Hand held laser bar code reader with safety shutoff responsive to housing motion detector

A hand held laser bar code reader includes a motion sensor and associated circuitry to disable energization of the laser unless the bar code reader has just undergone some degree of motion. This safety feature avoids the possibility of the bar code reader's being held motionless for a long enough time to cause retinal damage to a human eye.

BACKGROUND OF THE INVENTION 
The invention relates to a hand-held laser bar code reader, or scanner, and 
to the meeting of safety requirements in regard to such laser devices. 
Scanners for reading bar codes have been increasingly used for commercial 
and industrial purposes. In addition to the well-known use in supermarkets 
for reading the labels on goods they are also used in warehouses for 
inventory and identification of goods. However, in warehouse usage there 
is often a considerable distance to the goods. For this purpose there is 
in general a need for hand-held scanners that can read over a long 
distance for making the work of the user more efficient and to avoid the 
need for climbing up to goods stored in high places. 
At the same time, such scanners must satisfy safety requirements, such as 
those promulgated by regulations such as 21 CFR .sctn.1040 in the United 
States and I.E.C. Pub. 825, of the International Electrotechnical 
Commission. These requirements specify that a laser scanner (depending on 
use) must be of sufficiently low power that its beam will not injure the 
human eye if aimed directly into the eye for a prescribed period of time 
(often 1000 seconds, or about 16 minutes.) 
It is an object of the present invention to produce a relatively high 
powered hand-held laser bar code reader, suitable for efficient use in 
warehouses and like places, which includes a safety device to prevent the 
possibility of beam exposure to the human eye for dangerous periods. 
SUMMARY OF THE INVENTION 
This is accomplished in accordance with the invention by including a motion 
sensor in the hand-held scanner. The small motion sensor can be integrated 
in the body of the hand-held reader or it can be fixed on the outside of 
the device. 
The motion sensor and associated components and circuitry embody the safety 
feature of the hand-held scanner, and are effective to shut off or disable 
the scanner automatically if the scanner remains stationary for a 
preselected period of time. To be activated, the scanner has to have just 
moved or be in the process of at least minute movement. The time period 
during which the scanner can be stationary and still energized will vary 
with application. It can be adapted to different beam powers of the 
scanner, or different beam powers for different scanners. The higher the 
scanner power, the sooner the motion sensor will disable the laser in a 
stationary period. Since a relatively long period of exposure is required 
to cause eye damage, the stationary time period can be set at five 
seconds, ten seconds or fifteen seconds, for example, still representing a 
conservative safety factor. 
Motion sensor devices and circuitry of the general type suitable for use in 
the present invention have previously been used in some household 
flatirons. The object there was to prevent the danger of fire or other 
damage to surrounding objects or to the flatiron itself, due to the 
flatiron's being left on and unattended for prolonged periods. In the 
present invention the object is different. It is based on a shorter period 
of time, and directed to making it impossible to cause eye damage with a 
hand-held laser scanner, due to the inherent nature of the human body and 
hand to be in motion to at least some minute degree. 
The scanner can only cause eye damage if the beam is directed against the 
retina (or the scanning beam scanned repeatedly back and forth across the 
eye, intermittently striking the retina) for a considerable period of 
time. In practical effect, this requires that both the eye and the scanner 
device be motionless for that prolonged period of time. For the scanner 
and the person's eye to be both in motion but synchronous motion with the 
beam continually fixed on the eye is a practical impossibility. 
Therefore, it is a primary object of the invention to prevent the 
possibility of eye damage from a hand-held laser bar code reader by 
limiting possible eye exposure, therefore enabling the laser beam to be 
more powerful in accordance with need. 
Other and further objects of the present invention will be apparent from 
the following description and claims and are illustrated in the 
accompanying drawings which, by way of illustration, show preferred 
embodiments of the present invention and the principles thereof and what 
are now considered to be the best modes contemplated for applying these 
principles. Other embodiments of the invention embodying the same or 
equivalent principles may be used and structural changes may be made as 
desired by those skilled in the art without departing from the present 
invention and the purview of the appended claims.

