RU2302624C2 - Portable device for control and measuring alternate-reflecting ability of light-returning articles - Google Patents

Abstract

FIELD: the invention refers to optical measuring technique.

SUBSTANCE: the portable device for measuring of power of alternate-reflecting light designed for control of quality of light-reflecting articles has a source of light in a light-proof body for lighting of light-returning sample, an arrangement for stationing the sample under a given angle of lighting, a photo receiver for receiving alternate-reflective radiation and a half-transmitting mirror providing coordination of spatially dispersed channels of radiation and photo-receiving with the channel of lighting-reflective sample. The input opening of the photo receiver is fulfilled on a removable light-tight screen and its zones of light transmission are displaced from the axle of the photo receiver on a distance proportional to the required angle of divergence. At that a collecting lens is located between the screen and a light-sensitive element of the photo receiver.

EFFECT: increases accuracy of measuring.

3 cl, 6 dwg

Description

The invention relates to the field of optical-mechanical and electronic instrumentation and can be used in devices for measuring and monitoring the retroreflective ability of road information signs and automobile retroreflectors.

State of the art

A known installation of RETRO 1000 (and RETRO 2000, see [1], p. 15, implemented in accordance with the scheme [2], p. 7, Fig. 3) for measuring the retroreflectivity (in other terminology, "retroreflective" ability, or "coefficient of retroreflectivity" R, proportional to the ratio of the strength I of light reflected back by the "retroreflector" in a given direction (close to the direction of illumination) to the value E of its illumination: R ~ I / E) of retroreflective materials and products at given angles of divergence and lighting β (another common name for the angle of divergence " “observation goal”, α is the angle between the direction of the return-reflected (or “returned”) ray and the direction strictly opposite to the incident ray, the normalized viewing angles are very small, but, as a rule, are not equal to zero, since even when observed from the side the light source, the photodetector (eye of the observer - the driver of the car) and the source (headlight of the car) do not coincide in position. Typical regulatory requirements (see GOST R 50577-93, Appendix D) apply to the divergence angles ("observations") of 0 ° 12 ', 0 ° 20', 1 ° 30 '. The angle of illumination β characterizes the orientation of the retroreflective surface relative to the direction of illumination: β is the acute angle between the incident beam and the normal to this surface. The retroreflectivity coefficient as a function of the mentioned angles R (α, β) for good retroreflectors very quickly decreases with increasing α from 0 to 2 ° and slowly with increasing β, providing the visibility of retroreflective information signs in the reflected rays up to illumination angles β of the order of 45 ° or more), consisting of 1) a light source that generates radiation directed (to the test sample of the product), 2) devices (for example, a goniometer) for basing the test sample at a given angle of illumination β, located at a large (10 m or more) distance of L (base photometry) from the source, and 3) return radiation photodetector disposed in the same plane with the source (normal to the radiation direction) from the small mutable r«L distance from the source. In terms of the following descriptions of the prototype and the claimed device in this analog device, the optical "radiation channels" and "photodetectors" are practically combined with the "main illumination-reflection channel" of the sample, the axis of which passes through the geometric center of the frame (diaphragm) of the sample, restricting the incident on it luminous flux of the source (the presence of other light sources in the room is unacceptable). The specified small (about 0.3 °) angle of divergence α is provided by a certain offset value (by r) of the center of the photodetector inlet from the axis of the main channel: a≈r / L. Such an installation requires a large room, protected from external light, while the sensitivity of the photodetector is small.

A known portable device circuit (see [3], p. 4, Fig. 3) for monitoring retroreflectors, in which to increase the photo signal at a given angle of divergence k, an annular photocell of average radius r≈α · L, covering the axis of the common radiation channel, is used, lighting-reflection and photodetector (passing through the central hole in the photocell), and the source is located behind the photocell. There is a collecting lens at the output of the device, which ensures a constant illumination angle β over the sample area with a shortened base distance L. The disadvantage is the constant angle of divergence α (for changing it, a complex photocell must be replaced), and it’s technologically difficult to ensure α, less than 1 ° (the absence of isolation of the radiation channels and photodetector does not allow realizing sufficiently small values of r).

