image intensifier on the imaging surface of the signal converter and is telecentric on the output surface side.   The image pickup apparatus according to claim 1, wherein the relay optical system projects the output surface of the image intensifier on the image pickup surface of the signal conversion device at substantially the same magnification.   The relay optical system includes a first lens group and a second lens group in order from the output surface, and an imaging magnification can be corrected by adjusting an interval between the first lens group and the second lens group. The imaging device according to any one of claims 1 and 2. The relay optical system is provided to face the output surface of the image intensifier and separates the fluorescent image output from the image intensifier into a first fluorescent image and a second fluorescent image. A distributor for guiding the first fluorescent image to an optical path toward the signal converter,
4. The apparatus according to claim 1, further comprising a timing setting device that defines an imaging timing for operating the signal converter from the second fluorescent image separated by the distributor. 5. Imaging device.   The imaging apparatus according to claim 4, wherein the timing setting device includes a photomultiplier that individually detects the second fluorescent image from the divided region that constitutes the output surface of the image multiplier.   The timing setting device selectively selects a local region of the signal conversion device corresponding to the segmented region of the photomultiplier based on a detection signal corresponding to the segmented region output from the photomultiplier. The imaging apparatus according to claim 5, wherein a driving signal to be operated is output.   The image multiplication device includes a photoelectric conversion unit disposed in an input stage, a proximity type multiplication element disposed in a subsequent stage of the photoelectric conversion unit, and the output surface disposed in a subsequent stage of the proximity type multiplication element. The imaging device according to any one of claims 1 to 6, comprising:   The signal conversion device includes a solid-state image sensor which is one of a CCD image sensor and a CMOS image sensor, and operates the solid-state image sensor based on a timing signal output from the timing setting device. The imaging device according to any one of claims 1 to 7. A relay optical system incorporated in an imaging device having a signal conversion device that converts an image formed on the output surface of the detection device into an electrical image signal,
A relay optical system that projects an image formed on the output surface of the detection device onto the imaging surface of the signal conversion device at substantially the same magnification and is telecentric on the target image side.   The relay optical system according to claim 9, wherein the detection device is an image intensifier that converts a weak event into a fluorescent image on the output surface.   The fluorescent image provided opposite to the output surface of the image intensifier and output from the image intensifier is separated into a first fluorescent image and a second fluorescent image, and the first fluorescent image A distributor for guiding the second fluorescent image to an optical path toward a timing setting device that defines an imaging timing for operating the signal conversion device, and guiding the second fluorescent image to the optical path toward the signal conversion device. Relay optics.   The spot characteristic on the imaging surface of the signal conversion device is adjusted according to the spectral luminance distribution characteristic of the phosphor constituting the output surface of the image intensifier. The relay optical system described.   The first lens group and the second lens group are provided in order from the output surface, and the imaging magnification can be corrected by adjusting the distance between the first lens group and the second lens group. The relay optical system according to claim 12. When the numerical aperture of the first lens group is NA1 and the numerical aperture of the second lens group is NA2, the following conditional expression (1)
1.15 ≦ NA2 / NA1 ≦ 1.8 (1)
The relay optical system according to claim 13, wherein: When the focal length of the first lens group is f1, and the focal length of the second lens group is f2, the following conditional expression (2)
0.5 ≦ f2 / f1 ≦ 2.0 (2)
The relay optical system according to claim 13, wherein:   The relay optical system according to any one of claims 13 to 15, wherein the imaging magnification is adjusted in a range of ± 1.5% while substantially maintaining imaging characteristics. An illumination unit that outputs laser light;
An illumination driving unit for operating the illumination unit;
The imaging device according to any one of claims 1 to 8,
A measurement system comprising: an imaging drive unit that operates the imaging device in synchronization with the illumination unit.

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