DESCRIPTION OF A PREFERRED EMBODIMENT 
In the drawings, FIG. 1 shows a conventional hand-held laser scanner 10 of 
the type generally used as a non-contacting reader of bar codes. The bar 
code reader 10 is shown scanning a laser beam 12 (dashed lines) in a 
reciprocating projected pattern to form a scan line 14 on an object 
surface 16. 
The scanner 10 is shown projecting the scan line 14 across a bar code 18 on 
the surface 16. The bar code 18 may be of conventional format comprising 
alternate reflecting and nonreflecting lines of differing widths. The 
laser scan line 14 is shown crossing the bars of the bar code 
transversely. Although a single scan line 14 is shown formed by the laser 
scanner 10, it should be understood that the scanner 10 can be of the type 
which projects a raster pattern or other suitable pattern comprising more 
than one scan line. 
The scanner 10 may comprise a gun-shaped housing 20 of conventional 
configuration, including a handle portion 22 and a spring-loaded trigger 
switch 24. 
As indicated in FIGS. 1 and 2, a motion sensor 26 is included in the laser 
scanner ssembly, and may be positioned inside the housing. For example, it 
may be located in the base of the handle portion as indicated, or any 
suitable location where adequate space can be found without significantly 
affecting the overall dimensions of the scanner device 10. 
FIG. 3 shows schematically an example of a circuit 30 which may be employed 
in the invention. In the embodiment shown, the trigger spring switch 24 
leads to a control 32 which is connected to a power supply 34. The control 
32 controls a scan drive 36 and a laser drive 38, as well as signal 
processing circuitry and indicator lights typically present on a bar code 
scanner. 
The motion sense circuitry 40 is connected to the laser drive 38 through an 
AND gate 42 which also receives a signal from the main device control 32 
as indicated in FIG. 3. The motion sense circuitry 40 is connected to the 
motion sensor switch 26 (shown in FIGS. 1 and 2), so that the laser drive 
38 will be disabled unless the AND gate 42 receives both a command to scan 
from the control 32 and an okay to scan from the motion sense circuitry 
40. 
In this way, the laser drive 38 is powered only when the scanner housing 20 
(FIG. 1) has just moved, i.e. has moved within a predetermined time 
period. Two conditions are required, the operator actuated switch 24 must 
be depressed by the operator, and the motion sensor 26 and associated 
motion sense circuitry 40 must confirm that the bar code reader device has 
just been in motion. 
The motion detector may comprise a mercury switch which either sends a 
steady signal (i.e. steadily closed or open circuit) or an erratic signal, 
signifying motion. These are appropriately interpreted and processed by 
the motion sense circuitry 40. In one preferred embodiment the motion 
sensor may be one marketed by Signal Systems International of Holmdel, 
N.J., under the designation JS101. 
Within the motion sense circuitry 40 there is included some form of timer. 
Thus, if the motion detector indicates that there has been no motion of 
the housing 20 of the scanner for a predetermined period of time, as 
determined by the timer, the sense circuitry interprets this as the bar 
code reader being stationary for the preselected period, and it will send 
a "not okay" signal to the AND gate 42 to disable the laser drive 38, 
regardless of whether the trigger spring switch 24 is depressed or not. 
The motion sense function can be accomplished, for example, in 
combinational logic, a microprocessor, or analog timer techniques well 
known to those skilled in the art. 
Also, the laser device 10 can include two or more motion detectors 26, at 
different orientations in the housing 20, to assure sensitivity to motion 
in different directions or on different axes and over a broad range of 
motion frequencies. FIG. 3 shows two motion detectors 26 and 26a, both 
connected to the motion sense circuitry 40. The different detectors can 
have different preselected time periods established by the motion sense 
circuitry 40, in the event that different types of motion are of greater 
concern than others for the safety of the device. It may be desirable to 
give different weighting to different axes or directions of motion, or to 
different frequencies of motion. 
It should be understood that other suitable motion detectors, circuitry and 
logic can be employed while still embodying the principles of the present 
invention. 
While I have illustrated and described the preferred embodiments of my 
invention, it is to be understood that these are capable of variation and 
modification, and I therefore do not wish to be limited to the precise 
details set forth, but desire to avail myself of such changes and 
alterations as fall within the purview of the following claims.