Patent Application
20050041125
1. Field of the Invention
The present invention relates to an imaging device for imaging an object using two-dimensional imaging elements. Furthermore, the present invention relates to a particle image capturing apparatus for imaging particles in an optical cell moving at high speed together with the medium.
2. Description of the Related Art
Conventional an imaging devices are known, such as digital cameras and the like, which capture the image of an object using an area sensor (two-dimensional imaging element such as a CCD or the like) to produce image data. U.S. Pat. No. 5,721,433 discloses a particle image analyzer capable of analyzing particle images obtained by sequentially imaging particles of a particle suspension fluid flowing within an optical gel and moving through an imaging region, and displaying a calculated distribution map of the shape parameters such as the degree of roundness and the like so as to analyze the shape and the like of micro particles.
When interlace-type CCD area sensors for sequentially scanning odd pixels (ODD field) and even pixels (EVEN field) are used as the imaging elements of the particle image analyzer of U.S. Pat. No. 5,721,433, a striped pattern is introduced into the image when the area sensor is optically exposed during the EVEN field period. In general, the ODD field period of the area sensor is {fraction (1/60)} of a second, and the EVEN field period is {fraction (1/60)} of a second. Accordingly, when the particle image analyzer uses interlace-type CCD area sensors, it is difficult to image particles moving through the imaging region during the imaging intervals since the imaging interval must be approximately {fraction (1/30)} of a second.
The object of one embodiment of the present invention is to provide an imaging device which improves the probability of imaging each object even when imaging a plurality of objects moving at high speed.
The first aspect of the present invention relates to an imaging device comprising: a first two-dimensional image sensing elements; a second two-dimensional image sensing element; an optical system for forming identical optical images on the first and second image sensing elements; a first shutter means for controlled exposure of the first image sensing element from the optical system; a second shutter means for controlled exposure of the second image sensing element from the optical system; and a control means for driving the first image sensing element based on field signals sequentially repeating ODD field period and EVEN field period, driving the second image sensing element based on field signals having a different phase than the first image sensing element, and controlling the operation of the first shutter means and second shutter means so as to expose with light from the optical system an image sensing element having the ODD field period among the first and second image sensing elements.
The second aspect of the present invention relates to an imaging device comprising: a plurality of two-dimensional image sensing elements; an optical system for forming optical images on the respective image sensing elements; and a drive control means for driving the plurality of image sensing elements with respectively different timings, and controlling the operation of electronic shutters of the respective image sensing elements so as to expose one image sensing element among the plurality of image sensing elements.
The third aspect of the present invention relates to a particle image capturing apparatus for imaging particles comprising: a flow cell for forming a flow of a particle suspension; a light source for irradiating the particle suspension flow with light; a first two-dimensional image sensing elements driven based on field signals sequentially repeating the ODD field period and EVEN field period; a second two-dimensional image sensing element driven based on field signals having a phase different than that of the first two-dimensional image sensing element; an optical system for forming identical optical images of the particle suspension flow on the first and second two-dimensional image sensing elements; a first shutter means for exposing the first two-dimensional image sensing element with light from the optical system when the first two-dimensional image sensing element has an ODD filed period; and a second shutter means for exposing the second two-dimensional image sensing element with light from the optical system when the second two-dimensional image sensing element has an ODD filed period.
The fourth aspect of the present invention relates to a particle image capturing apparatus for imaging particles comprising: a flow cell for forming the flow of a particle suspension fluid; a light source for irradiating the particle suspension fluid; a first two-dimensional image sensing element; a second two-dimensional image sensing element; an optical system for forming identical optical images of particles in the particle suspension flow on the first and second particle image sensing elements; a first shutter means for controlled exposure of the first image sensing element from the optical system; a second shutter means for controlled exposure of the second image sensing element from the optical system; and a drive control means for driving the first image sensing element based on field signals sequentially repeating ODD field period and EVEN field period, driving the second image sensing element based on field signals having a different phase than the first image sensing element, and controlling the operation of the first shutter means and second shutter means so as to expose with light from the optical system an image sensing element having the ODD field period among the first and second image sensing elements.
The fifth aspect of the present invention relates to a particle image capturing apparatus comprising: a first two-dimensional image sensing element; a second two-dimensional image sensing element; an optical system for forming identical optical images of the particle on the first and second image sensing elements; and a drive control means for driving the first and second image sensing elements with different timings, and controlling the operation of electronic shutters of the respective image sensing elements so as to expose one or another of the first or second image sensing elements.