Known used as a prototype short-base (therefore, suitable for the development of a portable device) Novikov scheme (see [3], p.5, Fig.7), also including a light source, a device based on the sample and a photodetector, and, in addition, a beam splitter a device (beam splitter) providing spatial isolation of the radiation and photodetector channels and their optical matching with the main illumination-reflection channel of the test sample. The device is protected (from external exposure) by a general opaque housing. The optical radiation and photodetector channels intersect at a right angle, and a translucent mirror is used as a beam splitter, and the distance from the center of the mirror to the source and the photodetector is the same value L ₀ , which, together with the distance L ₁ between the mirror and the test sample, forms photometric base L = L ₀ + L ₁ . The scheme provides a measurement of the retroreflective ability at an angle of divergence α≈0, but it does not provide for the possibility of measurements at more important (from the point of view of informativeness of the retroreflective products) values of the angle α - small but not equal to 0, and there is no possibility to control the angle α.

Improvement Background

The purpose of the invention: to increase the measurement accuracy of the retroreflective ability of retroreflective products with portable (short-base, protected from external light) models of the device by more accurate selection (separation from the total reflected stream) of the rays of the return-reflected at a given angle divergence and increase the level of functionality (expanding the range of parameters functioning) by ensuring the reconfiguration of the device at different angles of divergence.

SUMMARY OF THE INVENTION

The goal is achieved in a device for measuring and monitoring the retroreflective ability of samples of retroreflective products and materials, having a common light-tight housing and containing 1) a radiation channel including a light source, 2) a light-reflection channel ("main channel"), including a test-based device product sample, 3) a photodetector channel including a photodetector, and 4) a beam splitter (“beam splitter”), for example, in the form of a translucent mirror, which is placed at the intersection of the axes of the said channels, the same distance from the outlet of the source and the inlet of the photodetector and provides spatial isolation (spatial separation) of the radiation and photodetectors and their optical matching with the main channel of illumination-reflection (so that the axis of one - any of the radiation and photodetectors is a geometric continuation of the main channel, and the axis of the other coincides with the mirror image of the first), characterized in that the inlet of the photodetector is made in the form of light-transmitting zones on an integral - removable or movable - opaque screen, while between the screen and the photosensitive element of the photodetector (small-sized photocell or photomultiplier), a short-focusing collecting lens is placed coaxially with this element, and the light-transmitting zones are displaced from the axis of the photodetector by a distance proportional to the required angle of divergence (while the total the axis of the lens and the photocell and the axis of the photodetector may or may not coincide).

The inlet of the photodetector can be made in the form of an arc, in particular circular, slot, the center of curvature of which lies on the axis of the photodetector (which, as an additional effect, can significantly increase the sensitivity of measurements by increasing the area of the receiving hole).

The device is equipped with an additional control channel, the axis of which spatially coincides with the position of the mirror image of the axis of the main channel (illumination-reflection channel), while an additional observation hole is made on the axis of the control channel in the device case.

List of drawings

The invention is illustrated by drawings. Figure 1 shows a variant of the optical circuit of the device as a whole. In Fig.2, 3 - options for the diaphragm of the light source and the diaphragm screen of the photodetector, respectively, and in Fig.4 - a combination of their images. Figures 5, 6 show variants of the diaphragm screen of the photodetector (with the superimposition of the image of the source label), providing high sensitivity to weak return reflection due to the integration of signals in different information-significant directions of retroreflection. In FIGS. 4, 5, 6, the designations of positions indicating not real elements but their images created by a translucent mirror are underlined, for example, while the photodetector inlet has the designation “15”, its image is “ 15 ”.

