GB2291967A - Optical scanning position checking system - Google Patents

Abstract

An optical scanning position checking system for laboratory automation equipment which is allegedly useful to confirm whether a syringe needle is straight or bent. A laser diode (3) and optical system is used to create a scanned laser x-y target area (2), and then the robot system can place a reference vane or syringe needle into the target area. The exact position of the syringe in the target area may be determined by detecting the positions of the shadows cast by the syringe on photodiodes (16, 17), using electronic counting means (Fig. 2, not shown). The optical system consists of a refractor (5) rotated by a motor (6) at a known speed, a beam splitter (8), mirrors (9, 10, 12) and ball lenses (14, 15), and serves to provide two orthogonal scanning laser beams which interact at the target area (2). <IMAGE>

Description

TITLE OF THE INVENTION OPTICAL SCANNING POSITION CHECKING SYSTEM FOR LABORATORY AUTOMATION EQUIPMENT .BACKGROUND OF THE INVENTION Single and multiple axis optical detection systems are known, see U.S. 5,166,889 at Figure 4C and col. 7, line 65 to col. 8, line 4; and U.S. 4,495,149. The latter patent is most pertinent, and discloses an optics/dispensing mechanism, see col. 5, lines 18 to col. 7, line 6, see also Figures 1, 3, 5, 6, 8 and 9. Target irradiation is employed using four directions, see col. 6, lines 35 and 36.

This system uses light guiding glass fibers 32 to direct the irradiation through the radiation lenses to a target. This optical detection is used to detect the position of the dispensing needle to facilitate its movement, but does not suggest the concept of detecting bent needles.

5,171,530 addresses the problem of bent or broken syringe needles but does not disclose any means for sensing these defects. The sensor disclosed in the Pennatto patent detects the presence or absence of a sample vial to be used in conjunction with the dispensing needle.

Finally, U.S. 4,325,909 discloses a vertically and horizontally moveable arm structure for fluid transfer. Sensors are employed in this structure for vertical positioning of the arm.

However, there is no system to monitor the needle straightness.

SUMMARY OF THE INVENTION An object of the present invention is to monitor the straightness of a syringe needle and utilizes diode laser in conjunction with mirrors, lenses, detectors, a refractor and a beam splitter.

It is another object of the present invention to provide a means for determining if the position of a syringe needle or other object carried by a robotic or positioning system falls within a target zone which does not involve contacting the needle or object.

A further object of the present invention is to provide a means and method to accurately measure the exact position of the syringe needle or object carried by a robotic or positioning system within a target zone.

A further object of the present invention is to provide an apparatus which measures the width of the object which falls within a target zone.

A still further object of the present invention is to provide an electronic output means that may be directly connected to a indicator lamp or directed to lab automation equipment which will signal when an object is properly positioned within a target zone.

According to this invention, there is provided a means for optically scanning a collimated light source creating a 2 or 3 axis target zone for indicating if an object is positioned in the target zone and the exact location of the object inside the target zone.

These and other objects and features of the present invention will be apparent from the following detailed description taken with reference to the accompanying drawing.

The present invention will be described with reference to the annexed drawing which are given by way of non-limiting examples only in which: BRIEF DESCRIPTION OF DRAWING Figure 1 is a schematic diagram illustrating the optical system associated with the needle check apparatus according to an embodiment of the present invention.

Figure 2 is a schematic diagram illustrating the electronic system associated the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the Figure 1, there is shown a housing 1 which holds the optical components of the system. The apparatus generates a target area 2 using two scanned laser beams positioned at right angles to one another. Diode laser 3 generates a collimated light beam 4. A collimated light beam may also be generated using other types of lasers (i.e., gas laser; He Ne laser). The laser light beam passes through a refractor 5 which refracts the light beam causing it to exit the refractor 5 at a different plane depending on the angle of incident.Refraction is a .function of the index of refraction of the material and the angle of the incidence light beam according to the equation: sin A2 = (sin Al)/n21 where: Al = incidence angle A2 = refraction angle n21 = index of refraction of medium 2 with respect to medium 1 A cube of polished plastic or a glass cube may serve as good refractors. Connected to the refractor cube 5 is the shaft of a motor 6. The motor 6 causes the refractor cube 5 to rotate at known fixed RPM. As the refractor 5 rotates the angle of incidence of the entering collimated light beam 4 changes and in turn the light beam exits the refractor 5 at a different plains. The result is a scanned laser beam 3 exits the rotating refractor 5.The scan rate a function of the motor 6 RPM and the width of the scan a function of the size of the refractor 5 and the material the refractor is made of.