The structure of an embodiment of the imaging device 1 is shown in
The first CCD drive circuit 8 for driving the first CCD 6 is provided with a synchronizing signal generator 8a for generating synchronizing signals such as a vertical synchronizing signal VD and horizontal synchronizing signal HD based on the signal of the standard crystal generator 10, timing generator 8b for receiving the input of the vertical synchronizing signal VD and horizontal synchronizing signal HD output from the synchronizing signal generator 8a and generating various types of timing signals used for the first CCD 6, and a driver 8c for receiving the timing signals output from the timing generator 8b and driving the first CCD 6 by providing a vertical transmission pulse, horizontal transmission pulse, and shutter pulses (electronic shutter starting pulse for the first CCD 6) for discharging accumulated signal loads and starting a new exposure. The signal processing system of the output signals of the first CCD 6 are omitted from the drawing. The second CCD drive circuit 9 for driving the second CCD 7 is similarly provided with a synchronizing signal generator 9a for generating synchronizing signals such as a vertical synchronizing signal VD and horizontal synchronizing signal HD, timing generator 9b, and driver 9c.
The first CCD 6 is driven based on the field signal which has the reverse phase of the second CCD 7. In
Although the first CCD 6 and the second CCD 7 are driven based on field signals having reverse phases in the present embodiment, they also may be driven based on field signals having different phases.
The structure of an embodiment of the particle image capturing apparatus 11 using the imaging device 1 is shown in
The imaging of the particle image in the measuring unit 12 of
The suspension fluid 13 delivered to the charging line 16 is introduced to the flow cell 18 by the operation of the sheath syringe 17, and the particle suspension fluid 13 is extracted a little at a time from the tip of the sample nozzle 18a. At the same time, the sheath fluid is also delivered to the flow cell 18 from the sheath fluid bottle 19 through the sheath fluid chamber 20. As a result, the particle suspension fluid 13 is encapsulated in the sheath fluid, and the suspension fluid is constricted as it flows within the flow cell 18 via flow dynamics, and is discharged to the waste chamber 21.
The suspension flow in the flow cell 18 is periodically irradiated each {fraction (1/60)} second by a pulse of light from the light source (strobe) 22. In this way a still image of a particle is introduced each {fraction (1/60)} second to the optical system 2 of the solid-state imaging device 1. The still image is input to the first CCD 6 and second CCD 7 through the optical system 2. The first CCD 6 is driven by a field signal having the reverse phase of the second CCD 7 as described previously. Therefore, the image of the particle input by the optical system 2 is sensed by the CCD which has the ODD field signal among the first CCD 6 and the second CCD 7.
Although a first CCD drive circuit 8 and a second CCD drive circuit 9 are used as exposure control means in the above embodiment, the exposure timing of the first CCD 6 and second CCD 7 also may be controlled by the control unit 25. Furthermore, although an electronic shutter is used as a shutter means for controlling the exposure of the first CCD 6 and second CCD 7, a mechanical shutter also may be used.
Although the first CCD 6 and second CCD 7 are driven based on field signals having reverse phases, they also may be driven based on field signals having different phases.
The structure of a particle image analyzer 30 provided with the particle image capturing apparatus 11 is shown in
The image processing sequence of particle image data of each {fraction (1/60)} second is shown in
The particle image signals from the first CCD 6 and second CCD 7 are subjected to A/D conversion by the signal processing circuit 36 of the image processing device 31, to obtain particle image data (step S1). First, the obtained image data are subjected to background correction to correct unevenness in the intensity of light (shading) irradiating the suspension fluid flow (step S2).
Specifically, image data obtained by light exposure when particles are not moving through the flow cell 18 are collected prior to the measuring, and these image data and the image data of the actual particle image screen are compared. Then, a contour enhancement process is executed to accurately extract the contour of the particle image (step S3). Specifically, the generally well-known Laplacean enhancement process is executed.
Next, the image data are binarized at an appropriate threshold level (step S4). Then, a determination is made as to whether or not the binarized particle image has an edge point, and information on a possible edge point adjacent to the observed edge point. That is, a chain code, is generated (step S5). Thereafter, the particle image is subjected to edge tracing while referring to the chain code, and the total number of pixels, total number of edges, and number of inclined edges of each particle image are determined (step S6).
If an image processing device capable of high-performance pipeline processing is used, the aforesaid image processing of a screen imaged every {fraction (1/60)} second can be accomplished in real time. Furthermore, the particle image can be extracted from the imaged frame, and the extracted particle image can be stored in the image memory of the memory unit 35 of the image processing device 31 (step S7).
When the imaging ends (step S8), particle characteristics parameters such as circular equivalent diameter (granularity) and roundness and the like are calculated as described below (step S9). First, the projection surface area S and circumferential length L of each particle image are determined from the total number of pixels, total number of edges, and number of inclined edges of each particle image using the equations below.