Information confirming the possibility of carrying out the invention and the operation of the device

The device (Fig. 1) contains in the general opaque housing 1 the following blocks and elements: light source block 2 with a conditional point O _and in the plane of its outlet; a basing device, which is used as the plane of the main light hole 3 in the housing 1 with a conditional center O, covered with a protective glass or lens 4, and adjacent (in the working state of the device) to the test reflective sample 5; a photodetector unit 6 with a conditional point O _f in the plane of its inlet. In the center of the _Ос system - for the spatial isolation of the radiation channel О _и -О _Ц and the photodetector channel О _Ц -О _ф and their optical matching with the main illumination-reflection channel О _Ц -О - a beam splitting device 7 is placed in the form of a translucent mirror 8 or glued beam splitting prism (In the case of manufacturing a beam splitter 7 in the form of a prism, one should take into account some kink (not shown in Fig. 1), which the main and control axes of the device will undergo on the refracting faces of the prism, since these faces must be deviated from the normal (to the axial rays) position, providing reflection of the inevitable parasitic (Fresnel) glare on the light-absorbing body of the device (ie, away from the photodetector)!), containing a flat translucent inner face-mirror 8. Optimum reflector reflector - 50% .

In addition to the main hole 3, in the housing 1, an auxiliary hole 9 with a center О 'can be made, which, when setting up and adjusting the device, is supplemented (externally) by an observing device 10 (magnifying glass or telescope), and in the operating mode it can be blocked (from the inside) by an additional photocell 11, and forms with the center O _C system control channel O _C -O '. The photodetector 6 and the comparison photocell 11 are connected to a common electronic unit with a display used for taking readings (not shown in FIG. 1).

Normal to the plane of the main hole 3 — the basal plane of sample 5 forms an angle β with the axis O- _Oc equal to the required angle of illumination of sample 5. If necessary, to ensure a constant angle of illumination β over the entire area of the sample, hole 3 must be covered by a collecting lens 4 with a focal length, equal to L or (if we allow some variation in the angle of illumination with respect to β) by large L.

The axes O _c -O and O _c -O 'of the main and control channels are correlated as mirror images of each other created by mirror 8 (the plane of the mirror intersects the plane of the angle between the axes along the bisector) and form an angle 2φ between themselves, where φ is the angle from ≈ 15 to ≈75 ° (depending on the device layout) between the reference axis and the plane mirror 8. axles O _n -O _{and n} and O _p -O radiation channels and are photoreception geometrical continuation of the axes O-O and O _'p O _q , wherein if G _{n and} -O (O _i -O or _f) is a continuation of the major axis O-O _n, then G _p -O _{f (n} or O _and -O) - cont of the reference axis O'-O _n. The distance from the center of O _C to the point O _{and the} outlet of the source 2 and to the point O _{f of the} screen of the inlet of the photodetector 6 is equal to the same value L ₀ , which, together with the distance L ₁ between the mirror and the test sample 5 forms the base of the photometry L = L ₀ + L ₁ . Thus, the point O _f coincides with the image of the point O _and in the mirror 8. As a result, the point O _f determines the path to the photodetector 6 of the beam emitted by the point O _and source 2 and experienced perfect retroreflection on the sample 5, that is, the beam reflected back under angle of divergence α = 0.

The source unit 2 includes either a diaphragm with an outlet 12 of a predetermined, often round, shape of diameter d _and ; the center of the hole (figure 2) is on the axis O _c -O _and . The diaphragm is illuminated by an incandescent lamp or other source with a compact luminous body 13. Illumination is either direct (then the luminous body should be larger than the aperture 12 of the diaphragm) or through a lens 14 creating an image (enlarged approximately a / b times, where a and b are the distances from lenses to the luminous body and the diaphragm, respectively) of the body 13 near the diaphragm, covering its outlet 12. But the “outlet" of the source can be the luminous body itself or its image, if it is compact ("point"). The diaphragm in this case is absent or replaced, in order to reduce spurious illumination, by a light-shielding screen with a hole 12 larger than the body 13 (or its image).