The scanned laser beam 7 then enters into beam splitter 8.

The beam splitter is oriented in a manor that 50% of the light exits at a right angle towards mirror 9 and the remaining 50% of the light travels straight through the beam splitter towards mirror 10. Scanned laser light reflects off of mirror 9 through aperture plate 11. The remaining light exiting beam splitter 8 reflects off mirror 10 and mirror 12 to aperture plate 13. Aperture plates 11 and 13 are adjusted to reduce the scan width of the scanned laser. The width of the aperture opening is set to a value which provides an acceptable target zone 2. Light exiting the aperture plates 11, 13 intersect at right angles in the target zone 2 and continue to ball lenses 14,15. The target zone 2 now consists of two scanned laser beams which intersect at right angles forming a square target zone proportional to the adjustment of the aperture plates 11, 13.

Ball lenses 14, 15 focus the scanned laser light into a spot at the focal point of the ball lens. A photo diode detector 16, 17 is located at the focal point of the ball lenses 14, 15. The size of the photo diode detector is large enough to accommodate the focused spot created by the ball lenses 14, 15.

If an object, such as a syringe needle, is placed into the target zone 2, the scanned laser beam will cast a shadow of the needle onto the ball lens 14, 15. Knowing the sweep rate and the start time of the sweep, it is possible to know not only that the needle is in the target zone but also where it is in the target zone. The width of the shadow generated by an object in the target zone is proportion to the width of the object.

Figure 2 shows an electronic circuit which generates an electrical signal if an object is placed in the apparatus inside the target zone 2. Scanned light exiting from the ball lenses 14, 15 is focused onto photodiodes 16, 17. Amplifier 18, 19 converts the light signal into an electrical signal. The electrical output from amplifier 18, 19 enters into the input of comparator 20, 21. The comparator trigger point is adjusted to a suitable threshold above the noise floor by voltage divider 22, 23 which in turn provides a 'IvI'L output when scanned light is detected. The TTL output from the comparator is directed into the input of counter 24, 25. The counter is configured to provide a divide by 4 output. The counter responds to positive transitions on the counter's input. The output frequency from the counter will be proportional to the number of positive transitions on the input of the counter. The result is a Tit output 1/4 the scan frequency if no target is in the target zone and a TIt output of 1/2 the scan frequency if a target is inside the target zone.

Outputs from the counter 24,25 are directed to a circuit 26 which measures the period of the counter output and determines if the frequency has changed. A variety of circuits could be used to measure frequency changes. Shown in the FIG. 2 a single chip microprocessor is used to measure frequency changes. The microprocessor 26 then generates an output 27 which indicates that an object is in the target zone.

The microprocessor 26 could also be programmed to .measure the time from the start of a scan to the point where the object casts. a shadow on the detector. Knowing the scan rate of the light beam the exact position of the object could then be calculated. In addition, the microprocessor 26 could be programmed to measure the time to traverse the shadow of the object and the width of the object could be calculated.

Although the embodiment describes a two axis needle check apparatus with a square target area, it would also be possible to create a 3-axis check system which has a cube target area. This could be accomplished by adding a second rotating refractor which is at a right angle to the first rotating refractor. The horizontal scanned light beam from the first refractor would enter the second refractor creating an additional vertical scan. A 3-axis scanned system may be useful to determine the exact location of a needle tip.

Claims (1)

1. WHAT IS CLAIMED IS:

   1. An optical scanning position-checking system which comprises an X-Y drive mechanism together with an optical system .which created a scanned laser X-Y target area, means for placing a reference vane or syringe needle into said target area, and means for generating a logic output signal if the predetermined target specifications are met.