As shown in
Surface area S=total number of pixels−(total edges×0.5)−1 (1)
Circumferential length L=(total number of edges−number of inclined edges)+(number of inclined edges×21/2) (2)
Then, the circular equivalent diameter is determined using the surface area S and circumferential length L. The circular equivalent diameter is the diameter of a circle having the same surface area as the projection image of the particle, and is expressed by equation (3). The roundness is a value defined by equation (4); the roundness is “1” when the particle image is circular, and the roundness value becomes smaller the larger the irregularities of the exterior edge of the particle image.
Circular equivalent diameter=(particle projection image area/π)½×2 (3)
Roundness=(circumferential length of a circle having a projection surface area value identical to the particle image)/(circumferential length of the particle image) (4)
When the circular equivalent diameter (granularity) and roundness of each particle image is calculated in this way, then a required scattergram and histogram are created based on commands from the keyboard 32 and displayed on the display 33 (step S10).
When analysis items and analysis regions are specified from the keyboard 32, these items and regions of the displayed scattergram and histogram are analyzed, that is, various analysis data, such as average value, standard deviation, variable coefficient, median value, mode value, 10% cumulative value, 50% cumulative value, 90% cumulative value and the like are calculated and the calculation results are displayed (steps S11, S12).
The measuring unit 40 is provided with a first light source unit 41 having a red semiconductor laser light source with a wavelength of 660 nm, conical exterior surface reflective mirror 42, conical interior surface reflective mirror 43, ring mirror 44, conical interior surface reflective mirror 45, optical cell 46, objective lens 49, dichroic mirror 50, lens 51, mirror 52, pinhole plate 53, collimator lens 54, bandpass filter 55, photosensor element (photomultiplier tube) 56, imaging control unit 57, second light source unit 58 having a pulse semiconductor light source with a wavelength of 870 nm, half-mirror 59, focusing lens 60, half-mirror 61, mirror 62, first CCD 63, and second CCD 64.
First, when a laser beam of 600 nm wavelength is emitted from the first light source unit 41, the laser light is converted to zonal light by the conical exterior surface reflective mirror 42 and the conical interior surface reflective mirror 43. The zonal light is guided to the conical interior surface reflective mirror 45 by the ring mirror 44, and converges at the detection region 48 of
The scattered light from the irradiated particle enters the first CCD 63 through the objective lens 49, dichroic mirror 50, half-mirror 59, objective lens 60, and half-mirror 61. The light reflected by the half-mirror 61 enters the second CCD 64 through the mirror 62. This assay unit 40 is capable of high efficiency imaging of particles since it detects and images particles moving in the imaging region. Although the detection region 48 shown in
Furthermore, a zonal irradiating light source unit having the structure shown in
In
The light-emitting sides of the through-holes provided on the same axis as the center axis of the body 71 are provided with three collimator lenses 79a, 79b, and 79c. A concave mirror 78 is provided at the left endface of the body 71 shown in
A multimode optical fiber having a core diameter of 800 □m is used as the multimode optical fiber 72. Furthermore, Pulse semiconductor lasers are used as the laser light sources 76a through 76f.
In the aforesaid structure, the plurality of light fluxes emitted from the laser light sources 76a through 76f are converted parallel light which is parallel to the optical axis of the mirror 78 by the collimator lenses 77a through 77f. The parallel light is condensed by the concave mirror 78 and enters the light receiving end of the multimode optical fiber 72 from different directions at predetermined identical entrance angles. Since the length of the optical paths are mutually identical from the laser light sources 76a through 76f to the multimode optical fiber 72, all of the light flux enters the light receiving opening having the same spot diameter.
The multimode optical fiber 72 mixes the plurality of entering light fluxes and reduces the coherence and smoothes the light intensity distribution and emits the radiant zonal light fluxes from the emission opening to the three collimator lenses 79a, 79b, and 79c. The collimator lenses 79a, 79b, and 79c convert the radiant zonal light fluxes from the optical fiber 72 to parallel light flux having a single optical axis.
From the perspective of good zonal light formation, the plurality of laser light sources are arranged on the circumference centered on the optical axis of the multimode optical fiber 72 such that the spacing of the adjacent laser light sources are equidistant. The number of zonal light forming light sources, that is, the laser light sources emitting light of the zonal light wavelength, is desirably four to eight, and preferably 5 to eight.
According to this structure, coherence can be reduced and zonal light effectiveness improved by the multimode optical fiber using a plurality of laser light sources which emit light flux of a predetermined wavelength. That is, when a particle imaged by zonal light is irradiated, optical resolution is improved since only the light flux entering at an angle to the particle is used. Furthermore, the detection signal to noise ratio is improved by using laser light to reduce coherence.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-297875 | Aug 2003 | JP | national |