The inlet 15 of the photodetector 6 - round diameter d _f (Fig.3) or more complex shape (Fig.4, 5) - is made on an opaque screen 16 that intersects the axis of the photodetector at the point O _f , and its light transmitting zones are separated from the point O _f by a given value r = α · L (where α is in radians). This is the displacement of the light hole 15 from the axis О _ф -О _ц , which determines the dimensions of the screen 16, which can be significantly larger than the dimensions of the photosensitive part of the receiver - photocell 17. Therefore, a short-focusing collecting lens 18 is placed directly behind the screen, and only then, near the image plane of the main hole 3 the device created by the lens 18 is the photosensitive element itself 17. The size of the photocell 17 is consistent with the image size of the hole 3 (coinciding with the size of the luminous zone of the sample 5): it should fit on the photosensitivity itelnoy photocell area and can be many times (i.e., in the L / f, where f - focal length of lens 18) is less than the opening 3 of the device. The dimensions (diameter) of the lens 18 (and the screen 16) are consistent with the maximum value of the angle d (with the central position of the point О _{f, the} diameter of the lens is not less than 2α · L + d _f ).

The position (relative to the axis О _ф -О _ц ), the shape and size of the inlet light-transmitting hole 15 in the screen 16 determine the divergence angle α, as well as the position of the observation plane (angle plane α) relative to the illumination plane (angle plane β) and the balance between the accuracy of the job angle α and sensitivity of the device. By appropriate selection of the position and shape of the light hole 15 (for which the screen can be interchangeable), it is possible to measure the retroreflectivity of sample 5 at different values of the angle α and in different planes of the angle α (relative to the plane of the angle of illumination β), as well as the integral characteristics (total return reflection in directions corresponding to practically the most informationally significant values of α).

For example, if the inlet of the photodetector has the shape of an arc or even an annular slot of radius r and width h≤r / 3 (Fig. 5), and the outlet of the source 12 (Fig. 2) is round, of diameter d _and ~ h, and if the location of these elements with respect to the mirror 8 ensures the alignment of the hole 12 and the image (in the mirror) of the arc (ring) hole 15 (this can be checked when observing through the hole 9), the signal from the sample 5 will be integrated during measurements in all reflection planes at values α = r / L ± h / L, which significantly lichivaet return reflection sensitivity measurements for a given angle of divergence by increasing the area of the receiving opening.

Figure 6 shows another variant of the light transmitting zone 15, which is elongated in the radial direction from r1 to r2. Here, γ is the angle between the illumination plane b-b '(sample 5) and the photometry plane of the reflected rays (i.e., between the planes of angles β and α). In this case, the device measures some integral (in α value) characteristic of the test sample 5, simulating the most typical situation in the practice of using retroreflective materials on highways (the driver of a moving car observes a retroreflective information sign in the light of his own headlights. The observation angle α changes (decreases) from r2 / L to r1 / L; the angle γ approximately characterizes the observation plane).

On the front (facing the center O _C ) side of the diaphragm of the source 2, a marking (crosshair) can be seen (using an observing device 10), indicating the position of the point O _and facilitating the alignment of the optical system of the device. The same applies to the diaphragm-screen 16 of the photodetector 6, its reference point O _f is applied most often (in particular, according to FIGS. 1, 5, 6) in the center of the screen 16 - on the axis of the photocell 17 and lens 18, but can be on the side from this axis (cf. FIGS. 3, 4, where the axis of the photodetector O _c -O _f does not coincide with the axis of the block of elements 17 and 18 of the device), which allows reducing the dimensions of the screen 16 (and the diameter of the lens 18) for a given angle α.

The instrument is tuned for use for measurements at a given value of the divergence angle α by using the control channel O'-O _c as follows. The observation hole 9 is opened (and a comparison photocell 11 is removed, covering the hole, if any) and the main hole 3 (a retroreflective sample is not required). Through the opening 3 in any extraneous light source (own source 2 is turned off) highlights the internal device components, and (via supervisory device 10) is controlled by the combination of control points of images O _and and D _f on the diaphragms source 2 and the photodetector 6, more precisely the combination of one of the points O _and and O _f with the image (created by the mirror 8) of another (Fig.4-6). In the absence of alignment, it must be achieved either by the necessary lateral displacement of one of blocks 2 and 6, or by smoothly changing the tilt of mirror 8 (at least one of these three variants of adjusted displacements (the least number of undesirable side effects, from the point of view of possible influence on the conditions illumination of sample 5, one should expect from the displacements of block 6) it is desirable to provide for the design of the device in advance).

In operation, the opening 9 has to be closed (against the ingress of ambient light), comparing the photocell 11 installed in the control channel O'-O _n, the main opening 3 is provided in contact with the test sample retroreflective 5, the source 2 is included. The light of the source 2, breaking through the beam splitting device 7, is divided into two beams, one of which is absorbed by the photocell 11, the other - at an angle of illumination β falls on the sample 5, experiences a reflection and, again breaking the beam splitter 7, is partially lost (“returning” to the source 2), partially falls on the photodetector 6. The rays “returned” by the sample 5 at the divergence angle α, to which the device is tuned, pass through the light-transmitting zones 15 of the screen 16, are sent by the collecting lens 18 to the photocell 7, create a photocurrent and form an electron nny signal which is converted into the display information on the retroreflective ability of the sample 5. The signal from the photocell 11 comparison proportional brightness source 2 introduces a correction to the final measurement result, which depends on the possible instability of the brightness.

The effectiveness of the invention consists in increasing the level of functionality and increasing the accuracy of measurements of the retroreflective ability (retroreflectivity) of portable (short-base, portable) instrument circuits, which is ensured by the possibility of easily reconfiguring the device to different divergence angles due to the use of a movable in the transverse direction or (interchangeable) diaphragm screen of the photodetector with a light hole offset from its center and eliminating the uncertainty of the divergence angle due to using the control channel. An additional effect is to increase the sensitivity of measurements by increasing the area of the receiving hole (for example, in the form of a ring), which integrates signals that are reflected back in different directions. A possible base for photometric measurement L (it also determines the main dimensions of the device), in which it is most advisable to use the inventive scheme in portable and portable devices from 0.3 m to 0.7 m. But it is also possible to use the scheme in short-base stationary installations up to 2-3 m while the allowable angles of divergence α are limited by the reasonable (up to 10 cm) dimensions of the lens 18.

Information sources

1. Flyer "LMT Photometers Colorimeters", 1998, Productinformation, p.15.

2. International Standard ISO 6742/2. Cycles - Lighting and retro-reflective devices - Photometric and physical requirements - Part 2: Retro-reflective devices, 1985, p. 7, fig. 3.

3. Abstract sb. "Autotractor electrical equipment", issue 2, 1967, p.1-6.

Claims (3)

1. A portable device for monitoring and measuring the retroreflective ability of retroreflective products, having a common light-tight housing and containing a radiation channel including a light source, a light-reflection channel ("main channel"), including a device for basing a test sample of a product, a photodetector channel including a photodetector and a beam splitter (“beam splitter”), which lies at the intersection of the axes of the said channels, at the same distance from the source outlet and the inlet detector and provides spatial isolation of the radiation and photodetector channels and their optical matching with the main channel, characterized in that, in order to increase the level of functionality, the photodetector inlet is made in the form of light-transmitting zones on a separate opaque screen, while the interface between the screen and the photosensitive element of the photodetector is coaxial a short-focusing collecting lens is placed with this element, and the light-transmitting zones are offset from the photodetector axis by a distance proportional to the required angle p ascent. 2. The device according to claim 1, characterized in that, in order to increase sensitivity, the inlet of the photodetector is made in the form of an arc slot, the center of curvature of which lies on the axis of the photodetector channel. 3. The device according to claim 1 or 2, characterized in that, in order to increase the accuracy of measurements, it is equipped with an additional control channel, the axis of which coincides with the image of the axis of the main channel in the mirror of the beam splitter, while in the case of the device on the axis of the control channel made an observation hole.

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